Advances in Petrochemical Engineering and Green Development 9781032331720, 9781032331744, 9781003318569

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ADVANCES IN PETROCHEMICAL ENGINEERING AND GREEN DEVELOPMENT

Advances in Petrochemical Engineering and Green Development is a compilation of selected papers from the 3rd International Conference on Petrochemical Engineering and Green Development (ICPEGD 2022) and focuses on the research of petrochemical engineering. The proceedings features the most cutting-edge research directions and achievements related to geology and green development. Subjects in this proceedings include: • • • • •

Petroleum and Petrochemical Engineering Fossil Technologies Oil & Gas Production Renewable Energy Sources and Technology Green Synergy Innovation Urban Crisis Management

The collection of papers in this proceedings will promote the development of petrochemical industry and energy, resource sharing, flexibility and high efficiency. Thereby, it will promote scientific information interchange between scholars from top universities, research centers and high-tech enterprises working all around the world.

PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON PETROCHEMICAL ENGINEERING AND GREEN DEVELOPMENT (ICPEGD 2022), SHANGHAI, CHINA, 25–27 FEBRUARY 2022

Advances in Petrochemical Engineering and Green Development Edited by

Bin Guan School of Mechanical Engineering, Shanghai Jiao Tong University

CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2023 selection and editorial matter, Bin Guan; individual chapters, the contributors Typeset in Times New Roman by MPS Limited, Chennai, India The right of Bin Guan to be identified as the author of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers nor the author for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. First published 2023 Published by: CRC Press / Taylor & Francis Group 4 Park Square, Milton Park / Abingdon, Oxon OX14 4RN / UK e-mail: [email protected] www.routledge.com – www.taylorandfrancis.com ISBN: 978-1-032-33172-0 (hbk) ISBN: 978-1-032-33174-4 (pbk) ISBN: 978-1-003-31856-9 (ebk) DOI: 10.1201/9781003318569

Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Editor(s), ISBN 978-1-032-33172-0

Table of contents Preface Committee members

xi xiii

Performance analysis of petroleum energy and chemical technology Research on the method of improving the drilling rate of horizontal well reservoirs C. Yan

3

Study on the removal of pollutants by double-cathode electrochemical oxidation Y. Jiang, L. Miao, W. Han, S. Qi & Y. Quan

7

Treatment of electrochemical oxidation and persulfate for organic compounds T. Yan, L. Miao, W. Han, M. Bao & Y. Quan

11

Study on treatment of phenol wastewater by electrochemical process J. Chen, Y. Yang & X. Zeng

16

Study on a kind of alkaline polyacrylamide/Cr gel breaker for oil extraction F. Chen, E.L. Zhao, G.S. Zhao, S.J. Cao & Y.J. Wang

22

Effects of multi-wall carbon nanotubes on seed germination and seedling growth of Water lotus S. Wen, P. Li, Y. Zhao, J. Ran, J. Zhang & M. Xiao

29

Application analysis of geological logging technology in oilfield exploration Y. Huo

34

Classification and safety precautions of blasting technology X. Qian

39

Experimental study on explosion characteristics of lignite dust in coal chemical industry L. Tao & S. Zhu

46

Application of fuzzy evaluation method in mixed combustion of inferior coal in Utility Boiler application in optimization H. Liu

52

Research spot and development status of phase transfer catalysis M.X. Zhang & H. Huang

58

Productivity test analysis of tight sandstone gas wells in Shenfu block, Ordos Basin K. Zhang, Z. Cheng, H. Cheng, M. Wang & Q. Qin

62

Experimental study on water vapor share and waste heat recovery from biomass flue gas C. Miao, N. Liang, K. Fan, H. Wang & J. Wang

69

Coal system reservoir fracturing technology of Carboniferous Benxi Formation in Shenfu block M. Wang, H. Cheng, Z. Cheng, K. Zhang & M. Sun v

77

A new method for judging the drilling mode of downhole instruments based on the giant magnetoresistance effect Y. Wu, H. Yang, Z. Meng, X. Ma, S. Chen & H. Qin

85

Analysis on the feasibility of applying inflow performance regulating device to low permeability horizontal wells Y. Zhou

93

Risk evolution analysis of chemical laboratory poisoning accident based on complex network Y. Chang, M. Zhang, X. Cui, Y. Lu, Z. Yi & C. Liang

98

Phase stability characteristics of marine natural gas hydrates during drilling fluid invasion J. Wang, J. Sun, R. Wang, K. Lv, J. Wang, B. Liao, Q. Wang, Y. Qu & H. Huang

106

Molecular dynamics simulation of solubility parameters of supercritical CO2 and pentaerythritol ester B. Yao & F. Liu

114

Study on thermal design method for impervious graphite heat exchangers B. Ren, H.L. Lu, X.L. Xue, B. Xiao, Y.Q. Yang & J.D. Wang

120

Comparative analysis on measurement uncertainty of heat capacity by GUM and Monte Carlo method H.L. Lu, B. Ren, B. Xiao, F. Zhao, J.D. Wang & Y.Q. Yang

127

Quantitative risk analysis of domino effect in petrochemical enterprise based on vulnerability-resilience Y. Lu, M. Zhang, Z. Yi, C. Liang, Y. Chang & X. Cui

132

An optimization strategy for atmospheric tank area layout in pool fire environments C. Liang, M. Zhang, Z. Yi, Y. Lu & Y. Chang

140

An experimental study on the application of separated heat pipes to waste heat discharge water tanks B. Zhao, J. Cheng, K. Qiao, W. Ji, W. Li, X. Xian & F. Chen

146

Synthesis, separation, and purification of cross-linked starch grafted polyacrylamide polymer flocculant X. Li & X. Hao

158

Research on measuring specific heat capacity of organic heat carrier at high temperatures by DSC J. Li, J. Yang, Y. Rong & D. Jin

164

New energy technology and green energy saving and emission reduction A study on the innovation strategy of rammed earth buildings in Huizhou based on passive house technology F. Sun & W. Shu

175

Does energy-saving technological progress effectively promote the energy-saving and CO2 emission reduction? B. Liu

186

An experimental and numerical study on strengthening collapsible loess foundation with plain soil compaction pile X. Zhang, Y. Jia, L. Zhou, Y. Liu & Y. Yang

192

vi

Application and management of green energy-saving in building construction R. Zhao, H. Qiao, Z. Liu, J. Sun & F. Liu Pollution characteristics and human risks of heavy metals in agricultural areas from the gold mine in Hainan Province, China H.-W. Xie

198

204

Carbon targets under the international shipping market analyses Z. Zhang & H. Qian

216

The utilization situation of red mud recycling project J. Tian

221

Study on the high-filling’s influence of the force-deformation on the pile frame structure embankment on the soft soil M. Zhan, H. Weng, S. Zheng & X. Hu

229

An analysis of overseas market promoting modes of Chinese electrical equipment manufacturers H. Xiao, G. Gao & X. Lin

234

Investigation and analysis of college students’ awareness and behavior of waste classification and treatment—taking Wuhan University of Technology as an example Z. Xia, L. Xu, B. Zheng, Z. Wang, Y. Li, Y. Liu & L. Shen

240

Characteristics of cloth masks and medical masks and disposal measures Y. Xu

246

Study on the water quality law of the inlet and outlet water of a water purification station H. Xiao & Y. Li

252

Influence of pretreatment on membrane fouling during the treatment of algae-rich water by microfiltration S. Zhang, F. Ma, W. Xu, J. Wang, Y. Li, Z. Wu & X. Zhang Application of passive green building energy-saving technology in rural construction S. Ying

258 267

Research on the energy-saving effect of heating setting temperature reduction under different window opening behaviors in office buildings C. An & E. Long

276

Structural equation model analysis of influencing factors heterogeneity of enterprise environmental innovation Z. Jiang

283

Analysis of flow field and aerodynamic characteristics of the Ahmed model under different turbulence degrees M. Zhao, Y. Liu, B. Hou, Z. Liu & S. Wu

290

Transformation and upgrading of China’s health tourism low-carbon empowerment industry under the goal of carbon neutrality G. Xiong, J. Deng & B. Ding

296

Coupling path of carbon market and power market in the background of carbon neutrality: Opportunities for renewable energy development L. Jin, G. Shen, X. Wang, M. Wang, L. Sun & D. Wang

304

vii

An empirical study on the influencing factors of carbon emissions in East China based on the STIRPAT model L. Yao & Y. Jiang The regional differences in China’s fertilizer utilization efficiency from 2001 to 2015 X. Huang, T. Zhang, B. Chen & X. Wang A prediction model of power grid hazardous waste generation based on the grey prediction method Y. Jin, Z. Li, X. Xiao, M. Liu & L. Chen Research and design of an intelligent drilling tool management system in coal mines X.-l. Jia

310 316

326 332

Environmental climate governance and sustainable development Planning and construction of beautiful countryside under the background of rural revitalization—a case study of Wangjia Village, Gongchang Town, Jianli City, Hubei Province X. Liu & J. Li Examination of future climate conditions in major transportation hubs in China based on CMIP6 projections M. Wu Research on the technical path of intelligent governance of rural environment Y. Sun

341

346 359

Research on the path of creating the construction of island-type urban ecological civilization—taking an island-type city in China as an example M. Gan & Q. Lv

371

Comprehensive evaluation of low-carbon economy development level based on factor analysis D. Shi & X. Wu

376

Analysis of coordinated evolution of urban environmental-economic system H. Sun

383

Changes in air quality from 2015 to 2021 in Foshan city Y. Liu & S.L. Lin

387

Research on stimulation and reforms of climate environment in refine scale in Xinfadi market area in Beijing X. Yang, W. Gao, F. Fu & S. Li

393

A systematic review of microplastic pollution in the ocean: Taking the Mediterranean Sea, the East China Sea, and the Great Australian Bight as examples L. Zhou

401

Risk assessment of forest fire in Hunan province based on fuzzy analytic hierarchy process K. Wei & H. Rui Exploring the spatial planning of urban park based on user behaviour—taking Jingxian Park in Jimei district as an example C. Wang & J. Wang Design and application of ecological concept in interior space of public buildings X. Cai & Y. Zhang viii

413

424 432

Research on the application of prefabricated interior wall leading interior art decoration X. Li

437

Post-occupancy evaluation of indoor acoustic and thermal environment in college classrooms in cold regions of China Q. Li, Q. Meng, J. Chu, Z. Li, Z. Wen & X. Tang

446

Distribution and sedimentary environment of Qingdao amphioxus in Luanhekou-Beidaihe adjacent sea area S. Zeng & W. Li

457

Ecological advantages and differentiated development of green tourism in counties of Dabie Mountain: Based on the analysis of landscape pattern indices Y. Zhu, Y. Wang & F. Ye

464

A preliminary study on mushroom classification and application of SVM principle to infer the linearly separable dataset Y. Ma, Y. Xia & X. He

470

A comparative study on the photothermic environment and comprehensive energy consumption of building louvers—based on the climatic conditions of Wuhan Y. Xin

477

Analysis of the influence mechanism of heterogeneous environmental regulation on the green innovation efficiency of the Yangtze River Economic Belt R. Xiong

484

Research on planning strategy of Qianjin village in Gongchang town under the background of rural revitalization strategy Y. Sun & R. Liu

492

Research on the current situation of black and odorous water treatment J. Wang, Y. Xu, D. Liang, F. Wang, C. Liao, C. Tang, Z. Zhou & G. Zeng

497

Research on ecological renovation design of rural housing in North China C. Peng, H. Zhang, M. Tang & Y. Liu

502

Urban safety risk index model based on multi-disaster coupling Z. Yi, M. Zhang, C. Liang, Y. Chang, Y. Lu & X. Cui

510

The influence of social interaction on pro-environmental behavior—analysis based on the Chinese General Social Survey X. Liang, Y. Han, Y. Yang & S. Huang

516

Research on enterprise hazardous waste management modes based on reverse supply chains X. Xiao, Y. Jin, Z. Li, M. Liu & L. Chen

522

Author index

527

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Editor(s), ISBN 978-1-032-33172-0

Preface Due to recent pandemic, the 2022 3rd International Conference on Petrochemical Engineering and Green Development (ICPEGD 2022) which was planned to be held in Shanghai, China, was held virtually online during February 25–27, 2022. The decision to hold the virtual conference was made in compliance with many restrictions and regulations that were imposed by countries around the globe. Such restrictions were made to minimize the risk of people contracting or spreading the COVID-19 through physical contact. There were 140 individuals who attended this on-line conference, represented many countries including Malaysia, Singapore and China. ICPEGD 2022 is to bring together innovative academics and industrial experts in the field of Petrochemical Engineering and Green Development to a common forum. The primary goal of the conference is to promote research and developmental activities in Petrochemical Engineering and Green Development and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in Petrochemical Engineering and Green Development and related areas. During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5–10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30–45 minutes to hold their speeches. In the second part, we invited three professors as our keynote speakers. Prof. Guangming Li, from Tongji University, China, performed a speech: Principle and technology of water pollution control and prevention in chemical technology. And then we had Prof. Qing Liu, Shandong University of Science and Technology, China. His research interests include Fuzzy Systems, Intelligent Systems, Knowledge-Based Systems, Neural Networks, Data Mining, Information Retrieval, and Genetic Algorithms. A/Prof. Bin Guan, our finale keynote speaker, from Shanghai Jiao Tong University, China. He delivered a wonderful speech: Catalytic combustion of lean methane assisted by electric field over Pd/Co3O4 catalysts at low temperature. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge. The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: Petrochemical Engineering, Green Development and more related topics of environment. All the papers have been through rigorous review and process to meet the requirements of International publication standard. We would like to acknowledge all of those who supported ICPEGD 2022. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers. We sincerely hope that the ICPEGD 2022 turned out to be a forum for excellent discussions that enabled new ideas to come about, promoting collaborative research. We are sure that the proceedings will serve as an important research source of references and knowledge, which will lead to not only scientific and engineering findings but also new products and technologies. The Committee of ICPEGD 2022

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Editor(s), ISBN 978-1-032-33172-0

Committee members Conference Chairman Prof. Guangming Li, Tongji University, China Academic Committee Academician Jinlong Zhang, East China University of Technology, China Prof. Guangming Li, Tongji University, China Prof. Zifeng Ma, Shanghai Jiao Tong University, China Prof. Fuchen Wang, East China University of Technology, China Prof. Yuanyu Tian, China University of Petroleum (East China), China Prof. Zongyi He School of Materials Science, East China Jiaotong University, China Prof. Jiusheng Li, Shanghai Institute of Advanced Studies, Chinese Academy of Sciences, China Prof. Peng Wu, East China Normal University, China Prof. Yulong Wu, Tsinghua University, China Prof. Zhenghong Luo, Shanghai Jiao Tong University, China Prof. Yongfeng Zhou, Shanghai Jiao Tong University, China Prof. Yong Lu, East China Normal University, China Prof. Xianyong Wei, China University of Mining, China Prof. Yongge Wei, Tsinghua University, China Dr. Binoy K. Saikia, CSIR-North East institute of Science & Technology, China Dr. Ghulam Yasin, Shenzhen University, China Dr. Maru Dessie Walle, Bahir Dar University, China Organizing Committee Prof. Lianhong Zhang, Southwest Petroleum University, China Prof. Jiangong Dong, Shanghai Universities of Applied Sciences, China Prof. Zegang Qiu, Xi’an Shiyou University, China Prof. Junjiang Teng, Guangdong Institute of Petrochemical Technology, China Dr. Navid Bayati, Aalborg University, China

xiii

Performance analysis of petroleum energy and chemical technology

Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Research on the method of improving the drilling rate of horizontal well reservoirs Cong Yan Oil Production Plant PetroChina Daqing Oilfield Co., Ltd., Petrochina, Daqing, China

ABSTRACT: The oil-water transition zone in the eastern part of the Sazhong Development Zone is located on the eastern flank of the anticline in the Sartu Oilfield, among them, three to four Sartu oil layers are sand-mudstone interbeds deposited by rivers and deltas in large inland lake basins, and the oil layer heterogeneity is more serious. To tap the remaining oil in the submerged area, our plant has deployed 24 horizontal wells in the SII1 and SII2 formations The predicted thickness of the target oil layer is generally about 1.0–2.0 m, thinly developed, It is difficult to control the trajectory to extend in the reservoir, our factory through exploration and practice in the process of tracking while drilling, developed a practical approach to design and tracking of horizontal wells. Application and cooperation of various technologies on-site have increased the oil layer drilling rate of horizontal wells to more than 80%, the success rate is over 90%, and it provides technical support for guiding the potential tapping of horizontal wells in the future.

1 FOREWORD Geosteering technology is used in the drilling process through the comprehensive application of measurement-while-drilling data and formation evaluation data while drilling technology to control wellbore trajectory. Our factory has completed the drilling of six horizontal wells in the eastern transition zone. LWD logging is mainly used in the drilling process, geological model, logging, and other technologies to guide trajectory operation, real-time stratigraphic comparison, calculate horizontal displacement, adjust the inclination of the well, and determine whether to hit the target. Due to the complexity of the geological structure of oil and gas reservoirs and uncertainty of stratum change, there is little geological data in the area without wells, difficulty in trajectory control during construction of horizontal wells, grasping the landing point, problems such as deviations in geological models, adjusting the drill to accurately land into and travel through the target layer, and formation of a system and working mode suitable for on-site construction of horizontal wells in the eastern transition zone. It is necessary to carry out research work on the comprehensive steering technology project for horizontal wells. 2 CONTROL THE LANDING POINT WITH THE REAL-TIME COMPARISON OF THE MARKING LAYER, AND MAKE SURE TO GRAB THE DESTINATION LAYER During the drilling of horizontal wells, effective control of the landing point has a direct impact on the construction quality of horizontal wells. The landing site is the pathway into the sand body reservoir, and it is the first key node that needs to be grasped in the drilling process. It is also the guarantee for the follow-up drilling rate improvement. Due to the complex and changeable stratigraphic structure, landing sites can be affected by a variety of factors to accurately grasp the landing point and carry out a stratigraphic comparison of offset wells. Due to the serious heterogeneity of reservoir development in the eastern transition zone, this leads to the lateral instability of the sand body development in this area; thickness variation increases the difficulty DOI 10.1201/9781003318569-1

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of marking layer comparison, especially when the inclination of the ground is large, the greater the impact. To solve this problem, we use geological models as reference tools, combined with measured curve comparison and logging cuttings analysis, calculate the formation dip, try to restore the true thickness of the formation, form a vertical thickness comparison chart, and establish control methods for landing sites. Sedimentary unit sublayers with adjacent wells in vertical-thickness contrast mode are compared. In the comparison process, the offset well with stable thickness is selected as the reference well, at the same time, the first-level standard layer developed between Sa zero and Sa I is selected as the primary comparison marker layer.

Figure 1.

Comparison of the vertical depth of oil layer curve.

3 COMPREHENSIVE RESEARCH AND JUDGMENT, LOGGING OTHER DATA WHILE DRILLING, AND UPDATING THE TUNING MODEL There are usually errors in the field tracking data of horizontal wells, mainly manifested in the complex structure of horizontal wells, resulting in the identification of cuttings in mud logging, creating stratigraphic profiles, difficulty in comparing strata and interpretation while drilling, and affecting the relative accuracy of horizontal well geosteering. The LWD tool is far from the drill bit downhole (Usually between 8–20 meters). For example, B1-61-A314 well models are adjusted in real-time during drilling, effectively guiding the drilling of subsequent reservoirs. The design depth of the well2322m, the destination layer isSII1story. During the drilling process of this well, it was found that the model information value and the logging return information were deviated, hindering subsequent construction. The well encountered a thin layer of oil spot siltstone at 1428 m–1436 m before hitting the target, unable to determine the actual location of the track in the formation. To implement the structure and reservoir, after the on-site personnel agreed, they chose to continue to explore, continue drilling at 86◦ C inclination, if there is an oil-bearing display in a short distance, the oil layer in SII1 is still developed, this layer can be tracked, if there is a large section of mudstone after drilling down, it proves that the bottom of SII1 has been drilled, trajectories need to be adjusted to retrace the thin layers of SII1 development. For example, after a large section of mudstone appears oil-bearing, it has entered the SII2 oil layer. According to this analysis result, we continue to explore about 30 m–50 m, cuttings, and gas gauge continues to show poor, the 4

gamma curve value did not drop. Therefore, it is judged that the drilling here is all mudstone, and it is consistent with the view that the thin sand layer of the previous member is located at the bottom of the SII1 oil layer. To reduce horizontal segment losses, grab the destination layer, and take into account the subsequent downdip trend of the formation. Field trackers quickly optimize the trajectory, and it is calculated that the dip angle of this section is about 1.6 degrees, the vertical thickness of the stratum is about 70 cm, adjust the well inclination based on this, and lift the model structure to the standard reservoir location, encrypted sampling, this oil layer is the same reservoir as the oil layer at 1436 m, reservoir development is discontinuous, well developed here, need to adjust the angle to track this layer as soon as possible.

Figure 2. The actual drilling trajectory of the geological model after well adjustment.

Finally, the well was successfully drilled, the sandstone drilling rate was 78.44%, and the oilbearing sandstone drilling rate was 77.25%. The well has achieved good drilling results under the careful cooperation of various on-site channels and geological models applied during drilling. Well logging, logging, drilling cooperation between various technologies such as construction, adjusting the drilling level in time, and avoiding poorly developed intervals and mudstone layers effectively ensure that the wellbore trajectory travels through the oil layer.

4 ANALYSIS OF ROCK, ELECTRICITY, AND OIL PROPERTIES, PREDICT RESERVOIRS AHEAD OF TIME, AND ADJUST TRAJECTORY FIELDS IN TIME Due to the variability of underground development during the drilling process, possibly drilled into reservoirs other than the designed target, at this time, according to the actual situation analysis, to increase the drilling rate, traceable to better reservoirs, the most general oil layer detectable layer observation, avoid unconventional reservoirs in time. For the well-developed layer, it should be tracked in time; for poorly developed layers and unconventional reservoirs, timely avoidance. Therefore, steps like comprehensive utilization of data while drilling, reference geological modeling, judgment and prediction, and design of the trajectory ahead of time are essential for the guiding work. Trackers can use petrol software to measure while drilling, logging while drilling, logging-while-drilling data, and other information are used to establish a prediction model of logging-while-drilling curves for the distance from the tool to the drill bit according to the trend 5

of the formation dip, provide a pre-adjustment plan to guide and optimize the actual drilling trajectory. Taking well B1-52-A318 as an example, the well is being drilled. Abnormal gas detection began to appear about 1520 meters deep in the well, with the well depth from 1522 m to 1525 m, and the hydrocarbon value rose rapidly from 0.6% to 2.3%. When the cuttings return to 1527 m, the hydrocarbon value reaches a maximum of about 4.7%. At this time, the value of the deep and shallow lateral curves also increases significantly, and there is a significant difference in magnitude. Judging from experience, well logging curves and hydrocarbon values show that this area has entered a better oil interval to improve the encounter rate. The trajectory should be optimized and traced as soon as possible; however, after the mud logging cuttings were reversed, it was found that the cuttings here were brittle and different from conventional sandstones, and the gamma curve also showed a trend of increasing synchronously with the resistivity. Contrary to the sandstone layer curve display, after repeated scrutiny of the cuttings on-site, the reservoir encountered here was determined to be a gray-brown oil shale. Due to the poor quality, brittleness, and undeveloped lamination of oil shale, it has a certain impact on drilling engineering, and the target horizon of the horizontal well is not a shale oil section. It is necessary to adjust the well deviation as soon as possible to avoid the oil shale formation in this section and orientation with LWD. After logging and steering, it is required to reduce the well inclination from 90 degrees to 87.50–88.0 degrees to avoid this well section and find sandstone reservoir as soon as possible. Finally, due to the timely control of the well deviation, after continuing to drill a well spacing, the hydrocarbon value in the field shows a continuous decline, changes in rock sample properties in situ, which avoids the oil shale in this section. It has effectively paved the way for subsequent engineering problems such as stable drilling and cementing. 5 CONCLUSION Horizontal well geosteering tracking is the key to improving the horizontal well drilling rate. Due to the variability of underground development and the complexity of the connection between various technologies, it will cause various difficulties in the actual drilling process of horizontal wells and affect the success rate of drilling. Therefore, we must do a good job of tracking while drilling, use drilling technology to optimize and adjust the trajectory, manage coordination, form an organic whole to make the right decisions, and ensure that geological objectives are met. Our factory summarizes the experience in the process of horizontal well drilling, which forms our own set of tracking patterns and successfully guides the smooth completion of multiple horizontal wells. Horizontal well drilling sees preliminary results. In the future, the steerable well drilling technology will be further improved in software, technical methods, and working modes, providing help for future horizontal well construction in shallow oil layers. REFERENCES Chen Song, Ren Baosheng, Lu Yi, et al. Well Logging Research and Case Analysis in Tracking While Drilling in Horizontal Wells[J]. Journal of Industrial Geophysics, 2009, 12 (06). Li Bin. Application of LWD Steering Technology in Horizontal Well Drilling. Standard and Quality of China Petroleum and Chemical Industry. Li Shaoqin, Jiang Chunlai. Application and Development of Comprehensive Logging in Production[J]. Petroleum Technology Forum, 2007-03: 56–59. Wang Jiahong. Analysis ofApplication Examples of Horizontal Wells in China[M]. Beijing: Petroleum Industry Press, 2003:25–43. Xiao Renfeng, Xiao Xianzhong. Application of geological logging technology in horizontal well geosteering[J]. Technical Research, 2017, 5. Yuan Jinzheng. Application and development status of horizontal well geosteering technology in domestic oil fields[J]. Petrochemical Technology, 2015, 22 (04): 86. Zhou Mingsheng, Tang Haiquan, Li Jihong. Application of Resistivity While Drilling Tool in Geosteering Drilling[J]. Chemical Engineering and Equipment, 2011, (4): 71–72.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Study on the removal of pollutants by double-cathode electrochemical oxidation Ye Jiang, Luyuan Miao & Wucheng Han Department of Agricultural Resources and Environment, Yanbian University, Yanji, Jilin, China

Shuting Qi Sewage Treatment Work, Yanji, Jilin, China

Yue Quan∗ Department of Agricultural Resources and Environment, Yanbian University, Yanji, Jilin, China Department of Environmental Science, Yanbian University, Hunchun, Jilin, China

ABSTRACT: Carmine wastewater was treated by electrochemical oxidation. The effects of single and double cathodes, electrolyte type, wastewater concentration, and current on the decolorization rate of carmine wastewater were discussed. The experimental results showed that the decolorization rate was 97.19% for 0.10 mol/L NaCl, and when the concentration of wastewater was 0.2000 g/L with 1.0 L, the pH value was 6.10, the aeration rate was 0.80 L/min, the electrode material was 316 L stainless steel with 40 mesh, the electrode distance was 2.0 cm, and the electrolysis time was 40.0 min.

1 INTRODUCTION Carmine is the most widely used synthetic pigment and plays an indispensable role (Meric, Selcuk, Belgiono, 2005). Carmine wastewater has a seriously destructive effect on human and microbial health (Mittal 2006; Parmar & Shukla, 2018; Wang et al. 2020). Scientists conducted toxicological experiments on carmine, and found that carmine had teratogenic, carcinogenic, and mutagenic effects (Tsuda et al. 2001). In recent years, electrochemical technology has been widely used for its advantages of large processing capacity, no secondary pollution, and simple operation (Chen et al. 2021), among which electrochemical oxidation has attracted much attention (Chanokya et al. 2021). In this study, the effects of electrolysis types, wastewater concentration, and current on the decolorization rate of carmine wastewater were investigated by using the double-cathode electrochemical method, which provided theoretical and practical support for the treatment of dye wastewater.

2 EXPERIMENT 2.1 Experimental materials The electrolysis was carried out in a reactor with a working volume of 1.0 L, containing 0.2000 g/L of carmine wastewater and a certain amount of electrolyte. The effective area of the working ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-2

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electrode was 10.0 mm ×4.0 mm. The reactor contains a microporous aeration device with an aeration capacity of 0.80 L/min. The electrode distance was 2.0 cm. 2.2 Analysis methods The concentration of carmine wastewater was analyzed via a spectrophotometer at the maximum wavelength of 508.0 nm. 2.3 Design of experiments Firstly, the decolorization rate of carmine wastewater by double cathode electrolytic cell and single cathode electrolytic cell was compared. Secondly, the effects of electrolyte type, current, wastewater concentration, and other conditions were studied. The wastewater was taken out every 5.0 min, and the absorbance was measured by a spectrophotometer.

3 RESULTS AND ANALYSIS 3.1 Effect of double cathode and single cathode electrolytic cell The influence of single cathode and double cathode electrolytic cells is shown in Figure 1. The decolorization rate of the double cathode was higher than the single cathode at 40.0 min. The effective area of the anode plate of the double cathode electrolytic cell is larger, the distribution current is larger, and the internal resistance is smaller (Lee et al. 2007), so higher current efficiency can be obtained. Therefore, dual-cathode electrolytic cells were selected for the next experiments.

Figure 1.

Electrolytic cell type on decolorization rate.

3.2 Effect of electrolyte type The effects of different electrolytes (NaCl, KCl, Na2 SO4 , and Na2 CO3 ) on the carmine decolorization rate were evaluated. As shown in Figure 2, the decolorization rate followed the order: NaCl > KCl > Na2 SO4 > Na2 CO3 . The reason was that NaCl could be indirectly oxidized with ·O.H. at the anode, or directly oxidized into active chlorine with good diffusion and high oxidation potentials, such as Cl2 , HClO, and ClO− , to enhance its oxidation capacity. Therefore, it was better to choose NaCl as an electrolyte. 8

Figure 2.

Effect of electrolytes on decolorization rate.

3.3 Effect of electrolyte concentration As shown in Figure 3, the decolorization rate of carmine wastewater with different concentrations of NaCl showed an upward trend. The higher concentration of ions in the solution, which made for the higher charge, enhanced conductivity. Therefore, from the perspective of the final effect and cost, it was reasonable to choose 0.10 mol/L NaCl as the following experimental condition.

Figure 3.

Effect of electrolyte concentration on decolorization rate.

3.4 Effect of current As shown in Figure 4, the current directly determines the final treatment effect. The higher the current density, the more O.H. would be generated in the anode, and the more O2 will be generated in the cathode. The decolorization rate tended to a downtrend, for a large amount of energy would be consumed in the electrolytic process, resulting in side reactions (Lou et al. 2008). According to the experimental results, when the electrolysis time is 40 min, the decolorization rate of each experimental group is similar, but the higher the current, the higher the energy consumption. Therefore, considering the current comprehensively, 0.75 A is selected. 9

Figure 4.

Effect of current on decolorization rate.

4 CONCLUSION The results showed that the double-cathode electrolysis method has a good effect on the removal of Pollutants. When the electrolyte is NaCl, the concentration is 0.10 mol/L, and the current is 0.75 A, the decolorization rate reached 97.19% at 40.0 min.

ACKNOWLEDGMENTS This work was supported by the National Science Foundation of China (51968073), the Natural Science Foundation of Jilin Province (20210101089JC), and the University Student Innovation and Entrepreneurship Training Programs (2021 years).

REFERENCES Chanokya, P., Nidheesh, P.V., Syam Babu, D., et al. (2021) Treatment of dyeing wastewater by combined sulfate radical based electrochemical advanced oxidation and electrocoagulation processes. Sep. Purif. Technol., 254: 117570. Chen, Z.Y., Xie, G.Y., Pan, Z.C., et al. (2021) A novel Pb/PbO2 electrodes prepared by the method of thermal oxidation- electrochemical oxidation: Characteristic and electrocatalytic oxidation performance J. Alloy. Compd., 851: 156834. Lee, Y.L., Ou, B.L., Yi, H.C. (2007) Effect of frequency and current density on A.C, etching of aluminum electrolytic capacitor foil. J. Mater. Sci. Mater. Electron., 18(5): 627–634. Lou, W., Abbas, M.E., Zhu, L.H., et al. (2008) Rapid quantitative determination of hydrogen peroxide by oxidation decolorization of methyl orange using a Fenton reaction system. Anal. Chim. Acta., 629(1–2): 1–5. Meric, S., Selcuk, H., Belgiono V. (2005) Acute toxicity removal in textile finishing wastewater by Fenton’s oxidation, ozone and coagulation-flocculation processes. Water. Res., 39(6): 1147–1153. Mittal, A. (2006) Adsorption kinetics of removal of a toxic dye, Malachite Green, from wastewater by using hen feathers. J. Hazard. Mater., 133(1–3): 196–202. Parmar, N.D., Shukla, S.R. (2018) Decolorization of dye wastewater by microbial methods-A review. Indian J. Chem Technol., 25(4): 315–323. Tsuda, S., Murakami, M., Matsusaka, N., et al. DNA damage induced by red food dyes orally dam in site red to pregnant and male mice. Toxicol Sci., 2001, 61(1): 92–99. Wang, T., Tang, X.M., Zhang, S.X., et al. (2020) Roles of functional microbial flocculant in dyeing wastewater treatment: Bridging and adsorption. J. Hazard. Mater., 384: 121506.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Treatment of electrochemical oxidation and persulfate for organic compounds Tingchun Yan, Luyan Miao & Wucheng Han Department of Agricultural Resources and Environment, Yanbian University, Yanji, Jilin, P.R. China

Meihan Bao Department of Environmental Science, Yanbian University, Hunchun, Jilin, China

Yue Quan∗ Department of Agricultural Resources and Environment, Yanbian University, Yanji, Jilin, P.R. China Department of Environmental Science, Yanbian University, Hunchun, Jilin, China

ABSTRACT: In this paper, four degradation methods of carmine wastewater were studied. The results showed that electrochemical oxidation-persulfate-Fe2+ displayed the best performance. The decolorization rate and energy consumption reached 98.85% and 1.44 kW·h/kg at 10.0 min when the current was 0.5 A with 2.0 mmol/L persulfate and 0.5 mmol/L FeSO4 .

1 INTRODUCTION More and more organic compounds are entering the environment and causing serious environmental problems. Dye wastewater is one of the biggest problems causing environmental pollution in China. The environment, animal, and human health also had unforeseeable harm (Chowdhury et al. 2020; Muntean et al. 2017; Subbulekshmi & Subramanian 2017; Zaied et al. 2011). At present, the removal methods for different dye wastewater mainly include photocatalysis (Lu et al. 2007), the oxidation method (Sang et al. 2019), the electrochemical method (Muhammad & Mamriz et al. 2020) and Fenton (Vinod et al. 2020). In recent years, sulfate radical and electrochemical oxidation technology has attracted wide attention (Gao et al. 2018). This paper explores the application of sulfate radical and electrochemical oxidation technology in the field of dye wastewater. This research could provide the theoretical basis for the degradation of dye wastewater. 2 MATERIALS AND METHODS 2.1 Experimental materials The experimental device was designed and assembled. The degradation process was carried out in a 2.0 L reactor with ruthenium iridium titanium and stainless-steel mesh as anode and cathode, respectively. The effective area of the positive and negative electrodes was 10.0 mm * 8.0 mm. 2.2 Analysis methods The concentration of carmine wastewater was analyzed using a 723 spectrophotometer at the maximum wavelength of 505.8 nm. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-3

11

2.3 Design of experiments Carmine wastewater (2.0 L) with 100.0 mg/L was added to the reactor with 0.10 mol/L NaCl electrolyte, 1.2 L/min aeration rate, 3.0 cm electrode distance and 0.50 A current. The absorbance of carmine water was determined every 5.0 min. Each experiment was repeated three times and averaged. The effects of the persulfate oxidation method, electrochemical oxidation method, electrochemical oxidation-persulfate method, and electrochemical oxidation-persulfate-Fe2+ on the decolorization rate and the energy consumption were discussed. 3 RESULTS AND ANALYSIS 3.1 Carmine wastewater was treated by persulfate oxidation The decolorization of carmine wastewater by persulfate oxidation is shown in Figure 1. The decolorization rate of carmine wastewater did not change much. The decolorization rate was 22.24% at 10.0 min. Therefore, the effect of persulfate oxidation on the decolorization rate has little change with time increased.

Figure 1.

Effect of persulfate oxidation to treat carmine wastewater.

3.2 Carmine wastewater was treated by electrochemical oxidation As shown in Figure 2, the change in decolorization rate of carmine wastewater treated by electrochemical oxidation was studied. The decolorization rate increased with the increase of

Figure 2.

Effect of electrochemical oxidation to treat carmine wastewater.

12

decolorization time. The decolorization rate increased rapidly to 61.13% at 10.0 min. As shown in Figure 3, 2.50 kW·h/kg of energy consumption was required at 10.0 min. When the reaction reached 35.0 min, 5.55 kW·h/kg of power consumption was required. Therefore, electrochemical oxidation was suitable for the treatment of carmine wastewater, but the energy consumption was large.

Figure 3.

Esp of electrochemical oxidation treated carmine wastewater.

3.3 Carmine wastewater was treated by electrochemical oxidation-persulfate Figures 4 and 5 showed the decolorization rate and energy consumption of carmine wastewater treated by electrochemical oxidation-persulfate. The decolorization rate and energy consumption increased with electrolysis time increased. When the discolorization time was 10.0 min, the decolorization rate and energy consumption increased rapidly to 74.27% and 1.88 kW·h/kg. Finally, the reaction 35.0 min decolorization rate was 99.66%. Therefore, the decolorization rate and energy consumption of this method were better than the electrochemical oxidation method.

Figure 4.

Effect of electrochemical oxidation-persulfate to treat carmine wastewater.

13

Figure 5.

Esp of electrochemical oxidation-persulfate treated carmine wastewater.

3.4 Carmine wastewater was treated by electrochemical oxidation-persulfate-Fe2+ The decolorization rate of carmine wastewater by electrochemical oxidation-persulfate-Fe2+ was shown in Figure 6. The addition of Fe2+ had a great impact on the decolorization rate. When the decolorization time was 10.0 min, the decolorization rate of carmine wastewater increased rapidly to 98.95%. The reason was that Fe2+ activated persulfate quickly, which generated Fe3+ , sulfate, and more ·OH (Wen et al. 2015). The change in energy consumption is shown in Figure 7. When the decolorization time is 10.0 min, the electric energy consumption was 1.44 kW·h/kg. The decolorization rate and energy consumption of this method were better than the electrochemical oxidation-persulfate. Therefore, this system was the best way to treat carmine wastewater.

Figure 6.

Effect of electrochemical oxidation-persulfate-Fe2+ to treat carmine wastewater.

4 CONCLUSION The results showed that the removal performances followed the order: electrochemical oxidationpersulfate-Fe2+ > electrochemical oxidation-persulfate > electrochemical oxidation > persulfate. When the decolorization time was 10.0 min, the decolorization rate and energy consumption reached 98.85% and 1.44 kW·h/kg with electrochemical oxidation-persulfate-Fe2+ . 14

Figure 7.

Esp of electrochemical oxidation-persulfate-Fe2+ treated carmine wastewater.

ACKNOWLEDGMENTS This work was supported by the National Science Foundation of China (No. 51968073), the Natural Science Foundation of Jilin Province (20210101089JC), and the University Student Innovation and Entrepreneurship Training Programs 2022.

REFERENCES Chowdhury, M.F., Khandaker, S, et al. (2020) Current treatment technologies and mechanisms for removal of indigo carmine dyes from wastewater: A review. J. J Mol Liq., 318:114061. Gao, F., Li, Y., et al. (2018) Degradation of bisphenol through transition metals activating persulfate process. J. Ecotoicol Environ Saf., 158: 239–247. Lu, P., Huang, L., Shao, C.L., et al. (2007) Study on oxidative degradation of Rhodamine B water solution by potassium ferrate. J. J Environ Chem., 26(3):366–370. Muhammad, T., Mamriz, M., et al. (2020) Removal of Rhodamine B dye from aqueous solutions using photo-Fenton processes and novel Ni-Cu@MWCNTs photocatalyst. J. J Mol Liq., 312: 113399. Muntean, S., Todea, A., Bakardjieva, S. (2017) Removal of non-benzidine direct red dye from aqueous solution by using natural sorbents: beech and silver fir. J. Water Treat., 312(10):235–250. Sang, W.J., Cui, J.Q., et al. (2019) Degradation of aniline in aqueous solution by dielectric barrier discharge plasma: Mechanism and degradation pathways. J. Chemosphere., 223:416–424. Subbulekshmi, N., Subramanian, E. (2017) High degree Fenton-like catalytic activity of CuO/zeolite X catalyst from coal fly ash in mineralization of indigo carmine dye. J. Environ Biothen Res., 12:228–237. Vinod, K., Manjeet, S., et al. (2020) Ionic liquid induced removal of Rhodamine B from water. J. J Mol Liq., 319: 114195. Wen, D., Shun, K., et al. (2015) Performance of magnetic activated carbon composite as peroxymonosulfate activator and regenerable adsorbent via sulfate radical-mediated oxidation processes. J. J Hazard Mater., 28:1–9. Zaied, M., Chutet, S., et al. (2011) Spontaneous oxidative degradation of indigo carmine by thin films of birnessite electrodeposited onto SnO2 . J. Appl Catal B Environ., 107:42–51.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Study on treatment of phenol wastewater by electrochemical process Jingyi Chen∗ Tianjin University, Yianjin, China

Yikai Yang Guilin University of Technology, Guilin, China

Xiaoqing Zeng Liaocheng University, Liaocheng, China

ABSTRACT: Electrochemical treatment of organic pollutants in wastewater is a promising advanced oxidation technology with high efficiency, ease of operation, and compatibility with the environment. The experiments were carried out by electrochemical treatment of phenol simulated wastewater at room temperature by varying the influencing factors such as the concentration of supporting electrolyte (Na2SO4), loading voltage, Yang value and initial concentration of phenol, using carbon rods from used No.1 dry cell as electrodes and beakers as electrolytic cells, and the results showed that the supporting electrolyte (Na2SO4) concentration of 20.0 g/L, loading voltage of 5.5 V and pH of 8.0 are the best conditions for treating phenol simulated wastewater. Finally, a preliminary discussion on the degradation mechanism of phenol was carried out.

1 INTRODUCTION Phenolic compounds are widely used in industrial manufacturing as the basic raw materials of the organic chemical industry. Because of the high toxicity of phenols, carcinogenic, teratogenic, and potential mutagenic toxicity, when it contaminates the water and soil, it is bound to harm biological growth and reproduction and affect human food and drinking water safety, and then threaten human health. So, the discharge of industrial wastewater containing phenols must have strict regulations. In general, the maximum permissible concentration of volatile phenols in drinking water is 0.001 mg/L. The maximum permissible concentration of volatile phenols in water bodies is 0.002 mg/L. According to this requirement, effective control and treatment measures must be taken for phenolic wastewater; therefore, the treatment of industrial phenolic wastewater has become one of the urgent problems in industrial wastewater treatment (Iniesta et al. 2002). The use of electrochemical methods to degrade certain organic pollutants in wastewater is often cost-effective and efficient. In recent years, the research on electrochemical methods for degrading organic pollutants in wastewater has been increasing, converting non-biochemically degradable organic matter into biochemically degradable organic matter, or making non-biochemically degradable organic matter burn to produce CO2 , and H2 O with good effect. However, since electrochemical processes often include complex intermediate steps such as mass transfer, reaction, and polarization, the target reaction requires more precise process measurement and control to facilitate. On the other hand, wastewater often has multiple components and complex states. Therefore, electrochemistry for environmental applications requires more detailed experimental studies and theoretical investigations of the underlying processes. Due to its self-polymerization and polymerization with other ∗ Corresponding Author:

16

[email protected]

DOI 10.1201/9781003318569-4

substances, phenol can undergo many downstream reactions in the environment, with both apparent and potential hazards to organisms and humans. The effect of phenol’s self-polymerization on the electrode surface in an electrochemical reaction system is typical of such polymeric substances, and the study of this reaction system can clarify the technical aspects of electrochemical methods and polarization prevention strategies (Lin et al. 1998).

2 ELECTROCHEMICAL OXIDATION METHOD Electrochemical oxidation is a method that uses the high potential and catalytic activity of the anode to produce a strong oxidant such as hydroxyl radicals to degrade the toxic compounds in solution, which has the advantages of high treatment efficiency, simple operation and compatibility with the environment (Ma et al. 2009). According to the different oxidation mechanisms, electrochemical oxidation can be divided into direct oxidation and indirect oxidation, and the anodic direct oxidation process mainly relies on the oxidation of the anode to directly oxidize organic substances. Indirect oxidation is the indirect oxidation of organic matter in wastewater through the generation of strong oxidants by some groups in the anodic oxidation solution. These groups can be anions in the wastewater, such as when treating chlorophenolic wastewater, to produce new ecological chlorine or further formation of hypochlorite, thus degrading the organic matter in the water by strong oxidation, or they can be applied reversible redox electric pairs to degrade organic phenols by using their conversion between oxidation and reduction states. The catalytic rate of the catalyst varies depending on the potential of the catalyst, and for the same electrode, different catalysts catalyze different effects. (Martínez-Huitle & Panizza 2018). 2.1 Direct oxidation principle The anodic oxidation mechanism contains the process of interaction between strong oxidants such as hydroxyl radicals and phenolic pollutants and the direct transfer of electrons from the phenolic pollutant molecules to the electrode surface. Studies on DSA-type motors have shown that a large amount of HO- can be produced by the oxidation of water or water and OH• (under alkaline conditions) at the anode: 2H2 O—2e− →2HO •+2H+ , OH− —e− →HO • and HO • can further produce the strong oxidant HO2 •: 2HO • → H2 O2 H2 O2 —e− → HO2 • + H+ ; H2 O2 + HO • → HO2 • + H2 O HO • and HO2 • are strong electrophilic reagents, easy to attack the phenolic organic benzene ring on the part of the higher density of electron cloud, electron-philic reaction, but also with the dehydrogenation reaction, electron transfer reaction, oxidation of organic matter or the formation of activated organic radicals to produce a chain of radical reactions, so that the organic matter can be rapidly degraded. In this process, phenol roughly undergoes three stages: firstly, it is attacked by free radicals to produce aromatic ring intermediates; this process is more rapid. Secondly, the intermediates open the ring to produce straight chain organic acids; this reaction is slower. Finally, electrochemical combustion occurs to produce CO2 and H2 O; this process is more difficult to occur (Rajkumar & Palanivelu 2004). 2.2 Principle of indirect oxidation Indirect oxidation is the use of strong oxidants generated by electrochemical reactions, and these substances are transferred to the native solution and react with the pollutant to degrade it. The main forms of indirect oxidation are intermediary electro-oxidation, generation of hypochlorite (ClO− ), 17

generation of H2 O2 , and generation of O3 in a total of four types. Since indirect oxidation plays to some extent both the direct oxidation of the anode and the use of the generated oxidant, the treatment efficiency is greatly improved (Zambrano et al. 2020). 2.3 Prospects for the application of electrochemical oxidation The electrochemical oxidation method has the advantages of a short process and easy operation. As a new type of water treatment technology, electrochemical oxidation has two main application prospects: (1) electrochemical degradation, which generates strong oxidizing substances in the electrolysis process, so that organic pollutants are completely oxidized and degraded into CO2 and H2 O in homogeneous or heterogeneous phases (2) electrochemical conversion, which converts biodegradable organic substances into easily biodegradable aliphatic compounds by electrochemical methods. The electrochemical degradation method for organic wastewater treatment is a promising advanced oxidation technology due to its unique advantages and has extremely broad application prospects in the pre-treatment and deep treatment of organic wastewater (Zhang et al. 2020).

3 EXPERIMENT 3.1 Experimental drugs (all analytically pure) Concentrated sulfuric acid (H2 SO4 ), sodium hydroxide (NaOH), phenol (C6 H5 OH), sodium sulfate crystals (Na2 SO4 -10H2 O), ultrapure water and distilled water, etc. 3.2 Experimental instruments Instruments

Model

Regulated DC Power Supply Digital Thermostat Magnetic Stirrer Electronic analytical balance Acidity meter (PH meter)

HB17301SC HJ-3 BS124S (Max120g d=0.0001g) METTLER TOLEDO 320 pH METER Agilent 1100 LC

High Performance Liquid Chromatograph

3.3 Experimental methods The experimental flow chart is shown in Figure 1.

Figure 1.

Schematic diagram of the experimental device and process flow.

18

The experimental procedure was as follows: simulated wastewater solutions with phenol concentration of 0.60 g/L (0.30 g/L) and supporting electrolyte (Na2SO4) concentration of 20.0 g/L (10.0 g/L, 30.0 g/L) were prepared respectively. Electrolysis was performed at a certain voltage, pH and temperature using carbon rods as electrodes for a total of 240 min. Samples were taken at different electrolysis times (every 20 min), filtered twice after electrolysis and extracted. The un-electrolyzed solution and the solution to be measured at different electrolysis times were taken and injected into the high-performance liquid chromatography (mobile phase: 30% methanol/70% water; room temperature; flow rate: 1.2 ml/min: pump pressure: 110 bar, injection volume: 20 µl) in turn for analysis. By comparing the spectra at different electrolysis times, the retention time and peak height (or peak area) of the components in the spectra can be used to make a preliminary determination of the degradation of phenol and the formation of intermediates. The degradation rate of phenol was used to reflect the degradation of phenol in the course of the experiment with the following equation: R=[(A0 —Ai )/A0 ]×100% R—degradation rate of phenol, %. A0 —peak area of phenol in the absence of electrolysis. Ai —peak area of phenol during electrolysis for 20 min to 240 min with an interval of 20 min.

4 RESULTS AND DISCUSSION 4.1 Factors affecting electrochemical oxidative degradation 4.1.1 Electrodes In the research process of the electrochemical oxidation method, the selection and preparation of electrodes are more important, but due to the limited conditions, this experiment is not studied and explored, and only the carbon rods in the dry cell are selected as electrodes (carbon electrodes) for electrolysis. 4.1.2 Concentration of supporting electrolytes In the experiment, we selected sodium sulfate (Na2 SO4 ) as the supporting electrolyte and prepared three simulated wastewater solutions with a phenol concentration of 0.60 g/L and a supporting electrolyte (Na2 SO4 ) concentration of 10.0 g/L (20.0 g/L, 30.0 g/L), respectively. Electrolysis was performed at a loading voltage of 4.0 V and a pH value of 8.0 for 240 min, and the samples were sampled at 20 min intervals and injected into a high-performance liquid chromatography for detection and analysis. According to the degradation effect of phenol, it can be seen that the degradation rate of phenol is relatively low at Na2 SO4 , with a concentration of 10.0 g/h and 30.0 g/h; while when Na2 SO4 , the concentration of 20.0 g/L, the degradation effect of phenol is relatively good, and the degradation rate at 240 min can reach 59.52%, and it can be seen that with the increase of electrolysis time, the degradation rate of phenol has It can be seen that the degradation rate of phenol tends to continue to increase with the increase of electrolysis time. 4.1.3 Load voltage A simulated wastewater solution with a phenol concentration of 0.60 g/L and a supporting electrolyte (Na2 SO4 ) concentration of 20.0 g/L was prepared. Electrolysis was performed at pH 8.0, room temperature, and loading voltages of 4.0V, 5.5V, and 7.0V, respectively. The samples were processed after electrolysis and injected into the high-performance liquid chromatography for detection and analysis, and the analytical results are shown in Figure 2. From the figure, it can be seen that at a voltage of 5.5 V, when the degradation time is 120 min, the phenol has basically been completely degraded; when the voltage is 7.0 V, the complete degradation time should be more than 60 min; 19

thus it can be concluded that the degradation effect is better at a voltage of 5.5 V. (Zhang et al. 2013).

Figure 2.

Degradation rate of phenol under different load voltages.

4.1.4 Initial concentration of phenol During the experiments, we only considered the cases of phenol at concentrations of 0.30 g/L and 0.60 g/L under the condition that the concentration of the supporting electrolyte (Na2SO4) was 20.0 g/L. The degradation rate of phenol decreased with increasing its initial concentration, and its total degradation increased with increasing the initial concentration. 4.1.5 Other influencing factors During the study of the electrochemical treatment of simulated phenol wastewater, there were some other influencing factors, but due to the limited experimental conditions, the remaining conditions (e.g., type of supporting electrolyte, current density, temperature, pH, etc.) were taken into account but not experimentally studied.

4.2 Exploration of phenol degradation mechanism Although the process of electrochemical oxidation is very complex and different researchers have proposed different oxidation mechanisms for different catalytic systems. However, it is generally accepted that the anodic oxidative degradation of organic matter is through the transfer of oxygen atoms, which are transferred from water molecules to organic matter due to the electrochemical oxidation of water. The degradation history of phenol can be summarized in 3 processes: (1) In the early stages of the reaction, the products of phenol degradation still have a conjugated system or double bond structure similar to the benzene ring, so the benzene ring is not fully opened at this time. These intermediate products may be quinones or small amounts of hydroquinone or catechol. (2) As the reaction time increases, the number of quinone compounds first increases and then decreases. The degradation of quinone compounds may produce some small molecules of organic acids. The main product at the beginning is butenedioic acid, and as the oxidation continues, the carbon chain continues to break into oxalic acid. (3) Some of the small molecule organic acids are further oxidized to produce the end products of carbon dioxide and water. In fact, the first two processes occur essentially simultaneously and constitute intermediate degradation products, while the third process proceeds relatively slowly, culminating in the end products of carbon dioxide and water. The electrochemical oxidative degradation course of phenol is postulated as follows: 20

5 CONCLUSION An apparatus and process for the electrochemical oxidative degradation of simulated wastewater containing phenol was designed under the conditions allowed in the laboratory. The electrochemical oxidative degradation characteristics of phenol were investigated using a carbon rod as the electrode, a beaker as the simulated electrolyzer, a regulated DC power supply to provide the loading voltage, and a thermostatic magnetic stirrer to control the temperature and the stirring rate of the solution. The effects of the supporting electrolyte concentration, loading voltage, and initial phenol concentration on the degradation effect of phenol were investigated. The degradation mechanism was discussed, and the following conclusions were obtained. (1) Under the conditions of supporting electrolyte sodium sulfate (Na2 SO4 ) concentration of 20.0 g/L, loading voltage of 5.5 V, pH value of 8.0 and room temperature, the solution was electrolyzed for 60 min to simulate the wastewater solution, and the solution was analyzed by high-performance liquid chromatography, and the degradation effect of phenol was most obvious. The supported electrolyte concentration, loading voltage, and initial phenol concentration all had important effects on the degradation of phenol. Overall, the method is promising for the treatment of wastewater containing phenol in large concentrations with certain salt content, and can be directly treated without pre-treatment such as dilution or neutralization and conditioning. (2) The degradation process of phenol is relatively complex, and different conditions can make certain changes in the degradation process. The main degradation products of phenol are benzoquinone, butenedioic acid and oxalic acid, and the end products are carbon dioxide and water. The specific degradation mechanism needs to be further studied and explored. ACKNOWLEDGMENTS This work was financially supported by the Applied Research Project of Public Welfare Technology of Zhejiang Province (2017xxxxxxx). REFERENCES Iniesta, J., Expósito, E., González-Garcıa, J., Montiel, V., & Aldaz, A. (2002). Electrochemical treatment of industrial wastewater containing phenols. Journal of the Electrochemical Society, 149(5), D57. Lin, S. H., Shyu, C. T., & Sun, M. C. (1998). Saline wastewater treatment by electrochemical method. Water Research, 32(4), 1059–1066. Ma, H., Zhang, X., Ma, Q., & Wang, B. (2009). Electrochemical catalytic treatment of phenol wastewater. Journal of Hazardous materials, 165(1–3), 475–480. Martínez-Huitle, C. A., & Panizza, M. (2018). Electrochemical oxidation of organic pollutants for wastewater treatment. Current Opinion in Electrochemistry, 11, 62–71. Rajkumar, D., & Palanivelu, K. (2004). Electrochemical treatment of industrial wastewater. Journal of hazardous materials, 113(1–3), 123–129. Zambrano, J., Park, H., & Min, B. (2020). Enhancing electrochemical degradation of phenol at optimum pH condition with a Pt/Ti anode electrode. Environmental Technology, 41(24), 3248–3259. Zhang, C., Jiang, Y., Li, Y., Hu, Z., Zhou, L., & Zhou, M. (2013). Three-dimensional electrochemical process for wastewater treatment: a general review. Chemical Engineering Journal, 228, 455–467. Zhang, M., Zhang, Z., Liu, S., Peng, Y., Chen, J., & Ki, S. Y. (2020). Ultrasound-assisted electrochemical treatment for phenolic wastewater. Ultrasonics sonochemistry, 65, 105058.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Study on a kind of alkaline polyacrylamide/Cr gel breaker for oil extraction F. Chen, E.L. Zhao & G.S. Zhao School of Science, Northeastern University, Shenyang, China

S.J. Cao Liaohe Petroleum Exploration Bureau Co., Ltd., Panjin, China

Y.J. Wang PetroChina Company Limited Liaohe Oilfield Branch, Panjin, China

ABSTRACT: The use of PAM/Cr gel as a water plugging agent in tertiary oil recovery is a technology that has been used for more than ten years. With the use of this water plugging agent, a large number of waste gels are generated. Because the gel is mixed with oily substances, it is difficult to effectively break glue decomposition processing, such as random disposal, which will pollute the environment. This paper studied saturated cardanol polyoxyethylene combined with alkaline oxidative radicals in an alkaline system to obtain a breaker for PAM/Cr gels. Through orthogonal design experiments, the optimal ratio of breaker with saturated cardanol polyoxyethylene and alkaline peroxide combined with stabilizer was screened out and verified by industrial experiments. The experimental results show that this gel breaker has a good sol effect, can break oil-containing PAM/Cr gel at room temperature, meets the requirements of industrial applications, and has broad application prospects.

1 INTRODUCTION With the development of tertiary oil recovery technology (Liao et al. 2017) based on polyacrylamide (PAM) oil displacement technology, the use of polyacrylamide as the main component of polymer injection agent is more and more widely used in oilfield development. Polyacrylamide can form colloidal substances with Cr3+ and high-value metals and organic substances to achieve water plugging, especially for oil wells with high temperatures and high salt. It has the advantages of high viscosity, strong plugging ability, and wide application range (Jing et al. 2015). However, the PAM/Cr gel will be deposited near the wellbore during long-term use, and the pressure release will cause the back-spitting of the displacement agent, which will block the oil flow pipe, production string and infusion pipe, so that the recovered oil pipe cannot be reused, increasing the cost and loss. The chemical residues at the bottom and sides of the liquid tank need to be cleaned every year to recycle the chemical waste, and there is no reasonable recycling method, which pollutes the soil and water bodies and affects human health (Hu et al. 2018). In addition, the polyacrylamide colloid has a large number of oil stains, which makes the treatment more difficult. There are physical methods for degrading polyacrylamide, such as ultrasonic waves, high-energy gas fracturing and high-pressure water jet, etc., but the application conditions and equipment requirements are high, and it is difficult to promote (Yen & Yang 2003). There are also chemical methods, which use degradants (Guo et al. 1998), oxidants (Fu et al. 2020) and surfactants to degrade polyacrylamide gel (Vijayalakshmi & Madras 2006); and biological methods, which use bacteria (Nie et al. 2016), enzymes (Bao et al. 2010) and other substances to degrade polyacrylamide, which is green and efficient. However, the common methods for degrading polyacrylamide 22

DOI 10.1201/9781003318569-5

are difficult to degrade PAM/Cr gel effectively, and there is no report on PAM/Cr gel degradation. The degradation of polyacrylamide hydrogels has been an urgent problem to be solved in tertiary oil recovery for many years. Therefore, in this paper, an alkaline breaker was obtained based on cardanol surfactants, which were used to dissolve PAM/Cr gels. Cardanol polyoxyethylene ether (MPE) is a surfactant obtained by reacting phenolic compounds with unsaturated long aliphatic chains (Zhang et al. 2013) with ethylene oxide. Similar, non-toxic and harmless, green and environmental protection (Gedam & Sampathkumaran 1986). Through orthogonal design experiments, the optimal ratio of breaker with saturated cardanol polyoxyethylene and alkaline peroxide combined with stabilizer was screened out, and it was verified by verification tests and industrial experiments.

2 EXPERIMENTAL PART 2.1 Reagent The reagents used are as follows: analytically pure sulfuric acid from Sinopharm Group Chemical Reagent Company; analytically pure sodium carbonate from Shanghai Hongguang Chemical Factory; analytically pure sodium chloride, ethanol absolute, EDTA and sodium hydroxide from Tianjin Damao Chemical Reagent Factory; 30% hydrogen peroxide from Tianjin Yongda Chemical Reagent Co., Ltd.; industrial-used stabilizer from Hebei Xietong Chemical Co., Ltd.; 99% MPE from Zhengzhou Dongda Zhonghuan Chemical Technology Co., Ltd. 2.2 Experimental method 2.2.1 Formulation of alkaline gel breaker Add 2.00 g of sodium hydroxide, a small amount of deionized water and 0.15 g of stabilizer to the test tube. When the inner wall of the test tube is no longer heated, add 0.06 g of MPE, slowly add 20.00 g of peroxide, and finally add distilled water to a total of 100.00 g to obtain an alkaline gel breaker. 2.2.2 Experiment on sol performance of optimal formulation of alkaline gel breaker Take 13.00 g PAM/Cr gel block, cut it into a cube with a side length of 1.0 cm, fill it into a glass tube with a diameter of 1.0 cm and a length of 13 cm, put it into a beaker, and add 300.00 g of alkaline gel, and the dissolution time of the gel was measured. 2.2.3 Simulative preparation experiment of alkaline gel breaker in the sealed pipeline In order to further conform to the actual situation, to simulate the PAM/Cr gel in the oil production pipeline, place two PAM/Cr gel blocks in a glass tube with a length of 10 cm and an inner diameter of 1 cm, put them into a 1000 mL beaker, and add 300.00 g of alkali. The gel breaker was used to measure the time for the gel to dissolve completely.

3 RESULTS AND DISCUSSION 3.1 Selection of reagents Add the same amount of surfactant and other drugs to each test tube, let stand for 24 hours, and observe the change of PAM/Cr gel. It can reduce the viscosity of the solution. The results are shown in Table 1. It can be concluded from experiment number 5 that the compound of hydrogen peroxide and MPE can reduce the viscosity of the solution. Compared with experiment number 8, it can be concluded that sodium hydroxide is a good auxiliary agent. Therefore, MPE, hydrogen peroxide and sodium hydroxide are selected as the alkaline sol formulation. Due to the exothermic heat during the reaction process, a certain amount of stabilizer is added to ensure the smooth progress of the reaction process. 23

Table 1. Selection result table of alkaline sol agent. Number

Reagents

Phenomena

1 2 3 4 5 6 7

sodium chloride, MPE ethanol absolute, MPE EDTA, sodium chloride, MPE sodium carbonate, MPE hydrogen peroxide, MPE sodium hydroxide, MPE sulfuric acid, hydrogen peroxide, MPE

8

sodium hydroxide, hydrogen peroxide, MPE

no significant change in gel no significant change in gel gel swelling gel swelling gel into solution, liquid is not sticky gel swelling bubbles are generated, the gel is partially dissolved, and the liquid is not sticky bubbles are generated, the gel is all dissolved, and the liquid is not sticky

3.2 Investigation of influencing factors The gel breaker was prepared with different amounts of MPE, and the gel breaking effect of the alkaline gel breaker was measured, as shown in Figure 1. As the amount of MPE increase, the gel breaking time decrease. When the amount of MPE was 0.06%, it entered the platform. Therefore, it is more appropriate to choose 0.06%.

Figure 1.

MPE single factor inspection chart.

3.3 Orthogonal experiment The time for the gel to dissolve completely is a factor to be considered in this orthogonal experiment. The experiment results are shown in Table 2. It can be seen from Table 2 that the magnitude of the range R1 is B>C>D>A, indicating the influence of the factors as follows: sodium hydroxide content>peroxide content>stabilizer content>MPE content. From the results of orthogonal experiments, the optimal levels of factors are A2 , B2 , C3 , and D1 . Therefore, the optimal formula of PAM/Cr gel alkaline gel breaker is MPE content of 0.06%, sodium hydroxide content of 2.00%, hydrogen peroxide content of 20.00%, and stabilizer content of 0.15%. 24

Table 2. L9(34) Orthogonal analysis table. Number

MPE/%

Sodium hydroxide/%

1 2 3 4 5 6 7 8 9 I1 II2 III3 range R1 order optimal level optimal order

1 (0.04) 1 (0.04) 1 (0.04) 2 (0.06) 2 (0.06) 2 (0.06) 3 (0.08) 3 (0.08) 3 (0.08) 151.333 149.667 153.667 4.000

1 (1.50) 2 (2.00) 3 (2.50) 1 (1.50) 2 (2.00) 3 (2.50) 1 (1.50) 2 (2.00) 3 (2.50) 158.667 138.000 158.000 20.667

A2

B2

Hydrogen peroxide/%

1 (10.00) 2 (15.00) 3 (20.00) 2 (15.00) 3 (20.00) 1 (10.00) 3 (20.00) 1 (10.00) 2 (15.00) 160.000 149.333 145.333 14.667 B> C > D>A C3 A 2 B2 C3 D1

Stabilizer/% 1 (0.15) 2 (0.20) 3 (0.25) 3 (0.25) 1 (0.15) 2 (0.20) 2 (0.20) 3 (0.25) 1 (0.15) 149.667 155.000 150.000 5.333

Dissolution time/min 165 139 150 153 128 168 158 147 156

D1

3.4 Determination of sol properties of optimal formulation of alkaline gel breaker 3.4.1 Sol performance of optimal formulation of alkaline gel breaker The comparison before and after the alkaline gel breaker dissolves the glue block is shown in Figure 2. It can be seen from Figure 2 that the dissolution time of the glue block was 128 min, and the dissolution effect was good. After 60 minutes, the glue block floated to the surface of the gel breaker. There was a strong irritating odor during the dissolution process, and the solution turned from light yellow to yellow-green. It shows that the gel breaker has a good effect, the main polyacrylamide chain is broken, and small molecular gas is generated.

Figure 2.

Small attempt at the dissolution performance of alkaline sols.

3.4.2 Sol simulation experiment of optimal formulation of alkaline gel breaker in the sealed pipeline The results of the sol simulation experiment of the optimal formulation of the alkaline gel breaker on the glue block in the blocked pipe are shown in Figure 3. 25

It can be seen from Figure 3 that after 48 hours of dissolution, the dissolution of the glue blocks in the blocked tube had a good effect, the gel breaker still had a certain permeability and solubility, and the stability was good. The change from light yellow to yellow-green indicated that the gel breaker has a good dissolving effect on the glue blocks in the blocked tube.

Figure 3. The static dissolution diagram of the rubber block in the clogged tube by the alkaline sol.

3.4.3 Scale-up experiment of performance of optimal formulation of alkaline gel breaker Take 500.00 g of PAM/Cr gel in a beaker, add 1500.00 g of gel breaker, and measure the time for complete dissolution. The experimental results are shown in Figure 4.

Figure 4. The effect diagram of the scale-up experiment of the dissolution performance of the alkaline sol.

26

It can be seen from Figure 4 that under the optimal formula, the dissolution time of the glue block is 43.5 h. At this time, the alkaline gel breaker still has stability and certain permeability, and the glue block appears in the dissolution process. The experimental phenomenon shows that the alkaline gel breaker is still effective after the scale-up experiment. 3.4.4 Industrial experimental results of the solubility of alkaline gel breakers In the field experiment at Baoyi Combined Station of Horqin Oil Production Plant, the on-site gel 120 m3 with a solid content of 49.8% was a non-flowing gel elastomer, as shown in Figure 5(a). After adding the stirring device, the gel breaker was added. After 48 hours, the solid gel was dissolved into a flowable liquid, as shown in Figure 5(b). After the gel is broken, the waste liquid can be discharged into the factory waste liquid treatment system after neutralization and simple reduction treatment.

Figure 5.

Industrial experiment picture of PAM/Cr gel dissolved in Baoyi Joint Station.

4 CONCLUSION In this paper, an alkaline breaker is applied to the dissolution of PAM/Cr gels. The main conclusions can be summarized as follows: (1) The optimal proportions of alkaline gel breakers are: MPE content 0.06%, sodium hydroxide content 2.00%, hydrogen peroxide content 20.00%, stabilizer content 0.15%. (2) The alkaline gel breaker is applied to the dissolution and industrial test of PAM/Cr gel; the dissolution effect is good and economical. (3) All components of the alkaline gel breaker are environmentally friendly, and the dissolved product of the PAM/Cr gel can be treated by the existing water treatment process in the oil extraction plant to meet the discharge standard. In terms of future work, the alkaline breaker should be carried out to enhance the treatment of waste PAM/Cr gel after oil displacement.

REFERENCES Bao, M. T. et al. (2010) Biodegradation of partially hydrolyzed polyacrylamide by bacteria isolated from production water after polymer flooding in an oil field. J. Journal of Hazardous Materials. 184(1): 105–110.

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Fu, X. et al. (2020) Y. Thermal decomposition behavior and mechanism study of cationic polyacrylamide. J. Journal of Thermal Analysis and Calorimetry. Guo, J. P. et al. (1998) The accelerated degradation of aqueous polyacrylamide at low temperature. J. Journal of Applied Polymer Science. 69: 791–797. Gedam, P. H. & P. S. Sampathkumaran (1986). Cashew nut shell liquid: extraction, chemistry and applications. J. Progress in Organic Coatings. 14: 115–157. Hu, H. et al. (2018) Anaerobic biodegradation of partially hydrolyzed polyacrylamide in long-term methanogenic enrichment cultures from production water of oil reservoirs. J. Biodegradation. 29: 233–243. Jing, J. Q. et al. (2015) Salt resistance of surfactants and anionic Polyacrylamide combined system. J. Polymer Bulletin. 5: 61–68. Liao, G. Z. et al. (2017) Chemical flooding development status and prospect. J. Acta Petrolei Sinica. 38(2): 196–207. Nie, C. H. et al. (2016) Towards efficient demulsification of produced water in oilfields: solar STEP directional degradation of polymer on interfacial film of emulsions. J. Energy & Fuels. 30(11) :9686–9692. Vijayalakshmi, S. P. & G. Madras (2006). Photocatalytic degradation of poly (ethylene oxide) and polyacrylamide. J. Journal of Applied Polymer Science. 100 (5): 3997–4003. Yen, H. Y. & M. H. Yang (2003). The ultrasonic degradation of polyacrylamide solution. J. Polymer Testing. 22(2): 129–131. Zhang, Y. et al. (2013) Enzyme-substrate binding landscapes in the process of nitrile biodegradation mediated by nitrile hydratase and amidase. J. Applied biochemistry and biotechnology. 170(7): 1614–23.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Effects of multi-wall carbon nanotubes on seed germination and seedling growth of Water lotus Shuangxi Wen, Peng Li, Yaya Zhao, Jing Ran, Juanjuan Zhang & Mi Xiao∗ College of Biological and Environmental Engineering, Guiyang University, Guiyang, Guizhou Province, China

ABSTRACT: This study aimed to investigate multi-wall carbon nanotubes (MWCNTs) toxicity in Water lotus which is commonly used in constructed wetlands. The seed germination, plantlet development, and physiology were evaluated by exposure experiments. The results of the seed germination experiment showed that different concentrations of MWCNTs (0, 5, 50, 100, 200 mg/L) had a certain inhibitory effect on the germination of Water lotus seeds, but the inhibitory effect was the smallest at the concentration of 100 mg/L. The results of the seedling growth experiment showed that the stem length and fresh weight ofWater lotus chinensis seedlings treated with different concentrations of MWCNTs decreased in varying degrees compared with the control group, but the root elongation increased in varying degrees compared with the control group. It proved that MWCNTs could inhibit the growth of stems and leaves of Water lotus chinensis seedlings, but could promote the growth and development of roots.

1 INTRODUCTION Multi-walled carbon nanotubes have been widely used in the fields of chemistry, food, and biology at present (Liu 2020). During production and use, MWCNTs will inevitably be released into the environment. The toxic effects and potential health risks to humans after entering the environment have attracted extensive attention in the academic community (Guaglianoni 2019; Mouchet 2010). Such widespread use of nanosized MWCNTs could cause a significant release of MWCNTs into the environment, thereby leading to a potential for increased environmental exposure to MWCNTs (Macwan 2011; Yuan 2017). NPs may pose novel health and environmental risks that cannot be predicted by current knowledge of the behavior of macroscopic particles (Yin 2020). Therefore, the safety of NPs must be established when considering the further development and applications for nanotechnology. Plants provide a potential pathway for the transport of nanoparticles (NPs) to the environment and serve as an important route for their bioaccumulation into the food chain (Wen 2019). The nanomaterials will eventually enter the water body through dry or wet sedimentation and rainwater scouring after entering the environment (Petersen 2011). Therefore, it is very necessary to investigate the impact of carbon nanomaterials on the growth and development of aquatic plants. However, the research reports on the ecotoxicological effects of MWCNTs on aquatic plants are still very limited. The water lotus is the most common plant used in constructed wetlands. It has a very short stem and radial growth of leaves, with a diameter of up to 30 cm. The leaf surface is yellow-green and the back is white. Both sides are covered with white transparent fluff. The rhizome (lotus root) is hypertrophic with many nodes and grows transversely in the underwater mud. The Lotus flower is a perennial floating plant with strong reproductive ability, easy supervision, no biological invasion, ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-6

29

and can absorb a large number of nutrient elements such as N and P in the water body. It is of great significance to the research on eutrophication control of river water bodies, and the lotus flower can be used as a landscape plant for people to view and admire in constructed wetlands. The present study aims to investigate the toxicity of MWCNTs on Water lotus, water culture experiments on seed germination, and seedling growth of Water lotus treated with different concentrations of MWCNTs were carried out. The growth indexes such as seed germination rate, germination potential, seedling fresh weight, seedling length, and root length were measured. 2 MATERIALS AND METHODS 2.1 Materials Multi-wall carbon nanotubes (content ≥ 99.9%, pipe diameter: 3–15 nm, pipe length: 15–30 µm) were purchased from Beijing Nachen Co., Ltd. Seeds of Water lotus were purchased from Nanjing Jingxiangyuan Co., Ltd. 2.2 Seed germination test Water lotus seeds with intact appearance and consistent size were selected for the germination experiment. The selected seeds were sterilized for 10 min in 10% hydrogen peroxide solution before application. The sterilized seeds were then rinsed with sterile distilled water until no sodium hypochlorite odor remained. Make a small opening on the epidermis of seeds with scissors to facilitate water to enter the seeds and promote germination. Soak the seeds in distilled water for 48 hours and replace the water every 12 hours. There are five treatments of 0, 5, 50, 100, and 200 mg/L of MWCNTs solutions were set for the experiment. Each treatment was set with 3 repetitions and 6 seeds in each repetition. The pretreated seeds were placed in disposable plastic bowls and 200 ml of MWCNTs solution with different concentrations were poured into each bowl. Then the bowls were covered with fresh-keeping film and 20 holes were pricked on the film with a needle, and the solution was stirred every 3 hours and replaced every 3 days to avoid serious agglomeration of MWCNTs and odorization of the water. Seeds were considered germinated when they swelled with water and sprouted to at least 1/2 of the seed length, and the germination of the seeds was counted regularly every day. 2.3 Seedling culture and exposure Following the experiment in 2.2, the Water lotus seedlings were cultured until the 27th day, and the seedling length, root length, stem length, root weight, and seedling weight were measured. All experiments were conducted in triplicate. 3 RESULTS AND DISCUSSION 3.1 Seed germination The germination rate and germination potential of Water lotus seeds treated with different concentrations of MWCNTs solution are shown in Figure 1. It can be seen from the figure that the germination rate and germination potential of Water lotus seeds show changing trend of first increasing and then decreasing when the concentration of MWCNTs is between 5∼200 mg/L. Both of them reached the maximum at 100 mg/L, which were 70.00% and 64.50% respectively, and reached the minimum value at 200 mg/L, which were 37.78% and 30.15% respectively. In addition, it can also be seen from the figure that the germination rate and germination potential of all treatment concentrations were significantly lower than those of the control treatment, indicating that MWCNTs treatment can inhibit the germination of Water lotus seeds, but the inhibition effect is the weakest at the concentration of 100 mg/L. 30

Figure 1.

Germination rates and germination potential of Water lotus seeds after MWCNTs treatment.

3.2 Seedling growth The weight of Water lotus seedlings cultured in different concentrations of MWCNTs solution is shown in Figure 2. It can be seen from the figure that under the four treatment concentrations, the

Figure 2.

Seedling masses of Water lotus after MWCNTs treatment.

31

fresh weight of Water lotus seedlings increased with the increase of concentration at first. When the concentration of MWCNTs was 100 mg/L, the fresh weight of Water lotus seedlings reached the maximum value of 3.33 g. Then, with the increase of MWCNTs concentration, the fresh weight of Water lotus seedlings decreased rapidly. When the concentration was 200 mg/L, the fresh weight of seedlings reached the minimum value of 1.35 g. Due to the changing trend of germination rate and germination potential with treatment concentration, the fresh weight of seedlings in all MWCNTs treatment concentrations was less than that in the control treatment (3.54 g).

Figure 3.

Seedling length and root length of Water lotus after MWCNTs treatment.

The changing trend of the seedling length and root elongation of Water lotus seedlings under different concentrations MWCNTs were shown in Figure 3. It can be seen from the figure that compared with the control, the seedling length of 5, 50, and 200 mg/L MWCNTs treatment decreased to varying degrees, indicating that the MWCNTs inhibited the growth of Water lotus seedlings to a certain extent under these concentrations, but the seedling length of 100 mg/L MWCNTs was slightly longer than that of the control, with seedling lengths of 47.6 cm and 49.5 cm respectively. The results showed that MWCNTs could slightly promote the growth of Water lotus seedlings at this concentration. In addition, it can be seen from Figure 3 that after treatment with several different concentrations of MWCNTs, except that the root length of 5 mg/L treatment at low concentration is slightly lower than that of the control, the root elongation of 50, 100, and 200 mg/L treatment is 1.8, 1.9 and 1.5 cm respectively, which are higher than that of the control treatment, indicating that MWCNTs can promote the root elongation of Water lotus at medium and high concentration.

4 CONCLUSION In this work, the effects of MWCNTs on Seed Germination and plant growth of Water lotus were investigated through the exposure experiment of seeds and seedlings, and the ecotoxicological effects of MWCNTs on aquatic plants after entering water were studied. The results showed that 32

although the appropriate concentration of carbon nanotubes could regulate the internal metabolism of plants, promote root growth, improve root activity, and make plant root elongation longer, MWCNTs showed a certain inhibitory effect on the growth of Water lotus at most concentrations, including the reduction of germination rate, germination potential, and plant fresh weight. It shows that MWCNTs have a certain adverse impact on aquatic ecology, and their ecological risk and toxicity mechanism deserve further study.

ACKNOWLEDGMENTS This work was financially supported by the growth project of young scientific and technological talents of the Education Department of Guizhou Province (qianjiaohe KY [2019] 102), the college students’ innovative entrepreneurship training program of Guizhou Province-2021, the Doctoral Scientific Research Foundation of Guiyang University (GYU-ZRD (2018)-004).

REFERENCES Guaglianoni, W.C., Florence, C.L., Bonatto, F., et al. (2019). Novel nanoarchitecture cobalt-doped TiO2 and carbon nanotube arrays: Synthesis and photocurrent performance. Ceram. Int. 45(2), 2439–2445. Liu, L., Xu, T.T., Zhao, X.C., et al. (2020). Study on the disturbation of physiological characteristics in Vicia faba L. seedlings exposed to a combination of carboxylated multi-walled carbon nanotubes and cadmium. Asian J. Ecotox. 15(6), 252–261. Macwan, D.P., Dave, P.N., Chaturvedi, S. (2011). A review on nano-TiO2 sol-gel type syntheses and their applications. J. Mater. Sci. 46, 3669–3686. Mouchet, F., Landois, P., Puech, P., et al. (2010). Carbon nanotube ecotoxicity in amphibians: Assessment of multi-walled carbon nanotubes and comparison with double-walled carbon nanotubes. Nanomedicine 5(6), 963–974. Petersen, E.J., Zhang, L.W., Mattison, N.T., et al. (2011). Potential release pathways, environmental fate, and ecological risks of carbon nanotubes. Environ. Sci. Technol. 45(23), 9837–9856. Wen, S.X., Xiao, M., Li, M. (2019). Phytotoxic effects of TiO2 -NPs in two macrophytes for constructed wetlands. Fresen. Environ. Bull. 28(9), 6733–6743. Yin, J., Fan, W., Du. J., et al. (2020). The toxicity of graphene oxide affected by algal physiological characteristics: a comparative study in cyanobacteria, green algae, diatom. Environ. Pollut. 260, 113847. Yuan, Z.D., Zhang, Z.M., Wang, X.P., et al. (2017). Novel impacts of functionalized multi-walled carbon nanotubes in plants: promotion of nodulation and nitrogenase activity in the Rhizobium-legume system. Nanoscale 9(28), 9921–9937.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Application analysis of geological logging technology in oilfield exploration Yuhang Huo∗ No. 1 Geological Mud Logging Company of Daqing Exploratory Drilling Engineering Company, Daqing Oilfield Limited Company, Heilongjiang, Daqing, China

ABSTRACT: With the modern development of China’s oilfield industry, the task of oilfield exploration has increased. The progress of various exploration works provides a practical guarantee for oilfield production. With the increasing expansion of the production scale of each oilfield, the role of oilfield exploration is becoming more and more prominent. Geological logging, as a key work in exploration, contains many exploration methods. In the process of industrial expansion, each oilfield enterprise must actively apply advanced technology and equipment to do a good job of geological logging. Based on this, this paper analyzes the classification, parameters, and functions of geological logging in the field of oilfield exploration, expounds on the key points of logging work, and analyzes the application of geological logging in oilfield exploration, which plays an important guiding role in oilfield exploration and development.

1 INTRODUCTION In the field of production and living at this stage, oil and gas resources have become key resources. With the progress of many activities, the consumption of oil and gas resources is increasing day by day. In order to alleviate the imbalance between the supply and demand of oil and gas resources, various oilfield enterprises are actively exploring new development paths to improve oilfield production through the application of advanced exploration and production processes, which obtains higher economic and social benefits. The development of geological logging provides information such as rock shape and odor for oilfield operators. At this stage, the oilfield field pays more and more attention to geological logging. In order to give full play to the role of geological logging, relevant enterprises should pay attention to the selection and application of geological logging technology.

2 OVERVIEW OF GEOLOGICAL LOGGING With the development of science and technology in China, conventional core logging technology and borehole logging technology are gradually improved. In addition, new logging technology is also gradually developed and applied. Therefore, for geological logging technology, oilfield companies should also strengthen their applications, improve the efficiency of field exploration, and contribute to the development of oilfield companies in China.

∗ Corresponding Author:

34

[email protected]

DOI 10.1201/9781003318569-7

2.1 Classification In the field of oilfield exploration at the present stage, geological logging mainly focuses on direct logging and indirect logging. Among them, direct logging technology can be further divided into core logging technology and cuttings logging technology, while indirect logging technology specifically includes gas logging and fluorescence logging. However, no matter what kind of logging technology is used in oilfield exploration, it needs to be completed with the help of information technology. Information acquisition and parameter processing are the key processes in the application of geological logging technology. Only by ensuring the efficiency of information acquisition and parameter processing, can geological logging play its role in Oilfield operation and master the relevant situation of reservoir area in detail. However, in the current field of oilfield production, geological logging technology contains more and more technologies. In order to give full play to the advantages of this technology, the most appropriate geological logging technology should be selected according to the actual situation of the site. 2.2 Parameters When applying geological logging technology in the field of oilfield exploration, the following parameters shall be obtained: (1) Geology. During drilling operation, the drillability of formation and bit conditions can be obtained; under the operation of cuttings and cores, the stability conditions of formation lithology are obtained; gas logging components are very effective for the investigation of basic properties and oil and gas-bearing properties of reservoir objects. (2) Drilling fluid. Under the condition of drilling fluid logging, it specifically includes flow parameters and density. Firstly, in terms of flow parameters, it accurately and fully reflects the change of drilling fluid entering and leaving the wellhead; secondly, the density reflects the performance fluctuation of drilling fluid. Through the mastery of the information of these parameters, relevant operators can fully understand whether the formation pressure and drilling fluid performance meet the operation standards during the operation. (3) Formation pressure. Formation pressure mainly includes the ECD index, DC index, and sigma index (Zhang 2020). 2.3 Function In recent years, with the growth of the demand for oil and gas resources in the economic and social fields, various oilfield enterprises pay more and more attention to the application of geological logging technology in the production operation. Through the determination of a scientific geological logging technology scheme, the scientificity and rationality of oilfield exploration are effectively guaranteed. The role of geological logging in oilfield exploration is as follows: (1) it can help operators on the oilfield site fully understand the distribution conditions of reservoirs in the formation and provide practical data support for oilfield production through detailed exploration data; (2) According to the relevant data and information obtained from geological logging, field operators can more clearly grasp the physical properties of the reservoir and the content of oil and gas resources, so as to realize the comprehensive evaluation of the oilfield situation. Scientific exploration reduces the difficulty of subsequent exploitation and creates higher benefits for oilfield enterprises (Li 2018).

3 KEY POINTS OF GEOLOGICAL LOGGING IN OILFIELD EXPLORATION 3.1 Cuttings logging At the oilfield exploration site, if relevant operators want to master complete and accurate information in the shortest time and ensure the accuracy of oilfield location determination, they should use rock cuttings to determine the basic net content of the oilfield according to the requirements 35

Figure 1.

Histogram statistical results of porosity and permeability of well A.

of the drilling work plan. Therefore, the application of cuttings logging technology is very important in oilfield exploration. Relevant personnel on-site should use cuttings logging technology scientifically according to the field conditions of the oilfield. 3.2 Fluorescence logging Fluorescence logging is also a kind of geological logging, which is widely used in oil field exploration. This logging technology adopts a chemical element detection method in detection. In a specific application, it can accurately determine the distribution position of the oil layer under the rock stratum and other basic information through a special chemical element. Based on the particularity of fluorescence logging technology, the application effect in oilfield exploration is ideal. If it is found to be yellow in oilfield exploration, it indicates that there are oil and gas resources distributed here to a great extent; however, if it is light yellow, it reflects that the water content in the surface layer of rock debris is high, and there may be a large layer of water mixing area in the bottom layer here; if it is golden, it means that there are abundant oil reserves here. In the application of fluorescence logging technology, the difference in rock stratum depth will also lead to its final presentation effect showing different color characteristics. It is this difference that makes the positioning of the oil layer more accurate. The application of fluorescence logging technology is mainly based on the principle of fluorescence reaction, and there is a close correlation between the fluorescence reaction results and the exploration depth. Therefore, in order to ensure the accuracy and reliability of the exploration results, it is particularly necessary to properly design the exploration process (Che 2015). 3.3 Drilling time logging Drilling time logging is also frequently used in oilfield exploration. Relevant operators should record and integrate all the collected information while drilling, because these data have a wide variety and a large number. In order to realize the efficient processing of data and information, it is generally completed with the help of computer software. The geological information data curve can be obtained only with the aid of software. The application of drilling time logging technology in oilfield exploration can obtain and record the corresponding data in real-time and accurately, and use these data to guide oilfield production operations. In order to give full play to the advantages of this technology, the personnel participating in drilling time logging are generally required to have high professional quality and ability. 36

3.4 Comprehensive logging instrument In oilfield exploration, the comprehensive logging instrument mainly monitors the characteristics of formation mud gas in the drilling process through gas logging instruments. This monitoring has a real-time and whole process. The monitoring of professional instruments can effectively analyze the changes in abnormal conditions and pressure parameters in the exploration area. With the help of a comprehensive logging instrument, operators can have a clearer grasp of underground mining, quickly identify safety risks to a certain extent, and timely take effective treatment strategies to ensure the efficient operation of mining. 3.5 Drilling fluid logging Drilling fluid logging technology is highly similar to cuttings logging technology. In the process of application of this logging technology, the specific situation of the formation can be mastered in detail through the collection and analysis of corresponding information. With the assistance of drilling fluid logging technology, information on drilling fluid density and hydrocarbon gas content is obtained. Once the distribution of oil and gas reservoir is encountered in the process of drilling, the drilling fluid will change significantly in a very short time. For example, it may be accompanied by abnormal acceleration of flow rate and generation of oil flowers and bubbles (Ma 2019).

4 APPLICATION OF GEOLOGICAL LOGGING IN OILFIELD EXPLORATION 4.1 Analysis of technical problems In the application of geological logging technology in oilfield exploration, even if geological logging technology is more and more diverse, it may also face various technical problems in the process of technical application. Geological logging is highly professional. If we want to play its role in oilfield exploration, we should pay special attention to the analysis and solution of various technical problems. The technical personnel participating in geological logging should have high professional quality and be able to deal with various technical problems in the process of implementation. For example, in the application of core logging technology, it is necessary to measure the oil well core, accurately analyze the specific properties of the core through the measurement results, and then draw the corresponding analysis results into a column diagram to accurately grasp the corresponding information. 4.2 Work environment management The operating environment of the oilfield site is complex and special, which may be accompanied by a series of safety risks, especially since there are many risk factors during the implementation of geological logging. If we lack attention to safety work in the actual operation process, it may lead to serious accidents. Therefore, in the application of geological logging technology in oilfield exploration, we should pay particular attention to the implementation of safety management, always adhere to the principle of safety first, ensuring that all kinds of equipment and facilities can be in a stable and reliable operating condition. Relevant personnel should strictly abide by the corresponding operation processes and specifications to reduce the safety risks on the operation site (Zhu 2019). 4.3 Staff quality Because of the strong professionalism of geological logging, the professional quality of the staff must be guaranteed when participating in the geological logging operation of oilfield exploration. Only by ensuring the extremely high professional quality of the staff can these staff select the appropriate geological logging technology according to the specific situation of the site and follow 37

the standardization requirements of geological logging technology in the process of oilfield exploration, so as to improve the effectiveness of geological logging. Once the professional quality of staff is low, it may lead to various problems in the development of geological logging work and affect its role, and it is difficult to provide a guarantee for oilfield production operation.

5 CONCLUSION Geological logging technology contains many means. In the actual selection and planning, the methods to be used should be selected according to the actual situation. At the same time, the exploration organization should formulate a scientific-technical management process to ensure the accuracy of logging results to the greatest extent. Geological logging technology is a key technology in oilfield exploration. Although there are many types of technology, the key points needing attention under different geological logging technologies are also different. In order to give full play to the role of geological logging effectively, relevant personnel should pay particular attention to the selection of geological logging technology in practical work, comply with the requirements of standardization, and improve the comprehensive level of geological logging.

REFERENCES Che Yinglan. On the application value of geological logging in oilfield exploration [J]. Petrochemical Technology, 2015, 22(06): 203. Li Zhen. Application of geological logging technology in oilfield exploration [J]. Petrochemical Technology, 2018, 25(06): 239+175. Ma Peng. Application of geological logging in oilfield exploration [J]. China Petroleum and chemical industry standard and quality, 2019, 39(05):126–127. Zhang Lei. Application of geological logging in oilfield exploration [J]. Petrochemical Technology, 2020, 27(11):144–145. Zhu shuangpeng. Discussion on the application of geological logging technology in horizontal well logging [J]. Chemical engineering and equipment, 2019(08):190–191.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Classification and safety precautions of blasting technology Xiyong Qian Henan University of Technology, Zhengzhou, Henan Province, China

ABSTRACT: Mine blasting belongs to the application of engineering blasting technology in mining. All kinds of blasting techniques are used in mine engineering, whether in the process of tunneling, open-pit mining, or underground stope mining. This paper mainly introduces the classification of engineering blasting, the main methods used in mine blasting, several kinds of blasting technology usually used in the underground stope, and the relevant control blasting technology and basic mine blasting safety technology in detail. Blasting technology can be classified according to the form of medicine package, the charging mode, and charging space shape. Besides, workers must have learned safety precautions of blasting technology before they start working. Classification and safety precautions of blasting technology allow workers have a better understanding of their projects so that the blasting work can be safe and reliable and then their working efficiency can be enhanced.

1 INTRODUCTION Engineering blasting methods can be divided into two categories according to the shape of the charge bag, the charge way, and the charge space form. 1.1 Classification according to the form of medicine package According to the shape of the charge bag, namely, the explosive action and characteristics of the charge bag are classified. According to this method, it can be divided into four types: 1.1.1 Concentrated drug package method Theoretically speaking, the shape of the package is spherical, the initiation point starts from the center of the sphere, and the detonation wave radiates outward in the form of a spherical expansion, that is, the explosion effect is evenly distributed to the surrounding medium. However, in engineering practice, it is almost impossible to process the drug bag into this shape. Usually, the drug bag is made into a cube or rectangular shape, and the longest side of a cuboid is no more than 6 times the shortest side. At this point, the charge can be called the centralized charge, usually called the charge chamber method and the charge pot method. 1.1.2 Lengthening cartridge method – cylindrical cartridge The package is made into a long strip, which can be cylindrical or square, but in general, it is cylindrical. Once the explosive is excited and exploded, the wavefront form of the generated detonation wave is cylindrical, that is, the detonation wave formed after the explosion spreads around in the form of a cylindrical wave and acts on the surrounding medium. Bags with a length greater than 6 times the shortest edge or diameter are usually called extended bags. In the practical engineering application, the strip charge blasting method in deep hole blasting, borehole blasting, and charge chamber blasting belongs to the extended charge blasting method. DOI 10.1201/9781003318569-8

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1.1.3 Flat drug package method The blasting of this cartridge is different from the first two methods, it does not need to drill nor dig chambers, but directly lay explosives on the surface of the medium, so the explosion effect is only on the surface of the medium contact cartridge, most of the energy is lost to the air, the detonation wave generated should be regarded as a plane wave. For example, in the processing of mechanical parts, the use of a round cake-shaped charge package, blasting coated on the surface of the medium, is the processing of mechanical parts explosive processing method. However, the planar charge bag method in chamber blasting is different from this method. It is a charged plane with an equivalent concentrated charge bag or strip charge bag arranged at a certain distance. The detonation wave produced during blasting is also similar to the plane wave. 1.1.4 Shape bag method This is a particular shape of the charge used to achieve a particular explosive effect. The most widely used is the shaped explosive method, which is to process one end of the cartridge shell into conical or parabolic pits, so that the detonation wave generated by the explosive explosion gathers on its focal point or axis according to the surface of the conical or parabolic pits, forming high-energy jet and penetrating a part of the medium in contact with it. This cartridge is used militarily as an armor-piercing round to penetrate tank decks and other military targets; in practical engineering, it is used to cut metal sheets (for example, the cutting of old hulls, the demolition of steel structures buildings and structures), the secondary crushing of rock chunks and the perforation in frozen soil, etc. 1.2 According to the charging mode and charging space shape of different classification According to the different charge modes and charge space shapes, it can be divided into four blasting methods (Kusmaul 1987). 1.2.1 Medicine chamber method This is a commonly used blasting method in a large number of earthwork excavation projects. Its advantage is that the construction machinery and tools are relatively simple, not limited by geographical conditions and climate, the greater the number of projects, the higher the efficiency. Generally speaking, the medicine chamber blasting method according to the size of the powder chamber volume within the rock mass excavation, also can be divided into three kinds of methods: a big room, a small room, and bar-type powder chambers. Each room of the explosive loading capacity, small to hundreds of kilograms, big to hundreds of tons, charge blasting chamber capacity can reach thousands of tons, and China had many times one thousand tons and tons of big blast. 1.2.2 Medicine pot method In order to achieve the blasting method of loading more charge, a small amount of explosive is put into the bottom of the ordinary hole for non-blocking blasting, so that the bottom of the hole is expanded into a round pot after repeated blasting. The blasting method of the charge pot belongs to the centralized charge package, which is suitable for the blasting of medium and hard rock. It can obtain more earth and stone volume by less hole blasting under the construction condition of small engineering quantities and insufficient drilling machines and tools. At present, this blasting method is only used under individual conditions. 1.2.3 Perforation method Usually, according to the different hole diameter and hole depth, the hole depth is not less than 5m, and the hole diameter is not less than 50mm called deep hole blasting, otherwise known as shallow hole blasting and hole blasting. In terms of charge structure, it belongs to a kind of extended charge, which is the most widely used and the largest blasting method in engineering blasting. 40

1.2.4 Naked medicine bag method This is the simplest and most convenient blasting construction method. It is not necessary to drill holes, but to lay the explosive directly on the surface of the blasted object and simply cover it. This blasting method is often used to remove dangerous objects, traffic obstacles, secondary crushing of large rocks, dangerous rock treatment, and so on (Kachanov 1992). 1.3 Classification of dust

Figure 1.

Classification procedure [3].

A laboratory classifier 100MZR from Hosokawa Alpine was used for the dry classification of dust. The procedure for the classification is illustrated in Figure 1. In the first classification step, the finest dust fraction was separated from the mixture and collected in the cyclone at the outlet of the classifier as Particle Class 1. The remaining coarse fraction was used as feed material in the next classification step, where the classifier was operated at a reduced speed. Thus, the cut size diameter of the classification was shifted to coarser particle size. In this second classification step, the material was split into particle Class 2 and a new coarse fraction. This procedure was repeated twice so that the dust mixture was separated into five dust particle classes. The speed of the classifier in the four classification runs was 18000 rpm, 10000 rpm, 6000 rpm, and 3000 rpm, and the airflow through the classifier was constant at 50 m3 /h. In the first classification step, it was found that some fine dust material is lost at the cyclone outlet because the collection efficiency of the cyclone for very fine material is limited. The amount of the fine dust lost was calculated for the first classification run by a mass balance.

2 ROADWAY DRIVING AND BLASTING Roadway driving blasting includes the blasting of various underground passages such as drift, shaft, inclined shaft, patio, and tunnel. Its common characteristic is that under the condition of the single free surface, restricted by the excavation section, the blasting footage is generally only 1 ∼ 3m per time. In order to form a certain shape of tunnel section, different types of boreholes must be 41

arranged on the working surface. The specification and direction of the roadway should be strictly guaranteed, and the requirements of concentration of blasting pile and uniformity of fragmentation should be met. The utilization rate of the blasting hole should be high, the surrounding area should be smooth, and the material consumption should be less. The parameters of roadway driving include hole diameter, unit explosive consumption, hole spacing, hole depth, hole number, charge quantity, filling length, etc. (Budiansky et al. 1997). In particular, it is a blasting technology developed in the 1950s that the one-hole and one-hole blasting is used in deep hole blasting driving. Its characteristic is that the one along with the patio with drilling cavern full high drilling deep holes, blasting can be divided into several blasting, from bottom to top is presented. The rock under blasting by gravity whereabouts, gun smoke roadway discharge through deep hole leads to the upper level, the charging, stuffing, initiating such as homework at the upper-level tunnel or cavern rock drill. Compared with common tunneling methods, deep hole blasting tunneling has the advantages of high efficiency, safe operation, and good working conditions. It is suitable for vertical or steeply inclined roadway excavation such as patio, pass, and filling well. The blasting parameters of the open-hole blasting scheme mainly include a number of deep holes, sectional height, and so on (Huang et al. 1994). 3 CONTROLLED BLASTING Definition of controlled blasting: According to the engineering requirement and blasting environment, scale, object, such as specific conditions, through careful design, construction and protection, and other technical measures, strictly control and medium crushing explosion energy release process, both to achieve the expected blasting effect, and the scope of blasting, direction and must be, air shock wave and noise of the blasting seismic wave and broken objects flying hazard control within the prescribed limit, the double control of blasting effect and blasting harm is called controlled blasting. A risk analysis of blast damage to built infrastructure can be represented, for convenience, as having three levels, each level progressively requiring more useful probabilistic measures of reliability and thus resulting in more useful probabilistic measures of reliability and risk (see Figure 2) (Mark et al. 2008). These are summarized as: • Level 1: Fragility (or vulnerability) curves. • Level 2: Probability of failure conditional on the occurrence of a specific threat scenario. BRCs can be generated from this information. • Level 3: Probability of failure obtained from the aggregation of conditional risks if the relative or absolute threat probabilities are known or inferred by export opinion. 3.1 Differential blasting Millisecond blasting is a kind of blasting technology that arranges the blasting order and reasonable time difference of each hole ingeniously. Because the time interval of blasting is a millisecond, millisecond blasting is also called millisecond blasting (Xu et al. 2003). The correct application of differential blasting can reduce the bulk rate after blasting, the intensity of seismic wave and air shock wave, the flying distance of fragments, get a good blasting effect, and easy to clear the accumulation. The key to differential blasting technology is the choice of the time interval. A reasonable time difference can ensure a good blasting effect, otherwise, it will cause bad consequences, which cannot reach the design purpose, and even the explosion rejection, increase the harm of seismic waves and other accidents. The emergence of multi-stage high-precision non-electric millisecond detonators, electronic detonators, and magnetoelectric detonators provides good conditions for the wide application of this blasting technology. Differential blasting technology is widely used in open-pit and underground excavation and urban controlled blasting, and directional blasting for dam construction by large chamber blasting has also been applied. 42

Figure 2. Illustration of models and probabilistic data required for risk. analysis of blast damage to built infrastructure (Mark et al. 2008).

3.2 Extrusion blasting (ballast-blasting) Extrusion blasting (ballast blasting) refers to the blasting under the condition of covering loose rock blocks in front of the free so that the rock is further crushed by extrusion. This method is commonly used in open-pit and deep-hole underground blasting. The extrusion effect is limited by the number of blasting rows: if the number of blasting rows is large, the loose rock blocks in the front will be more and more compacted, and the gap will be smaller and smaller, so the extrusion 43

effect of deep-hole blasting in the rear row is not available. When the loose coefficient reaches 1.1, it is the limit value. If the number of blasting rows is adjusted well, it can be regarded as an effective method to reduce the bulk rate (Xiao et al. 2002). Squeeze blasting (ballast blasting) is the blasting in which the compensating space is not enough for the free fragmentation of the exploded ore. According to the way of compensation space, squeeze blasting can be divided into small compensation space squeeze blasting and loose rock squeeze blasting. Squeeze blasting compensation in a small compensation space. The volume of space accounts for only 12%–20% of the volume of the ore exploded. The mining roadway and cutting groove between ore sections to be exploded are used as compensation space. Compressional blasting of loose ore and rock mainly compacts the loose ore and rock on the mining side by the kinetic energy obtained from ore caving during blasting. This kind of blasting is also called lateral extrusion blasting. Under suitable conditions, the use of extrusion blasting (ballast-blasting) will promote the development of mining science and technology, reduce consumption and increase efficiency, and bring remarkable economic benefits to mine production and management.

3.3 Pre-split blasting and smooth blasting Pre-split blasting and smooth blasting are two kinds of blasting techniques. Smooth blasting is a blasting operation in which dense holes are arranged along the excavation boundary, uncoupled charge or low-power explosive is adopted and detonated after the main blasting area to form a smooth contour surface. Pre-splitting blasting is a blasting operation in which dense holes are arranged along the excavation boundary, uncoupled charge or low-power explosive is adopted to initiate detonation before the main blasting area, so as to form pre-cracks between the blasting area and the reserved area, so as to weaken the damage of the reserved rock mass by the main blasting and form a smooth contour (Li et al. 1998). The ultimate purpose and effect of the two blasting technologies are the same, both of them are to make the rock face smooth and stable after blasting, so as to ensure that the surrounding rock is not damaged, and the blasting mechanism of the two technologies is also very similar. The difference between them is that pre-splitting blasting is within the intact rock mass, in front of the blasting excavation blasting in advance, so along the excavation section, there is no need to keep some boundaries open a crack, and it is used to partition split the rock damage reserved by the blasting effect and to maintain some new smooth surface after the project is completed; smooth blasting is to reserve a protective layer of a certain thickness (smooth blasting layer) when blasting is close to the excavation boundary, and then intensive drilling is conducted for this protective layer. These holes are continuously detonated after blasting other holes, so as to obtain a smooth slope and contour surface after blasting (Zheng et al. 2003).

4 CONCLUSION Engineering blasting technology can be classified into different categories according to the form of medicine package and the charging mode and the charging space shape. Roadway driving blasting includes the blasting of various underground passages and the one-hole, and one-hole blasting is used in deep hole blasting driving. Controlled blasting can be divided into differential blasting: extrusion blasting, pre-split blasting, and smooth blasting. Blasting safety has been accompanied by the development of blasting technology. A successful blast must, first of all, be safe. Blasting work is often risky, but blasting technology is not a risky technology, and it must be safe and reliable, so the blasting workers of all countries attach great importance to the study of blasting safety technology. Overall grasp of various blasting technology should not only have certain mathematics, mechanics, physics, chemistry, and engineering geological knowledge, but also has certain construction technology and experience accumulation, as blasting engineering technical personnel should be 44

familiar with all kinds of physical and mechanical properties of the medium, blasting action principle, method of blasting, blasting method and blasting parameters calculation principle, construction technology, and knowledge. At the same time, it is necessary to be familiar with the rules of blasting action, such as seismic wave, air shock wave, fragmentation scattering, and destruction range, as well as the corresponding safety protection knowledge. Classification and safety precautions of blasting technology allow people who are working on blasting projects to have a better understanding of engineering blasting methods and precautions of blasting technology. It can help reduce the risk of hurt and death in blasting projects so that they can be safe and reliable. Once the safety of workers has been guaranteed, their motivation and enthusiasm will be enhanced and the work efficiency will be improved.

ACKNOWLEDGMENTS I would like to show my appreciation to my professor and teacher. As for my professor, he helped me to tackle many problems related to my major, and he gave me some directions about my paper. As for my teacher, she assisted with the techniques of writing an article and gave me some very specific advice. Without their help, I believe I could not have finished this paper so smoothly.

REFERENCES Budiansky B. and O’Connell R. J, Elastic Moduli of cracked solid, Int. J. Solids, 1997, 12:81–87. Christ of Lanzerstorfer, Michaela Kroppl, Air classification of blast furnace dust collected in a fabric filter for recycling to the sintering process, 2014, A-4600 Wels, Austria. Huang Y ET AL, Generalized Self-consistent Mechanics method for Microcracked Solids, J. Meeh. Phys. Solids, 1994, 42:1273–1291. Kachanov M., Effective Elastic properties of Crack solids, Critical Review of Some Basic Concepts, App. Mech. Review, 1992, 45(7): 304–335. Kusmaul J.S., A New Constitutive Model of Frasmeniation of Rock under Dynamic Loading, in 2nd Int. symp. On Rock Rrag By Blasting, Keystone, 1987: 412–424. Li Shou-ju, Liu Ying-xi. Analysis of crack propagation process under blasting load [J] Journal of Rock Mechanics and Engineering, 1998, 17: 888∼891. Mark G. Stewart, Michael D. Netherton, Security risks and probabilistic risk assessment of glazing subject to explosive blast loading, 93(2008): 627–638. Xiao Zheng-xue, ZHANG Zhi-cheng, GUO Xue-bin. Research on crack developing law of rock fracture controlled blasting [J] Chinese Journal of RockMechanics and Engineering, 2002, 21(4): 546–549. Xu Hong-tao, Lu Wen-bo. Study on dynamic unloading effect during the process of fragmentizing rock by blasting [J] Rock and Soil Mechanics, 2003, 24(6): 969–973. Zheng Chang-qing, PAN Jin, Lu Yun-ming, et al. Discussion on rock slipping blasting [J] Blasting, 2003, 20(3): 14–16.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Experimental study on explosion characteristics of lignite dust in coal chemical industry Lujia Tao & Shunbing Zhu Nanjing Tech University, Nanjing, China

ABSTRACT: Lignite is the main raw material in the coal chemical process. Lignite dust produced in the coal chemical process is dangerous for combustion and explosion. Therefore, the combustion and explosion characteristics of lignite dust were studied in this paper. The combustion characteristics of lignite dust were studied by TG analysis, and the effects of different heating rates on the combustion characteristics of lignite dust were analyzed. The effects of different mass concentrations and different ignition energies on the maximum explosion pressure of lignite dust were studied by using a 20 L ball explosive device. The results show that when the heating rate is 10◦ C/min, the dust mass-loss rate is the largest and the combustion rate is faster when the temperature is 512◦ C. As the heating rate increases, the maximum weight loss rate of lignite dust increases. The temperature required to achieve the maximum weight loss rate increases from 490◦ C to 566◦ C. The maximum explosive pressure of lignite dust is 150 g/m3 . Under the action of high ignition energy of pulverized coal, the danger of explosion will increase, and the accident consequences of the explosion will be more serious. When the dust concentration is 150 g/m3 , the explosion pressure is the highest, which is 0.7658 MPa. When the concentration is 300 g/m3 , the ignition energy has a more significant effect on the explosive pressure of lignite dust. 1 INTRODUCTION In recent years, with the continuous innovation of coal chemical technology, lignite as the main chemical raw material coal, will produce a large amount of dust in the process of converting coal into gas, liquid, and solid fuel and chemicals, posing a threat to production safety. Coal dust explosion accidents are frequent. The overpressure and high temperature caused by the explosion not only seriously threaten the safety of operators, but also destroy the production equipment, which has become the main culprit of the safety products in the process of the coal chemical industry. Therefore, research on the combustion and explosion characteristics of lignite dust is one of the preconditions for effective prevention and control of lignite dust explosion. A dust explosion is a deflagration phenomenon that occurs when the flammable particulate matter in the air reaches a critical point. Because the fine combustible dust is well mixed with the air, once it explodes, it is often surprisingly powerful. Dust explosions can cause personal injury and property damage. Therefore, accurately understanding the harm of coal dust explosion is the key to ensuring the safety of the coal chemical process. Despite many efforts and measures have been taken to prevent dust explosion accidents, dust explosions continue to pose a threat in different industries involving dust production. TG analysis to compare the combustion characteristics of coal under O2 /N2 and O2 /CO2 atmospheres (Yi 2014). The fraction content increased, showing obvious fluctuations. The effect of different ignition energy on the explosion behavior of pulverized coal, and compared the explosion suppression effect of two inert media, CaCO3 and Al(OH)3 , and the variation law of the explosion suppression effect of inert media with ignition energy (Guo 2017). As relatively young coal, lignite has the characteristics of high volatile content, high moisture, and low calorific value. A further understanding of the characteristics of the lignite dust clouds is 46

DOI 10.1201/9781003318569-9

of great practical significance to prevent dust explosions. By testing the characteristics of lignite dust, the evolution of its combustion characteristics and explosion pressure can be revealed, and the occurrence of dust explosion accidents can be avoided. 2 MATERIALS AND METHODS 2.1 Materials Before the lignite dust explosion experiment, the lignite dust particles were dried in a drying oven at 50◦ C for about 10 hours. The particle size distribution of dust samples was measured by a laser particle size distribution analyzer, and the results are shown in Figure 1. Table 1 summarizes the size distribution of lignite dust.

Figure 1.

Particle size distribution of lignite powder.

Table 1. Material properties of lignite powder. Particle size distribution (µm)

Specific surface area (m2 /g)

d(10)=3.896 d(50)=21.76 d(90)=72.89

0.239

As shown in Figure 2, SEM was used to observe the surface morphology of lignite dust. The particle shape of lignite dust is irregular. The particle morphology of lignite is mainly irregular plate-like and flake-like.

Figure 2.

SEM image of lignite dust.

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2.2 Experimental methods for thermal analysis instruments Thermo gravimetric analyzer commonly known as thermo balance measures the relationship between sample mass and temperature or time by placing the sample in a specific atmosphere through a temperature control program. In thermo gravimetric experiments, the measurement results are usually expressed by the TGA curve of the relationship between sample mass and temperature or time. The rate of change of sample mass is the first derivative DTG curve of the TGA curve and temperature or time. Therefore, by observing the changes in the TGA curve and DTG curve under the condition of the heating or constant temperature, the characteristics, and composition of the sample can be inferred. The experimental device is shown in Figure 3.

Figure 3.

Synchronous thermal analyzer.

2.3 Experimental methods for 20 L spherical explosion container The explosion severity parameters of lignite dust were tested in a standard 20 L test vessel. The components of the experimental setup are shown in Figure 4. Before the explosion experiment, the pre-weighed lignite dust was put into a 0.6 L dust collection container. Then, the safety-sealed explosion container was evacuated to −0.6 bar, the dispersion air pressure of the dust collection container was set to 20 bar, and the lignite dust was dispersed into a 20-liter container through a dispersion valve. After injecting lignite dust through the nozzle, after a delay of 60 milliseconds, the suspended dust is ignited by a centrally mounted chemical igniter, resulting in a uniform dust cloud. Finally, the explosion severity parameters of this experiment can be automatically obtained by analyzing the pressure-time curve.

Figure 4.

20 L spherical explosion container.

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3 RESULTS AND DISCUSSIONS 3.1 TG analysis of lignite dust In order to determine the combustion mechanism of lignite dust, a TG analysis experiment was carried out. It is found that the release of volatiles is the key characteristic of the homogenous combustion mechanism and can be used as the criterion to distinguish the two different combustion mechanisms (Du 2017). The samples to be tested were heated from 30◦ C to 900◦ C at heating rates of 5◦ C/min, 10◦ C/min, and 20◦ C/min in air atmospheres. The spontaneous combustion oxidation process of lignite dust was studied at a heating rate of 10◦ C/min. It can be seen from Figure 5. that at a heating rate of 10◦ C/min, the pulverized coal particles mainly undergo four stages. The first stage of pulverized coal particles is from 30◦ C to 135◦ C. In this stage, due to the low temperature, reactions such as water evaporation and gas desorption mainly occur in this stage, and the quality of pulverized coal decreases slowly. From 135◦ C, the strength of the adsorption reaction between dust and oxygen gradually increased, and the quality of dust showed a trend of slow increase. When the lignite dust reaches a dynamic equilibrium between oxidation reaction and oxygen absorption, the mass of pulverized coal no longer increases and reaches the maximum value at 283◦ C. After 283◦ C, with the increase in temperature, the coal oxidation reaction is gradually enhanced. At this stage, the pyrolysis and combustion reaction of pulverized coal mainly occurs, which will release a large amount of heat and gas products. The quality of pulverized coal gradually decreases at this stage. After a period of combustion of the pulverized coal, the combustible substances are completely consumed in the pyrolysis stage until 694◦ C, resulting in a stable quality of the pulverized coal, and the residual amount is about 1%. The temperature T at the maximum point of the DTG curve is 512◦ C, where the mass loss rate of dust reaches the maximum value, and the burning rate of dust is the fastest. In the whole combustion process, the quantity and temperature of combustibles are the key factors affecting the reaction process. When the temperature is less than T, the temperature is the main factor affecting the coal oxidation reaction. When the temperature exceeds T, the previous dust is consumed in large quantities, so the amount of combustibles becomes the main factor affecting the combustion process of lignite dust. After the temperature T, the combustion rate of lignite dust gradually decreases until the combustibles are burnt out. Figure 5 shows the TG and DTG graphs of lignite dust in an air atmosphere with a heating rate of 5◦ C/min, 10◦ C/min, and 20◦ C/min. In the air atmosphere, the TG and DTG curves of lignite dust have some differences under different heating rates, which indicates that the heating rate has a certain influence on the weight loss of lignite dust. It can be seen from the TG curve that with the increase in the heating rate, the initial temperature of the pyrolysis of the lignite dust will be higher, and the increase of the heating rate will shorten the oxidation time of the lignite dust, and the dust will not be completely oxidized. The time from oxidation to the start of combustion becomes longer,

Figure 5. TG and DTG diagrams of pulverized coal in an air atmosphere at different heating rates.

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which affects the entire combustion process. The heating rate is 5◦ C/min, 10◦ C/min, 20◦ C/min The corresponding maximum weight loss rate temperatures are 490◦ C, 513◦ C, and 566◦ C, respectively. As the heating rate increases, the peak value of the DTG curve shifts backward. That is to say, the faster the heating rate is, the more easily lignite dust will ignite. 3.2 Effects of mass concentration and ignition energy on explosive characteristics of lignite dust The chemical ignition heads in the lignite dust explosion test experiment were 2, 5, and 10 kJ, respectively. The chemical ignition head used in the experiment is composed of zirconium powder, barium nitrate, and barium peroxide, and the mass ratio is 4:3:3 (Yang 2019). The effect of lignite dust mass concentration on explosion pressure under different ignition energies is shown in Figure 6.

Figure 6.

Influence of lignite dust concentration on explosion pressure under different ignition energies.

It can be seen from Figure 6 that with the continuous increase of dust concentration, when the dust concentration is 150 g/m3 , the explosion pressure is the highest, which is 0.7658 MPa. With the increase of ignition energy, the surface temperature of pulverized coal particles increases, and the explosion pressure of pulverized coal increases sharply. The gas-phase ignition mechanism of dust believes that the explosion pressure depends on the combustible volatiles released by the dust particles, and the ignition energy plays a role in the volatility of pulverized coal. The more volatile matter in the unit volume, the coal dust particles react with the air in a short time, the faster the reaction, the more the number of particles participating in the reaction, the shorter the entire explosion time, and the more heat lost through heat conduction and heat radiation. After that, the number of particles per unit volume increases, and the concentration of pulverized coal that does not participate in the explosion reaction increases, so the oxygen concentration decreases, and the explosion pressure of lignite dust begins to drop. It can be seen from Figure 7 that at the concentration of 300 g/m3 , the explosion pressure of pulverized coal is more significantly affected by the ignition energy than at the concentration of 50 g/m3 . Therefore, it can be considered that under the action of high ignition energy of pulverized

Figure 7.

Effect of ignition energy on explosive characteristics of lignite dust.

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coal, the danger of explosion will increase, and the accident consequences of the explosion will be more serious. Chemical ignition induces a certain level of turbulence, and the heat released by the ignition tip increases the pressure within the vessel, which is known as an ignition boost (Hu 2018).

4 CONCLUSION In this paper, TG analysis is adopted to study the combustion characteristics, and a 20L ball explosive device is adopted to study the explosion characteristics. The main conclusions can be summarized as follows: (1) When the heating rate is 10◦ C/min, the lignite dust quality does not change at 694◦ C. At 512◦ C, the lignite dust mass-loss rate is the largest and the combustion rate is faster. (2) The faster the heating rate is, the more easily lignite dust will ignite. As the heating rate increases, the maximum weight loss rate of lignite dust increases. The temperature required to achieve the maximum weight loss rate increases from 490◦ C to 566◦ C. (3) When the dust concentration is 150 g/m3 , the explosion pressure is the highest, which is 0.7658 MPa. When the concentration is 300 g/m3 , the ignition energy has a more significant effect on the explosive pressure of lignite dust. Under the action of high ignition energy of lignite dust, the danger of explosion will increase, and the accident consequences of the explosion will be more serious. In future work, the effect of inert powder on lignite dust should be studied.

REFERENCES Baojun Yi & Liqi Zhang (2014). Effect of the particle size on combustion characteristics of pulverized coal in an O2 /CO2 atmosphere. Fuel Process Technology. 128(10): 17–27. Bing Du & Weixing Huang (2014). Comparative study of explosion processes controlled by homogeneous and heterogeneous combustion mechanisms. Journal of Loss Prevention in the Process Industries. 30: 155–163. Jie Yang & Yuan Yu (2019). Inerting effects of ammonium polyphosphate on explosion characteristics of polypropylene dust. Process Safety and Environmental Protection. 130: 221–230. Jing Guo & Qing Wang (2017). Experimental studies on explosion characteristics of coal dust in confined space. Blasting. 34(3): 31–36. Weixi Hu & Wang Tao (2018). Effect of ignition energy on the lower limit concentration of dust explosion. Industrial Safety and Environmental Protection. 44(10): 13–14+47.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Application of fuzzy evaluation method in mixed combustion of inferior coal in Utility Boiler application in optimization Hongwei Liu Inner Mongolia Power (Group) Co., Ltd., Inner Mongolia Power Research Institute Branch, Hohhot, Inner Mongolia

ABSTRACT: In the actual boiler combustion optimization, the best operation mode is to improve boiler efficiency, reduce NOx emission, reduce auxiliary power consumption and reduce desuperheating water consumption. In particular, there are contradictions among various index factors, so it is difficult to establish a mathematical model to take into account these indexes at the same time. Two kinds of multi-objective decision-making methods in fuzzy mathematics theory are introduced. Based on the test data of a power plant burning inferior coal in different proportions, the application of two kinds of multi-objective decision-making methods in the decision-making of burning inferior coal is expounded, and the determination method of index weight is explained. Based on the theory of fuzzy mathematics, the method of weighted relative deviation minimum and the method of quantitative index comprehensive decision-making are proposed to make multiobjective decision-making. The results show that the multi-objective decision-making method can evaluate the blending data of inferior coal according to the factor index weight. The results of the two methods are the same. Under the currently selected index weight, the scheme of blending 60% of inferior coal has a good blending effect. The evaluation method provided a new idea for the accurate evaluation of the blending effect of inferior coal.

1 INTRODUCTION Coal-fired cost is the main source of operating cost of thermal power generation enterprises. Considering the profit space, most power generation enterprises cannot completely burn the design coal. In particular, there are contradictions among various index factors, so it is difficult to establish a mathematical model to take into account these indexes at the same time. Therefore, it is of practical significance to determine the best blending scheme of inferior coal by using the multi-objective decision-making method in fuzzy mathematics theory. The boiler of a power plant #2 unit in Inner Mongolia is manufactured by Shanghai Boiler Works Co., Ltd. The type is supercritical parameter composite sliding pressure spiral tube coil once through pulverized coal boiler, single furnace bore, four corner tangential circles, primary intermediate reheat, balanced ventilation, solid slag removal, all-steel frame suspension structure, and tight closure
Type coal-fired boiler. The steam temperature adopts the coal/water ratio as the main steam temperature regulation means, and cooperates with the secondary spray desuperheating as the fine regulation of the main steam temperature. The spray desuperheating is arranged at the left and right points of each stage to eliminate the left and right heat absorption and steam temperature deviation of Superheaters at all levels. The temperature regulation of the reheater is mainly based on the swing temperature regulation of the burner up and down, and the emergency water spray device installed on the inlet pipe of the low-temperature reheater is used for auxiliary temperature regulation. 52

DOI 10.1201/9781003318569-10

2 FUZZY MATHEMATICS MULTI-OBJECTIVE DECISION THEORY When evaluating the advantages and disadvantages of a scheme in engineering practice, due to the contradictory characteristics of various indexes in the scheme, a single index cannot comprehensively measure the advantages and disadvantages of various schemes. Therefore, seeking a satisfactory multi-objective scheme under certain constraints is a problem to be solved in multiobjective decision-making. Through the theory of fuzzy mathematics, the target elements in the scheme are transformed into relative membership degrees, and then the scheme set is sorted according to a certain weight. After comprehensive weighing, the optimal scheme in the scheme set can be selected (Chen 2013,2008). 2.1 Weighted relative deviation minimum method It is assumed that the scheme set to be evaluated is U = {option 1, option 2,…, option m,}= {u1,u2,…um}; Scheme m contains n index factors, and the set of factors and indicators contained in all schemes is V = { f1 , f2 , · · · fn }; The i-th index factor of the j-th scheme is recorded as fij , and the N-Factor index composition matrix of the m-th scheme is F, ⎞ ⎛ f11 f12 · · · f1m ⎜ f21 f22 · · · f2m ⎟ ⎟ ⎜ (1) F =⎜ . .. .. .. ⎟ ; ⎝ .. . . . ⎠ fn1 fn2 · · · fnm Define the relative deviation of indicators δij ,  0   f − fij  i δij = i = 1, 2, . . . , n; j = 1, 2, . . . , m; (2) fi max − fi min fi max = max{ fi1 , fi2 , . . . , fim } is the maximum value of the i-th index element of M schemes; fi min = min{ fi1 , fi2 , · · · , fim } is the minimum value of the i-th index element of M schemes; The positive indicator refers to the indicator that the larger the indicator value is, the better the scheme is, and the negative indicator refers to the indicator that the smaller the indicator value is, the better the scheme is. The relative deviation value constitutes a relative deviation matrix  between each factor and the optimal factor; ⎞ ⎛ δ11 δ12 · · · δ1m ⎜ δ21 δ22 · · · δ2m ⎟ ⎟ ⎜ (3) =⎜ . .. .. .. ⎟ ; ⎝ .. . . . ⎠ δn1 δn2 · · · δnm Among them is the best index, and the weight coefficient ai of each influencing factor is evaluated by experts, and the fuzzy subset A is determined according to the importance of each factor A = ( a1 , a2 , · · · an ) ; The weighted relative deviation the index vector ui of each scheme factor and  distance between the standard value vector f 0 = f10 , f20 , · · · fn0 of all indexes of all schemes is calculated to obtain the weighted relative deviation distance dj between all index elements of the j scheme and the standard value vector f 0 .

 n   1 0 (ai · δij )2 j = 1,2, . . . ,m (4) d j = dj u j , f = a i=1 a=

n i=1

n

ai

, is the average of N weighted values. 53

 The standard value vector f 0 = f10 , f20 , · · · fn0 is the most ideal scheme; among all m schemes, the scheme with the smallest relative deviation distance between n elements and n elements of the optimal scheme f 0 is the relatively optimal scheme, di = min (dj ) (1 ≤ j ≤ m, 1 ≤ i ≤ n) that is ui , which is the optimal scheme at that time. 2.2 Quantitative index comprehensive decision method Order rij = 0.1 + (fimax − fij )/d, when fi is a negative indicator; rij = 0.1 + (fij − fimin )/d, when fi is a positive indicator; −fi min ; rij is the evaluation value of the i-th index in the j-th scheme, and the N evaluation d = fi max 1−0.1 values of M schemes form the evaluation fuzzy matrix R. ⎛ ⎞ r11 r12 · · · r1m ⎜ r21 r22 · · · r2m ⎟ ⎜ ⎟ R=⎜ . . . . ⎟ (5) ⎝ .. .. .. .. ⎠ rn1 rn2 · · · rnm The weighted average model is used to evaluate each scheme, A = (a1 , a2 , a3 , a4 , a5 ) ;

(6)

The weighted average model M (•, +) is used for the evaluation of programmes. According to the principle of maximum membership degree M (•, +), that is bj , the maximum value is the optimal scheme. B = A · R = (b1 , b2 , . . . , bm ) , bj =

n

ai rij , j = 1, 2, . . . , m◦ bj = max (bj ), j = 1, 2, . . . , m◦

(7)

i=1

2.3 Determination method of factor index weight vector 2.3.1 Delphi method This is the most commonly used method. According to the knowledge, wisdom, experience, information, and values of several experts, it is an investigation method to analyze, judge, weigh and give corresponding weights to the proposed evaluation indicators. Generally, after multiple anonymous surveys, based on the comparison of expert opinions, the expert opinions are processed to test the consistency of expert opinions and obtain the weight vector of each index (Wang Jing 2001). 2.3.2 Weight determination method of analytic hierarchy process The analytic hierarchy process forms a complex evaluated system into an orderly hierarchical structure represented by evaluation factors according to its internal logical relationship and compares the indicators of the same layer and domain by using experts’ knowledge, wisdom, experience, information, and values. 2.3.3 Entropy method In information theory, entropy is a measure of uncertainty. The greater the amount of information, the smaller the uncertainty and the smaller the entropy; the smaller the amount of information, the greater the uncertainty and the greater the entropy. According to the characteristics of entropy, the randomness and disorder degree of an event can be judged by calculating entropy, and the dispersion degree of an index can also be judged by entropy. The greater the dispersion degree of the index, the greater the impact (weight) of the index on the comprehensive evaluation, and the smaller the entropy. 54

In this paper, the weight index vector is obtained by the entropy method. Among the five index factors, the mixed coal price pair is directly related to the production cost, and the index weight is slightly larger. The desuperheating water volume of the reheater has little impact on the scheme, and the index weight is slightly small. A = (a1 , a2 , a3 , a4 , a5 ) = (0.2, 0.3, 0.1, 0.2, 0.2) ;

(8)

3 EXAMPLE CALCULATION According to the analysis of the above principles, the advantages and disadvantages of different proportions of inferior coal are determined, and the proportions of inferior coal are U = {option1, option2, option3, option4} = {0,40%,60%.80%}. See Table 1 for the test results of different mixed combustion proportions of inferior coal. The boiler efficiency is calculated according to the gb10184-2015 specification for the performance test of utility boilers. The mixed coal price is obtained based on the weighted average of the blending proportion and the single coal price. The desuperheating water volume of the reheater affects the operation economy of the unit, which is obtained by adding it on both sides of the operation screen. NOx concentration is the average value on both sides of the SCR device inlet (converted to 6% reference oxygen content). The power consumption of main auxiliary machines includes the power consumption of two induced draft fans, primary air fans, forced draft fans, and coal mills (Li 2018). Table 1. Test results of different mixed combustion proportions of inferior coal. Mixed Mixed Mixed Mixed combustion of combustion of combustion of combustion of inferior coal 0 inferior coal 40% inferior coal 60% inferior coal 80%

Boiler efficiency (%) Mixed coal price (yuan/ton) Desuperheating water volume of reheater (T/h) NOx concentration (mg/Nm3 ) Power consumption of main auxiliary equipment (kW)

Option 1

Option 2

Option 3

Option 4

93.76

93.04

92.67

92.17

398

387.2

381.8

376.4

14.89

10.14

14.76

17.64

293.5

341

255

268.5

8674

8806

8912

9248

3.1 Weighted relative deviation minimum method Factor index matrix F of each scheme, ⎛

⎞ 93.76 93.04 92.67 92.17 ⎜ 398 387.2 381.8 376.4 ⎟ ⎜ ⎟ F = ⎜ 14.89 10.41 14.71 17.64 ⎟ ⎝ 293.5 341 255 268.5 ⎠ 8674 8806 8912 9248 55

(9)

The weighted relative deviation distance minimization method is used for decision-making. The factor index matrix F of each scheme shows that the standard value vector of each factor index is f 0 . f 0 = (93.76, 376.4, 10.14, 255, 8674) ; from δij =

 0  f − fij  i

fi max − fi min

(10)

i = 1, 2, · · · , n; j = 1, 2, · · · , m;

(11)

⎞ 0.45 0.68 1 0.5 0.25 0 ⎟ ⎟ 0 0.616 1 ⎟ 1 0 0.16 ⎠ 0.23 0.41 1

(12)

The relative deviation fuzzy matrix is : ⎛

0 ⎜ 1 ⎜  = ⎜ 0.63 ⎝ 0.45 0

According to the weighted relative deviation distance 

dj = dj uj , f

0

 n

1 = (ai · δij )2 j = 1,2, · · · ,m; a i=1

dj = (1.60, 1.35, 0.94, 1.51) j = 1, 2, 3 ,4;

(13)

According to the relative deviation minimum method, the scheme with the smallest weighted relative deviation distance between the four schemes and the most ideal scheme can be determined as the most ideal scheme, in which the value of dj = 0.94 is the smallest, and scheme 3 is the best when the mixed combustion proportion of inferior coal is 60%. 3.2 Calculation of quantitative index comprehensive decision method Using the quantitative index comprehensive decision-making method for evaluation, the evaluation fuzzy matrix can be calculated as: ⎛

1 0.59 ⎜ 0.1 0.55 ⎜ R = ⎜ 0.43 1.00 ⎝ 0.60 0.1 1 0.79

⎞ 0.38 0.1 0.77 1 ⎟ ⎟ 0.45 0.1 ⎟ 1 0.86 ⎠ 0.63 0.1

(14)

The weighted average model is used to evaluate each scheme M (•, +), A = (a1 , a2 , a3 , a4 , a5 ) = (0.2, 0.3, 0.1, 0.2, 0.2) ;

(15)

Evaluation of programmes, B = A · R = (b1 , b2 , · · · , bm ) ;

(16)

B = A · R = (0.59, 0.56, 0.68, 0.52) ;

(17)

It can be seen that the middle value is the largest, and scheme 3 is the best according to the principle of maximum membership. The result is the same as that calculated by the weighted relative deviation distance minimum method (Zhang 2019). 56

4 CONCLUSION In this paper, the weighted relative deviation minimum method and quantitative index comprehensive decision method are adopted to study in mixed combustion of inferior coal in Utility Boiler application in optimization. The main conclusions can be summarized as follows: (1) According to the test data of mixed combustion of inferior coal in different proportions of the boiler, the fuzzy mathematical theory is used for modeling, and the weighted relative deviation minimum method and quantitative index comprehensive decision-making method are used for calculation respectively. The results obtained by the two calculation methods are the same and verified each other. The calculation results show that under the condition of the currently determined index weight, it is the comprehensive and relatively optimal scheme when the proportion of inferior coal is 60%. (2) For the first time, the fuzzy mathematics theory is applied to the traditional mixed combustion effect evaluation of inferior coal in power plant boilers, which provides a new means and method for the research of multi-objective fuzzy evaluation decision-making, which can effectively guide the mixed combustion decision-making of power plants, and has important practical significance and guiding value. (3) Since the index weights and factors directly affect the evaluation results, the index factors and index weights proposed in this paper are only for reference. Power generation enterprises can change the index factors and index weight coefficients according to their own reality, and use the above two methods to obtain the target decision results that meet the actual situation on site.

ACKNOWLEDGMENT Fund Project: 2021 self-raised science and technology project of Inner Mongolia Electric Power Research Institute branch of Inner Mongolia electric power (Group) Co., Ltd.

REFERENCES Chen Gang (2013) Coal blending and economic operation of a utility boiler. Beijing: China Electric Power Press, 177–181. Chen Gang (2008) The application of fuzzy mathematics in the evaluation of boiler coal blending scheme. Power engineering, 6:856–858. Li Haoyu (2018) Technology of deep mixing and burning of inferior coal in 600MW unit boilers. Thermal power generation, 7: 99–104. Wang Jing (2001) Comparison of several methods for determining weight index vector in a comprehensive evaluation. Journal of Hebei University of Technology, 6: 52–55. Xianen Zhang (2019) Application of fuzzy comprehensive evaluation method in the optimization of coal blending scheme in power plant. Thermal power generation,10:117–119.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Research spot and development status of phase transfer catalysis M.X. Zhang & H. Huang School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo, Zhejiang, P.R. China

ABSTRACT: Based on Bibliometrics and CiteSpace visualization technology, taking 2632 relevant literature from 1992 to 2021 as the analysis object, this paper draws the knowledge map of phase transfer catalysis abroad, and summarizes the development of phase transfer catalysis in recent 30 years. Three research hotspots of synthesis, catalysis, and polyethylene glycol were excavated. It reveals that 1995–2008 is a hot research period in this field.

1 INTRODUCTION Phase transfer catalyst (PTC) is one of the most important catalytic technologies in the industrial field. Compared with the traditional synthesis methods, PTC has the advantages of a fast reaction rate, high yield, and convenient product treatment. It is an innovation of organic synthesis methods such as nucleophilic substitution, nucleophilic addition, oxidation, and reduction. Therefore, the application and development of phase transfer catalysts are very active at present. Quite a few scholars have carried out an army of research on this, and show the trend of multi-disciplinary common development. However, there is no systematic combination of phase transfer catalysis, review and summary of relevant literature, and the academic picture of phase transfer catalysis technology is not clear. Based on this, this paper attempts to use the biometric method to outline the basic overview of the research field from a macro perspective, so as to provide a coordinated reference for the follow-up academic research and practical promotion of phase transfer catalysis. 2 DATA SOURCES AND RESEARCH METHODS Based on CNKI database, the author sets the search conditions as follows: ((subject% = ‘phase transfer’ or title% = ‘phase transfer’) and (subject% = ‘catalysis’ or title% = ‘catalysis’)) and (publication time between (‘January 1, 1992’, ‘December 31, 2021’), search scope: Journal. In order to ensure the reliability and preciseness of the article, literature irrelevant to the subject and repeated literature were manually eliminated, and 2632 relevant literature materials were obtained. Bibliometrics refers to the use of mathematical and statistical methods to analyze the structure, characteristics, and laws of a field, and understand the current situation and development trend of the field as a whole. As a fresh development of bibliometrics, the knowledge atlas integrates interdisciplinary fields. In this paper, the information visualization software CiteSpace developed by Professor Chen Meichao of Drexel University in the United States is used as the research tool to sort out the current situation, hot topics, and development trend of phase transfer catalysis in China. 3 RESULT 3.1 Document quantity analysis The number of papers published is one of the important indicators of bibliometric analysis. It can not only reflect the output capacity of scientific research but also reveal and predict the development trend of this research field. Phase transfer catalysis technology should be the research work done 58

DOI 10.1201/9781003318569-11

by Polish scientist makosza and his collaborators in 1965. The scope of literature selected in this paper is from 1992 to 2021. After nearly 30 years of development, the number of literature in 1992 has been 89. Afterward, it entered the stage of rapid development. The annual number of articles issued from 1995 to 2008 exceeded 100, of which 131 reached their peak in 2000. Since another small peak in 2010, the number of documents issued has shown a downward trend and gradually transitioned to a stable development stage.

Figure 1.

Broken line chart of documents issued on the theme of phase transfer catalysis from 1992 to 2021.

3.2 Keyword analysis CiteSpace provides a way to combine keywords and terms to explore topics of common concern to scholars in a certain field. This means that the research hot spots or focus topics in a certain period of time can be reflected by high-frequency keywords. Figure 2 shows the results of keyword visual analysis in the HowNet database from 1992 to 2021, including 703 nodes, 1292 connections, and a density of 0.0052. It can be seen from the figure that the research hotspots in the recent 30 years are keywords with high frequency: synthesis, polyethylene glycol, and catalyst.

Figure 2.

Co-occurrence of keywords of phase transfer catalysis from 1992 to 1021.

3.3 Analysis of cooperation network of authors and institutions The cooperative network map of authors and institutions can reflect the situation of academic cooperation and the development of the research network. It can be seen from Figure 3 that the authors and institutions related to phase transfer catalysis have formed a preliminary cooperation network, and there are three main research teams, of which the team of Central South University represented by Li Xiaoru ranks first. 59

Figure 3.

Co-occurrence of authors and institutions related to phase transfer catalysis from 1992 to 2021.

3.4 Analysis of highly cited literature Through statistical analysis of the cited frequency of all sample documents, it is found that the literature information of the top ten cited frequencies is shown in Table 1. The most is progress in the research of supercritical fluid technology published by Xiao Jianping on progress in chemistry in 2001, which has been cited 117 times. Among the ten highly cited literature, except one is about reaction mechanism, the rest are related to a chemical reaction, which also confirms that phase transfer catalysis technology is mainly used in the field of the chemical industry in the previous keyword analysis. Table 1. Literature statistics of the top ten cited frequencies. Title Progress in Research of Supercritical Fluid Technology A New “Green” Route to the Synthesis of Adipic Acid Studies on the Synthesis and Biological Activity of N-Aryl- N’-(5-Aryl-2-Furoyl) Thiourea Derivative Clean Synthesis of Adipic Acid Direct Oxidation of Cyclohexene to Adipic Acid with Hydrogen Peroxide Catalyzed by Phosphotungstic Acid The Development of Phase Transfer Catalyst in Organic Synthesis Catalytic Oxidation of Cyclohexene to Adipic Acid over Heteropolyacids Studies on Mechanism andApplication of the Phase Transfer Catalytic Reaction Effects of Solvents and Quaternary Ammonium Ions in Heteropolyoxotungstates on Reaction-Controlled Phase Transfer Catalysis for Cyclohexene Epoxidation Studies on Desulfurization from Cracking of Gasoline Catalyzed by Phase Transfer Catalyst

Journal name

Year

Number of references

Progress in Chemistry

2001

117

Chemical Journal of Chinese Universities Chemical Journal of Chinese Universities

2000

101

1992

100

Chemistry Chinese Journal of Applied Chemistry

2001 2003

94 92

Journal of Hebei University of Technology Applied Chemistry

2001

79

2003

70

Lanzhou Railway College

2002

67

Journal of catalysis

2002

66

Chemical Journal of Chinese Universities

2006

63

60

4 CONCLUSION Taking phase transfer catalysis as the theme, taking the relevant papers in the China HowNet database from January 1992 to December 2021 as the research object, the scientific knowledge spectrum is drawn and analyzed by using CiteSpace visual analysis software, and the following conclusions and suggestions are drawn. (1) Since 1992, the research on phase transfer catalysis in China has gone through three development stages: first, it developed rapidly from 1995 to 2008, then decreased gradually, and finally transitioned to today’s stable development stage. From the visualization results of keywords and highly cited literature, the research in this field focuses on material synthesis and reaction catalysis in the chemical industry. Under the general trend of multi-disciplinary integration, the concept and technology of phase transfer catalysis should be applied to more fields in future research. (2) From the visual map of the authors and research institutions, it can be found that China has initially formed a cooperative network of authors and institutions in phase transfer catalysis research in recent three decades. Generally speaking, phase transfer catalysis technology has changed from backward to mature, but there is still a gap with developed countries, which requires the joint efforts of more scholars.

ACKNOWLEDGMENTS The authors wish to acknowledge financial support from the Ningbo Natural Science Foundation (2021J148) and the Student Innovation and Entrepreneurship Training Program of China (202111058011).

REFERENCES Chai, L. Q. & W. K. Dong (2002). Mechanism and application of phase transfer catalytic reaction. J. L. Z. Rai. Uni. 21, 89–91. Feng, R. (2021). Econometric Analysis on the progress and trend of tumor screening in China in recent ten years. J. Med. Inf. 34, 30–35. Li, J. & C. M. Chen (2016). CiteSpace: Scientific text mining and visualization. Beijing. Capital University of economics and trade press. pp, 156–170. Lu, T. (2020). Research hotspot and evolutionary approach of elderly care – bibliometric analysis based on CNKI. J. Soc. Welf. (Theo. Edi.) 09, 15–26. Zhang, Y. (2020). Analysis of the evolution path, hot spots, and trend of reading promotion research in colleges and universities in China. J. Lib. Wor. Rese. 08, 87–97.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Productivity test analysis of tight sandstone gas wells in Shenfu block, Ordos Basin Ke Zhang COSL-EXPRO Testing Services (Tianjin) Co., Ltd., Tianjin, China

Zhaoyuan Cheng∗ College of Petroleum Engineering, Xi’an Shiyou University, Xi’an Shaanxi, China

Hanlie Cheng COSL-EXPRO Testing Services (Tianjin) Co., Ltd., Tianjin, China

Minghao Wang China United Coalbed Methane Company, Shenmu Shaanxi, China

Qiang Qin COSL-EXPRO Testing Services (Tianjin) Co., Ltd., Tianjin, China

ABSTRACT: The evaluation of tight gas production capacity is very important for the gas well later production. The one-point method empirical formula for calculating the flow without resistance is widely used as a simple method for calculating the flow without resistance. The three types of production capacity well testing at present include back pressure well testing, isochronous well testing, and modified isochronous well testing, among which modified isochronous well testing is more suitable for tight sandstone gas reservoirs. In order to carry out the unobstructed flow of gas well in tight sandstone gas reservoir of Shenfu Block in Ordos Basin, two well correction isochronous tests were carried out. Based on the theoretical study, field test, and system analysis, the well test and interpretation method adapted to Shenfu Block was analyzed. The study shows that the additional pressure recovery test after the conventional modified equal-time well test can more accurately evaluate gas well capacity, and provide a reliable dynamic basis for gas field exploration and development.

1 INTRODUCTION The flow rate without resistance refers to the limited production of a gas well, which is generally defined as the flow pressure at the bottom of the well—the gas well production when the surface pressure on the gas layer level is reduced to 0, or when the absolute pressure is reduced to atmospheric pressure (1 atm) (Lea 2004). Obviously, because of the existence of wellbore friction, the conditions set cannot be achieved on the site. At present, the gas well non-resistance flow measured by the oil and natural gas industry standard refers to the gas well just put into production the non-resistance flow calculated, it is the gas well’s “initial non-resistance flow” (Shan 1992). According to the usual method of gas field development scheme design, the design yield of a gas well is 1/4 ∼ 1/5 of the unimpeded flow rate. Shenfu Block is a typical tight sandstone gas reservoir with low permeability, low saturation, and low porosity (Coleman 1991). The life cycle of the single well is short, and the rate of production ∗ Corresponding Author:

62

[email protected]

DOI 10.1201/9781003318569-12

capacity decline is fast. It is very important for the later development of gas wells (Wattenbarger 1969) to accurately evaluate the gas well production capacity. The current experience of tight gas development in the Ordos Basin shows that the modified equal-time trial wells are suitable for the gas well production capacity evaluation. The production capacity test of two wells in Langanbao of Shenfu Block was carried out, and some results and understandings were obtained (Swift 1962). It has positive significance for the later gas well production capacity evaluation.

2 RELATED RESEARCH In 1959, Katz et al. proposed a modified isochronous well test, which was developed on the basis of the isochronous well test: The modified isochronous well is composed of n (n ≥ 3) isochronous switch wells and a continuation period (Carlson 1991). The n isochronous switch wells are unstable flow to determine the coefficient of gas well capacity equation B. The continuation period requires flow to reach stability, which is used to determine the coefficient A of the well capacity equation. The test curve is shown in Figure 1.

Figure 1.

Sequence diagram of yield and pressure of corrected isochronous well test.

For a homogeneous gas reservoir gas well, when the wellbore reservoir effect disappears, its bottom pressure dynamic is reflected in Eq. 1, Eq. 2, Eq. 3: p2R − p2wf = Aqg + Bqg2 A=

29.22µg ZT Kh

 lg

0.472re S + rw 2.302

(1)  (2)

12.69µg ZT ·D (3) Kh In formula: p is the bottom flow pressure, MPa; P is formation pressure, MPa; K is reservoir permeability, mD; H is the layer thickness, m; q is the yield of the test section, 10m/d; D is the non-Darcy flow coefficient (10 m/d); S is the mechanical skin coefficient, no dimensional; µ is the formation gas viscosity, mPa·s; Z is the natural gas compression factor, m/m; r is the supply radius, m; r is the conversion radius of the bottom of the well, m; T is formation temperature, K. B=

63

3 WELL TESTING THEORY AND METHOD (1) Testing process At present, the block is in the exploration stage, the number of wells is less, select SM-X, SM-Y wells as the correction isochronous well test wells. The production characteristics of gas wells at all stages of production are considered in the following test scheme and process. Test scenario: Well pressure recovery (formation pressure recovery stability)+3∼4 isochronous switch well sections+1 extended production section+well pressure recovery (formation pressure recovery stability). Test process: High precision storage pressure gauge for steel wire suspension (Kamath 2003). (2) Design of test scheme The main factors that affect the results of the modified isochronous well test are isochronous interval, yield sequence, and extended production time. In order to ensure the effective implementation of correction isochronous well test, scientific and reasonable design is very important. In the practical application, we have carried out thorough research on each link of the well test design, perfecting and developing the original design method (Cellino 1999). 1) Determination of different test intervals The coefficient B of the equation of production is increasing with time due to the influence of the wellbore reservoir effect in the initial stage of well opening. Equal time interval has a significant impact on the binomial capacity equation coefficient B. The short equal time interval results in a smaller capacity equation coefficient B, leading to the final calculation of the gas well absolute flow being relatively large; on the other hand, if the design is longer, a reliable coefficient B can be obtained, but the test time and cost are increased, the production capacity of the tight gas is attenuated, and the obtained flow without resistance can not reflect the initial production capacity (Odeh 1968). Based on the experience of other tight gas fields in Ordos Basin, it is decided to use 24 ∼ 48 h as the interval of switching well, 10 d is the production time of the continuation period, and the last period is 30 ∼ 60 d. 2) Selection principle for test output Production Sequence Selection: The output is adjusted from small to large, and each output is approximately equal to a different number. Extension yield: It is generally not less than that minimum isochronous production stage yield. 3) Design parameters of two wells SM-X well test scheme: Well pressure recovery (2d) + 3 isochronous well sections (36h) + 1 extended production section (16d) + well pressure recovery (40d). SM-Y well test scheme: Well pressure recovery (5d) + 4 isochronous well sections (48h) + 1 extended production section (16d) + well pressure recovery (40d). The test output determines the output of different test sections and the shut-down time according to the production situation of the well, tests the flow pressure and the flow temperature gradient in different production sections, and tests the static pressure and the static temperature gradient after the closing well. (3) Construction equipment process and operation flow Construction equipment: steel wire well testing vehicles and supporting equipment, highprecision manometers, three-phase separators, and wellhead pipeline insulation equipment. Field Workflow: survey of well conditions is beneficial to understand the well site production conditions and the surrounding environment, and facilitate the arrangement of test construction; After reaching the wellsite, the production status of the well was observed for 24h. After the production status is stable, according to the design construction, the adjustment needs to ensure that the wellhead pipeline does not appear to freeze the blockage phenomenon under the minimum output. For the water-producing gas well, the minimum output must be greater than the critical liquid-carrying output; it is required to do well the wellhead pressure gage

64

insulation work and ensure that the pressure gage temperature is within its normal working range; (c) it is needed to ensure that production fluctuations do not exceed 5%; when the steel wire suspension technology is used for construction, the downhole pressure gage goes down to the middle of the gas layer as far as possible to eliminate the influence of the accumulated liquid and ensure the conversion accuracy of pressure and temperature; after the test is finished, the downhole manometer is proposed and the data is played back. 4 RESULTS (1) General situation of operation This test has 2 wells: Benxi Group and Taiyuan Group, the actual test variable production test time and test time in the field are basically consistent, the extended production time and the final shut-off well time is longer than the design time, the test data quality is very high, and this test is successful. The gas well test pressure yield overview and basic parameters are shown in Tables 1 and 2. Table 1. Production capacity well testing production, pressure, schedule.

well Test number Phase

Average gas test production, time, m3 /d h

Measure the pressure at the end of the well Test point, MPa. number Phase

Average gas test production, time, m3 /d h

Measure the pressure at the end of the point, MPa.

Chuguanjing SM-X q1 Guanjing q3 Guanjing q3 Guanjing / / qextension Jhongguan Jing

0 5135 0 7292 0 8631 0 / / 4691 0

21.0656 13.4959 20.5120 9.3959 19.9216 4.5625 19.3429 / / 10.9632 21.5920

0 2200 0 4200 0 5800 0 8200 0 6200 0

16.8473 14.5730 16.5427 13.3620 16.2308 13.1200 16.0387 12.7380 15.3868 9.4800 17.3711

62 51 45 37 35 36 38 / / 409 1660

Chuguanjing SM-Y q1 Guanjing q2 Guanjing q3 Guanjing q4 Guanjing qextension Jhongguan Jing

140 32 49 39 48 48 48 47 49 627 1805

Table 2. Table of basic parameters of test wells. parameter

SM-X

SM-Y

level Well radius r, m reservoir thickness h,m average porosity φ,% Water saturation S,% viscosity µ, mPa·s Gas Compressibility C, MPa−1 gas volume coefficient Bg Coefficient of deviation Z Relative density of natural gas γg

Tai 2 Formation 0.079 1.5 9.2 42.3 0.0209 0.0410 0.0008 0.8818 0.7069

Benxi Formation 0.079 6.8 8.5 43.2 0.0183 0.0570 0.0010 0.8713 0.6146

(2) Interpretation of results of well testing Using Saphir well test software to interpret and analyze, using the full pressure history fitting from production to the end of the test, the fitting results are reliable and meet the test requirements. The interpretation results of pressure recovery well testing are shown in Table 3. 65

Table 3. Results of pressure recovery and interpretation for Shenmu Wells. Test Type

formation pressure MPa

permeability mD

crack length m

fracture diversion capability mD·m

total skin factor

formation pressure coefficient

SM-X SM-Y

21.595 17.412

0.22 0.08

41.7 22.5

106.2 121.5

2.17 –4.14

1.0927 0.8856

The pressure recovery test of the final well was analyzed, and the results showed that the physical properties of the two wells in Shenfu were poor, the capacity potential was limited, and the flow without resistance was low. Figures 2 and 3 show the explanation results of well testing with production capacity.

Figure 2.

Production capacity well test results for SM-X well.

Figure 3.

SM-Y well capacity well test results.

The slope of pressure variance/yield and yield curve of the characteristic curve is negative by using measured data, and the law of variation of yield and production pressure difference is inconsistent with seepage theory. That is, the binomial productivity equation B is negative, so it is 66

impossible to calculate the flow rate of the gas well without resistance. The conventional binomial and exponential capacity equations can not be established at present. Considering the pressure gradient of low permeability start and the influence of water production, the binomial capacity equations can add a constant term, as Eq. 4. 2 = Aqg + Bqg2 + C PR2 − Pwf

(4)

In formula: C is the initial start-up pressure constant. The C value is calculated by the trial algorithm, and the slope of the curve of FIG. 2 is changed from negative to positive. At this time, the unobstructed flow of the two wells is calculated according to Formula 4. See Table 4. Table 4. Results of modified isochronous well testing in Shenmu Wells. Well name SM-X SM-Y

Test Type

capacity equation

non-resistive flow 103 m/d

Binomial for capacity testing stable binomial Binomial for capacity testing stable binomial

P − P = 517.194q + 14.974q + 100 P − P = 505.442q + 0.06196qg2 P − P = 330.8996q + 0.3271q + 5 P − P = 320.8996q + 0.12771qg2

0.90 0.91 0.95 0.94

At present, the binomial production capacity equation of the pressure level method is used to explain, and then the final shut-off well pressure recovery interpretation results are used to calculate the unimpeded flow by using the one-point method formula derived from the continuation section stability point. The error between the two calculations of unimpeded flow is within 5%, and the results are highly consistent, which shows that the interpretation results are accurate, the production capacity of the well is low, and the production potential is limited. In this test, the test process is successful, which proves that the modified isochronous well test method is suitable for low-yield tight sandstone gas wells, and this method can be used for capacity evaluation of tight gas wells. (3) Discussion The practice of equal-time well test in Shenfu Block shows that: At present, the initial well pressure recovery (5d)+3 isochronous well sections (36–48h)+1 extended production sections (16d)+40d well pressure recovery can meet the test requirements. After 40 h, the formation pressure is basically stable, and prolonging the test time has little effect on the test results. For this test, the test process is successful, which proves that the modified isochronous well test method is suitable for low-yield tight sandstone gas wells, and this method can be used for capacity evaluation of tight gas wells. But the modified equal-time well testing time is long, the testing cost is high, for low-yield gas well testing is of little significance, it is suggested that the later test select the wellhead production 5 × 103 m/d to test, the higher the test yield, the higher the test value. The output of different test systems is equal to the number of differences, the greater the difference, the better the testing effect. The test gas well geological conditions are poor, the production capacity is low, the output difference of different production systems is small, and there is a low osmotic start pressure influence. Except that the production measurement time is long, the production capacity decays fast, resulting in the measured data interpretation being difficult. The correction of the equal-time well test and the stability point binomial method to calculate the non-resistance flow error within 5%. It is suggested that for low-capacity gas wells, test pressure recovery can calculate the non-resistance flow and capacity evaluation, greatly shortening the test time and reducing the test cost. For the wells with higher gas production, such as production greater than 5 × 103 m/d, we consider the correction of the pilot wells for capacity analysis; for low-yield gas wells, it is suggested to use the binomial method of the stable point to calculate the flow without resistance. Pipeline 67

freezing and blockage occurred during SM-Y well test, which caused test interruption. It is recommended that all kinds of plans be prepared during the test, and be careful to prevent abnormal production during the test, which caused a test failure.

5 CONCLUSION (1) The production capacity test results show that for the gas wells with gas production less than 1 × 103 m/d, the output of different production measurement systems is arranged in the equal difference series, the output is adjusted from small to large in order, the tolerance 2000m/d can meet the production measurement requirements, the conventional well correction equal-time trial wells using different system output by means of the equal-ratio series distribution method is not suitable for tight gas. (2) For dense gas wells, the measured data of modified isochronous well tests are of high quality. From the point of view of technology and design, the measured data are qualified. But the analysis is difficult, the slope of the indicated curve of the production capacity equation is negative, which cannot be analyzed by the conventional well test theory. It is needed to consider the effect of the water production and low permeability start pressure gradient, and the gas well flow can be accurately obtained through the transformation of the production capacity equation.

ACKNOWLEDGMENTS This work was not supported by any funds. The authors would like to show sincere thanks to those techniques who have contributed to this research.

REFERENCES Coleman, S.B., Clay, H.B., McCurdy, D.G., Norris, L.H. (1991) A new look at predicting gas-well load-up. Journal of petroleum technology., 43: 329–333. Carlson, E.S., Mercer, J.C. (1991) Devonian shale gas production: mechanisms and simple models. Journal of Petroleum Technology., 43: 476–482. Cellino, M., Graf, W.H. (1999) Sediment-laden flow in open-channels under non capacity and capacity conditions. Journal of hydraulic engineering., 125: 455–462. Kamath, J., Laroche, C. (2003) Laboratory-based evaluation of gas well deliverability loss caused by water blocking. SPE Journal., 8: 71–80. Lea, J.F., Nickens, H.V. (2004) Solving gas-well liquid-loading problems. Journal of Petroleum Technology., 56: 30–36. Odeh, A.S. (1968) Steady-state flow capacity of wells with limited entry to flow. Society of Petroleum Engineers Journal., 8: 43–51. Shan, C., Falta, R.W., Javandel, I. (1992) Analytical solutions for steady-state gas flow to a soil vapor extraction well. Water Resources Research., 28: 1105–1120. Swift, G.W., Kiel, O.G. (1962) The prediction of gas-well performance including the effect of non-Darcy flow. Journal of Petroleum Technology., 14: 791–798. Wattenbarger, R.A., Ramey, H.J. (1969) Well test interpretation of vertically fractured gas wells. Journal of Petroleum Technology., 21: 625–632.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Experimental study on water vapor share and waste heat recovery from biomass flue gas ChengXu Miao, Na Liang, Kai Fan, Han Wang & JianWei Wang∗ College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao, China

ABSTRACT: With the optimization of China’s energy structure, biomass as a carbon-neutral, renewable energy source has a substantial development and utilization value. However, the current biomass fuels are applied mainly by direct combustion, which has the problem of low thermal efficiency. In this paper, we primarily investigate the share of water vapor in the flue gas produced by biomass combustion and the effect of its vaporization latent heat recovery on the improvement of thermal efficiency. Through theoretical calculations, the share of water vapor in the flue gas generated by the combustion of three biomass fuels was derived; experimental tests were conducted using a biomass vaporization experimental combustion bench containing a condensing heat exchanger to investigate the effects of different factors on the recovery of waste heat in the flue gas of pine fuel combustion. The results showed that the thermal efficiency improvement was about 6%–9% under several operating conditions measured experimentally, and the thermal efficiency improved by latent heat was significantly higher than that by sensible heat, indicating that recovering latent heat from biomass boilers to improve thermal efficiency has excellent potential and practical application.

1 INTRODUCTION In recent years, to solve the problem of air pollution, China has forced out small coal-fired industrial boilers and started to promote natural gas boilers vigorously. However, in 2017, China’s external dependence on natural gas energy was close to 40%. The severe shortage of natural gas supply will be a complex problem that China will have to face for a long time in the future. In contrast, biomass has the advantages of renewable, widespread, low sulfur, and carbon neutrality, accounting for about 14% of the world’s total energy consumption. Moreover, with the continuous improvement of China’s energy structure and the proposal and promotion of “carbon peak” and “carbon neutralization” target schemes, biomass fuels have ushered in new historic development opportunities. Currently, the primary utilization method of biomass energy in China is direct combustion, and overall, the existing biomass boilers have the problem of still low average thermal efficiency. Most conventional technical measures that can effectively reduce heat loss have already been popularized, such as switching to vibrating grates, installing ash cleaning devices, and installing additional secondary air. It is more challenging to improve the thermal efficiency of biomass boilers significantly. Some outstanding features of biomass, such as much higher water content and hydrogen to carbon ratio than coal, and much higher oxygen content than natural gas, make its flue gas also contains a large amount of water vapor. Moreover, this makes it possible to improve the thermal efficiency of boilers by recovering the latent heat of water vapor. 2008, Finland’s largest biomass heating station applied condensed heat exchange technology. The power of a single ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-13

69

biomass-fueled circulating fluidized bed boiler at this heating station was 40 MW, which reduced the exhaust flue gas temperature to 35◦ C and achieved a boiler thermal efficiency of 118% in terms of low-level fuel heat generation. However, many studies have been conducted on the recovery of latent heat of water vapor in the flue gas. So far, the studies have mainly focused on the flue gas from natural gas boilers with high carbon-to-hydrogen ratios and the flue gas emitted from large coal-fired boiler units rich in water vapor after limestone-gypsum wet flue gas desulfurization. In contrast, relatively few studies have been conducted on the recovery of latent heat of water vapor in flue gas from biomass boilers. This paper theoretically calculates the flue gas after the combustion of pinewood, rice straw, and Enteromorpha. The water vapor share in the flue gas under different excess air coefficients is obtained. At the same time, the condensation heat exchanger is installed on the biomass gasification and combustion test-bed to experiment with waste heat recovery of flue gas, and the effects of different factors on the waste heat recovery in the flue gas of pinewood fuel combustion are explored. 2 THEORETICAL CALCULATION OF BIOMASS FLUE GAS Biomass fuel contains more moisture than coal, natural gas, and other fossil fuels, so the water vapor content in the flue gas after biomass combustion is high, and the recoverable water vapor latent heat share in the flue gas is also significant. In this paper, some primary data on wood, straw, and seaweed biomass are collected. The characteristics of these three biomass fuels are shown in Table 1. Table 1. Fuel characteristics of biomass. The characteristics

Industrial analysis (%)

Elemental analysis (%)

Low calorific value (KJ/kg)

Pinewood

Rice straw

Enteromorpha

Mad FCad Vad Aad

10.13 35.96 50.30 3.60

0 18.58 71.70 9.72

13.30 7.79 41.82 37.09

Cad Had Oad Nad Sad

41.80 5.78 37.80 0.80 0.08

43.45 6.38 39.42 0.88 0.15

22.74 6.27 16.19 3.14 1.27

QLH

17085

17230

7890

The above three biomass fuels are theoretically calculated, and the volume share of water vapor in flue gas after complete combustion of pinewood, rice straw, and Enteromorpha under the conditions of different moisture content and excess air coefficient is obtained. It can be seen from Figure 1 that under the same excess air coefficient, the volume share of water vapor in flue gas increases with the increase of moisture content of biomass fuel; when the moisture content is the same, the water vapor content decreases with the increase of excess air coefficient. Taking pinewood fuel with the moisture content of 15% and excess air coefficient α = 1.2 as an example, the amount of water vapor in the flue gas after combustion is about 16.23%, that of straw after combustion is about 16.77%, and that of Enteromorpha after combustion is about 20.82%. The calculation results show that the flue gas after biomass combustion has much moisture, and the water vapor condensation heat in the flue gas can be recovered under certain conditions to reduce the exhaust heat loss, thus improving the energy utilization rate. Compared with fossil 70

fuels, biomass fuels have more advantages in recovering waste heat and improving the thermal efficiency of boilers.

Figure 1. flue gas.

Relationship between the water content of biomass and volume content of water vapor in the

In general, conventional biomass boilers are used in direct combustion. The required excess air coefficient is as high as 1.6, while the excess air coefficient in gasification combustion can be reduced to 1.1. Therefore, the excess air coefficient is reduced after the biomass fuel is gasified in an upward suction gasifier. Then the share of water vapor in flue gas is increased, which is conducive to the recovery and utilization of latent heat of water vapor in the flue gas.

3 EXPERIMENT OF BIOMASS FLUE GAS WASTE HEAT RECOVERY The biomass combustion experimental device is shown in Figure 2, including an updraft gasifier, Tars cracking, bag filter, furnace chamber, heat accumulator, burner, four-way valve, condensation heat exchanger, and other equipment. The furnace diameter of the gasifier is 160 mm, and the height is 810 mm. The updraft gasifier gasifies biomass fuel into gas, and the gas is burned in stages on the burner. The generated flue gas first passes through the regenerative heat exchanger for heat exchange and then enters the condensing heat exchanger. The water vapor in the flue gas changes phase in the condensation heat exchanger to release the latent heat of vaporization, and then the flue gas leaves the thermal system. 71

Figure 2. The biomass combustion experimental device.

The regenerator of the regenerative heat exchanger is made of honeycomb ceramics, which has good corrosion resistance and effectively increases the heat exchange area and saves space and cost. The furnace diameter of the heat storage boiler is 200 mm, the height is 300 mm, and the size of the honeycomb ceramic regenerator on both sides is 500 mm × 240 mm × 120 mm. K-type thermocouples are installed at the inlet and outlet of the regenerator. It is used to measure the inlet and outlet flue gas temperature. In order to overcome the low-temperature corrosion of flue gas below the dew point temperature, the condensation heat exchanger in the experiment is made of fluoroplastic material with strong corrosion resistance. The feedwater mass flow and condensate flow are measured by a vortex flowmeter, and the water temperature is measured by PT100 thermal resistance. Table 2. Outlet temperature of flue gas and cooling water. Outlet temperature of flue gas (◦ C)

Outlet temperature of cooling water (◦ C)

Condensate volume(kg/h)

Case 1 Case 2 Case 3 Case 4

40.8 39.5 38.5 37.3

30.8 30.6 30.4 30.1

0.536 0.547 0.561 0.578

Case 1 Case 2 Case 3 Case 4

40.5 41.4 42.6 43.1

30.8 32.3 33.0 34.1

0.522 0.518 0.514 0.511

Case 1 Case 2 Case 3 Case 4

40.2 42.3 45.4 50.9

30.9 31.3 31.9 32.2

0.533 0.541 0.552 0.560

Case 1 Case 2 Case 3 Case 4

40.7 40.4 40.1 39.8

30.3 30.5 30.8 30.9

0.533 0.568 0.635 0.748

Experiment Section 2.1

Section 2.2

Section 2.3

Section 2.4

Pinewood was used as fuel in the experiment. The benchmark conditions were as follows: the moisture content was 10.14% and the excess air coefficient was 1.1. In the condensation heat exchanger, the cooling water flow rate is 0.15 m/ s, the cooling water inlet temperature is 20.1◦ C, the flue gas flow rate is 6 m / s, and the flue gas inlet temperature is 100.7◦ C. The effects of cooling water flow rate, cooling water inlet temperature, flue gas flow rate, and moisture content on the 72

recovery of flue gas waste heat and condensate after pinewood combustion were studied by the controlling variable method. Under all experimental conditions, the temperature of flue gas entering the condensation heat exchanger and cooling water leaving the condensation heat exchanger and the amount of condensate are shown in Table 2. Accordingly, the improved thermal efficiency of flue gas waste heat recovery can be calculated according to the data in the table.

4 TEST RESULTS AND DISCUSSIONS 4.1 Effect of different flow rates of cooling water The flow rate of cooling water was changed by adjusting the valve of the cooling water flowmeter, and the flow rates of cooling water were selected as 0.15m/s, 0.17m/s, 0.19m/s, and 0.21m/s as the study variables, and the effect of cooling water flow rate on the thermal efficiency of latent and sensible heat improvement and condensate recovery was obtained, as shown in Figure 3.

Figure 3.

Effect of different flow rates of cooling water.

The thermal efficiency of sensible heat and latent heat increases with the cooling water flow rate. The reason is that with the increase in cooling water flow rate, the heat transfer coefficient of the surface increases, the heat transfer is strengthened, and the outlet temperature of flue gas decreases. That is, the inlet and outlet temperature difference increases, and the sensible heat recovery is enhanced. In addition, as the cooling water flow rate increases, the temperature of the heat exchanger tube decreases, the condensate recovery from flue gas increases, condensation heat transfer is enhanced, and the thermal efficiency of latent heat improvement increases. Furthermore, it can be seen from Figure 3 that the thermal efficiency improved by sensible heat is more significant than latent heat, with a maximum increase of 6.76% at a cooling water flow rate of 0.21 m/s. This also proves the necessity of recovering the latent heat of water vapor in the flue gas.

4.2 Effect of different inlet temperatures of cooling water The inlet temperatures of cooling water of 20◦ C, 22◦ C, 24◦ C, and, 26◦ C were selected as the study variables to investigate the effect of cooling water temperature on the thermal efficiency of latent and sensible heat increase and condensate recovery. 73

Figure 4.

Effect of different flow rates of cooling water.

As shown in Figure 2, the thermal efficiency of sensible heat and latent heat increase decreases with the cooling water inlet temperature. As the inlet temperature increases, the heat transfer temperature difference of the condensing heat exchanger decreases, and the heat transfer performance decreases. Furthermore, the outlet temperature of flue gas increases, the temperature difference of flue gas inlet and outlet also gradually decreases, the amount of sensible heat recovery decreases, and the thermal efficiency of sensible heat increase also decreases. Moreover, as the inlet water temperature increases, the temperature of the heat exchange tube increases, and the condensation heat transfer on the flue gas side weaken, the latent heat released also decreases, and the improved thermal efficiency decreases. 4.3 Effect of different flow rates of flue gas Flue gas flow rates of 6 m/s, 6.5 m/s, 7 m/s, and 7.5 m/s were selected as the study variables to investigate the effect of flue gas flow rate on the thermal efficiency of latent and sensible heat improvement and condensate recovery. As shown in Figure 5, the sensible heat improved thermal efficiency increases first with the flue gas flow rate. It then decreases because the more significant the flue gas velocity, the greater the surface heat transfer coefficient, and the sensible heat will increase.

Figure 5.

Effect of different flow rates of flue gas.

However, when the flue gas flow rate exceeds 7m/s, the less heat exchange time between the flue gas and the tube wall, the less the sensible heat is utilized. Moreover, the outlet temperature 74

of the flue gas increases, the temperature difference between the import and export of the flue gas decreases, and the sensible heat improved thermal efficiency decrease. In addition, as the flow rate of flue gas increases, the amount of flue gas entering the heat exchanger increases, carrying more water vapor into it, more latent heat can be recovered, and the latent heat recovery increases the thermal efficiency. Overall, the total thermal efficiency that can be improved is less influenced by latent heat recovery and more by sensible heat recovery. With the increase in flue gas flow rate, the total thermal efficiency that can be improved tends to rise first and then fall. 4.4 Effect of different biomass moisture content

Figure 6.

Effect of different biomass moisture content.

Pinewood with moisture contents of 10.14%, 15.03%, 20.21%, and 25.51% were selected as the study variables to investigate the effect of material moisture on latent and sensible heat improved thermal efficiency and condensate recovery. As shown in Figure 6, the thermal efficiency of sensible and latent heat improvement increases with the increase of moisture content of biomass fuel, where the effect of latent heat improvement is more prominent than the sensible heat. Because the higher the moisture content of biomass, the more significant the proportion of water vapor contained in the flue gas. The water vapor partial pressure will increase, the dew point temperature will rise, and the condensate volume will increase. As the moisture content of biomass increases, its low calorific value decreases, and the effect of latent heat to improve thermal efficiency becomes apparent. The more the moisture content of biomass, the less flue gas produced by combustion, and the recovered sensible heat decreases. However, due to the decrease of its low calorific value, the heat efficiency recoverable by sensible heat tends to rise.

5 CONCLUSION In this paper, theoretical calculations were performed on the flue gas produced by combustion of three biomasses under different excess air coefficients, the relationship between the water vapor share in the flue gas and the excess air coefficient, and the water content of the biomass was derived. Combustion experiments were conducted on pinewood fuels. The effects of cooling water flow rate, cooling water temperature, flue gas flow rate, and water contents of biomass fuels on the effect of waste heat recovery in the biomass flue gas were systematically studied, and the following conclusions were drawn. 1. The flue gas from biomass combustion contains much water vapor. The highest share of water vapor in the flue gas can reach 28.88%, with a large amount of latent heat available for recovery. 75

2. The share of water vapor in the flue gas from biomass combustion increases as the excess air coefficient decreases and the water content of biomass increases. Decreasing the excess air coefficient is conducive to recovering the latent heat of vapor in the flue gas. 3. Under several experimental conditions, the thermal efficiency can be increased by about 6% to 9%. The latent heat to improve the thermal efficiency is significantly higher than the sensible heat, proving the feasibility and practical application value of recovery of latent heat in the flue gas.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Coal system reservoir fracturing technology of Carboniferous Benxi Formation in Shenfu block Minghao Wang China United Coalbed Methane Company, Shenmu Shaanxi, China

Hanlie Cheng COSL-EXPRO Testing Services (Tianjin) Co., Ltd., Tianjin, China

Zhaoyuan Cheng∗ College of Petroleum Engineering, Xi’an Shiyou University, Xi’an Shaanxi, China

Ke Zhang & Ming Sun COSL-EXPRO Testing Services (Tianjin) Co., Ltd., Tianjin, China

ABSTRACT: The reservoir of Benxi Formation of Carboniferous in Shenfu block is highly heterogeneous and belongs to low porosity and low permeability coal measure sandstone. The average porosity is 4.2%, the permeability is 0.35 mD, and the natural gas production of the gas well is low. The production needs to be obtained through fracturing. Fracturing reconstruction is an important measure for exploration and development in this area, but the fracturing effect of some wells is poor in recent years. Therefore, targeted research on fracturing technology and supporting technologies is needed to improve the drilling success rate and fracturing effect. In this paper, the experimental evaluation of rock mineral composition and rock mechanics is carried out by means of full core analysis and X-ray diffraction. The research shows that the young’s modulus of the Benxi Formation reservoir is 26300 MPa ∼ 28200 MPa, the Poisson’s ratio is 0.24 ∼ 0.26, and the lithology is mainly quartz sandstone, indicating that the rock is brittle, the formation is relatively easy to open (when the in-situ stress is not particularly high, but it is not easy to open in deep wells in the western region), and the calculated brittleness index is 50 ∼ 52%. The minimum principal stress is 50.7 ∼ 54.7 MPa, the maximum principal stress is 69.8 ∼ 74.1 MPa, the maximum and minimum stress difference is 19.1 ∼ 19.4 MPa, and the in-situ stress difference coefficient is 0.35 ∼ 0.38, which is not easy to form a complex fracture network. The stress difference of the interlayer is 6.1 MPa and that of the lower interlayer is 8.4MPa. The nature of the interlayer is general. High fracture control technology shall be adopted for fracturing to prevent excessive fracture extension. Based on the reservoir characteristics of the Benxi Formation, the fracturing process is optimized, and finally, a fracturing technology suitable for the study area is formed.

1 INTRODUCTION The fracturing technology has been developed for many years. Because of its ability to increase the production of a single well and increase injection, it has been widely used in the world. So far, the research on fracturing technology has achieved a high achievement and created a greater economic benefit (Liu 2018). In the 1970s, fracturing technology became the main means of increasing the efficiency of oil and gas reservoirs because of the need of developing a low permeability oilfield. However, with the development of the oil field, the fracturing process has been developed and perfected according to the requirements of different periods, objects and technologies. In the 1980s, ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-14

77

fracturing technology has been greatly developed with fracturing optimization design, fracture diagnosis and fracturing material improvement. It is closely combined with reservoir engineering and becomes a powerful measure to improve the efficiency of oil recovery and oilfield development (Guo 2020). During this period, the limited flow fracturing completion technology, including the thin interlayer balance limited flow fracturing completion technology, successfully solved the low permeability thin sandstone fracturing excavation problem (Ju 2020). After the 1990s, the location balance fracturing technology is also aimed at the old well thin differential layer and high water-thin interbed fracturing potential, fracturing technology has become the main factor of the low permeability oilfield development program, making it possible to develop efficiently (Liu & Wang 2018) Shenfu Block is located on the eastern margin of Ordos Basin, block area is 2998.4 km, the gas exploration block belongs to the prospecting jurisdiction of CNOOC. In recent years, the drilling in the Benxi Formation of the Carboniferous System has obtained natural gas resources and formed a certain scale of natural gas exploration, but there is a problem of low gas production in some natural gas wells (Wang 2018). The present study shows that the Benxi Formation of Carboniferous is a coal-based reservoir with a thin thickness and a single sand layer with a thickness of 2 ∼ 8 m, which brings great difficulties to the fracturing modification and is also an important reason for the poor effect of fracturing modification in some wells. In view of the reservoir reformation technology of tight gas reservoirs, a lot of experience has been obtained at home and abroad. This paper analyzes the reservoir characteristics of the Benxi Formation, through the investigation of a similar block fracturing process, and on this basis combined with the Benxi Formation’s low porosity, ultra-low permeability, thin interbed characteristics, analysis of the Benxi Formation fracturing difficulties, the corresponding fracturing technology countermeasures and research measures. So as to achieve that success rate of the construction of the coal system reservoir and the lamination of the Benxi Group and improve the fracturing effect of the Benxi Group, thereby improving the exploration awareness and economic benefit, and providing a reference for the fracturing transformation of the Benxi Group.

2 COAL RESERVOIR CHARACTERISTICS 2.1 Reservoir lithology The study area is affected by the deposition and tectonic evolution of the entire Ordos Basin. Upper Paleozoic mainly developed the Permian Upper Shiqianfeng Formation, Zhongtongshihezi Formation and Xiadongshan Shanxi Formation, Taiyuan Formation and Carboniferous Upper Benxi Formation. The Benxi Formation was divided into the Benxi 2 and the Benxi 1 from the bottom up. The main types of sandstone in the Benxi Formation are quartz sandstone, followed by lithologic quartz sandstone, which contains a small amount of lithologic sandstone and feldspar quartz sandstone. Most of the debris components in sandstone reservoirs are quartz, the content of quartz is 52.8–89.0%, and the average content is 70.3%. The second is rock debris with little feldspar content. The components of rock debris include sedimentary rock debris, igneous rock debris, metamorphic rock debris, mica and flintstone. Metamorphic rock debris is the main component of rock debris, and the content of mica and flintstone is very small. The content of the interstitial matter group in the Benxi Group was 3.6% ∼ 16.5%, and the average was 10.1%. The particle size of debris in the Benxi Formation has a great change, the largest particle size is 10.00 mm, mainly in the range of 0.20 ∼ 1.5 mm, and the vast majority of medium-coarse sandstone, a small amount of fine sandstone and conglomerate (Figure 1). Sandstone is dense, composition maturity and structure maturity are higher, the grading is equal—good, and the grinding circle is mainly subangular—minor circle. The concave-convex contact or inlay contact is the main contact between the particles, most of which are particle support and also can see a small amount of heterosis and substrate support. The types of cementation are pore type cementation, regeneration—pore type cementation, compression—contact cementation, substrate—pore type cementation, substrate type cementation, contact cementation, mosaic cementation, and mainly pore type cementation and regeneration—pore type cementation. The average porosity is 4.2% and permeability is 0.35 × 78

10 µm, which is a very low porosity and low permeability gas reservoir (GB/T 26979-2011 gas reservoir classification).

Figure 1.

Gray-white fine sandstone core samples (2453.01m).

The pore types of sandstone reservoir in the Benxi Formation are mainly residual intergranular pore, intergranular pore, lattice intra-granular pore, microporous pore and micro-fracture. According to their causes, they are divided into the primary pore and secondary pore. Benxi Formation reservoir is deeper, compaction and late diagenesis are strong, the pore type of sandstone is mainly secondary pores, and is divided into three types of intergranular dissolution pores, lattice intra-granular dissolution pores and cracks. 2.2 Reservoir temperature and pressure The formation pressure is 0.7 ∼ 1.1, the average is 0.85, which is low pressure—normal pressure reservoir (GB/T 26979-2011). The ground temperature gradient is 3.2◦ C/m, the temperature range is 80 ∼ 120◦ C, and the average is 100◦ C. 3 ROCK MECHANICS EXPERIMENT The core is in a compression state in the deep part of the formation due to the earth stress, and the natural fractures are also in a closed state. When the core is taken to the ground, the core will expand due to stress release, resulting in many new micro-cracks. The degree of these microcracks opening and the density and direction of production will be related to the state of the in situ environmental stress field of the core, which is the reflection of the underground stress field. The direction of maximum and minimum principal stress in space can be obtained by analyzing the different strains in different directions of core pressurization. This method is called differential strain analysis (DSA). The differential strain analysis method is tested based on the following assumptions: All the micro-cracks are produced by the release of local compressive stress, which is consistent with the principal stress direction. If the formation is isotropic, then when a principal stress value can be obtained independently, the principal strain ratio can be used to obtain the value of the in situ stress. In the laboratory, the rock sample is pressurized by hydrostatic pressure, the micro-cracks due to stress release will be closed first. After the crack is closed, the load is continued. The deformation is caused by rock solid deformation (skeleton compression). Figure 2 The typical curve of the relationship between strain and pressure measured after loading. The curve is divided into two parts, the first part is due to the strain caused by the closing of micro-cracks and the compression of the rock skeleton. The slope of the second part is smaller. The difference between the slopes of the two parts reflects the strain due to the closure of the microcracks alone. The direction of the 79

maximum principal strain (i.e., the maximum principal stress) can be obtained by distinguishing the contribution of microcracks to the direction of deformation. The rock sample is loaded into the pressure chamber of the instrument, connected with each strain gage sensor wire, and the pressure chamber is lifted and closed to drain the hydraulic circuit. After three cycles of pressurization/depressurization from 150 Psi∼10000 Psi∼150Psi, the strain changes during the whole pressurization/depressurization process were recorded. The experimental results show that the average elastic modulus of the Benxi Formation reservoir core is 27475 MPa, and the average Poisson’s ratio is 0.25, indicating that the rock is brittle. The average value of the minimum principal stress was 54.7 MPa, and the stress gradient was 0.019 MPa/m. The maximum principal stress is 74.1MPa, the maximum and minimum principal stress difference is 6 MPa ∼ 30 MPa, the average is 19.4 MPa, and the stress difference coefficient is more than 0.3, which is not easy to form a complex seam net.

Figure 2. Typical strain curve diagram.

The calculation of the geostress profile shows that the minimum principal stress of the average reservoir is 50.7 MPa, the maximum principal stress is 68.9 MPa, and the maximum and minimum principal stress difference is 10 MPa∼20 MPa, and the average is 19.1 MPa. Poisson’s ratio is 0.22, and Young’s modulus is 26.3 GPa. The average stress of the upper and lower spacers is 58.7 MPa, the average stress of the lower spacers is 59.1 MPa, the average stress difference between the upper spacers and the reservoir is 6.1 MPa, the average stress difference between the lower spacers and the reservoir is 8.4 MPa, and the upper and lower spacers have a certain shielding effect. 4 FRACTURING PROCESS OPTIMIZATION For the reservoir with a large difference in ground stress and large thickness of the reservoir, the mechanical layered fracturing technology was adopted to optimize the combination of fracturing string and downhole tools to ensure the success rate of construction. For the reservoir with a small difference in ground stress and small thickness of the reservoir, the degradable fiber or degradable temporary blocking agent is adopted to carry out the layered fracturing, and the fiber and the temporary blocking agent are optimized to optimize the adding amount, thereby achieving the purpose of layered reconstruction and improving the section use degree. 4.1 Measures for reducing the fracture pressure In view of the problem of high fracture pressure of a deep well with a depth over 3500m, the treatment measures are as follows: 1) Acidification pretreatment technology. The rock structure near the borehole is destroyed and the rock’s mechanical strength is reduced to reduce the fracture pressure. Changing the magnitude 80

2)

3)

4)

5)

6)

and direction of the lithology stress and weakening the mechanical properties of the rock itself are the fundamental reasons for the decrease of the fracturing pressure of the formation and have a good effect on reducing the fracturing pressure of the formation itself. Perforation optimization technology. Increasing the perforation density, controlling the perforation azimuth and increasing the perforation diameter can increase the effective perforation number, destroy the lithology near the wellbore, and reduce the bending friction of fracturing fluid near the well zone and the friction pressure when fracturing fluid flows through the perforation, thereby directly or indirectly reducing the formation fracture pressure. The process of gas pushing perforation. The invention is characterized in that: a gas propelling seam forming device (containing a supporting agent) is arranged outside a conventional perforating gun body; the perforating bomb is firstly detonated; when the metal flows through the seam forming device, the seam forming device is ignited; a large amount of high-energy gas generated is carried out to the formation through hole-casting along the newly formed perforation hole; as the supporting agent enters, not only the perforation depth is increased, but also the crack width is kept. Gas-driven seam formation process can effectively reduce the formation fracture pressure, eliminate perforation compaction zone, avoid and eliminate near-well zone pollution, and create necessary conditions for fracturing transformation. The pre-treatment technology can not only reduce the pressure of formation rupture but also be applied to the production improvement of the fractured carbonate reservoir and the low-porosity and low-permeability formation. Low friction fracturing fluid system. The low viscosity and high-density fracturing fluid suitable for the performance requirements of fracturing fluid was studied, the concentration of thickening agent was optimized, the viscosity of fracturing fluid was controlled, and the friction resistance along the tube column was reduced as much as possible. High energy gas fracturing technology. The invention utilizes the controlled burning of gunpowder in the oil-gas well to generate a large amount of high temperature and high-pressure gas which exceeds the maximum local stress value of the oil-gas layer to act on the oil-gas layer in a pulse loading mode, so that the oil-gas layer rock around the wellbore breaks and forms a plurality of radial cracks which are not controlled by the ground stress. Because high-energy gas fracturing can break the rock around the wellbore and change the magnitude of ground stress, the formation fracturing pressure can be greatly reduced, which reduces the difficulty of fracturing construction caused by high fracturing pressure. Therefore, high-energy gas fracturing pretreatment plays an important role in reducing the formation fracture pressure. The technology of aggravating fracturing fluid. The invention can not only reduce the construction pressure when the formation is broken at the initial stage of construction, but also ensure the smooth extension of the crack, thereby reducing the construction difficulty and being simple and feasible.

Combined with the characteristics of strong acid sensitivity of the Benxi Formation reservoir, combined with the need to reduce costs, comprehensive consideration of the recommended early test evaluation of acidification pretreatment measures, such as limited effect can be combined with the application of perforation optimization technology, gas propulsive perforation process and low friction fracturing fluid system to reduce fracturing construction fracturing pressure.

4.2 Temporary blockage fracturing of degradable materials For the reservoir with a small difference in ground stress and small thickness of the reservoir, the degradable fiber or degradable temporary blocking agent is adapted to carry out the layered fracturing, and the fiber and the temporary blocking agent are optimized to optimize the adding amount, thereby achieving the purpose of layered reconstruction and improving the section use degree. In the fracturing fluid added a certain concentration of fiber, using the network structure of the fiber to produce super-strong suspension carrying capacity and proppant fixation capacity, so that the fluid in the formation occurs the turn, to achieve fracking transformation (Figure 4). 81

4.3 Preferred fracturing fluid According to the characteristics of the compact and low-pressure reservoirs, three kinds of fracturing fluid evaluation were carried out to reduce the residual damage of guanidine glue, clay expansion damage and fracturing fluid retention formation damage. From the results of laboratory experiments and field experiments, three kinds of fracturing fluid systems can meet the requirements of fracturing construction for extending the Benxi Formation. The core damage rate and performance parameters of the degumming fluid residue show that the performance of clean fracturing fluid is better than that of low concentration guanidine fracturing fluid and that of conventional guanidine fracturing fluid. Hydroxypropyl guanidine is widely used in oil and gas well fracturing as a thickening agent of water-based fracturing fluid, which has the characteristics of strong thickening ability, good shear resistance, good thermal stability and strong control of loss. Fracturing fluid not only improves the oil and gas channels but also brings some damage to the reservoir. The main damage of fracturing fluid to the reservoir is the damage to matrix permeability by fracturing fluid filtrate and the damage to supporting fracture diversion ability by fracturing fluid residue and filter cake. A large number of studies have shown that fracturing fluid residue injury can reduce the diversion capacity by more than 90%, and the damage of gel-breaking fluid residue occupies the dominant position of reservoir damage. In order to evaluate the damage of the fracturing fluid system to the reservoir, the conventional fracturing fluid system, low concentration guanidine gel fracturing fluid system and clean fracturing fluid system were used in the experiment. Figure 3 shows the core damage experiment results of three fracturing fluid system cores through the fracturing fluid, permeability decreased, showing that fracturing fluid on the reservoir has a certain degree of damage, but the clean fracturing fluid has a lower fracturing fluid damage rate, only 7.8%, followed by low concentration of guanidine gel fracturing fluid system core damage rate of 13.0%, also has the characteristics of low damage.

Figure 3.

Experimental results of core damage in three fracturing fluid systems.

4.4 Preferred proppant In light of low-porosity, ultra-low permeability and thin interstorage laminated fracture transformation, the formation of narrow crack width, easiness to cause early sand blocking, the selection of suitable particle size of supporting agents, fracturing construction success plays a key factor. In the past, Benxi Formation basically used 20 ∼ 40 mesh ceramisite as the main supporting agent. From the construction process, it can basically meet the requirements of fracturing transformation and crack diversion capacity. However, in some reservoirs with poor physical properties or deep 82

target layer, because of the large clay content or limited discharge, resulting in insufficient width of the gap and sand difficulty phenomenon. When the construction displacement is less than 2.5 m/min or the closed stress is more than 50 MPa, the average width of the crack is about 2 mm. According to the Gruesbeck supporting agent bridge criterion, the principle is that the width of the crack is more than three times the diameter of the supporting agent. In the high mud content section or low displacement well, 30– 50 mesh ceramic particles are recommended. The experimental results show that 30–50 mesh ceramsite can provide about 40 mD diversion capacity under 50 MPa closure pressure, which can meet the needs of reservoir transformation. 4.5 On-site application In view of the Benxi Group buried depth of more than 3500 m measure well, the supporting fracturing process scheme is suggested as follows: 1) Fracturing the string. The perforation, fracturing and drainage can be realized by the combined process of 2-/oil pipe transmission perforation gun and fracturing. 2) Fracturing fluid system. By extending the system of 0.28–0.32% low-concentration guanidine glue-water-based fracturing fluid, the requirements of sand-carrying performance of the 80 ∼ 120◦ C reservoir transformation can be met, and the fracturing fluid friction resistance can be further reduced, and the reservoir damage can be reduced. 3) Proppant. The 40–70 mesh ceramic slug can effectively reduce the bending and friction resistance of the hole and near-well cracks, and the 20–40 mesh ceramic slug is adopted in the main sand adding stage. 4) Construction parameters. The discharge capacity is 2.5∼3.5 m/min, the upper and lower layers of the target layer are well developed, and the proportion of the proposed liquid is increased to 35%∼40%. The property of the interlayer is general, and the distance between the interlayer and the coal layer and the limestone layer is close, and the proportion of pre-liquid is increased to 40%–45%. In addition, the sand plug ratio of the pre-liquid stage is reduced to 5%, and the quantity of the sand plug is flexibly adjusted according to the on-site construction effect. The sand ratio step is further reduced in the continuous sand adding a stage, the low sand ratio stage (sand ratio below 15%) is started with 4% steps, the medium sand ratio stage (sand ratio between 15% and 20%) is applied with 3% steps, and the high sand ratio stage (sand ratio above 20%) is applied with 2% steps. The maximum sand ratio is reduced to 30%, and the average sand ratio is reduced to 18–20%. 5) Energy and emission enhancement. By using liquid nitrogen injection measures, each gas layer in each block has formed a mature matching pump injection parameters, the average liquid nitrogen accounts for 7.3% of the net liquid volume in the well, the site according to the construction pressure for flexible adjustment. 6) Forced crack closure rapid reflow process. On the basis of the current drainage control measures, the implementation of the “forced crack closure rapid back-drainage process” is further strengthened, before the artificial crack closure, the use of a small-sized oil spout (3–4 mm) to control the drainage, after the artificial crack closure, the rapid replacement of large-sized oil spout, so as to reduce the fracturing fluid damage to the formation and maintain the maximum supporting crack diversion capacity.

5 CONCLUSION (1) The young’s modulus of the Benxi Formation reservoir is 26300 ∼ 28200 MPa, Poisson’s ratio is 0.24 ∼ 0.26, the rock is relatively brittle, and the formation is relatively easy to open (when the in-situ stress is not particularly high, but it is difficult to open when the in-situ stress of deep wells in the western region is high). The calculated brittleness index is 50 ∼ 52%. 83

Rock mechanical properties: the minimum principal stress is 50.7 ∼ 54.7 MPa, the maximum principal stress is 69.8 ∼ 74.1 MPa, the maximum and minimum stress difference is 19.1 ∼ 19.4 MPa, and the in-situ stress difference coefficient is 0.35 ∼ 0.38. The two-dimensional stress difference of the reservoir is large, so it is not easy to form a complex fracture network. The stress difference between the upper compartment is 6.1mpa and the lower compartment is 8.4 mpa. The nature of the compartment is relatively general. High fracture control technology shall be adopted for fracturing to prevent excessive fracture extension. (2) In order to further improve the success rate of fracturing construction of Benxi Formation, for the reservoir with large in-situ stress difference and large spacer thickness, mechanical layered fracturing technology is adopted to optimize the combination of fracturing string and downhole tools to ensure the success rate of construction. For the reservoir with a small in-situ stress difference and small spacer thickness, a degradable composite temporary plugging agent is adopted for layered fracturing to achieve the purpose of layered reconstruction and improve the production degree of profile.

ACKNOWLEDGMENTS This work was not supported by any funds. The authors would like to show sincere thanks to those techniques who have contributed to this research.

REFERENCES Guo, Q., Wang, X., Qu, L. (2020) A new method for identifying fractures in tight sandstone of a gentle structural area using well logs. Energy Science & Engineering., 8: 3909–3924. Ju, W., Shen, J., Li, C., Yu, K., Yang, H. (2020) Natural fractures within unconventional reservoirs of Linxing Block, eastern Ordos Basin, central China. Frontiers of Earth Science., 14: 770–782. Liu, D., Liu, C., Kang, Y., Guo, B., Jiang, Y. (2018) Mechanical behavior of Benxi Formation limestone under triaxial compression: a new post-peak constitutive model and experimental validation. Bulletin of Engineering Geology and the Environment., 77: 1701–1715. Liu, S., Wang, J., He, H., Wang, H. (2018) Mechanism on imbibition of fracturing fluid in the nanopore. Nanoscience and Nanotechnology Letters., 10: 87–93. Wang, W., Zhang, Y., Zhao, J. (2018) Evolution of formation pressure and accumulation of natural gas in the Upper Palaeozoic, eastern-Ordos Basin, Central China. Geological Journal., 53: 395–404.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

A new method for judging the drilling mode of downhole instruments based on the giant magnetoresistance effect Yao Wu∗ , Hao Yang, Zhuoran Meng, Xiao Ma, Sijia Chen & Hongjiang Qin China National Logging Corporation, Xi’an Hi-tech Industries Development Zone, Shaanxi, China

ABSTRACT: Logging while drilling (LWD) refers to a logging method for measuring formation parameters during oil drilling. Measurement while drilling (MWD) mainly measures drilling engineering parameters. The drilling method of the downhole drilling tool determines the measurement while drilling. At present, the downhole rotation status of the instrument is mostly judged by the azimuth sensor and fluxgate, but the cost is high, the space is large, and it needs to be returned to the factory for calibration regularly. This paper proposes a new measurement method, which uses the characteristics of the output voltage change caused by the angle change between the giant magnetoresistive sensor and the geomagnetic field, and changes the angle information with the geomagnetic field into a voltage signal for measurement to realize the judgment of the drilling method. Measurement greatly reduces measurement cost and space occupied. The feasibility of the measurement method has been verified through experiments, and a new measurement method is provided for real-time status determination of downhole instruments. 1 INTRODUCTION Logging while drilling in the petroleum industry can be divided into logging while drilling (LWD) and measurement while drilling (MWD), which are used to measure the rock physical parameters and drilling engineering parameters of the formation (Zhang et al. 2006), respectively. The drilling condition of the downhole instrument determines the measurement method and upload parameters of the instrument. At present, the judgment of downhole drilling mode is realized by a fluxgate sensor in the directional pipe. By judging whether the instrument is compound drilling or sliding drilling, the rock physical parameters or engineering parameters can be switched and uploaded. However, the fluxgate sensor has a large volume, poor anti-interference ability, and needs to be returned to the factory regularly for calibration. The giant magnetoresistance effect (GMR) was discovered in Fe/Cr multilayer films by the physics research team of professor Fert (University of Paris, France) in 1988. The resistivity of GMR is greatly different with or without an external magnetic field, and even a slight change in a magnetic field can lead to a significant change in resistivity (Wang et al. 2020). GMR sensors have excellent temperature stability and high sensitivity with low power consumption and a small package. Currently, it is mainly applied to vehicle positioning of projectile body attitude, etc. (Hu & Yang 2003). In the oil drilling and production industry, the variation of output voltage due to the angle variation between GMR sensor and geomagnetic field can be used to measure the drilling status of downhole instruments. AAH002-02 is a giant magnetoresistance sensor developed by the NVE Company. It can measure the earth magnetic field with the characteristics of high sensitivity and low magnetic field measurement range (Wang et al. 2021). The measuring range of the device is -3GS ∼+3Gs (earth magnetic field range: +0.6gs∼-0.6gs), the resolution is 11mV/Gs∼18mV/Gs, the working voltage is 5V, and its internal structure is shown in Figure 1. In AAH002-02, there is a Wheatstone bridge ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003318569-15

85

composed of four GMR, which makes the magnetic sensitive direction of the sensor parallel to the direction of the magnetic field, that is, the included angle between the sensor and the magnetic field is 0. Only the magnetic field intensity is changed to make the magnetic field intensity change between 0∼+20Oe and 0∼ -20oe. Figure 2 shows the four measurement results at −40◦ C, 25◦ C, 85◦ C, and 125◦ C, respectively. The output voltage is always positive, and there is a positive correlation between the output voltage and the absolute value of the magnetic field. Due to the hysteresis phenomenon, the output voltage is slightly different in the process of increasing and decreasing the magnetic field intensity. Within the range of geomagnetic field intensity, the output voltage has an approximately linear correlation with magnetic field intensity as follows: Vout = kH + b

(1)

where H is the magnetic field intensity, and K and b are constants. The giant magnetoresistance sensor is directional (Li et al. 2010), and the magnetic field is parallel to the ground and always points north (Li et al. 2022) when sensor sensitive axis (magnetizing direction) and the earth’s North Pole Angle changes, giant magnetoresistance sensor sensitive axis direction of the magnetic field strength changes, lead to changes in the output voltage, so as to realize the downhole instrument to determine ways of drilling (Tan & Qia 2014).

Figure 1.

Schematic diagram of AAH002-02 internal structure.

Figure 2.

Output and temperature performance of AAH002-02 sensor.

2 CIRCUIT DESIGN AAH series devices provide full polarity output, along the sensitive axis of positive and negative changes in the voltage output. The hardware circuit design includes giant magnetic sensor AAH002-02, rail-to-rail highspeed comparator TS3021H, microprocessor MC9S08SG32, memory N25Q128A, power module TPS76901, and RS485 communication module SN65HVD11. After comparing the output of the GIANT reluctance sensor module with the rail-to-rail high-speed comparator, the comparator pushpull output signals of +5V or GND voltage for A/D sampling. The processing results are sent to the ON-chip AD of the MCU, and the converted results are stored. When the instrument is stationary, the output waveform is a straight line; when the instrument is rotating, the output waveform is a square wave (Li et al. 2021). The hardware circuit structure is shown in Figure 4. 86

Figure 3. AAH002-02 sensor sensitive axis direction.

Figure 4.

Hardware circuit structure.

Since the memory needs a 3.3V power supply and the other modules need a 5V power supply, 5V is input externally, so the conversion from 5V to 3.3V and the voltage isolation between the memory and MCU are key. TPS76901HDBVT from the traditional PNP transmission transistor into PMOS, PMOS transmission resistance is very small, so the pressure difference is very low (Li et al. 2020; Xiao et al. 2001). A voltage of 1.7V or higher on the EN input will disable the TPS76901 internal circuit, thereby reducing the power current by 1µA. A voltage lower than 0.9V at the EN input will restore TPS76901 to normal operation. EN Input The actual switchover threshold is about 1.5 V. A 1µF ceramic input bypass capacitor, connected between pin IN and GND, is located near TPS76901 to improve transient response and noise suppression. The hardware circuit is shown in Figure 5:

Figure 5. Voltage conversion module.

The internal reference voltage can be calculated as: Vref = 1.16V

(2)

R1 and R2 have about 7uA partial voltage current, and the resistance value should not be too small. A high resistance value should also be avoided, otherwise, the current added to negative feedback will increase the error of output voltage (Lu, Wu, Chen, et al 2021). Therefore, IT is recommended to select R2 = 169K.   V0 − 1 ∗ R2 (3) R1 = VREF All low-voltage differential regulators require an output capacitor to be connected between OUT and GND to stabilize the internal control loop, with a recommended minimum of 4.7uF. Capacitors should have ESR between 0.2 and 10 to ensure stability and improve transient response 87

and noise suppression. One can choose solid tantalum electrolytic capacitors, aluminum electrolytic capacitors, and multilayer ceramic capacitors. This paper uses a solid tantalum electrolytic capacitor. The voltage isolation chip adopts MC74VHC1GT125, and the schematic diagram is shown in Figure 6.

Figure 6. Voltage isolation module.

3 EXPERIMENTAL VERIFICATION The installation direction of the AAH002-02 sensor on the printed circuit board is shown in Figure 7. The printed board is placed on the instrument framework. When the instrument is perpendicular to the ground and applied to the vertical well, the standard sensitive axis is parallel to the direction of the geomagnetic field, and the initial position differs 180◦ C from the direction of the sensitive axis (S U N et al. 2021). When the instrument does not rotate, Uout , Uout+ , and Uout− are constants, and the output waveform of the comparator is 0. The instrument was perpendicular to the ground plane, then rotated 360◦ C, and the measured voltage of Uout- and Uout+ are shown in Table 1. The test conditions were as follows: latitude 34◦ C 13 49 N, longitude 108◦ C 58 9 E, altitude 418.7m, and air pressure 968.5hPa. The installation mode and initial orientation of the sensor are shown in Figure 7.

Figure 7.

Installation mode and initial position diagram of the instrument perpendicular to the ground.

Table 1. Voltage output table of the angle between the instrument and the geomagnetic field when it is perpendicular to the ground. location

output voltage (V)

Uout+ (V)

Uout− (V)

location

output voltage (V)

Uout+ (V)

Uout− (V)

N0◦ N10◦ N20◦ NE30◦ NE40◦ NE50◦ NE60◦ NE70◦ E80◦

0.004 0.004 0.004 0.004 unstable 5.004 5.004 5.044 5.044

2.5255 2.5258 2.5262 2.5270 2.5281 2.5297 2.5314 2.5332 2.5354

2.5314 2.5311 2.5306 2.5299 2.5287 2.5272 2.5258 2.5242 2.5223

S190◦ S200◦ WS210◦ WS220◦ WS230◦ WS240◦ W250◦ W260◦ W270◦

5.044 5.044 5.004 5.044 5.004 5.004 5.004 5.004 5.004

2.5511 2.5506 2.5486 2.5481 2.5467 2.5450 2.5426 2.5412 2.5385

2.5067 2.5072 2.5082 2.5097 2.5110 2.5128 2.5153 2.5166 2.5194 (continued)

88

Table 1. Continued. location

output voltage (V)

Uout+ (V)

Uout− (V)

E90◦ E100◦ E110◦ ES120◦ ES130◦ ES140◦ ES150◦ S160◦ S170◦ S180◦

5.044 5.044 5.044 5.044 5.044 5.044 5.044 5.044 5.044 5.044

2.5378 2.5398 2.5424 2.5445 2.5464 2.5482 2.5495 2.5505 2.5512 2.5514

2.5199 2.5178 2.5152 2.5131 2.5112 2.5094 2.5082 2.5072 2.5066 2.5063

W280◦ W290◦ WN300◦ WN310◦ WN320◦ WN330◦ N340◦ N350◦ N360◦

output voltage (V)

Uout+ (V)

Uout− (V)

5.004 5.004 5.004 5.004 0.006-0.008 0.004 0.004 0.004 0.004

2.5359 2.5336 2.5315 2.5297 2.5283 2.5272 2.5265 2.5263 2.5261

2.5220 2.5241 2.5260 2.5274 2.5289 2.5301 2.5307 2.5310 2.5308

The instrument outputs voltages Uout+ and Uout− that are perpendicular to the ground plane are shown in Figure 8. The output differential voltage Uout is shown in Figure 9. At this time, the comparator output waveform is shown in Figure 10:

Figure 8. Voltage output curve when the instrument is perpendicular to the ground.

Figure 9.

Differential voltage output curve when the instrument is perpendicular to the ground.

When the instrument rotates, the magnetic field in the direction of the sensitive axis is: Hβ = H cos β

(4)

Where Hβ refers to the intensity of the sensitive axis magnetic field when the sensitive direction of the sensor is at an angle β with the positive direction of the magnetic field, and H is the intensity of the geomagnetic field. According to the output characteristics of AAH002-02, the output voltage should have an approximately linear relationship with the intensity of the magnetic field. 89

Figure 10.

Comparator output voltage when the instrument is perpendicular to the ground.

When the instrument is perpendicular to the ground plane, the duty ratio of the output voltage is about 0.72T, where T is the time for the instrument to rotate 360◦ . The instrument rotates once, and the number of positive pulses is 1. According to the number of pulses, the speed of the instrument in a certain time can be calculated. When the instrument and surface water level, considering the sensitivity of device measurement, the sensor is installed at 90◦ with the printed board, and the sensitive axis is parallel to the direction of the geomagnetic field. The installation mode is shown in Figure 11.

Figure 11.

Sensor installation mode and initial position diagram.

When the instrument rotates 360◦ horizontally on the ground, the output voltage Uout+ and Uout- are shown in Figure 12, the output voltage differential voltage Uout is shown in Figure 13, and the output waveform of the comparator is shown in Figure 14.

Figure 12. Voltage output curve of the instrument at ground level.

Figure 13.

Differential voltage output curve when the instrument is horizontal on the ground.

90

When the instrument rotates, the magnetic field in the direction of the sensitive axis is: Hβ = H sin β

(5)

where Hβ refers to the intensity of the sensitive axis magnetic field when the sensitive direction of the sensor is at an angle β with the positive direction of the magnetic field, and H is the intensity of the geomagnetic field. According to the output characteristics of AAH002-02, the output voltage should have an approximately linear relationship with the intensity of the magnetic field. It should be noted that the relationship is not linear, but approximately ternary function relation, which may be due to its voltage range being larger relative to the vertical direction, has been out of the limitation of the linear region.

Figure 14.

Comparator output voltage when the instrument is level at ground.

When the instrument is level, the duty ratio of the output voltage is about 0.61×T. The ground can judge the instrument rotation and calculate the speed after receiving the waveform. 4 CONCLUSION The giant magnetoresistance sensor can measure the rotating state of the instrument, and the rotational speed of the instrument can be calculated by calculating the duty ratio of the output voltage of the comparator. The small package giant magnetoresistance sensor can greatly save the space occupied by the downhole instrument to measure the rotating state of the instrument. When the instrument is perpendicular to the ground, the output voltage of the sensor changes according to the approximate cosine law. When the instrument is horizontal to the ground, the output voltage of the sensor changes according to the approximate sine law, which is mainly caused by the change of the angle between the sensitive axis and the geomagnetic field. ACKNOWLEDGMENT This research is supported by China National Petroleum Corporation (CNPC) Project “Development of High Temperature and High-Pressure Imaging Logging Instrument while Drilling” [2021DJ3902] and the China National Logging Corporation Project “Independent Development of Electromagnetic Wave LWD Mechanical and Electrical Components” [ZZKY2021-04]. REFERENCES Li Y, Wang S, Yang Y, et al. Multiscale symbolic fuzzy entropy: An entropy denoising method for weak feature extraction of rotating machinery[J]. Mechanical Systems and Signal Processing, 2022, 162: 108052. Li Y, Wang S, Li N, et al. Multiscale symbolic diversity entropy: a novel measurement approach for time-series analysis and its application in fault diagnosis of planetary gearboxes[J]. IEEE Transactions on Industrial Informatics, 2021.

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LiY, Du X, Wan F, et al. Rotating machinery fault diagnosis based on convolutional neural network and infrared thermal imaging[J]. Chinese Journal of Aeronautics, 2020, 33(2): 427–438. Lu C, Wu M, Chen L, et al. An event-triggered approach to torsional vibration control of the drill-string system using measurement-while-drilling data[J]. Control Engineering Practice, 2021, 106: 104668. N. Tan, Z, Qia. “Development of comprehensive Characteristics Test Device for Giant Magnetoresistance Sensor,” Electrical Measurement and Instrumentation. 2014.12 Qifeng S U N, Na L I, Youxiang D, et al. Logging-while-drilling formation dip interpretation based on long short-term memory[J]. Petroleum Exploration and Development, 2021, 48(4): 978–986. S. Hu, W. Yang. “Current situation and the prospect of giant magnetoresistance applications,” Journal of Qingdao University. 2003.3 Wang X, Si S, Li Y. Multiscale diversity entropy: a novel dynamical measure for fault diagnosis of rotating machinery[J]. IEEE Transactions on Industrial Informatics, 2020. Wang X, Si S, Li Y. Variational embedding multiscale diversity entropy for fault diagnosis of large-scale machinery[J]. IEEE Transactions on Industrial Electronics, 2021. W. Li, Z. Xie, Y. Yang. “Research progress of Giant magnetoresistance effect in thin films,” Materials Guide.2010.8. X. Zhang, J. Wang, Y. Guo. “Progress and Development Trend of Logging While Drilling technology,” Logging Technology. 2006.2 Y. Xiao, R. Zeng, L. Wang. “Application of giant magnetoresistance sensor”. Magnetic materials and devices. 2001.4.

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Analysis on the feasibility of applying inflow performance regulating device to low permeability horizontal wells Yongjie Zhou No.5 Oil Production Plant of Daqing Oilfield Company, Daqing, China

ABSTRACT: With the continuous development of fine potential tapping technology, the recovery of many low-permeability oilfields has reached 40-60%. In order to further improve the recovery, the horizontal well development method has become a more economical choice. As the horizontal well development method has the characteristics of more penetrating oil layers, being close to the top of oil layers, a higher input-output ratio than vertical wells, and good economic benefits, it can economically and efficiently tap the potential and develop the remaining oil in the block. However, there are still some problems, such as a great difference in flow efficiency between the root and toe of the horizontal section, serious bottom water coning, and a great difference between inflow performance and ideal state; in order to solve the above problems and improve the productivity of horizontal wells, the feasibility of applying inflow performance regulation device in low permeability horizontal wells is analyzed. Technically, through the application of an inflow performance regulating device, the flow resistance of liquid at the root of a horizontal section of the low-permeability horizontal well can be significantly increased, and the flow efficiency between toe and root can be adjusted to achieve balance or close to balance. In terms of economic benefits, reducing the impact of root fluid inflow on the toe can improve the toe fluid inflow capacity, achieve the goal of increasing root inflow resistance and improving the productivity of the whole well, and provide new means and experience for improving the production of horizontal wells.

1 INTRODUCTION At present, the recovery efficiency of many Low-permeability Oilfields has been close to 40-60%. Vertical well mining is facing the current situation of high water cut, high cost, and low benefit (two high and one low). In order to further improve crude oil recovery and oilfield development efficiency, horizontal well development has become a more economical choice. Horizontal well development has the characteristics of more penetrating oil layers, close to the top of oil layers, and a higher input-output ratio than vertical wells. It has good economic benefits, can solve the problem of two high and one low faced by vertical well development, and can economically and efficiently tap the remaining oil in the development block. However, we still face the following problems. First, although the horizontal well penetrates the reservoir as much as possible, there is a great difference in flow efficiency between the root and toe of the horizontal section, and 75% of the production capacity comes from the root of the horizontal well; second, although the horizontal well trajectory is as close to the top of the reservoir as possible, the problem of bottom water coning is still serious; third, generally, the actual wellbore trajectory of a horizontal well is not absolutely horizontal, but wavy. When the wellbore is bent greatly, the inflow performance of a horizontal well is greatly different from that of an ideal horizontal well due to gravitational potential energy; to solve the above problems, the feasibility of using an inflow performance regulation device in horizontal wells of low permeability reservoir is analyzed. The application of an inflow performance adjustment device can significantly increase the inflow resistance of liquid at the root of the horizontal section, adjust the inflow performance between toe and root, balance the flow efficiency between toe and DOI 10.1201/9781003318569-16

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root of a low-permeability horizontal well, and make it reach equilibrium or close to equilibrium. By reducing the influence of root liquid inflow on the toe, the liquid inflow capacity of the toe can be improved, the goal of increasing inflow resistance and single well productivity can be achieved, and new means and experience can be provided for improving single well productivity of horizontal wells (Karen 2007).

2 PROCESS PRINCIPLE In order to balance the inflow performance of horizontal sections, improve the productivity of a single well, prolong the effective production period, and finally achieve the goal of improving reservoir recovery and developing economic benefits, oil production engineers and technicians have developed inflow performance regulation device. At present, it has been widely used in reservoirs with good geological conditions and achieved good results. The design idea is to increase the annular flow channel in the process of the produced fluid entering the casing so that the fluid in the formation can increase the friction resistance through the annular flow channel and balance the pressure system inside the wellbore. The radius, length, and other specifications of the annular channel can be adjusted according to the design to form the required pressure drop value, increase the flow from the formation into the wellbore and improve the single well productivity of horizontal wells. At present, the commonly used inflow dynamic regulating devices are mainly divided into three types: runner type, nozzle type, or eyelet type (Liu 2004). 2.1 Runner type The channel type inflow dynamic regulating device has a spiral annular channel structure. The annular channel produces a certain friction resistance to the oil and gas fluid. The formationproduced fluid enters the annular channel through the screen and flows into the central pipe after passing through the small channel of the design length. When it is inside the (wellbore), it produces a large pressure drop loss, so that the pressure at the root of the horizontal section inside the wellbore is lower than that at the toe, reducing the impact on the liquid inlet at the toe (Figure 1).

Figure 1.

Spiral channel type inflow dynamic regulating device.

Compared with nozzle type and eyelet type, the structural design of channel type can maintain the pressure drop of the liquid inlet at the root for a long time, which has the advantage of reducing the possibility of erosion and blockage at the inlet of the dynamic regulating device; The disadvantage is that it is highly sensitive to velocity, and the pressure drop caused by friction in the annular channel will be different due to different liquid flow rates. Therefore, in actual production, a relatively constant recovery rate should be maintained as far as possible (Zhao 2003). 2.2 Nozzle type The principle of the nozzle type inflow dynamic regulating device (Figure 2) is to generate pressure drop through the nozzle. The formation-produced liquid enters the cavity of the regulating device after passing through the screen. A nozzle for fluid to pass through is arranged in the cavity, and 94

the fluid enters the center tube through the nozzle. The diameter of the nozzle can adopt different specifications according to the corresponding pressure drop generated by the predicted produced fluid flow rate. The device is characterized in that the pressure drop generated by the fluid flow through the nozzle is seriously affected by the fluid density and velocity, and is less sensitive to the fluid viscosity. The disadvantage is that a high flow rate is easy to cause tool corrosion, especially when the produced fluid contains sand. Therefore, it is recommended to use the device together with a sand control screen in actual production, and control the produced fluid speed of horizontal wells.

Figure 2.

Nozzle type inflow dynamic regulating device.

2.3 Eyelet type The orifice type inflow dynamic regulating device (Figure 3) adopts the mode of multi holes in parallel to generate the required differential pressure, so as to achieve the goal of flow efficiency balance. Each inflow dynamic regulating device is composed of a large number of orifice plates with preset radius specifications. Contrary to the structure of the nozzle type inflow dynamic regulating device, the hole of the device is on the central tube in the cavity. This process realizes different pressure drop values by reducing the number of openings. Although the exact position of the eyelet is different from the nozzle type inflow dynamic regulating device, its principle is basically the same, and the fluid characteristics, advantages, and disadvantages are basically similar to the nozzle type regulating device.

Figure 3.

Eyelet type inflow dynamic regulating device.

3 FEASIBILITY ANALYSIS Taking the hole type inflow performance regulating device as an example, it is theoretically analyzed that under the conventional completion mode, the root of the horizontal well is the main liquid supply area, and the toe is seriously affected by friction. The pressure drop caused by the perforation when the local formation fluid flows through the perforation and enters the casing  P0 ≈  P1≈  P2 ≈  P3 (Figure 4), and the formation pressure P of the four sections in the horizontal well section is basically equal. When there is no suction (i.e., after shutdown and stability), P0 ≈ P1 ≈ P2 ≈ P3, the fluid in the third and fourth sections of the horizontal section will not flow to the bottom of the well without differential pressure; under the action of the oil well pump, the pressure of p-well 95

decreases, and the fluid in the wellbore continuously flows to the bottom of the well from the first and second sections. The differential pressure is generated at P0 and P1 because the fluid flows to the bottom of the well. Under the action of the differential pressure, the formation continuously flows out, and the fluid in the third and second sections continuously flows to P1, P0 and the bottom of the well; however, from the numerical analysis, when the friction resistance of the fluid in the third and fourth sections is greater than or equal to the pressure difference between the formation and P1 and P0  P0,  P1, the flow into the bottom hole under the action of friction resistance will be far lower than the liquid supply of the formation; only in terms of frictional resistance and differential pressure  P0,  when the difference between P1 is large, the fluid flow will be close to our expectation due to the influence of friction resistance; however, in fact, because the horizontal section is often long and the well trajectory is not an ideal horizontal state, there is a great difference between the inflow performance at the bottom of the well and the ideal horizontal well state due to the influence of friction resistance and gravity potential energy. This is also the case in the actual test. T oilfield is a thin oil-bearing layer with a thickness range of 4–27 m. It has not only an overlying gas cap but also a bottom water layer. Through economic evaluation, there is no economic benefit in using a vertical well to exploit such a thin reservoir. Later, two horizontal wells a and B were drilled with good productivity. The production profile logging analysis is carried out in test well a, and the result is that 75% of the productivity comes from the first half of the horizontal section, that is, 3 / 4 of the productivity comes from the root of the horizontal section, and the productivity of the second half (i.e., the toe of the horizontal section) only accounts for 25% of the productivity of the whole well under similar geological conditions and perforation length. Therefore, it is necessary to apply the completion device to improve the productivity of a single well in low permeability horizontal wells.

Figure 4.

Bottom hole pressure after conventional well completion.

The problem of inflow dynamic imbalance can be solved through the “stepped” arrangement, that is, during well completion, the regulating device with the maximum strength is installed in the first section of the horizontal section, the regulating device with the lower strength is installed in the second section, the device with the minimum strength is installed in the third section, and the fourth section is completed and perforated by the conventional casing. After applying the regulating device, the pressure drop of fluid entering each section is different and arranged in steps ( P0>  P1>  P2>  P3). Under the combined action of suction and continuous liquid supply from the formation, the pressure of each section in the horizontal section is also in a stepped arrangement from the root to the toe (P0 < P1 < P2 < P3). Under the action of differential pressure, the fluid at the toe of the horizontal section will continue to flow to the root (Figure 5). Under ideal conditions, the latter half of the well can release three times the original production capacity, that is, the production capacity of the whole well can be increased by 50%. Even if the full oil increase effect cannot be achieved, the cumulative oil increase of a single well will increase when the differential pressure becomes larger. It has obvious technical advantages in oil increase effect (Wang 2013). For sand producing wells, the inflow performance regulating device can be used together with the sand filter pipe; meanwhile, in the actual construction process, in order to simplify the construction 96

procedure, the regulating device at the root of the horizontal section can be designed as a unified strength, and the regulating device is not installed at the toe of the horizontal section. On a horizontal well in Z oilfield, four-channel type regulating devices with the same strength are used for cementing and completion of a 671m long well section. Compared with the surrounding produced wells completed by conventional cement cementing and perforation completion, the well has higher productivity and an obvious balance of liquid injection.

Figure 5.

Schematic diagram of bottom hole pressure after well completion with regulating device.

Through the above analysis, it is considered that the application of regulating devices in horizontal wells of low permeability oilfields is feasible in technology and economy.

4 CONCLUSION AND UNDERSTANDING First, horizontal wells have higher economic benefits than vertical wells in low permeability oilfields but are affected by friction resistance, gravity potential energy, and other factors. There are some problems, such as unbalanced flow efficiency, and a large gap between actual production and expectation, etc. Second, the application of the regulating device can effectively adjust the inflow performance difference between the toe and the root, balance the flow efficiency between the toe and the root of low-permeability horizontal wells, make them reach equilibrium or close to equilibrium, and improve the liquid inflow capacity of the toe and the productivity of single wells. Third, the application of regulating devices in horizontal wells in low permeability oilfields can achieve the goal of increasing inflow resistance and increasing single well productivity and provide new means to improve the production of horizontal wells and support for the economic and effective development of low permeability oilfields.

REFERENCES Karen Bybee. Inflow control devices. Spe. 2007. International oil conference and Exhibition Liu Shanzhen and Gu Zude. Large displacement downhole casing technology and development direction. Technology and equipment. 2004 Wang Dawei, Li Xiaoping. Influence of good trajectory on inflow performance of horizontal wells. Lithologic oil and gas reservoirs. Issue 3, 2013 Zhao Xu, Yao Zhiliang, Liu huanle. Study on design method of horizontal well flow regulation and water control screen completion. Petroleum drilling and production technology. Issue 1, 2003

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Risk evolution analysis of chemical laboratory poisoning accident based on complex network Yudie Chang, Mingguang Zhang∗ , Xingmin Cui, Yifan Lu, Ziwei Yi & Chongqing Liang College of Safety Science and Engineering, Nanjing Tech University, Nanjing, Jiangsu, China Jiangsu Key Laboratory of Hazardous Chemicals Safety and Control, Nanjing, Jiangsu, China

ABSTRACT: In order to solve the problem of laboratory safety, a quantitative assessment method of laboratory poisoning accident risk evolution was proposed based on complex network theory and risk uncertainty. According to the laboratory operation process, the complex network evolution model of the poisoning accident scene was constructed to judge the clustering of nodes. In view of the randomness and fuzziness of risk transfer, edge weights are introduced to represent the uncertainty. The expression of the maximum possibility of the risk transmission path is given, and the accident’s shortest path is obtained by the Dijkstra algorithm. The results show that the clustering coefficient of the complex network of laboratory poisoning accidents is 0.120, and the node aggregation degree is low but the evolution is strong, which has the characteristics of the small-world network. The risk transmission path that directly affects laboratory equipment and facilities as the initial event has the greatest influence on poisoning accidents. However, all the initial events can lead to poisoning accidents after a few steps of transmission, which verifies the feasibility of this method in the semi-quantitative risk assessment of complex process systems.

1 INTRODUCTION With the rapid development of the chemical industry, scientific research institutions, and higher education, the number of chemical laboratories of various types keeps increasing. However, various accidents keep happening, causing casualties and property losses. A chemical laboratory is a relatively dangerous area due to its compact space and various kinds of toxic and harmful substances. In addition, many laboratory staff lack safety awareness, equipment aging, dangerous chemical management disorder, and other potential factors seriously threatening the safety of teachers, students and staff. On March 27, 2017, a chemical reactor exploded in a laboratory in the Chemistry Department of Fudan University, injuring a boy’s arms. On December 26, 2018, three students at Beijing Jiaotong University were killed in an explosion while conducting an experiment on leachate wastewater treatment. Laboratory accidents bring varying degrees of negative impact on individuals, schools, and society. Therefore, it is of great engineering significance to study the influencing factors and evolution of laboratory accidents. As for laboratory risk assessment, Peiyi Wang (Wang 2006) showed that the storage of hazardous chemicals in most laboratories in China could not meet the conditions of professional storage places, and a variety of hazardous chemicals would be involved in accidents. Pietro Apostoli et al (Apostoli 1996) established an evaluation method with steps including risk identification, risk classification of chemical substance updating, evaluation of variables that may lead to an explosion, and quantification of explosion risk. Norafneeza et al (Norazahar 2012) believed that operational guidance and rules and regulations were very important in chemical laboratories, and adopted Lab-Arbais to monitor and control the risky behaviors of students in laboratories. Boutskou et al (Boutskou 2008) evaluated the safety awareness level of students and staff in chemical laboratories ∗ Corresponding Author:

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[email protected]

DOI 10.1201/9781003318569-17

through a questionnaire survey, and then evaluated the safety level of laboratories based on the safety awareness and overall quality of staff. Kaufman James (James 1992) emphasized the differences between hazardous chemical laboratories and other workplaces and the necessity of different safety requirements. Joseph M. Crockett (Crockett 2011) described that students must pass relevant tests before using the laboratory, so as to reduce the possibility of accidents when using the laboratory. There are few types of research on the mechanism of accident risk coupling. A chemical laboratory is a complex and open system with a large number of personnel, complex equipment, and exploratory and uncertain experimental activities. Accidents are mostly caused by the interaction and coupling of different risk factors. In addition, according to the statistical results of related accidents (He 2017; Li 2014), among all kinds of laboratory accidents, poisoning accidents do not take up a high proportion of occurrence frequency but cause the most casualties. Therefore, this paper introduces complex network theory to study the coupling mechanism of laboratory poisoning accidents, explores the development process of poisoning accidents, and excavates the accident evolution law.

2 METHODS OF COMPLEX NETWORKS Complex network theory has been applied in many fields (Deng 2015; Liu 2012), which can deepen people’s understanding and understanding of the evolution of the internal structure of complex systems, fully demonstrate the coupling mechanism of the cause of laboratory poisoning accidents, and is suitable for exploring the coupling law of the cause of accidents. The main characterization parameters of the system complex network are as follows (Wu 2016). 2.1 Characteristic indicators of complex networks 2.1.1 The degree of node The degree Ki f node i in an undirected network is the number of other nodes directly connected with node i, and the number of edges is directly connected with i. If a node in the network has a larger degree value, it indicates that the node is in the core position in the network. Degree K of node i is xpressed by the formula:

(1) aij ki = j

Where: aij is the number of connecting edges between node Vi and node Vj . The greater the degree is, the more important the node is in the network. 2.1.2 Clustering coefficient The clustering coefficient refers to the proportion of interconnected nodes adjacent to a node, which reflects the aggregation of nodes in the local network. The clustering coefficient of node Vi is: Ci =

2Li n (n − 1)

(2)

Where n is the total number of nodes adjacent to node Vi ; Li is the actual number of edges connected between n adjacent nodes. The clustering coefficient C of the whole system is: 1 Ci N i=1 N

C=

(3)

N is the total number of nodes, and the larger the value of C is, the greater the degree of short-distance connection will be formed in the whole network. 99

2.1.3 The shortest path One of the purposes of complex network operation is to find the fastest way to cause the result event, namely the shortest path. However, the network linkage graph cannot be calculated directly and needs to be converted into a weighted directed graph. After transformation, the directed graph is composed of nodes and weighted edges, where the weighted edge represents the degree of difficulty that the previous event causes the subsequent event in the network. Therefore, the key to shortest path calculation lies in the transformation of graphs and the setting of weights, namely: G = (V, E, W)

(4)

V={V1 , V2 , V3, …, Vn }, a collection of initial events, transfer events, and result events; E={e1 , e2 , e3 , …, en }, the edge set between node events; W is the set of edge weights. The shortest path length between node Vi and node Vj is called the distance between nodes, denoted as d(i, j). 3 EVOLUTIONARY MODEL OF POISONING RISK 3.1 Material of risk list The node of the laboratory dangerous chemical poisoning accident risk evolution model is derived from risk events. Based on the collation and analysis of the existing poisoning accident-related data, the risk and operable analysis method is used to identify the accident cause events and build the accident risk list. Laboratory poisoning accidents are mostly caused by hazardous chemicals, while most of them are caused by unsafe behaviors such as illegal operation and error of operators. Based on the above risk identification, the risk factors affecting poisoning accidents are divided into 19 risk events, as shown in Table 1. Table 1. Risk factors of poisoning accidents. Event number

meaning

Event number

V1

Lack of safety management system

V11

V2

The main responsibility of production safety is not clear The safety level of employee participation is not high Lack of education and training system

V12

V3 V4

V13 V14

V5 V6

The emergency rescue system is lacking The hidden trouble investigation and rectification system is deficient

V15 V16

V7

Lack of safety knowledge

V17

V8

Organizational laws and regulations are not complete

V18

V9 V10

Safety awareness is not high Work without wearing safety equipment

V19

meaning Non-compliance with operating procedures Not familiar with process control index The management personnel command in violation of regulations Key supervisory process units are not automated The equipment is not repaired regularly Do not wear special protective equipment to engage in hazardous operations in a toxic or harmful environment Perform dangerous operations in toxic, harmful, or corrosive media without wearing special protective equipment Oxygen content and toxic gas concentration were not analyzed before entering restricted space operation Poisoning choke

3.2 Complex network modeling of laboratory poisoning process Complex networks are between the regular grid and the random network (Erd 2011), chamber poisoning accident factors in the chain of the node in the network, the interaction relationship 100

between hazard or accident as a network of edge. The causal relationship is between the factors as the direction of the edge between nodes, according to the influence of the relationship between events. Risk factors are established between the evolution of the structural model, and the directed network diagram is shown in Figure 1. The evolution model contains 19 nodes and 31 edges, representing the risk events and evolution relationship and the corresponding risk transfer chain. Among them, the safety management system lacks full production, the main body of responsibility is not clear, member participation in safety degree is not high for the initial event, laboratory poisoning for the end of the event, and the rest for risk transfer events.

Figure 1.

Laboratory poisoning risk evolution linkage model and shortest path diagram.

4 UNAUTHORIZED DIRECTED NETWORK ANALYSIS 4.1 Degree of analysis The degree of influence of risk events on subsequent events depends on their out-degree. The greater the out-degree, the greater the degree of influence on subsequent events. The in-degree represents the number of paths leading to the occurrence of the event. The greater the in-degree, the more paths leading to the event, and the difficulty of control will increase accordingly. According to Figure 1, out-degree and in-degree respectively refer to the total number of arrows pointing and pointing at-risk events. The out-degree and in-degree of each risk event are shown in Table 2. Table 2. Unauthorized digraph analysis results. Node number

Outdegree

Indegree

Degree

Clustering coefficient

Node number

Outdegree

Indegree

Degree

Clustering coefficient

V1 V2 V3

3 3 3

0 0 0

3 3 3

0 0.33 0.67

V11 V12 V13

2 3 1

2 1 1

5 4 2

0.33 0 0 (continued)

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Table 2. Continued. Node number

Outdegree

Indegree

Degree

Clustering coefficient

Node number

Outdegree

Indegree

Degree

Clustering coefficient

V4 V5 V6 V7 V8 V9 V10

2 1 1 2 1 2 2

1 1 2 2 1 3 1

3 2 3 4 2 5 3

0 0 0.33 0.17 0 0.1 0

V14 V15 V16 V17 V18 V19

1 1 1 1 1 0

1 2 3 3 3 3

2 3 4 4 4 3

0 0.33 0 0 0 0

4.2 Countermeasure analysis of the degree As can be seen from Table 2, the lack of a safety management system, the unclear responsibility of safety production subjects, and the unfamiliarity with process control index events have a large incidence, that is, they have a wide impact on subsequent events. Safety awareness is not high, do not wear special protective equipment to engage in toxic and harmful dangerous operations and other events; there are many ways to cause this event, and the cause of poisoning is more direct and difficult to control; overall, the degree of all risk nodes, such as low safety awareness, noncompliance with operation procedures, and unfamiliar with process control indexes, exceeds 4, indicating that there are a large number of other nodes connected to these nodes, that is, they have a large interaction with other risk factors, which is the key factor affecting poisoning accidents. The laboratory should pay attention to the establishment of the responsibility system, top-down layer planning, clear definition of each level of responsibility and rights, so as to achieve “vertical to the end, horizontal to the edge, seamless docking”; It is required to conduct safety education and training for experimental personnel, improve their safety knowledge level, safety prevention, and control awareness, and enhance their safety participation; before entering toxic and harmful gas space, a safety risk assessment and wear corresponding safety protective equipment is conducted. 4.3 Analysis of clustering coefficient and countermeasures In order to clearly indicate the occurrence sequence of events, all risk events are divided into 3 levels according to the analysis of access degree. The event with zero entry degree is the initial event as level 1, the event at the top of the model is the laboratory poisoning event as level 3, and the risk transmission event as level 2. According to Formula (2), the clustering coefficients of each node are shown in Table 2 after calculation. Where: The clustering coefficient of all first-level events is 0, indicating that as the initial node, the interaction between the next-level risk events triggered is small; in the secondlevel events, the clustering coefficients of the events such as the lack of hidden trouble investigation and rectification system, the lack of safety knowledge, and the equipment not regularly repaired are relatively high, indicating that these events are closely connected to the event group. From the perspective of inhibiting risk transmission, perfecting the hidden trouble investigation and rectification system, checking and maintaining the equipment regularly, and wearing special safety protection equipment according to the provisions are effective means to cut off the transmission of fire poisoning risk; the third-level event, laboratory poisoning, had a cluster coefficient of 0, indicating that the direct causes of the final outcome were not closely related. The comprehensive clustering coefficient of the risk evolution network of laboratory poisoning accidents was calculated by Formula (3) as C=0.12, indicating that in the whole complex network, the causes leading to the final events were complex, but the correlation between most of the risk events was not obvious, but there was a significant transfer relationship. The occurrence of laboratory poisoning can be controlled by means of chain-breaking control and evolutionary path cutting. 102

5 EVOLUTION ANALYSIS OF WEIGHTED DIRECTED NETWORKS The process of accident development is accompanied by the transition of node risk state, and the difficulty of transmission is reflected in the edge weight W of a complex network. The edges in the evolution model in FIG. 1 are weighted and transformed into a weighted directed network. The edge weight E is assigned with reference to the weight standard in reference (Guo 2012), and {1, 3, 5, 7, 9, ∞} respectively represent the occurrence of the former node and the occurrence of the latter node {definitely, extremely likely, possibly, not easily, extremely difficult, impossible}. According to the digraph calculation method of Dijkstra (Xu 2004), if the node-set (V1 , V2 …, Vn−1 , Vn ) is the shortest, it is needed to make (V1 , V2 …, Vn−1 ) the shortest path, that is, all transmission paths are guaranteed to be shortest. Starting from the initial events V1 , V2 , V3 , and V4 , this method is used to get their respective shortest paths (maybe more than 1). Table 3. Edge weights. Edge

Code name

Weight

Edge

Code name

Weight

Edge

Code name

Weight

V1 –V8 V1 –V4 V1 –V6 V2 –V6 V2 V15 V2 V5 V3 –V9 V3 –V11 V3 –V7 V4 –V9 V4 –V7

e1 e2 e3 e4 e5 e6 e7 e8 e9 e10 e11

5 3 3 5 5 5 3 5 5 3 3

V5 –V13 V6 –V15 V7 –V12 V7 –V11 V8 –V9 V9 –V10 V9 –V11 V10 –V16 V10 –V17 V11 –V17 V11 –V16

e12 e13 e14 e15 e16 e17 e18 e19 e20 e21 e22

5 3 3 3 7 3 3 1 1 3 3

V12 –V18 V12 –V16 V12 –V17 V13 –V18 V14 –V12 V15 –V14 V16 –V19 V17 –V19 V18 –V19

e23 e24 e25 e26 e27 e28 e29 e30 e31

5 3 3 5 5 5 3 3 5

The bold lines in Figure 1 are the shortest paths of each initial event, and the specific paths are shown in Table 4. Table 4. Shortest path for each initial event. The initial event

The shortest path

Distance d (I, j)

V1 V2 V2 V3

V1 –V4 –V7 –V12 –V16 (V17 )–V19 V2 –V5 –V13 –V18 –V19 V2 –V15 –V14 –V18 –V19 V3 –V9 –V10 –V16 (V17 )–V19

15 20 20 10

According to Table 4, the initial event with V3 employees’ low participation in safety has the shortest evolution path, followed byV1’s lack of a safety management system, andV2 has the longest evolution path with unclear responsibility of safety production subjects. This is because the responsibility of the main body of production safety is not clear. The impact on the whole system is indirect, and the impact on the occurrence of accidents is relatively hidden, while other initial events have a more direct impact on the system. However, on the whole, each initial event can lead to the occurrence of poisoning accidents after a few steps of transmission, showing obvious small-world network characteristics (Watts 1998). From the perspective of risk transfer chain control, establishing and perfecting the laboratory safety responsibility system, cultivating the safety responsibility consciousness of employees, improving the safety participation degree of employees, perfecting the hidden trouble investigation and management system, checking equipment and facilities regularly, and ensuring adequate professional protective supplies are important means to prevent laboratory poisoning accidents. 103

6 CONCLUSION 1) Based on the historical data and expert comments on laboratory poisoning accidents, the evolution network model of laboratory poisoning accidents was constructed according to the evolution mechanism of disaster events. Based on the complex network theory, the key links affecting laboratory poisoning accidents were revealed from the global perspective, and the control measures of chain-breaking were put forward. 2) The average clustering coefficient of the complex network of laboratory poisoning accidents is 0.120, and the clustering degree of nodes is low, indicating that the network has significant evolution and transitivity. By reducing the node event risk and cutting off the accident transmission chain, the initial event can be effectively prevented from escalating to a serious poisoning accident. 3) This method uses the Dijkstra algorithm to search the shortest path of the fault and identify the most likely failure mode of the system formed by multiple nodes. The results show that low employee participation is the shortest path leading to poisoning accidents. 4) The risk evolution assessment method of poisoning accident based on a complex network, on the basis of considering the random uncertainty, shows the complex accident development scene intuitively on the network graph, realizes the half-quantity evaluation of the development process of poisoning accident, and also provides a reference for the quantitative assessment of accident risk of the modern complex process system.

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (71971110) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJA510008). The authors deeply appreciate the support.

REFERENCES Apostoli P; Lucchini R, Alessio L. Proposal of a method for identifying exposure to hazardous chemicals in biomedical laboratories[J]. 1996, 256(1):75–86. Crockett J M. Laboratory safety for undergraduates[J]. Chemical Health & Safety, 2011, 18(4): p.16–25. Erd P, R Nyi A, 2011. On the evolution of random graphs. J. Transactions of the American Mathematical Society. 286(1):257–274. Guo Heng, Chen Guoming, 2012. Offshore platform chain risk assessment based on Graph Theory. J. China Safety Science Journal. 22(5):106–112. https://doi.org/10.3969/j.issn.1003-3033.2012.05.017. He Lei et al, 2017. Research on Statistic and Countermeasure of112 University Laboratory Accidents. J. China Public Security. Academy Edition..02:49–53. https://doi.org/CNKI:SUN:GGAQ.0.2017-02-013. Juming XU, 2004. Graph theory and its applications. M. University of Science and Technology of China Press. Karapantsios T D, Boutskou E I, Touliopoulou E, et al. Evaluation of chemical laboratory safety based on student comprehension of chemicals labeling [J ].2008,3(1):e66–e73. Kaufman, James A. Occupational exposure to hazardous chemicals in laboratories: Understanding the OSHA laboratory standard[J]. Journal of Chemical Education, 1992, 69(11):911. Liu WY, Wang J M, Xie C, et al., 2012. Brittleness source identification model for cascading failure of complex power grid based on brittle risk entropy. J. Proceedings of the CSEE. 32(31): 142–149. https://doi.org/10. 13334/j.0258-8013.pcsee.2012.31.014. Peiyi Wang, Tong Wang. Analysis of accident factors of dangerous chemical products in the laboratory [J]. 2006, 27(1):25–17 Shariff A M, Norazahar N. At-risk behavior analysis and improvement study in an academic laboratory[J]. 2012,50(1):29–38. Wu Xiping, YANG Hongyu, HAN Songchen, 2016. Analysis on network properties of multivariate mixed air traffic management technical support system based on complex network theory. [J]. Acta Physica Sinica. 65(14): 15–23. https://doi.org/CNKI:SUN:WLXB.0.2016-14-004.

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Watts D J, Strogatz S H, 1998. Collective dynamics of ‘small-world’ networks. J. Nature. 393(6684). https:// doi.org/10.1038/30918. Yongliang Deng, et al, 2015. Research on subway physical vulnerability based on network theory and FMECA. J. Safety Science. 80. https://doi.org/10.1016/j.ssci.2015.07.019. Zhihong Li, 2014. Research on statistical analyses and countermeasures of 100 laboratory accidents. J. Experimental Technology and Management. 210–213+216. https://doi.org/10.16791/j.cnki.sjg.2014. 04.060.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Phase stability characteristics of marine natural gas hydrates during drilling fluid invasion Jianlong Wang School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong, China

Jinsheng Sun∗ School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong, China CNPC Engineering Technology R & D Company Limited, Beijing, China

Ren Wang CNPC Engineering Technology R & D Company Limited, Beijing, China

Kaihe Lv, Jintang Wang, Bo Liao & Qibing Wang School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong, China

Yuanzhi Qu & Hongjun Huang CNPC Engineering Technology R & D Company Limited, Beijing, China

ABSTRACT: With huge reserves, marine natural gas hydrate (NGH) is an important potential efficient and clean resource to replace oil and gas. The interaction between drilling fluid and NGHs in the drilling process such as mass and heat transfer is likely to induce the decomposition of NGHs in the reservoir, which leads to a decrease in reservoir strength and wellbore instability. In order to know the decomposition characteristics of hydrates during drilling fluid invasion, a simulation and evaluation apparatus for hydrate formation and decomposition was independently assembled to study the impacts of drilling fluid temperature, NaCl, and nano-SiO2 on the phase stability of hydrates in a porous medium. Study results show that the decomposition of hydrates in a porous medium can be divided into three stages during drilling fluid invasion. Hydrates are very sensitive to the change in drilling fluid temperature. The higher the drilling fluid temperature is, the faster the hydrate decomposition rate is. 5.0% NaCl can inhibit the decomposition of hydrates in local and accelerated decomposition stages, and the acceleration of hydrate decomposition rate in stable high-speed decomposition stage promotes hydrate decomposition. Nano-SiO2 can hardly affect the phase stability of reservoir hydrates at low concentrations. However, when nano-SiO2 concentration is equal to or greater than 3.0%, the decomposition rate of hydrates increases, and gradually accelerates with the increase in nano-SiO2 concentration, due to the impact of thermal conducting capacity of the fluid system enhanced by it. These findings will help guide the design of drilling fluid systems for marine NGHs and provide a scientific basis for safe and efficient drilling.

1 INTRODUCTION NGH is a clathrate formed by natural gas and water at low temperatures and high pressures, and over 90% of NGHs are distributed in the oceans (Lee 2011; Ripmeester 1987; Sloan 2003). With a global total organic carbon content about twice that of traditional fossil energy, NGHs are important potential efficient and clean resources to replace oil and gas (Tan 2005). Compared with oil and gas, hydrate drilling faces a series of challenges in respect of wellbore stability and safety ∗ Corresponding Author:

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[email protected]

DOI 10.1201/9781003318569-18

related to drilling fluid (Barker 1989; Klauda 2005; Ning 2013). Subsea NGHs are very sensitive to temperature, pressure, and properties of invading fluid. Drilling fluid invasion during drilling causes mass and heat transfer processes between it and reservoir NGHs. Improper control of drilling fluid performance is very likely to induce the decomposition of reservoir NGHs, weakening the mechanical strength of the reservoir, which will in turn lead to wellbore instability (Baez 1994; Reem 2008). Therefore, knowing the decomposition characteristics of reservoir hydrates during drilling fluid invasion is of great significance to quantitatively evaluate the phase instability of hydrates induced by drilling fluid invasion. Consequently, this paper addresses the decomposition characteristics of hydrates in the reservoirs during drilling fluid invasion based on an independently-assembled multi-functional simulation and evaluation apparatus for hydrate formation and decomposition and reveals the impacting patterns of different drilling fluid temperatures and components on the phase stability of hydrates, providing technical countermeasures for the design of drilling fluid system for marine NGHs to avoid wellbore instability and other downhole troubles. 2 TESTS 2.1 Materials Testing materials include sodium dodecyl sulfate (SDS), nano-SiO2, and quartz sand (16–30 mesh) purchased from Sinopharm Chemical Reagent Co., Ltd., CH4 (purity ≥ 99.9%) purchased from Beijing Chengxin Shunxing Gas Materials Sales Co., Ltd., and distilled water self-prepared in the lab. 2.2 Apparatus A multi-functional simulation and evaluation apparatus (Figure 1a) independently assembled by the lab was used in the test, which mainly consists of a high-pressure reaction kettle, a water bath temperature control system, a thermostat air bath box, a drilling fluid pumping system, a gas control system, a back pressure unloading system and a data acquisition system. Three layers of temperature sensors with a precision of ±0.05◦ C are installed at the bottom of the reaction kettle (Figure 1b). The data acquisition frequency is 2 seconds per time. Temperatures of the reaction kettle and drilling fluid sample tank are controlled by the water bath temperature control system and the thermostat air bath box, respectively.

Figure 1.

Multi-functional simulation and evaluation apparatus for hydrate formation and decomposition.

107

2.3 Methods Firstly, the simulation test of CH4 hydrate formation was conducted using the constant-temperature and constant-volume method, and then the hydrate decomposition test was conducted using the drilling fluid pumping system. The specific test steps are as follows: (1) Pour 300 mL 0.1% SDS aqueous solution into 1,200 g quartz sand. Seal it and allow it to stand still for 24 h to ensure that the quartz sand can be sufficiently wetted. (2) Clean and dry the reaction kettle. Check its gas tightness using N2 . Place the soaked quartz sand uniformly into the reaction kettle, and compact it. Install the instrument tubing, and then keep on vacuumizing it for 30 min. (3) Inject low-temperature CH4 into the reaction kettle at a rate of 0.01 MPa/s until the pressure reaches 10 MPa. Set the water bath temperature control system at 5.0◦ C. (4) After the temperature and pressure of the reaction kettle become stable, start up the backpressure unloading system to slowly reduce the reaction kettle pressure to 5.0 MPa. At the same time, turn on the thermostat air bath box to decrease the temperature of the drilling fluid sample tank. (5) Set the drilling fluid invasion rate at 20 mL/min. Startup the drilling fluid pumping system to inject simulated drilling fluid into the reaction kettle, and switch on the data acquisition system to monitor the temperature, pressure, and gas displacement inside the reaction kettle until the finish of the test.

3 RESULTS AND DISCUSSIONS 3.1 Response of reservoir hydrate phase stability to the change of drilling fluid temperature During NGH drilling, the change of drilling fluid temperature will lead to the change in reservoir temperature and pressure conditions around the wellbore, which will, in turn, impact the phase stability of hydrates. In order to quantitatively evaluate the impact of drilling fluid temperature on the phase stability of hydrates, this test analyzed the impact pattern of pumping fluid temperature on the decomposition of hydrates in a porous medium by monitoring the evolution of temperature field and methane release rate (based on which the phase stability and decomposition rate of hydrates are characterized) after distilled water at different temperatures was pumped. In this test, the distilled water temperatures were 7.5◦ C and 12.5◦ C, respectively. To ensure the repeatability and reproducibility of test processes, the setting of parameters such as the temperature of the porous medium and the back pressure of the backpressure valve remained consistent. Figures 2 and 3 show the curves of reservoir temperature and methane release rate versus time during the invasion of distilled water at different temperatures, respectively. Take Figures 2a and 3a as examples. The decomposition of hydrates can be divided into three stages after the invasion of distilled water at 7.5◦ C into a porous medium. The period from 0 to 0.5 min was the local decomposition stage of hydrates, in which only the hydrates invading near the piping absorbed heat, decomposed rapidly, and began to release methane. The period from 0.5 to 8.1 min was the accelerated decomposition stage of hydrates, in which the decomposition of hydrates in a porous medium began to accelerate under the actions of mass and heat transfer. According to the temperature sensors, there was a decrease in the heat absorption temperature of hydrates (with the biggest decrease of 0.8◦ C). The methane release rate kept on increasing rapidly. Impacted by the continual cooling of the water bath temperature control system, hydrates near the reaction kettle wall did not decompose obviously. The period from 8.1 min till the finish of the test was the stable high-speed decomposition stage of hydrates, in which the hydrates in a porous medium kept on decomposing at a large scale, and the release of methane peaked at a rate of 764 mL/min. The results indicate that hydrates in a porous medium in this stage had the least phase stability and the fastest decomposition rate. 108

According to Figure 3b, almost immediately after the distilled water at 12.5◦ C invaded the porous medium, hydrates were at the accelerated decomposition stage, and the methane release rate kept on increasing rapidly. After that, hydrates entered the stable high-speed decomposition stage. Compared with the distilled water at 7.5◦ C, the methane release rate reached its peak in 4.03 min, which was 59.17% shorter, and the peak release rate increased by 36.13% to 1,040 mL/min. The test results show that hydrates in a porous medium are very sensitive to the temperature of invading fluid. The higher the temperature of the invading fluid is, the worse the phase stability of hydrates is, and the faster the decomposition rate of hydrates is. Therefore, during marine NGH drilling, a cooling unit should be used to reduce the temperature of drilling fluid as much as possible under the premise of ensuring drilling operations, so as to effectively reduce the decomposition of hydrates in formation.

Figure 2.

Reservoir temperature vs. time during the invasion of distilled water at different temperatures.

Figure 3.

Methane release rate vs. time during the invasion of distilled water at different temperatures.

3.2 Response of reservoir hydrate phase stability to the change of salt concentration During marine NGH drilling, in order to improve the performance of drilling fluid and prevent the formation and accumulation of hydrates in a wellbore or wellhead blowout preventer, an appropriate 109

amount of inorganic salt is usually added to drilling fluid. However, the salt concentration of drilling fluid will change the phase stability of hydrates in the reservoir around the wellbore to some extent, thus affecting wellbore stability. Therefore, this paper studies the impact of 5.0% NaCl solution at an invasion temperature of 12.5◦ C on the phase stability of reservoir hydrates (Figure 4). As shown in Figure 4, after the invasion of 5.0% NaCl solution into the reservoir, the duration of the accelerated decomposition stage of hydrates was prolonged to 7 min, and the peak release rate of methane increased by a little to 1180 mL/min, compared with the distilled water at 12.5◦ C. The results indicate that 5.0% NaCl solution inhibited the decomposition of hydrates in the partial and accelerated decomposition stages, which is conducive to maintaining the phase stability of hydrates. In the stable high-speed decomposition stage, the acceleration of hydrate decomposition rate promoted hydrate decomposition, resulting in the expansion of the decomposition range of hydrates. Mechanical properties of the reservoir around the wellbore are bound to decrease rapidly due to the intensified decomposition of hydrates, which keeps on propagating along the radial direction, thus increasing the risk of wellbore instability.

Figure 4. The release rate of reservoir methane vs. time during the invasion of 5.0% NaCl solution.

3.3 Response of reservoir hydrate phase stability to the change of rigid sealing material During the horizontal drilling of marine NGHs, an appropriate amount of nano-sealing material can be added to the drilling fluid to prevent the drilling fluid from invading the hydrate reservoir. In this paper, nano-silica, a rigid water-wet sealing material, was selected as the study object. It has an average particle size of 80 nm, an adding concentration of 1.0%, 3.0%, and 5.0% respectively, an invasion temperature of 7.5◦ C, and an invasion rate of 20 mL/min. Its impact on the phase stability of hydrates in the porous medium was evaluated by conducting lab tests. Figure 5 shows the curves of methane release rate versus testing time after nano-SiO2 solution with different concentrations invaded the porous medium. Compared with distilled water, 1.0% SiO2 solution slightly shortened the duration of the stable high-speed decomposition stage for hydrates, but the peak methane release rate did not change significantly, which indicates that 1.0% SiO2 solution basically did not promote hydrate decomposition. When the concentration of SiO2 in solution was increased to 3.0% and 5.0% respectively, the duration of the stable high-speed 110

decomposition stage for hydrates was significantly shortened, and the peak methane release rate increased to 886 mL/min and 1198 mL/min, respectively. The results indicate that, when the concentration of SiO2 reached or was over 3.0%, the actions of mass and heat transfer were enhanced, the phase stability of hydrates was further reduced, the decomposition of hydrates in a porous medium was promoted, and the decomposition rate of hydrates accelerated significantly with the increase in SiO2 concentration.

Figure 5. Release Rate of reservoir methane vs. time during the invasion of SiO2 solution at different concentrations.

Available studies show that the addition of rigid sealing material failed to change the phase equilibrium conditions for methane hydrates. Each group of fluids invaded the reservoir at a constant temperature and velocity. The heat carried by the fluid was basically consistent with the erosion action applied by it on hydrates. Therefore, it failed to change the time when local hydrates started to decompose. After hydrates started to decompose, the addition of rigid sealing material impacted the decomposition rate of hydrates to different extents. In general, the decomposition rate of reservoir hydrates gradually accelerated with the increase in the adding amount of rigid sealing material. The formation and decomposition of hydrates are processes impacted by mass and heat transfer. On the premise that this test has not changed the mass transfer conditions for hydrates, it could be determined that this situation must be caused by the change in heat transfer conditions of the fluid system. To this end, the thermal conductivity of distilled water and each group of nano-fluids were tested at room temperature. The results (Figure 6) show that the addition of rigid sealing material increased the thermal conducting performance of the fluid to a certain extent, and this effect was enhanced with the increase in the adding amount. The thermal conducting capacity of the fluid system was enhanced, the heat required for hydrate decomposition was able to be transferred to the surrounding area more quickly, and the decomposition rate of hydrates gradually accelerated as the thermal conducting capacity of the fluid system increased. To sum up, the impact of rigid sealing material added to the drilling fluid system on the stability of reservoir hydrates during the horizontal drilling of marine NGHs is two-sided. On the one hand, a rigid sealing material with appropriate particle size can effectively prevent drilling fluid from invading the reservoir, thus strengthening the wellbore stability. On the other hand, a rigid 111

sealing material used will accelerate the decomposition rate of reservoir hydrates and aggravate wellbore instability instead of properly mitigating the invasion of drilling fluid, if it fails to meet the performance requirements.

Figure 6. Thermal conductivity of SiO2 solution at different concentrations.

4 CONCLUSIONS The interaction between drilling fluid and NGHs in the drilling process such as mass and heat transfer is likely to induce the decomposition of NGHs in reservoirs, leading to wellbore instability. This study reveals the mechanism of drilling fluid temperature and components impacting the phase stability of hydrates in a porous medium. The results show that, in the invasion process of drilling fluid, the decomposition of hydrates in a porous medium can be divided into three stages: local decomposition, accelerated decomposition, and stable high-speed decomposition. Hydrates are very sensitive to the change in drilling fluid temperature. The higher the drilling fluid temperature is, the faster the hydrate decomposition rate is. 5.0% NaCl can inhibit the decomposition of hydrates in the local and accelerated decomposition stages, and the acceleration of hydrate decomposition rate in a stable high-speed decomposition stage promotes hydrate decomposition. 1.0% Nano-SiO2 can hardly affect the phase stability of reservoir hydrates. When nano-SiO2 concentration is equal to or greater than 3.0%, the decomposition rate of hydrates increases, and gradually accelerates with the increase in nano-SiO2 concentration, due to the impact of the thermal conducting capacity of the fluid system enhanced by it. Therefore, it is recommended that the concentration of SiO2 should be controlled at less than 1.0% in the process of designing a drilling fluid system, and a drilling fluid cooling unit should be installed during NGH drilling to lower drilling fluid temperature to the greatest possibility, so as to effectively reduce the decomposition of hydrates in formation. ACKNOWLEDGMENTS This research was financially supported by the National Natural Science Foundation of China (41902323, 52174016), Engineering Research Center of Rock-Soil Drilling & Excavation and 112

Protection, Ministry of Education (202115), the CNPC’s Directly under the Institute Fund (2020D5008-01).

REFERENCES Baez L A, Clancy P, Computer simulation of the crystal growth and dissolution of natural gas hydrates[J]. International Conference on Natural Gas Hydrates, 1994, 715: 177–186. Barker J, Gomez R. Formation of hydrates during deepwater drilling operations[J]. Journal of Petroleum Technology. 1989, 41(03): 297–301. Klauda J B, Sandler S I. Global distribution of methane hydrate in ocean sediment[J]. Energy & Fuels. 2005, 19(2): 459–470. Lee J Y, Ryu B J, Yun T S, et al. Review on the gas hydrate development and production as a new energy resource[J]. KSCE Journal of Civil Engineering. 2011, 15(4): 689–696. Ning F L, Wu N Y, Yu Y B et al. Invasion of drilling mud into gas-hydrate-bearing sediments. Part II: Effects of geophysical properties of sediments[J]. Geophysical Journal International. 2013, 193(3): 1385–1398. Reem Freij-Ayoub R. Wellbore Stability Issues in Shales or Hydrate Bearing Sediments[C]. SPE Conference, 2008. Ripmeester J A, John S T, Ratcliffe C I, et al. A new clathrate hydrate structure[J]. Nature, 1987, 325(6100): 135–136. Sloan E D. Fundamental principles and applications of natural gas hydrates[J]. Nature. 2003, 426(6964): 353–363. Tan C P, Freij-Ayoub R, Clennell M B, et al. Managing wellbore instability risk in gas hydrate-bearing sediments[R]. In: SPE Asia Pacific Oil and Gas Conference and Exhibition. Society of Petroleum Engineers, 2005.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Molecular dynamics simulation of solubility parameters of supercritical CO2 and pentaerythritol ester BingXian Yao & Fang Liu Department of Energy and Mechanical Engineering, Shanghai Electric Power University, Shanghai, China

ABSTRACT: In a CO2 refrigeration system, the circulating fluid is in contact with the compressor used, and a portion of the oil is sent into the refrigeration circuit with various effects on performance. If the oil is immiscible with the refrigerant, the oil returning to the compressor is not smooth, causing damage to the compressor and the oil may accumulate in the heat exchange tubes. The purpose of this paper is to calculate and analyze the influencing factors of the solubility parameters between the two from a microscopic point of view, so as to achieve the controllable solubility. Using the molecular dynamics simulation method, the solubility parameters of supercritical CO2 and pentaerythritol ester (PECn ) were calculated. The results show that the solubility parameter of supercritical CO2 decreases with the increase of temperature and increases with the increase of pressure; the solubility parameter of pentaerythritol ester (PECn ) decreases with the increase of temperature, and the effect of the change of pressure is smaller, and the solubility parameter of pentaerythritol ester (PECn ) decreases with an increasing number of tail alkyl groups. To further improve the solubility parameter of supercritical CO2 , ethanol molecules were added. Ethanol molecules can form intermolecular hydrogen bonds with CO2 molecules to increase the polarity of CO2 , thereby improving the solubility parameter of supercritical CO2 . The molecular dynamics simulation calculation of the solubility parameters of supercritical CO2 and pentaerythritol ester is to analyze the mutual solubility between the two, so as to provide guidance for the solubility study of refrigerant CO2 and lubricating oil. 1 INTRODUCTION In the current research background, the compatibility of carbon dioxide and lubricating oil is a research content that cannot be ignored in refrigeration system research. Among the possible alternative refrigerants (YE 2019), there is no doubt that CO2 (carbon dioxide) is considered one of the most promising working fluids with zero pollution to the environment. However, up to now, the most suitable oil for working with CO2 has not been found, and even new synthetic lubricants (Laura 2008) such as PAG (polyalkylene glycol) and POE (polyol ester) have not reached the international unified recognition. Kawaguchi (Chinwuba 2019) et al. reported that PAG is the main lubricant of CO2 because it is partially miscible with CO2 . Li and Rajewski (Jeonghun 2015) conducted a lot of experimental comparative studies and found that POE and CO2 were completely miscible. It is extremely one-sided to judge which is superior or inferior simply from compatibility. Ma (Wang 2009) et al. think that POE is superior to other lubricants for transcritical CO2 systems (Zhang 2014), and Renz (Lee 2019) reports that POE is especially suitable for semi-enclosed reciprocating compressors and screw compressors of the CO2 system. The report of Tuninzhao (Zhao 2009) and the research of Wang (Wang 2020) and others think that PAG can be applied to transcritical systems, while POE can be applied to transcritical systems and cascade systems. In a word, although the long-term stability of POE is not as good as that of PAG in the transcritical CO2 system, POE is far superior to PAG in terms of compatibility and applicable system scope. In fact, because the circulating fluid is in contact with the compressor used, a part of the oil is transported to the refrigeration circuit, which has various influences on the performance (Leslie 2020; Saidur 2011).

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DOI 10.1201/9781003318569-19

The purpose of this paper is to study the factors that affect the compatibility of carbon dioxide with lubricating oil from a microscopic point of view and by means of molecular dynamics simulation, so as to control the degree of compatibility between carbon dioxide and PEC (Precursors of Polyol Ester POE, lubricating oil). The main work content is to build a system box with the help of Materials Studio, then optimize the energy and structure of the box, perform NPT (atomic number, pressure, and temperature) ensemble simulation, and finally calculate according to the dissolution parameter calculation program written by myself. 2 MOLECULAR DYNAMICS SIMULATION 2.1 Simulation parameters and steps The CO2 force field in this paper comes from the COMPASS force field in MS (Materials Studio). Considering that the elastic force field model will not improve the accuracy of viscosity calculation, all the force field models in this paper are rigid models with constant bond length and bond angle, so only intermolecular interaction potential is involved in the force field model. In this paper, the classical LJ 9-6 potential and electrostatic potential are used to describe the force field of the system, and the expression is as follows (McQuaid 2004): ⎡    6 ⎤ 9 rij0 rij0 qq ⎦+ i j U = εij ⎣2 −3 (1) rij rij rij Where, U represents energy, rij represents the distance between atoms I and J; qi and qj are the charges on atoms I and J, respectively. Parameters of the CO2 molecular model constructed in this paper are shown in Table 1. In this paper, the calculation method of LJ parameters between different atoms [12] is chosen as the “sixth power average”:   3  3  ri0 rj0 √ εij = 2 εi εj  6  6 ri0 rj0

rij0 =

(2)

  3  3  16 ri0 − rj0

(3)

2

Table 1. Single CO2 molecular parameters. q/e

q/e

L/nm

A/(deg)

+0.6512(C)

–0.3256(O)

0.1149(C=O)

180(O=C=O)

Firstly, the Amorphous Cell module in Material Studio 8.0 software package is used to construct a cubic periodic box containing 125 pentaerythritol ester molecules (taking PEC6 as an example) and a cubic periodic box containing 500 CO2 molecules, as shown in Figures 1(a) and 1(b). After building the models of the two, the NPT system is adopted to allow the system to reach the required temperature and pressure. When the temperature and pressure of the whole simulation box tend to be stable, it can be considered that the whole system has reached an equilibrium state. Finally, the solubility parameters of the system were calculated by the Forcite function module. 2.2 Calculation theory of solubility parameters Ecoh = − Einter 115

(4)

In the formula, Ecoh represents the cohesive energy of molecules in the whole system and is the average energy required to separate all molecules to an infinite distance from each other. Einter stands for the total energy between all the molecules; According to Average value of NPT pedigrees. Ecoh CED = (5) V Where Ecoh represents the cohesive energy of molecules in the whole system; CED stands for cohesive energy density; V is the volume of the entire system. δ = CED∧0.5

(6)

δ represents the solubility parameter in the formula; CED stands for cohesive energy density.

Figure 1.

Carbon dioxide and PEC initial box model.

3 ANALYZATION 3.1 Model validation In order to verify the accuracy of the calculation of the selected model, the solubility parameters of polar solvent toluene, non-polar solvent n-pentane, and hydrogen bond solvent ethanol at 298K were firstly calculated in this paper, and the average relative deviation (AARD) was analyzed with the experimental values, as shown in Table 2.   Ns  exp eri  1 − Asim  Ai i  AARD =   ∗ 100% exp eri  Ns i=1  Ai exp eri

Where Ns is the number of state points, while Asim and Ai i experimental values respectively.

(7)

are simulated values and

Table 2. The solubility parameter of common solvents. Solvents

Calculated value/MPa∧0.5

Experimental value/MPa∧0.5

Experimental value/MPa∧0.5

Toluene n-pentane ethanol

19.08 19.08 27.49

18.23 14.42 26.43

4.66 4.85 4.01

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According to the analysis of the average relative deviation (AARD) in Table 2, the calculated values of the solubility parameters of n-pentane, ethanol and toluene are all less than 5% compared with the experimental values in reference. Therefore, it is feasible to use this model to calculate the solubility parameters of supercritical CO2 and PECn .

3.2 Calculation of solubility parameters In this paper, the solubility parameters of supercritical CO2 at 8MPA-28MPa and 300K-400K and the solubility parameters of PECn at 300K-400K and 8MPa and 300K-400K and 28MPa are simulated. The molecular model of PECn (taking PEC6 as an example) is shown in Figure 2. Solubility parameters of supercritical CO2 and PECn are shown in Figures 3, 4, and 5.

Figure 2.

Molecular model of PEC6 .

Figure 3.

Simulated values of CO2 solubility parameters at a supercritical state.

As can be seen from Figure 3, the solubility parameters of supercritical CO2 are closely related to temperature and pressure, showing a negative correlation with temperature and a negative correlation with pressure. As can be seen from Figures 4 and 5, the solubility parameters of PECn are negatively correlated with temperature but are slightly affected by pressure changes. It decreases with the increase of tail alkyl number N. 117

Figure 4.

Simulation values of the solubility parameters of PECn at 8 MPa.

Figure 5.

Simulation values of the solubility parameters of PECn at 28MPa.

4 CONCLUSION In this paper, the Molecular dynamics simulation method is adopted to study the solubility parameters of supercritical CO2 and pentaerythritol ester. The main conclusions can be summarized as follows: (1) It can be concluded from the simulation results in this paper that the solubility parameters of supercritical CO2 are negatively correlated with temperature and positively correlated with pressure. This is because when the temperature rises, the total energy of the system increases, and this part will be converted into kinetic energy of the system, leading to more chaotic thermal movement of molecules in the system, reduced interaction force between molecules, and reduced solubility of the whole system. (2) The solubility parameters of PECn are negatively correlated with temperature, but are slightly affected by pressure changes, and decrease with the increase of tail alkyl number N. From the perspective of molecular structure, when the alkyl number of PECn increases, the molecular chain becomes longer, which leads to the weakening of the intermolecular interaction force and the decrease of the solubility of the system. 118

(3) CO2 is a non-polar molecule. From the perspective of solubility parameters, the closer the solubility parameters of solute and solvent are, the better their compatibility is. Under the premise of the same temperature and pressure, the polar solvent can be added to supercritical CO2 as a solvent to improve the solubility parameters of supercritical CO2 , and the alkyl number of pentaerythritol ester can be increased to increase its molecular chain length and reduce the solubility parameters of its system, so as to achieve the controllable compatibility degree of the two.

ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation (52176012), China Electric Power Research Institute (NYB51202001608), and the Natural Science Foundation of Shanghai Municipality (19ZR1420400). At the same time, I am very grateful for the help of my teachers.

REFERENCES Chinwuba V. O, Hung G. H & Hosung K (2019). Friction factors in open channels. J. Industrial Lubrication and Tribology. 62(1), 26–31. Jeonghun K, Jaewan L, Hwanjong C, et al (2015). Experimental study of R134a/R410A cascade cycle for variable refrigerant flow heat pump systems. J. Journal of Mechanical Science and Technology. 29(12), 5447–5458. Laura F. (2008). Solubility of carbon dioxide in pentaerythritol tetraoctanoate. J. Fluid Phase Equilibria. 277(1), 55–60. Lee J. Y. (2019). Waste heat recovery of recirculated MCFC using supercritical carbon dioxide power cycle. J. Plant Journal. 15(2), 42–45. Leslie R. R (2020). Synthetics, Mineral Oils, and Bio-Based Lubricants. M. CRC Press: 2020-01-29. McQuaid M. J. (2004). Development and validation of COMPASS force field parameters for molecules with aliphatic azide chains. J. Journal of computational chemistry. 25(1), 61–71. Saidur R. (2011). A review on the performance of nanoparticles suspended with refrigerants and lubricating oils in refrigeration systems. J. Renewable & Sustainable Energy Reviews. 15(1), 310–323. Wang D. (2020). Performance Comparison of CO2 , R170, and R41 Used in Transcritical Air Source Heat Pump Water Heater System. J. Chemical Engineering Journal. 71(S1), 51–56. Wang Y. D. (2009). Preliminary Study on Thermophysical Properties of Mixture in CO2 Transcritical Cycle System. J. Journal of refrigeration. 30(03), 1–5. Ye Z. L. (2019). Study on the influence of recoverer in transcritical CO2 heat pump with air source. J. Xi’an Jiaotong University. 53(05), 1–8. Zhang Z. Y. (2014). Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander. J. Entropy. 16(11), 5919–5934. Zhao X. (2009). A critical review of flow boiling heat transfer of CO2 -lubricant mixture. J. International Journal of Heat & Mass Transfer. 52(3–4), 870–879.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Study on thermal design method for impervious graphite heat exchangers B. Ren & H.L. Lu National Heat Exchanger Product Quality Inspection and Test Center, Shanghai Institute of Special Equipment Inspection and Technical Research, Shanghai, China

X.L. Xue, B. Xiao, Y.Q. Yang & J.D. Wang Shanghai Institute of Special Equipment Inspection and Technical Research, Shanghai, China

ABSTRACT: The impervious graphite heat exchanger is a kind of heat exchanger that has excellent anti-corrosion properties and high heat transfer efficiency. The thermal design method is rarely reported publicly and general heat exchanger design software does not have its calculation model. In this paper, a simplified thermal design method is studied which is comprised of three steps. The first step is to select a preliminary heat exchanger type based on the estimated heat transfer area. The second step is to check the thermal performance. That is to judge whether the selected heat exchanger area meets the requirements according to the calculation of the total heat transfer coefficient. The final step is to check the flow resistance ensuring the pressure drop is less than the maximum allowable value.

1 INTRODUCTION The impervious graphite heat exchanger is a kind of heat exchanger that has excellent anti-corrosion properties and high heat transfer efficiency. These heat exchangers are widely used in industrial fields such as chlor-alkali, acid production, fertilizers, pesticides, and organic synthesis. Used for chemical unit operations such as heating, cooling, condensation, evaporation, and absorption, they are the most used and typical graphite equipment. Graphite heat exchangers have the following types: floating head tubular type, circular-block type, rectangular-block type, plate type, plate groove type, etc. China standardization committee on non-metallic chemical equipment has formulated technical standards for, floating head tubular type, circular-block type, and rectangularblock type heat exchangers, which are respectively HG/T 3112 (SAC/TC 162 2011), HG/T 3113 (SAC/TC 162 2019) and HG/T 3187 (SAC/TC 162 2012). Impermeable graphite heat exchangers, especially block-hole heat exchangers, because of their special structure and complex medium flow state, their thermal calculation methods are rarely reported publicly, and general heat exchanger design software does not have its calculation model. The method is in the hands of a few foreign-funded manufacturing enterprises. However, none of these standards involve thermal design methods due to the following reasons. The first reason is that due to the difference in soaking material and process, the thermal conductivity of impermeable graphite material produced by different manufacturers is inconsistent. The second reason is that the complex structure of graphite heat exchangers, especially block-type heat exchangers, leads to complex flow and heat transfer mechanisms. In addition, there is no module for the thermal design of graphite heat exchangers in commercial software. Inconsistent and

120

DOI 10.1201/9781003318569-20

inaccurate thermal design methods will lead to high redundancy of heat transfer area and reduced heat transfer efficiency of impervious graphite heat exchangers. The graphite heat exchanger is a serialized product leading to a simplified thermal design method compared with metal heat exchange. In this paper, the design procedure is studied which is comprised of three steps. The first step is to select a preliminary heat exchanger type. The second step is to check the thermal performance. The final step is to check the flow resistance. The detailed design process is described below.

2 PRELIMINARY TYPE SELECTION The type selection procedure consists of calculation of heat transfer rate and effective mean temperature difference, determination of heat transfer area based on estimated overall heat transfer coefficient, and selection of preliminary type.

2.1 Heat transfer rate The heat transfer rate is the arithmetic mean of the heat transfer rate for the hot stream and that for the cold stream:   Q = (Qh + Qc ) 2 = [mh cp,h (Ti − To ) + mc cp,c (ti − to )] 2

(1)

where mh is the mass flow rate of the hot stream, cp,h is the specific heat of the hot stream, Ti and To are respectively inlet and outlet temperatures of the hot stream, mc is the mass flow rate of the cold stream, cp,c is the specific heat of cold stream and ti and to are respectively inlet and outlet temperatures of the cold stream.

2.2 Effective mean temperature difference For countercurrent flow, the log mean temperature difference is derived from: LMTD =

(Ti − to ) − (To − ti ) o ln TTio−t −ti

(2)

Accounting for different flow arrangements, the effective mean temperature difference is described as: EMTD = F · LMTD

(3)

where F is a correction factor. It can be shown graphically as a function of R and Pwhich are defined as: Ti -To (4) R= to − t i P=

to − t i Ti − t i

For block-type heat exchangers, F can be determined by looking up in Figure 1.

121

(5)

Figure 1.

Correction factor for block type heat exchangers (ASME 2000).

For floating head tubular heat exchangers, F can be determined by looking up in Figure 2.

Figure 2.

Correction factor for tubular heat exchangers with one shell pass and two tube passes.

2.3 Estimated value of heat transfer area The empirical value of the overall heat transfer coefficient can be obtained in Table 1. Then the estimated value of heat transfer area can be calculated by: Ae =

Q Ue · EMTD 122

(6)

Table 1. Empirical value of overall heat transfer coefficient (Xu 2002; Qiu; Zhao 2017). Function

Cooler Heater evaporator

Condenser

Media

Heat carrier

Empirical value W/(m2 ·K)

Weakly acidic aqueous solution Weak acid, aqueous solution Organic solution Gas

Water Seawater and freezing brine Water Water and freezing brine

930.4∼1395.6 465.2∼697.8 697.8∼1046.7 34.89∼174.45

Aqueous solution Organic fluid

Vapour Vapour

1163∼2907.5 930.4∼1744.5

Vapour Vapour + noncondensable gas Organic fluid steam Organic fluid steam +noncondensable gas

Water Water Water Water

930.4∼1744.5 348.9∼930.4 581.5∼1163 232.6∼814.1

According to the estimated heat transfer area, the type with the closest area is selected from the product series. It should be noted that the area of the selected type should be 10%-20% larger than the estimated area. And the area of the selected type shall be that of fluid with a smaller heat transfer coefficient. 3 THERMAL PERFORMANCE RATING 3.1 Calculated value of overall heat transfer coefficient After type selection, the actual overall heat transfer coefficient can be calculated by: 1 1  =  U 1 hc + (Rf ,c + Rr,c ) + Rw + (Rf ,h + Rr,h ) + 1 hh

(7)

where hc and hh are respectively cold and hot side heat transfer coefficients. Rf ,c and Rf ,h are respectively thermal resistances of fouling on the cold and hot sides. Rr,c and Rr,h are respectively thermal resistance of resin on the cold and hot sides. And Rw is the thermal resistance of the wall separating the hot and cold stream. 3.2 Individual heat transfer coefficient For forced convection heat transfer, the heat transfer coefficient is determined by (Xiong et al. 2006): N u = 0.023 · Re0.8 Pr 0.3 or 0.4 (Re > 10000) (8)     Re · Pr 1/3 λf 0.14 N u = 1.86 · (Re ≤ 2300) (9) λw l/d   6 × 105 N u = 0.023 · Re0.8 Pr 0.3 or 0.4 1 (2300 < Re ≤ 10000) (10) Re1.8 For condensation, the condensation heat transfer coefficient is expressed as (Yang & Tao 2006):  h = 1.13 ·  h=

gl 3 ρ2 λ2

1/3 ·

gρ2 λ3 hfg µtl

1/4 (Re ≤ 1600)

Re −1/2 58Prf (Prw /Prf )1/4 (Re3/4

123

− 253) + 9200

(11)

(Re > 1600)

(12)

For boiling during a tube, the boiling heat transfer coefficient is calculated by:  h = 0.62 ·

ghfg ρv (ρl − ρv )λ3 µdt

1/4 (13)

In addition to direct calculations by formulas, Zhang and Geng (Zhang & Geng 2017) provide a method for simulating condensation and boiling heat transfer coefficients using HTRI software. On the basis of applying the double-pipe heat exchanger model from HTRI, most biases between simulation results and manufacture parameters are less than 10%, indicating this method is applicable to engineering design. 3.3 Thermal resistance The thermal resistance consists of the thermal resistance of fouling, the thermal resistance of resin, and the thermal resistance of the wall. The thermal resistance of fouling is usually obtained by looking up the table. The effect of thermal resistance of resin is usually considered by reducing the thermal conductivity of graphite. The formula of thermal resistance of the wall depends on the type of heat exchanger. For floating head tubular heat exchangers, the thermal resistance of the wall is calculated by: do ln (do /di ) (14) Rw = 2λ The distribution of heat flux of block-type heat exchangers is shown in Figure 3. It can be seen that the thickness of the heat transfer wall periodic varies. The equivalent wall thickness δ’ is defined as: δ =

2V  Ah + A v

(15)

where V ’is the residual volume of the heat exchanger block after drilling. Ah, and Av are respectively surface areas of transverse and longitudinal holes.

Figure 3.

Distribution of heat flux of block type heat exchangers.

Then for block type heat exchangers, the thermal resistance of the wall is calculated by:  Rw = δ λ

(16)

3.4 Calculated value of heat transfer area The calculated value of heat transfer area is expressed as: A=

Q EMTD · U 124

(17)

The heat transfer area of the selected heat exchanger is compared with the calculated value. If the actual heat transfer area is smaller than the calculated value, the heat exchanger type should be reselected and the rating process needs to be conducted. 4 FLOW RESISTANCE CHECKING The pressure drop generated by the fluid passing through the heat exchanger is an important index to measure the economic efficiency of operation. And the energy loss due to pressure drop is compensated by power equipment that needs to consume electrical energy. The pressure drop is caused by the friction between fluid and wall and the change of flow velocity and direction. For floating head tubular heat exchangers, the shell side pressure drop can be calculated by the flow path analysis method (Shi & Wang 2013), and the tube side pressure drop can be calculated by the following formula: (18) p = pi + pr + pN where pi is pressure drop due to frictional resistance, pr is pressure drop due to return flow and pN is pressure drop that happened in import and export nozzle. For block type heat exchangers, the pressure drop in the channel is obtained by: p = N ζ

ρu2 2

(19)

where N is the number of blocks and ζ is the friction factor by experimental test. The calculated pressure drop is compared with the maximum allowable pressure drop (usually 50Kpa). If the calculated value is larger than the maximum allowable value, the heat exchanger type should be reselected. And thermal performance rating and flow resistance checking are progressed until heat transfer and flow resistance meet the requirements of the process. 5 CONCLUSION In this paper, a simplified thermal design method for the graphite heat exchanger is studied which is comprised of three steps. The first step is to select a preliminary heat exchanger type based on the estimated heat transfer area. The second step is to check the thermal performance. That is to judge whether the selected heat exchanger area meets the requirements according to the calculation of the total heat transfer coefficient. The final step is to check the flow resistance ensuring the pressure drop is less than the maximum allowable value. ACKNOWLEDGMENTS The work was funded by Shanghai Municipal Administration for Market Regulation (NO. 2021-25, NO.2019-28) and Shanghai Science Committee (No. 20ZR145000). REFERENCES American Society of Mechanical Engineers. (2000). ASME PTC 12.5 Single-phase heat exchangers (American standard). Qiu, X. F. & Zhao, G. H. (2017). Star of anti-corrosion materials - carbon and graphite. Science Press, Beijing. SAC/TC 162 China standardization committee on non-metallic chemical equipment. (2011). HG/T 3112 Shell and tube floating head graphite heat exchanger (Chinese standard). SAC/TC 162 China standardization committee on non-metallic chemical equipment. (2012). HG/T 3187 Heat exchanger of graphite rectangular-block (Chinese standard).

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SAC/TC 162 China standardization committee on non-metallic chemical equipment. (2019). HG/T 3113 circular-block type impervious graphite heat exchanger (Chinese standard). Shi, M. Z. & Wang, Z. Z. (2013). Principle and Design of Heat Exchangers (6th Edition). Southeast University Press, Nanjing. Xiong, J. Y., Wang, G. J., Chen, X. H. (2006). Studies on process design methods of round-hole type graphite coolers for hydrogen chloride. Chlor-Alkali Industry 34(11), 39–42, 45. Xu, Z. Y. (2002). Graphite chemical equipment. Chemical Industry Press, Beijing. Yang, S. M. & Tao, W. Q. (2006). Heat transfer (4th edition). Higher Education Press, Beijing. Zhang, M. & Geng, Y. C. (2017). Total heat transfer coefficient simulation calculation of graphite block heat exchanger. China Chlor-Alkali 31(2), 30–33.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Comparative analysis on measurement uncertainty of heat capacity by GUM and Monte Carlo method H.L. Lu & B. Ren National Heat Exchanger Product Quality Inspection and Test Center, Shanghai Institute of Special Equipment Inspection and Technical Research, Shanghai, China

B. Xiao, F. Zhao, J.D. Wang & Y.Q. Yang Shanghai Institute of Special Equipment Inspection and Technical Research, Shanghai, China

ABSTRACT: Monte Carlo method is especially suitable to evaluate measurement uncertainty of heat capacity Q and overall heat transfer coefficient k. Because their measurement models are nonlinear for heat exchangers, in the present work, an ordinary operating condition of the test data including flow, temperature, and pressure was chosen as the benchmark for a plate heat exchanger, and the Monte Carlo method was employed to produce 100000 groups of random operating conditions. The estimated values for Q and k by the Monte Carlo method were 0.78%, and 2.3% respectively less than those by GUM. The two methods both proved each other independently. But the measurement uncertainties by the former were 7.4 kW and 61 W/m2 *K for Q and k, while those by the latter were 16 kW and 138 W/m2 *K respectively. And the former were only 46.25% and 44.2% of the latter. In sum, the Monte Carlo method provides more accurate measurement uncertainty than GUM when each of the inputs is subject to the same uniform distribution.

1 INTRODUCTION The heat capacity Q and overall heat transfer coefficient k of the heat exchanger are tested and reported in accordance with the standards: GB/T 27698.1-2011, GB/T 27698.3-2011, the continuous quantity obtained from the test and described by the quantity value shall be evaluated for the measurement uncertainty in the standards: CNAS-CL01-G003:2021, CNAS-GL016:2020. When the measurement uncertainty affects the validity of the measurement results or their use, or when requested by the customer, or when the uncertainty affects the compliance with the specified limits, the extended uncertainty at about 95% confidence level shall be calculated according to GB/T 27418-2017, GB/T 27418-2018. On the one hand, it is convenient for users to evaluate its reliability; on the other hand, it also enhances the comparability between measurement results. Usually, the quality of measurement results is measured by measurement error, but measurement error can only show the short-term quality of measurement. Whether the measurement process is continuously controlled, whether the measurement results can remain stable and consistent and whether the measurement ability meets the requirements of production profitability need to be rated by measurement uncertainty. The greater the measurement uncertainty, the worse the measurement ability; On the contrary, it means that the measurement ability is stronger. The standard JJF 1059.1-2012 requires that the measurement model is linear, can be transformed into a linear model, or can be approximated by a linear model. When the above applicable conditions cannot be met at the same time, the measurement uncertainty can be evaluated by the MCM method, that is, the method of probability distribution propagation. The Monte Carlo method in the standard JJF 1059.2-2012 is especially proposed to evaluate uncertainty when the measurement model is obviously nonlinear. The measurement models of heat capacity Q and overall heat transfer DOI 10.1201/9781003318569-21

127

coefficient k are obviously nonlinear in terms of multiple flow, pressure, and temperature, therefor Monte Carlo method is better to evaluate the uncertainty of the heat exchanger. Castro used the GUM and Monte Carlo methodologies to develop an evaluation of the measurement uncertainty of the prover calibration. In the present work, 100000 groups of random operating conditions subject to uniform distribution were produced on the base of test data for a plate heat exchanger. The measurement uncertainties by the former were 7.4 kW, 61 W/m2 *K for Q, k, while those by the latter were 16 kW, 138 W/m2 *K respectively, that was the former were only 46.25%, 44.2% of the latter.

2 CONFIGURATION AND OPERATING CONDITION The heat exchanger was a plate heat exchanger with 33 pieces of plates, and the heat exchange area was 15.6 m2 . The water-water heat transfer test without phase-change was conducted under the specified operating condition by the standard [2]. Table 1 shows the detailed items and corresponding uncertainty. Table 1. Benchmark operating conditions and uncertainty. item

Gh (m3 /h)

Gc (m3 /h)

thi (◦ C)

tho (◦ C)

tci (◦ C)

tco (◦ C)

phi (kPa)

pho (kPa)

pci (kPa)

pco (kPa)

value accuracy

44.28 0.42

43.77 0.42

60.17 0.20

37.81 0.20

24.34 0.20

47.34 0.20

101.5 3.0

62.5 3.0

96.1 3.0

59.29 3.0

3 MEASUREMENT MODEL The heat capacity of the heat exchanger is expressed in equation (1) when the heat absorption of the cold fluid and the heat release of the hot fluid can be measured accurately. The overall heat transfer coefficient k is expressed in equation (2). Q=

QC + Qh ρc Cc Gc (tco − tci ) + ρh Ch Gh (thi − tho ) = 2 2 Q Q = K= ho −t Ftm F (thi −tco(t)−(t  ci ) −tco ) ln

(1) (2)

hi (tho −tci )

Where: Q, Qc , Qh are heat capacity, heat absorption, and the heat release; ρc and ρh are the density of the cold fluid, the density of the hot fluid, which are determined by fluid, temperature, and pressure; Cc and Ch are the specific heat of cold fluid, the specific heat of hot fluid, which are determined by fluid, temperature, and pressure; Gc and Gh are volume flow of cold fluid, volume flow of hot fluid, which are measured by a flowmeter; tci and tco are inlet temperature, the outlet temperature of cold fluid, which are measured by temperature sensor; thi and tho are inlet temperature, the outlet temperature of hot fluid, which are measured by temperature sensor; F is the heat exchange area. From the structure of expressions for Q and k, the measurement models are obviously nonlinear; the Monte Carlo method is especially suitable in this situation. 128

The operating condition including 10 independent variables shown in Table 1 was chosen as the benchmark. Then 100000 operating conditions were produced by random data of 10 independent variables such as flow, pressure, and temperature. All random data of one variable of operating condition were subject to a uniform distribution. Finally, the heat capacity and the overall heat transfer coefficient were computed successively.

4 NUMERICAL RESULT All random input data were subject to the uniform distribution of the corresponding 10 independent variables. Figure 1 showed the random input temperature of the hot fluid in uniform distribution, and Figure 2 showed the random flow of hot fluid in uniform distribution. Due to the same configuration of the sensor, the inlet temperature of hot fluid, the outlet temperature of hot fluid, the inlet temperature of cold fluid, and the outlet temperature of cold fluid were 0.12◦ C in the measurement uncertainty, the same as that by GUM.

Figure 1.

Random input temperature of the hot fluid in uniform distribution.

Figure 2.

Random flow of hot fluid in uniform distribution.

129

Due to the same configuration of the sensor, the inlet pressure of the hot fluid, the outlet pressure of the hot fluid, the inlet pressure of the cold fluid, and the outlet pressure of cold fluid were 1.7 kPa in the measurement uncertainty, the same as that by GUM. Due to the same configuration of the sensor, the flow of hot fluid and the flow of cold fluid were 0.24 m3 /h in the measurement uncertainty, the same as that by GUM. While the outputs were different from the inputs, the heat capacity was subject to a normal distribution shown in Figure 3, its skew and kurtosis were 0.0014, −1.2, respectively. The overall heat transfer coefficient was subject to a normal distribution shown in Figure 4, its skew and kurtosis were 0.0014, −1.2, respectively.

Figure 3.

Heat capacity distribution.

Figure 4.

Overall heat transfer coefficient distribution.

From Table 2, the estimated values for Q, k by the Monte Carlo method were 0.78% and 2.3% respectively less than those by GUM. They both proved each other independently. But the measurement uncertainties by the former were 7.4 kW and 61 W/m2 *K for Q and k, while those by the latter were 16 kW and 138 W/m2 *K respectively, that was the former were only 46.25% and 44.2% of the latter. Obviously, the Monte Carlo method provided more accurate measurement uncertainty than GUM when the inputs including flow, temperature, and pressure are the same. 130

Table 2. Evaluation result comparison by GUM and Monte Carlo Method.

Monte Carlo Method GUM

item

Gh m3 /h

thi ◦C

pco kPa

Q kW

kW/ m2 *K

Estimated value uncertainty Estimated value uncertainty

44.28 0. 24 / 0.24

60.17 0.12 / 0.12

59.29 1.7 / 1.7

1149.0 7.4 1158.0 16.0

5588 61 5719 138

5 CONCLUSION The Monte Carlo method was employed to produce 100000 groups of random operating conditions subject to a uniform distribution. The estimated values for Q and k by the Monte Carlo method were 0.78% and 2.3% respectively less than those by GUM. They both proved each other independently. But the measurement uncertainties by the former were 7.4 kW and 61 W/m2 *K for Q and k, while those by the latter were 16 kW and 138 W/m2 *K respectively, that was the former were only 46.25% and 44.2% of the latter. Obviously, the Monte Carlo method provided more accurate measurement uncertainty than GUM when the inputs including flow, temperature, and pressure are the same.

ACKNOWLEDGMENT The work was funded by Shanghai Municipal Administration for Market Regulation (NO. 2021-25, NO.2019-28) and Shanghai Science Committee (No. 20ZR145000).

REFERENCES Castro, H. (2021). Validation of the gum using the Monte Carlo method when applied in the calculation of the measurement uncertainty of a compact prover calibration. Flow Measurement and Instrumentation, 77, 101877. China National Accreditation Service for Conformity Assessment (2021). CNAS-CL01-G003:2021. Requirements for measurement uncertainty. China National Accreditation Service for Conformity Assessment (2020). CNAS-GL016:2020. Guidelines and examples for evaluation of measurement uncertainty of physical and chemical testing in the petroleum and petrochemical field. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China and China National Standardization Administration Committee (2017). GB/T 27418-2017. Guide to the evaluation and expression of uncertainty in measurement. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China and China National Standardization Administration Committee (2018). GB/T 27419-2018. Supplementary document for evaluation and representation of measurement uncertainty 1: distributed propagation based on Monte Carlo method. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China and China National Standardization Administration Committee (2011). GB/T 27698.1-2011. Performance test methods for heat exchangers and heat transfer elements Part 1: General requirements. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China and China National Standardization Administration Committee (2011). GB/T 27698.3-2011. Performance test methods for heat exchangers and heat transfer elements Part 3: Plate heat exchangers. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China (2012). JJF 1059.1-2012.Evaluation and expression of measurement uncertainty. General Administration of quality supervision, inspection, and Quarantine of the people’s Republic of China (2012). JJF 1059.2-2012. Monte Carlo method for evaluation of measurement uncertainty.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Quantitative risk analysis of domino effect in petrochemical enterprise based on vulnerability-resilience Yifan Lu, Mingguang Zhang∗ , Ziwei Yi, Chongqin Liang, Yudie Chang & Xinming Cui College of Safety Science and Engineering, Nanjing Tech University, Nanjing, Jiangsu, China Jiangsu Key Laboratory of Hazardous Chemicals Safety and Control, Nanjing, Jiangsu, China

ABSTRACT: In order to quantitatively evaluate chain accidents in chemical installations, vulnerability and resilience evaluations are introduced on the basis of the domino effect, and a quantitative calculation model is constructed from both the possibility and the consequences. In terms of target vulnerability, a calculation model is established by analyzing the impact indicators of peopleequipment. The focus is on the four stages of prevention-preparation-response-recovery to discuss the impact indicators of emergency resilience, and an indicator system with the analytic hierarchy process is constructed. Based on the analysis of the accident scene and the propagation path, the domino effect evaluation model of the explosion accident is established, the TNO model is used to define the risk of the domino consequence of the accident in the installation area, the vulnerability and resilience coefficients are introduced, the accident possibility is corrected, and the personal risk calculation is combined to construct a quantitative calculation Model. The feasibility of the model is verified through examples.

1 INTRODUCTION The raw materials, intermediate products and products stored and used in large-scale chemical production often involve inflammable and explosive hazardous chemicals. These chemicals are concentrated in layout and have large stock. Once they are leaked, they are prone to fire and explosion accidents. Among them, explosion accidents accounted for about 35%. (Abbasi 2010). Khan et al. proposed a framework theory to evaluate the possibility and potential harm of domino accidents (Khan 2001) The probit model is the main research method for thermal radiation and shock wave damage probability (Jia 2017) Based on a large amount of experimental data, Cozzani et al. proposed revised device damage and accident escalation thresholds, and proposed a quantitative evaluation method for dominoes, that is, describing the risk assessment results in terms of personal risks and social risks. Hemmatian et al. drew the social risk curve of the domino effect from the perspective of accident statistics, which can be used as the criterion curve for the risk evaluation results (Hemmatian 2014). The European Union proposes vulnerability factors for chemical parks and uses the salty analytic hierarchy process to analyze the vulnerability of personnel-environment-materials (Landucci 2015) Tan analyzed the factors influencing the vulnerability of the chemical industry park and established a set of quantitative evaluation systems by combining the fuzzy comprehensive analysis method and the principal component analysis method (Tan 2012). In the study of resilience, Health pointed out that the basic principles of accident disaster management are prevention, preparation, response and recovery. Sheng clarified the index factors affecting emergency response capabilities on the basis of scenario construction and used the analytic hierarchy process to assign values (Sheng 2017) Wang calculated the index weights through the structural ∗ Corresponding Author:

132

[email protected]

DOI 10.1201/9781003318569-22

equation model and established the evaluation model with the comprehensive evaluation method (Wang 2015). Currently, domino effect risk assessment has a relatively mature system, but the comprehensive assessment of chemical production combined with vulnerability and emergency resilience is relatively rare. This article introduces vulnerability and resilience coefficients in the quantitative assessment of cascading accidents to calculate personal risks, and to provide guidance for risk early warning of chemical companies.

2 QUANTITATIVE RISK ANALYSIS 2.1 Consequence analysis model The TNO multi-energy method needs to read the drawing data when calculating the overpressure. The drawing process is uncontrollable, manual viewing of the drawing is highly subjective and there are errors. The researchers obtained the correlation function through the numerical fitting. In this article, use the fitting function formula instead of reading the graph to obtain the value. The explosion intensity gradually increases from 1 to 10. In this paper, the explosion intensity of the device is selected as 7, and its dimensionless peak overpressure fitting equation is as follows (Sari 2011):  1 0.23 ≤ R ≤ 0.5 P s = (1) −1.20 0.5 ≤ R ≤ 100 0.406 × R 2.2 Domino effect risk analysis After calculating the influence of the initial accident damage form on the target equipment, compared with the target threshold, when it is greater than or equal to its extended threshold, a secondary accident may occur. The secondary accident probability of the target unit can be calculated by the corresponding damage probability model of the target equipment. The formula for calculating the probability P of secondary accidents of equipment under domino effect is as follows (Cozzani 2004):  1 −5 P = √ ∫Y−∞ exp −u2 /2 du 2π The scenario probability of domino effect is calculated as follows: fd(k,m) = f0 Pd(k,m) km fd(k,m)

(2)

(3)

is the probability that the m-th domino scene will occur simultaneously on In the formula, k devices with secondary events; f0 is the probability of the initial event; Pd(k,m) is the probability of the m-th domino scene where k devices have accidents at the same time. The Bayesian network is used to analyze the domino scene, treat the accident as a node in the network, introduce conditional probability to clarify the importance of each level of accident, and find the most likely propagation scene of the accident. The probability of an initial accident is expressed by the frequency of failure. Including the frequency of container leakage and the frequency of accidents caused by the fire of the leaked material. According to the description in the TNO Yellow Book, the failure frequency of atmospheric pressure vessel LOC under the condition of continuous leakage of small holes is 1 × 10−4 /year. The probability of delayed ignition of a fixed device that stores flammable substances is 0.1. Personal risk refers to the probability of individual death that may be caused to a person in a fixed position after different accidents in the area. In a chemical production enterprise, the personal 133

risk at a certain geographic location coordinate (x, y) is related to the probability of accidents, the probability of death of personnel, and the meteorological conditions of the natural environment (such as wind direction, wind speed). In order to simplify the model, without considering the influence of natural factors, the personal risk can be expressed as:

n (k,m) (k,m) f Vd (4) IR(x, y) = i=1 d  2 1 G−5 (5) V = √ ∫−∞ exp −u /2 du 2π In the formula, IR (x,y) is a personal risk, Vd(k,m) is probability of dying, V is the initial accident death probability without considering domino effect; after considering the domino effect, Vd(k,m) is the sum of the probability of death in all levels of accidents; V is the probability of death, and the value is between 0 and 1; G is the probability unit. 2.3 Vulnerability analysis From the main body of the enterprise, considering the vulnerability of the disaster-bearing body when it is damaged by the accident, it is mainly based on the personnel-equipment analysis influencing factors to determine the evaluation index (Fatemi 2017; Rui 2018). 2.3.1 Personnel vulnerability 1) Personnel Exposure Index A. Personnel exposure density B. Personnel exposed location 2) Personnel Damageability Index A. Personnel health B. Personnel age structure index C. Safety training indicators Ni (6) S In the formula: Ni is the number of personnel in each indicator; S is the area of the unit area. Pi =

2.3.2 Equipment vulnerability 1) Facility Exposure Index A. Facility exposure ratio B. Facility exposure location 2) Facility Damageability Index A. Facility/building importance B. Facility fire rating C. Explosion resistance of facilities Fi (7) S In the formula: Fi is the number of personnel in each indicator; S is the area of the unit area. Ii =

2.3.3 Vulnerability calculation model Chaoyang Tan used the Analytic Hierarchy Process to derive the weights of various indicators of the vulnerability of personnel and equipment in the chemical industry park. Based on the literature, the calculation formula of the vulnerability coefficient is given as follows: V = = 0.234P1 + 0.449P2 + 0.122P3 + 0.057P4 + 0.011P5 + 0.011I1 + 0.056I2 + 0.019I3 + 0.001I4 + 0.002I5 134

2.4 Resilience analysis In the life cycle of a disaster, the magnitude of emergency response capacity represents the strength of resilience. Combined with relevant policies, regulations and literature. Considering the actual emergency response scenario, the index system is constructed from the four aspects of “accident prevention and emergency preparedness”, “anomaly monitoring and early warning”, “emergency response” and “recovery afterward” (Chen 2009; Cheng 2015). According to the references, the emergency indicator system and related weights are given, as shown in Table 1. Table 1. Emergency index system Index/Weights Accident prevention and emergency preparation (0.275)

Comment content Emergency law (0.105) Emergency organization (0.117) Plan exercise management (0.432) Risk assessment (0.212)

Education and training (0.134) Abnormal monitoring and early warning (0.473) Emergency Response Recovery afterward (0.148)

Process control (0.325) Monitoring and early warning information processing (0.675) Emergency command (0.148) On-site rescue and disposal (0.346) Emergency support (0.506) Investigation and evaluation (0.372) Rebuild and restore (0.628)

Laws and regulations; policy understanding; Emergency institution Management system; emergency organization Emergency plan; emergency exercise Identification of major hazard installations; risk zoning classification; Risk point management; risk assessment system Safety production training; emergency education Whole production process supervision; risk early warning Information sharing; information push, Data management analysis; base database Coordinate command; discharge of duties Site management; medical rescue; human evacuation Material security; communications security Accident investigation and assessment; summary report Infrastructure repair and reconstruction

The resilience coefficient R0 can be calculated through the resilience score and weight. 2.5 Evaluation model According to risk=probability×consequence, based on this, this paper introduces vulnerability and emergency recovery capacity and builds a domino effect analysis model based on target vulnerability and emergency recovery.

Figure 1.

Quantitative evaluation model.

135

3 APPLICATION EXAMPLE There are 6 atmospheric storage tanks in the tank area, the container is 1000 m3 , and two groups of horizontally store n-butanol, toluene and methanol respectively. The distribution map of storage tanks is shown in Figure 2.

Figure 2. Distribution map of tank area.

Figure 3. Bayesian network diagram of domino scene.

Taking the explosion of the vapor cloud caused by the T1 leak as the initial accident unit, this paper analyzes the accident propagation path and determines the units that may be affected. When a vapor cloud explosion occurs at T1, based on the continuous leakage scenario (leakage diameter 300 mm, leakage duration 10min) and the TNO consequence model, the impact of the explosion of T1 on the remaining tanks can be obtained. The results are shown in Table 2. According to recent calculations, after the initial accident caused by the leakage of T1, the overpressure effect of the shock wave caused by the explosion of its vapor cloud on the T2 and T4 storage tanks is greater than the tank accident threshold, and there is a possibility of a domino accident. When T1 explodes under continuous leakage conditions, the directly affected accident units are T2, T4, and T5, which are the first-level domino effect units. T3 and T6 are two-stage domino effect units, and the results of the impact on the two-stage effect units when T2 and T5 explode under continuous leakage conditions are shown in Table 2. According to the analysis of the domino scenario based on the Bayesian network, the most probability accident propagation scenario is shown in Figure 3. Table 2. The impact of the first and second domino effects of the T1 storage tank explosion on adjacent storage tanks The first order domino effect

Secondary domino effect

Number

Distance/m

Overpressure/ kpa

T1 → T2 T1 → T3 T1 → T4 T1 → T5 T1 → T6

16 32 20 25 37

43.41 18.90 33.21 25.41 15.88

136

Number

Overpressure/ Distance/m

kpa

T2 → T3 T2 → T6 T5 → T3 T5 → T6

16 25 25 16

49.45 28.95 28.95 49.45

Considering the interlocking effect between domino effect units, assuming that vapor cloud explosions occur at T2, T3, and T4 at the same time, under the same specifications and parameters of each target unit, T3 and T6 are directly affected by the primary effect unit T2 and T5, and T4 is away from T3, T6 is farther than T2 and T5, so only the second level domino accidents that may be caused by T2 and T5 are considered. Based on historical accident cases and data, the possibility of Domino accidents of level 3 and above is extremely low, and this article will not consider this situation for the time being. According to the device damage model, the expanded overview of domino accidents at all levels in different accident scenarios is calculated, see Table 3 for details. Table 3. Probability of secondary accident caused by T1 vapor cloud explosion Primary domino accident device

Secondary accident device damage probability

Secondary domino accident device

Damage probability of three accident devices

T1 → T2 T1 → T4 T1 → T5

0.98 0.92 0.78

T2 → T3 T5 → T6 T2 → T6 T5 → T3

0.99 0.99 0.86 0.86

WhenT1 explodes, under the condition of continuous leakage of small holes, the propagation path of the first-level domino accident: T1 → T2+T4+T5, and the propagation path of the second-level domino accident: T2/T5→T3/T6. The probabilities of the domino scene are shown in Table 4. Table 4. Domino scene probability First-level domino

expansion probability

Probability of Domino scene

Secondary domino

expansion probability

Probability of Domino scene

T1 → T2+T4+T5

0.7032

7.032×10−5

T2/T5 → T3/T6

0.9999

7.032×10−5

The values of basic vulnerability indices of the plant are shown in the table below. Table 5. Coefficient values of basic indicators of vulnerability Index

Value

Personnel exposure density Personnel exposed location Personnel health Personnel age structure Safety training indicators Facility exposure ratio Facility exposure location Facility importance Facility fire rating Explosion resistance of facilities

0.25 0.14 0.04 0.04 0.2 0.54 0.22 0.24 0.32 0.36

After calculation, the vulnerability factor of the plant area is 0.155. 137

Through the investigation of the plant’s emergency resources and management capabilities, referring to section 2.3, statistics show that the plant’s emergency recovery indicators are scored as follows. After calculation, the recoverable coefficient is 0.83. Table 6. Emergency recovery index score Index

Value

Emergency law Emergency organization Plan exercise management Risk assessment Education and training Process control Monitoring and early warning information processing Emergency command On-site rescue and disposal Emergency support Investigation and evaluation Rebuild and restore

87 96 79 86 76 84 74 87 81 73 79 80

Table 7. Influence of personal risk value in domino scenario Scenarios No Domino Consider the first-order domino Consider secondary dominoes

Personal risk (before)

personal risk (after)

1.75×10−7 5.74×10−7

4.6×10−9 1.51×10−8

6.37×10−7

1.68×10−8

4 CONCLUSION AND OUTLOOK Introducing the concept of target vulnerability-resilience into the domino effect quantitative assessment system is more practical for quantitative risk assessment, and comprehensive consideration is given to the impact of equipment, personnel, management and other aspects. This paper gives a quantitative assessment method of the domino effect based on vulnerability and resilience and calculates an example, which shows that the calculation result of this method is more practical and can reflect the magnitude of risk more reasonably and scientifically. It is particularly pointed out that the vulnerability and resilience evaluation index system in this paper is relatively simple, and the determination of the index weight depends on the score of experts, which can be further improved in future research.

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (71971110) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJA510008). The authors deeply appreciate the support. 138

REFERENCES Abbasi, T., Pasman, H.J., Abbasi, S.A. (2010) A scheme for the classification of explosions in the chemical process industry. J. Hazard Mater. 174, 270–80. Cozzani V, Salzano E. (2004) The quantitative assessment of domino effects caused by overpressure – part i. probit models[J]. Journal of Hazardous Materials, 107(3): 67–80. Chen G, Zhang X. (2009) Fuzzy-based methodology for performance assessment of emergency planning and its application.J. Journal of Loss Prevention in the Process Industries, 22(2): 125–132. Cheng W-C, Chen W-Y, Yang H-B et. al. (2015) The factors determine the early development in patients with high-risk colon adenoma underwent surveillance colonoscopy. J. Journal of Gastroenterology and Hepatology, 30: 163–167. Fatemi Farin et al. (2017) Constructing the Indicators of Assessing Human Vulnerability to Industrial Chemical Accidents: A Consensus-based Fuzzy Delphi and Fuzzy AHP Approach. J. PLoS currents. Hemmatian, B.(2014) The significance of domino effect in chemical accidents. J. Loss Preve. Process. Ind. 29, 30–38. Jia, M.S, Chen, G.H., Hu, K. (2017) Review of risk assessment and pre-control of Domino effect in Chemical Industry Park. J. Chemical industry and engineering progress, 36(04), 1534–1543. Khan, F.I., Abbasi, S.A. (2001) Estimation of probabilities and likely consequences of a chain of accidents (domino effect) in Manali Industrial Complex. J. Cleaner Production, 9(6), 493–508. Landucci, G. (2015) Quantitative assessment of safety barrier performance in the prevention of domino scenarios triggered by fire[J]. Reliability Engineering and System Safety, 143, 30–43. Rui Zhao et al. (2018) A safety vulnerability assessment for chemical enterprises: A hybrid of a data envelopment analysis and fuzzy decision-making[J]. Journal of Loss Prevention in the Process Industries, 56: 95–103. Sheng, Y. (2017) Study on assessment method of emergency preparedness capability based on scenario construction technology. J. Safety Science and Technology. 13(10), 43–47. Sari A. (2011) Comparison of two multienergy and baker-strehlow-tang models. J. Process Safety Progress, 30(1): 23–26. Tan, C.Y. (2012) Study of Comprehensive Assessment Methods for Chemical Industry Park Vulnerability. Nankai University. Wang, T.Y., (2015) An empirical research of evaluation on emergency management capability in petrochemical enterprises. Harbin Institute of Technology.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

An optimization strategy for atmospheric tank area layout in pool fire environments Chongqing Liang, Mingguang Zhang∗ , Ziwei Yi, Yifan Lu & Yudie Chang College of Safety Science and Engineering, Nanjing Tech University, Nanjing, China

ABSTRACT: The atmospheric storage tank area stores huge amounts of materials. Once a fire accident occurs, it is likely to trigger the domino effect. Although the existing norms and standards have certain universality, there is still a lack of layout optimization to reduce the possibility of the domino effect. In the present work, the dynamic Bayesian network is used to construct an accident dynamic evolution network considering the domino accident in atmospheric storage tank areas under pool fire accidents. The overall escalated probability of domino accidents in the atmospheric storage tank area is calculated, combined with accident consequences, the typical layout of the atmospheric storage tank is analyzed, and the optimal tank area layout is identified to provide a strategy for atmospheric storage tank area layout optimization. According to the calculation, when there are two sizes of storage tanks, the small-size storage tanks are arranged together and the large-size storage tanks are arranged separately. The overall escalation probability and escalation risk of domino accidents in the atmospheric storage tank area are the lowest.

1 INTRODUCTION The petrochemical industry is one of the pillar industries in China, but it involves a large number of flammable and explosive dangerous chemicals, especially in the storage tank area, which stores a huge number of materials. Once an accident occurs, the consequences are serious and are prone to cause domino accidents (Bing 2016). Abdolhamidzadeh found that fires are the most common cause of domino effect accidents (Abdolhamidzadeh 2010). R.M. Darbra’s study showed that fire accidents accounted for 17.8% of domino accident sequences (Darbra 2010). The characteristics of fire accidents in oil storage tank areas are high flame temperatures and strong radiant heat. It is prone to domino accidents (Yuan 2009). Fire has time delays for the escalated form of domino accidents, and the possibility of damage to the adjacent storage tanks is related to the spacing between tanks. The dynamic Bayesian network can well combine the influence of time and space on domino accidents and evolve the escalated form of the accident (Khakzad 2017). Zheng Feng constructed a thermal radiation coupling model of the chemical storage tank area based on the dynamic Bayesian analysis theory and obtained the accident probability of each accident tank after the initial accident (Zheng 2019). According to the research of the above scholars, the dynamic Bayesian network method can be used to show the evolution and escalation of domino accidents in atmospheric tank area fire. Based on the dynamic Bayesian network analysis technology, the accident probability of each level of the storage tank was calculated from two perspectives, i.e., failure time and failure probability. The optimal layout of atmospheric storage tank area is analyzed according to the economic loss caused by the accident.

∗ Corresponding Author:

140

[email protected]

DOI 10.1201/9781003318569-23

2 ASSESSMENT OF ATMOSPHERIC TANK LAYOUT IN A POOL FIRE ENVIRONMENT The layout assessment of the atmospheric storage tank area in pool fire environments is mainly divided into three parts: 1) evolution of the escalated probability of domino accidents; 2) direct economic loss from the accident; 3) risk assessment of domino accidents. 2.1 Accident propagation mode in atmospheric storage tank area under pool fire environment Storage tanks in atmospheric pressure tank areas mostly use internal floating roof oil tanks. The fire accidents of internal floating roof storage tanks are mainly pool fire. The pool fire mainly damages the surrounding storage tanks through thermal radiation (Fukuda 2005, Santos 2014). Thermal radiation causes the temperature of the wall of the adjacent storage tank to rise, and finally, the storage tank is damaged, leading to more serious consequences. Cozzani proposed a critical failure threshold of 15 kW/m2 for atmospheric storage tanks subjected to thermal radiation for more than 10 min in a pool fire (Cozzani 2006). The atmospheric tank failure probability model constructed by Cozzani is shown in Table 1: Table 1. Escalated model of atmospheric equipment failure probability. Escalated factors

Target device

Threshold value

Probabilistic calculation model

Thermal radiation

Atmospheric pressure equipment

15 KW/m2

Y = 12.54 − ln (t)

t ≥ 10 min

ln(t) = −1.128 ln (Q) − 2.667 ×10−5 V + 9.877

In Table 1, Y represents the probability unit value of failure probability of target equipment; t represents the failure time of target device (s); Q represents the thermal radiation value received per unit area of the target equipment (kW /m2 ); V represents the volume of the target device (m3 ). Y values under different risk factors are calculated according to different types of the target equipment. The failure probability Pd of the target equipment can be obtained by Formula (1): 2 1 −5 −u 2 Pd = √ ∫Y−∞ e du 2π

(1)

2.2 Economic conversion of property loss The commonly used economic translation of property loss is shown in Formula (2), but this formula is not applicable to the assessment of the consequences of domino accidents with different layouts in the same storage tank area. Through Formula (1) and the dynamic Bayesian network, the failure probability of each tank can be dynamically obtained. Therefore, Formula (3) is adopted to calculate the direct economic loss caused by the accident. L = πR2 ρ

(2) 

LD = LT + π RT m Pr t

(3)

where L is the converted value of property loss (yuan); R is the radius of property loss (m); ρ is the average density of property in the accident tank area (yuan/m2 ); LD is the economic converted value of property loss in domino accidents in the atmospheric storage tank area fire (yuan); RT is the radius of the accident storage tank (m); m is the mass burning rate per unit liquid surface area of the storage material in the accident tank (kg/ m2 ·s); Pr is the price of materials; t is the burning time of materials (s). 141

2.3 Risk degree The traditional risk evaluation is to analyze and evaluate the risk degree of the project and determine whether it is within the acceptable range. However, this method is a qualitative risk assessment approach with strong subjectivity. Therefore, the calculation formula is improved, as shown in Formula (4). The improved formula applies to quantitative evaluation and can objectively reflect the risk degree of each layout. RL = PT × LD

(4)

where RL is the risk degree of domino accidents in a storage tank area fire; PT is the tank failure probability under domino accidents in a tank area fire.

3 ATMOSPHERIC STORAGE TANK AREA EXPANSION CLASSIC LAYOUT Reasonable layout is of great significance to reduce the escalation probability of domino accidents and increase the rescue time. It is supposed that there are four atmospheric storage tanks in a chemical storage tank area, and four atmospheric storage tanks are expanded later, as shown in Figure 1. Three typical layouts were selected for comparative analysis to explore the optimal layout. The difference between Layout scheme 1 and Scheme 2 is whether the small-size storage tanks are placed together or the large-size storage tanks are placed together. The difference between Layout 3 and other layouts is that the large-size storage tanks are staggered. The optimal layout strategy of the atmospheric storage tank area is explored by comparing the total domino escalation probability of three typical storage tank areas when the tank fire accident occurs.

Figure 1. Typical layout schemes of the atmospheric storage tank area.

4 CASE ANALYSIS There are four storage tanks in the atmospheric storage tank area of a chemical enterprise. The tank area layout is shown in Figure 2(a). The original tank area needs to be expanded. The layout of the new tank area is shown in Figure 2(b). Parameters of each tank are shown in Table 2, and parameters of each material are shown in Table 2. The initial accident tank was analyzed as a pool fire. The thermal radiation of each storage tank obtained through the solid flame model is shown in Table 3 (Chen 2018; Fu 2008; Mudan 1984; Thomas 1963) 142

Figure 2.

(a) Layout of storage tank area before expansion. (b) Layout of storage tank area after expansion.

Table 2. Relevant parameters of each tank. Storage material

Tank code

Gasoline tank Diesel tank

T1, T2, T5, T6 T3, T4, T7, T8

Tank volume (m3 ) 17000 11000

Tank type

Tank diameter Tank Filling (m) height ratio

Inner 35 floating roof 28 tank

18

0.75

18

Heat of liquid burning Density/ combustion/ rate/kg/ (g·cm−3 ) (kJ/kg) (m2 ·s) 0.75

4.4×104

0.0225

0.85

4.48×104

0.016

Table 3. Thermal radiation values received by each tank in the initial layout. The thermal radiation of the target tank I (kW/m2 ) Initial accident storage tank

T1

T1 T2 T3 T4 T5 T6 T7 T8

15.44 12.71 9.61 9.17 8.18 8.26 7.77

T2

T3

T4

T5

T6

T7

T8

15.44

15.44 10.82

10.82 15.44 11.12

9.17 15.44 8.26 9.61

8.18 9.17 7.77 8.26 15.44

8.78 10.82 8.37 11.12 15.44 10.82

8.07 8.78 7.80 8.37 10.82 15.44 11.12

9.61 12.71 15.44 9.17 9.61 8.26

11.12 8.78 8.07 8.37 7.80

10.82 8.78 11.12 8.37

15.44 12.71 9.61

9.61 12.71

11.12

4.1 Determination of initial accident tanks in layout In the initial layout, all tanks are assumed to be initial accidents for scenario construction. The scenarios are as follows: Scenario 1: when T1 is the initial accident storage tank, IT2 = IT3 = 15.44 > 15 kW/m2 , and the thermal radiation received by T4 is less than the escalated threshold, so first order escalation may occur in T2 and T3. When T2 and T3 have accidents and T1 simultaneously produces thermal radiation effect on the adjacent target storage tank, IT4 = 37.38 > 15 kW/m2 , IT5 = 32.87 > 15 kW/m2 , and IT7 = 27.97 > 15 kW/m2 . Compared with T7, T4 and T5 have a large difference in thermal 143

radiation values and are affected by T1, T2 and T3 fires in advance. Therefore, Tanks T4 and T5 are set as second order escalation. T6, T7 and T8 are affected by the accident tanks T1, T2, T3, T4 and T5, resulting in third order escalation. In Scenarios 2, 3 and 4, T1, T2, T3 and T4 are set as the initial accident storage tanks, and the above analysis process is repeated. By comparing various accident scenarios, T2 is determined to be the most likely domino escalation caused by the initial accident storage tank. The above scenario analysis is carried out for the layout schemes 1, 2 and 3, and the thermal radiation value of the tanks in each layout is calculated. The analysis of each layout determined that T11, T21 and T31 are the initial tanks, which may lead to the most serious domino accident. 4.2 Probability of atmospheric tank escalation in a pool fire environment According to scenario analysis, the transmission process of domino effect is divided into three stages, as shown in Figure 3. Level-1 upgrade occurs 9 to 10 minutes after an accident occurs, level-2 emerges 13 minutes after an accident occurs, and Level-3 occurs 15 to 16 minutes after an accident occurs. The above process is repeated for the layout schemes 1, 2, and 3. The probability of initial tank pool fire accident is set at 1 × 10−5 (Cozzani 2005). All layout expansion probabilities are calculated.

Figure 3.

Initial layout accident escalated Bayesian network construction. diagram.

Through Formulas (1), (3) and (4), the following results can be obtained in combination with the dynamic Bayesian theory. The overall escalated probability and escalated risk of the initial layout are 6.87e−9 and 4.68e−2 , respectively. The overall escalated probability and escalated risk of the layout scheme 1 are 3.81e−9 and 2.50e−2 , respectively. The overall escalated probability and escalated risk of the layout scheme 2 are 6.91e−9 and 4.70e−2 , respectively. The overall escalated probability and escalated risk of the layout scheme 3 are 4.58e−9 and 5.74e−2 , respectively. The maximum escalated probability is 1.8 times of the minimum value, and the maximum escalated risk degree is 2.3 times of the minimum value. To sum up, the atmospheric storage tank area expansion should choose the layout scheme 1. 5 CONCLUSION Based on the existing standard specification of storage tank fire spacing, the storage tank spacing is set, and four typical storage tank expansion methods are selected. The thermal radiation of each tank is obtained based on a solid flame model. The initial accident tank is determined by analyzing each tank. The escalated model of domino accidents in atmospheric storage tank areas is established by the dynamic Bayesian method. According to the accident escalation model, the overall escalation probability of domino accidents in each layout scheme is calculated, and the optimal layout is obtained, which further improves the layout optimization of the atmospheric storage tank area. 144

ACKNOWLEDGMENTS The authors thank the General Program of National Natural Science Foundation of China (71971110) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJA510008) for funding support.

REFERENCES Abdolhamidzadeh B, Abbasi T, Rashtchian D, et al. (2010) A new method for assessing domino effect in chemical process industry. J. J. Hazard. Mater. 182 (1-3):416–426. Bing Wang. (2016) Study on Rational Distribution of Petrochemical Tank Zone Based on The Domino Effects [D]. Shenyang Aerospace University. CozzaniV, Gubinelli G,Antonioni G, et al. (2005)The assessment of risk caused by domino effect in quantitative area risk analysis. J. J. Hazard. Mater., 127:14–30. Cozzani V, Gubinelli G, Salzano E. (2006) Escalation thresholds in the assessment of domino accidental events. J. J. Hazard. Mater., 129(1–3):1–21. Chen C, Reniers G, Zhang L. (2018) An innovative methodology for quickly modeling the spatial-temporal evolution of domino accidents triggered by fire. J. J. Loss Prev. Process Ind., 54:312–324. Darbra R M, Palacios A, Casal J. (2010) Domino effect in chemical accidents: Main features and accident sequences. J. J. Hazard. Mater., 183(1-3):565–573. Fukuda M. (2005) Characteristics of Two Small Pool Fires Arranged Two Different Horizontal Planes. J. Fu Zhimin, Huang Jinyin, Fu Min. (2008) Quantitative analysis of fire damage and destruction of hydrocarbon fluids. J. Zhongguo Anquan Kexue Xuebao., (09):29–36. Khakzad N, Landucci G, Reniers G. (2017) Application of dynamic Bayesian network to performance assessment of fire protection systems during domino effects. J. Reliab. Eng. Syst. Saf., 167:232–247. Mudan, Krishna S. (1984) Thermal Radiation Hazards from Hydrocarbon Pool Fires[J]. Prog. Energy. Combust. Sci., 10:59–80. Santos F, Landesmann A. (2014) Thermal performance-based analysis of minimum safe distances between fuel storage tanks exposed to fire. J. Fire Saf J., 69(oct.):57–68. Thomas P H. (1963) The size of flames from natural fires. J. Symp. (Int.) Combust., [Proc.], 9(1):844–859. Yuan Jing. (2009) The research and application of ways to control fire and explosion happened in oil tin[D]. Tianjin University of Technology. Zheng Feng, Zhang Mingguang, Zuo Yawen. (2019) Construction of Domino accident scenario in chemical plant area based on dynamic Bayesian network. J. Nanjing Gongye Daxue Xuebao, Ziran Kexueban., 41(5):554–560.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

An experimental study on the application of separated heat pipes to waste heat discharge water tanks Baoming Zhao & Jianjie Cheng School of Urban Construction, Nanjing University of Technology, Nanjing, China

Ke Qiao School of Energy Science and Engineering, Nanjing University of Technology, Nanjing, China

Weihao Ji & Wei Li School of Urban Construction, Nanjing University of Technology, Nanjing, China

Xirui Xian & Fucai Chen Science and Technology on Reactor System Design Technology Laboratory, Nuclear Power Institute of China, Chengdu, China

ABSTRACT: In the passive containment cooling system (PCS), the separated heat pipe heat exchanger is of great significance for the heat dissipation in the containment. It is urgent to carry out experimental research on the heat transfer performance of large-scale separated heat pipes (SHP). In this paper, a test device is built, and the thermal stratification degree of the cooling water tank, the field of water temperature change, and the thermal characteristics of the SHP are tested and analyzed through the distribution change of the temperature field of the water tank in the test system. The results show that the temperature field distribution difference in the test water tank is mainly manifested in the vertical height direction, and the maximum temperature difference does not exceed 3◦ C; the SHP has a good regulation and control effect on the uniform temperature field of the water tank; at a heat load within the range of 1.6-6.8 kW, the SHP has better adaptability. When the temperature of the water tank is in an unsteady state, there is a proportional relationship between the heat load in the water tank and the heat dissipation capacity of the SHP; as the temperature of the water tank becomes stable, the fluctuation of the average heat transfer coefficient at the evaporating end and the condensing end decreases. Therefore, the overall heat dissipation effect of the SHP radiator meets the design requirements.

1 INTRODUCTION As an efficient passive heat transfer device, the split heat pipe has been widely used in the fields of electronics, metallurgy, chemistry and aerospace (Chen 2009; Esen 2005; Garrity 2007; Zhuang 2000). The separation heat pipe is applied to the residual heat removal system of the pressurized water reactor, the containment cooling system, and the spent fuel pool cooling system, and has achieved good results (Company; Li 2017; Shen 1996; W. E. 2011). However, the heat load to be discharged from the cooling water pool is large, and there are strict requirements on the upper limit of the temperature of the cooling water pool, which further increases the difficulty of test measurement. In addition, there are many factors affecting the heat transfer performance of the separated heat pipe (Qian 2012; Hao 2009; Wang 2014; Wang et al. 2014), such as: the working medium of the heat pipe, the specifications and dimensions of each part of the heat pipe, the structure and size of the water tank, the height-diameter ratio of the water tank, the position of the inlet and outlet of the water tank, the inlet flow rate, the inlet temperature, and the initial temperature (Chung 146

DOI 10.1201/9781003318569-24

2008; Haller 2009; Kenjo 2007; Tang 2011). In recent years, the heat transfer mechanism, internal flow, and heat transfer characteristics of the separated heat pipe system have been widely studied by many researchers (Chen 2003; Shi 2011; Wang 2000; Zhang 2019). However, for integrated, large-scale separated heat pipes and heat exchangers, experimental studies on thermal-hydraulic behavior under high a high density of heat flux are rarely reported. In this paper, the actual engineering system is scaled to calculate and analyze the spatial distribution of the temperature field in the cooling water tank, the law of development and change with time, and accompanying phenomena, as well as the thermal characteristics of the separated heat pipe. The influence of factors such as heating power and location of the heat source on the temperature distribution of the water tank and the heat transfer characteristics of the heat pipe is simulated. It provides a research basis for evaluating the influence of the thermal stratification of the water tank on the natural circulation flow of the tank and the heat transfer of the heat pipe.

2 TEST EQUIPMENT AND METHODS 2.1 Experimental scaling The following parameters of the experiment are conserved: (1) The heat load per unit area in the prototype = the calorific value per unit area in the experiment:   Qprototype = Qexperiment

(2) The ratio of the volume of the annular cylinder in the prototype to the heating area of the prototype = the ratio of the volume of the water tank in the test to the heating area in the test:     V V = S prototype S  experiment (3) Heat load under prototype conditions/heat load in experiment = Vprototype /Vexperiment (q × K × A)prototype Vprototype = (q × K × A)experiment Vexperiment where q is the heat flux density, A is the effective heat transfer area, K is the heat transfer coefficient, and V is the water volume. Table 1 is the geometric ratio of the test section relative to the prototype condition. Table 1. Geometric proportions. parameter water quality (kg) Cabinet heating surface area (m2 ) heat load (kw) Box height (m)

prototype value

Test value

Proportion

9600 19.84

1200 2.48

8:1 8:1

25 2.2

0∼6.4 2.2

(3.9∼8):1 1:1

Comparing the operating conditions of the test and the prototype, the temperature of the heating element in the test is about 300◦ C, and the temperature of the water tank in the prototype is about 280◦ C. Therefore, once the heat generating body generates heat, the duration of the two conditions is considered to be approximate. 147

2.2 Test equipment The purpose of this test is to study the heat transfer characteristics of the heat pipe heat exchanger. The system can measure the heat transfer performance of the separated heat pipe under different heat dissipation modes of the specific simulated heat source power, ambient temperature and condenser end. Figure 1 is a schematic diagram of the test system.

Figure 1.

Schematic diagram of test system.

The test system includes a separated heat pipe, a simulated heat source, a water supply and return module and a data acquisition module. Among them, the simulated heat source includes four insulated aluminum plates with adjustable heating power and related electrical equipment; the water supply and return module consists of a water tank, water supply and return pipelines; the data acquisition module includes a patrol instrument, a K-type thermocouple, and a desktop computer. Among them, the water tank is made of stainless steel with a cover. The support structure of the top cover of the water tank fixes the separated heat pipe condenser on the upper cover surface. Aluminum plate, coated with thermally conductive material on the bonding surface. The outer wall of the entire water tank is wrapped with thermal insulation material with a thickness of 30 mm to reduce the convection and radiation heat exchange between the water tank and the surrounding environment during the test. The evaporation end of the separated heat pipe immersed in the water tank, because the low boiling point working medium (pure water) in the tube bundle of the evaporation end absorbs the heat in the water tank, vaporizes a lot, and passes through the riser pipe to the condensation end under the driving action of the density difference. The saturated vapor condenses exothermically in the condenser, then flows through the downcomer by gravity and returns to the evaporator again. The heat supplied to the tank by the simulated heat source is dissipated through the split heat pipe and released to the surrounding environment. As shown in Figure 2, the material of the separated heat pipe is made of the 304 stainless steel with a liquid filling rate of 50%, including the evaporation section, the rising pipe, the condensation section and the descending pipe. The evaporation end of the heat pipe is composed of 30 8×1 mm stainless steel tubes in parallel, with a vertical height of 780 mm, an outer diameter of 8 mm and 148

a wall thickness of 1 mm; the condensation end is composed of 149 8×1 mm finned stainless steel tubes horizontally. In parallel, the fin rib height is 3 mm; the inner diameter of the rising tube is 32 mm, and the wall thickness is 2 mm; the inner diameter of the descending tube is 10 mm, and the wall thickness is 1 mm. The detailed test conditions are shown in Table 2. Note that the wind speed at the condensing end is 4 m/s during forced convection.

Figure 2.

Schematic diagram of separated heat pipe radiator. Table 2. Test conditions.

Working condition 1 Working condition 2 Working condition 3 Working condition 4

Simulate heat source heating power (kw)

Ambient temperature (◦ C)

Condensing end air cooling method

1.6

25

Natural convection

4.6

25

Forced convection

6.4

30

Forced convection

1.6

40

Natural convection

2.3 Arrangement of thermocouple measuring points The K-type thermocouple used to measure the water temperature and wall temperature in the test has a range of 0 to 1300◦ C and an error limit of ±0.75%t (t is the measured value). The specific measurement point layout is shown in Figure 3. Figure 3(a) shows four temperature measuring points arranged on the inner wall of the water tank heating, which are all located on the geometric center point of each insulating aluminum plate to monitor whether the simulated heat source is heating well. To identify whether there will be a “thermal runaway” phenomenon with uneven temperature in the area, four layers of horizontal temperature measuring points are evenly arranged inside the water tank, six on each layer, a total of 24, as shown in Figure 3(b). In order to monitor whether the separated heat pipe is during operation 149

Figure 3.

Layout of measuring points.

and the wall temperature of each part during operation, K-type thermocouples are arranged in their corresponding positions, and the measuring points on the wall surface of the tube bundle at the evaporation end are arranged vertically and equidistantly, as shown in Figure 3(c). Details are shown in Table 3.

Table 3. Summary of measuring points. Location Inner wall of water tank Inside the tank riser Left/right cavity wall down tube Evaporator

Measuring point number B1∼B4

number 4

S1∼S24 SS-1∼SS-4 L(R)1∼L(R)5

24 4 10

X-1∼X-5 1∼30

5 30

2.4 Test steps Before the start of the test, we first adjust the parameters of the height of the water tank liquid level, the water tank water temperature and the ambient temperature of the condenser to the set values. Then, we turn off the electric heater, turn on the corresponding simulated heat source according to the set working conditions, and adjust to the test power value; in addition, according to the different cooling methods of the condenser, we decide whether to start the fan in the air duct.

150

During the test, the signal output by the K-type thermocouple can be read and displayed on the desktop computer intuitively through the inspection device, and the real-time data is stored every one minute. We wait for the temperature of the 24 water-temperature measuring points to stabilize till no obvious fluctuation emerges for a maintenance time of more than 90 minutes, and then the test of this working condition is completed. After that, the data of the entire test process are saved and analyzed. In addition, in order to correct the heat power, the Qin is added to the water tank by the simulated heat source. Not all the heat added by the actual simulated heat source can be added to the water body of the tank. Therefore, we need to conduct a “blank test” on this test system. The processes are as follows: 1. When the daily test conditions are completed, the final stable data of the 24 water-temperature measurement points are read separately, and the average water temperature T1 at this time is calculated. 2. Next, the condensation end of the separated heat pipe radiator is covered with a thermal insulation box, and the time τ1 and the water level height H1 of the water tank are recorded at this time. 3. After one night and in the next morning, the data acquisition system is turned on, and at the same time, the readings of the 24 measuring points reflecting the water temperature are recorded, and the average water temperature T2 is obtained. The time τ2 and the water level height H2 of the water tank at this time are recorded. 4. Calculation Equation of heat leakage per unit time is as follows: q=

C · m · t τ

(1)

In Equation (1), q is the heat loss (kj/s); C is the specific heat capacity of water, and C = 4200 J/(kg·◦ C); m is the mass of the water in the tank (kg); τ is the elapsed time (s); and t is the water temperature difference (◦ C).

3 ERROR ANALYSIS For this test, in addition to the measurement device error, environmental error and personnel error, the heat loss from the heat exchange between the water tank and the surrounding environment should also be considered. In order to reduce the heat loss of the water tank, thermal insulation materials were used to insulate the outer wall of the water tank in the experiment. However, the top of the water tank is not insulated and there is a “thermal bridge” phenomenon where the insulation materials are combined, which cannot completely isolate heat dissipation. Therefore, the heat loss rate needs to be determined experimentally. Hence, after each completion of a set of test conditions, the “heat leakage test” must be carried out. The specific operation steps are described in Section 2.4. The test measurement results are shown in Table 4. Table 4. Heat leakage test data.

Frequency

Starting average temperature of water tank/◦ C

Average temperature at the end of the tank/◦ C

Experience time/s

1 2 3

78.8 79.09 77.36

63.89 60.11 60.59

43200 52500 54000

151

Take for example the calculation result of the first measurement. We can calculate the heat loss Q of the water tank: C · m · t × 3600 τ 4.18 kJ/(kg · ◦ C) × 1200 kg × (78.8 − 63.89)◦ C = × 3600 43200 s = 6.23 MJ/h Q = q × 3600 =

At the beginning of the first test, the total enthalpy of the water tank is C · m · t1 = 3.95 × 102 MJ; after 43200 s, the water tank loses about 74.8 MJ of heat, and the heat loss is 6.23 MJ/h; the heat loss per hour is almost equivalent to 1.58% of the initial total enthalpy, which is relatively low. In a similar way, it can also be calculated that the heat loss per hour for the second and third times is about 1.65% and 1.45% of the initial total enthalpy. Therefore, in the next analysis of the water tank system using the first law of thermodynamics, the heat leakage from the outer surface of the water tank to the surrounding environment is ignored.

4 RESULTS AND DISCUSSION 4.1 Heat dissipation capability of heat pipe According to the test results, using the general expression Equation of the first law of thermodynamics for any thermodynamic system: input energy – output energy = change of system stored energy, the thermal calculation of the equation is carried out for the thermodynamic system of this experiment. For the thermal system of this experiment, the water tank is taken as the research object. There is no mass in and out on the boundary surface of the water tank, and neither the macroscopic kinetic energy nor the gravitational potential energy changes. Therefore, the calculation is performed using the energy equation of the closed system. Assuming that the heat entering the system is Q, the power output of the system is W, and the change in the internal energy of the system is U, the energy equation of the closed system is (Lian 2007): Q = U + W

(2)

Equation (2) is the most basic closed system energy equation, which is applicable to both ideal gases and actual gases, liquids and solids. Thus, the following equations are listed: Q1 + (−Q2 ) + (−Q3 ) = U + W

(3)

In Equation (3) Q1 is the electrical work done by the adiabatic heating of the aluminum plate; Q2 is the heat leakage from the outside of the water tank facing the surrounding environment, which is ignored here; Q3 represents the heat dissipated to the surrounding environment through the heat pipe;  U is the change in the internal energy of the water in the water tank. The power W of the output system is equal to 0. Equation (3) is used to calculate the variation curve of the overall heat dissipation of the heat pipe inside the water tank with time when the ambient temperature is 25◦ C (see Figure 4b). Figures 4(a) and (b) show that the curve changes of the average water temperature and the overall heat dissipation capacity of the heat pipe present the same trend. On the one hand, no matter whether the heat dissipation method of the condensing end of the heat pipe is natural convection or forced convection, the average water temperature and the overall heat dissipation capacity of the heat pipe show a turning point around 95 mins. It stays around a fixed value; on the other hand, the greater the power of the simulated heat source, the more severe the change between the two around the turning point value (95 mins). This shows that when the two values are in the start-up stage of the heat pipe before the turning point, the overall heat dissipation capacity of the heat pipe at this stage 152

Figure 4. The average water temperature and the heat dissipation capacity of the heat pipe change with time.

is greatly affected by the isothermal distribution of the water tank, and the values of the two are after the start-up stage until the steady state. The process is the transition stage of the heat pipe. In the transition stage, the dominant factor affecting the heat dissipation capacity of the separated heat pipe is whether the internal working fluid circulation is in good condition; then the heat pipe, the water tank system and the surrounding environment reach a stable state stage. In the first stage, the isothermal characteristics of the heat pipe make the water temperature stratification in the water tank not obvious, the heat pipe works well, and the heat dissipation capacity continues to be stable. Finally, as the power of the simulated heat source increases, the overall heat dissipation capability of the heat pipe increases.

4.2 Average heat transfer coefficient of heat pipe According to the test data, using Equations (4) and (5), we can calculate the variation of the average heat transfer coefficient he at the evaporating end and the average heat transfer coefficient hc at the 153

condensing end of the separated heat pipe heat exchanger inside the water tank with time when the ambient temperature is 25◦ C. The results are plotted in Figures 5(a) and (b), respectively. he =

Qin Fe (T e − T a )

(4)

In the equation, he is the average heat transfer coefficient outside the evaporating end tube of the heat pipe, and the unit is W/(m2 ·◦ C); Qin represents the corrected heat source power; Fe is the outer surface area of the evaporating end tube (0.79 m2 ); T a is the average temperature of the adiabatic section; T e represents the average temperature at the evaporating end. hc =

Qin Fc (T e − T c )

(5)

where hc is the average heat transfer coefficient outside the tube at the condensation end of the heat pipe, the unit of which is W/(m2 · ◦ C); Fc is the outer surface area of the tube at the condensation end (6.02 m2 ); T a is the average temperature of the adiabatic section; T c is the average temperature of the condensation end.

Figure 5. The average heat transfer coefficient changes with time.

From Figure 5(a) and (b), it can be found intuitively that with the increase of the uniformity of the temperature field distribution of the water body inside the water tank, the average heat transfer coefficient of the evaporating end and the condensing end of the separated heat pipe heat exchanger gradually changes with time. This reflects from the side that the separated heat pipe heat exchanger 154

has unique advantages in adjusting the temperature uniformity of the water tank. In addition, the average heat transfer coefficient of the condensation end is much smaller than the average heat transfer coefficient of the evaporation end, which limits the overall heat pipe. The key to the heat dissipation capacity, however, is to make up for the small heat transfer coefficient by increasing the condensing end tube bundle, thereby increasing its heat exchange area with the air. Therefore, in the design of the condensation end of the heat pipe, the arrangement of the tube bundle, the condensation heat exchange area, the fin form, and the flushing method with the cold fluid should be mainly considered.

4.3 Analysis of water temperature uniformity Under the test conditions of working condition 4, with the elapsed time as the abscissa and the temperature gradient as the ordinate, the radial and axial temperature gradients of the water tank are analyzed. The temperature gradient is calculated by the vector calculation rule. The positive and negative signs of the ordinate in Figures 6 and 7 represent the relative temperature at both ends of the arrow.

Figure 6.

Radial temperature gradient.

Figure 7. Axial temperature gradient.

155

On the one hand, the maximum difference of the absolute value of the radial temperature gradient of the water tank is 0.036◦ C/cm, and the maximum difference of the absolute value of the axial temperature gradient is 0.013◦ C/cm. The radial temperature gradient of the water tank fluctuates obviously with time. The reason for this fluctuation is that the heat flux density of the simulated heat source in the radial direction has a great influence on the water temperature. Therefore, the evaporating end of the heat pipe should be placed as close as possible to the high radial heat flux density. On the other hand, the change of the axial temperature gradient in the second half of the test shows a certain stability and is in a dynamic equilibrium state, which reflects from the side that the isothermal performance of the heat pipe is very good, and the heating position of the simulated heat source affects the temperature uniformity of the water tank. It was weakened by the operation of the heat pipe. In the second half of the test, the large and small vortices formed by natural convection in the water tank did not change drastically, and the uniformity of the temperature field of the water tank performed well.

5 CONCLUSION Under the condition of constant high heat flux density, the separated heat pipe radiator in the test, on the one hand, has a superior ability to adjust the temperature uniformity of the water tank. The initial temperature of the water tank is in the range of 75 to 80◦ C. Under the heating power conditions listed in the experiment, the normal operation of the heat pipe makes the temperature field of the water tank gradually uniform and stable; on the other hand, the heat transfer characteristics of each part of the separated heat pipe radiator are good. The total heat transfer coefficient is relatively high. Under the condition that the heat dissipation method of the condensing end is forced convection heat dissipation, the average heat transfer coefficients of the evaporation end and the condensing end are 4362.18 W/m2 · ◦ C and 112.56 W/m2 · ◦ C, respectively. Under the condition of natural convection heat dissipation, the overall heat dissipation capacity of the separated heat pipe radiator is 1.6 to 1.8 kw. When the ambient temperature of the condensing end is in the range of 30 to 40◦ C, the heat dissipation effect is optimal; Under the conditions, the overall heat dissipation capacity of the separated heat pipe radiator is 6.4–6.8 kw, and the heat dissipation effect is optimal when the ambient temperature of the condensing end is in the range of 30–40◦ C.

ACKNOWLEDGMENTS The authors want to extend gratitude for the support from the 2021 Jiangsu Postgraduate Research and Innovation Practice Activity Project (SJCX21_0454).

REFERENCES Chen B.R., Chang Y.W., Lee W.S., etc. Long-term thermal performance of a two-phase thermosyphon solar water heater[J]. Solar Energy, 2009, 83 (7):1048–1055. Chen Lan, Su Junlin, Wu Yiwen. Experimental Research on Liquid Filling Rate of Separated heat pipes [J]. Journal of Shanghai University of Science and Technology, 2003(03):285–288. Chung J D, Cho S H, Tae C S, et al. The effect of diffuser configuration on thermal stratification in a rectangular storage tank[J]. Renewable Energy, 2008, 33:2 236–2 245. Company, W. E. Modular Floating Passive Cooling System 300 for Used Fuel Pools[R]. American: 2011. Esen M., Esen H. Experimental investigation of a two-phase closed thermosyphon solar water heater[J]. Solar Energy, 2005, 79 (5):459–468. Garrity P.T., Klausner J. F., Mei R. A flow boiling microchannel evaporator plate or fuel cell thermal management[J]. Heat Transfer Engineering, 2007, 28(10):877–884. Haller M Y. Methods to determine stratification efficiency of thermal energy storage processes: Review and theoretical comparison[J]. Solar Energy, 2009, 83:1 847–1 860.

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Synthesis, separation, and purification of cross-linked starch grafted polyacrylamide polymer flocculant Xiaohong Li & Xuekui Hao Department of Civil Engineering, Lanzhou Institute of Technology, Lanzhou, China

ABSTRACT: In the present work, the cross-linked starch was studied as a base material, the Ce4+ was selected as initiator of graft copolymerization, and acrylamide was grafted to prepare an environmentally-friendly polymeric flocculant by aqueous solution polymerization. The separation and purification of graft copolymerization reactants were studied. The results showed that the grafting reaction was simple, and the enzymatic degradation method was used to separate and purify the graft copolymer, which was safe and reliable, and provided a reference for the separation and purification of modified starch polymers.

1 INTRODUCTION It has been widely reported that the research and technology of grafting vinyl monomers to starch (Athawale 1998; Delval 2001, 2005), which was modified by grafting has attracted great attention, because the graft copolymer has greatly improved the physical and chemical properties and industrial applications of starch. Since Minoru Imoto discovered that starch could graft copolymerize with some monomers in water in 1962, many researchers have studied the graft copolymerization of starch with acrylamide. For example, Reyes et al. (1966) studied cerium ion induced graft copolymerization of acrylamide and acrylonitrile to wheat starch. Experimental results show that the concentration of monomer and initiator amount is the main factors influencing the graft under the condition of optimal grafting. The maximum grafting efficiency of acrylamide and acrylonitrile was 43.8% and 87% respectively, despite of the amount of acrylamide monomer is less than that of acrylonitrile, acrylamide and acrylonitrile formation is almost the same number of branched chains in the end grafted product (Dai Shugui 1997). Varmal (1983) found that the grafting rate of acrylamide was three times that of homo-polymerization in the presence of starch. In Butler’s report, aqueous starch graft acrylamide was synthesized in aqueous solution using cerium amine nitrate as initiator (Butler 1983). In the present work, the monomer ratio, initiation dose, reaction time, temperature, viscosity, molecular weight, and yield of the product are described in detail so that starch graft acrylamide can be popularized and applied.

2 PREPARATION PRINCIPLE The grafting mechanism of cross-linked starch to polyacrylamide is similar to that of starch to acrylamide. It forms a multi-dimensional network structure, because the cross-linking reaction of starch only bridges two or more starch molecules together, about one cross-linking bond per 100∼3000 dehydrated glucose units. The amount of cross-linking agent introduced into starch by 158

DOI 10.1201/9781003318569-25

cross-linking reaction is generally small. Therefore, the active functional groups in cross-linked starch are mainly alcohol-hydroxyl groups. Whether starch can react with acrylamide monomer depends not only on the structure and properties of the monomer, but also on the existence of activated free radicals on starch macromolecules. Free radicals can be produced by physical or chemical methods, but the most commonly used are chemical initiation methods, in which Ce4+ , H2 O2 -Fe2+ , K2 S2 O8 /KHSO3 , (NH4 )2 S2 O8 /NaHSO3 , KMnO4 are used as initiators. The grafting mechanism of Ce4+ was discussed in this paper. Graft copolymerization of cross-linked starch and acrylamide initiated by Ce4+ can be divided into three stages: chain initiation, chain growth, and chain termination. Initially, the complexation of Ce4+ and cross-linked starch leads to electron transfer. A free radical on the cross-linked starch backbone is generated, since the Ce4+ was reduced to Ce3+ . The free radical on the cross-linked starch backbone then leads to graft copolymerization of polar acrylamide monomer, forming a polyacrylamide side chain on the cross-linked starch molecular chain (Chang 2008). The reaction diagram is as follows:

Chain caused by:

St + Ce4+ → St• + Ce3+ + H+

Chain growth:

St + AM• → St − g − PAM St + AM• → St − g − PAM (OR PAM)

Chain termination:

St• + Ce4+ → St• + Ce3+ + H+

3 PREPARATION METHOD In the experiment, cross-linked starch (2 g) and distilled water (20 mL) were placed in a 250 mL four-mouth flask, which was installed with mechanical stirring, gas device, condensing tube, and thermometer. The cross-linked starch was stirred into a uniform paste at room temperature, and 40 mL of 40% acrylamide solution was added. Then, four flasks were placed into the water with a constant temperature of 45◦ C, uniform mechanical agitation was performed and nitrogen was injected to the flasks from the bottom. Nitrogen was used to eliminate oxygen in the reaction system, because oxygen has a remarkable inhibition to polymerization. If oxygen and free radicals react with each other, the polymerization will stop by disproportionation or coupling. After constant temperature (about 15 minutes), 0.1 mol/L ammonium cerium nitrate solution was added drop by drop. After 3 hours of polymerization, mechanical agitation was stopped to remove nitrogen and the solution was cooled to room temperature to obtain cross-linked starch grafted acrylamide crude products (Hao 2009).

4 SEPARATION AND PURIFICATION METHOD 4.1 Separation and purification of graft copolymer crude products The crude product of cross-linked starch graft acrylamide contains the following components: cross-linked starch graft polyacrylamide copolymer, acrylamide homopolymer, starch monomer and other residual small molecules (such as acrylamide, solvent, and initiator). The Soxhlet extractor was used to extract the dried graft copolymer crude products (Chang 2003). The experimental device of the Soxhlet extractor is shown in Figure 1. 159

The specific methods are as follows: 1.000 g crude product was weighed with an electronic balance and put into the Soxhlet extractor. The mixture of glacial acetic acid and ethylene glycol was used as solvent (60:40, V/V) for continuous reflux extraction for 8 hours. The homopolymer of acrylamide was separated and removed by extraction agent. The remaining solids in the extractor were precipitated and washed with methanol for three times, then filtered and dried in a vacuum drying oven at 60◦ C until constant weight. The product was quantitatively weighed, and a certain amount of 0.5 mol LNaOH solution was added and stirred at 50◦ C for 3 hours with magnetic force to dissolve the ungrafted starch. The graft products were filtered by a Bouchard funnel. The pure graft copolymerization product was obtained by precipitation and washed with anhydrous ethanol and acetone for three times and then dried (Athawale 1998, 1999).

Figure 1.

Soxhlet apparatus.

4.2 Separation of side chain of graft copolymer The starch on the graft copolymer chain was removed by acid hydrolysis in the most of literature (Athawale 1999; Reyes 1966). Because of the high acid hydrolysis resistance of the cross-linked starch, the enzymatic degradation method was adopted for the separation of the cross-linked starch grafted polyacrylamide side chain. The specific methods are as follows: after purified and dried by Soxhlet extractor, 1.00 g of pure grafting copolymerization product and 0.002 g of α-amylase were obtained by electronic balance, and placed in a 50 mL conical bottle; 10 mL distilled water was added and stirred by a magnetic stirrer. After 2 hours of reaction at a constant temperature of 60–65◦ C, the product was cooled to room temperature and filtered by a sand-core funnel. The filtrate was poured into a sufficient amount of acetone solution to extract side chain polyacrylamide, the extracted polyacrylamide was dissolved in warm distilled water, filtered and then washed with acetone solution once. The process was repeated twice, and the separated polyacrylamide was dried in a vacuum drying oven at 60◦ C to constant weight. 160

5 CHARACTERIZATION 5.1 Infrared spectrum analysis The dried starch, cross-linked starch and cross-linked starch grafted acrylamide samples were made KBr sample blocks and placed on the NEXUS 670SX infrared spectrometer of Nicolet in the United States for full-band scanning (scanning range: 4000∼400 cm−1 ). The FTIR spectra were drawn, as shown in Figure 2. As can be seen from the FTIR infrared spectra in Figure 2, comparing the infrared spectra of cross-linked starch and starch, we found no additional peaks. Therefore, comparing the infrared spectrum between cross-linked starch and cross-linked starch grafted polyacrylamide, it showed that primary amide characteristic absorption peak appeared at 1700 cm−1 , N-H deformation oscillation absorption peak of secondary amide appeared at 1665 cm−1 , and weak characteristic absorption peak of carboxyl group appeared near 1600 cm−1 . Stretching vibration peaks of -CH2 -O-CH appeared at 1081 cm−1 and 1016 cm−1 , respectively. These characteristic peaks could indicate that the product was a graft copolymer of cross-linked starch and polyacrylamide (Ni 2005).

Figure 2.

Infrared spectra of starch (a), cross-linked starch (b), and cross-linked starch grafted acrylamide (c).

5.2 Scanning electron microscope (SEM) The SEM was used to observe the surface structure of grafted polyacrylamide and the distribution of the particles by the “Hitachi-430” scanning electron microscope. 161

Figure 3a. SEM micrographs of starch.

Figure 3c.

Figure 3b. SEM micrographs of the cross-linked starch.

SEM micrographs of the cross-linked starch grafted polyacrylamide.

After spraying gold, the dried corn starch, cross-linked starch and cross-linked starch grafted acrylamide were fixed on the sample table. Therefore, their surface structures were observed by the American JSM-5600 low-vacuum scanning electron microscope (SEM). The representative electron microscopy photos were shown in Figures 3a–3c. Figure 3a Corn starch grains are round, oval, or polygonal with clear outline in shapes, at the same time it is scattered and isolated. The particle size is between 5 and 26 µm. It can be seen from Figure 3b that starch particles have different shapes and sizes. The brightness of the outer surface of the starch particles decreases, and there are obvious traces of connection between some particles. As can be seen from Figure 3c, starch particles no longer have sharp edges and corners, but it shows signs of wrapping and winding on the outer surface, and the degree of irregularity increases, which may be the result of the graft copolymer (Zhao 1996). 162

6 FLOCCULATION EXPERIMENT In the experiment, 4.0 g of high territory was put into a 100 mL calibration settlement tube with plug, and 90 mL distilled water was added. The solution was shaken at 5 times/s for 1 min, and then it was added the solution of starch grafted polyacrylamide flocculant with a concentration of 1.0%, and added distilled water to the full scale. The solution was shaken for 1 min, which placed vertically and timed. The height of the settlement interface was read at intervals, and 3 cm below the liquid level was quickly absorbed after 10 min. The absorbance (wavelength 550 nm,1 cm colorimetric pool) was measured by spectrophotometer (Pledger 1985). Flocculation effect was expressed by flocculation speed and relative absorbance.

7 CONCLUSION Based on the experiment presented above, the conclusions are obtained as below: (1) It is shown that the optimal synthesis conditions are: 40 g/L concentration of cross-linked starch, 6.67×10−4 mol/L concentration of cerium ammonium nitrate, 0.939 mol/L of acrylamide, 45◦ C reaction temperature and 3 h reaction time, the grafted copolymer of cross-linked starch polyacrylamide has higher graft rate and graft efficiency. The molecular weight of side chain can reach 6.34×105 . The turbidity removal rate of the product is 96.4%. (2) It is concluded that the feasibility of graft copolymerization was proved. The separation and purification products of each modified step were analyzed and compared by FTIR and SEM, which provided a reference for the separation and purification of modified starch polymers.

REFERENCES Athawale V D, Rathi S C. (1999) Graft Polymerization: Starch as a Model Substrate. J. Macromol. Sci., Pure Appl. Chem., 39 (3): 445–480. Athawale V D, Rathi SC, Lele V. (1998) Graft copolymerization on to maize starch – I. Grafting of methacrylamide using ceric ammonium nitrate as an initiator. Euro. Poly. J., 34 (2): 159–162. Athawale V D, Vidyagauri, Mumbai. (1998) Graft Copolymerization Onto Starch. 3: Grafting of Acrylamide Using Ceric ion Initiation and Preparation of its Hydrogels. Starch/Starke, 50: 426–431. Butler G B, Hogen T E, Dallas J M. (1983) US Pat. 4, 400, 496. Chang Qing. (2003) Flocculation of water treatment. Chemical Industry Press. Beijing. Dai Shugui. (1997) Environmental chemistry. Higher Education Press. Beijing. Delval F, Crini G, Janus L, Vebrel J, Morcellet M. (2001) Novel crosslinked gels containing starch derivatives. Polymers water interaction. Applications in waster water treatment. Macromol. Symp., 166: 103–108. Delval F, Crini G, Sabrina B, Claudine F, Giangiacomo T. (2005) Preparation, characterization and sorption properties of crosslinked starch-based exchangers. Carbohyd. Polym., 60: 67–75. Hao Xuekui, Chang Qing, Li Xiaohong. (2009) Synthesis, Characterization and Properties of Polymeric Flocculant with the Function of Trapping Heavy Metal Ions. J. Appl. Polym. Sci., 112(1): 135–141. Ni Y C. (2005) Structural Identification of Organic Compounds and Organic Spectroscopy. Beijing, Chain, 490–498. Pledger H, Young T S, Wu G S, Butler G B. (1985) Synthesis and Characterization of Water-Soluble StarchAcrylamide Graft Copolymers. J. Macromol. Sci. A., A22 (4): 415–436. Qing Chang, Xuekui Hao, Lili Duan. (2008) Synthesis of crosslinked starcg-graft- polyacrylamide-co-sodium xanthate and its performances in wastewater treatment. J. Hazard. Mater., 159(2–3): 548–553. Reyes Z, Rist C E. (1966) Russell C R. Grafting of polyacrylonitrile to granular corn starch by initiation with cerium. J. Polym. Sci., Part A: Polym. Chem., 4: 103l–1043. Varma I K, Singh O P, Sandle N K. (1983) Graft-copolymerization of Starch with Acrylamide. Angew. Makromol. Chem., 119: 183–192. Zhao Jiaxai, Xu Tao. (1996) Analytical electron microscopy practical manual. Ningxia People’s Education Press.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Research on measuring specific heat capacity of organic heat carrier at high temperatures by DSC Jingmiao Li, Jianhua Yang, Yan Rong & Dong Jin∗ China Special Equipment Inspection and Research Institute, Beijing, China

ABSTRACT: Many methods have been proposed to measure the specific heat capacity of organic heat carriers, but due to the volatilization of the organic heat carrier under heating, it is impossible to improve the specific heat test above 170◦ C. Alkane mineral oil, alkyl benzene, hydrogenated terphenyl, aromatic heat conduction oil and dibenzyltoluene were selected as experimental objects in this paper. The above experimental objects were sealed with a high-pressure crucible for differential scanning calorimetry analysis at a temperature ranging from 50◦ C to 280◦ C. The high-pressure crucible showed no almost no changes in quality before and after the test, and the sealing effect was good. Then, the thermal variation of the sample was analyzed and the specific heat capacity of the sample was calculated.

1 INTRODUCTION Heat conduction oil or heat conduction fluid, collectively referred to as organic heat carrier (Zhang 2013), is a kind of organic matter used as a heat transfer medium. The organic heat carrier appeared in the 20th century. Up to now, more than 100 organic heat carrier products have been developed in various countries, including alkyl benzene, benzyl toluene, hydrogenated tribiphenyl and so on. With the rapid development of petrochemical and chemical fiber industries in China, the demand of organic heat carriers as a high temperature heating and low temperature cooling medium is also increasing. Since 2000, China has implemented the energy-saving strategy, and the organic heat carrier boiler wins broad favor from enterprises because of its energy-saving properties of high temperature and low pressure. The annual demand for organic heat carriers reached 50,000–60,000 tons in 2010 (Wang 2013). The specific heat capacity is an important physical parameter used in boiler energy efficiency tests. The specific heat capacity of different kinds of organic heat carriers is different, which is related to many factors such as operating pressure, temperature, and material structure of organic heat carriers. Traditional calorimetry can measure the specific heat capacity. However, this method is difficult to achieve rapid measurement due to its complex measurement process and large sample consumption. In recent years, differential scanning calorimetry (DSC) has attracted the attention of the petrochemical industry for its advantages of a short test cycle, small dosage, convenient and quick operation. The method has been applied to the measurement of specific heat capacity of transformer oil, crude oil, and other liquids (Yuan 2013; Zhang 2013). In this paper, differential scanning calorimetry (DSC) and high pressure sealed crucible were used to measure the specific heat capacities of five kinds of organic heat carrier samples at 50◦ C∼280◦ C. According to the experimental results, we drew the temperature-specific heat capacity curve and fit the formula for the specific heat value of five samples. ∗ Corresponding Author:

164

[email protected]

DOI 10.1201/9781003318569-26

2 THE EXPERIMENT 2.1 The experimental sample The basic properties of five different organic heat carriers are shown in Table 1. Table 1. Organic heat carrier samples of 5 different components.

Alkane mineral oil Alkyl benzene hydrogenated terphenyl Aromatic heat conduction oil Dibenzyltoluene

Maximum allowable operating temperature (◦ C)

Density (20◦ C) (kg/m3 )

kinematic viscosity (40◦ C) (mm2 /s)

300

868.4

31.9

0.01

24

0.02

4.7

280

870.6

23.8

0.01

57

alkyl benzene > mineral alkanes. From the actual test process, benzene and its homologues have relatively good heat capacity in terms of heat transfer, while mineral oil has the worst heat capacity. According to the data and figures, polynomial fitting can be carried out for all kinds of samples, and the basic formula is: C = A + BT + CT2 + DT3 + ET4 + FT5 . As shown in the table, the aromatic hydrocarbons, hydrogenated tribiphenyl and alkyl benzene reached a correlation coefficient more than 0.99, which proves that the fitting formula is in good agreement with the result curve, and can be used as a reference for energy efficiency tests. The correlation coefficient between dibenzyltoluene and aromatic hydrocarbons was only 0.98 due to their thermochemical changes in the testing process. 170

Figure 9.

Plot of specific heat capacity.

Table 4. Formula coefficient table. A Hydrogenated terphenyl Alkyl benzene Alkane mineral oil Aromatic heat conduction oil Dibenzyltoluene

B

C

D

E

F

Adj. R-Square

−1.74136E-11

0.99617

−0.02921

5.20038E-4

−3.87307E-6

1.34264E-8

−0.81116

0.04677

−4.71943E-4

2.39393E-6

−5.88383E-9

5.6564E-12

0.99322

−5.00424

0.17615

−0.00213

1.27037E-5

−3.66738E-8

4.11613E-11

0.98020

2.24263

−0.03809

−3.99039E-6

1.25662E-8

−1.49458E-11

0.99943

−2.41265

0.11002

2.58383E-11

0.98716

1.7904

5.93946E-4 −0.00132

7.86091E-6

−2.2837E-8

4 CONCLUSION In conclusion, the specific heat capacity of organic heat carrier can be measured from 50◦ C to 280◦ C under the condition of high pressure sealed crucibles. In the testing process, the highpressure crucible can achieve a better sealing effect to reduce the influence of organic volatilization testing process. Through the test and comparison, we found that the specific heat values of the five organic heat carriers from high to low are aromatic heat conduction oil, hydrogenated terphenyl, dibenzyltoluene, alkyl benzene and alkane mineral oil. At the same time, according to the DSC curve in the testing process, aromatic hydrocarbons and hydrogenated tribiphenyl samples have the best stability, which is more suitable for the specific heat capacity test by differential scanning calorimetry. Alkyl benzene, dibenzyltoluene, and alkane mineral oil all have phase transformation or reaction change. According to the experimental process, it can be found that the DSC method has less sample consumption and higher testing efficiency. After the test, only a small amount of cleaning agent is 171

needed to clean the crucible. At the same time, it can reduce environmental pollution. Therefore, in the follow-up study of specific heat capacity testing, the method can be optimized to better apply to the testing of organic heat carriers and other aspects.

REFERENCES Tang Xun, Chen Shengzong, Wen Qing. (2013) Synthesis and application of benzyltoluene J. Hunan Chemical Industry, (02):62–65. Wang Jiaoling, SI Rong. (2013) Review of organic Heat Carrier Technology progress. C. The third National Boiler Water (Medium) Quality Treatment academic Exchange Conference. Yuan Kaijun, Han Xiaoqiang, Chen Guojin, et al. (2013) Measurement of specific heat capacity of crude oil by DSC J. Oil & Gas Storage and Transportation, 29(11):4. Zhang Jianwen,He Jinkun.(2013) Discussion on the influence of kinematic viscosity of organic heat carrier. J. Construction Materials & Decoration, 000(033):84–85. Zhang Jing, LI Junfeng, HE Jun, et al. (2013) Study on measuring specific heat capacity of transformer oil by DSC J. Transformer, 49(10):3.

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New energy technology and green energy saving and emission reduction

Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

A study on the innovation strategy of rammed earth buildings in Huizhou based on passive house technology Fuliang Sun & Wei Shu School of Art, Huangshan University, Huangshan, China

ABSTRACT: Nowadays, in the construction of new houses in Huizhou, people blindly resist “earth houses” and pursue “fashionable buildings” constructed with reinforced concrete. The few villagers who protect the memory of rammed earth construction misread it as “display specimens” and “performance projects”. From the starting point of creation, traditional rammed earth buildings and modern passive houses tread different paths that lead to the same destination. Through the mutual reference and integration of these two types, we construct a protective outer layer for the main part of the building, use the air circulation layer, high thermal insulation technology, and highly airtight building enclosures. Based on the high heat storage and good moisture absorption performance of rammed earth walls, this paper explores innovative strategies for low-cost green residential buildings in rural areas in Huizhou in the future, thus inheriting and developing the memory of construction with rammed earth in a “dynamic” way.

1 INTRODUCTION The mountainous area of southern Anhui is home to Huizhou culture, unique regional culture in China, in which the hall and patio buildings of Hui-style folk houses are the most prominent. They originated from the northern gentry who moved south to avoid wars during the Wei and Jin Dynasties. The Central Plains culture they brought was integrated with the local mountain culture. Based on the concept of “harmony between man and nature,” the original “buildings on stilts” developed into the form of “upstairs hall”. Then, with the prosperity of Huizhou merchants in the Ming and Qing dynasties, the financial resources became abundant, and the buildings were gradually improved and refined. The Hui-style hall-patio-style houses with a unique style and exquisite decoration were achieved. But at the same time, the cost of this kind of house

Figure 1.

Diverse Huizhou folk houses.

DOI 10.1201/9781003318569-27

175

was expensive, and it was difficult for most villagers to afford. In contrast, between the mountains and fields, the housing form that combined backward mountain productivity and civilized upstairs halls — earthen buildings, were more often seen. Among them, “Yangchan Village”, which has gained public attention in recent years, is its representative (Figure 1). But now, the unpretentious and rough earthen buildings were gradually eliminated by various contemporary rural constructions.

2 THE CURRENT SITUATION AND PROBLEMS OF CONTEMPORARY RURAL HOUSES IN HUIZHOU In recent years, thanks to the promotion of the escalating rural development policies of the state, the economy of Huizhou has developed rapidly, and foreign capital is abundant. Relying on efficient transportation and information network, rural construction in Huizhou is in full swing. There are three main forms: rural renovation and upgrading led by the government, residential renovation and construction spontaneously carried out by local villagers, and rural hotels and homestays that are driven by capital from the outside world (Figure 2). The first two are the main forms of housing construction for local villagers in Huizhou. The purpose is to improve the quality of houses and villages in Huizhou, and they are the core of the future development of Huizhou houses. This paper takes this as the research object. The latter is the construction of rural hotels and homestays driven by external capital under the influence of the development of the tourism industry. It is a capital behavior pursuing profit, and its service target is not the residents. This paper does not research this.

Figure 2. The type of contemporary rural construction.

2.1 Government-led rural transformation and upgrading The government-led rural transformation and upgrading refer to the pursuit of a better rural living environment by the villager collectives led by the government under the impetus of economic and social development trends. Economic factors play a crucial role in this behavior. Usually, villages close to cities have good overall economic development, which makes the upgrading of residential buildings in these places faster. At the same time, as a result of the expansion effect brought about by urban development, such rural buildings show an obvious urbanization phenomenon. They have unified planning and construction, effective land management and control, complete public facilities, and a layout model close to urban residences, ultimately presenting a beautiful countryside “similar to urban communities”. But this pattern consistent with current urban construction is a misreading of “beautiful”. This type of rural house has a serious tendency toward urbanization, the landscape is neat, and the appearance and layout are similar. The destruction of traditional neighborhood spaces has left many villages “losing their rural feelings”. As a result, all rural areas become “the same” as the cities. 176

2.2 Residential renovation and construction spontaneously carried out by local villagers The independent rural construction behavior of local villagers is rooted in the traditional Huizhou dwelling culture and is the epitome of the entire Huizhou society. The construction process is closely related to the villagers’ production needs, living conditions, and other factors. This is greatly different from the mode of architect-led construction in modern architecture. The traditional residential construction process is based on the daily life of the villagers, led by Fengshui masters and craftsmen, using local materials, integrating traditional culture, folk customs, and the meaning of blessing, thus establishing an emotional connection between the occupants and the houses. Compared with the architect-led modern mode, this construction mode is an organic combination of living and construction activities. It can more effectively express the living needs of the villagers at the material level, deepen the connection between the villagers, and pay attention to the feelings of the villagers at the spiritual level. However, this form of rural construction is greatly restricted by the culture and architectural quality of the villagers. In addition, due to the long-term lack of professional guidance and control of residential facade design, villagers build various styles of residential houses according to their aesthetic preferences, which has led to damage to the overall style of villages. 2.3 Impact of the above situation What’s worse is that most residential renovations in the outer suburbs and even the countryside will use the government-led new villages as a reference sample for residential construction. Compared with the government-led new village and image projects, these remote rural areas have poor economic conditions and low incomes. They lack financial security, coupled with the serious comparison mentality of the villagers, people blindly pursue large bays in buildings and go deeper. They are enthusiastic about reinforced concrete materials, but they resist the new composite materials that are more cost-effective. Due to these two factors, many rural houses nowadays look good, but their structure and thermodynamic properties are seriously damaged, resulting in a poor living experience. Huizhou traditional dwellings are rooted in the “slash-and-burn” lifestyle of local villagers. This way of life is still very common in the outer suburbs, which is completely different from the basis of the modern urban architectural model. Urbanized dwellings lack ancillary buildings and courtyard spaces, and their architectural patterns cannot adapt to the living habits of the villagers.

3 RAMMED EARTH BUILDINGS IN HUIZHOU AND THEIR VALUE Rammed earth buildings have a long history since the days of cave dwellings. The construction in Huizhou has always advocated the “unity of man and nature”, and rammed earth buildings can be seen everywhere in the remaining traditional Huizhou houses today. These rammed-earth construction techniques were formed by local villagers through long-term practice and summary during the period of low productivity. They are the direct embodiment of the simple view of the creation of the combination and symbiosis of architecture and nature. Today, our green village construction still needs such simple wisdom. 3.1 Huizhou and rammed earth architecture Huangshan City, the core area of Huizhou, belongs to the north subtropical humid monsoon climate. It is mild and rainy, with four distinct seasons, no extreme heat in summer, and no severe cold in winter except in high-altitude areas. In this area, the site selection of rural villages is mainly mountain areas with medium and low heights and hilly areas. Most of the mountain areas with medium and low heights have yellow soil with high gravel content; the hilly areas are mostly with red soil and purple soil with sticky texture, both of which are good rammed earth building materials. 177

The design of rammed earth buildings in Huizhou is based on local conditions and local materials, making the construction simple and low in cost. People use the soil near the construction site as the raw material, judge the soil quality through oral experience, mix vernacular materials such as gravel, river sand, mud, straw, and recycled old wall mud to improve the performance, increase the strength, enhance building stability and reduce the occurrence of cracking. The construction process is low-energy and pollution-free, and as long as it is constructed properly, it can resist erosion for hundreds of years. Even if the renovation is needed because the rammed earth material is renewable, it can be reused after the houses are demolished, and it can even be returned to the farmland as fertilizers, so almost no construction waste will be generated (Tao et al. 2019). These construction activities run through the process of the formation of Huizhou’s characteristic regional culture. They are constantly evolving, stabilizing, and eventually endowed with a unique cultural imprint. Compared with the local wood-structured hall-patio houses, the interior space of the hall-patio buildings is directly connected to the external environment through the patio. In winter, they can only maintain the temperature with the help of small isolation spaces and heating equipment inside. Earthen buildings in Huizhou have outstanding heat storage performance, and the interior space is warm in winter and cool in summer, making them especially suitable for use in winter when there is a lack of heating equipment (Figure 3). At the same time, because the rammed earth material has a “breathing” function, it can effectively adjust the indoor humidity. Compared with the smooth walls and floor tiles in modern buildings, they can better cope with the “south-returning days” in Huizhou.

Figure 3. Thermal performance data of building materials.

3.2 The contemporary value of rammed earth buildings in Huizhou The relationship between tradition and modernity is an eternal topic. With the advancement of technologies, architecture keeps moving forward. This forward process is not a negation of traditions. As far as the rammed earth buildings in Huizhou are concerned, due to the limitation of technology and productivity, they use local natural materials for construction. Its architectural idea of using materials sparingly not only saves costs, but also represents the builders’ attitude towards the environment, which is a manifestation of green design. At the end of the life cycle, earthen buildings will return to the earth, and the concept of “born in the earth” is the same as the “reduction,” “recycling,” and “reuse” of the contemporary prevailing ideas of sustainable development and green design. At the same time, their appearance is natural and simple, making full use of the characteristics of materials to directly show the simplicity and pure beauty of materials, which is similar to the aesthetics of materials such as “bare concrete” in modern architecture. 178

3.3 The policy of government On September 22, 2021, through the document No. 36: Opinions on Completely Accurately Implementing the New Development Concept and Doing a Good Job in Carbon Neutralization, the Central Committee of the Communist Party of China put forward the working principles of “national overall planning, conservation priority, two-wheel drive, smooth internal and external flow, and risk prevention.” In terms of urban and rural construction, it required promoting the low-carbon transformation of urban and rural construction and management models, vigorously developing energy-saving and low-carbon buildings, and accelerating the optimization of building energy consumption structure. It proposes the development of green farmhouses. At the same time, the development planning of building energy conservation and green building requires promoting the modernization and application of local traditional buildings such as new “rammed earth buildings” (Figure 4).

Figure 4.

Carbon emission data of building materials.

4 PASSIVE HOUSE TECHNOLOGY AND ITS SIGNIFICANCE The concept of a passive house was proposed in 1988 by Prof. Bo Adamson of Lund University in Sweden and Dr. Wolfgang Feist of the Institute of Housing and Environment Darmstadt in Germany (Zhang 2015). Its concept is an energy-saving technology that reduces building energy consumption through the intervention of relatively “passive” non-mechanical electrical equipment such as the building’s spatial form, enclosing structure, building materials, and structural design (Zhang 2014). In 1990, the world’s first passive building was built in Darmstadt, Germany. Since 2005, the world’s energy prices have risen sharply, and the related theories of passive buildings have quickly spread in construction, energy, and the environment. More and more professionals regard it as the most reasonable and effective technology for building energy saving. 4.1 Development of passive house technology in China In China, passive ultra-low energy buildings are defined in the following way: “Passive ultra-low energy buildings refer to such buildings: they maximize the thermal insulation performance and airtightness of the building envelope and make full use of passive technical means such as natural ventilation, natural lighting, solar radiation, and indoor non-heating heat gain, thus minimizing the need for heating and air conditioning, achieving a comfortable indoor environment and enabling people to live in harmony with nature” (Xu & Sun 2016). In the actual design, they mainly reduce the need for heating and cooling supply of the buildings to the greatest extent by adapting to the climatic characteristics and natural conditions, adopting enclosing structures with higher thermal insulation performance, building airtightness, and using 179

the high-efficiency technology of fresh air heat recovery. They make full use of interventions such as renewable energy to achieve buildings that provide a comfortable indoor environment with less energy consumption. For example, based on a full understanding of the natural conditions and climatic characteristics of the site, we rationally arrange the orientation of the buildings in the architectural design, set up shading facilities according to the needs, adjust the lighting, design the building openings that are conducive to natural ventilation, and select the building enclosure and thermal insulation technology in a targeted manner, to effectively enclose the buildings (Xu 2013). In this way, based on extremely low power consumption, oil, and other energy consumption, we can realize the automatic rise and fall of the indoor temperature according to the changes in the external environment, to meet the needs of heating and air conditioning, and ventilation of the buildings. In winter, we do not need to install heating equipment, but only use solar energy, the heat dissipation of necessary indoor equipment, and the body temperature of the occupants to achieve the purpose of keeping warm. In summers, we can dispense with air conditioning, and use specially designed ventilation devices to achieve cooling purposes. 4.2 The feasibility of passive house development in Huizhou By comparing the long-term climate data of Huizhou with Berlin, Germany, we can find that the temperature trends in these two places are similar throughout the year, and both belong to the type of warm summer and cold winter. In the same seasons, the temperature in Huangshan is slightly higher, but the data is not much different (Figure 5). In addition, there are many mountains in the Huizhou region, with a maximum altitude difference of nearly 1,700 meters. Most of the villages are in hilly and mountainous areas. The temperature reduction brought by the altitude can completely offset the differences in the data. These similar characteristics indicate that the passive house technology that originated in Germany has the same adaptability to Huizhou. In the future design of low-energy-consumption green residential buildings in Huizhou, we can learn from and use many research findings and mature technologies of passive houses in Germany. Considering that there is a lot of rain in spring and summer in Huizhou and the air humidity is high (Figure 6), we only need to adjust and improve the dehumidification and moisture prevention according to the specific conditions of local areas.

Figure 5. Temperature data of the two places.

5 INNOVATION STRATEGIES OF RAMMED EARTH BUILDINGS IN HUIZHOU BASED ON PASSIVE HOUSE TECHNOLOGY Houses are the material expression of the ideal environment. The construction of green farmhouses should be based on the local and regional features, starting from the experience of the rural living process, combining traditional methods and folk wisdom, to explore the methods and strategies for the design and construction of modern rural houses, thus realizing the villagers’ autonomous house construction behavior without the participation of architects, enabling rural residential architectural art phenomenon to realize real regional characteristics. 180

Figure 6.

Humidity, rain, and sunshine data of the two places.

5.1 Problems of traditional rammed earth buildings in Huizhou The traditional raw soil building walls in Huizhou have relatively good thermal insulation and airtightness. However, due to the limitations of building layout structure, construction technology, and auxiliary materials, they have many defects in the airtight property of the enclosing structure. In the construction of traditional rammed earth buildings in Huizhou, to protect the structural strength of the rammed earth walls and prevent the intrusion of ground moisture, people use gravel at the lower part of the wall and leave ventilation holes on the foundation, which creates thermal bridges that accelerate heat loss from the inside of the buildings. Due to the limitation of technical conditions, the buildings use simple wooden windows with poor airtight performance. The enclosure structure of the roof is also very simple and with many gaps, and it does not have airtightness and heat insulation. Some buildings adopt an open patio layout, and the indoor space is directly connected to the outdoor space. As a result, the airtightness and thermal insulation of the enclosure structure are almost lost (Figure 7).

Figure 7. Traditional rammed earth.

5.2 The strategies for the innovation of new rammed earth buildings In the future design of rural raw soil houses in Huizhou, we should focus on local materials and structures with low cost, low energy consumption, and easy construction, integrate the relevant technologies and strategies of passive house design, and fully exploit and utilize solar energy technology and other active green energy-saving technologies with low cost, high efficiency and 181

cost-effectiveness, trying to avoid the use of active technologies with the high cost and high energy consumption. Based on fully studying the structural characteristics of traditional raw soil buildings, we should design and select according to the local climate characteristics of Huizhou, such as moderate sunlight, humidity and rain, hot summer and cold winter, add a protective outer layer to the main body of the building enclosure, leave a gap between the two layers, and turn it into the structure of the air circulation layer. This is the core innovation in the design strategy proposed here (Figure 8).

Figure 8.

Design strategies of the enclosure structure.

5.3 Protective outer layer and air circulation layer The protective outer layer is outside the main structure of the building, its structure is relatively thin, and it is connected and reinforced by the embedded parts in the main enclosure structure. This layer directly faces the natural environment in which the building is located, and its main functions are to shield, protect, decorate and provide an installation platform for ancillary equipment. The choice of materials is flexible and diverse. Because this layer is the appearance expression of the building and the structure is relatively thin, the materials should be as light and beautiful as possible, and the requirements for weather resistance are high. If rammed earth material is selected, its properties need to be properly improved, especially water resistance property. There is a certain gap between the protective outer layer of the house and the main structure layer, which are connected and extend from the foundation to the roof. This gap is the air circulation layer. The presence of the air circulation layer minimizes the direct contact between the shield layer and the main structure layer. The role of the protective layer on the main structure of the building is similar to the shading and protective role of an “umbrella.” Due to this effect, the main structure of the house is no longer directly affected by external factors such as sun and rain; instead, it needs to face the circulating air. In addition, the super-insulation layer installed on the surface of the rammed earth body makes the temperature of the surface of the rammed earth body of the house change slowly and makes the temperature difference small. Finally, the influence of the external factors on the indoor environment is minimized, and the thermal environment is very stable. At the same time, the air circulation layer is connected to the crushed stone foundation of traditional rammed earth or the foundation overhead layer. This allows the airflow with a relatively stable temperature 182

in the soil layer to enter the air circulation layer under the action of the chimney effect, which further stabilizes the external environment of the main body of the house. In addition, we can also use ventilation equipment to connect the indoor space and the air circulation layer and exchange air between indoor and outdoor spaces according to the characteristics of different seasons and the needs of the indoor environment.

5.4 Enclosure structure of the main body and technical details (Figure 9)

Figure 9.

Enclosure structure of the main body and technical details.

The main structure of the building is built with rammed earth, giving full play to its green and lowcarbon advantages. Furthermore, the construction of rammed earth buildings is done with the help of simple and modern tools such as mixing mixers and electric (pneumatic) rammers. Compared with the labor-intensive traditional rammed earth process, it not only achieves higher strength and a more uniform structure of the rammed earth, but it also greatly reduces the demand for labor, which is more in line with the current situation of rural areas in Huizhou. During the construction process, metal prefabricated rammed earth molds are used, which are easy to operate and have high precision. The surface texture of the earth wall is uniform, and the material aesthetics of rammed earth is fully demonstrated. Compared with smooth walls such as cement, ceramic tiles, and latex paint, the rammed earth surface directly facing the interior space has a “breathing” function, and can effectively adjust the indoor humidity, and air quality, especially the moisture absorption performance is outstanding. (Mu 2016) It has an obvious effect on regulating the humidity of the indoor environment without forming condensed water on the surface of the wall, and can effectively cope with the “south-returning days” and “the rainy season.” During the construction stage, structural components such as door and window frames, flue gas passages, and closet supports are directly embedded into the rammed earth structure wall. Due to the maturity of modern metal profile technology, the shapes of components have become more flexible, the constructive structural performance is outstanding, and the appearance and interior forms of buildings have been greatly enriched. 183

5.5 Assistance by technologies Super-insulation and waterproof materials are laid on the side of the main body of the house facing the air circulation layer. The foundation moisture-proof insulation layer is set on the stone foundation. While isolating the ground moisture, it blocks the thermal bridge between the interior and the foundation. This can not only take advantage of the traditional stone foundation, but also keep the indoor environment stable. The house sets up the basement as an auxiliary function space, where geothermal equipment can be installed to fully use the geothermal energy in the basic soil layer. When designing, the floor height can be adjusted according to specific needs, saving costs. The wall is mainly insulated and sealed, especially near the embedded holes such as doors and windows, be sure to cut off the thermal bridge. The pre-embedded frame, based on the lighting and architectural modeling, and functional requirements of the modern living space, should try to use broken bridge insulation profiles with high thermal performance. At the same time, window products with a good thermal insulation effect should be used. When the budget allows, tripleglazed + inert gas + LOW-E glass exterior windows can be used. The traditional roof structure is simple, and the thermal insulation and rainproof effect are poor, so the design of the roof is particularly important. The structure of the outer covering of the new roof of the house is similar to that of the traditional roof, and the installation fulcrum of the solar energy equipment can be added according to the needs. Rammed earth cannot be used for the main structural layer. Builders can directly use waterproof, thermal insulation, thermal insulation, fireproof materials, and highstrength auxiliary materials to build super-insulated roofs and design the structural bearing strength according to the roof equipment.

6 CONCLUSIONS Based on integrating scientific site selection, airtight enclosure, super thermal insulation, and scientific ventilation in passive building design, the new passive earth houses built by this design strategy have an air circulation layer in the enclosure. Shading the building effectively reduces the heat radiation received by the main enclosure and provides a relatively stable external environment for the main body of the building. At the same time, with the assistance of modern thermal insulation materials, all-around airtightness and thermal insulation protection without thermal bridges are achieved. The advantageous properties of rammed earth and auxiliary materials are fully exploited, to meet the requirements of the airtightness standard of passive house enclosures and minimize the uncontrollable interference of the external environment to the indoor environment. Due to the heat shielding effect of the air circulation layer, the investment in modern insulation materials with high carbon emissions is greatly reduced, which reduces construction costs and improves the sustainability of the buildings.

ACKNOWLEDGMENTS This work was financially supported by the key research projects of Humanities and Social Sciences in colleges and universities inAnhui Province “research on the protection and innovation of Huizhou native residence in the context of passive architecture” (SK2020A0483) and the teaching research project in Anhui Province “research on the teaching mode of environmental design professional practice integrating Huizhou culture” (2020jyxm1785).

REFERENCES Mu Jun. (2016). The Excavation, Renewal, and Inheritance of the Tradition of Raw Soil Construction. J. Journal of Architecture. (04):1–7.

184

Tao Yan, Hou Min, Chai Dong, Tian Yi, He Yingcheng, Tao Zhong, Yu Hong. (2019). Research on Seismic Reinforcement Method of Raw Soil Houses in Chuxiong, Yunnan Province. J. Engineering Seismic Resistance and Reinforcement. 41(04):133–139. Xu Wei, Sun Deyu. (2016). Compilation Ideas and Key Points of Technical Guidelines for Passive Ultra-Low Energy Green Buildings. J. Engineering Construction Standardization. (03):47–51. Xu Wei. (2013). Research on Building Energy Conservation Planning and Design in Ganpo Area. D. Nanchang University. Zhang Feng. (2014). An Analysis of Urban Drainage and Sewage Treatment in Northern Anhui. Anhui Architecture. 21(06):155+160. Zhang Jun. (2015). Comparison of Carbon Emissions of Different Roof Structures of Passive Houses. D. Qingdao University of Technology.

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Does energy-saving technological progress effectively promote the energy-saving and CO2 emission reduction? Binfeng Liu School of Economics, Sichuan University Jinjiang College, Sichuan, China

ABSTRACT: Low-carbon economy is one of the important tasks of economic and social development in the world. China’s carbon emissions accounted for 30.7% of the world’s carbon emissions. China needs to constrain its energy consumption and carbon emission. Technological progress is considered the most effective implication. This paper narrows technological progress to energy-saving technological progress and deeply investigates the influence of knowledge stock of energy-saving patents on energy intensity and carbon dioxide intensity. The empirical results show that energy-saving technological progress is conducive to constraining China’s energy intensity and carbon intensity. Based on the findings, some insightful policy implications for China to constrain energy intensity and carbon intensity are put forward.

1 INTRODUCTION With the process of urbanization and industrialization through the concentration of factors such as labor, capital, and technology, China has achieved a remarkable development miracle. However, the traditional extensive development model has also led to serious resource and environmental problems. According to the World Energy StatisticalYearbook (70th edition) released by BP, in 2020, global carbon emissions were 32.28 billion tons, and China’s carbon emissions reached 9.899 billion tons. China’s carbon emission is more than any other country. To relieve the pressure of energy consumption and reduce carbon emissions, the Chinese government must deal with the relationship between economic development and environmental protection. China must undertake the obligation of carbon emission reduction. Although China’s reliance on coal for energy consumption cannot be changed, it can continuously tap the potential for energy efficiency improvement and carbon emission reduction in various industries and regions from the perspectives of industrial structure, technological innovation, and environmental regulation to achieve the dual carbon goals. Technological progress is considered the most effective implication to cut energy consumption and carbon emissions. The improvement of its technical efficiency is conducive to promoting carbon dioxide emission reduction to a certain extent (Guo 2012). By applying path analysis, Gui et al. (2017) confirmed technological progress is the most effective way to decrease carbon intensity (Gui et al. 2017). Huang et al. (2018) investigated the effect of domestic R&D on China’s regional carbon intensity and concluded domestic R&D is conducive to reducing carbon intensity (Huang et al. 2018). Decomposing the LMDI model, Gao and Zhu (2020) found increment of research input has little constraints on carbon emission. Still, improvements in research efficiency and industrial structural upgrade do (Gao & Zhu 2018). Technological progress can influence factor utilization efficiency, which affects energy consumption and carbon emissions. Fisher, Vanden, and Jefferson (2006) concluded that energy price and technological progress are important factors affecting the energy intensity of enterprises, and independent technological innovation and imported technology have different effects (Fisher et al. 2006). By applying the data from 36 industrial sectors in China from 1999 to 2010, Wang and Qi (2014) found that biased technological progress significantly impacts energy intensity (Wang & 186

DOI 10.1201/9781003318569-28

Qi 2014). Huang and Chen (2020) found that continuous technological progress is conducive to better environmental performance (Huang & Chen 2020). According to the literature review, the existing studies focus on the effects of overall technological progress. This paper has two major marginal contributions. First, we narrow technological progress to energy-saving technological progress, and the influence of knowledge stock of energy-saving patents on energy intensity and carbon dioxide intensity is investigated. Second, based on China’s provincial panel data from 2005 to 2019, the dynamic GMM estimation method analyzes the effects of energy-saving technological progress on energy intensity and carbon emission. 2 METHODOLOGY AND VARIABLES 2.1 Research model To explore the effect of energy-saving technological progress on energy demand and carbon emission, the basic models are described as follows: ln EIi,t = α0 + α1 ln ERDi,t + α2 ln SECi,t + α3 ln ESi,t + α4 ln OPENi,t + εi,t

(1)

ln CIi,t = β0 + β1 ln ERDi,t + β2 ln TLLi,t + β3 ln ESi,t + β4 ln OPENi,t + εi,t

(2)

Where i and t refer to provinces in China and years from 2005 to 2019, respectively. EI and CI denote the energy intensity and carbon intensity, respectively. ERD indicates energy-saving technological progress. α0 and β0 denote the constant, and α1 − α4 , β1 − β4 are the regression coefficients for each variable, ε is the stochastic disturbance term. lnISU, lnES, lnOPEN, and lnTLL indicate industrial structure, energy structure, trade openness, and industrial structure optimization, respectively. Considering the continuity effects of energy consumption and carbon emissions, our models include the first-order lag of lnEI and lnCI as Models (3) and (4): ln EIi,t = α0 + δ ln EIi,t−1 + α1 ln ERDi,t + α2 ln SECi,t + α3 ln ESi,t + α4 ln OPENi,t + εi,t

(3)

ln CIi,t = α0 + δ ln CIi,t−1 + α1 ln ERDi,t + α2 ln TLLi,t + α3 ln ESi,t + α4 ln OPENi,t + εi,t

(4)

2.2 Variables Energy intensity is defined as the ratio of the total energy consumption to the provincial GDP. Carbon intensity is calculated as the ratio of provincial CO2 emissions to gross domestic product. There were no official statistics on China’s provincial CO2 emissions, so the carbon emissions of each province are computed following the guidelines in IPCC (2006) (IPCC 2007; Huang et al. 2020). The data on energy consumption of each type and provincial real GDP (the base year is 2000) come from the China Energy StatisticalYearbooks and China Provincial StatisticalYearbooks, respectively. Energy-saving technological progress (lnERD) is defined as the knowledge stock of energysaving patents by considering the diffusion and depreciation rate (Lin & Zhu 2019). In this paper, energy-saving patents include invention and utility models (Huang et al. 2021). The calculation formula is as follows: ERDit =

t

EPit × exp [ − β1 (t - j)] · {1 - exp[ -β2 (t - j)]}

(5)

j=1

Where ERD denotes the knowledge stock, EP denotes the energy-saving patents, including invention and utility models. β1 is the depreciation rate, which has a value of 36%. β2 represents 187

the diffusion rate and has a value of 3% (Popp 2002). The data on each energy-saving patent comes from the Patent Search System of the State Intellectual Property Office of China. Industrial structure (lnISU) is defined as the economic output share of the secondary industry in GDP. Industrial structure optimization (lnTLL) denotes the Theil index of provincial industrial structures. Energy structure (lnES) is defined as the ratio of coal used to total energy consumption. The data on coal use and energy consumption can be collected from the China Energy Statistical Yearbooks. Trade openness (lnOPEN) is denoted as the ratio of the total imports and exports to GDP. The corresponding data on exports, imports and GDP are collected from the China Provincial Statistical Yearbooks. 2.3 Data In Tibet, Macao, Taiwan, and Hongkong, the statistical caliber is inconsistent, and the data is seriously missing, so this paper applies a panel dataset covering 30 Chinese provincial regions from 2005 to 2019. Some missing data are supplemented by the moving average method. To reduce the effect of heteroscedasticity, all variables are treated with a natural logarithm. The definitions and descriptive statistics of all the variables are reported in Table 1. Table 1. Definitions and descriptive statistics of the variables used in this paper. Symbol Definition (Unit)

Mean

Std

Min

lnEI

−0.053

1.384

−5.353

2.304

3.966

5.067

0.004

30.485

3.139 3.797

1.835 0.222

1.351 2.785

7.404 4.119

2.928 4.116

0.788 0.498

0.157 0.573

4.945 5.169

2.884

0.980

0.237

5.148

lnCI lnERD lnSEC lnTLL lnES lnOPEN

ln form of energy consumption divided by gross GDP (ton/104 Yuan RMB) ln form of carbon emissions divided by gross GDP (ton/104 Yuan RMB) ln form of the knowledge stock of energy-saving patents ln form of the percentage of the added value in the secondary industry to GDP (%) ln form of the Theil index of industrial structure (%) ln form of the share of coal use in total energy consumption (%) ln form of the ratio of total imports and exports to GDP (%)

Max

3 RESULTS AND DISCUSSION Considering the lagged term of the green industrial agglomeration and potential endogeneity issues in our model, we use the GMM approach to resolve the potential endogeneity (Hao et al. 2020). The corresponding SYS-GMM estimated results of empirical models (1)–(4) are presented in Table 2. Before analyzing the estimated results, we need to test the results of SYS-GMM. The consistency of the SYS-GMM estimators depends on whether the selected lag order is reasonable and the explanatory variable for the difference is an effective instrument (Chen et al. 2018). The result of the Hansen over-identification test and AR(1) and AR(2) autocorrelation tests confirm the validity and reliability of the SYS-GMM estimators (Arellano & Bond 1991). In Table 2, Columns (1), (2), (3), and (4) show the lag coefficient of lnEI and lnCI is positive and significant, implying that energy intensity and carbon intensity both exert a strong inertia effect over time. The coefficients of energy-saving technological progress are −0.0750, −0.928, −0.0661, and −0.644, respectively, and significant at the 1% level. Energy-saving technological progress is helpful to the transformation of the economy from traditional extensive growth mode to modern intensive development mode. It provides technical conditions for transforming traditional 188

Table 2. Estimation results for panel dynamic models. Variables L.lnEI L.lnCI lnERD lnISU lnTLL lnES lnOPEN constant AR(1)b AR(2) Hanse(p-value)c

(1) lnEI

(2) lnCI

0.120***a −0.0750***

0.219*** −3.473** −0.108 30.00 (0.849)

(3) lnEI

(4) lnCI

0.0605*** 0.152*** −0.928***

6.254*** −2.034** 0.938 29.87 (0.853)

−0.0661*** 1.010*** −1.630*** −0.522*** 4.562*** −3.228*** −0.650 29.65 (0.832)

0.0367*** −0.644*** −0.107 5.468*** −0.0739*** −16.11*** −1.923** −0.391 28.75 (0.861)

Notes: (a): ***, ** and * denote significance at the 1%, 5% and 10% levels, respectively. (b): The AR(1) and AR(2) are the first and second-order autocorrelations tests respectively. (c): The p-value for the Hansen test is given in parentheses.

polluting industries and forming green production modes and lifestyles to improve energy utilization efficiency and reduce energy consumption and carbon emissions. Concerning the control variables, the coefficient of the industrial structure (lnISU ) is positive and significant at a 1% level, implying reducing the share of the secondary industry will help reduce energy intensity. Industrial structure optimization (lnTLL) negatively affects the carbon intensity, but the coefficient is not significant. The coefficient on lnOPEN is negative and at a 1% significance level. One possible explanation behind the negative relationship is that opening wider to the outside world will help save energy and reduce emissions. The coefficient of energy structure (lnES) in Model (4) is 5.468 and significant at a 1% level, revealing that the growth of coal use is bad for constraining the carbon intensity.

4 CONCLUSIONS AND POLICY IMPLICATIONS This paper explores the effects of energy-saving technological progress on energy consumption and carbon emission using China’s provincial dataset. The results of the panel dynamic model reveal a negative relationship between energy-saving technological progress and energy consumption and carbon emission. The improvements in trade openness and industrial structure are helpful to cut energy and carbon intensity. Based on the above conclusions, we put forward some insightful policy implications for China to effectively achieve the dual carbon goal. First, we should accelerate green technological innovation and promote the green industrial transformation to promote ecological and environmental governance. Give priority to conquering energy resources and environmental protection technology, determined to solve the major bottleneck restricting the development of economic and social problems. Pay special attention to climate change, energy-saving, and emission reduction work. Focus on science and technology and strengthen the comprehensive utilization of waste main pollutant control and management technology development and integration model. We will acquire more core technologies in key areas such as new energy and aerospace, vigorously develop high-tech industries, and optimize and upgrade the industrial structure. It is necessary to let enterprises play the principal role in innovation, encourage universities and research and development institutions to tackle key problems in energy conservation innovation, and master the research, development, and application of key technologies for energy conservation and emissions reduction. 189

Second, we should continue to deepen opening-up, strengthen international exchanges and cooperation in energy conservation, emission reduction, green production, and other technical fields, and actively introduce foreign investment and sophisticated technologies to alleviate the shortage of capital and technology in the less-developed central and western regions. We must balance domestic development with an opening to the outside world, actively do a good job in all aspects of opening to the outside world and enhance our ability to participate in international cooperation and competition. Third, we shall continue to adjust industrial structure and realize industrial upgrading. To cut carbon emissions in China, we must curb carbon emissions growth and make efforts to achieve an overall strong decoupling state. It is necessary to optimize the industrial structure to reduce the proportion of secondary industry output value while guaranteeing sustainable economic growth. We should seize the historical opportunity of the current industrial iteration and upgrading to actively cultivate the new economy and replace old growth drivers with new ones. On the one hand, we should focus on basic research at the forefront of science and technology, increase investment in capital and personnel, and actively cultivate strategic emerging industries such as new energy and new materials. On the other hand, we will actively promote the in-depth integration of 5G artificial intelligence and other new-generation Internet technologies with traditional industries to form new forms and models of business that link online and offline and transform traditional industries from low-end to medium-high-end. Last but not least, we should promote fair trading and improve the carbon rights market. The government should formulate laws and regulations about how to standardize the behavior of the carbon trading market and make use of the means to strictly implement carbon trading. The government should accelerate the establishment and improvement of carbon markets, especially to speed up the pilot area in the central and western regions to carry on the scientific research under correct guidance, to effectively use the market mechanism of administrative measures to control carbon dioxide emissions. Our findings and policy implications are conducive to controlling the energy intensity and carbon intensity in China. However, there are two main limitations in our analysis. First, due to data limitations, some important control variables may be omitted. Second, there may be some influencing channels, such as the urbanization level, and foreign direct investment.

ACKNOWLEDGMENTS This work was financially supported by Sichuan University Jinjiang College 2021 Young Teachers’ Scientific Research Fund Project (QNJJ-2021-B06).

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Hao, Y., Zheng, S.Q., Zhao, M. et al. (2020) Re-examining the relationships among urbanization, industrial structure, and environmental pollution in China — new evidence using the dynamic threshold panel model. Energy Reports, 6(28): 28–39. Huang, J.B., Chen, X. (2020) Domestic R&D activities, technology absorption ability, and energy intensity in China. Energy Policy, 138:111184. Huang, J.B., Liu, Q., Cai, X.C., Hao, Y., Lei, H. (2018). The effect of technological factors on China’s carbon intensity: new evidence from a panel threshold model. Energy Policy, 1005: 32–42. Huang, J.B., Wu, J., Tang, Y.E., and Hao, Y. (2020) The influence of openness on China’s industrial CO2 intensity. Environmental Science and Pollution Research, 27(21). Huang, J.B., Xiang, S.Q., Wang Y.J., Chen, X. (2021) Energy-saving R&D and carbon intensity in China. Energy Economics, 98, 105240. Intergovernmental Panel on Climate Change (IPCC). Climate change 2007: the fourth assessment report of the intergovernmental panel on climate change. England: Cambridge University Press; 2007. Li, L.S., Zhou, Y. (2006) Can technological advances improve energy efficiency? —Empirical test based on Chinese industrial sector, Management World, (10): 82–89. Lin, B., & Zhu, J. (2019). Determinants of renewable energy technology innovation in China under CO2 emissions constraint. Journal of Environmental Management, 247, 662–671. Popp, D. (2002) Induced innovation and energy prices. Am. Econ. Rev. 92(1), 160–180. Wang, B.B., Qi, S.Z. (2014) Biased Technological progress, factor substitution and China’s industrial energy intensity. Economic Research Journal, (2):13–17.

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An experimental and numerical study on strengthening collapsible loess foundation with plain soil compaction pile Xiaochun Zhang, Yizhen Jia, Liqing Zhou & Yutong Liu Qingyang power supply company of State Grid Gansu Electric Company, QingYang, China

Yongdong Yang School of Civil Engineering, Longdong University, Qingyang, China

ABSTRACT: The bored compaction pile is one of the most effective methods to treat collapsible loess foundation and improve its bearing capacity. The collapsible loess foundation of a proposed project is treated by a plain soil compaction pile, and the field load test is carried out. The test includes different pile length conditions and different pile spacing conditions. Based on settlement displacement and compaction coefficient, the foundation treatment effect is evaluated, and the settlement displacement is verified by numerical simulation. The results show that when the pile spacing is the same, the longer the pile length, the longer the soil reinforcement area, and the smaller the displacement and settlement. The reduction of pile spacing can effectively improve the bearing capacity of the foundation, and the longer the pile length, the more obvious the effect of improving the bearing capacity of the foundation.

1 GENERAL INTRODUCTION Collapsible loess is a kind of unsaturated under compacted soil, which has the characteristics of large pores and vertical joints. Collapsible deformation caused by external load and self-weight pressure is a kind of unstable deformation with a large sinking amount and fast sinking speed, which is harmful to buildings (Mu 2010). Qingyang City belongs to the second area (Longdong area) in the engineering geological division of collapsible loess in China. The collapsible loess with self-weight is widely distributed, the thickness of the collapsible loess is large, the collapsible grade of the foundation is high, and the collapsibility is sensitive. The bored compaction pile method is used to treat collapsible loess foundation, which can effectively eliminate the collapsibility of soil and improve the bearing capacity of the foundation (Ji 2015; Liu & Shen 2009). The bored compaction pile composite foundation is also called bored rammed expanded compaction composite pile. Deep dynamic compaction (DDC) in the hole is to pre-drill the foundation to be treated, then feed into the hole, and then tamp in the hole with a special heavy hammer, so that the filler can be squeezed laterally, and the soil can be compacted laterally or squeezed (mixed and replaced) into the soil layer laterally (Liu et al. 2007; Zhao 2014). A plain soil compaction pile is to use plain soil as filler to squeeze soil into holes in the foundation using immersion tube, impact, or explosion expansion, to eliminate the collapsibility of loess and improve the bearing capacity of the foundation. In this paper, a field load test of the collapsible loess foundation of a proposed project is carried out and verified by numerical simulation. Focuses are on comparing the tests and numerical studies under different pile length and pile spacing conditions and evaluating the foundation treatment effect. 192

DOI 10.1201/9781003318569-29

2 STUDY AREA 2.1 Profile of the study area The area where the project is located belongs to the hinterland of Longdong Loess Plateau, where a complete loess stratum of about 250 m is developed. Therefore, the surface loess stratum in the loess tableland landform area of this area is distributed in extremely thick layers. Late Pleistocene aeolian loess, namely Malan loess, is widely distributed on the surface. The collapsible loess layer of the site is about 23.5∼28.5 m thick. Because the loess samples are mixed with a small number of ginger stones and the grain size is large, the loess foundation of the site is comprehensively evaluated as a Class IV (very serious) collapsible site with self-weight. Given the large thickness and strong collapsibility of collapsible soil layer in the construction site, and the lack of a good natural bearing layer and pile foundation bearing layer, the buildings (structures) in the proposed site do not have the conditions to adopt a natural foundation, so foundation treatment must be carried out on the site. Combined with the actual situation of the site and regional construction experience, it is suggested that a lime-soil compaction pile should be used for foundation treatment, and shallow foundation program should be adopted after treatment, and waterproof measures should be taken around the foundation pit. 2.2 Engineering geological conditions The geomorphic unit of the proposed site is a typical loess tableland geomorphology, which is generally high in the northwest and low in the southeast. The elevation of the station site is between 1545 m and 1551 m (1985 National Elevation Datum in China). The maximum exploration depth is 30.5 m, and no groundwater is found. The groundwater in the site belongs to pore phreatic water, and its main recharge source is atmospheric precipitation infiltration. According to the field investigation results, the groundwater depth is more than 100 m. The physical and mechanical properties of Plain fill, Malan loess, and Lishi loess are shown in Table 1. Table 1. Physical and mechanical properties of soil layer. Liquid moisture Gravity Saturation limit content/ density/ Void Sr/ wL / % (kN/m3 ) ratio % % Plain fill Malan loess ① Malan loess ② Lishi loess

Plastic internal limit Cohesion friction wP / c/ angle/ ◦ % kPa

Compressive modulus Es1−2 / Collapsibility MPa coefficient

5.17

13.00

1.06 13.43

26.28 18.97

7.00

22.00

6.00

0.113

11.03

14.50

1.06 28.09

26.92 19.27

9.53

25.90

14.62

0.022

14.13

15.10

0.96 40.49

27.28 19.45 10.04

25.78

24.66

0.010

10.74

15.20

0.86 32.40

26.79 19.23 11.21

26.17

27.79

0.006

3 TEST PROGRAM DESIGN AND CONSTRUCTION 3.1 Test design parameters The field test is divided into four test areas according to pile length and pile spacing, the pile spacing is divided into 0.8 m and 1.0 m, and the pile length is divided into 7.6 m, 9.6 m, and 12.1 m, which are arranged in an equilateral triangle. Plain soil is selected as the pile material. The design parameters are shown in Table 2. 193

Table 2. Design parameters of composite foundation.

Condition

Pile diameter (mm)

Pile length (m)

Pile spacing (mm)

Pile layout

Pile material

Replacement rate (%)

Condition 1 Condition 2 Condition 3 Condition 4

400 400 400 400

7.6 9.6 12.1 9.6

1000 1000 1000 800

Equilateral triangle Equilateral triangle Equilateral triangle Equilateral triangle

Plain soil Plain soil Plain soil Plain soil

14.51 14.51 14.51 14.51

3.2 Test methods To test whether the bearing capacity of plain soil compaction pile composite foundation meets the design requirements and discuss the working behavior of composite foundation, the static load test of single pile composite foundation is carried out. In this single pile composite plate load test, a circular rigid bearing plate is adopted, and the bearing plate with 800 mm pile spacing has an area of 0.55 m2 and a diameter of 0.84 m. The bearing plate with 1000 mm pile spacing has an area of 0.865 m2 and a diameter of 1.05 m. The loading method adopts a slow maintenance load method, and the design limit load is 360 kPa. The loading is divided into 10 levels, and the first level is 1/5 of the maximum load. Before and after each load, the subsidence of the pressure plate shall be measured and recorded once, and every 0.5 h after that, the subsidence of the pressure plate shall be measured and recorded once. When the subsidence is less than 0.1 mm per 1h within 2 h, it is considered that the subsidence of the pressure plate has become stable, the next load can be added, and the interval time of each load is not less than 2 hours. 4 NUMERICAL SIMULATIONS The finite element software Abaqus is used to establish a three-dimensional numerical model to analyze the settlement of a single pile composite foundation with a plain soil compaction pile under load and compare it with the test. Solid elements (C3D8R) are adopted for pile foundation, soil and bearing plate, face-to-face contact is adopted for pile-soil contact, and Coulomb contact criterion is adopted for contact criterion (Liu 2009, He 2010). Normal constraint (x=0, y=0) is adopted at the side of the soil, and fixed constraint (x=0, y=0, z=0) is adopted at the bottom of soil. The area of foundation reinforcement is regarded as a composite foundation, and Mohr-Coulomb constitutive model is adopted for composite foundation and soil. When the pile spacing is 800 mm and 1000 mm, the elastic modulus of the composite foundation is 47.4 MPa and 57.2 MPa respectively. The other soil parameters are shown in Table 1. The bearing plate material is steel, and the elastic modulus is 210 GPa. The length and width of the numerical model are all 12 m and the depth is 30 m, so the influence of boundary conditions can be ignored. The test results of condition 1 in Table 3 are selected to verify the accuracy of the numerical model. The numerical simulation results are shown in Figure 2. It can be seen that the numerical model has good accuracy and reliability. The composite foundation modulus method is adopted, and the numerical model can better simulate the settlement of plain soil compaction pile under external load. 5 FOUNDATION TREATMENT EFFECT 5.1 Load test and numerical simulation results of composite foundation To study the influence of pile spacing and pile length on the bearing capacity of pile foundation, the simulated conditions are shown based on the numerical model in Table 3. Figures 3 (a) and (b) show the load-displacement numerical simulation results of conditions 4 and 6. 194

Figure 1.

Numerical model.

Figure 2. Verification and comparison of numerical simulation and test results. Table 3. Settlement displacement of load test.

Condition

Pile length (m)

Pile spacing (mm)

180 kPa sedimentation (mm)

360 kPa sedimentation (mm)

Remarks

Condition 1 Condition 2 Condition 3 Condition 4 Condition 5 Condition 6

7.60 9.60 12.10 7.60 9.60 12.10

1000 1000 1000 800 800 800

4.23 3.30 3.17 3.91 2.94 2.88

9.67 9.36 9.19 9.44 9.10 8.99

Tests and numerical Test Test Numerical value Test Numerical value

When the pile spacing is the same, the longer the pile length, the longer the soil reinforcement area, and the smaller the displacement and settlement. When the pile spacing is 1000 mm, the pile length is increased from 7.6 m to 12.1 m, the load is 180 kPa, the displacement settlement is reduced by 25.1%, the load is 360 kPa, and the displacement settlement is reduced by 3.2%. When the pile spacing is 800 mm, the pile length is increased from 7.6 m to 12.1 m, the load is 180 kPa, the displacement and settlement decrease by 26.3%, and the load is 360 kPa, and the displacement and settlement decrease by 4.8%. 195

Figure 3.

Load-settlement displacement (P-S).

When the pile length is the same, the smaller the pile spacing, the higher the replacement rate, the denser the soil reinforcement, and the smaller the displacement and settlement (Yan 2014). When the pile length is 7.6 m and the load is 360 kPa, the settlement displacement of 800 mm pile spacing decreases by 2.38% compared with that of 1000 mm pile spacing. When the pile length is 9.6m and the load is 360 kPa, the settlement displacement of 800 mm pile spacing decreases by 2.77% compared with that of 1000 mm pile spacing. When the pile length is 12.1 m and the load is 360 kPa, the settlement displacement of 800 mm pile spacing is reduced by 4.77% compared with that of 1000 mm pile spacing. It can be seen that the reduction of pile spacing can effectively improve the bearing capacity of pile foundation, and the longer the pile length, the more obvious the effect of improving the bearing capacity of pile foundation. 5.2 Collapsibility of foundation soil According to the requirements of “Building Code in Collapsible Loess Area in China” (GB500252018), the average compaction coefficient of soil between three holes should not be less than 0.93, and the minimum compaction coefficient of soil of Class A and Class B buildings should not be less than 0.88. The minimum compaction coefficient of soil for Class C buildings should not be less than 0.84. The compaction coefficient of each condition in this test is shown in Table 4. No matter the compaction coefficient or the minimum compaction coefficient, all conditions meet the requirements. The collapsibility coefficient and self-weight collapsibility coefficient of indoor geotechnical test are shown in Table 5). The results show that the collapsibility coefficient and self-weight collapsibility coefficient of each condition are less than 0.015, and the collapsibility is eliminated within the treatment depth range. Table 4. Compaction coefficient of compaction pile.

Condition

Pile length (m)

Pile spacing (mm)

Minimum compaction coefficient

Average compaction coefficient

Condition 1 Condition 2 Condition 3 Condition 5

7.6 9.6 12.1 9.6

1000 1000 1000 800

0.80 0.82 0.83 0.84

0.87 0.90 0.90 0.91

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Table 5. Collapsibility coefficient and self-weight collapsibility coefficient of compaction pile.

Condition

Pile length (m)

Pile spacing (mm)

Collapsibility coefficient

Dead weight collapsibility coefficient

Condition 1 Condition 2 Condition 3 Condition 5

7.6 9.6 12.1 9.6

1000 1000 1000 800

0.002 0.012 0.006 0.006

0.001 0.008 0.006 0.003

6 CONCLUSIONS (1) The collapsible loess foundation is treated by drilling a plain soil compaction pile in the engineering site, which effectively eliminates the collapsibility of soil and improves the bearing capacity of the foundation. (2) When the pile spacing is the same, the longer the pile length, the longer the soil reinforcement area, and the smaller the displacement and settlement. When the pile length is the same, the smaller the pile spacing, the higher the replacement rate, the denser the soil reinforcement, and the smaller the displacement and settlement. The longer the pile length, the more obvious the effect of improving the bearing capacity of the pile foundation. (3) The collapsibility coefficient of the foundation and the self-weight collapsibility coefficient of each condition are combined with requirements, and the collapsibility of the foundation is eliminated. At the same time, both the compaction coefficient and the minimum compaction coefficient meet the design requirements.

ACKNOWLEDGMENTS This work was financially supported by the Qingyang Regional Cooperation Plan Project (KH2015-01).

REFERENCES He Yongqiang (2010). Theoretical analysis and experimental study on compaction pile composite foundation in strongly collapsible loess area. Lanzhou University of Technology, Lanzhou. Ji Jianhua (2015). Application of combined composite foundation in collapsible loess area. Henan Science, 33(1), 77–81. Li Ning, Han Xuan (1999). Numerical experimental study on strengthening mechanism of single pile composite foundation. Rock and Soil Mechanics, 20(4), 42–49. Liu Baomin, Yi Weixin, Sun Mingyuan (2007). Application of compacted cement-soil pile composite foundation in foundation treatment. Engineering Survey, 10, 21–23. Liu Zhiwei, Shen Rutao (2009). Experimental study on treatment of strong collapsible loess foundation with bored compaction pile [J]. Geotechnical Mechanics, S2: 339–343. Mu Shengli (2010). Engineering properties of Collpsible Loess and its foundation treatment. Journal of water resources and architectural engineering, 5, 70–72. Yan Mingli, Luo Pengfei, Tong Jianxing, et al. Area replacement rate of composite foundation [J]. Engineering Survey, 2014 (9): 30–35. Zhao Haifei (2014). Application of drilling soil compaction pile to sandy collapsible loess. Electric power survey and design, 5, 16–19.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Application and management of green energy-saving in building construction Ruochen Zhao, Huichun Qiao, Zhifei Liu, Jian Sun & Fangfang Liu Inner Mongolia Honder College of Arts and Sciences, Hohhot, China

ABSTRACT: China is facing an increasing energy crisis and environmental pressure. To fundamentally improve people’s quality of life, the country has put forward the strategic requirement of sustainable development and paid more attention to the construction of ecological civilization. In response to the call of the United Nations, it has put forward the slogan of “Zero Carbon China in 2050”, and the concepts of “green environmental protection” and “low carbon” have been thoroughly implemented in the construction of all walks of life. In the process of building engineering construction, more and more green construction technologies are applied to engineering construction, which can not only effectively reduce energy consumption, but also effectively improve the quality of engineering construction. Especially in green building engineering, the increasingly extensive application of energy-saving technologies is in line with the requirements of ecological civilization construction, which is of great significance to green development and ecological civilization construction. This paper introduces the importance of the application of green energysaving and environmental protection technology and discusses and analyzes the specific application and management of green energy-saving in building engineering construction, hoping to promote the sustainable development of the building industry. 1 INTRODUCTION Due to the rapid development of the national economy, people’s demand for material life has become increasingly rich, and the construction industry has entered a vigorous development stage. Although it has further stimulated the economic development in China, it has also brought about greater pollution problems and energy consumption problems (Ma 2022; Zheng 2021). With the improvement of national attention to ecological civilization construction, all high energy-consuming fields need to increase the development and utilization of energy-saving technologies. Therefore, green building projects must strengthen the promotion and use of energy-saving technologies, improve construction standards, respond to the national call for low-carbon concepts and energy-saving technologies, and promote better and more sustainable development in the construction field (Liao 2021). The construction industry is one of the pillar industries, and its rapid development has greatly improved people’s lives. Since the reform and opening up, the construction industry has developed faster and faster, and landmark buildings have emerged one after another. With the accelerating speed of urbanization, the construction industry has changed from extensive development to high-quality development. It has become a key problem to be solved in the whole construction industry on how to improve the construction level and meet the requirements of energy conservation and environmental protection in the construction process (Qu 2021; Yang 2021). 2 CONCEPTS OF GREEN ENERGY-SAVING BUILDING There are great differences between traditional building engineering and green building engineering. Traditional engineering projects mainly consider meeting people’s needs and maximizing the economic benefits of construction enterprises, while green buildings pay more attention to the harmonious coexistence between man and nature. That is to say, the main goal of green building is 198

DOI 10.1201/9781003318569-30

not only to meet the needs of people’s real life, but also to consider the economic and ecological benefits brought by the long-term use of construction projects, to shorten the gap between the construction industry and ecological development as much as possible and reduce the damage to the surrounding environment. Based on saving resources, people, architecture, and the environment are integrated into an organic whole to improve the overall quality of architecture. Green buildings need strict design schemes, high-standard energy-saving construction technologies, and high-standard building materials to provide efficient and healthy living spaces and achieve harmonious coexistence between man and nature. In green building, the use of energy-saving technology is an important foundation. It is of great significance for saving construction energy, reducing construction waste, reducing construction costs, and reducing noise pollution, which is beneficial to improving the social and economic benefits of enterprises and promoting the construction industry at the same time. The main characteristics of green energy-saving buildings include the following points: First, it has a good energy-saving environment. Second, it can effectively reduce the construction cost of the project, effectively improve the ecological benefits of the project construction, and ensure the living experience of residents. It can make full use of natural effects, reduce the utilization rate of various materials and electrical equipment, and ensure people’s lives and health. China advocates building a socialist harmonious society in the process of development. To ensure the smooth realization of this goal, it is necessary to use green energy-saving materials instead of traditional building materials. If it still follows the extensive development mode in the past, it would increase the pressure on the ecological environment. 3 SIGNIFICANCE OF THE APPLICATION OF GREEN ENERGY-SAVING AND ENVIRONMENTAL PROTECTION TECHNOLOGY

Figure 1. Application significance.

In the development process of the construction industry, we must pay attention to the application of green energy-saving, take effective treatment measures, minimize the pollution to the surrounding environment, and promote the double harvest of ecological and economic benefits of the construction industry. The specific application significance is shown in Figure 1. 3.1 Enhance building effectiveness Choosing green energy-saving materials in the construction process of buildings contains very high scientific and technological content, especially modern construction materials, dependency, and integrity, which have been effectively improved and solved the problems faced in the past construction process. The use of green energy-saving materials can further optimize the construction 199

process, shorten the construction period and fundamentally improve the construction efficiency of building projects while ensuring the construction quality. 3.2 Saving building materials In the development of the construction industry in the future, the previous construction methods will be changed, and the application of energy-saving and environmental protection technology will become an inevitable trend. In the process of building engineering construction, choosing green energy-saving to reduce the consumption of construction materials has become the focus of attention. When choosing construction materials, we should choose renewable materials, which can not only effectively save the construction cost, but also effectively improve the economic benefits of project construction and create more favorable conditions for environmental protection. 3.3 Consistent with the strategy for sustainable development In the process of modern city construction, the complexity of project construction is also increasing rapidly, and the energy consumption in the construction process is also increasing. However, the energy shortage is becoming more and more serious, so it is impossible to over-exploit, and the consumption of renewable energy has seriously affected the ecological environment protection. Compared with developed countries, sustainable development has always been an important problem that people need to face. In the past few years, although China’s economic development has been getting faster and faster, and all aspects are constantly improving, the energy consumed in the development process of many industries is non-renewable resources, which is contrary to the sustainable development strategy. In the development process of the construction industry, we should strictly follow the concept of green energy conservation and environmental protection, and increase the application of energy-saving technologies, to lay a good foundation for the future development of the construction industry. 3.4 Create a more comfortable living environment With the rapid growth of the economic level, the environmental pollution problem is becoming more and more serious. Facing such a severe environmental situation, people all over the world have increased their awareness of energy conservation and environmental protection and paid more attention to the protection of the quality of life and the ecological environment. In the construction process, we should also increase the application of green energy-saving and green construction materials, effectively improve the energy-saving and environmental protection effects of construction projects, and provide a safer and more comfortable living environment for people’s normal life. 4 APPLICATION OF GREEN ENERGY-SAVING IN CONSTRUCTION ENGINEERING 4.1 Construction of doors, windows, and exterior walls For the sake of ensuring the energy-saving effect of construction projects, it is necessary to put the wall insulation technology into practice first. In the actual construction process, we can start from the following two aspects: Firstly, in the process of pouring the wall between windows, pozzolanic concrete with low hydration heat reaction should be selected as far as possible. In the construction process of building engineering, hollow brick structure or pozzolanic concrete block can be selected as the construction material of envelope structure, which can effectively improve the construction effect of building engineering, ensure the construction quality of engineering project to meet the construction requirements, and give full play to the role of heat preservation. Secondly, a glass curtain wall can be chosen. We must choose materials with good safety factors and environmental protection performance to achieve the purpose of energy-saving and environmental 200

protection according to the characteristics of engineering project construction, further beautify the appearance of the building structure, reduce energy consumption, and truly realize energy saving and environmental protection purpose. In the construction process of building engineering, doors and windows are the most important vents of the whole structure. If their thermal insulation performance is poor, it will easily lead to the phenomenon of hot summer and cold winter in buildings, so it is necessary to increase the use time and frequency of refrigeration and heating equipment and consume a lot of energy. Therefore, before installing doors and windows, we must carefully check whether the thermal insulation performance of doors and windows can meet the relevant standards. Most external windows choose double-layer vacuum glass to increase their thermal insulation effect. Doublelayer glass can effectively improve the intimacy of door and window structure and reduce the heat exchange speed indoors and outdoors. After completing the installation of the door and window structure, it is necessary to seal the installation parts. When sealing, the filling materials with good sealing performance and robustness should be selected as far as possible to ensure the sealing performance of the door and window structure. 4.2 Energy saving of roofing and lighting equipment The roof is the key position of green energy-saving applications in building engineering. Roof energy-saving mainly faces high-temperature weather. If strong sunlight shines on the roof, a large amount of heat will gather on the roof and transmit to the room at the fastest speed, resulting in the continuous rise of indoor temperature. In the cold season, due to the great difference in temperature inside and outside the building, the temperature will be too high. To ensure the tightness between the wall and the door and window frame, the doors and windows can be sealed with sealant strips or other forms. After treatment, relevant technicians should be organized to go to the site for a sealing test for the first time, to improve the overall sealing performance of the building structure and reduce energy consumption. In the process of building construction, choosing green energy-saving is to maximize the use of energy, ensure that indoor greenhouse gases can be discharged out as soon as possible while ensuring sufficient sunshine, and ensure that the internal temperature meets the requirements of energy conservation and emission reduction. According to the relevant research, the energy consumption of the lighting system in the whole construction project occupies about 1/3 of the total energy consumption, which means that it is of great significance to do a good job in energy-saving measures of the lighting system. To ensure the energy-saving effect of the lighting system, we should increase the utilization rate of natural light as much as possible and reduce energy consumption. Because the shape of buildings is the arc, we can make full use of the role of natural light. According to the investigation and research, using this method can effectively reduce energy consumption in the lighting process. In practice, the following measures can be taken in the application process: Firstly, all lighting equipment in all buildings should choose energy-saving materials, especially in corridors, garages, public toilets, and other areas, and try to choose clean energy as the driving force. Secondly, photovoltaic power generation systems can be installed above buildings during construction, so that power can be supplied to narrow or dim areas. Finally, choosing intelligent lighting equipment can make full use of intelligent methods such as induction, voice control, and light control to ensure the energy-saving effect of the lighting system and save power resources to the minimum. 4.3 Water cycle technology and solar energy environmental protection technology Water is the most important resource on which people depend for their survival, and the shortage of water resources has become a hot topic of common concern in the world, occupying a very important position in environmental protection. It is also very critical to recycle water resources in construction projects. In the construction process, all pipes and pipes should meet the requirements of energy-saving and emission reduction in strict accordance with national standards. In addition, in the construction of building projects, a perfect rainwater recovery system should be set up to 201

improve the utilization rate of rainwater resources, make full use of recycling equipment, and treat all rainwater centrally, to truly realize the recycling of water resources after passing through the filtration system. The utilization of solar energy resources for the ecological environment is the least damaging, so in the construction process, workers also need to increase the utilization rate of solar energy resources. Many construction enterprises have used solar energy technology in electricity consumption and office work, which can effectively reduce electricity and energy consumption and help enterprises save more costs. However, due to the lack of technology, the application of solar energy technology is not in place. If not timely treatment, it will affect the construction effect and hinder the future development of energy-saving buildings in the practical application process. Among all the clean energy sources, solar energy has the highest utilization value among the known energy sources and has been widely used in some areas of China. Especially with the strong support of national policies, more and more users have begun to favor solar energy resources.

5 APPLICATION AND MANAGEMENT OF ENERGY-SAVING TECHNOLOGY 5.1 Deepen the concept of energy saving If we want to promote the wide application of energy-saving technology, we must fundamentally solve the application of energy-saving technology, that is, strengthen the publicity of green environmental protection and energy-saving concept, and deepen the application concept of energy-saving technology. Ensure that during the construction of green buildings, the application of energy-saving technologies can run through the whole construction period, and continuously deepen the environmental awareness of designers, managers, and construction personnel. First of all, the original architectural design drawings should fully reflect the concept of energy conservation, and ensure that all energy-saving technologies are feasible and correct. Secondly, during the construction period, it is necessary to constantly emphasize the awareness of green energy conservation to managers and construction personnel, reduce environmental pollution and energy consumption, and promote the harmonious coexistence between man and nature. In addition, government departments should also cooperate with construction enterprises, actively cooperate, jointly formulate many preferential policies for energy-saving technologies, and vigorously advocate to stimulate the application and promotion of energy-saving technologies. The specific content of the energy-saving concept is shown in Figure 2.

Figure 2.

Energy-saving concept.

202

5.2 Pay attention to the selection and management of construction materials To implement green energy-saving construction technology, we should not only pay attention to the improvement and development of technology, and pay attention to the selection of materials, such as curtain wall energy-saving technology and building top green energy-saving construction technology, which have relatively high requirements for construction materials. Therefore, construction enterprises should strictly control the selection of materials and do a good job in the management and arrangement of construction materials. In particular, many energy-saving technologies are used in special materials, which need special classification management to avoid loss of material properties due to improper management. 6 CONCLUSION With the continuous development of society, green energy conservation and environmental protection have become a widespread concern of the people. During the development of the construction industry, increasing the application of the concept of green environmental protection has become an important direction for the future development of the whole industry. In the actual construction process, we should organically combine the traditional technical means with the concept of energy conservation and environmental protection, meet the requirements of energy conservation and emission reduction on the premise of improving the construction quality, promote the sustainable development of the construction industry, and further improve the resource-saving and environment-friendly society. Based on responding to the call of the state, construction enterprises should constantly push themselves, strengthen the innovation and research and development of energy-saving construction technology, promote the concept of energy conservation and environmental protection to be deeply rooted in the hearts of the people, provide people with a more comfortable and safe green living environment, and gradually realize the harmonious coexistence between man and nature. ACKNOWLEDGMENTS This study is supported by Inner Mongolia Hongder College of Arts and Sciences. REFERENCES Liao, F.Z. (2021) Research on building energy-saving technology and management. Jiangxi building materials, (11):273–274. Ma, H. (2022) Effective application of energy-saving design in civil building design. Sichuan cement, (01):125– 126. Qu, X.J., Liu, W.Y. (2021) Research on the application of green energy-saving technology in building engineering construction. Residential facilities in China, (12):121–122. Yang, X. (2021) Discussion on energy-saving construction technology of housing construction engineering. Mass standardization, (24):37–39. Zheng, W.N. (2021) Design and research of intelligent control system for building energy-saving operation. Electronic world, (23):53–54.

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Advances in Petrochemical Engineering and Green Development – Guan (Ed.) © 2023 The Author(s), ISBN 978-1-032-33172-0

Pollution characteristics and human risks of heavy metals in agricultural areas from the gold mine in Hainan Province, China Hui-Wen Xie College of Earth and Mineral Sciences, Pennsylvania State University, PA, USA

ABSTRACT: Due to the properties of accumulation, non-degradability, and transportation, the heavy metal pollution issue has been focused on for several decades. The majority source of HMs contamination is a mining operation. In the present study, an abandoned mine located in Hainan Province, China, has been chosen to investigate the adverse impact of the mining operation. There were 39 soil samples and seven groundwater samples from a total of 36 sampling sites. Ni, Cr, Zn, Cd, As, Cu, Pb, and Hg were detected, while the concentration of Zn and Ni from groundwater exceeded the limit of 3 levels. The Single Pollution Index (SPI), Geoaccumulation Index (GI), and Nemerow Composite Pollution Index (NCPI) were applied to examine the level of HMs contamination. All results of SPI and NCPI were under the safety level. The mean SPIs followed the descending order by Pb (0.18), Cu (0.10), As (0.09), Zn (0.09), Ni (0.06), Cr (0.02), Hg (0.0018). The Geoaccumulation Index provides that Cr and Hg are mainly extremely exceeded; Cu, Pb, Ni, and Zn are mainly moderately and strongly exceeded, as is mainly safety and slightly exceeded. The results of the ecological risk analysis were all less than 40, which means no potential ecological risks. The hazard quotient (HQ) indicates the potential non-carcinogenic risk for a certain HM. All values of HQ were significantly less than the limit of 1, which means stay a safety level. The carcinogenic risk of As by oral was greater than 1.00E-06, which means oral ingestion of As might have carcinogenic risks.

1 INTRODUCTION Heavy metals (HMs) originally existed on the Earth. They have been carried near the surface due to crustal movements. However, urbanization, industrialization, and mining activities have undoubtedly influenced the concentration of HMs in the soil (Kinuthia et al. 2020). In addition, HMs are commonly found in soils after mining and smelting. Pollution of HMs will threaten the ecosystem and human health when they enter the food chain. The migration of HMs between soil and water is vital. The HMs from contaminated soil could cause the plant to be toxic, and further enter the human body. The high toxicity, bioaccumulation, and biomagnification of HMs will pose adverse effects to corps and animals (Alia et al. 2015, Cervantes-Ramírez et al. 2018). For those reasons, heavy metal pollution should be considered a primary concern in mine-dense nations. China is a representative example of a mine-dense nation. Coal consumption occupied almost 70% of national energy consumption. The overwhelming part of mine brings many serious environmental issues (Leong et al. 2020). Going back a few decades, China experienced an era of urgent economic development. During that period, many natural resources were over-exploited. Due to management limitations, in addition to the government-owned formal mining operations, there are many private non-conforming mining areas (Leong et al. 2020). These private mining operations have a more adverse impact on the environment matrices such as soil, surface runoff, and groundwater. Unscientific and blindly demanding mining methods led to irreversible damage to these natural resources. That damage has been lasting for a long time. Nowadays, we know that there is a challenging balance between natural 204

DOI 10.1201/9781003318569-31

resources and economic development (Almeida et al. 2017). This challenging balance has been ignored in the pursuit of economic development. "The Environmental Kuznets Curve hypothesis suggests that the relationship between economic growth and environmental impacts is not linear; it is more likely to behave as an inverted U-shaped curve (Almeida et al. 2017). It does not mean that once the adverse impacts reach the peak, the environment will repair itself to the original. Strict restorations are extremely necessary nowadays. With the deepening of industrialization, China’s industrial transformation has accelerated, and many industrial operations have moved or ceased operations. These mining operations have left behind many contaminated sites in the local area. These abandoned mine sites without contaminants removal will lead to diverse types of damage to the surrounding environment: large-scale collapse, settlement, and pollution. Abandoned mines affect soil, even humans. Mine experts research how mining affects the stability of the surface, while others study how mining affects the environment. A new environmental risk is associated with abandoned mines. To protect public health and reduce impacts, some countries prepare closure plans and long-term risk assessments when closing mines’ environmental damage to surrounding areas (Longoni et al. 2016). Due to the continued expansion of urban centers, land use becomes more constrained (Bren d’Amour et al. 2016). It is still possible to utilize abandoned mine sites as construction land. Because of the lack of management, most abandoned mines underwent migrations of HMs to surrounding areas. The migration of HMs results in serious effects, such as soil texture destruction, lack of nutrients in the soil, contaminated groundwater, and other environmental issues. Those issues might have a lasting impact on human beings. Crops from soil and water are fundamental living requirements. HMs and other toxic substances will build a line reaction with the human body. These toxic elements might cause acute and chronic injuries and pose health risk issues (Bren d’Amour et al. 2016). Therefore, before we take advantage of those tailing ponds, detailed risk assessments are needed. That is the reason we assess this Lead-zinc tailing pond in Hainan. Hainan is a province of China that has vast and diverse natural resources. Hainan Province has more than 90 kinds of mineral resources. The mineral resources are mainly iron, copper, cobalt, lead, zinc, gold, limestone, dissolved stone, quartz sand, and granite. It is the place where the soil and water samples came from. The sample tailing pond ran between 1958 and 1991. After the mine was closed, the mine was in ruins. A large amount of slag polluted by HMs is stored in the tailings pond. After long-term rainwater leaching, surface runoff, and heavy metal infiltration, many heavy metal elements are accumulated in the soil of the mining area and surrounding areas, resulting in soil heavy metal pollution. Those toxic exposures threaten human health and earth health throughout. Due to the physical properties of heavy metal migration, the HMs will flow to farther soil and underground, then cause more serious and far-reaching impacts. In this risk assessment, we aim to evaluate the contaminant level of the tailings pond and the impact on the sensitive targets around this Lead-zinc tailing pond. There are several types of sensitive targets. There are three sensitive targets around the sample tailing pond. After risk assessment, there are more complicated issues that need to be addressed. The selected pond should fully promote the treatment and repair of destroyed mines. 2 METHODS AND MATERIALS 2.1 Study area The investigated abandoned site is in the western Hainan Province, with a total area of 1,569 km2 (about half the area of Yosemite National Park) in the county. It is a heavy industrial base in Hainan Province. The topography of the tailing pond area is a denuded terrace unit, the relative height difference of the terrain is not large, and the surrounding vegetation cover is good. The terrain is high in the northeast and low in the south, the tailing pond hub is built in the mountain depression trench, the original trench is non-perennial flowing water, belongs to the valley type tailing pond, the elevation of both sides of the ridge is more than 100 m. There are communities, farmlands, and rivers around this tailing. 205

2.2 Sample collection According to the satellite map, site information, and the results of the site survey on March 1, 2017, the sensitive targets around the selected tailing pond were identified as: (1) the residents of the 14th team of a Farm about 1km to the north; (2) the basic farmland around the tailing pond; and (3) the downstream river. The sampling point layout method used the grid layout method by about 200×200 m. There were 26 sampling points in place near the reservoir and dams. In addition, one sampling point was placed on the north side of the tailing reservoir, and three were placed on the east side. There were six sampling points on the west side. A total of 36 soil sampling points were collected from this tailing. From these 36 soil sampling points, there were 39 soil samples and seven sets of groundwater samples collected to examine the pH and concentration of 8 types of HMs. In addition, three samples of tailings slag were taken to analyze the leaching toxicity and speciation of arsenic and lead. The code of samples is followed by MW1-0.4, a sample from site MW1 with a depth of 0.4 m. 2.3 Measurement of HMs in soils and groundwater The analytical method for detecting the content of HMs except for mercury in the soil is US EPA 6010C (Rev 3):2007. For detecting mercury in soil samples, US EPA 7470A (Rev 1):1994 is used. The analytical method for detecting the content of HMs except mercury is in water samples US EPA 6020A-2007. For detecting mercury in water samples, US EPA 7470A-2007 is used. For examining pH in the soil sample and water sample, NY/T 1377-2007 and GB/T 6920-1986 are used, respectively. 2.4 Leaching toxicity and chemical forms of HMs The analytic methods of testing leaching toxicity and chemical forms of HMs are GB5085.3-2007 and GB/T25282-2010//USEPA 6010C (Rev 3):2007, respectively. 2.5 Pollution assessments Using a single pollution index to examine the HMs pollution by equation (1); Using Geoaccumulation Index to test the level of contamination with the background level of local HMs by equation (2); Using the Nemerow Composite Pollution Index to evaluate the comprehensive pollution index considering the extreme value or prominent maximum, all details shown as Table S1. 2.6 Ecological risk assessment The potential ecological risk index method proposed by Hakanson is used to evaluate the potential risk of HMs in this area. This method not only evaluates the pollution status of HMs by using the principle of sedimentology, but also combines the ecological effects, environmental effects, and biological toxicology of HMs, reflecting the comprehensive effects of plenty of pollutants in the environment. It is the most widely used assessment in such research, and its equations are shown in Table S2. 2.7 Health risk assessment A human health risk assessment is a method to estimate the probability of adverse health effects in humans who may be exposed to contaminated environments, now or in the future. The risk assessment process is divided into four steps: Hazard identification, Dose-response assessment, Exposure Assessment, and Risk characterization. There are four routes of exposure: Inhalation, Ingestion, Dermal, and Inoculation. The detailed calculations of carcinogenic and non-carcinogenic exposure doses by different routes. It is a process to estimate the number of excess unwarranted health events expected at different time intervals at each level of exposure. All detailed equations are shown in Tables S3 & S4. 206

2.8 Data analysis Microsoft Excel 2018 was used for the statistical analysis of obtained data, and RStudio was applied to draw the diagrams in this study. 3 RESULTS 3.1 pH in soil and groundwater The pH of soil samples is between 4.11 and 7.21 (Table S1). The mean soil pH is 5.33, which is weakly acidic. The existence of acid buffers the transport of HMs in soil (Schwab et al. 2008). The pH of groundwater is 6.44. Except that S40-0.4 and S27-0.4 (comparative set) are alkaline, other samples are weakly acidic. A total of 7 groundwater samples were collected for determination. The pH range of tested samples is between 6.24 and 6.78. The groundwater is slightly acidic and might be affected by contaminated soil. The detailed information on the pH values in soil and groundwater is shown in Table 1. Table 1. HMs results of soil samples (mg/kg).

Min Max Mean STDEV GB15168-2018 (5.5