Innovative Renewable Waste Conversion Technologies 3030814300, 9783030814304

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Gheorghe Lazaroiu Lucian Mihaescu   Editors

Innovative Renewable Waste Conversion Technologies

Innovative Renewable Waste Conversion Technologies

Gheorghe Lazaroiu Lucian Mihaescu •

Editors

Innovative Renewable Waste Conversion Technologies

123

Editors Gheorghe Lazaroiu University Politehnica of Bucharest Bucharest, Romania

Lucian Mihaescu University Politehnica of Bucharest Bucharest, Romania

ISBN 978-3-030-81430-4 ISBN 978-3-030-81431-1 https://doi.org/10.1007/978-3-030-81431-1

(eBook)

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface I

Let us start at the beginning, the big bang as it is known. It is not known from where, but according to our current perception, as per our hypothesis, a four-dimensional space is formed, respectively: matter, energy, information, and time. Why can we assert thus? Let us think about trivial and current facts. We can argue using any plant, but we take the example of the cherry tree. It starts blooming in spring before having leaves to feed on matter and energy. It practically uses its energy reserves according to the information and develops the flowers, so the first law of any species seems to be the perpetuation of the species. Then, they form leaves that absorb energy (solar radiation) and matter (carbon dioxide, water, minerals, etc.) to regulate their structures according to the information held. Time is an important element that seems to be related to information and vice versa. A cherry tree in the southern hemisphere will never bloom in the northern hemisphere in the spring. The energy–matter dualism has long been explained and is based on Einstein’s famous equation, E = mc2. This actually means transforming a four-dimensional space into a three-dimensional space. Without having a similar explanation, we can consider that time and information can be transformed into energy or matter and then we arrive at the philosophical concept of black holes or big bang, a space contracted at one point, or one-dimensional. What is information? Information seems to be composed of all the laws and postulates of physics, chemistry, optics, nuclear, etc. What is time? Time is implacable and is present implicitly or explicitly in information, in the DNA of each individual and inexplicable in the evolution of the earth and the universe. What is matter? The philosophical concept of matter is associated with mass, with something palpable, and this mass also has an energy content. The concept of mass seems to be essential in defining matter. What is energy? The current classical concept is that energy is a measure of the motion of matter, but if we refer to Einstein’s definition energy is a measure of mass transformation, because in the equation E = mc2, m is the difference in mass that v

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occurs in a transformation. If we correlate with what we currently know about universe, the mass does not disappear but remains at the level of protons, or more of elementary particles. As is known, an elementary particle, or fundamental particle, is a particle that is not known if it has a substructure; this means that it is not known whether it is made up of smaller particles. If an elementary particle really has no substructure, then it is one of the basic units of the universe, from which all other particles are made. In the standard model, elementary particles are fundamental fermions (including quarks, leptons, and their antiparticles) and fundamental bosons (including intermediate bosons and the Higgs boson). The current model of knowing does not explain everything that happens in the universe, more specifically on earth. At the current level of knowledge, we can say with certainty that the universe is an isolated system and so that mass and energy are conserved. But the earth? The earth, according to current knowledge, is considered to be a closed system that has only energy exchange with the outside, so the universe. What can we say from here? If we consider the earth perennial, the energy accumulated in time is in the form of fossil fuels of the order of 1023 J and in the form of nuclear fuels of 1024 J from fission and 1024 J from fusion. The energy received from the sun on earth is 5.4 * 1024 J/year, and—the amount of solar energy that reaches the earth on the unit of surface directly exposed to sunlight: 1370 W/m2. To this is added the heat flow from inside the earth to the surface: 9.5 * 1021 J/year. The average amount of energy required by man is (8–10) * 106 J per day. What is meant by waste? In a broad sense, any material residue resulting from any process is waste. As it is known, the result of dividing two polynomials comprises also an irreducible remainder. Obviously, not all operations lead to the rest, but the majority. Similarly, waste is material residue resulting from some process of transformation (division) of one product (division) into another product (divider), resulting in a certain amount of product (how much) and irreducible waste (residue). It is obvious that this residue can be, in some cases, a certain product through another recovery or recycling transformation, but in many cases it is irreducible and can therefore be considered waste. Therefore, a waste is a certain material residue that cannot be recovered in the product. This material residue always contains an amount of embedded energy. Disposal of this waste in the environment leads to increased volumes of landfills, with an impact on environmental health. Some of this waste can be used for energy production, achieving both an energy contribution in the overall energy balance, but also a considerable reduction in volume, with a direct impact on reducing the size of landfills and the impact on the environment. Maintaining a high standard of living, based on energy consumption, while increasing individual comfort by increasing the quality of the environment, leads to an increase in the technical and financial efforts to reduce waste pollution by using them as renewable energy sources.

Preface I

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Renewable energy present on earth today and questionable about the use of organic resources in the future involves a much more complex analysis and sustainable generalizations. In fact, renewable energy from waste must be integrated into the earth’s energy and the general concept of energy. Bucharest, Romania

Gheorghe Lazaroiu Lucian Mihaescu

Preface II

The work Innovative Renewable Waste Conversion Technologies presents the authors’ own research for the energy recovery of waste through various conversion technologies. Researchers from three countries and prestigious universities with great teaching and research experience in the field of energy recovery of renewable waste have contributed to the elaboration of the paper. Chapter 1 focuses mainly on the Romanian power system (in comparison with other European countries), as one with high RES contribution and fast ascending trend of RES-based generation capacities. The impact of modifying the power generation spectrum (starting with 2014) is evaluated. It is noticeable that the shares corresponding to hydro-energy and nuclear energy show an almost constant trend. Moreover, the correlation between the national amount of CO2 emissions and the events which have determined a decline in the RES share in the energy production is investigated. Consequently, it is observed that the contribution of polluting energy sources (such as coal, gas, and oil) progressively diminished. Chapter 2 addresses that the market success of a fuel depends on several factors, such as the energy quality expressed by calorific value, price/calorific value ratio, and polluting effect. A purely biological classification does not allow access to information on the energy use of biomass, which required the design of a biofuel matrix introduced in this chapter. Chapter 3 underlines that a biofuel derivative has a dominant characteristic, which must be considered in the energy production system. It is highlighted that a good use of biofuels in energy production applications comprises the intersection of two concepts, namely: an efficient combustion and a use of the resulting thermal potential in an energy installation with the highest efficiency. Chapter 4 tackles the problem of combustion for biofuels with low energy characteristics that remains open. The main solution is to approach the combustion of a certain number of biofuels, aiming to capitalize their positive characteristics. It is proved that the combustion of more than two fuels simultaneously usually represents an unnecessary complication.

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Chapter 5 refers to the awareness of the energy and environmental problems associated with the burning of fossil fuels, as well as the need to find other alternatives that meet the growing demand for energy in the world and have encouraged the research for new alternative fuels. The research aims at developing a capitalization method for animal fat waste from the leather industry, by analyzing a combustion technology of mixtures made up of this waste and liquid hydrocarbon. Chapter 6 deals with the energetic valorization of biodegradable wastes that has become during recent years one of the most preoccupations on modern society. Difficult manipulation of these wastes has led to an increased interest to use them in the purpose of energy production or to assure a proper disposal. Chapter 7 presents different aspects of the system for simultaneous production of electric and thermal energy (cogeneration) through biomass gasification. Various features of the processes of biomass preparation, syngas production, syngas cleaning, and combustion in the cogeneration set are presented and discussed. Chapter 8 addresses the conception, realization, and a set of tests for a pellet burner with a horizontal flame and a power of 150 kW. The burner is designed for the combustion of pelletized agricultural biomass. Chapter 9 presents an overview of the possibilities of efficient industrial waste incineration. For poultry manure combustion, the moisture content is an important issue to consider. Very wet fuels, with about 10–15% in a massive grain strain mixture, it is preferable to be processed using the burning technology with horizontal grate bars by direct advancing movement. Chapter 10 depicts the possibilities for utilization of waste heat from boilers and furnaces. Based on the specifics of the flue gases throughout the combustion process of biomass and phytomass, various installations for waste heat recovery (for heating air, water, and steam) are also presented. Chapter 11 investigates the influence of different alternative fuels used at internal combustion engine on pollutant emissions. It is proved that the use of hydrogen as single fuel at spark-ignition engine leads to the decrease of NOx with 93% at lean dosages. The addition of hydrogen at the air inlet of spark-ignition engines ensures better combustion performances and lower polluting emissions levels. Chapter 12 addresses the problem of lignocellulosic agricultural residues, which are in huge quantities, but a considerably underutilized resource of biomass is available for energy. Mobilization of this potential for energy gives an opportunity to provide a secure energy supply contributing to the decarbonization of the energy sector. Chapter 13 promotes the exploitation, use of deposits of natural absorbents (bentonites and zeolites), and the use of new energy resources, while saving classical resources. Environmental pollution with waste oils can be reduced if this hazardous waste is recovered by purifying and reusing it in the automotive and industrial fields. This technology of purification of waste oils requires organizational, scientific, and economic efforts for an evolution of this branch.

Preface II

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Chapter 14 shows the specifics of the environmental aspect related to the introduction of cogeneration plants through biomass gasification, as well as the significant possible risks in the introduction of such large-scale power plants. The significance of the risk is presented in matrix form, as well as the actions for its reduction are indicated. Chapter 15 shows the specifics in the environmental aspect of the introduction of cogeneration plants through biomass gasification, as well as the significant possible risks in the introduction of such large-scale power plants. The significance of the risk is presented in matrix form, as well as the actions for its reduction are indicated. Chapter 16 presents an innovative technology that responds the challenges encountered in the conversion of waste organics, providing the possibility to utilize fuels with a moisture content of up to 90%wt, while keeping the acceptable emission levels (NOx, CO, SO2, and HCl). The 12 MW operating pilot-scale plant tested while supplied with meat-and-bone meal has exhibited high efficiency, 88.4  84.8% depending on a facility load, offering a complete fuel combustion resulting in a flue gas being free from flammable gas compounds, and the ashes with low percentages of combustibles. The editors thank the contributors for the elaboration of the chapters in which they presented their own research, making important contributions to the energy recovery of waste. We also thank the publishing house and especially Mrs. Miriam Sturm— responsible editor. Bucharest, Romania

Gheorghe Lazaroiu Lucian Mihaescu

Contents

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Structure of the Energy Produced from Renewable Sources . . . . . Dana-Alexandra Ciupageanu, Gheorghe Lazaroiu, and Lucian Mihaescu

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The Matrix of Energy Biofuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gheorghe Lazaroiu, Lucian Mihaescu, Dana-Alexandra Ciupageanu, and Gabriel-Paul Negreanu

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The Technological Matrix for the Efficient Use of Biofuels . . . . . . . Gheorghe Lazaroiu, Lucian Mihaescu, Gabriel-Paul Negreanu, Ionel Pisa, and Viorel Berbece

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Combined Combustion Required for Energy Fuels . . . . . . . . . . . . Gabriel-Paul Negreanu, Gheorghe Lazaroiu, and Lucian Mihaescu

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Experimental Tests on the Combustion of Animal Fats . . . . . . . . . 103 Dana-Andreya Bondrea, Gheorghe Lazaroiu, Lucian Mihaescu, and Gabriel-Paul Negreanu

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Combustion of Biogas Obtained by Anaerobic Fermentation of Animal Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Gheorghe Lazaroiu, Lucian Mihaescu, and Elena-Mădălina Mavrodin

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Feasibility and Experimental Study of Cogeneration Plant Using Wood Biomass Gasification Process . . . . . . . . . . . . . . . . . . . . . . . . 179 Iliya Iliev and Angel Terziev

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Design and Experimental Testing of a Horizontal Flame Burner for Agricultural Waste Pellets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 Lucian Mihaescu, Emil Enache, Ionel Pisa, and Elena Pop

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Experimental Research of Combustion of Poultry Manure . . . . . . . 213 Gheorghe Lazaroiu, Lucian Mihaescu, Dana-Alexandra Ciupageanu, and Gabriel-Paul Negreanu

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10 Waste Heat Recovery from Boilers and Furnaces Running on Biomass Waste Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Iliya Iliev and Angel Terziev 11 Solutions for Polluting Emissions Reduction in Internal Combustion Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Alexandru Cernat, Constantin Pana, and Niculae Negurescu 12 Technologies for Energy Production from Lignocellulosic Agricultural Residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 Georgii Geletukha, Semen Drahniev, Tetiana Zheliezna, Vitalii Zubenko, and Olha Haidai 13 Purification of Waste Oils from the Transport Industry Through Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Ionel Pisa, Mihai Dragne, and Elena Pop 14 Environmental Impact and Risk Analysis of the Implementation of Cogeneration Power Plants Through Biomass Processing . . . . . 385 Iliya Iliev and Angel Terziev 15 Informatics Applications for Efficient Exploitation of Forestry Fund . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 Teodora Vatuiu, Gheorghe Lazaroiu, and Silviu-Adrian Iana 16 The Staged Combustion of Meat-and-Bone Meal: The Characteristics of Conversion Sub-processes and Large-Scale Process Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 Marcin Kantorek, Krzysztof Jesionek, Sylwia Polesek-Karczewska, Paweł Ziółkowski, and Janusz Badur Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

Editors and Contributors

About the Editors Full Professor Gheorghe Lazaroiu, Ph.D., has been granted Ph.D. thesis advisory in power engineering in 2011, having great academic and research experience. Born in 1954, he started his professional career as Engineer at the Institute of Nuclear Power Reactors in August 1979 and then continued as Technical Engineer between May 1985 and February 1988 at University Politehnica of Bucharest. Starting with 1988, he started his academic career as Assistant Professor within Power Engineering Faculty at University Politehnica of Bucharest. After March 1992, he became Lecturer, then Associate Professor from March 1999, and Full Professor from October 2005. During his career, he coordinated as Project Director more than 30 research contracts won through competition. For what concerns, the impact of his research, he has 232 scientific publications from which over 75 ISI indexed with high impact factor (14 articles in top 50% journals) and owns 3 patents (ID: orcid.org/0000-00033077-5192). He has an 12 h-index on Web of Science, 12 h-index on Scopus database, and 14 h-index on Google Scholar.

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Full Professor Lucian Mihaescu, Ph.D., was born in 1948 and obtained the title of mechanical engineer at the University Politehnica of Bucharest in 1971. He has been a doctor in mechanical engineering, with the specialization steam boilers, from 1980, with the doctoral thesis “contributions to the construction and operation of pulverized coal burners.” He was University Professor since 1996 and Chairman of the Department of Classic and Nuclear Thermomechanic Equipment between 1996 and 2012. He has headed the following courses: fuels and combustion plants, and heat generators. He has published over 10 specialty books: energy recovery of vegetable oils, vortex burners, low NOx hydrocarbon burners, unconventional thermal plants, steam generators. In regard to the subject of industrial and agricultural waste, the following achievements should be mentioned: collaboration with E Morarit Husi for agricultural waste energy recovery; research regarding the combustion of vegetable oils; research regarding the combustion of animal fats; and research in the field of pyrolysis and gasification of agricultural waste. He has published over 195 technical papers and took part in the development of over 100 research projects out of which more than 45 being scientific research. Also, he has participated in more than 130 national conferences and over 40 international conferences. He has over 200 citations on ISI with H = 9 and over 300 citations on Scopus with H = 8. He is also the holder of 4 patents.

Contributors Janusz Badur Institute of Fluid Flow Machinery, Polish Academy of Sciences, Gdańsk, Poland Viorel Berbece Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Dana-Andreya Bondrea Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania

Editors and Contributors

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Alexandru Cernat Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Dana-Alexandra Ciupageanu Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania Mihai Dragne Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Semen Drahniev Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Emil Enache Enache MORARIT, Huși, Vaslui, Romania Georgii Geletukha Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Olha Haidai Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Silviu-Adrian Iana Doctoral School of Economics II, ACADEMY of ECONOMIC STUDIES Bucharest, Bucharest, Romania Iliya Iliev Agrarian and Industrial Faculty, University of Ruse, Ruse, Bulgaria Krzysztof Jesionek Wrocław University of Science and Technology, Wałbrzych, Poland Marcin Kantorek Endress + Hauser, Wrocław, Poland Gheorghe Lazaroiu Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania Elena-Mădălina Mavrodin Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania Lucian Mihaescu Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Gabriel-Paul Negreanu Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Niculae Negurescu Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Constantin Pana Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Ionel Pisa Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Sylwia Polesek-Karczewska Institute of Fluid Flow Machinery, Polish Academy of Sciences, Gdańsk, Poland

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Elena Pop Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania Angel Terziev Faculty of Power Engineering and Power Machines, Technical University of Sofia, Sofia, Bulgaria Teodora Vatuiu Faculty of Law and Economic Sciences, TITU Maiorescu University of Bucharest, Bucharest, Romania Tetiana Zheliezna Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Paweł Ziółkowski Faculty of Mechanical Engineering and Ship Technology, Gdańsk University of Technology, Gdańsk, Poland Vitalii Zubenko Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine

Chapter 1

Structure of the Energy Produced from Renewable Sources Dana-Alexandra Ciupageanu, Gheorghe Lazaroiu, and Lucian Mihaescu

Abstract It is remarkable as renewable energy sources’ (RES) share in the power balance grew constantly during the past decade, following specific trends for different regions. Consequently, the contribution of polluting energy sources (such as coal, gas and oil) progressively diminished over time. In order to make environmental restrictions for the classical power plants still in operation, proper depolluting equipment are required. This chapter focuses mainly on the Romanian power system (in comparison with other European countries), as one with high RES contribution and fast ascending trend of RES-based generation capacities. First, the impact of modifying the power generation spectrum (starting with 2014) is evaluated. It is noticeable that the shares corresponding to hydro-energy and nuclear energy show an almost constant trend. Second, the correlation between the national amount of CO2 emissions and the events which have determined a decline in the RES share in the energy production is investigated. To highlight the different evolution at a national level, a comparison to other representative European countries (Germany—having a distribution by sources similar to Romania, France —relying mainly on nuclear energy and Czech Republic—showing a decreasing renewable energy employment trend) is presented. To underline the correlation between renewable energy employment and climate evolution, the fluctuations triggered in the annual use of hydro or wind sources are cross-referenced with meteorological data. A temperature increase between 4 and 22% is noticed in all the countries taken into account, while the precipitation level doesn’t follow a monotonic trend. Keywords CO2 emissions Renewable energy


Environmental impact
Power production


D.-A. Ciupageanu (&)
G. Lazaroiu Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania e-mail: [email protected] L. Mihaescu Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_1

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1 General Aspects According to the latest analyses carried out by energy agencies and governing institutions, sustainable development of renewable energy systems raises a two-folded challenge [1, 2]. The main paths in the energies policies sector emerge as follows. On one hand, electrification (based on renewable energy sources—RES) of energy intensive economy sectors, such as transportation, is identified as a solution to mitigate harmful emissions, therefore effective incentives must be carefully designed in this regard. On the other hand, including progressively higher shares of strongly variable energy sources (wind, photovoltaic, wave energy, etc.) entails dealing with supply continuity issues [3, 4]. To overcome RES intermittency issues when integrating them in various power systems architectures, through variability analyses, performant prediction models and connection solutions have to be investigated [2]. To assess the potential prospects for a particular renewable technology to reach a certain share in meeting the local/regional energy balance, the correlation between costs, carbon intensity, capacity increase factor and associated carbon dioxide emissions has to be evaluated [5]. In order to address energy systems sustainability over extended time frames considering the increasing RES penetration, it is mandatory to investigate each evolutionary pattern from complimentary perspectives, in order to design an up-to-date holistic framework to develop future microgrids [6]. Researches worldwide emphasize that a viable solution to prevail individual limitations of RES and increase systems’ global yield is by employing hybrid configurations, comprising energy storage devices coupled to RES plants [7, 8]. An overview of the concept and the major factors towards sustainable development of energy systems is depicted in Fig. 1. It is agreed that global energy consumption is highly susceptible to economic factors and terms of energy transition paradigm [9]. Figure 2 displays the behavior exhibited by the relative energy consumption ratio evaluated for two consecutive

Fig. 1 Sustainable energy systems concept

1 Structure of the Energy Produced from Renewable Sources

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Fig. 2 Relative energy consumption variation. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE

years according to [10]. It is noticeable that, given the rising energy consumption, this variable is positive and growing before 1950. Around 1950, the energy consumption shows a sudden increase, doubling its value, determining a peak of the variable in Fig. 2. Past this spike, an abrupt decrease is noticeable, after which comes a time interval followed by small amplitude oscillation (within a range of 0:1). Energy consumption variations are reflected on the primary energy consumption, as showed in Fig. 3. It is evaluated that, as presented also in [12], a yearly growth rate of approximately 2.5% corresponds to natural gas and coal, a rate under 1.5% is associated to oil. Regarding nuclear energy, before 1980 it showed a 10% annual growth rate, remaining always under 1% after that. RES show a low environmental impact, following the global policy of harmful emissions reduction [13]. Moreover, RES enable increased energy independence, as they reduce the dependence on energy imports and cope with the eventual risks related to markets fluctuations. Thus, RES became lately cost-competitive with classical power generation [14], showing an increasing trend in meeting the energy balance, as pictured in Fig. 4 for Romania, Europe and worldwide.

2 RES Potential Territorial Spreading and Variability Territorial and climatological features strongly influenced the development of Romania’s national energy system [15]. The dominant geographic and energy generation characteristics of Romania are addressed forward: • Romania is a medium sized country (relatively to the European scale), having a surface of around 240,000 km2 and a population of about 20 million people; • The relief distribution is depicted in Fig. 5. It is highlighted that a significant part of the Carpathian Mountains (the second largest European mountain chain

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Fig. 3 Primary energy consumption. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE [11]

Fig. 4 Renewable energy share in meeting energy demand. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE [11]

Fig. 5 Romanian relief distribution [16]

1 Structure of the Energy Produced from Renewable Sources

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Fig. 6 Territorial spreading of RES potential and population

after the Alps) is located on Romanian territory. Moreover, the river Danube follows a course of approximately 1,000 km over its territory up to finally shedding into the Black Sea. This analysis addresses first the correlation between RES territorial availability in Romania and population distribution, aiming to discuss possible feasible solutions for increasing RES share in Romanian energy balance. Based on potential estimations and statistical records [15, 17], the RES availability and population regional spread are overlapped for all 42 regions, including the capital. Figure 6 depicts the ratios corresponding to the two quantities, relatively to the minimum of each (12.1 MW RES potential in region 26 and 25.1 people per km2 in region 39). It is evident that the maximum values are not correlated (being evaluated at 2572.5 MW in region 15, respectively 7913.6 people per km2 in region 10, which represents the capital), posing transmission and infrastructure loading issues in centralized systems [18]. The results of further assessing the average value and the deviation across the country, are listed in Table 1, highlighting their both widespread and pointing out the need of passing to decentralized architectures. Beyond the territorial spread, it is remarked a wide distribution of individual sources contribution in reaching the regional RES potential, as shown in Fig. 7. Romania accounts for a global exploitable potential of 10,232.5 MW, including wind energy, photovoltaics, biomass, biogas, geothermal, and cogeneration resources. Given the technological advances in the field of RES, entailing their economic competitiveness to classical power plants, it is expected that RES share will keep growing during next few years. Figure 8 presents the evolution of the generating

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Table 1 National average and deviation

RES potential Population density

Average value Absolute

Relative

Deviation Absolute

Relative

245.8 MW 267.7 people per km2

20.3 10.7

242.7 364.1 people per km2

20.1 14.5

Fig. 7 Territorial variability of RES availability

capacities installed in RES technologies over the past decade in Romania. In accordance with the available potential depicted in Fig. 7, the largest capacity is installed in wind energy conversion systems. Although the rising trend is obvious, the latest total RES capacity (excluding large hydro, as in Fig. 7) adds up to 4547 MW, leaving a difference of 5776.5 MW unexploited RES.

3 Evolutionary Trend Analysis a. Carbon dioxide Emissions The correlation between the total primary energy supply per capita and the corresponding CO2 emissions quantity are depicted in Fig. 9, in comparison for Romania, Europe and at global level [10]. It can be remarked that Romania and Europe show similar trends and the variation ranges are close for both investigated quantities.

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Fig. 8 Operating generating RES capacities in Romania

Fig. 9 Total primary energy supply and CO2 emissions evolution. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE [11]

However, the CO2 emissions level in Romania is lower by up to 44% if compared to Europe. This is due to the higher RES share integrated in the Romanian energy balance and the reduced total primary energy supply (by up to 48%). Moreover, it is noticeable that during past decade, both CO2 emissions and total primary energy supply per capita are on a deceasing slope in Romania and in Europe, while they are growing at a global level. Figure 10 depicts the dependence between the RES share in the power generation structure in Romania and the evolution of corresponding CO2 emissions. It is remarked as the maximum RES share is achieved in 2014 while the minimum is reached in 2017. Complimentary, looking at the weather conditions for 2017, it can

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Fig. 10 RES share and specific CO2 emissions evolution [16]

be observed that the lower contribution of renewable energy is correlated with consistent droughts affecting the hydropower plants’ production. Furthermore, it is noticeable that during the analysis timeframe, RES share in power production reaches 41.28%. Consequently, the CO2 emissions over national level are diminished, as emerging from Fig. 10, falling within the range 287.11—299.02 g/kWh. b. Electricity Generation Spectrum According to official prospects, it is expected that the power production capacity in Romania will reach 21,460 MW in 2020, although ongoing evaluations may lead to the withdrawal of power producing licenses for up to 3800 MW. It should be specified that 1067 MW installed in thermal power plants (227 MW and 210 MW from the Chișcani power plant, 330 MW from the Rovinari power plant and the rest from Iernut power plant) are already taken out of service [19]. Figure 11 depicts the structure of the power generation section in Romania. The classical energy generation sources in Romania include [13, 20]: – oil and gas reserves (with potential deposits additionally exploitable in the Black Sea). Starting with the 1970s, the use of liquid and gas fuels for power production is constantly lowered. – coal – uranium. In the 1980s, the nuclear power plant of Cernavoda was built (comprising 2 groups of 750 MW each). It started operation in the 1990s. – a well-developed hydrographic network. The hydropower plants Portile de Fier I and II stand out in the hydro-energy category (being built starting with the 1960s to harness the Danube’s waters). A wide system of artificial lakes and hydropower plants on the majority of inner rivers bring also a significant contribution to the hydro-energy production.

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Fig. 11 Power generation structure in Romania [16]

In Romania, RES generating capacities account for [21, 22]: – wind farms (especially on the shoreline and agriculturally designated areas— large crops cultivated surfaces). Starting with 2009, a very well-developed wind power network was implemented, mainly in the Dobrogea region. – photovoltaic plants (on land with no agricultural assignment). – Romania owns rich biomass resources; its surface being covered with various types of forests. More in detail, there are 6.61 million hectares of forestry lands, representing 27.1% of the total surface. The distribution of the forests is almost uniform with the landforms (approx. 33% for each), having a slightly lower presence in the southeastern and southern regions. Regarding the yearly potential for wood biomass harvesting, it is remarked that, during the last decade it has varied between 18.5 and 20 millions m3 [23]. As around 5 millions households rely on wood-based heating, 3.6 millions m3 of the wood production are employed in thermal energy generation. Biomass derived from agriculture doesn’t represent yet a viable option for power production [24]. Figure 12 focuses on the distribution by sources of energy production, individually for conventional sources and RES. In reference to the RES-based generation, it is evidenced that hydro-energy represents the main source during this time, being almost 3 times higher than wind and 30 times larger compared to photovoltaic generation. However, it highlighted that the installed power in hydro power plants is 2 times larger than the one installed in wind generation systems [25]. For what concerns the participation of conventional energy sources, it is outlined as coal remains the dominant resource, although a slight decline in its use can be observed starting with 2015 (particularly from 26.89 to 24.24%). The following contribution belongs to nuclear energy, with an approximate share of 18%. Hydrocarbons are

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Fig. 12 Share distribution by source in Romania [16]

next, while other sources, such as biomass, show a very low share, reaching a maximum of 1.81% in 2018. The data presented previously outlines the tendency to reduce polluting energy resources, diminishing CO2 emissions issued by the power sector. It is pointed out that the CO2 specific emissions are relatively low, under 290 g/kWh (compared with the lowest CO2 emission from coal burning in Rovinari power plant, i.e. 940 g/kWh). iii. Heat Generation Spectrum For what concerns the heat generation sector, it is remarked in Fig. 13 as it mainly relies on natural gas. A smaller (and decreasing) share belongs to oil, while a variable contribution is brought by coal. In the RES area, biofuels and waste stand out, having the largest participation. However, in Romania the RES based heat generation is weakly represented, with very reduced waste shares. In the combined heat and power generation framework, this is analysis is of great interest, highlighting that, following certain energy shifts, the carbon footprint of the heat sector can be considerably reduced.

4 Discussions iv. Environmental Impact The correlation between energy resources employment and climate change represents an issue of great interest worldwide [26]. To meet the increasing demand, large amounts of harmful emissions (mainly CO2) are generated in the energy sector. These emissions have to be properly managed to achieve environmental impact mitigation. In the current global and European context, Romania shows a significant potential in this regard. Figure 14 depicts the evolutionary trends of CO2 emissions per capita. It is evident that Romania shows the fastest decreasing slope, followed by Europe. Globally, the emissions evolution exhibit a slight increase.

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Fig. 13 Heat generation by sources. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE [11]

The fluctuations triggered in the annual use of hydro-energy or wind sources are cross-referenced with meteorological data. During the analysis time span it is highlighted that:

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Fig. 14 CO2 emissions per capita. Reprinted, with permission, from Lazaroiu et al. (2020) © IEEE [11]

Fig. 15 Absolute temperature deviation from the yearly average [16]

• in reference to the wind intensity, local repartitions have the most important impact on the produced energy. Therefore, annual data could not be formulated. • the annual average temperature drift for the four analyzed countries is presented in Fig. 15. It is remarked that a minimum 4% temperature increase is registered in France and a maximum 22% for Czech Republic respectively. All the other variations fall within these limits. • regarding the precipitation drift, it is highlighted that there are significant differences when considering the quantity of precipitations at European Union level. This can be correlated with the variations observed in the hydropower use. Considering the share hydropower has in the national power production, Romania suffered the strongest impact.

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The increasing RES share in meeting the energy demand reflects therefore on the CO2 emissions amount, determining a decrease in this regard. Further reduction of CO2 emissions could be possible by progressively diversifying the power generation spectrum and including RES such as biomass and waste. e. Mitigation Solution In order to enable a slick transition towards environmentally friendly power supply also for the conventional generation, the operating traditional plants have to be upgraded. More in detail, they should comprise decarbonization technologies, facilities with improved combustion efficiency and employ alternative fuels with low carbon footprint [2]. Further, flexibility requirements (evaluated based on the mismatch between the energy demand and the continuous supply and the boundaries of the confidence interval limits) have to be satisfied to increase the high reliability of supply. A general microgrid layout, depicted in Fig. 16, could be adapted according to the particularities of each region. The proposed architecture exploits the advantages of poly-generation configurations, including storage devices and uninterruptible power supply technologies. More in detail, the RES have been selected taking into account the local availability, to increase energy independence on a local level. The storage section comprises two devices, with different response characteristics and timeframe suitability (Li-ion battery for short time and reversible solid oxide fuel cell for medium to long time). The microgrid could operate in interconnected mode, in order to ensure overproduction flow towards areas with production lack. Furthermore, a diesel group equipped with a methanation unit is integrated within the microgrid, emphasizing carbon capture and utilization features in a sustainable development framework.

5 Comparative Analysis to Other European Union Countries Further, a comparison is carried out among Romania and three other European countries (France, Germany and the Czech Republic), in order to establish a wider context in reference to the RES employment [1]. These three countries are selected based on their relevance when considering the use of RES in meeting national power balance, as shown in Fig. 17. In particular, RES share in 2018 reaches 21.2% in France, increasing by 2.91% since 2014. Further, it is remarked that the share structure for energy sources in Germany is somewhat similar to the Romanian one. More in detail, as depicted below, a steady annual increase of RES can be noticed, rising by 11.2% during the considered time horizon, up to 40.6% in 2018. In the Czech Republic, RES share in the total power production balance shows a reduction, getting in 2018 to a value almost halved (6.17%) compared to the one achieved in 2015 (11.77%).

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Fig. 16 General microgrid architecture definition [27]

Regarding the distribution by sources of energy generation in France, it emerges from Fig. 18 [28] that, among RES, hydropower has the largest share (10–12%); wind energy doesn’t exceed 5.1% in 2018, with a 1.9% increase compared to 2014; photovoltaic power production is relatively low, never exceeding 2%. Further, by analyzing the share of conventional power production, nuclear energy stands out as the main source, with a share of over 71.6% in 2018 (reduced from 76.92% in 2014). It is highlighted that France is the European country employing the largest amount of nuclear power. As the CO2 emissions for this source are null in operation, France achieves low CO2 emissions levels even with a reduced share of RES. It is interesting to evidence that the fall in using nuclear energy is compensated by a rise in of coal employment, reaching 10.3% in 2017, but dropping to 7.2% in 2018. Figure 19 presents the distribution by sources of the energy balance in Germany [29]. It is highlighted that, in the field of RES, wind energy gets the upper hand, almost doubling its contribution from 11% in 2014 to 20.5% in 2018. Hydropower accounts for 3.7% in 2018, while solar and biomass add up to over 8.2% from the

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Fig. 17 RES share comparison [16]

Fig. 18 Distribution by source of energy production in France [16]

Fig. 19 Distribution by source of energy production in Germany [16]

total production. In reference to the energy produced from conventional sources, it is noticeable a decline of 3.9% registered by nuclear energy employment, reaching 13.2% in 2018. The distribution by sources of energy generation in the Czech Republic can be observed in Fig. 20 [30]. Among RES, wind energy leads, followed by

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Fig. 20 Distribution by source of energy production in Czech Republic [16]

photovoltaics and hydropower. In reference to the classical resources, an increased share can be observed for coal. The maximum is attained in 2016 (50.87%), dropping however to 48.81% in 2018. Gas usage varies, with an average of 5.5%. Aside from nuclear energy (with shares within the range 30.36–36.88%), the share of conventional sources that issue CO2 through combustion is over 52–53%.

6 Conclusions It is estimated that there is still over 50% unexploited RES potential available on a regional scale over the Romanian territory. This enables a further increase of RES share in meeting the national energy balance, currently varying around 50% if including large hydro power plants. Thus, if implementing similar approaches to the one introduced in the present study, Romania could achieve a further up to 10% increase of RES share. If correlated with the proposed decarbonization technologies, the reduction in harmful emissions would be significant. From a flexibility perspective, it is highlighted that requirements are reduced if adjacent systems share their backup power resources. As the proposed microgrid configuration is equipped with complimentary generation and storage technologies, such distributed architectures enable increased energy independence and high operation performances, alternating as convenient the online source to meet the energy demand. It must be mentioned that an additional RES share augmentation can be achieved if exploiting the wave energy potential available on in the Black Sea. Although there are several investigations depicted on the literature on this regard, because there are still no operational facilities, this RES category it is not considered in the present study. In conclusion, passing to a decentralized generation structure is a feasible alternative in Romania, but given the strong territorial mismatch between RES potential and energy communities establishment, independent and economic affordable microgrids are not yet a viable solution. Interconnected poly-generation microgrids, including hybrid storage sections and uninterruptible power supply

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facilities are, based on the proposed outline, enable highly efficient and sustainable power system development. Further detailed analyses are to be carried out to define particular microgrid configuration and evaluate their performances. The analysis carried out in this paper shows that Romania exhibits a high percentage of RES in energy production, with hydropower owning the largest share, followed by wind power. In particular, RES share varies within the range 38.2– 43.2%. Periods of drought have a significant impact on the national power grid during the studied time interval, an extreme and localized drought causing a drop in hydropower use. This is compensated by the use of fossil fuels to cover the production loss. When compared to Germany or the Czech Republic, coal use in Romania contributes by a halved share in the total power production. Therefore, the national CO2 emissions remain at an acceptable level in reference to the Paris Agreement terms, never exceeding 315 g/kWh. Countries relying heavily on nuclear energy, such as France, can reach low CO2 emissions even without capital investments in the field of RES technologies. Considering that the largest percentage of power produced in France (up to 77%) comes from zero CO2 emissions sources (nuclear power), the national emissions levels are sensibly low. However, the future for nuclear energy is still uncertain, furthermore when considering that policies regarding production and waste management policies vary widely across the European Union. By analyzing the statistical data presented in this paper, a pass from coal to gas emerges first, followed by a switch to RES. The possibility to develop RES-based production and to proceed towards low carbon power generation, rests largely on the topology and climate of the country. Romania shows numerous opportunities in this regard.

Bibliography 1. IRENA.: Global Energy Transformation: A Roadmap to 2050 (2018). https://doi.org/10.1007/ s00063-001-1014-y 2. Krajačić, G., Duić, N., Vujanović, M., Kılkış, Ş., Rosen, M.A., Al-Nimr, M.A.: Sustainable development of energy, water and environment systems for future energy technologies and concepts. Energy Convers. Manag. 125, 1–14 (2016). https://doi.org/10.1016/j.enconman. 2016.08.050 3. Lund, H.: Renewable energy strategies for sustainable development. Energy (2007). https:// doi.org/10.1016/j.energy.2006.10.017 4. Ciupăgeanu, D.A., Lăzăroiu, G., Barelli, L.: Wind energy integration: variability analysis and power system impact assessment. Energy (2019). https://doi.org/10.1016/j.energy.2019.07. 136 5. Calise, F., Costa, M., Wang, Q., Zhang, X., Duic, N.: Recent advances in the analysis of sustainable energy systems. Energies 11(10) (2018). https://doi.org/10.3390/en11102520 6. Brandoni, C., Shah, N.N., Vorushylo, I., Hewitt, N.J.: Poly-generation as a solution to address the energy challenge of an aging population. Energy Convers. Manag. 171, 635–646 (2018). https://doi.org/10.1016/j.enconman.2018.06.019

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7. Calise, F., Dentice d’Accadia, M., Libertini, L., Quiriti, E., Vanoli, R., Vicidomini, M.: Optimal operating strategies of combined cooling, heating and power systems: a case study for an engine manufacturing facility. Energy Convers. Manag. 149, 1066–1084 (2017). https://doi.org/10.1016/j.enconman.2017.06.028 8. Calise, F., Figaj, R.D., Vanoli, L.: A novel polygeneration system integrating photovoltaic/ thermal collectors, solar assisted heat pump, adsorption chiller and electrical energy storage: dynamic and energy-economic analysis. Energy Convers. Manag. 149, 798–814 (2017). https://doi.org/10.1016/j.enconman.2017.03.027 9. European Environment Agency.: The European Environment—State and Outlook 2020: Knowledge for Transition to a Sustainable Europe (2019). https://doi.org/10.2800/96749 10. International Energy Agency.: https://www.iea.org 11. Lazaroiu, G., Ciupageanu, D., Vatuiu, T.: Highlights of renewable energy integration impact: evolution and perspectives in Romania. In: SIELA Conference, pp. 11–14 (2020) 12. Sueyoshi, T., Goto, M.: World trend in energy: an extension to DEA applied to energy and environment. J. Econ. Struct. 6(1) (2017). https://doi.org/10.1186/s40008-017-0073-z 13. Ciupǎgeanu, D.-A., Lǎzǎroiu, G., Tîrşu, M.: Carbon dioxide emissions reduction by renewable energy employment in Romania. In: 2017 11th International Conference on Electromechanical and Power Systems, SIELMEN 2017—Proceedings, Vol. 2017 Jan (2017). https://doi.org/10.1109/SIELMEN.2017.8123333 14. Akinyele, D.O., Rayudu, R.K.: Review of energy storage technologies for sustainable power networks. Sustain. Energy Technol. Assessments. 8, 74–91 (2014). https://doi.org/10.1016/j. seta.2014.07.004 15. National Institute of Statistics.: Anuarul Statistic Al Romaniei (2013) 16. Lăzăroiu, G., Mihăescu, L., Jarcu, E.A., Stănescu, L.A., Ciupăgeanu, D.A.: Renewable energy employment in Romania: an environmental impact discussion. In: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM, Vol. 2020 Aug (2020). https://doi.org/10.5593/sgem2020/4.1/s17.023 17. Dumitrascu, M., Grigorescu, I., Micu, D., et al.: Renewable energy, climate change and environmental challenges in Romania. In: 2019 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), Bucharest, pp. 1–5 (2019) 18. Schneider, D.R., Duić, N., Raguzin, I., et al.: Mapping the potential for decentralized energy generation based on res in western balkans. Therm. Sci. (2007). https://doi.org/10.2298/ TSCI0703007S 19. https://www.anre.ro 20. www.transelectrica.ro 21. Haas, R., Panzer, C., Resch, G., Ragwitz, M., Reece, G., Held, A.: A historical review of promotion strategies for electricity from renewable energy sources in EU countries. Renew. Sustain. Energy Rev. 15(2), 1003–1034 (2011). https://doi.org/10.1016/j.rser.2010.11.015 22. Ciupageanu, D.-A., Lazaroiu, G., Barelli, L.: Variability assessment of renewable energy sources based on power generation recordings. In: 18th International Multidisciplinary Scientific GeoConference SGEM2018, Albena, Bulgary, pp. 807–813 (2018). https://doi.org/ 10.5593/sgem2018/4.1 23. Vatuiu, T., Mihaescu, L., Lazaroiu, G.: Sustainable management of the forestry fund by implementing the integrated information system for the welfare of wooden materials. In: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM (2018). https://doi.org/10.5593/sgem2018/2.1/S07.107 24. Lazaroiu, G., Mihaescu, L., Negreanu, G., et al.: Experimental investigations of innovative biomass energy harnessing solutions. Energies 11(12), 3469 (2018). https://doi.org/10.3390/ en11123469 25. Ciupǎgeanu, D.-A., Lazaroiu, G., Barelli, L.: Wind energy integration: variability analysis and power system impact assessment. Energy 185, 1183–1196 (2019). https://doi.org/10.1016/j. energy.2019.07.136

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Chapter 2

The Matrix of Energy Biofuels Gheorghe Lazaroiu, Lucian Mihaescu, Dana-Alexandra Ciupageanu, and Gabriel-Paul Negreanu

Abstract Today, the notion of biomass (biofuels) includes the biodegradable part found in agricultural products, vegetable and animal waste and residues, forestry and wood industry, urban and industrial waste. A purely biological classification does not allow access to information on the energy use of biomass, which required the design of a biofuels matrix. In essence, the market success of a fuel depends on several factors, such as the energy quality expressed by calorific value, price/ calorific value ratio, and polluting effect. Today, worldwide, biomass represents 15% of the market share, but the degree of applicability differs greatly from one country to another. In the European Union, there are countries that have a share of biomass in the energy balance of over 10%. Keywords Biogas


Biofuel
Energy matrix
Renewable energy

1 Biofuels Definition The use of biofuels today is an energy vector in full development, being along with other renewable energy resources a way to reduce or eliminate fossil fuels. However, the notion of ecology must be joined by renewable energy, and this interaction becoming the symbol of the energy of the future. An in-depth analysis in this regard demonstrates an evolution at an extremely fast trend. There is a shortage of clean fuels, raw materials but also a shortage of water [1, 2]. Individual existence is increasingly dominated by globalization, but still the individual contribution remains extremely important. On this evolutionary level, it is found that the delays in the field of energy modernizations lead to an extremely G. Lazaroiu (&)
D.-A. Ciupageanu Power Engineering Faculty, University Politehnica of Bucharest, Bucharest, Romania e-mail: [email protected] L. Mihaescu
G.-P. Negreanu Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_2

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long response time, a fact highlighted by the theories of conceptual and investment inertia. Achievements in the field of biofuels both as an intrinsic value and as an applicative value in energy generation have led to a great diversification. As a result, a set of clarifications is required, materialized by co-opting them into a conceptual matrix, which defines their physicochemical and energetic characteristics [3, 4]. Currently, agricultural waste is a viable solution as biofuels, ahead of the contribution of forest waste. Both resources have a social reflection: The energy use of agricultural waste should not influence food resources, and wood should not come from excessive and uncontrolled deforestation [1, 5]. There is a strong interaction between energy production, fuel quality, and environmental pollution. A clean environment can in turn generate clean energy, even if only the energy produced by combustion is considered. Figure 1 shows this interaction. Regarding the use of wood in energy generation, there are successive transitions from the domination of waste to the domination of raw wood. The subsidy policy for stimulating the production of energy from renewable sources has sometimes made a decisive contribution to the use of raw wood [6]. The existence of individual households with the exclusive use of wood for heating and food preparation, but also of some agricultural, industrial, or tourism complexes contributes significantly to the increase of raw wood consumption. The primary use of biofuels is in the schemes as shown in Fig. 2. The efficiency of the conversion of biofuels into electricity does not usually exceed 25%, due to the low parameters of steam, specific to power installations below 10 MW. Moreover, it can be mentioned that the most common applications have global energy conversion efficiencies below 15%. Cogeneration improves low-efficiency values, thus reducing the specific consumption of biofuels [7, 8]. The energy crops developed recently come to supplement the need for biofuels. In the first places are the energy willow and poplar, but also the sorghum and miscanthus. Rapeseed has a special role, used mainly in transport and not in generating electricity or heat. Willow and poplar crops have a short period of growth and maturation, about 10 times shorter than in the case of afforestation. The extremely long period of wood growth in afforestation (of at least 30–35 years) actually blocks the investment effort for the business environment [9, 10]. It results

Fig. 1 Interaction between biofuels, energy, and environment

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Fig. 2 Use of biofuels for energy generation

that the afforestation actions remain only as an ecological way of sustainable development, possibly to be carried out by the local communities or by the state authorities [11]. The climate is an essential factor in the production of biofuels, and the economic criterion is defining for the selection of the range of biofuels, as well as in their grouping in the direction of use [12]. The time factor, as will be shown below, often changes the economic and environmental effects of the use of a particular type of biofuel. Particular importance must be given to increasing the efficiency of energy generation, including by implementing with new alternative sources and new energy conversion technologies. In turn, the consumer will have to be receptive to modern energy, even if he will be forced to give up the habits or even part of the old comfort [13]. Today, the notion of biomass (biofuels) includes the biodegradable part found in agricultural products, vegetable and animal waste and residues, forestry and wood industry, urban and industrial waste. Biomass is a result of solar energy, which is stored in the molecules of organic substances. This definition of embedded solar energy must be differentiated from some fossil fuels (oil, coal), which, although of organic origin, through physical and chemical transformations undergone during formation and storage, have become pollutants [14]. Biomass is classified by origin into: • • • •

primary biomass; secondary biomass; residual biomass; fossil biomass.

This purely biological classification does not allow access to information on the energy use of biomass, which required the design of a biofuels matrix. Regarding biomass residues [4], they are classified into: • primary residues; • secondary residues; • tertiary residues.

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Secondary residues come from the processing of primary biomass to produce food, or from the processing of wood biomass, including cellulose. The category of tertiary waste includes household waste, those resulting from wastewater treatment, etc. Energy biomass is represented by crops set up especially for the generation of electricity and heat, as well as for the propulsion of vehicles [15]. For this purpose, the following categories of crops are defined: • • • •

sugar plants (beets, sugar cane, sorghum, etc.); starch plants (potatoes, cereals); plants for vegetable oils (sunflower, rapeseed, corn); plants with lignocellulosic structure (willow, poplar, miscanthus). These crops are subjected to the following processes after harvest:

• direct combustion; • physicochemical transformations for transformation into derived fuels (gasification, pyrolysis, fermentation, and digestion). In order for a biofuel to be used for energy purposes, it must meet a set of criteria: • there is a volume of production that satisfies the demand at a competitive price; • to have technologies for harvesting, transport, and storage at the level of needs; • the existence of a technological chain for the transformation of biomass into derived fuels; • their efficient use for energy purposes in dedicated installations. Only those fuels that meet all these criteria will be required over time. In fact, since the start of biofuel use programs, there have been trends to impose some to the detriment of others. Nor can the enthusiasm of some individuals or companies for the taxation of one or another of the types of biofuels be neglected. The notion of a free market has also emerged with difficulty in this area. In essence, the market success of a fuel depends on: • energy quality expressed by calorific value; • price/calorific value ratio; • polluting effect. These qualities imposed in the definition of a biofuel can slow down its use over time, even if initially the enthusiasm or the legislation defined it with a certain potential. Figure 3 shows the possible evolutions over time for a biofuel [16]. There is an initial increase in the implementation phase of the new fuel, even if it does not present a perspective in time (b). The real conditions, both the technological ones and the ones dictated by the price, correct in time the evolution on the market of the biofuel, establishing both its market value and the share. Today, worldwide, biomass represents 15% of the market share, but the degree of applicability differs greatly from one country to another.

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Fig. 3 Possible consumption over time for a biofuel

In the European Union, there are countries that have a share of biomass in the energy balance of over 10%.

2 Biomass Used in E.U. For Energy Generation a. Wood Biomass Forest residues have a higher energy quality than agricultural ones. Problems arise with the price of harvesting on sloping forests or with the quality of the bark different from bark, as shown in Table 1 [12]. For wet solid fuels at initial condition, the technical analysis includes: V i þ Cfi þ Ai þ Wti ¼ 100 %

ð1Þ

The calorific value will depend on the moisture content, which for raw wood can reach 70%. Figure 4 shows the variation of calorific value with humidity.

Table 1 Characteristics of wood biomass

Characteristic

Peeled wood (%)

Bark (%)

Vanh (volatiles) Cfanh (fixed carbon) Aanh (ash)

77–80 19.4–22.6 0.4–0.6

73–74.6 21–24.7 2.3–2.4

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Fig. 4 Calorific value of wood biomass versus moisture content

The bulk density is also important, which varies between 420 and 910 kg/m3. Industrially, only dry wood is used, with a maximum of 30% humidity, when the calorific value for raw wood varies between 12,400 and 14,400 kJ/kg. The energy derivatives of raw wood are represented by briquettes, maxi-briquettes, pellets, sawdust, and charcoal. The lighters and pellets are made of humid wood, pressed under a certain size and shape. Instead, the manufacture of charcoal includes a pyrolysis phase, which removes moisture and volatiles, remaining a product containing fixed carbon and ash, with a calorific value of about 17,500 kJ/kg [2]. A common feature of all types of biomass is the high oxygen content, present in the elemental analysis (the most complex energy analysis) C i þ H i þ Sic þ Oi þ N i þ Ai þ Wti ¼ 100 %

ð2Þ

The analysis is expressed in gravimetric weight percent, and besides the terms defined in (1) there are more: • • • • •

Ci—carbon; Hi—hydrogen; Sic —combustible sulfur; Oi—oxygen; Ni—nitrogen.

The elemental analysis can be expressed for the “initial” state (s) of the fuel, the “anhydrous” state (anh) or the “combustible mass” (mc). For biomass at the initial state, oxygen has values in the range of 30–50%, and sulfur has an insignificant content ( 1 for the use of a stabilizer that divides the flame). The experiments were carried out in the gas burning laboratory of the Thermodynamics Department of the Polytechnic University of Bucharest. In Fig. 7, there is presented an overview of the experimental stand in the gas burning laboratory at the Department at the Polytechnic University of Bucharest. The 1  1.20 (m) combustion chamber is disposed on 4 supports at a height of 1 m from the ground, thus allowing different types of burners to be mounted. This combustion chamber is made of four walls with heat-resistant glass embedded in a metal frame, so it is extremely easy to see the flame characteristics at all angles as well as the combustion mode. The burner place is centrally located in the combustion chamber. For combustion gasses evacuation, this combustion chamber is connected to the central air vent of the laboratory. Also, the room also has a movable wall (front) to allow access to fit different types of combustion stabilizers and research equipment [20–22]. The burners are supplied from a network of natural gas, equipped with a flow meter for measuring gas flow. Maximum gas flow is 2 m3N =h, so the maximum boiler output is 20 kW. Burners for kinetic combustion study are with automatic drawing in air design. For diffusive burners, they must be connected to an air source for the experiments performed, a small compressor being connected to the system, as shown in Fig. 7. The tests were carried out using a gas prepared by Linde by mixing in pressure cylinders of a similar gas mixture in concentration with the biogas obtained from the pilot plant of anaerobic fermentation.

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Fig. 7 Overview of the experimental stand in the Gaseous Fuels Laboratory

Three versions of gas were prepared to cover the variation in the quality of biogas. In Table 6, the gas compositions of the three bottles are presented, the bottle I represent the average composition and the most common in the process of biogas generation. In order to make it possible to supply the burners at their working pressure, a two-stage pressure reducing valve was required. Figure 8 is the pressure reducer mounted on one of the cylinders. In all measured measurements, a gas flow in the field 0.88–1 m3N =h was constantly maintained.

Table 6 The composition of the biogas from the three cylinders

Cylinder I Cylinder II Cylinder III

CH4 (%)

CO2 (%)

H2 (%)

N2 (%)

CH4/CO2 (%)

Hii (kJ/m3N)

52 60 40

45 32 56

1 1 1

2 7 3

1.15 1.87 0.71

18,700 21,550 14,400

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Fig. 8 The pressure reducing valve mounted on one of the cylinders

As shown in Fig. 9, the gas flow (black hose) is measured with a rotameter. The connection line between the rotameter and the burner is the yellow one. The left rotameter is for airflow measurement (red pipe). As in Fig. 9, an automatic drawing-air burner is fitted, there is no air connection to the burner. The comparison of the gasses was done using a gas analyzer throughout the experiment.

Fig. 9 Rotameter used to measure fuel-gas flow

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Fig. 10 SMART VIEW 4.1. Fluke IR thermal camera used

In these experiments, a thermal camera for measuring flame temperatures was also used, shown in Fig. 10. The tests were performed using both existing technologies for combustion of gaseous fuels: kinetics (air premixing) and diffusion. The Wobble criterion was used when configuring the two burners because the calorific power and the density of the biogas (synthetic gas in the cylinders) are different from those of methane (CH4). Using the Wobble test, the experiments performed were successful for all measured parameters for all three types of gas and for both types of burners, which are capable of having a stable flame and complete combustion and low emission of pollutants. The adjustment of the thermal power of the burners, which represents the product between the fuel flow and the lower calorific value of the biogas, to obtain the necessary flow is done using the Wobble criterion. Pt ¼ B
Hii kW W0 ¼

pffiffiffiffiffiffi H i Dp pffiffiffii q

ð18Þ ð19Þ

where Dp—the overpressure at the burner inlet; Hii—lower calorific value; q—gas density. The thermal power required to be observed throughout the experiments was 3
defined by the flow rate of 0.88 mN h and the gas in cylinder I:

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Pt ¼

0:88
18; 700 ¼ 4:57 kW 3600

ð20Þ

The gas flows for the other qualities were: 3
BII ¼ 0:76 mN h

ð21Þ

3
BIII ¼ 1:14 mN h

ð22Þ

Applying the Wobble criterion to make those adjustments required changing the pffiffiffiffiffiffi dimensions of the gas nozzles and the supply pressure ( Dp). In Fig. 11, the variation of the biogas density according to its composition is presented characterized by the criterion R. There is an increase in the density of biogas depending on the increase of CO2 content because its density clearly exceeds the density of methane. Analyzing the Wobbe criterion, it results that the greatest influence of the setting of the working parameters on the burner is for the kinetic combustion with air premix. For diffusive combustion, if the working pressure is not changed, it is only possible to act directly on the size of the gas nozzle. For the three grades of gas in the cylinders, the working pressure Dp2 relative to the combustion of methane Dp1 must correspond to the values in Fig. 12. For diffuser burners, if the inlet pressure of the biogas is not adjusted, the size required for the diameter of the nozzle d2 compared to the diameter of the nozzle d1 for methane, and the data in Fig. 13 must be observed.

1.04

biogas density ρ [kg/m3N]

0.66, 1.03

1 1, 0.975 0.96

0.92

0.88 0.45

1.5, 0.92

0.65

0.85

1.05

1.25

R

Fig. 11 Variation of biogas density depending on its composition

1.45

1.65

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10 9 0.66, 8.7

Δ p2/ Δ p1

8 7 6

1, 5.98

5 4

1.5, 3.92

3 0.45

0.65

0.85

1.05

1.25

1.45

1.65

R Fig. 12 Influence of biogas quality on burner inlet (Dp2) pressure compared to methane (Dp1)

1.6

d2/d1

1.45

0.66, 1.44

1.3 1, 1.26 1.5, 1.18 1.15

1 0.45

0.65

0.85

1.05

1.25

1.45

1.65

R

Fig. 13 The influence of biogas quality on the variation of the burner nozzle diameter

4.2

Kinetic Combustion of Biogas

The first experiments were carried out with an automatic drawing-in burner for kinetic firing, shown in Fig. 14. The central duct is intended for gas supply. At the bottom is the air suction system, driven by a nut. At the top, there is a connection with the stand and the flame exit section.

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Fig. 14 Automatic drawing-in burner used in the experiments

In the first part of the experiment, a stabilizer with a hole system was used. In Fig. 15, the flame stabilizer with a total diameter of 75 mm is illustrated, comprising 160 holes with a diameter of 3.4 mm each. In Fig. 16, the appearance of the kinetic flame is presented at one point, a test performed with the gas from cylinder I. 3
For the gas flow, B = 0.88 mN h and the excess air k = 1.03, the fluid flow 3
coming out of the stabilizer holes was 0.0014 m s. The flow rate through the flame stabilizer was: u ¼

V 0:0014 3
¼ ¼ 3:04 m s d2 p
0:00342 np 4 160
4

ð23Þ

According to the data in the previous chapter, for a gas with a calorific value of
18 700 kJ m3 , the normal kinetic rate of combustion is S0n ¼ 2:35 m=s: Thus, the N

flame is in the stability zone with a slight removal from the exit section of the burner, as can be seen in Fig. 16.

Fig. 15 Dimensions of the flame stabilizer with a hole system

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Fig. 16 Kinetic flame of automatic drawing-in burner with hole stabilizer (cylinder 1)

The temperature histogram indicates high temperatures in the flame core, normal for a very small excess air (k = 1.03). The temperature in the ignition area was 260 °C, and the walls of the stand were 46.5 °C. The histogram shows a high-performance combustion, demonstrating the existence of high temperatures in the flame core, not demonstrated by classical measurements (Fig. 17). In Fig. 18, the flame is presented for the low gas quality, according to the composition in cylinder III. The flame is adequate, but the temperature histogram narrows considerably. Another stabilizer system used during kinetic combustion experiments was the slit system. Different images with this stabilizer are illustrated in Fig. 19. This stabilizer has a system of 23 slits with a thickness of 1 mm arranged at a distance of 1 mm (Fig. 20). In Fig. 21, the experimental stand on which the automatic drawing-in burner and the stabilizer with slit system are mounted is observed. It is noticeable the realization of the flames in the form of feathers, a shape generated by the flow between the slits of the stabilizer. As the flow width between the slits is larger than that through the holes of the 3
previous stabilizer, it was possible to increase the gas flow to 1 mN h. Equality of flow velocity with combustion velocity, as shown in Fig. 21. led to a stabilization of the flame exactly in the exit section of the burner. Next, the combustion stability with a ceramic tunnel stabilizer was studied. This stabilizer in the first stage achieves a relaxation of the fluid, so that, for lower fuels with a high CO2 content and having a low combustion rate, and its equality with the

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Fig. 17 Combustion test performed with cylinder I (captures taken from IR 0086, 00: 46 s): a real image; b infrared image; c temperature histogram

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Fig. 18 Kinetic gas combustion in cylinder III with hole stabilizer (captures taken from IR 0099, 01:11): a real image; b infrared image; c temperature histogram

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Fig. 19 Stabilizer with slit system

Fig. 20 Dimensions of the flame stabilizer with slit system

flow rate is achieved. In the second stage, the heating of the ceramic mantle makes it in turn become a thermal source of ignition and therefore of stability. In Fig. 22, the appearance of the kinetic flame is presented when using a stabilizer with ceramic tunnel, in the first test phase, for the gas in cylinder I. The exposed data regarding the kinetic combustion of gas with flame splitting stabilizers, respectively, with holes and slits, lead to the conclusion that this gas and of course biogas with the same composition can be used with energy recovery in installations equipped with self-extracting burners. In addition, the flame stabilization systems used in natural gas (CH4) were found to remain applicable in this case as well. However, as in the case of natural gas, strict compliance with the aerodynamic conditions of stability is required.

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Fig. 21 Kinetic flame of automatic drawing-in burner with slitted stabilizer

Fig. 22 Kinetic flame of the automatic drawing-in burner using a stabilizer with ceramic tunnel

4.3

Diffuse Combustion of the Analyzed Biogas

A new set of experimental tests were performed with a diffuser burner. In Fig. 23, the diffusive burner intended for diffuse combustion research is presented. The fuel gas comes out of a central nozzle, framed by an annular section for air intake. The

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Fig. 23 Diffusive burner

operation of the burner is based on the diffusion of gas in the air stream, the ignition being achieved in the section where the stoichiometric concentration is achieved. In Fig. 24, the flame image is shown when using the 5-hole gas inlet from the test phase. The reddish-blue color shows a reduced excess of air, so a proper adjustment. The test is performed with gas II of average calorific value. In Fig. 25, the images obtained at the combustion of the gas for the gas nozzle with a single central hole are presented. As expected, the flame lengthened and the

Fig. 24 Flame splitting image for the first device

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Fig. 25 Diffuse combustion of gas from cylinder II with central orifice nozzle (captures taken from IR 0139): a real image; b infrared image; c temperature histogram

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temperature increased compared to using the 5-hole nozzle. The same excess air and flow rate was maintained as in the previous test set, where the air was not swirled. Excess air was 1.03–1.06. No vertexing was used to make a more obvious comparison with kinetic combustion (with air-gas premix).

5 Conclusions on the Experiments The big length of the flame obtained when using a nozzle without radial holes implies the need to swirl the air. Swirling, through the radial air velocity, contributes to changing the appearance of the flame, which thickens to the detriment of its length. Through internal recirculation currents, it also contributes to the general increase of the flame. Table 7 summarizes all experimental results on pollutant emissions. The kinetic flame was higher for the superior gas quality. Thus, the flame length varied according to the quality of the gas according to the data in Fig. 26. Table 7 Pollutant data on emissions for the two types of combustion Parameter

Kinetic combustion

Diffusive combustion

Output gas velocity (m/s) Air excess (-) Axial velocity of the air (m/s) NOx (ppm) CO (ppm) Degree of swirling (-)

1.68 1.03–1.07 – 8–20 Max 30 –

21 1.07 27 Max 22 Max 40 1.15

Fig. 26 Flame length at kinetic combustion depending on biogas quality

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Fig. 27 Temperature in kinetic flame

If the average temperature of the flame contour for the gas, in cylinder I is about 1200 °C, for the gas of the lowest quality (cylinder III), it has decreased, the maximum value being 1065 °C—Fig. 27. CO2 emission measurements have in all cases indicated an appropriate reduction in normal CO2 emissions for an energy fuel. Thus, at the base of the kinetic flame, the CO2 emission was 500–600 ppm, reaching the maximum value of 30 ppm as indicated by the data in the previous table. For diffusion burning, the value decreases by oxidation from about 3000 ppm to a maximum of 40 ppm. The turbulence of the air reduced the length of the flame to about 1/3 of the initial length of the non-turbulent flame and to an increase in the intensity of combustion in the base area of the flame so that excess air could be maintained in the range of 1.02–1.03. The vortex flame (degree of vortex n = 1.15–1.7) by intensifying the combustion also contributed to the reduction of carbon monoxide emission at the end of combustion, at the value of 5–15 ppm. NOx emission was below the 20 ppm limit.

Bibliography 1. Popper, L., Raduti, C.: Economy Efficiency of Energy Systems . Printech Press, Bucharest, Romania (2005) 2. Tripşa, I.: Utilization of renewable resources for energy, S.C. CHIMINFORM DATA S.A., pp. 1–25, Bucharest (2006) 3. Birtas, A., Voicu, I., Chiriac, R.: Constant volume burning characteristics of HHO Gas. Theory Pract. Energ. Mater. III, 244–250 (2009)

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4. Mihăescu, L., Pîșă, I., Negreanu, G., Lăzăroiu, G., Berbece, V., Pop, E., Bartha, S., Enache, E.: Achievements and perspectives of solid biomass energy valorization. In: 9th International Conference on“ Biomass for Energy”, Kyiv, Ukraine (2013) 5. Mirza, U.K., Ahmad, N., Harijan, K., Majeed, T.: A vision for hydrogen economy in Pakistan. Renew. Sustain. Energy Rev. 13, 1111–1115 (2009) 6. Nenițescu, C.D.: Chimie general. București, Editura Tehnică, România (1963) 7. Mavrodin, M., Lăzăroiu, G.: Experimental research on combustion of biogas obtained through anaerobic fermentation of tanneries wastes. U. P. B. Sci. Bull. Ser. B 80(3), 1454– 2331 (2018) 8. Pîșă, I.: Combined primary methods for NOx reduction to the pulverized coal-sawdust co-combustion, FUPROC 3562. Fuel Process. Technol. 106, 429–438 (2013) 9. Pîșă, I.: The flue gas recirculation to supress nitrogen monoxide formation in combustion installations. Rev. Chim. 4(57), 387–392 (2003) 10. Pîșă, I., Lăzăroiu, G.: Influence of co-combustion of coal/biomass on the corrosion. Fuel Process. Technol. 104, 356–364 (2012) 11. Pîșă, I., Mihăescu, L.: The Romanian boilers endurance in the biomass combustion. In: 3rd International Conference on Applied Energy, Perugia, Italy, pp. 1735–1740 (2011). 978-889-058-430-5 12. Polihroniade, A.: Absorbţia – Adsorbţia, București, România: Ed. Tehnică (1967) 13. Lakó, J., Hancsók, J., Yuzhakova, T., Marton, G., Utasi, A., Rédey, A.: Biomass—a source of chemicals and energy for sustainable development. Environ. Eng. Manag. J. 7, 499–509 (2008) 14. Lăzăroiu, G.: Impact of Power Plants on Environment. Politehnica Press, Bucharest, Romania (1967) 15. Lăzăroiu, G.: Modeling and simulating combustion and generation of NOx. Fuel Process. Technol. 88, 771–777 (2007) 16. Lăzăroiu, G., Traistă, E., Bădulescu, C., Orban, M., Pleşea, V.: Sustainable combined utilization of renewable forest resources and coal in Romania. Environ. Eng. Manag. J. 7, 227–232 (2008) 17. Lăzăroiu, G., Mihăescu, L., Prisecaru, T., Oprea, I., Negreanu, G.: R, Indrieș, Combustion of pitcoal—wood biomass brichettes in a boiler test facility. Environ. Eng. Manag. J. 7, 595–601 (2008) 18. Lăzăroiu, G., Pop, E., Negreanu, G., Pîșă, I., Mihăescu, L., Bondrea, A.D., Berbece, V.: Biomass combustion with hydrogen injection for energy applications. Energy 127, 351–357 (2017) 19. Pîșă, I., Lăzăroiu, G., Mihăescu, L., Prisecaru, T., Negreanu, G.: Mathematical model and experimental tests of hydrogen diffusion in the porous system of biomass. Int. J. Green Energy 13, 774–780 (2016) 20. Pîșă, I., Lăzăroiu, G., Prisecaru, T.: Influence of hydrogen enriched gas injection upon polluting emissions from pulverized coal combustion. Int. J. Hydrog. Energy 39, 17702– 17709 (2014) 21. Lăzăroiu, G., Pană, C., Mihăescu, L., Cernat, A., Negurescu, N., Mocanu, R., Negreanu, G.: Solutions for energy recovery of animal waste from leather industry. Energy Convers. Manag. 149, 1085–1095 (2017) 22. Lăzăroiu, G., Pană, C., Mihăescu, L., Cernat, A., Negurescu, N., Mocanu, R., Negreanu, G.: Green Tannery—Methods for Energetic Recovery of Biodegradable Wastes. project ID PN-II-PT-PCCA-2013-4-1017, UPB 2013–2017

Chapter 7

Feasibility and Experimental Study of Cogeneration Plant Using Wood Biomass Gasification Process Iliya Iliev and Angel Terziev

Abstract Different aspects of the system for simultaneous production of electric and thermal energy (cogeneration) through biomass gasification are presented. Various features of the processes of biomass preparation, syngas production, syngas cleaning and combustion in the cogeneration set are presented and discussed. Based on the characteristics of the syngas produced proposed is a variety of systems for cleaning and cooling the syngas and also for tar removal. Thermal and mass balances are presented for each step of the gasification process. Recommendations for the use of the produced electrical and thermal energy are also made. Keywords Gasification


Feasibility study
Wood biomass
Cogeneration

1 Overview of the Forest Biomass Potential in Europe Forests are classified as a crucial resource for the supply of wood material for energy production from renewable energy resources. In numerous studies, [1–4] assessments have been performed in terms of estimation the biomass potential from forests worldwide. Appropriate analysis of the spatial distribution of said potential across the European continent and how local country politics affect the biomass production and further processing is presented in [5]. Moreover, the study provides suggestions on how forest owners could improve the biomass production process and what the costs of organizing such a process would be.

I. Iliev (&) Agrarian and Industrial Faculty, University of Ruse, Ruse, Bulgaria e-mail: [email protected] A. Terziev Faculty of Power Engineering and Power Machines, Technical University of Sofia, Sofia, Bulgaria e-mail: aterziev@tu-sofia.bg © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_7

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In terms of utilization, the following types of forest biomass materials could be classified [6–8]: • Base potential: this potential is in accordance with the acting guidelines for sustainable forest management. Legal restrictions in terms of protected areas are also included; • Technical potential: this is the maximum potential of wood material potential when the minimum restrictions are applied; • High potential: this potential is a Base potential with less restrictions focussing on the technologies for green energy production; • Significant potential with enriched biodiversity protection (BIOD): this is a Base potential where the entire volume of wood shaped is reduced by 10% because of the presence of protected areas. Figure 1 [5] is a representation of these four types of forest wood material distribution. The total amount of biomass based on the Base potential amounted to 401 Tg of dry matter per year (Tg.yr−1). 88% of this volume refers to trunk wood, while the waste material amounted to 12%. In terms of total biomass production, the estimations of forest wood biomass potential across the EU amount to 144 Mtoe. The currents studies show that the domestic biomass potential for Europe ranges between 16 and 737 Mtoe from 2050 onwards. The agricultural biomass potential is compared with the forest biomass, and it is estimated to 124 MToe. In Fig. 2, the energy consumption of biomass in 2017 and EU potential in 2050 is presented.

Fig. 1 Base, Tech, High and Biod forest wood potentials distribution in 39 European countries

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Fig. 2 Source Bioenergy Europe, Faaij (2018), biomass availability for energy production applications across Europe

2 Simultaneous Production of Thermal and Electric Energy (Cogeneration) Through Biomass Gasification Process 2.1

General Information

Biomass gasification is a fairly complex technology, and biomass plants through gasification need to comply with different European standards and norms. The various process steps and potential Health, Safety and Environmental aspects in a typical such plant are illustrated in Fig. 3. The typical process of a cogeneration power plant through biomass gasification is presented in Fig. 4. There are different wood biomass gasification technologies, but down-drawn gasification technology is a suitable one for decentralized biomass utilization when keeping the high efficiency of thermal and electric energy production. There are four general stages in a power production process: • Fuel storage and supply. Preliminary treatment of the raw material is needed in order to comply with gasifier specifics; • Biomass gasification process. Different gasifying technologies can be applied— fixed and fluidized bed. Operating condition of the gasifying process should be observed. Gasification utilities (water vapour, air, additives) are of great importance to the gasification process.

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Fig. 3 Potential Health, Safety and Environmental aspects of gasification plants [9]

Fig. 4 Stage of biogas production through gasification process [9]

• Gas cooling and cleaning systems. Different types of cyclones and wet and dry cleaning technologies are applied to clean the produced syngas from solid particles and gaseous admixtures. • Cogeneration power plant. Gas engines, turbines and micro-gas turbines are used to burn the syngas produced by the gasification process.

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2.2

183

General Information of Large Scale Biomass Gasification System

Wood waste as a fuel has several environmental advantages over fossil fuels. The main advantage is that it is a renewable resource, offering a sustainable and dependable supply. In addition, the amount of carbon dioxide (CO2) released through the burning process is usually 90% less than when burning fossil fuels. Wood fuel contains minimal amounts of sulphur and heavy metals. It cannot inflict acid rain pollution, and its particulate emissions are mostly controllable. Alternatively, the lower wood waste price makes the use of this energy source more attractive than competing fossil fuels. Certain biomass power plant includes but is not limited of course to the following elements: place where the biomass material is stored, cutting and dehydrating equipment; gasification unit; gas cleaning system; cogeneration unit; wastewater processing system and a couple of stages water cooling systems. Figure 5 [10] is a representation of biomass power installation.

Fig. 5 Principle schemes of the biomass gasification system

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2.3

Technology Overview

2.3.1

Biomass Processing Unit

The waste wood material is collected in a storage, and then via front loaders are transported to the transport line leading the material to the chipper machine. After shredding, large pieces of wood residues or metal debris are removed by operator. Then, the wood chips are transferred with a line further and enters into drum dryer. The wet material moves in a dryer because of the rotation flow, and drying air is supplied in a counter current direction. Purpose of the drying of the wood material is to be met the needs of the gasifier. The thermal energy for drying the wood material comes from the exhaust flue gases produced by the co-generator. The preliminary process dried material is directed to the daily storage. Screw conveyors are used to transport the material from storage to the gasifier. The amount of transferred material depends of the thermal characteristics of the material and mode of the facility. The installed capacity of the raw material preparation system is 11.7 kW which is 0.02% of the electric power of the biomass system (5 MWel).

2.3.2

Dryer

The proposed drum dryer purpose is to reduce the raw material moisture content from 35 to 15%. This is crucial for the proper operation of the gasifier unit. The size of the facility requires presence of three drying units with total capacity of 150 tonnes per 24 h. Usually, the thermal energy needed to dry the wet wood material is supplied by the co-generator sets, and it is result of their cooling. Moisture content of the wood biomass is normally expressed either with dry basis (DB) or wet basis (WB). The respective relations are as follows: DB; % ¼

Wwet wood  Woven dry wood :100%; Woven dry wood

ð1Þ

WB; % ¼

Wwet wood  Woven dry wood :100%; Wwet wood

ð2Þ

where W is the weight of the respective material Mathematical interpretation of drying the sawdust material is presented in [11]. An overview of the rotary and flash dryers is presented in Fig. 6a, b.

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Fig. 6 Wood dryers: a rotary type, b flash type [12]

2.3.3

Gasifier

Gasification is a process where the burning gas is released when the wood material is heated to a very high temperature. There are different technologies that can be applied for the gasification of solid fuels [13]. The basic classification of these processes is carried out by considering the basic reactor principles that are applied, i.e.: • fixed-bed systems; • fluidized-bed systems; • entrained flow systems; The process of gasification of solid biomass can run at standard (atmospheric) or gauge pressure. During both operating conditions, the thermochemical conversion of wood material occurs and syngas (combustible) gas is released. For proper running of the thermochemical conversion process, the exact amount of solid material and gasification media should be provided. In terms of the technology pure oxygen or water vapour are used as catalysts in the gasification process. Those two elements are used the syngas toe be released from the wood material. The produced gas should pass through series of cooling and cleaning processes before using as a thermal energy producer. Usually, the lower calorific value of the cold syngas depends on the stages of cleaning and cooling. The efficiency of the processed gas is defined as the amount of energy used to “brake” the chemical bounds of the produced gas. This indicator is extremely valuable and can be used to compare the production efficiency using different technologies. The stated efficiency can be expressed with (Eq. 3): g¼

LHVpr gas :Q_ pr gas ; LHVfuel :m_ fuel

ð3Þ

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where LHVpr Q_ pr

gas —Low

heating value of the producer gas (kJ/nm3);

gas —Volume

flow rate producer gas (nm3/h);

LHVfuel —Low heating value of the fuel (biomass) (kJ/kg); m_ fuel —Mass flow rate of fuel (biomass) (kg/h). The gasification process includes pyrolysis of the raw wood material where the reduction of the concerned products is realized in the presence of atmospheric air. Then combustible (methane, carbon monoxide, hydrogen and higher hydrocarbons) and inert gases, (carbon dioxide and nitrogen) are produced. The gasification process of the raw material starts at a high temperature (300– 600 °C) when the volatile matter is released. In case of excess air, unstable products are burnt to carbon dioxide, water vapour and certain amount of carbon monoxide are produced which is a function of mixture content. This is a releasing energy process which can further support both the pyrolysis and combustion processes by relocating thermal energy to raw wood material. This process takes place at temperatures of 1200–1400 °C. There are a numerous reactions running into the gasifier where the thermal energy is released and consumed. The produced syngas contains CO2 and H2O, which further react with the atomic carbon to produce H2O to H2. Furthermore, in the process, the syngas temperature is reduced, as the thermal energy is stored in CO and H2 molecules. The chemical reactions running into the gasifier are presented in Table 1. The process syngas after couple of cooling stages has to follow composition of 20% CO, 20% H2, 2% CH4, 12% CO2 with the remaining share of N2 and also equilibrium moisture content. The excess amount of water carries with the hot gases with temperature of about 600 °C and further condenses where the syngas is cooled to the ambient temperature. Before entering the cleaning systems in terms of composition of the raw material, the produced syngas can contain carbon dust

Table 1 Reactions type and energy during the pyrolysis process Reactions Devolatilization Steam-carbon Reverse boudourd Oxidation Hydrogasification Water gas shift Methanation

DH (kJ/mol) C + heat = CH4 + condensable hydrocarbons + char C + H2O + heat = CO + H2 C + CO2 + heat = 2CO C + O2 = CO2 + heat C + 2H2 = CH4 + heat H2O + CO = CO2 + H2 + heat 3H2 + CO = CH4 + H2O + heat 4H2 + CO2 = CH4 + 2H2O + heat

131.4 172.6 −393.8 −74.9 −41.2 −74.9

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entrained by the ascending hot gas and also some amount of remaining volatile matter called tar. Cleaning of the impurities of the produced syngas is crucial for save and reliable operation of the internal combustion (IC) engines where the gas is burnt. Therefore, a well-designed gasification system must be equipped with the effective gas cooling and cleaning systems, and also, amount of the produced contaminants should be kept in the requested by the cogeneration unit limits. Based on the technology specifics, the following gasifiers are distinguishable: updraft; downdraft; double fire and two stages (Fig. 7). The first two types are applied for small and medium-scale power installations. The proposed biomass gasification system applied for this facility is Ankur Downdraft Gasifier system. This is a closed top type gasifier system (Fig. 8). Air is drawn from the tuyeres arranged around the periphery to enter a zone below the fuel storage section. The air comes via nozzles at reasonably high velocities so that it can penetrate into the core region of the reactor. Below the air nozzle, space is provided up to a zone where the gas flow is designed to pass through a constriction called a throat. This ensures that the hot gas gets mixed sufficiently with the air and passes through the throat region in the porous bed. The high velocities ensure high temperatures, and the small zone of passage ensures adequate mixing to cause the breakdown of tars into small fragments. The reactor is operated by loading with

Fig. 7 Typical configurations of gasifiers (updraft, downdraft, double fire and two stages)

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Fig. 8 a Separate zones in the gasifier with indication of loading the biomass and charging the gas; b picture of gasifier WBG-2000 type. Source Ankur

charcoal to start with (for the first time) and then loading biomass periodically as it is consumed. The biomass loses volatiles because of heat from the combustion zone. This char then moves downstream and gets consumed by the gasification reactions. The char then reacts with airflow along with the volatiles generated in the zone above. The product gases flow downstream because of the reaction with air, fragmentation as a result of load from above and thermal stresses. The raw material’s grain size can affect significantly the performance of the gasification process because of increased pressure drop, including slagging. It is the main reason for the proper preparation of the raw material when using a downdraft gasification system. Table 2 presents the specifics in using the downdraft gasification technology. The gasification start-up process needs a certain amount of energy which is provided by the charcoal. When the process is steady, the raw material is continuously supplied into the gasifier.

Table 2 Feedstock specifications for downdraft gasification. Source Ankur

Moisture content

% Mass, dry

10 up to 20

Grain size Share of fine wood particles Ash content

cm % Mass, wet

1.5 up to 8 1.15 dosages. On alcohol use at ICE’s, the analysis extends the experimental investigation for methanol use at the ICEs for two diesel engines fueled by methanol, D115 aspirated engine and D2156MTN8 supercharged engine. The fuel diesel substitution with methanol at D115 engine was a maximum of 50% and brake specific energetic consumption is smaller than conventional engine. NOx emissions are formed in the diesel engine in preformed mixtures and in the spray kernel due to the great

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influence of temperature. For the same engine power, the NOx emission level decreases due to methanol influence (the methanol vaporization leads to lower temperature during fuel diesel injection). At the increase of the amount of methanol, the level of NO, NOx and smoke emissions is smaller versus standard diesel fuel operation. At over 50% energetic percent of substitution of diesel fuel with methanol use leads to an accentuated increase of smoke emission due to the worsening of combustion process. At the truck D 2156 MTN 8 turbocharged engine, the methanol injection during the rapid combustion phase leads to the decrease of the brake specific energetic consumption at minimum value. The variation of the energetic substitution coefficient of the diesel fuel with methanol, in 47–80% ensure the reduction of the NOx and CO2 emissions level at 100–25% engine load. The NOx relative concentration decreases due to the cooling effect produced by the methanol vaporization. The minimum CO2 emission concentration was obtained for 35 % methanol substitution ratio. Over 35% methanol substitution ratio, the smoke emission concentration increased, and the engine efficiency accentuated decreased.

3.3

Conclusions on LPG Use

For K9K diesel engine, the use of LPG, in different energetic substitution ratios xc, leads to the decrease of pollutant emissions. At full engine load and 2000 rpm speed regime, in the case of diesel and LPG fueling, the NOx emission level is reduced by a maximum of 40% at LPG compared to the value recorded in the case of only diesel fueling. The replacement of diesel in 2.58% ensures a reduction of NOx emission by 21% compared to the value measured for diesel and by 35% at xc = 4.48. For xc = 9.25, the most important reduction is obtained, of 40%, but the economy of the engine can be compared with that of the classic engine, being slightly reduced. It can be stated that from this point of view, the maximum reduction obtained from the emission of nitrogen oxides is achieved in the conditions of maintaining the efficiency of the engine. If the criterion of the maximum obtained economy is followed, for xc = 2.58, a considerable reduction of the emission by 20% can be ensured. At the speed of 4000 rpm, there is a continuous reduction of nitrogen oxides emission, the maximum reduction obtained in the case of diesel and LPG supply, being 21% at xc = 40. For intermediate substitution coefficients the NOx emission level is reduced comparative to clasic fuelling, with 5,1% for xc = 18.3 and with 7.8% for xc = 29.5. Considering the criterion of economy, the reduction of NOx emission by 21% implies the reduction of the effective efficiency of the engine, respectively, the increase of the specific energy consumption. The 5% emission reduction can be achieved while maintaining the engine efficiency in the range established by the classic solution. The reduction of NOx emission to the partial substitution of diesel by LPG can be explained based on the tendency to reduce the available oxygen and to reduce the gas temperature. The CO2 emissions levels show a slight reduction compared to diesel fuel supply for all

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277

degrees of substitution used. The most important 3% discount can be obtained while maintaining the engine efficiency. The reductions are more accentuated for the regime of 4000 rpm, with a decrease of 8% compared to the classic feeding solution. The reduction of CO2 emissions can be achieved without affecting the engine efficiency. The reduction of CO2 emission is attributed to the reduction of the amount of carbon in the mass composition of the final fuel, when substituting diesel with liquefied petroleum gas. Thus, at low substitution ratios, up to 9.25%, the CO2 emissions level is modestly reduced by a maximum of 2% compared to diesel fuel. At the subsequent increase of the substitution coefficient, with up to xc = 40%, the reduction of the CO2 emission level is more important compared to the previous situation, of about 7% compared to diesel fuel. An important reduction is also ensured in the case of the emission level of unburned hydrocarbons, for the speed regime 2000 rpm. The reduction becomes important even from small quantities of LPG introduced in the engine intake: 49% reduction compared to the reference value at a percentage xc = 2.58. The maximum reduction was achieved for xc = 9.25, with a decrease of 77%. In the conditions of maintaining the specific energy consumption at a value very close to that of the classic diesel engine, an important reduction of the emission of unburned hydrocarbons by 68–77% can be ensured. The HC emission level decreases by 36% compared to diesel and at maximum power speed, the degree of reduction being related to the substitution coefficient xc = 29.5. Important reductions for the HC emission level of the order of 30–50% can be achieved in the conditions of maintaining the economy in operation for the two speed regimes. The high-speed combustion of homogeneous air–LPG mixtures ensures the reduction of HC emissions by increasing its proportion in the cylinder. The smoke emission decreases with maximum 40% at LPG use at regime of 2000 rpm and full load. Further increase of LPG dose leads to the increase of the smoke emission level but the registered value is with 25% lower comparative to diesel fueling. At the speed regime of 4000 rpm, the most important reduction of smoke emission level is 55% and is registered at low LPG quantities. The increase of LPG dose at raised values also decreases the smoke opacity by 28–35% versus classic fueling. This increase tendency of smoke opacity once with the rise of LPG dose may represents a factor for LPG quantity limitation. As future perspectives, the experimental investigations will be extended to alternative fuels substitution degrees and to other operating regimes and engine parameters tune.

Bibliography 1. Vision 2050: A Pathway for the Evolution of the Refining Industry and Liquid Fuels. Fuels Europe. European Union Communication, Brussels. www.fueleurope.com (2018) 2. Negurescu, N., Pana, C., Popa, M.G.: Spark Ignition Engines. Processes. Publisher Matrixrom, Bucharest (2003) 3. Butlin, R.N., Simmons, R.F.: The inhibition of hydrogen-air flames by hydrogen halides. Combust. Flame 12(1968), 447–456 (1968)

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4. Goran, S.H.: The upper limit of flammability of hydrogen in air oxygen ann oxigen- inert mixtures at elevated pressures. Combust. Flame 17, 295–301 (1971) 5. Heywood, H.B., Vilchis, F.R.: Comparison of flame development in a spark ignition engine fueled with propane and hydrogen. Comb. Sci. Techn. 38 (1984) 6. Selected Values of Chemical Thermodynamic Properties-Part I. Tables, National Bureau of Standards Circular 500. Reprinted July 20, 1961 7. Pischinger, P.: Internal Combustion Engines Hydrogen Fuelling. MTZ 37(3), 71–72 (1976) 8. Negurescu, N., Pana, C., Popa, M.G., Cernat, A., Soare, D.: The control of the running of the hydrogen fueled spark ignition engine. 2th European Conference H2-FuelMillenium_Convergence 2008, e-Hydrogenia, Academy ROMANA Bucharest, September 18–19, 10 pp. ISBN 10:973-1704-12-4, ISBN 13:978-973-1704-12-8 (2008) 9. Mac Carley, C.A.: A Study of Factors Influencing Thermally Induced Backfiring in Hydrogen Fueled Engines, and Methods for Backfire Control, 16-th IECEC Conference. Atlanta, USA (1981) 10. Negurescu, N., Pana, C., Popa, M.G.: Aspects Regarding the Combustion of Hydrogen in Spark Ignition Engine; SAE 2006–01–0651 (2006) 11. Berger, E., Bock, C., Fisher, M., Gruber, M., Kiesgen, G., Rottengruber, H.: The New BMW12-cylinder Hydrogen Engine Clean Efficient and Powerful Vehicle Powertrain; FISITA World Automotive Congress, YOKOHAMA, paper F2006P114 (2006) 12. Negurescu, N.: Researches regarding the SIE Hydrogen Fuelling. PhD Thesis. Institute Politehnic Bucharest (1980) 13. Conte, E., Boulouchos, K.: Influence of Hydrogen-Rich-Gas Addition on Combustion, Pollutant Formation and Efficiency of an IC-SI Eng, SAE paper 2004-01-0972 (2004) 14. Negurescu, N., Pana, C., Popa, M.G., Cernat, A.: Performance comparison between hydrogen and gasoline S.I. Fuelled engine, ThSci2011.036. J. Therm. Sci. 15(4), 12, 1155–1164. https://doi.org/10.2298/TSCI110203090N (2011) 15. Negurescu, N., Pană, C., Popa, M.G., Cernat, A.: Experimental researches of a hydrogen fuelled SI engine. J. Energy Power Eng. 4(7) (Serial No.32), 1–8. ISSN 1934-8975, USA (2010) 16. Negurescu, N., Pana, C., Popa, M.G., Cernat, A.: Experimental and theoretical researches of hydrogen use in S. I. engine. International U.A.B.—Balkan Environmental Association (B.E. N.A). J. Environ. Protect. Ecol JEPE B.EN.A. 12(4A), 2275–2287. ISSN 1311-5065 (2011) 17. Pana, C., Negurescu, N., Popa, M.G., Cernat, A., Soare, D.: An Investigation of the Hydrogen Addition Effects to Gasoline Fueled Spark Ignition Engine, Paper No. 2007-01-1468, SAE World Congress 2007, Detroit, Michigan, USA. ISSN 0148-7191 (2007) 18. Negurescu, N., Pana, C., Cernat, A.: Aspects of Using Hydrogen in SI Engine, University Politehnica of Bucharest. Sci. Bull. Ser. D Mech. Eng. 74, 11–20. ISSN 1454-2358 (2012) 19. Negurescu, N.: Researches on integral hydrogen fueling of a SIE. Research Raport Grant CNCSIS 27, 2006–2008, Journal of Science Policy and Scientometry—special issue VI. ISSN-1582-1218 (2008) 20. Negurescu, N., Pana, C., Popa, M.G., Cernat, A., Soare, D.: Experimental Investigations Concerning the Direct Injection in Hydrogen Fueled S.I. Engine, Paper F2008-09-028, FISITA2008, World Automotive Congress 2008, 14–19 September, Munich, Germany, 10 (2008) 21. Pechlivanoglou, G.: Hydrogen Enhanced Combustion History, Applications and Hydrogen Supply by Plasma Reforming, University of Oldenburg PPRE 2005–2007 22. Lambe, S., Watson, H.: Optimizing the design of a hydrogen engine with pilot diesel fuel ignition. Int. J. Vehicles Des. 14, 370e89 (1993) 23. Talibi, M., Hellier, P., Balachandran, R., Ladommatos, N.N.: Effect of hydrogen-diesel fuel co-combustion on exhaust emissions with verification using an in-cylinder gas sampling technique. Int. J. Hydrogen Energy 39, 15088–15102 (2014) 24. Saravanan, N., Nagarajan, G., Sanjay, G., Dhanasekaran, C., Kalaiselvan, K.M.: Combustion analysis on a DI diesel engine with hydrogen in dual fuel mode. Fuel 87, 3591–3599 (2008)

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25. Cernat, A., Pana, C., Negurescu, N., Nutu, C., Mirica, I.: Performance comparison between hydrogen and diesel fuel fueled compression ignition engine. Sci Bull UPB Ser D Mech Eng 77, 4. ISSN 1454-2358 (2015) 26. Cernat, A., Pana, C., Negurescu, N., Fuiorescu, D., Nutu, C., Mirica, I.: Experimental aspects of hydrogen use at diesel engine by diesel gas method. Therm. Sci. 22(00), 138–138 (2018). https://doi.org/10.2298/TSCI170314138C 27. Cernat, A., Pana, C., Negurescu, N., Lazaroiu, G., Nutu, C., Fuiorescu, D.: Hydrogen—An Alternative Fuel for Automotive Diesel Engines Used in Transportation. Sustainability 12, 9321. https://doi.org/10.3390/su12229321 www.mdpi.com/journal/sustainability (2020) 28. Cernat, A., Pana, C., Negurescu, N., Nutu, C., Mirica, I.: The Effect of Hydrogen Use on Diesel Engine Performance. 20th Innvative Manufacturing Engineering and Energy Conference (IManEE 2016) IOP Publishing IOP Conference Series: Materials Science and Engineering 161, 012075. https://doi.org/10.1088/1757-899X/161/1/012075 (2016) 29. Panǎ, C., Negurescu, N., Popa, M.G., Boboc, G., Cernat, A.: Performance of a DME Fueled Diesel Eengine. 5th International Colloquium “FUELS 2005”, Technische Akademie Esslingen, Germania, pp 227–232. ISBN 3-924813-59-0 (2005) 30. Popa, M.G., Negurescu, N., Pana, C.: Diesel engines. Processes. Matrix Rom Bucharest (2003) 31. Pana, C., Negurescu, N., Popa, M.G., Cernat, A., Soare, D.: Aspects of the Use of Ethanol in addition with Gasoline Spark Ignition Engine. The 6th International Colloquiuium Fuels Proceedings, Technische Esslingen. ISBN 3-924813-67-1 (2007) 32. Negurescu, N., Pana, C., Popa, M.G., Cernat, A., Soare, D.: Aspects of Using Ethanol in SI Engines. FISITA Congress-Yokohama, Japan (2006) 33. Pana, C., Negurescu, N., Popa, M.G., Cernat, A., Soare, D.: Aspects of the Use of Ethanol in Spark Ignition Engine. Paper No. JSAE 20077271 (SAE 2007–01–2040). JSAE/SAE International Fuels and Lubricants Meeting, Kyoto, Japan. ISBN 978-4-915219-92-4 (2007) 34. Pana, C., Negurescu, N., Cernat, A.: Improvement of the automotive spark ignition engine performance by supercharging and the bioethanol use. World Congress FISITA 2012, F2012-B01–007 (2012) 35. Ulrik, L., Troels, J., Jesper, S.: Ethanol as a Fuel for Road Transportation-Main Report. Technical University of Denmark (2009) 36. Radu, A.: Researches regarding the use of the ethanol in the spark ignition engine. PhD Thesis, University Politehnica of Bucharest (2012) 37. European Union. Directive 2009/28/EC of the European Parliament and of the Council (2009) 38. CEEX. Bioethanol obtained by unconventional methods from regenerative source used in addition in fuels. Contract 613/2005. University Politehnica Bucharest (2005) 39. Popa, M.G.: Research about the Methanol Use as Fuel for Compression Ignition Engine. PhD. Thesis, University Politehnica of Bucharest (1982) 40. Popa, M.G., Negurescu, N., Pană, C.: Control of diesel engine pollutant emissions by methanol use. Man and Environment -a VII-a edition of Timis Academic Days. ISBN 973-8247-31-4 (2001) 41. Popa, M.G., Negurescu, N., Pană, C., Racovitză, A.: Results obtained by methanol fuelling diesel engine. SAE Technical Papers Series 2001–01–3748. Proceedings of the 2002 Environmental Sustainability Conference and Exhibition, p. 365, Graz, Austria (2002) 42. Racovitza, A., Pana, C., Negurescu, N., Popa, M.G., Boboc, G.: Improvement of heavy-duty diesel engine operation when using methanol-diesel double injection fueling method. The 5th International Colloquiuium Fuels Proceedings, Technische Esslingen. ISBN 3-924813-59-0 (2005)

Chapter 12

Technologies for Energy Production from Lignocellulosic Agricultural Residues Georgii Geletukha, Semen Drahniev, Tetiana Zheliezna, Vitalii Zubenko, and Olha Haidai Abstract Lignocellulosic agricultural residues are huge, but a considerably underutilized resource of biomass is available for energy. Mobilization of this potential for energy gives an opportunity to provide a secure energy supply contributing to the decarbonization of the energy sector. The chapter presents an original approach to introduce in the energy flow the lignocellulosic agricultural residues, in particular in areas where these ones are highly present. The improvement of quality and efficiency of agricultural residues’ combustion requires using special equipments and technical solution for fulfilling the environmental requirements, presented in this chapter. The operation of energy equipments impacts the environment. Thus, environmental impact assessments are required to evaluate the level, the possible effects and to determine regulations update.
















Keywords Bioenergy Biomass Biofuels Agricultural residues Straw Corn residues Sunflower residues Life-cycle assessment







1 Technologies for Energy Utilization of Straw At present, lignocellulose agricultural residues are not prevalent in power engineering and have inconsiderable share in the world’s energy balances. Nevertheless, the agrarian countries (include Ukraine) have high potential for use of agricultural residues. The availability of new, efficient technologies and equipment makes the prerequisite for the wide use of agricultural residues in the future. Ukraine has limited amount of fossil fuels and significant national plans for the development of renewable energy. In addition, the reduction of greenhouse gas emissions needs the attraction of new kinds of biomass for energy production. G. Geletukha (&)
S. Drahniev
T. Zheliezna
V. Zubenko
O. Haidai Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kyiv, Ukraine e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_12

281

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Wood biofuels use depletes own potential for increasing but agricultural residues have huge potential and opportunities for energy sector development. Necessity of larger use of agricultural residues also follows from the analysis of biomass consumption structure. Furthermore, wide development of the energy use of agricultural residues is cumbered by a number of substantial limitations imposed by organizational and technological solutions, environmental requirements and a lack of big practical experience. Ukrainian market does not have a large number of technological equipment manufacturers, and high cost of their products prevent the transition to the use of agricultural residues in the energy sector and the district heating sector. The deceleration in economic development in the world and the fast decrease in the price offossil fuels directly affect the bioenergy development and decline interest in the realization of new bioenergy projects. Simultaneously, both the return of high prices for fossil fuels and the increase of investment in the renewable energy sector, where bioenergy continues to take a leading position, are expected in the nearest future.

1.1

Technologies and Equipment

Improvement of the agricultural residues combustion quality and efficiency need the use of particular equipment and technological solutions in order to meet environmental requirements. A detailed overview of burning technologies with an estimation of the benefits and shortcomings was presented in the manual on the preparation and implementation of natural gas replacement projects with biomass [1, 2]. Direct burning is a time-proved technology and is described by its simplicity and affordability. Present improvement of these technologies tries to solve the problems of environmental contamination, possibility to burn different fuels, increasing efficiency, and integration in cogeneration cycles. Biomass gasification is more complex technology, which has not achieved commercial status but can use low-quality fuels. The most widespread technology of agricultural residues burning is a vibration water-cooling grates (Table 1); less common are technologies of crushed biofuels jet fire and fluidized bed combustion. These burning technologies have different types of heat-producing equipment with wide scope of capacities from small domestic boilers to big power plants. The technology of periodic burning is broadly implemented in hot-water boilers and hot-air heat generators with a capacity of up to 1 MW. Fuel in the form of bales is supplied into a large burning chamber. The fuel burning continues for 4–5 h, and only after that, the next portion of fuel can be supplied. The main requirements of farms to heat-producing equipment are simple construction, less mechanization, and accessible price. The main consumers of heat energy from agricultural residues are residential premises, warehouses, drying chambers, and small heating networks. The main shortcoming of the periodic burning of biomass is the low level of burning control. It is the cause of large amount of emissions during the lighting of the boiler.

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Table 1 Combustion technologies and features of their use [3] Technology Bed combustion: - Fixed grate

- Chain grate

- Vibrating and pushing water-cooling grates

Dust (flame) combustion Fluidized bed (BFB, CFB)

Features of use Hot-water boilers and heat generators of batch burning with capacity up to 1 MW, manual and mechanized fuel supply, fuels with homogeneous composition and low water content Co-combustion of different agricultural residues with coal, fuels with inhomogeneous composition and fraction, used at the modernization of existing boilers (up to 50 MW), including CHP Fuel with homogeneous composition and fraction, used at the reconstruction of existing boilers and in new boilers (capacity up to 120 MW), including CHP, is the basic technology of agricultural residues burning Co-combustion in existing coal-fired boilers, homogeneous fuel with fine fraction, over 100 MW capacity, includes TPP Co-firing, fuel with inhomogeneous composition and fraction, high water content and harmful impurities, over 30 MW capacity, includes CHP

“Cigar” burning technology with the agricultural residues post-combustion on the grate is effective in boilers with a capacity up to 10 MW. The privilege of the “cigar” burning is the low electricity consumption and no need for mechanical chopping of straw bales into chips. Large straw bales can be chopped into several pieces and supplied into the boiler fire chamber. This simplification decreases investment and operating costs at the heat production. Fluidized bed burning technology as well as biomass dust burning technology is widely implemented for co-combustion of agricultural residues with coal [4] at existing coal-fired power-generating units with a capacity of more than 100 MW. This technology has small investment costs for reconstruction (50–1500 $/kW), which allows mixing up to 20% of agricultural residues to the main fuel without capacity reducing. Fluidized bed burning technology allows regulation a big range of boiler capacity and the share of agricultural residues in the fuel mixture from null to 100%. The main restrictions are the ability to provide sufficient amounts of agricultural residues. These technologies are implemented at TPP and CHP with supercritical parameters of steam (over 200 bar, 520–540 °C) which ensures the electricity production with high efficiency (Table 2). The most of companies deliver turnkey technological solutions from fuel warehouse to a chimney. It reduces to a minimum the risks of incompatibility at the use of equipment from different producers, reduces the duration of project implementation and determines the person responsibility for the whole complex efficiency. The total reliability of the object is estimated by the reliability of the weakest unit in the whole technological chain of production. So not only the main technological equipment (boilers, turbines) must have the best quality but also the

1989

Volund

Straw

26

20

Cigar, grate

67

26.532

455

19%

88%

Fabric filter

Fuel

Fuel consumption, thousand tons

Boiler heat output (MW)

Combustion technology

Working pressure of desks (bar)

Steam productivity (t/h)

Steam temperature (C)

Electrical efficiency of CHP

Boiler efficiency

Gas cleaning

Useful heat release (MW)

Equipment supplier

13

Electric power (MW)

Commissioning

Haslev

5

Name

Fabric filter

89%

22%

450

12.96

60

Vibrating grate

11.2

14

Straw

B&W

1990

7.5

2.55

Rudkobing

Electrostatic

89%

25%

450

57.6

67

Moving grate

31

30

Straw

Aalborg

1990

28

11.4

Slagelse

Mabjer-gvaerket

Masnedo

90% Fabric filter

Fabric filter

88%

25%

–

Fabric filter

520

46.44

92

Vibrating grate

36.4

40

Straw, woodchips

B&W

1996

0

9

520

50.4

67

Vibrating grate, cigar

39

30

Straw, chips, pellets

Volund

1993

0

28

93%

33%

540

165.6

110

Vibrating grate

118

150

Straw

Bioneer

2009

75

35

Fynsvaer-ket

Electrostatic

92%

41%

510

122.4

210

Vibrating grate

80

120

Straw, woodchips

B&W

1998

Ensted-vaerket

Table 2 Description of TPPs and CHPs in Denmark using agricultural residues [5] Maribo

Fabric filter

88%

29%

540

49.68

102

Vibrating grate

37

45

Straw

FLS Miljo A/S

2000

22.5

10.6

Avedore 2

Electrostatic

94%

49%

310

144

310

Flame, grate

100

150

Straw + coal

FLS Miljo, B&W, Volund

2001

-

275

Amagervaer-ket

Electrostatic

95%

23%

562

500.4

185

Flame, grate

350

150

Straw pellets + coal

Electrostatic

-

42%

540

1033.2

250

Flame

no data

130

Straw + coal

2005 Babcock

Electrostatic

-

22%

505

104.04

92

Fluidized bed

88

40

Straw + coal

Aalborg

1992

40

2  455

2009

Grenaa 19,6

Studstru-pvaerket 2  350

B&W

250

80

284 G. Geletukha et al.

12

Technologies for Energy Production …

285

auxiliary equipment—fuel warehouses and supply systems, systems of ash removal and gas cleaning, heat and electricity supply systems. The comparative information about TPP in Denmark (Table 2) allows asserting that bed burning on moving grates is used for power plants with a capacity of up to 50 MW. In its turn, the co-firing of biomass with coal in a fluidized bed is used for capacities more than 50 MW. The boiler efficiency at the level of 88–95%, and the CHP electrical efficiency in the cogeneration regime is on average 22–33% can be reached owing to higher operating parameters of steam (60–250 bar, 455–562 °C). Use of bag filters in flue gas cleaning systems can ensure 20 mg/nm3 of particulate emissions that ensure compliance with current regulatory requirements. The cogeneration regime of CHP allows increasing of its efficiency up to 85% and decreasing of heat and electricity production cost. Table 3 is made based on the analysis of projects, which are accomplished in the world. It shows data about the main producers of boiler equipment for agricultural residues burning. Manufacturing of the equipment for agricultural residues burning is the most developed in Denmark. Weiss, Linka, Danstoker are the leaders among producers of straw-burning hot-water boilers in Denmark. Straw-burning boilers with 2–8 MW capacity use in general medium size of straw bales. Usually straw bales are chopped by stationary shredders, sometimes—cut into pieces, and after that are supplied in the furnace by use of hydraulic and screw supply systems. The pre-eminence of hydraulic supply systems is the minimal noise and mechanical wear of fuel supply elements. Fuel warehouses of power plants can be equipped with several cranes, which permits the discharging of some trucks with trailers simultaneously. The use of wheel loaders is cheaper but fuel supply system would have smaller efficiency. Stationary automatic emission control systems is installed on boilers to ensure the burning quality according to environmental requirements. The oxygen sensors control the oxygen content in the combustion products and as a result regulate the air supply in the furnace automatically. It is clear that the bed firing with different types of grates will remain the base technology of energy utilization of agricultural residues. Sunflower husks and pellets use for heat and electricity production is very popular in Ukraine. Domestic boilers with combustion of abovementioned fuels are widely used in existing TPPs and CHPs. The production of specialized energy equipment for the combustion of agricultural residues in Ukraine can be improved owing to close cooperation with leading European manufacturers. The “green” tariff for electricity in Ukraine is an important stimulation for bioenergy projects investment. Indirect extra advantages of such cooperation are the creating of new jobs and filling of local and state budgets.

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Table 3 Equipment manufacturers for agro-biofuels burning [3] №

Name/trademark

1 2 3 4

Agro Forst B&W Volund BWSC D'alessandro

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

Thermal capacity (MW) 5   







Danstoker DP CleanTech Enerstena EuroTHERM FAUST Gizex Granpal Heizomat HERLT HOST Justsen KARA Komkont Kovosta LINKA MetalERG







 

 

Passat Energi A/S Polytechnik GmbH PROTECH Sp. z o.o REKA Skeltek STEP Teisen Tenza TTS Boilers Uniconfort Verdo VYNCKE Weiss



 









 



     

  

   

     

    





http://protech-wkg.pl

  





     



 

http://www.agro-ft.at http://www.volund.dk/ https://www.bwsc.com/ http://www. caldaiedalessandro.it/ http://danstoker.dk/ https://www.dpcleantech.com http://enerstena.lt http://www.eurotherm.dk/ https://www.faust.dk/ https://www.gizex.com.pl/ http://granpal.pl http://heizomat.de/ http://herlt.eu http://host-bioenergy.com https://justsen.dk/ http://kara-greenenergy.com http://komkont.com/ http://www.kovosta.cz/ https://www.linka.dk/da/ http://kotlynaslome.pl/en/ main/ https://passatenergy.com/ http://polytechnik.com

   

https://www.reka.com/ http://www.skeltek.dk/ http://steptrutnov.cz https://www.farm2000.co.uk/ http://www.tenza.cz/ http://tts.cz/ https://www.uniconfort.com/ https://www.verdo.com/ http://vyncke.com/ https://www.weiss2energy.eu

12

1.2

Technologies for Energy Production …

287

Environmental Aspects

Building and running of energy equipment cause a many-sided impact on the environment. Current environmental legislation is sought at preventing environmental harm, providing of environmental safety, sustainable use, and recreation of natural resources. The aim of the environmental assessment is to recognize the level of impact, possible effects and providing of the current legislation requirements. Power plants with a thermal capacity of 50 MW and more are subject to environmental impact assessment because they have a considerable impact on the environment. According to DBN A.2.2-3-2014, CHPs and TPPs with a thermal capacity of up to 50 MW must develop a section on the evaluation of environmental impact in the project documentation. The environmental assessment is developed for the total object and is a mandatory clause for obtaining permits for emissions of pollutants into the atmospheric air. Nitrogen dioxide, hydrogen chloride, ammonia, sulfur dioxide, substances in the form of suspended solids, carbon monoxide, non-methane volatile organic compounds are the most harmful pollutants. State regulations in the field of environmental protection strictly regulate the authorized emissions of pollutants into the atmospheric air that depend on the type of fuel, the period of commissioning, capacity, flue gas cleaning systems, and combustion technology. Primary and secondary measures are used for solving the problem of meet to environmental requirements. Combustion regimes, organizational and preparatory measures are the primary methods. These may considerably reduce the formation of harmful substances by affecting burning in a furnace. Using of specialized gas cleaning equipment for reducing the concentration of already generated emissions is the secondary methods. Fuel with high quality, selection of equipment for the specified fuel, maintenance of the regime parameters and assembling of additional gas cleaning equipment are widespread approach to ensure compliance with the strict legislation requirements. The amount of pollutants in the flue gases depends most of the fuel elemental composition. Agricultural residues as a rule have a higher level of sulfur, nitrogen, and chlorine compared to wood waste, that is why appropriate technology and gas cleaning equipment should be used for their safe usage. Nitrogen oxides NOx are created owing to nitrogen contents in fuel. The traditional regime methods such as flue gas recirculation, the stage air supply, reduction of excess air ratio, moisture injection are used to reduce NOx. Some secondary methods additionally used because of primary methods have low efficiency. Secondary methods are based on chemical purification of flue gases —oxidative, reducing, and sorption. The decrease method with the use of ammonia (NH3) is the most promising. At present, two types of ammonia nitric oxide decrease are widely used in agricultural

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residues burning—the method of selective non-catalytic reduction (900–1200 °C) and catalytic (300–500 °C) decrease in the presence of a catalyst from oxides of various metals (titanium, chromium, vanadium). The efficiency of cleaning systems with such methods is 30–70% with the possibility of increasing to 90%. Due to the danger of using ammonia (high toxicity), carbamide is used instead of ammonia, otherwise: urea (NH2)2CO. Non-catalytic recovery has economic preferences over catalytic recovery. Large energy and industrial boilers and solid waste recovery boilers used the catalytic recovery. The availability of carbon monoxide (CO) in the flue gases indicates incomplete burning of the fuel. The decrease of CO emissions is achieved by primary methods. Typically, this is the optimal design of the furnace (providing sufficient time, temperature and mixing for complete combustion), fuel preparation (drying and/or chopping), and efficient air distribution in the furnace. Low-power boilers and boilers with periodic burning have high levels of CO emissions. These boilers have not proper regulation of air supply and compliance with operating temperatures. Sulfur (SOx) compounds pollute the air and cause corrosion of the metal of power equipment. The main source of pollution by sulfur compounds is the burning of coal and petroleum products, including the co-combustion of agricultural residues with coal. The double alkaline desulfurization and semi-dry desulfurization are two methods of purification of flue gases from sulfur oxides. Semi-dry desulfurization is a highly efficient, relatively inexpensive, compact, simple, and easy to operate system. The technology of the semi-dry method of desulfurization has an efficiency of up to 95%. The purification of flue gases from TPPs and CHPs mainly used this type of desulfurization. Ash is formed as a result of the solid agricultural residues combustion. Part of this ash enters the flue gas purification system. This system has purified the flue gas from solid particles. The cyclones, wet inertial ash traps, multicyclones, bag filters, electrostatic precipitators are usually used as technological solutions to ensure compliance with environmental standards. The principle of operation of cyclones and multicyclones is based on the use of centrifugal forces, and they are mechanical separators. A series of cyclones, which are operated in parallel, is the multicyclone. They are installed with the view to reduce the size of the unit. The efficiency of cyclones and multicyclones is 65% and 95%, respectively. Sometimes cyclones are installed before the bag filters or electrostatic precipitators as a precleaning measure. The electrostatic precipitators are often implemented for the particles deposition in the burning of agricultural residues. They are very effective (98–99.5%) and able to catch the particles with a size of 1 lm. Only the best bag filters correspond to the degree of the capture of the electrostatic precipitator. Electrostatic precipitators are characterized also by very low aerodynamic drag. Complexity of the operation and the significant capital costs are the disadvantages of electrostatic precipitator. Usually the electrostatic precipitator is installed on boilers with a capacity of more than 10 MW. The bag filters can catch very small particles (less than 1 lm) and have high efficiency up to 99.99%. Bag filters can reduce the concentration of solid particles

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in flue gases to 20–50 mg/nm3 (sometimes even to 10 mg/nm3), which is ensure compliance with environmental requirements. Bag filters have some disadvantages —a risk of burning the fabric, high aerodynamic pressure, significant capital costs, and the risk of decommissioning owing to clogging of filter materials and water vapor condensation. Therefore, for safety reasons, they are not used in small biomass boilers. Existing technologies for agro-biofuels combustion allow ensuring compliance with environmental requirements by installing only gas cleaning equipment to remove particulate matter. The majority of power plants use bag filters. Powerful CHPs and TPPs use also sulfur and gas purification.

2 Technologies for Collection and Energy Utilization of Corn Residues (Stalks, Cobs) Corn (maize) is a highly productive crop, which parts are widely used for many purposes in different industries, in particular: • • • • • • •

raw material for food; high-energy fodder in poultry farming and animal husbandry; feedstock for first- and second-generation biofuels; raw material for biogas; raw material for solid biofuels; fertilizer; feedstock in chemical, pharmaceutical, and other industries.

Corn is a crop with high agro-technological value as it cleans soil of weeds and is an excellent predecessor in crop rotation. Judging by the absorption of carbon dioxide and release of oxygen, corn is one of the best crops and is even more effective than a forest in the same area [6]. Agricultural machinery could be better used for corn growing due to the later time of the crop sowing and harvesting. Corn has a high demand on the world market because of its valuable properties. The USA has the world leadership in corn production and yield. In the 2019/ 2020 marketing year (MY), the production of corn in the USA was 345.96 Mt (31% of the global production), and the average yield was 10.51 t/ha (Table 4). Other leading countries in producing corn are China with the production of 260.78 Mt, Brazil—102.0 Mt, the EU—66.72 Mt, Argentina—51.0 Mt, and Ukraine— 35.89 Mt in 2019/2020 MY. The lead EU corn producers are Romania (17.3 Mt in 2019), France (13.0 Mt in 2019), and Hungary (8.3 Mt in 2019). From 2015 to 2019, the highest average yield of corn and corn-cob-mix was achieved in Spain (11.6 t/ha), Greece (10.3 t/ha), Austria, and Italy (10.1 t/ha) [7]. The increase in corn yield is related to the development of agricultural science and the use of biotechnology for the creation of hybrids. American farmers achieve corn yields of more than 250 m.c./ha in comparative tests. The USA National Corn

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Table 4 Main world producers of corn (by MY) [8] #

Country/ region

Area (million ha)

Yield (t/ha)

Production (million t)

2018/ 19

2019/ 20

2020/ 21

2018/ 19

2019/ 20

2020/ 21

2018/ 19

2019/ 20

2020/ 21

1

USA

32.9

32.9

33.4

11.1

10.5

11.0

364.3

346.0

368.5

2

China

42.1

41.3

42.0

6.1

6.3

6.2

257.3

260.8

260.0

3

Brazil

17.5

18.5

19.5

5.8

5.5

5.6

101.0

102.0

110.0

4

EU

8.3

8.9

9.0

7.8

7.5

7.1

64.4

66.7

63.7

5

Argentina

6.1

6.3

6.1

8.4

8.1

8.0

51.0

51.0

49.0

6

Ukraine

4.6

5.0

5.4

7.8

7.2

5.5

35.8

35.9

29.5

7

India

9.0

9.7

9.2

3.1

3.0

3.0

27.7

28.6

28.0

8

Mexico World

7.2

6.6

7.3

3.8

4.0

3.8

27.6

26.5

28.0

192.1

193.3

197.0

5.9

5.8

5.8

1123.4

1116.2

1143.6

Notes 2019/2020 MY—preliminary data, 2020/2021 MY—forecast (December 2020)

Grain, 47.6% Other, 1.2% Yield of corn 10 t/ha Leaves, 10.6% Stalks with shanks and sheaths, 28.8% Cobs, 7.5% HI = 0.48

Corn stover

Husks, 4.3%

Underground part of the plant

Fig. 1 Main aboveground parts of a corn plant and their mass ratio

Growers Association announced the world record about 386 m.c./ha of grain corn in Virginia in 2019 [9]. The growth of the average global corn yield (2016–2018) is expected to be 14% up to 2028 [10]. Residues of corn production, which are often called corn stover, consist of different underground and aboveground parts: stalks, leaves, shanks, sheaths, husks, cobs, and other parts (Fig. 1, the mass ratio data were taken from [11]). Corn stover is primarily made up of fiber, which consists of approximately 36% of cellulose, 23% of hemicellulose, and 20% of lignin [11]. The mass ratio between crop residues and grain of the crop (residue/grain ratio) depends on many different factors, mainly on a crop hybrid, but, on average, it is 1.3 for corn [12]. Currently, the major method for commercial corn harvesting is the use of combine harvesters equipped with corn reapers for cutting corn, threshing of ears, chopping corn stover, and spreading it in the field. When harvesting corn by this method, the combine harvester forms three streams of crop residues: stubble,

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EW + CB = 0.24 * Мgrain Behind the combine Stubble=0.1* Мgrain

SТ + LV = 0.96 * Мgrain Behind the reaper

Fig. 2 Scheme of indicative flows of corn residues harvested by a combine harvester

which stays on the field; stalks and leaves that remain behind the reaper; and wrap and cobs that remain behind the combine harvester (Fig. 2). In Ukraine, the theoretic potential of the corn residues available for energy (the whole amount of generated residues) was 46.5 Mt or 8.9 Mtoe in 2018. The economic potential of corn residues (the amount available for energy production, which is 40% of the theoretical potential) was 18.6 Mt or 3.6 Mtoe, including stalks—9.7 Mt (1.9 Mtoe) and cobs—3.3 Mt (0.6 Mtoe) [9]. By 2030, it is expected the increase in the corn residues potential for energy in Ukraine up to 19.2 Mt/yr or 3.7 Mtoe/yr. It could be achieved by the increase in corn yield in Ukraine up to the top indicators of EU countries. In 2018, the average yield of corn grain reached 7.84 t/ha in Ukraine. The present positive dynamics of the agriculture development in the country could support reaching the top EU levels of corn yield during the next 10 years in Ukraine. Agricultural residues production is seasonable and depends on harvesting periods. The harvesting periods of grain corn depend on the time of sowing, the variety, the place of cultivation, etc. Usually, the corn harvesting period is determined by the moisture content of grain. It is important to control the moisture content of the grain and its ripeness before harvesting, taking into account the hybrid ripeness group and the terms of sowing. Corn grain must have at least 45% dry matter content by the beginning of harvesting. September–November is a typical corn harvesting period in Ukraine. For instance, in 2016, by the beginning of October, corn was harvested from 24.4% of the total area (20.4% of the annual production), and by the beginning of November —from 65.7% of the area (61.4% of the annual production). By December 2, 2016, the harvested area under corn reached 95–100% in 10 regions. The farmers from the rest regions harvested corn from over 80% of the area. At that, corn harvesting was performed faster in the southern and central regions. In general, corn residues are characterized by relatively good fuel properties that are close to those of wood fuel. Due to that, the equipment intended for wood biomass can be used for burning solid biofuels made from corn residues. Characteristics and fuel properties of corn stover and corn cobs are given in Table 5. A comparison of characteristics of different agricultural residues and wood chips is presented in Table 6.

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Table 5 Corn residues characteristics and their fuel properties [14] Parameters

Samples of corn stovera #704 #889 #1241

Samples of corn cobsa #2068 #2791 #1454

Proximate analysis: Moisture content, War (%) 6.06 5.00 – – 7.04 – 5.06 7.35 5.58 3.48 3.12 3.60 Ash content, Ad (%) 85.17 84.30 79.61 – 80.69 83.20 Volatile matter, Vdaf (%) Ultimate analysis: 46.82 46.50 43.65 48.22 46.51 45.31 Carbon, Cd (%) 5.74 5.81 5.56 6.20 5.68 7.16 Hydrogen, Hd (%) d 0.66 0.56 0.61 1.57 0.47 – Nitrogen, N , % 0.11 0.11 0.01 0.13 0.09 43.93 Sulfur, Sd (%) 41.36 39.67 43.31 42.94 44.13 Oxygen, Od (%) Halides: #1240e Chlorine, Cld (mg/kg) 2661.3 0.0 6000.0 2100 – – 15.68 16.72 16.44d – 15.05 14.02d Net calorific value, Qar (MJ/kg) 19.06 20.50 18.69 19.95b Gross calorific value, 18.19 16.16 Qdaf (MJ/kg) Ash composition (%): #402c P2O5 8.68 – – – – 54.04 – – – – SiO2 1.99 – – – – Al2O3 CaO 8.66 – – – – MgO 6.11 – – – – 0.15 – – – – Na2O 20.67 – – – – K2O Ash melting behavior (°C) #402c Initial deformation – 1232 – 900 – 850 temperature (IDT) Hemispherical temperature – 1500 – – – 1000 (HT) Fluid temperature (FT) – 1500 – 1020 – – #979f Biochemical composition #2372g (%) Cellulose – 36.80 28.00 26.30 52.00 – Hemicellulose – 25.40 28.00 25.20 32.00 – Lignin – 16.90 11.00 16.30 15.00 – Upper indexes ar—fuel as received; d—dry matter; daf—dry and ash free basis a Numbers according to Phyllis database. bHHVMilne. cAsh composition and ash melting behavior for sample #402. dFor dry matter. eHalides for sample #1240. fBiochemical composition for sample #979. gBiochemical composition for sample #2372

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For further production of biofuels, the key quality factors of corn stover are ash content and ash melting behavior. The harvesting technology depends on the ash content. When biomass contacts with soil, the amount of ash in corn stover increases. There are structural and non-structural types of ash [13]. Structural ash consists of inorganic substances of the crop that remain after biomass burning. Usually, the ash content of corn stover is 3.5%. Unstructured ash is formed from inorganic substances, mostly soil. These get into biomass during harvesting, in particular when windrowing and baling takes place. In the case of multiple passes of agricultural machines during corn stover harvesting, the typical total ash content is 8–10%. Corn stover ash melting behavior is close to wood biomass that is better for combustion compared with cereal straw. For comparison: the ash melting temperature of corn stalks is about 1100 °C, and that for wood is about 1200 °C of (see Table 6). Furthermore, corn stover contains less chlorine (0.2% d.m.) compared with fresh (“yellow”) cereal straw (0.75% d.m.). This is a good factor for energy equipment because chlorine compounds in fuel cause corrosion of steel elements. The elemental composition of corn stover is similar to that of cereal straw, so their calorific values are almost the same. A place of cultivation, type of soil, fertilizers, harvesting time, and weather have strong influence on the properties of crop residues. The calorific value of corn residues mainly depends on their moisture content (Fig. 3). The harvesting of corn grain with the use of combine harvesters equipped with corn reapers provides a reduction in fuel consumption of 20–25% and a decrease in labor costs of 1.8–2 times in with technology of ears harvesting [15]. However, some farmers that collect corn for sowing use harvesting of non-threshed ears with the following stationary threshing, which enable to gather cobs. The collection of corn grain and cob mixture with combine harvesters is not widespread in Ukraine yet. In the case of the use of a combine harvester with a corn reaper, the parts of a corn plant are distributed in three flows (see Fig. 2): stubble (about 10% of the corn grain mass), mainly stalk and leaves behind the combine reaper (about 96% of the corn grain mass) and mainly ear wraps and cobs behind the combine harvester (about 24% of the corn grain mass). For improving logistics efficiency and decreasing the required area of warehouses, balers, which collect and press biomass in more than four times, can be used. There are four main types of technological systems for corn residues harvesting in bales: • Single pass: a combine harvester connected with a baler, which forms bales from corn residues simultaneously with corn grain threshing. • Two-pass: a combine harvester with a special reaper that forms corn residues windrows that are baled in the following stage by a baler attached to a tractor. • Three-pass: a combine harvester spreads corn residues, which are windrowed by a tractor with a windrower shredder, then a tractor with a baler presses them in large square bales (round bales).

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Table 6 Chemical composition and fuel properties of different biomass [9] Parameters

Yellow straw

Gray straw

Winter wheat straw

Corn stalks*

Sunflower stalks*

Wood chips

Moisture content (%)

10–20

10–20

11.2

45–60 (after harvesting) 15–18 (air dried)

40

Net calorific value (MJ/kg)

14.4

15

14.96

Volatile matter (%) Ash content (%) Ultimate analysis (%): Carbon Hydrogen Oxygen Chlorine Potassium (alkali metal)

>70

>70

80.2

16.7 (d.m.) 5–8 (W 45–60%) 15–17 (W 15–18%) 67

60–70 (after harvesting) *20 (air dried) 16 (W < 16%)

73

>70

4

3

6.59

6–9

10–12

0.6–1.5

42 5 37 0.75 1.18

43 5.2 38 0.2 0.22

45.64 5.97 41.36 0.392 –

45.5 5.5 41.5 0.2 Corn cobs: 6.1 mg/kg d.m 0.69; 0.3 0.04 1050–1200

44.1 5.0 39.4 0.7–0.8 5.0

50 6 43 0.02 0.13–0.35

0.7 0.1 800–1270

0.3 0.05 1000–1400

Nitrogen 0.35 0.41 0.37 Sulfur 0.16 0.13 0.08 Ash melting 800–1000 950–1100 1150 temperature (°C) d.m.—dry matter; W—moisture content *Data for volatile matter, ash content, and ultimate analysis are based

10.4

on dry matter

• Multipass: a combine harvester spreads corn residues, a tractor with a shredder shreds them, a tractor with a rake makes windrows from the biomass, and a tractor with a baler presses it. The three-pass system is the most rational for Ukraine due to the possibility of using standard machines that are available on many farms and due to less soil contamination of corn residues. This supply chain is used by the DuPont company for its cellulosic ethanol plant in the USA [16]. Local farmers harvest their corn, and the plant staff carries out corn stover collection and transportation. In addition, a round baler instead of a large square baler can be used for the corn stover baling, and, in this case, the biomass is pressed in round bales. Alternatively, corn residues can be shredded as a mixture of their various fractions or selected fractions such as cobs. The shredded corn residues harvesting can be performed

Net calorific value, MJ/kg

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16 14 12 10 8 6 4

10

15

20

25

30

35

40

45

50

55

60

Relative moisture content (War), % Fig. 3 Graph of the dependence of the net calorific value of corn stover from its moisture content (as-received basis)

with a forage harvester or a forage loader wagon that are used for silage corn harvesting. The ash content was 6.9 ± 2.0% d.m. for corn stover, harvested with a forage loader wagon, and 7.0 ± 1.9% d.m. for such biomass, collected with a forage harvester due to the results of field experiments of the Bavarian State Research Centre for Agriculture in 2014–2015 [17]. The collection of a part of corn residues after threshing grain with a combine harvester can be another option for corn stover harvesting. In 2018, the Italian company CREA-IT (Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria) carried out some on-field experiments to assess the performance of an innovative mechanized system for the corn cobs collection [18]. It was possible to harvest on average 2 t/ha of cobs with the biomass productivity of 4.1 t/h by using a combine harvester with the Harcob system [19]. For cobs harvesting, the Vermeer Company produces the CCX770 harvester machine [9]. The Vermeer CCX770 cobs harvester is a pull-type collection wagon attached to a combine harvester. This machinery enables farmers to harvest in one pass separately corn grain and corn cobs. Corn residues can be harvested by different machinery, which can be introduced in many technology systems. At the same time, taking into account the production run machinery available on the market and outcomes of field trials in the EU and the USA, it is rational to carry out the techno-economic assessment of four corn residues supply chains in Ukrainian conditions [9]: 1. SC1—the three-pass system with a large square baler: a combine, a tractor with a windrower shredder and a tractor with a large square baler; 2. SC2—the three-pass system with a round baler: a combine, a tractor with a windrower shredder and a tractor with a round baler; 3. SC3—the forage harvester system: a combine, a tractor with a windrower shredder, a forage harvester and a tractor with a trailer; 4. SC4—the forage wagon system: a combine, a tractor with a windrower shredder, a tractor with a forage loader wagon.

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Fig. 4 Corn stover yield in dry tons per hectare

Additionally, the corn cob harvesting technology with Vermeer CCX770 cob harvester will be assessed. For cost-effective corn stover harvesting, it is important to determine the reasonable cost of machinery and operating costs, which are different due to the quantity of harvested biomass from the field area, machines productivity, and transportation distances. In the USA, farmers harvest 2.5–5 t d.m. of corn stover from a hectare. In general, the corn stover collection efficiency can be assumed of 50%. The rest corn residues remain in the fields and can be used as organic fertilizer. The dependence of corn stover yield from the corn grain yield with 14% basic moisture content is presented in Fig. 4. In the following calculations, it is considered three scenarios of corn stover harvesting: • minimum—collection of 2.5 t d.m./ha; • average—collection of 3.5 t d.m./ha; • maximum—collection of 5.0 t d.m./ha. The three-pass system set of machinery for the corn residues harvesting with the productivity of 20–35 t/h costs about 262,000 Euro for the minimum scenario, 270,000 Euro for the average scenario, and 279,000 Euro for the maximum scenario. Operating costs of corn stover harvesting in the large square bales are shown in Fig. 5. The graph shows that the operating costs considerably depend on the corn residues mass collected from the field. Upper values are for the harvesting of 2.5 t d. m./ha (3920 t d.m./yr). Lower values are for the harvesting of 5 t d.m./ha (5880 t d. m./yr).

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Operang costs, EUR/t d.m.

Fig. 5 Operating costs of corn residues harvesting in the form of large square bales

35.00 29.39

30.00 25.00 20.00

18.34

19.22

15.00 13.44

10.00 10

14.31 25

20.67

15.76

22.12

24.48 17.22

50 75 Distance of transportaon, km 5 t d.m./ha

23.58

18.67

100

200

2.5 t d.m./ha

Fig. 6 Dependence of operating costs of corn residues harvesting from the distance of transportation

The transportation distance of the corn residues bales transportation from the field to the central storage facility has an effect on the operating costs (Fig. 6). A significant increase in the costs can be detected at the transportation distance of over 100 km. Production costs for the other three corn stover harvesting technologies (in round bales, shredded by a forage harvester and by a forage loader wagon) were assessed for the harvesting of 3.5 t d.m./ha (average scenario). The capital costs of machinery for corn residues supply chains are 127,200 EURO for the SC2 with the productivity of 8–10 t/h, 492,300 EUR for the SC3 with the productivity of 20– 40 t/h and 139,000 EUR for the SC4 with the productivity of 10–20 t/h. The adopted transportation distances are up to 25 km for the round baler and the forage loader systems and 10 km for the forage harvester system. The last one uses the transportation stage directly from the fields to the main storage facility, whereas

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other systems use two-stage transportation with an intermediate local storage near fields with harvested corn. Technological operations of the corn stover supply chain, which produces round bales, are similar to ones for large square bales, but a round baler is less productive. The adopted dimensions of the round bale are 1.5 m in diameter and 1.22 m in width. The shredded corn stover is wrapped with bale net wrap. The average mass of 345 kg of dry matter in the round bale is assumed in calculations. The accepted productivity of the technology is 8–10 t/h. On many farms, corn silage is harvested by self-propelled forage harvesters with high productivity. Farmers, who have such machines, can also use these harvesters for the harvesting of shredded corn stover. In this case, it is necessary to use many tractors with trailers due to the low density of shredded biomass to transport the collected biomass simultaneously with harvesting. The longer the transportation distance, the more tractors and trailers are required. The assumed transportation distance is up to 10 km. The forage loader system uses a tractor with a special trailer, which can pick up shredded corn stover from a windrow, compress the biomass and then transport it to a local or a central storage facility. From the local storage facility near a field, a telehandler or a frontal loader can load the shredded biomass to a high-capacity trailer for road transportation to the main storage. It was estimated the cost of 3.5 t d.m./ha corn residues harvesting (an average scenario) by four technologies using the large square baler, the round baler, the forage harvester and the forage wagon systems. The diagrams with operating costs shares (labor, fuel, materials, repairs, and amortization) for these four corn stover harvesting technologies are shown in Fig. 7. The main costs of the value chains include amortization and fuel. Costs comparison for these corn stover harvesting technologies for the harvesting of 3.5 t d.m./ha with taking into account the transportation distance is presented in Fig. 8. The corn stover harvesting in large square bales with their following transportation at distances longer than 20 km is economically feasible. The forage loader wagon can be used for shorter distances. Results of the feasibility study on corn stover harvesting in the square bales are given in Table 7. The payback period of the projects significantly depends on the mass of corn residues collected from a hectare, which also affects the loading of machinery and logistic efficiency. Thus, in the case of corn stover harvesting with the large square baler, the simple payback period of the project is 6.4 years for the collection of 2.5 t d.m./ha and 3.7 years for 5 t d.m./ha. In the average scenario of the 3.5 t d.m./ha corn residues harvesting, when corn yield is about 7.5 t/ha, the simple payback period is 4.8 years. The initial data about the cob harvesting case, based on the cob harvester Vermeer CCX770 attached to the combine harvester, are taken from the Purdue extension paper ID-417-W [20]. The additional weight of the CCX770 cob harvester affects the combine harvester productivity that is decreased by 10%. This is taken into account in the calculations of operating costs. The corn cobs yield is

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Fig. 7 Corn stover harvesting costs in the mass of 3.5 t d.m./ha with their transportation from the fields to the main storage facilities: a large square baler; b round baler; c forage harvester; d forage loader wagon. Notes *The transportation distance is 25 km. **The transportation distance is 10 km

1.25 t d.m./ha. The distance of cobs transportation is 10 km. The average annual cob harvesting period is 40 days. The results of the techno-economic assessment of three corn stover harvesting systems (with the round baler, the forage harvester and the forage loader wagon) and cobs harvesting are presented in Table 8. From the considered options, the lowest cost of corn residues is 25.2 EUR/t, which corresponds to the forage loader wagon system (SC4 supply chain). When using a round baler (SC2), the cost of corn stover is 29.5 EUR/t; self-propelled forage harvester system (SC3) allows getting a corn stover cost of 28.6 EUR/t, and in the case of cobs harvesting by a cob harvester, the cost of this biomass is 34.9 EUR/t. At the same time, the collected corn cobs can be used without further processing, which contributes to selling cobs at higher price than other corn residues. According to the obtained results, corn stover harvesting in the large square bales is the most economically feasible technology. It allows getting corn stover costs of 22.3 EUR/t d.m. on the central storage facility at a distance of 25 km from the field. The shredded corn residues harvesting with the forage loader wagon is also economically feasible with a simple payback period of 4.6 years and IRR of 26.0%.

Operang costs, EUR/t d.m.

300

G. Geletukha et al. 40.0 35.0 30.0 25.0 20.0 15.0 10.0 10

20

30

40

50

60

70

80

90

100

Transportaon distance of , km Large square baler

Round baler

Forage harvester

Forage loader wagon

Fig. 8 Dependence of operating costs of corn residues harvesting by the four technologies from the transportation distance

Table 7 Techno-economic assessment of corn stover harvesting in large square bales (SC1) Indicators

Scenarios of corn stover harvesting Min Avg Max

Corn residues output (t d.m./ha) 2.5 3.5 5 Productivity of corn stover harvesting (t d.m./yr) 3920 4802 5880 Capital costs of the machinery (thous. EUR) 261.7 269.6 279.3 Operating costs (thous. EUR/yr) 80.5 90.7 103.3 Loan as the share of capital costs (%) 60 Loan rate (%) 7 Corn stover price in the field* (EUR/t d.m) 8.0 Net cost of corn stover bales** (EUR/t d.m) 27.2 24.5 22.3 Sale price of corn stover bales*** (EUR/t d.m. with VAT) 40 Simple payback period (yr) 6.4 4.8 3.7 Discounted payback period (under discount rate of 7%) (yr) 8.7 5.8 4.2 IRR (%) 12.3 22.5 35.1 * The price is determined by the cost of the required amount of mineral fertilizers that is equivalent to replace the nutrients taken away with the corn stover from the field **The cost includes direct costs for harvesting corn residues and deductions for the machinery amortization ***The price is equal to the biomass bales price (with the moisture content of 25%) of 25 EUR/t without VAT

However, further field tests are needed to evaluate the feasibility of this technology under Ukrainian conditions. For the full value chain analysis, it is important to make a techno-economic assessment of corn residues storage. Further corn stover processing into pellets and briquettes will increase the biomass added value.

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Table 8 Techno-economic assessment of different corn residues harvesting technologies Indicators

Harvesting Round baler (SC2)

technology Forage harvester (SC3)

Forage wagon (SC4)

Cob harvester

Output of corn residues (t d.m./ha) 3.5 1.25 Productivity of corn residues (t d.m./yr) 1551 5390 2924 500 Capital costs of the machinery 127.2 492.3 139.0 85.2 (thous. EUR) Operating costs (thous. EUR/yr) 33.0 116.5 55.9 8.9 Loan as the share of capital costs (%) 60 Loan rate (%) 7 Corn stover price in the field* 8.0 – (EUR/t d.m) Net cost of biomass bales** 29.5 28.6 25.2 34.9 (EUR/t d.m) Sale price of corn stover*** or 40*** 70**** cobs****, EUR/t d.m. with VAT*** Simple payback period (yr) 9.4 8.7 4.6 6.7 Discounted payback period (under >10 >10 5.3 8.8 discount rate of 7%) (yr) IRR (%) 1.7 3.3 26.0 12.6 * The price is determined by the cost of the required amount of mineral fertilizers that is equivalent to replace the nutrients taken away with the corn stover from the field **The cost includes direct costs for harvesting corn residues and deductions for the machinery amortization ***The price is equal to the biomass bales price (with the moisture content of 25%) of 25 EUR/t without VAT ****The price is equal to the cobs price (with the moisture content of 20%) of 40 EUR/t without VAT

Corn stover, as well as straw, should be stored for keeping off increase its moisture content due to rains and soaking from the ground, ensuring fire protection and avoiding decay. The place and local conditions are affected on the selection of a storage type. The corn residues can be stored in open storage, tarped storage, permanent structure storage, or anaerobic storage [21]. Many factors should be considered for appropriate storage system selection, including the cost of storage infrastructure, necessary feedstock stability, accessibility of the biomass during the entire storage duration, integration of the storage with a processing plant or energy facility. The biomass storage in permanent structures and buildings offers many advantages in comparison with other systems. However, the permanent storages are economically unfeasible due to the relatively low density of corn stover, including bales, and high capital costs for a new storage building. In the case of existing permanent storages, a stakeholder can use them for corn stover.

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Open-air corn stover storage can be used for temporary local storages when the upper layer of biomass provides coverage of lower layers. Also, in some regions, such an approach can be used for the central storage facility. However, such type of a storage can cause high losses of biomass dry matter. Anaerobic storage or ensiling is a widespread storage method for wet feedstock in the livestock industry. Anaerobic storage remains economically viable for high moisture feedstock, particularly for early season bale storage or emergency storage during extremely wet harvest seasons [21]. The tarped corn stover storage offers the optimal balance of costs and quality preservation. Agro-fiber material can be used as tarp material, which provides snow and rain protection. It gives a possibility of air out on the surface, which prevents mold and fungus formation. These properties of agro-fiber allow its usage for wood chips drying. The period of the agro-fiber use is more than 5 years. The corn stover tarped storage with agro-fiber was chosen for the further cost assessment. The corn stover storage facilities have to comply with the Fire Safety Regulations. For example, in Ukraine, it is the in force Fire Safety Regulations in Agricultural Sector of Ukraine (Order of Ministry of agriculture and Ministry of emergency situation #730/770) [22]. The area of one stack of straw bales must be less than 500 m2, and for shredded bulk straw, it must be less than 300 m2. It is allowed to arrange bales (shredded straw) in double stacks with a distance not less than 6 m between stacks in pair and not less than 30 m between adjacent double stacks. It is important to provide free access to biomass for loaders. The main costs of corn stover storage under tarp include land rent, ground preparation, tarp material, loading/unloading, guarding of the site and dry matter losses of biomass. The costs assessment of corn stover tarped storage for shredded bulk residues, large square bales, and round bales are presented in Table 9. The infrastructure guarding cost is not taken into account due to the assumption that the central corn stover storage facility will be placed near the farm with an existing protection of facilities. Storage costs of large square bales under tarp are 3.1 EUR/t d.m. that is lower than that for round bales (5.0 EUR/t d.m.) and shredded corn stover (6.9 EUR/t d.m.).

3 Technologies for Collection and Energy Utilization of Sunflower Residues (Stalks, Husk) Sunflower is the main oil crop in the world. The main product of sunflower growing is seeds, which reach in fats and contain 30–35% of oil. Kernels of sunflower seeds contain 50–60% of oil [23]. Sunflower oil has a very good taste. Thanks to these properties, a huge amount of sunflower seeds is processed into edible fats. The worst seeds are used for technical purposes. Sunflower has a great fodder value. The sunflower oilseed cake, obtained during oil production, contains 20–35% of proteins. Due to this, it is valuable concentrated feed for animals.

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Table 9 Corn residues storage costs under tarp material Indicators

Shredded form

Large square bales

Round bales

Annual land rent and ground preparation costs of 1 ha (EUR/(ha
year)) Cost of materials for covering one stack of the biomass (EUR/(stack
year)) Area for a double stack with considering the fire protection rules (ha) Corn stover mass in a double stack (t d.m) Dry matter loss (%) Corn stover storage costs (EUR/t d.m) Loading/unloading costs (EUR/t d.m) Total storage costs at the main storage facility (EUR/t d.m)

400 273

427

427

0.31

0.44

0.48

160 9 2.7 4.82 6.9

1103

484

0.6 2.5 3.1

1.4 3.6 5.0

Table 10 Main world sunflower producers (by MY) [8] No

Country/ region

Area (million ha) 2018/ 2019/ 2020/ 2019 2020 2021

Yield (t/ha) 2018/ 2019/ 2019 2020

2020/ 2021

Production (million t) 2018/ 2019/ 2020/ 2019 2020 2021

1 2 3 4 5 6 7 8

Ukraine 6.50 6.40 6.80 2.31 2.58 2.06 15.00 16.50 14.00 Russia 7.94 8.36 8.20 1.60 1.83 1.59 12.71 15.31 13.00 EU 4.02 4.31 4.34 2.37 2.24 2.12 9.51 9.64 9.20 Argentina 1.88 1.53 1.38 2.04 2.11 2.10 3.83 3.24 2.90 China 0.92 1.25 1.25 2.71 2.60 2.64 2.49 3.25 3.30 Turkey 0.72 0.73 0.72 2.52 2.40 2.17 1.80 1.75 1.56 Kazakhstan 0.85 0.82 0.7 1.00 1.13 1.07 0.85 0.92 0.75 USA 0.49 0.51 0.66 1.94 1.75 1.94 0.96 0.89 1.27 World 25.78 26.34 26.55 1.99 2.09 1.86 50.56 54.96 49.46 Notes MY—the marketing year starts on 1st of September and ends on 31th of August. 2019/2020 MY—preliminary data, 2020/2021 MY—forecast (December 2020)

In addition, sunflower has great importance for the energy sector. The sunflower seeds processing generates about 15% of husk, which is mainly processed into solid biofuels (pellets and briquettes) and burned for energy production. By-products of sunflower growing can also be used as energy biomass. The ash generated by sunflower stalks combustion is rich in potassium and other fertile elements. It can be applied as a potassium fertilizer or used as raw material for the production of fertilizers. Since 2012, Ukraine has been a lead sunflower producer in the world. In the 2019/2020 marketing year (MY), the gross harvest of sunflower in Ukraine amounted to 16.5 million tons (Table 10). This is almost 30% of the world’s

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Sunflowewr yield, t/ha

3.0 2.5 2.0 1.5 1.0 0.5 1960

1970

World

1980

EU

1990

2000

Ukraine

2010

2020

China

Fig. 9 Increasing of sunflower yield from 1961 to 2019

sunflower production. Other largest sunflower producers are Russia (15.31 million tons) and the EU (9.64 million tons). It should be noted that the largest sunflower sown area is in Russia (8.36 million hectares in 2019/2020 MY, or 31.7% of the sunflower sown area in the world); however, in 2019, the main EU sunflower producers were Romania (3.6 million tons), Bulgaria (1.9 million tons), Hungary (1.7 million tons) and France (1.3 million tons) [7]. The sunflower yield has increased significantly, which can be seen in Fig. 9 based on the FAO statistical data [24]. From 1961 to 2019, the average global sunflower yield doubled from 1.0 to 2.1 t/ha. In 2019, the average sunflower yield in Ukraine exceeded the EU one. However, the sunflower production potential has not yet been completely used in Ukraine, especially in the Polissya and Forest-Steppe zones [23]. Nowadays, scientists are improving sunflower growing technologies, breeding precocious varieties and hybrids, which will expand the sunflower sown area. In Ukraine, the sunflower area raised more than 3.5 times from 1990 to 2016. The domestic oil and fat complex is developing, and it stimulates demand for sunflower seeds. Ukraine is a world leader in the export of sunflower oil. In 2018, the sunflower oil export achieved 4.1 billion USD or 5.6 Mt of oil [25]. For many years, sunflower was the most profitable crop in the country. According to the data of the State Statistics Service of Ukraine, the profitability of sunflower production by enterprises was 32.5% in 2018, while the profitability of their whole activities was 13.5% [26]. In 2015, the profitability of sunflower production achieved 78.4%. At the same time, the profitability of the whole agricultural activity of enterprises was 30.4%. Sunflower yield depends on favorable climatic and soil conditions for the crop growing, the quality of seed material and agro-technological methods. It is important to provide in time and proper harvesting on the final stage of growing

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crops. The key factor for the beginning of sunflower harvesting is the moisture content of seeds that depends on the ripening phase and weather conditions. The increase in the mass of sunflower seeds and its oil content ends in 35–40 days after mass flowering. The economic maturity comes after the moisture evaporation from sunflower. The sunflower preharvest drying by chemicals (desiccation) in the phase of physiological maturity accelerates ripening and dries the seeds. This operation allows starting harvesting 8–12 days earlier. The optimal harvest time comes when 20–25% of all crops are yellow and yellow–brown, and other plants are dry and brown. At this stage, the moisture content of seeds decreases to 11–13%, heads—to 69–75%, and stalks—to 60–70% [23]. If a farmer has a large sunflower area and a grain dryer, he can start sunflower harvesting at 20–22% seeds moisture content. The sunflower seeds with moisture content less than 7–8% are suitable for long-term storage. The seeds with higher moisture are oxidized, and the oil from them becomes unfit as food. The optimal period of sunflower harvesting is 5–6 days. If sunflower harvesting begins in the phase of full ripeness, the losses from seed falling increase by two times on the fifth day and by 12 times on the 15th day. In Ukraine, the sunflower harvesting period starts in August and finishes in November, the main amount being harvested in September–October [23]. Sunflower is harvested by combine harvesters with special or universal reapers. Farmers can use adapters, special attachments (sunflower attachments) for grain reapers. Reapers can be equipped with a stalk shredder. The use of the shredder will reduce productivity and increase the fuel consumption of the combine harvester and save costs on mulching. Classic reapers are designed for the traditional technology of sunflower cultivation with a row spacing of 70 cm. A reaper should cut sunflower on 20–25 cm below the heads. The combine harvester operating speed is up to 9 km/h for sunflower harvesting. The cut sunflower heads pass through the combine threshing and separating system and are spread on the field. Sunflower stalks remain standing in the field, forming the main part of the sunflower residues, which are available for further harvesting. In existing agricultural practices, sunflower residues are shredded and distributed over the field by specialized agricultural machines. However, some farmers burn sunflower residues on the fields. An alternative to such burning can be the sunflower residues harvesting for energy. Thus, post-harvest sunflower residues include aboveground parts: stalks, heads, leaves, and chaff that is formed during threshing, and underground part—roots. Sunflower reapers are designed to cut the heads with the limited supply of the stalk mass to the combine harvester. The cut stalk mass and heads, after passing through the threshing-separating system, can be collected in a hopper or a trailer. In the 1980s, sunflower was harvested with SK-5 Niva combine harvester with PUN-5 shredder that provided the collection of chaff and heads into trailers for animal feed. This allowed collecting chaff in the mass of up to 0.3–0.5 t/ha [27]. At that, technological maps of sunflower cultivation considered the sunflower yield of 2.5–3.0 t/ha.

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Some farmers adjust the separation of seeds in the combine harvester to increase the ingress of sunflower residues parts into the hopper. Then, seeds are cleaned on stationary grain cleaning machines, and organic waste impurities are separated and can be used as energy biomass in heat generators and boilers. However, the possibility of the use of this technology for the sunflower residues harvesting in significant volumes for the biomass market is limited due to the reducing productivity of the combine harvesters, increasing load on them, increasing consumption of diesel fuel, and rising seed moisture content [23]. At that, the collected biomass has an inhomogeneous composition, and it is contaminated with various impurities that negatively affect its fuel characteristics. Nowadays, the part of sunflower heads and stalk mass is shredded and spread by the combine harvester on the field surface, and it is very difficult to perform the collection of such biomass. Therefore, another option for sunflower residues harvesting, which will allow collecting of larger volumes of biomass from the fields, is the collection of standing stalks. It can be made by using forage harvesters. An important advantage of this approach is the possible drying of stalks in the field that improves fuel characteristics of the collected biomass. The absolutely dry mass of one sunflower plant (height is 170–185 cm, the number of leaves is 28–30) is 250–280 g on the average 265 g. At a density of plants standing at the time of harvesting of 50,000 per hectare, the absolutely dry mass of post-harvest sunflower residues will amount to about 13.0 t/ha [28]. The yield of dry heads is 56–60% of sunflower seeds and 19–20% of the mass of the aboveground part of the plant [29]. In Turkey, the ratio of sunflower stalks yield to seeds is taken as 1.29, and that of heads to seeds is taken as 1.17 [30]. According to other estimates, in addition to seeds, 3–7 tons of dry biomass, of which 10% are heads, can be obtained from a hectare of sunflower [31]. On average, the mass ratio of sunflower residues yield to seeds is taken as 1.9 [32]. Approximate flows of biomass during the sunflower cultivation and processing are given in Fig. 10. The sunflower seeds are processed into oil, which can be used for biodiesel production. The sunflower stalks and heads (without seeds) are fibrous materials with low protein content. This biomass has a variable composition of different fractions of sunflower residues with miscellaneous maturity features [23]. The energy characteristics of sunflower residues, husk and oilcake are presented in Table 11. The fuel characteristics of sunflower stalks and heads are similar. In general, sunflower residues can be used as lignocellulosic feedstock for solid, liquid and gaseous biofuels production. In addition, this biomass can be used for fodder and as a raw material for industry. Threshed sunflower heads contain cellulose (14–17%), protein (5–8%), fat (3.5– 4%), ash elements (potassium, calcium, phosphorus, magnesium—13–15%, nitrogen-free extractives—up to 60%) on the absolute dry weight. Sunflower heads are quite good fodder. Green sunflower heads are stored with the green mass addition (corn, beet tops) in a silo. If sunflower heads have a moisture content of 20–25%, they are stacked with layers of dry straw. The heads can be stored under such conditions for a long time [34].

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1 t of seeds with 7% of moisture content

307

Sunflower growing and harvesting

Stalks, 1400-1700 kg

Processing

Husks, 150-200 kg

Oilcake (meal), 320-450 kg

Heads and chaff, 200-600 kg

Sunflower oil, 350-480 kg

Fig. 10 Mass of sunflower residues and products of oil production per 1 ton of seeds

A sunflower stalk is straight round or ribbed, covered with rough hairs, filled inside with spongy tissue [35]. The bark covers the stalk outside. The stalk volume takes up 90% of the sunflower volume [36]. The bark density is 350 kg/m3; the spongy tissue density is 29 kg/m3. The sunflower stalk with the leaves attached to it dries out during seed ripening. The stalks contain 34–42% cellulose, 19–33% hemicellulose, and 12–30% lignin [37]. Sunflower stalks can be used as fuel, fodder, and fertilizer (Table 12). The ash content of the stalks is 3–13.2%. The comparison of sunflower stalks fuel properties with other crop residues (straw, corn stalks) and wood chips is presented in Table 6. During the sunflower harvesting, the stalks have a high moisture content (60–70%). Such wet biomass should be dried before combustion. The sunflower stalks ash melting temperature is similar to straw one, and it is lower than that of corn stalks and wood chips. For heating equipment selection, it is important to consider this fact. Sunflower stalks contain 0.7–0.8% of chlorine that complicates their combustion, as chlorine compounds cause corrosion of steel elements. The sunflower stalks elemental composition is similar to straw and corn stalks, so they have comparable heating value. As for other crop residues, the moisture content of sunflower residues has the most significant effect on the heating value. The harvesting technology and storage conditions have an influence on the fuel properties of sunflower residues. Harvesting is the initial process of the crop residues supply chains. Two streams of sunflower residues can be allocated: biomass passed through a combine harvester and stalks that are remained to stand in a field. In this case, the sunflower stalks can dry out under favorable weather conditions that will make better the fuel properties of the biomass. In the past, peasants cut sunflower manually for harvest and collected sunflower stalks in bundles, which were further used as fuel for heating. However, there is a lack of up-to-date examples of sunflower residues harvesting.

(NHV) (MJ/kg a.r)

Heating value

(LHV) (MJ/kg d.m)

Moisture (%)

Stalks 14.252 16.190 10.4 Heads 13.824 15.980 11.7 Husk 19.153 20.704 6.7 Dehulled 19.360 21.026 7.1 oilcake Notes: a.r.: means as received by the analyst, value expressed on wet basis d.m.: means dry matter, value expressed on dry basis ST—shrink temperature; DT—deformation temperature

Material

8.3 12.5 3.6 6.6

Ash content (%)

0.13 0.3 0.05 0.12

Cl (%)

0.06 0.16 0.14 0.27

S (%)

44.6 44.3 54.4 51.2

C (%)

7.2 7.3 7.3 7.6

H (%)

0.8 1.4 1.6 5.4

N (%)

920 960 897 925

1100 1130 1002 1155

Ash melting temperature (°C) ST DT

Table 11 Energy characteristics and chemical composition of different components of sunflower residues and by-products of sunflower processing [33]

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Table 12 Main characteristics of sunflower stalks [38] Physicochemical properties Fuel characteristics Higher heating value (HHV) (MJ/kg) Lower heating value (LHV) (MJ/kg) Fixed carbon, (%wt)db Volatile matter, (%wt)db Ash, (%wt)db Moisture, (%wt)am Carbon, (%wt)db Oxygen, (%wt)db Hydrogen, (%wt)db Nitrogen, (%wt)db Sulfur, (%wt)db Fodder characteristics Dry matter, (%wt)am Crude protein, (%wt)db Crude fiber, (%wt)db Neutral detergent fiber (NDF), (%wt)db Acid detergent fiber (ADF), (%wt)db Lignin, (%wt)db Ether extract, (%wt)db Ash, (%wt)db Gross energy, MJ/kg Fertilizer characteristics Nitrogen, (g/kg)db Phosphorus, (g/kg)db Potassium, (g/kg)db Calcium, (g/kg)db Magnesium, (g/kg)db Sulfur, (g/kg)db am as measured; db dry base

Average

Standard deviation

Min.

Max.

Number of samples

18.7

3.34

15.9

26.0

9

17.7

3.29

15.2

24.4

8

8.7 81.0 7.9 9.1 46.0 37.6 5.4 1.2 0.1

6.59 6.03 3.6 5.82 7.07 5.39 0.74 0.69 0.07

1.2 72.7 3.0 2.3 35.1 26.8 4.8 0.3 0.0

14.4 85.9 13.2 18.0 60.3 47.5 7.1 2.6 0.2

4 4 18 5 10 10 10 11 8

88.9 7.3 48.8 71.7

5.08 4.49 n.a 16.82

82.0 1.5 48.8 43.2

94.0 16.3 48.8 89.5

4 12 1 6

37.2

10.17

22.1

51.0

6

16.1 1.0 7.9 18.8

5.85 0.79 3.64 3.57

7.3 0.5 3.0 15.9

26.5 2.0 13.2 26.0

7 3 18 8

11.1 0.9 27.5 8.1 1.1 1.2

5.53 0.73 22.50 4.80 0.27 0.79

3.1 0.1 8.0 1.6 0.9 0.1

20.0 2.3 67.8 13.7 1.5 2.5

10 7 7 7 6 8

Sunflower stalks can be cut and shredded by a forage harvester. After passing through the combine, the shredded biomass is collected in the trailer. The sunflower residues need drying if their moisture content is more than 25%. An alternative option is to use the multipass corn stover harvesting technology or supply chains of shredded corn residues harvesting.

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Residues yield, t d.m./ha

6.0

Heads Stover mass

5.0 4.0 3.0 2.0 1.0 0.0 15

20

25

30 35 Sunflower yield, m.c./ha

40

45

50

Fig. 11 Sunflower residues yield in dry tons per hectare

Assessment of harvesting technologies will be carried out for yields from 1.5 to 5.0 t/ha. The graph of the yield of sunflower heads and stover mass is given in Fig. 11. Partly this biomass can be harvested for energy purposes. In the feasibility study of sunflower stalks harvesting under Ukrainian conditions, it is evaluated the supply chain with a self-propelled forage harvester, equipped with a reaper for harvesting coarse-stemmed crops [23]. The shredded biomass is collected in a trailer that moves nearby the forage harvester. For transporting of biomass simultaneously with the residues harvesting, it is necessary to use many tractors with trailers. The accepted transport distance is up to 10 km. Due to the lack of the described practical examples of sunflower residues harvesting by forage harvesters, the assessment is based on the corn stover harvesting experience, taking into account the sunflower properties. Initial conditions are: the harvesting period is 30 days; the daily working time is 8 h/day; deductions for maintenance and repair is 5%; amortization is 10 years; the operator salary is 20.6 euros/day; the sunflower yield is 1.5 t/ha for the minimum scenario, 2.5 t/ha for the average scenario; and 5 t/ha for the maximum scenario; the mass of harvested stalks for these scenarios are 1.6 t d.m./ha, 2.1 t d.m./ha and 3.0 t d.m./ha, respectively. The machinery cost is presented in Table 13. The conditional cost is the part of the actual cost of machinery that depends on the duration of their direct use for the sunflower stalks harvest during a year. The results of the operating cost estimation for the three scenarios of sunflower stalks harvesting are given in Fig. 12. The main component of costs is amortization. The results of the feasibility assessment of the supply chain with a self-propelled forage harvester are presented in Table 14. The simple payback period of the sunflower stalks harvesting system is 4.8 years for the maximum scenario (3 t d.m./ha),

50

51,9

4

4

20

125

50

1 1

320

100

100

200

120 120

Min 1.6 t d.m./ha Quantity Conditional cost, 1000 EUR

4

240 240

1. Collection Forage harvester Claas Jaguar 850 2. Transportation to storage facility Tractor Claas Axion 850 Trailer Kobzarenko TZP-39 Total

Use of equipment, % of the annual usage

177

Unit price, 1000 EUR

Process/machinery

5

5

5

1 1

370

125

125

250

120 120

Average 2.1 t d.m./ha Quantity Conditional cost, 1000 EUR

Table 13 Cost of the machinery for the harvesting of sunflower residues with a forage harvester

6

6

6

1 1

420

150

150

300

120 120

Max 3.0 t d.m./ha Quantity Conditional cost, 1000 EUR

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Cost of sunflowwer stalks, EUR/т d.m.

40 35 30 25 20 15 10 5 0 Min

Avg

Labor

Fuel

Amorzaon

Max

Repairs

Fig. 12 Costs of sunflower stalks harvesting by a forage harvester

Table 14 Techno-economic assessment of harvesting sunflower residues with a forage harvester Indicators

Sunflower residues yield 1.6 2.1 3.0 t d.m./ha t d.m./ha t d.m./ha

Productivity of sunflower residues harvesting (t d.m./yr) 1867 2559 Capital costs of the machinery (thous. EUR) 320 370 Operating costs (thous. EUR/yr) 38.5 45.7 Loan as the share of capital costs (%) 60 Loan rate (%) 7 Net cost of sunflower residues* (EUR/t d.m) 37.7 32.3 Sale price of sunflower residues ** (EUR/t d.m. with VAT) 45 Simple payback period (yr) 8.2 6.4 Discounted payback period (under discount rate of 7%) (yr) >10 8.6 IRR (%) 5.0 12.2 * The cost includes direct costs for harvesting biomass and deductions for the amortization **The price is equal to the sale price of sunflower residues (with the moisture content 33.8 EUR/t without VAT

3616 420 55.3

26.9 4.8 5.7 22.9 machinery of 25%) of

6.4 years for the average scenario (2.1 t d.m./ha), and 8.2 years for the minimum scenario (1.6 t d.m./ha). In addition, it was assessed the sunflower chaff harvesting technology based on the use of a trailer behind a combine harvester SK-5 Niva with a shredder PSP-1.5 [27]. In Ukraine, this system was used at the end of the last century. Initial data: harvesting period is 30 days; the daily working time is 8 h/day; deductions for maintenance and repair is 5%; amortization is 10 years; the operator salary is 20.6 euros/day; the collected chaff mass is 0.5 t d.m./ha; an annual mass of harvested biomass is 181 t d.m./season. The list of additional machinery for sunflower

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residues harvesting includes the used trailers 2PTS-4-887A, the shredder PSP-1.5, and the new tractor MTZ-82. The operating costs of sunflower chaff harvesting without machinery amortization is 15.9 EUR/t d.m. (11.1 EUR/t d.m). The simple payback period of the project is 2.3 years, in case of the harvested biomass sale at a price of 35 EUR/t d.m. without VAT, and 1.7 years at the sale price of 45 EUR/t d. m. without VAT. At present, modern commercial combine harvesters provide spreading of crop residues on a field surface or windrowing them. Only a few individual models can be equipped with a stacker, while a trailer unit for the harvesting of sunflower chaff and heads is not used. The Kherson Machine-Building Plant used to produce combines and reapers, which allowed crop residues harvesting into trailers simultaneously with grain harvesting. The technology systems of sunflower residues windrowing with following baling or harvesting in shredded form require field tests. The collected biomass can be delivered by different transport, but it is necessary to use vehicles with high-capacity trailers due to the low density of shredded sunflower residues. For organizing the sunflower residues storage, it can be used approaches similar to the corn stover storing that provide conditions to prevent the affecting of precipitation and moisture from the ground on the biomass, avoiding its rot and providing the necessary fire protection. Dry biomass can be stored under a tarp or in indoor warehouses, and wet biomass is ensiled or preserved under anaerobic conditions. In contrast to the significant use of sunflower husk for heat and energy generation and briquettes or pellets production, the examples of sunflower residues processing into solid biofuels are still quite rare. Sunflower residues are mainly used in small quantities to supply agricultural producers and rural households with heat. Sunflower is not cultivated widely in many countries, but in some countries this crop has significant potential for energy. Some stakeholders have already tested technologies for processing sunflower residues into solid biofuels. Fuel briquettes from a mixture of sunflower parts are included in the register of alternative fuels of the State Agency on Energy Efficiency and Energy Saving of Ukraine in 2018. Due to the fuel characteristics of sunflower residues, it is necessary to use specialized boilers for the combustion of solid biofuels based on this biomass. Therefore, it is important that the equipment manufacturer confirms the possibility of sunflower residues use as fuel. In Ukraine, projects for the production of energy from sunflower stalks are carried out by Kotloturboprom LLC of the MAST-IPRA Corporation [23]. In addition, heat generators and burners of grain dryers for the combustion of the stalks and other sunflower residues are available on the market. The experiment results [39] of sunflower stalks burning on different grates are presented in Table 15. The boiler has grates with three different types of holes: circular, oblong, and mixed (circular with oblong). The air supply was provided by front natural draft, lower natural draft, and a lower blow fan. Air supply under grate allows reducing emissions from the sunflower stalks combustion. High CO emissions are related to the specific conditions of the experiment. The rational

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Table 15 Averaged results of the flue gas measurement at sunflower stalks combustion on three different grates [39] Circle holed grate Parameters

1F FB

TCG (°C) 148.0 VCG (m/s) 3.4 555.6 QN CG (nm3/h) 16.7 O2 (%) 3.8 CO2 (%) 1.84 k (13% O2) 5060.8 CON (mg/nm3) 0 SO2 N (mg/nm3) 442.8 NOx N (mg/nm3) Oblong holed grate Parameters 1F 1F FB BB

1F BB

2F FB

2F BB

2F *BB

3F *BB

77.2 1.7 327.4 13.6 6.6 1.08 9119.0 21.5 213.6

72.8 2.6 512.3 18.0 2.7 2.64 12,738.7 119.8 313.6

89.8 1.5 290.8 11.8 8.1 0.87 10,572.1 0 167.1

96.4 2.0 366.2 12.1 7.8 0.90 7575.8 0 110.3

94.4 1.9 362.1 11.7 8.1 0.86 5525.2 0 137.9

TCG (°C) 133.9 152.2 VCG (m/s) 3.9 3.5 650.9 558.2 QN CG (nm3/ h) 16.5 13.7 O2 (%) 3.9 6.4 CO2 (%) 1.76 1.10 k (13% O2) 4570.2 2953.9 CON (mg/ nm3) 0 15.6 SO2 N (mg/ nm3) 346.2 271.5 NOx N (mg/ nm3) Mixed (circle + oblong) holed grate Parameters 1F FB

2F FB

2F BB

2F *BB

3F BB

3F *BB

88.5 2.4 460.5

135.9 2.8 471.1

176.8 3.1 474.2

149.7 3.2 520.9

142.8 3.7 612.2

18.3 2.4 2.99 10,808.8

13.0 7.1 0.99 1765.5

14.1 6.0 1.16 1626.3

13.8 6.4 1.11 2851.7

13.9 6.2 1.13 3414.7

0

23.5

0

0

0

197.6

193.8

403.9

276.0

333.8

2F BB

2F *BB

3F BB

3F *BB

TCG (°C) 149.1 116.0 121.8 130.2 167.5 VCG (m/s) 3.2 2.8 3.1 2.9 3.2 521.6 486.4 531.5 486.3 499.8 QN CG (nm3/h) 13.0 13.1 14.3 13.9 14.4 O2 (%) 7.0 7.0 5.9 6.3 5.9 CO2 (%) 1.0 1.01 1.19 1.12 1.20 k (13% O2) 2834.8 2181.5 2920.0 1706.3 4223.8 CO N (mg/nm3) 0 0 18.6 3.4 0 SO2 N (mg/nm3) 190.0 117.2 172.3 246.8 305.2 NOx N (mg/nm 3) Notes: 1F—sunflower stalks as it was harvested from the field, 2F—chopped stalks without compression, 3F—chopped and compressed stalks in polyethylene bags; FB—front burning, BB— natural draft burning, *BB—fan blowing burning

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organization of combustion and regulation of air supply in industrial boilers provide CO emissions within the permissible limit. Boilers can be equipped with flue gas cleaning systems to meet the requirements for the maximum permitted emissions from the combustion of sunflower residues. During harvesting, sunflower residues can have a high moisture content, which causes difficulties for storage of the biomass and need for its drying for processing into solid biofuels. However, biogas can be produced from such wet biomass. However, due to the high content of lignocellulosic compounds in sunflower residues, it is necessary to pretreat the biomass with mechanical, physical, or chemical destruction before the anaerobic fermentation. The achieved biochemical methane potential of untreated sunflower heads was 210 ± 1.97 ml of CH4/g volatile solids (VS), and 127.98 ± 5.19 ml CH4/g VS for untreated stalks [40]. Sunflower heads are considered a better feedstock for biogas production than sunflower stalks. After alkali pretreatment, it was achieved the methane yield from the sunflower heads of 268.35 ± 0.11 ml of CH4/g VS, while the methane yield from the pretreated sunflower stalks was 168.17 ± 6.87 ml of CH4/g VS. According to the experimental data, the content of VS was 79.9 ± 0.5% of dry weight in sunflower heads and 87.7 ± 0.1% of dry weight in sunflower stalks. Thus, up to 214 m3 of methane can be obtained from 1 t d.m. of sunflower heads and up to 154 m3 from 1 t d.m. of sunflower stalks. In addition, some farmers grow sunflower for silage and green fodder. For comparison: the methane yield from sunflower silage is 298 nm3/t [41]. The methane yield from different crops is given in Table 16. The different pretreatment methods of sunflower stalks before the anaerobic fermentation were analyzed in the studies [43, 44]. The highest methane yield (259 ± 6 ml CH4/g VS) was achieved after alkali pretreatment of sunflower stalks with 4% NaOH at a temperature of 55 °C for 24 h. Thus, alkali pretreatment of sunflower residues before the anaerobic fermentation, as well as alkali pretreatment of other lignocellulosic substrates, increases methane yield. If sunflower residues are used as a raw material for bioethanol production, it is necessary to provide pretreatment of the biomass to destroy its lignocellulosic structure. This provides the access of enzymes to the cellulose chains easier or directs the use of their lignocellulosic fractions [45]. It can be obtained 1 l of ethanol from 3.8 kg of pretreated sunflower stalks if the pre-treatment was made by steam and simultaneous saccharification and fermentation. In this case, 101.4 L of bioethanol can be produced from 1 ton of raw sunflower stalks [46]. Prehydrolysis at the temperature of 180–230 °C with simultaneous saccharification and fermentation makes it possible to obtain 12 g of bioethanol/100 g of sunflower stalks (150 l/t), which is equivalent to 72.2% of the theoretical yield [47]. The theoretical yield of bioethanol from different biomass is presented in Table 17. In the study [45], four sunflower accessions were cultivated and harvested in the semi-arid region of northeastern Brazil for the estimation of the potential of further processing the sunflower seeds into biodiesel and the sunflower stalks with heads into bioethanol. The yield of sunflower seeds was 1635 kg d.m./ha, and the yield of sunflower residues was 2537 kg d.m./ha. The seeds and residues could be

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Table 16 Methane yield from different crops [42]

Crop

Methane yield (m3/VS)

Sunflower Oilseed rape Maize (whole crop) Straw Grass Clover grass Leaves Potatoes Fodder beet Sugar beet

154–400 240–340 205–450 242–324 298–467 290–390 417–453 275–400 420–500 236–381

Table 17 Bioethanol yield from different raw materials [48]

Raw materials

Potential ethanol yield (l/t d.m)

Corn grain Corn stover Rice straw Forest thinning Hardwood sawdust

470 428 416 309 382

processed, respectively, into 663 kg/ha of oil and 1115 kg/ha of sugars (871 kg/ha of cellulose and 244 kg/ha of hemicellulose). From this mass of sunflower residues, it is possible to produce 293 l of bioethanol/ha.

4 Energy and Ecological Life-Cycle Analysis of Corn By-Products Energy Usage 4.1

Methodology for Assessing Energy and Environmental Efficiency of Bioenergy Technologies

An objective comparison of the energy efficiency of the implementation of different technologies for energy production from biomass should be carried out according to the methodology of life-cycle assessment [49] and with the calculation of the balance between total primary energy consumption during product production and total energy production as a final product. The methodology for assessing energy efficiency, based on the use of cumulative energy demand (CED, CEDNR) and energy yield coefficient (EYC, EYCNR), is described in detail in [50]. The values of before-mentioned coefficients calculated using the life-cycle assessment methodology for the production of thermal energy from maize crop residues will be compared with the following values: according to the recommendations of the

Technologies for Energy Production …

12

317

International Energy Agency, in order to achieve sustainable bioenergy development in the future EYCNR should be more than 2, market value—more than 5. Directive 2018/2001/EC of the European Parliament and of the Council [51] on the promotion of the use of energy from renewable sources contains a methodology for calculating the greenhouse gas balance of fuels derived from biomass used for the production of heat and electricity and cooling. According to the proposed methodology, greenhouse gas emissions are considered for such single processes as planting, harvesting, preliminary preparation, and transportation of biomass. Emissions from direct changes in land use in the event of such changes after 2008 are also taken into account. The balance does not include emissions from the combustion of biomass as a fuel and any emissions related to indirect effects. Unlike liquid biofuels, the method of calculating GHG emissions for biomass and biogas also includes the final stage of their conversion into heat and/or electricity. Greenhouse gas emissions from the production of solid and gaseous biomass before its conversion into thermal energy are calculated by the following formula: E ¼ eec þ e1 þ ep þ etd þ eU  esca  eccs  eccr ; gCO2eg /Tbiomass ;

ð1Þ

where E eec e1 ep etd eU esca eccs eccr

total emissions from the use of the fuel; emissions from the extraction or cultivation of raw materials; annualized emissions from carbon stock changes caused by land-use change; emissions from processing; emissions from transport and distribution; emissions from the fuel in use; emission savings from soil carbon accumulation via improved agricultural management; emission savings from CO2 capture and geological storage; emission savings from CO2 capture and replacement.

Emissions from the manufacture of machinery and equipment shall not be taken into account. Greenhouse gas emissions from the use of biofuels for thermal energy production, including the energy conversion stage, are calculated according to the following dependence: ECh ¼ E=gh

ð2Þ

where ECh total greenhouse gas emissions during thermal energy production as a final product, gCO2eq./MJ; ηh the heat efficiency, defined as the annual useful heat output divided by the annual bioliquid input based on its energy content. Greenhouse gas emissions savings from heat being generated from bioliquid:

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 SAVING ¼ ECFðhÞ  ECh /ECFðhÞ ; %

ð3Þ

where EC(h) total emissions from the heat production; ECF(h) total emissions from the fossil fuel comparator for useful heat. Wastes and residues, including treetops and branches, straw, husks, cobs and nut shells, and residues from processing, including crude glycerin (glycerin that is not refined) and bagasse, shall be considered to have zero life-cycle greenhouse gas emissions up to the process of collection. According to recommendations contained in the Directive 2018/2001/EC, during the production of thermal energy from biofuels, greenhouse gas emissions should be compared with the following emissions from fossil fuel systems: ECF (h) = 80 gCO2eq/MJ heat. For biofuels used for thermal energy production, where direct physical replacement of coal can be demonstrated, for calculation purposes, the ECF(h) shall be 124 CO2eq/MJ heat. A similar coefficient in the production of thermal energy for the conditions of Ukraine is not found in official documents. The directive states that the value of the ECF(h) indicator at the level of 80 g CO2eq/MJ heat takes into account that most of the thermal energy in the European Union by 2020 is produced from natural gas, which is also identical for Ukraine. Therefore, in this paper, the value of greenhouse gas emissions when using biomass for thermal energy production will be compared with this value. Bioenergy technology can be considered environmentally friendly if its implementation reduces greenhouse gas emissions compared to the use of fossil fuels. According to the new requirements of the Directive to promote the use of RES, the reduction of greenhouse gas emissions from the use of biofuels for electricity, heat and cooling must be at least 70% for installations starting from January 1, 2021 to December 31, 2025 and 80% for installations, which will start operating on January 1, 2026.

4.2

Energy Analysis of the Use of Corn Residues in Bales, Pellets and Briquettes for Thermal Energy Production

Energy and environmental analysis of the use of maize by-products was performed for three-pass systems based on a baler of large rectangular bales: combine harvester + tractor with stalk-shredding windrower + tractor with baler of large rectangular bales. Harvesting of corn by-products from the field should take place immediately after the main harvest, so as not to interfere with the main crop rotation activities. According to typical crop rotations, waste collection from fields can take no more than 14 days. Then the by-products are transported to the main warehouse (the entire annual volume of harvest is stored), and then (in the pre-heating and heating season)—to the boiler room warehouse.

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Fig. 13 Life-cycle diagram of the use of maize by-products a in bales and b in pellets/briquettes for heat production

The life cycle of the use of corn by-products in a form of bales, pellets/briquettes as a fuel for thermal energy production is presented in Fig. 13. Annual primary energy consumption during feedstock cycles (Efd) of corn by-products use in the form of bales, granules/briquettes is described by systems of mathematical relations (4 and 5), where each of the system equations is responsible for one of the elementary flows or operations occurring during biomass preparation for use for energy purposes. Thus, for crop residues in the form of energy bales, the annual consumption of primary energy is:

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8 n P > > E ¼ Ei > fd > > i¼1 > > > > Ewd ¼ 1; 25
B
bwd
QH > p > > H > E ¼ 1; 25
B
b
Q ; > bl bl p > > > > Ecol ¼ 1; 25
B
bcol
QH > p; > < Eid1 ¼ 1; 25
B
bld1
QH p; > E ¼ B
E
n ; tr1 t
km1 1 > > > > Est1 ¼ B
ea:f: ; > > > > Etr2 ¼ B
Et
km2
n2 ; > > > > Eid2 ¼ 2; 5
B
bld2
QH > p; > > > 16;8
B
e st:cov: > Est2 ¼ ; > > s : Ech ¼ 3
ech
B.

ð4Þ

where Ewd, Ebl, Ecol, Eld1, Etr1, Est1, Eтp2, Eld2, Esy2, Ech—primary energy consumption when: windrowing corn residues in the field; residues baling; when collecting bales from the field; their loading on the vehicle; transportation of bales to the central warehouse; storage of bales in the central warehouse under agro-fiber; transportation of bales to the consumer; bale loading operations at the central warehouse and boiler house warehouse; storage of a weekly stock of bales in the boiler house warehouse; chipping of bales before feeding into the boiler, GJ/year; B —annual fuel consumption by the boiler house, t/year. bwd, bbl, bcl, bld—specific fuel consumption of equipment used for windrowing, baling, collection, and loading of raw materials, l/t; Qнp—net calorific value of diesel fuel, MJ/l; n1—distance of bale transportation from the place of their production to the central warehouse, km; n2—from the central warehouse to the boiler house, km; s—load of the boiler house, hr/year; Et⋅km—energy capacity of transportation work, MJ/t⋅km; ea.f.—specific consumption of primary energy in the production of agro-fiber, MJ/t; est.cov.—specific consumption of primary energy during the building of the warehouse: energy consumption of metal and concrete structures, fuel and electricity consumption during construction, MJ/t; ech—specific electricity consumption during chipping of bales, MJ/t. For corn residues in the form of pellets or briquettes, the annual consumption of primary energy during the feedstock cycle is:

12

Technologies for Energy Production …

8 n P > > Efd ¼ Ei ; > > > i¼1 > p > > > Ewd ¼ 1; 5
Bpl=br
bwd
QH ; > p > > Ebl ¼ 1; 5
Bpl=br
bbl
QH ; > > > > Ecol ¼ 1; 5
Bpl=br
bcol
QH > p; > > p < E ¼ 1; 5
B
b
Q ld1 ld1 pl=br H; E ¼ B
E
n ; tr1 t
km1 1 pl=br > > > > E ¼ 1; 2
B
e ; st1 a:B: pl=br > > > H > E ¼ 3
B
b
Q ld2 id2 > pl=br p; > > > E ¼ 3
B
e ; > pl=br pl=br pl=br > > > > Etr2 ¼ Bpl=br
Et
km2
n2 ; > > : 72
Bpl=br
est2 Est2 ¼ ; s

321

ð5Þ

where Bpl/br—annual consumption of pellets/briquettes by the boiler, t/year; n1— distance of transportation of bales from the place of their collection to the place of granulation/briquetting, km; n2—distance of biofuel transportation to the consumer, km; est2—specific consumption of primary energy during the construction of the hopper for pellets/briquette warehouse (storage of monthly stock of pellets/ briquettes, service life of the facility 10 years), MJ/tpl/br; epl/br—specific costs of primary non-renewable energy for granulation/briquetting (electricity consumption in process equipment), MJpr/tpl/br. The total primary energy consumption in the conversion subsystem is determined by the dependence: Econ: ¼ Eeq: /keq: þ Eexp: þ Eel: ; ½GJ/year

ð6Þ

where Eeq.—primary energy consumption during the equipment production, installation and dismantling, GJ; keq.—estimated period of the equipment operation, years; Eexp.—primary energy consumption for repair and maintenance of boiler equipment, GJ/year; Eel.—own electricity consumption, GJ/year. 8 CEDNR ¼ Efd þ Econ: ; > > n > P > > > Efd ¼ B
Ei ; > > > i¼0 > > < Econ: ¼ P Eexp : þ Eel: þ keq þ Eeq ; CEP ¼ Wi
si ; > > CEDNR ; > > ced ¼ NR > CEP > > > CEP > EYC > NR ¼ CED ; > NR : cedNR \0; 2; EYCNR [ 5:

ð7Þ

Calculation and methodological model for determining energy efficiency taking into account the criteria of sustainable development is represented by a set of relations (7). Based on the obtained methodological model and using a set of Eqs. (4 and 5), a study of energy efficiency for thermal energy production in a boiler with

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a capacity of 500 kW using bales, pellets, and briquettes from corn residues have been performed. The obtained values of energy yield coefficient (non-renewable) (Table 18) at a distance of transportation of final biofuel up to 150 km correspond to the recommended range of values and are in the range of 4.62–12.71. It should be noted that compared to the use of corn residues in bales, the energy performance for pellets and briquettes is lower. The decrease is explained by high primary energy consumption during granulation/briquetting—55% of all primary energy consumption (when transporting biofuels over a distance of 50 km) (Fig. 14). However, compared to pellet production, the energy efficiency of briquettes is better, due to lower initial energy consumption for briquetting compared to granulation, and lower energy consumption for the boiler plant’s own needs (fuel is loaded manually). As it is shown in Fig. 14, the largest consumption of primary energy of fossil fuels occurs at the stages of procurement, pretreatment of raw materials and transportation of finished fuel. In addition, an important component is the production of energy in the boiler. Energy consumptions share during the manufacture, dismantling, maintenance and repair of the boiler plant are 2–4% of the total consumption of primary energy of fossil fuels during the product life cycle. As can be seen from Fig. 15, briquettes always have worse values of specific cumulative energy demand within their recommended values compared to bales, but slightly better values compared to pellets. At a distance of more than 500 km, briquettes are better than bales in terms of energy efficiency if their use for thermal energy production. Compared to pellets, briquettes always have better energy efficiency, both within acceptable and recommended values.

4.3

Ecological Analysis of the Use of Corn By-Products in Bales, Pellets, and Briquettes for Thermal Energy Production

The calculation of GHG emission reductions is performed in accordance with the recommendations provided in the Directive of the European Parliament and of the Council 2018/2001/EC to promote the use of renewable energy sources, taking into account the life cycle of thermal energy production from solid biofuels. GHG emissions from solid biomass production before its conversion into thermal energy (e) for different types of solid biofuels considered in the paper are: For bales from corn by-products: e ¼ Ke:d:
QpH
ðbwd þ bbl þ bcol þ bld1 þ btr1 þ bld2 þ btr2 Þ þ Ke:el:
ðbch þ bbl Þ; gCO2eq /t

ð8Þ

where bwd ; bbl ; bcol ; btr1 ; bld1 ; btr2 ; bld2 —consumption of diesel fuel by the equipment which carries out windrowing, baling, collecting, transportation and loading

CED, GJ/year ced EYC = 1/ced CEDNR, GJ/year cedNR EYCNR = 1/cedNR

Bales from corn by-products

Energy performance indicators

6810 1.33 0.75 402 0.08 12.71

6838 1.34 0.75 430 0.08 11.89

6948 1.36 0.74 540 0.11 9.47

7086 1.39 0.72 678 0.13 7.54

Transportation distance (km) 0 10 50 100 7224 1.41 0.71 816 0.16 5.36

150 7732 1.51 0.66 790 0.16 6.47

7753 1.52 0.66 811 0.16 6.30

7838 1.53 0.65 896 0.18 5.71

7943 1.55 0.64 1002 0.20 5.11

8049 1.57 0.64 1107 0.22 4.62

0 10 50 100 150 Pellets from corn by-products

Table 18 Energy efficiency of the life cycle of thermal energy production from corn by-products

7821 1.53 0.65 716 0.14 7.14

7842 1.53 0.65 737 0.14 6.94

7927 1.55 0.65 822 0.16 6.22

8138 1.57 0.64 927 0.18 5.51

8244 1.59 0.63 1033 0.20 4.95

0 10 50 100 150 Briquettes from corn by-products

12 Technologies for Energy Production … 323

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a

b) pellets from corn by-

c) briquettes from corn by-

1 --- feedstock gathering; 2 ---

products

products

bales chipping; 3 --- biofuel

1 --- feedstock gathering; 2 ---

1 --- feedstock gathering; 2 --

storage; 4 --- manufacture,

bales and pellets

bales and briquettes

dismantling, maintenance,

transportation; 3 ---storage

transportation; 3 --- storage /

repair of the boiler installation; 5

/loading operations; 4 ---

loading operations; 4 --thermal energy production; 5

--- bales transportation; 6 ---

thermal energy production; 5 ---

thermal energy production; 7 ---

pelletizing; 6 --- manufacture,

--- briquetting; 6 ---

loading operations

dismantling, maintenance,

manufacture, dismantling,

repair of the boiler installation

Fig. 14 Distribution of primary energy consumption (non-renewable) (CEDNR) by stages of the life cycle of thermal energy production from corn residues

Fig. 15 Dependence of cednr on transportation distance of corn by-products in a form of bales, pellets, and briquettes

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of crop residues, l/t; QpH —net calorific value of diesel fuel, MJ/l; Ke.d.—greenhouse gas emission factor when using diesel fuel: 74.1 t/TJ; Ke.el.—specific emissions of carbon dioxide when using electricity: 1.227 kg CO2-eq./kW
hr; bch, bbl—electricity consumption by bale shredder and boiler plant, kW
hr/t. For pellets/briquettes from corn by-products: e ¼ K
e:d:
QpH
ðbwd þ bbl þ bcol þ btr1 þ bld þ btr2 Þ þ Ke:el:
bbl þ bpl=br ; gCO2eq /tbm

ð9Þ

where bpl=br —specific electricity consumption for granulation/briquetting, kWh/tpl/br. Reduction of GHG emissions from thermal energy production from biomass is expressed as a percentage compared to total GHG emissions from the use of fossil fuels for thermal energy production, which, according to the recommendations of the European Commission, is accepted at the level of 80 gCO2-eq./MJproduced. Based on the analysis of the ratios (1–3, 8–9) and taking into account the entire life cycle of thermal energy production, a calculation and methodological model for estimating the potential for reducing greenhouse gas emissions has been developed: P P 8 e ¼ Ke:d:
Edies: þ Ke:el:
Eel: ; > > < ECh ¼ e
QB1 ; Fh ECh > De ¼ ECEC ; > : Fh De [ 70%

ð10Þ

Figure 16 shows a comparison of specific greenhouse gas emissions during the production of thermal energy from corn residues in the form of large bales, pellets, and briquettes. It can be seen that at the stage of transportation of granular and briquetted biomass, slightly lower greenhouse gas emissions occur compared to the transportation of bales. However, the additional stage of granulation and briquetting, during which electricity is consumed, leads to a significant increase in specific greenhouse gas emissions during the life cycle of the use of corn residues for energy production. The production of thermal energy from solid biofuels in a boiler with a capacity of 500 kW provides a significant reduction in greenhouse gas emissions when using biofuels from corn residues: by 83–91% in the form of bales; by 73–79% in a form of granules; by 75–81% in a form of briquettes depending on the transportation distance of biofuels (Table 19). Reduction of greenhouse gas emissions when using corn residues in the form of pellets is slightly lower compared to the use of bales, due to additional emissions at the stage of granulation. However, their value fully satisfies the sustainability requirements considered in this paper. The reduction of greenhouse gas emissions when using corn residues in the form of briquettes is slightly lower compared to the use of bales, and higher than in the case of production and use of pellets.

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Fig. 16 Specific greenhouse gas emissions during the life cycle of corn by-products usage for thermal energy production

Table 19 Reduction of greenhouse gas emissions during the production of thermal energy from corn residues

Biofuel type

GHG emissions reduction (%) Transportation distance (km) 0 50 100

150

Bales Pellets Briquettes

90.95 79.32 81.00

82.92 73.37 74.91

88.27 77.34 78.97

85.60 75.36 76.94

5 Roadmap for Bioenergy Development in Ukraine Until 2050 5.1

Goal, Time frame, and Benchmarks of the Roadmap

The goal of the roadmap is to present a realistic long-term scenario for the development of bioenergy, which corresponds to Ukraine’s transition to 100% RES in 2070. The proposed roadmap covers the period of 2020–2050 and has several benchmarks. One of them is the year 2030 as the new NREAP is to be developed until 2030, in which at least 8 Mtoe of biomass, biofuels and waste should be consumed according to the current Ukraine’s Energy Strategy. The second benchmark takes into account the goal of bioenergy development determined by the Energy Strategy of Ukraine for 2035—11 Mtoe of biomass, biofuels, and waste in the total primary energy supply. The roadmap is in line with the scenario of achieving over 60% of RES in the energy balance of Ukraine in 2050 (Fig. 17), including the individual sectors: power production—70% of RES (Fig. 18); heat production—65% of RES (Fig. 19); transport—35% of RES (Fig. 20). In Fig. 17, the value for 2018 is

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70%

63%

60% 48%

50% 35%

40% 25%

30% 20% 10%

4.6%

9%

13%

18%

0% 2018

2020

2025

2030

2035

2040

2045

2050

Fig. 17 Forecasted share of RES in Ukraine’s total primary energy supply until 2050

according to Ukraine’s Energy Balance for 2018, and the value for 2035 is according to the Energy Strategy of Ukraine until 2035. The realization of these goals is possible under the condition of reducing TPES in 2050 compared to 2018 (93.2 Mtoe) by 9% (up to 85 Mtoe). Regarding the production of heat from RES, it should be noted that up to 85– 90% of the total amount is provided by biomass now. According to the forecast of the Bioenergy Association of Ukraine, in the future, the biggest share of heat production from RES will also fall to biomass. Taking this into account, the roadmap for the development of Ukraine’s bioenergy until 2050 provides for high biomass shares of all RES in heat production (Fig. 21). According to the dynamics of changes in TPES and its structure assumed in the roadmap, this corresponds to the share of biomass in the total heat production in 2050—44% (Fig. 22). Assumed in the roadmap biomass shares of all RES in electricity production, in transport sector and obtained respective contribution of biomass to the total electricity production and total consumption of energy in transport sector until 2050 are presented in Figs. 23, 24, 25, and 26. Based on the predicted bioenergy development in the heat, electricity and transport sectors, we have obtained data on the possible contribution of biomass/ biofuels to renewable energy production and to the total primary energy supply in Ukraine by 2050: 38% and 24% in 2050, respectively (Figs. 27, and 28).

5.2

Biomass Potential in Ukraine and Its Estimation Until 2050

According to 2018 data, the potential of biomass available for energy in Ukraine is about 23 Mtoe, the biggest constituents being agricultural residues (44% of the

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80%

70%

70% 55%

60% 50%

40%

40%

30%

30% 20% 10% 0%

8.9%

11%

2018

2020

15%

2025

20%

2030

2035

2040

2045

2050

Fig. 18 Forecasted share of RES in the power production until 2050

65%

70% 55%

60% 45%

50% 35%

40% 25%

30% 18%

20% 10% 0%

8.0%

2018

12%

2020

2025

2030

2035

2040

2045

2050

Fig. 19 Forecasted share of RES in the heat production until 2050

40%

35%

30%

25% 17%

20%

10% 2.2%

4%

6%

9%

12%

0% 2018

2020

2025

2030

2035

2040

Fig. 20 Forecasted share of RES in the transport sector until 2050

2045

2050

Technologies for Energy Production …

12

329

100% 85%

81%

80%

77%

75%

73%

71%

69%

67%

2040

2045

2050

60% 40% 20% 0% 2018

2020

2025

2030

2035

Fig. 21 Forecast for biomass share of all RES in heat production

50%

44% 38%

40% 32% 30%

26% 19%

20% 10%

14% 7%

10%

0% 2018

2020

2025

2030

2035

2040

2045

2050

Fig. 22 Forecast for biomass share in heat production

14% 12%

11.0%

10%

9.0% 7.5%

8% 6.0% 6%

4.5% 3.5%

4% 2.1%

2.5%

2018

2020

2% 0% 2025

2030

2035

2040

Fig. 23 Forecast for biomass share of all RES in power production

2045

2050

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9% 7.7%

8% 7% 6% 5.0% 5% 4%

3.0%

3% 1.8%

2% 1%

0.2%

0.3%

0.5%

2018

2020

2025

0.9%

0% 2030

2035

2040

2045

2050

42%

41%

40%

2040

2045

2050

Fig. 24 Forecast for biomass share in power production

50%

45%

45%

45%

45%

44%

40% 30% 20% 10% 0%

2018

2020

2025

2030

2035

Fig. 25 Forecast for biomass share of all RES in transport sector

16%

14.0%

12%

10.3% 7.1%

8% 5.3% 4.1% 4% 1.0%

1.8%

2.7%

0% 2018

2020

2025

2030

2035

2040

2045

2050

Fig. 26 Forecast for biomass share in the total final consumption of energy in transport

total) and energy crops (32%) (Table 20; Fig. 29). Within the agricultural residues, the largest amounts fall to the shares of grain crops straw (33%) and by-products of grain maize production (35%).

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331

100% 80%

77%

73%

65%

60%

60%

55%

50%

43%

40%

38%

20% 0% 2018

2020

2025

2030

2035

2040

2045

2050

Fig. 27 Forecasted biomass shares of all RES in Ukraine’s total primary energy supply

30% 25% 17%

20%

24%

14%

15% 10% 5%

21%

3.4%

4%

2018

2020

6%

10%

0% 2025

2030

2035

2040

2045

2050

Fig. 28 Forecasted contribution of bioenergy to Ukraine’s total primary energy supply

Expert estimation shows that in 2050 this potential may increase to more than 47.5 Mtoe/yr that is practically double as compared with 2018 (Table 21). Thus, the level of biofuel consumption in 2050 (about 20 Mtoe) envisaged in the roadmap will come to only 43% of the biomass potential available at that time. Main factors for the growth of energy potential of biomass until 2050 include: – Increase in the yield of crops, first of all, cereals. – Significant increase in the economic potential of biogas obtained from different types of feedstock. – Doubling of areas under energy crops and an increase in their yield. – Growth of the level of the net annual forest increment felling. – Switchover to II generation biofuels and new types of feedstock for I generation biofuels.

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Table 20 Bioenergy potential in Ukraine in 2018 Type of biomass

Theoretical potential, million tons

Economic potential % of the Mtoe theoretical potential

Grain crops straw 32.8 30 3.36 Straw of rapeseed 4.9 40 0.68 By-products of grain maize production 46.5 40 3.56 (stems, cobs) By-products of sunflower production (stems, 26.9 40 1.54 heads) Secondary agricultural residues (sunflower 2.4 100 1.00 husk) Wood biomass (fuel wood, logging residues, 8.8 96 2.06 wood working waste) Wood biomass (deadwood, wood from 8.8 45 1.02 shelterbelt forests, biomass from agrarian plantation pruning and removal—APPR) Biodiesel (from rapeseed) – – 0.39 Bioethanol (from maize and sugar beet) – – 0.82 42 0.99 Biogas from waste and by-products of 2.8 bln m3 CH4 agro-industrial complex 29 0.14 Landfill gas 0.6 bln m3 CH4 28 0.09 Sewage gas (industrial and municipal waste 0.4 bln m3 CH4 waters) 100 2.57 Energy crops: maize for biogas (1 mln ha*); 3.0 bln m3 CH4 miscanthus, poplar, willow (1 mln ha*) 11.5 100 4.88 Total – – 23.10 * Provided that 1 million hectares of unused agricultural land is used for raising the energy crops

5.3

Suggested Use of Bioenergy Potential by Types of Biomass and Obtained Energy Carrier Until 2050

The structure and directions of using bioenergy potential envisaged in the roadmap are presented in Figs. 30 and 31. The covered types of biofuels include wood biomass, primary and secondary agricultural residues, energy crops, biogas from different types of feedstock and liquid biofuels (biodiesel and bioethanol), the total amount of consumption in 2050 being about 20 Mtoe. Directions of biofuels use include the production of heat, power, biomethane, and motor biofuels. Biomethane will be used for power and heat production and as gaseous motor fuel. The suggested structure of production and consumption of biofuels takes into account and reflect the key trends that, according to the expert prediction, will take place in the bioenergy sector of Ukraine during 2020–2050:

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(a) Total potential of biomass

333

(b) Potential of agricultural residues

Fig. 29 Structure of the biomass potential in Ukraine (2018), Mtoe

– Increase in the share of agro-biomass, namely agricultural residues and energy crops, in the structure of solid biofuels consumption up to 60% and 20% of the total in 2050, respectively. – Minimal growth in the use of wood biofuels, namely 1.2 times in 2050 (against 8 times for agricultural residues during 2020–2050). – Significant increase in the production of biogas and liquid biofuels: up to 4.7 Mtoe/yr and 0.85 Mtoe/yr, respectively, in 2050. – The launch and growth of the production of biomethane and motor biofuels of the second generation: up to 2.4 Mtoe/yr and 0.43 Mtoe/yr in 2050, respectively.

5.4

Biofuels in the Sectors of Heat Production, Power Production and Transport

In Ukraine, over half of the final energy consumption is accounted for heat. Taking this into consideration, according to the roadmap, about a half of the total consumption of biofuels will fall to solid biofuels used for heat production (11.7 Mtoe) in 2050 (see Fig. 31). The rest will be divided into relatively comparable proportions between the solid biofuels for electricity production (3.0 Mtoe), biogas (2.36 Mtoe), and biomethane (2.36 Mtoe). The smallest share of the total biofuel consumption in 2050 falls to liquid biofuels (0.85 Mtoe); of them, the second-generation biofuels (the production of which has not started yet in Ukraine at all) account for 0.43 Mtoe. Forecast for the structure of the use of solid biofuels for heat and power production in different sectors in Ukraine is presented in Figs. 32 and 33.

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Table 21 Forecast for the energy potential of biomass in Ukraine in 2050 Type of biomass

Theoretical potential, million tons

Economic potential % of the Mtoe theoretical potential, %

Grain crops straw of* 49.2 30 5.04 Straw of rapeseed 4.9 40 0.68 By-products of grain maize production 58.1 40 4.45 (stems, cobs)* By-products of sunflower production 26.9 40 1.54 (stems, heads) Secondary agricultural residues 2.4 100 1.00 (sunflower husk) Wood biomass (fuel wood, logging residues, 12.3 96 2.88 wood working waste)* Wood biomass (deadwood, wood from 8.8 45 1.02 shelterbelt forests, biomass from APPR) Biodiesel (I and II generation)* – – 1.10 Bioethanol (I and II generation)* – – 2.33 83 5.92 Biogas from waste and by-products 8.4 bln m3 CH4 of agro-industrial complex* 70 0.42 Biogas from MSW* 0.7 bln m3 CH4 31 0.11 Sewage gas (industrial and municipal waste 0.4 bln m3 CH4 waters)* 100 6.43 Energy crops*: maize for biogas 7.5 bln m3 CH4 (2 mln ha**) miscanthus, poplar, willow (2 mln ha**); 34.5 100 14.65 Total – – 47.57 * Components of the biomass potential, the growth of which is expected by 2050. Other components are left at their level estimated for 2018 according to the conservative approach **Provided that 2 million hectares of unused agricultural land are used for raising the energy crops

These data show that the volume of heat production from solid biomass will be comparable in DH/public sector, industry and individual heating closer to 2050, while power production from biomass will be concentrated more in the industrial sector during the whole period until 2050.

5.5

Envisaged Bioenergy Equipment to Be Introduced Until 2050

It is assessed that the total installed capacity of bioenergy equipment will be about 50 GWth and 5.2 GWel in 2050. The total consumption of biofuels will be over 20 Mtoe/yr, which actually corresponds to almost entire current potential of biomass in Ukraine (see Table 20).

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335

22 Деревна біомаса Солома, стебла Лушпиння соняшнику Енергетичні рослини Енергетичні рослини (біогаз) ТПВ (біогаз)

20 18 16

0.85 0.82 0.63 1.51 0.19 0.40

14 12

0.50 1.04 0.13 0.28

10 8 6

0.26 0.39 1.78

0.29 0.04 0.08 0.37

4 2

0.39 0.59 1.01 0.50

0.07 0.15

0.17 0.19 0.02 0.00 0.38 0.79

1.78 0.64

2.36

2.14 0.27

3.40 0.42

0.90

0.56 3.01 2.76 0.80

0.84

0.75

6.40

7.34

7.85

4.80 3.11

0.00 0.25 0.05 1.90

0.00 0.26 0.07 1.95

0.00 0.30 0.08 2.12

0.04 0.01 0.34 0.10

0.05 0.04 0.38 0.40

2.35

2.40

2.51

2.64

2.74

2.83

2.89

2.95

3.00

2015

2016

2017

2018

2019

2020

2025

2030

2035

2040

2045

2050

0

Fig. 30 Suggested structure of using biofuels in Ukraine until 2050, by type, Mtoe

22 20 18

Тверді біопалива (тепло)

Тверді біопалива (е/е)

Рідкі БП І покоління

Рідкі БП ІІ покоління

Біогаз (е/е, тепло)

Біометан

2.36

16 0.63 1.47 0.25 0.38

14 12 10 0.08 0.73 0.08 0.31 1.51

8 6

0.02 0.38 0.03 0.23 0.72

4 2

0.29 1.16 0.15 0.35 2.00

0.00 0.04 0.16

0.00 0.05 0.19

0.00 0.26 0.00 0.17 0.18

0.00 0.02 2.17

0.00 0.08 2.20

0.00 0.12 2.38

2.64

3.03

3.39

2015

2016

2017

2018

2019

2020

1.19

2.36

1.78 0.39 0.43

0.43 0.43 3.00

2.82

2.51

9.89

11.03

11.70

2045

2050

8.07 5.86 4.45

0 2025

2030

2035

2040

Fig. 31 Suggested structure of using biofuels in Ukraine until 2050, by type of the obtained energy carrier, Mtoe

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Fig. 32 Forecasted structure of using solid biofuels for heat production in different sectors in Ukraine, Mtoe

Fig. 33 Forecasted structure of using solid biofuels for power production in different sectors in Ukraine, Mtoe

Table 22 presents the distribution of equipment by sectors in 2050: household sector (domestic boilers and stoves on solid biofuels), DH/public sector (boilers and CHP plants on solid biofuels), and industry (boilers, CHP plants, TPPs, ORC TPPs on solid biofuels, CHP plants on biogas/biomethane, CHP plants on biogas obtained from waste).

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Table 22 Envisaged installed capacity of bioenergy equipment in Ukraine in 2050 Type of equipment

Household sector Domestic boilers and stoves on wood biomass (firewood, pellets, briquettes) Domestic boilers on agro-biomass (pellets, briquettes, small bales) Domestic boilers on energy crops (pellets, chips) DH + public sector Boilers (wood biomass) Boilers (primary agricultural residues) Boilers (secondary agricultural residues) Boilers (energy crops) CHP plants (wood biomass) CHP plants (primary agricultural residues) CHP plants (energy crops) Industry Boilers (wood biomass) Boilers (primary agricultural residues) Boilers (secondary agricultural residues) CHP plants (wood biomass) CHP plants (primary agricultural residues) CHP plants (secondary agricultural residues) CHP plants (biogas, biomethane) TPPs (primary agricultural residues) TPPs (secondary agricultural residues) TPPs (wood) TPPs (energy crops) TPPs ORC (primary agricultural residues) CHP plants on biogas obtained from waste (landfills, mechanical and biological treatment of waste, wastewater) Total

5.6

Total installed capacity in 2050 MWel MWth 5285 7500 6000 600 12,750 900 2750 225 1500 2250 1400 3000 300 240 1520 300 2870

75 500 750

265

80 475 100 2040 380 160 55 340 25 250

49,655

5230

Assessment of Investments Required for Implementing Roadmap Until 2050

Preliminary expert estimates indicate that the implementation of the roadmap requires investments in the range of 21…33.5 billion EUR, depending on the cost of the equipment to be installed. Approximate distribution of the investments by type of bioenergy equipment/technologies is given in Table 23.

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Table 23 Assessment of investments required for the implementation of the roadmap Types of bioenergy equipment/technology

Specific capital costs*

Expected investments, bln EUR

Individual boilers and stoves on solid biomass

50–100 EUR/kWth 200–300 EUR/kWth 2500–4000 EUR/kWel 2500–4000 EUR/kWel

0.9–1.9

10,000– 16,000 EUR/(m3 CH4/hr) 837–1648 EUR/ktoe 2346–4246 EUR/ktoe

1.1–1.8

Boilers on solid biomass CHP plants/TPPs on solid biomass CHP plants on biogas/biomethane (agri-residues, landfill gas, mechanical and biological treatment of waste, wastewater) Production of biomethane (motor fuel)

Production of liquid biofuels of I generation Production of liquid biofuels of II generation

4.3–6.5 7.4–11.8 5.7–9.1

0.4–0.7 1.0–1.8

Total 20.8–33.5 These are some average figures as the specific capital costs depend on type/capacity of an installation, type of applied technology, and used biomass. They will be gradually decreasing during the period until 2050

*

5.7

Roadmap Summary

Roadmap summary indices by benchmark years are presented in Table 24. According to the forecast presented in the roadmap, by 2050, the development of bioenergy in Ukraine may lead to: replacement of nearly 20 bln m3/yr of natural gas and more than 1 Mt of petrol and diesel;—reduction of GHG emissions by over 54 Mt CO2-eq/yr; creation of over 162,000 direct and indirect jobs. Of these, the solid biomass segment makes the biggest contribution accounting for 17.9 bln m3/yr of natural gas, 35 Mt CO2/yr and over 107,000 new jobs in 2050 (Table 25). Another 2.1 bln m3/yr of natural gas and 0.4 Mt/yr of petrol and diesel will be replaced at the expense of the production and consumption of biogas/ biomethane (Tables 26, 27, and 28). The contribution of liquid biofuels to Roadmap indexes in 2050 will lie in the replacement of 0.83 Mt/yr of petrol/diesel, reduction of almost 2 Mt CO2/yr of GHG and creation of over 8,500 new jobs (Table 29). Estimation of natural gas substitution volumes in Tables 26, and 27 takes into account substitution of natural gas as a result of heat production from biogas and biomethane only. Estimation of CO2 emission reductions in Tables 26, 27, and 28 takes into account the avoided emissions from the combustion of fossil fuel, avoided

Installed capacity of bioenergy equipment MWel MWth

2020 8206 202 2025 12,276 844 2030 19,087 1846 2035 30,237 2804 2040 39,338 3609 2045 45,351 4299 2050 49,655 5230 * Including liquid and gaseous

Year

3.77 5.83 8.57 12.01 15.13 17.64 20.28 biofuels for transport

Consumption of biofuels* (Mtoe)

Table 24 Bioenergy Roadmap summary indices

4.34 6.35 9.11 12.62 15.77 17.98 19.92

Replacement of NG (bln m3)

0.17 0.25 0.39 0.50 0.67 0.96 1.23

Replacement of petrol and diesel (Mt)

8.90 14.31 21.35 30.37 38.66 45.79 54.40

Reduction of CO2 emission (Mt/yr)

1.52 3.73 7.07 10.78 14.15 16.94 19.70

Min

2.52 6.06 11.44 17.43 22.85 27.38 31.81

Max

Required investments (bln EUR)

16,914 31,438 54,302 86,237 115,439 139,013 162,710

Creation of new jobs, number

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Table 25 Forecast for the development of bioenergy until 2050 in terms of solid biofuels Year

Installed capacity

Consumption of biofuels (Mtoe)

Replacement of NG (bln m3)

Reduction of CO2 emission (Mt/yr)

Required investments, (bln EUR)

Creation of new jobs

MWth

MWel

2020

8103

105

3.57

4.33

8.49

1.14

1.85

13,334

2025

11,955

552

5.18

6.29

12.32

2.74

4.39

23,284

2030

18,465

1295

7.36

8.94

17.53

5.24

8.39

39,853

2035

29,173

1908

10.06

12.22

23.95

7.90

12.64

64,023

2040

37,854

2421

12.40

15.06

29.51

10.28

16.41

85,987

2045

43,307

2738

13.85

16.82

32.97

11.75

18.75

99,755

2050

46,520

2940

14.71

17.86

35.01

12.63

20.15

107,543

Min

Max

Table 26 Forecast for the development of bioenergy until 2050 in terms of biogas Year

Installed capacity MWel

MWth

Consumption of biofuels (Mtoe)

Replacement of NG (bln m3)

Reduction of CO2 emission (Mt/yr)

Min

Max

2020

97

104

0.03

0.00

0.11

0.24

0.39

1843

2025

281

302

0.38

0.05

1.40

0.70

1.13

5347

2030

511

547

0.73

0.11

2.70

1.28

2.04

9702

2035

760

814

1.16

0.20

4.27

1.28

3.04

14,441

2040

910

975

1.47

0.28

5.42

1.90

3.64

17,297

2045

1073

1150

1.78

0.38

6.56

2.28

4.29

20,390

2050

1385

1484

2.36

0.55

8.70

2.68

5.54

26,324

Required investments (bln EUR)

Creation of new jobs

Table 27 Forecast for the development of bioenergy until 2050 in terms of biomethane Year

Installed capacity MWel

MWth

Consumption of biofuels (Mtoe)

Replacement of NG (bln m3)

Reduction of CO2 emission (Mt/yr)

2020

–

–

0.00

0.00

0.00

0.00

0.00

–

2025

11

19

0.02

0.01

0.07

0.03

0.04

200

2030

41

74

0.07

0.04

0.26

0.10

0.16

772

2035

136

249

0.23

0.15

0.85

0.34

0.54

2584

2040

277

508

0.47

0.30

1.74

0.69

1.11

5267

2045

488

894

0.83

0.53

3.06

1.22

1.95

9265

2050

901

1 651

1.53

0.99

5.66

2.25

3.60

17,110

Required investments (bln EUR) Min

Creation of new jobs

Max

12

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Table 28 Forecast for the development of bioenergy until 2050 in terms of gaseous biofuels (biomethane) Year

Production

Replacement of motor fuels including:

Mt

Mtoe

NG (bln m3)

Diesel and petrol (Mt)

Total (Mtoe)

2020

0.00

0.00

0.00

0.00

0.00

2025

0.00

0.00

0.00

0.00

0.00

2030

0.01

0.01

0.01

0.00

2035

0.05

0.06

0.05

0.02

2040

0.14

0.16

0.12

2045

0.32

0.36

2050

0.75

0.83

Reduction of CO2 emissions (Mt/yr)

Required investments (bln EUR)

Creation of new jobs

Min

Max

0.00

0.00

0.00

–

0.01

0.00

0.00

8

0.01

0.05

0.02

0.03

47

0.06

0.21

0.08

0.12

224

0.06

0.16

0.58

0.21

0.34

609

0.24

0.15

0.36

1.31

0.47

0.76

1377

0.52

0.40

0.83

3.05

1.10

1.76

3195

emissions from the manufacture of inorganic fertilizers, avoided landfill emissions from the digestion of biodegradable waste, avoided emissions from manure management, and avoided emissions from the burning of crops. The calculations take a specific indicator of CO2 emissions reduction by 1 toe of primary energy from biogas produced from a mix of different sources, estimated when calculating the global potential for biogas energy production. Thus, with an estimated biogas production potential of 12,065 TWh (equivalent to 1,037 Mtoe), the potential for CO2 emission reductions estimated to 3,825 Mt of CO2eq, and therefore the specific reduction potential is 3.687 tons of CO2eq per 1 toe. Based on the Roadmap data for 2050 on the consumption of biofuels, the possible currency saving caused by the reduced imports of natural gas and petrol/ diesel to Ukraine is estimated as 2.31 bln USD/yr and 0.77 bln USD/yr, respectively, the total sum being 3.08 bln USD/yr.

6 Conclusions There are good preconditions for mobilizing lignocellulosic agricultural residues for the production of energy. However, as agricultural residues as fuel have some specific characteristics, the utilization of these residues for energy requires the application of specialized equipment and special technological solutions. This can improve the quality of combustion and combustion efficiency and ensure compliance with all the environmental requirements. Results of the performed life-cycle assessment show high efficiency of the usage of agricultural residues from energy and environmental points of view. Example of the elaborated Roadmap for bioenergy development in Ukraine demonstrates the effective way for utilizing the available potential of biomass with the focus on biomass of agricultural origin.

2020 2025 2030 2035 2040 2045 2050

Year

0.27 0.39 0.58 0.70 0.85 1.09 1.12

0.00 0.04 0.11 0.20 0.31 0.49 0.53

0.17 0.26 0.39 0.50 0.63 0.82 0.85

0.00 0.03 0.08 0.15 0.25 0.39 0.43

Including II-gen biofuels (toe) 0.17 0.25 0.38 0.48 0.61 0.80 0.83

0.17 0.26 0.39 0.50 0.63 0.82 0.85

Mtoe

Mt

Total (Mtoe)

Total (Mt)

Including II-gen biofuels (Mt)

Replacement of petrol and diesel

Production of biofuels

Table 29 Forecast for the development of bioenergy until 2050 in terms of liquid biofuels

0.29 0.52 0.82 1.08 1.41 1.88 1.98

Reduction of CO2 emission (Mt/yr)

145 257 447 640 905 1285 1359

286 496 851 1205 1687 2382 2516

Required investments (mln EUR) Min Max

1737 2599 3928 4965 6280 8227 8538

Creation of new jobs

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Bibliography 1. Oliinyk, Y., Antonenko, V., Chaplygin, S., et al.: Preparation and implementation of projects to replace natural gas with biomass for thermal energy production in Ukraine. In: Geletukha, G.G. (ed.) Guideline (2015) 2. Energy and Environmental Analysis, Inc., an ICF International Company, and Eastern Research Group, Inc.: Biomass Combined Heat and Power Catalog of Technologies U. S. Environmental Protection Agency (2007) 3. UABIO Position Paper № 24, 2020, https://uabio.org/wp-content/uploads-/2020/09/ Analityka_UABIO_-energetychne-vykorystannia_agrovidhodiv_en.pdf 4. van Loo, S., Koppejan, J.: The Handbook of Biomass Combustion and Co-firing (2008) 5. Sander, B., Skøtt, T.: Bioenergy for electricity and heat—experiences from biomass-fired CHP plants in Denmark (2007) 6. Shpaara, D.: Corn. Growing, harvesting, conservation and use (2009) 7. Grain maize and corn-cob-mix harvested production in EU. Statistical data from Eurostat. https://ec.europa.eu/eurostat/en/ 8. World Agricultural Production, USDA Reports, https://apps.fas.usda.gov/psdonline/circulars/ production.pdf 9. UABIO Position Paper № 23, 2020. https://uabio.org/wp-content/uploads/2020/04/positionpaper-uabio-23-en.pdf 10. OECD-FAO Agricultural Outlook 2019–2028. http://www.fao.org/3/ca4076en/ca4076en.pdf 11. Ertl, D.: Sustainable corn stover harvest. Iowa Corn Promotion Board (2013) 12. The value given by Ukraine’s National Academy of Agrarian Sciences in its letter to the Institute of Engineering Thermophysics (N 5–2/256 of 16.11.2012) 13. Schon, B., Darr, M.: Corn stover ash. PM 3051L, 2014. https://store.extension.iastate.edu/ Product/Corn-Stover-Ash 14. Physico-chemical composition of corn stover and corn cobs. Phyllis database containing information on the composition of biomass and waste. https://phyllis.nl/ 15. Cherenkov, A.V., Tsykov, V.S., Dziubetskyi, B.V., Shevchenko, M.S., et al.: Intensification of corn technologies—a guarantee for yield stabilization at 90–100 m.c./ha level (practical recommendations). NU Institute of Steppe zone agriculture NAASU, Dnepropetrovsk (2012) 16. Heggenstaller, A.: DuPont cellulosic ethanol: Sustainable corn stover harvest for biofuel production (2012) 17. Fleschhut, M., Hulsbergen, K.-J., Thurner, S., Eder, J.: Analysis of different corn stover harvest systems. LANDTECHNIK 71(6) (2016) 18. Recovering Maize Cob: Converting Untapped Biomass Resource into Valuable Feedstock. Becool project website. https://www.becoolproject.eu/2018/10/22/recovering-maize-cobconverting-untapped-biomass-resource-into-valuable-feedstock/ 19. Pari, L., Bergonzoli, S., Suardi, A., Alfano, V., Scarfone, A., Lazar, S.: Maize cob harvesting: first assessment of an innovative system. In: 26th European Biomass Conference and Exhibition, 2018 20. Erickson, M.J., Tyner, W.E.: The economics of harvesting corn cobs for energy https://www. extension.purdue.edu/extmedia/ID/ID-417-W.pdf 21. Darr, M., Shah, A., Peyton, K., Webster, K.: Corn stover storage methods https://store. extension.iastate.edu/product/14077 22. Rules of fire safety in the agro-industrial complex of Ukraine. http://zakon.rada.gov.ua/laws/ show/z0313-07 23. UABIO Position Paper № 25, 2020. https://uabio.org/wp-content/uploads/2020/10/uabioposition-paper-25-en-1.pdf 24. Sunflower seed statistics: FAOSTAT portal. http://www.fao.org/faostat/en/#data

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25. 26. 27. 28.

State Statistics Service of Ukraine:Ukraine’s foreign trade. Statistical yearbook (2019) State Statistics Service of Ukraine: Agriculture of Ukraine. Statistical yearbook for 2018. Recommendations for advanced sunflower production technology.—К.: «Urozhai» (1981) Kokhan, A.V., Gangur, V.V., Koretskyi, O.Ye., Len, O.I., Manko, L.A.: Sunflower in the crop rotations of the Left-Bank Forest-Steppe of Ukraine. Bulletin of the Center for Scientific Support of Agricultural Production of Kharkiv Region 2015, №18. Nikitchyn, D.I.: Sunflower. К.: Urozhai (1993) BEFS assessment for Turkey: Sustainable bioenergy options from crop and livestock residues. FAO, 2016. http://www.fao.org/3/a-i6480e.pdf Marechal, V., Rigal, L.: Characterization of by-products of sunflower culture—commercial applications for stalks and heads. Ind. Crops Prod. 10(3), 185–200 (1999) Dubrovin, V.O., Golub, G.A., Drahniev, C.V., Geletukha, G.G., Zheliezna, T.A., Kucheruk, P.P., Matveev, Yu.B., Kudria, S.O., Zabarnyi, G.M., Masliukova, Z.V.: Methods of generalized assessment of technical energy potential of biomass (2013) Duca, D., Toscano, G., Riva, G., Mengarelli, C., Rossini, G., Pizzi, A., Del Gatto, A., Foppa Pedretti, E.: Quality of residues of the biodiesel chain in the energy field. Ind. Crops Prod. 75 (Part A), 91–97 (2015) Vasiliev, D.: Sunflower. M.: Agropromizdat (1990) Kutsenko, O., Kocherga, A., Filonenko, C.: Industrial crops. Tutorial (2003) Mathias, J.D., et al.: Upcycling sunflower stems as natural fibers for biocomposite applications. BioResources 10(4), 8076–8088 (2015) Kovačić, Đ, Kralik, D., Rupčić, S., Jovičić, D., Spajić, R., Tišma, M.: Soybean straw, corn stover and sunflower stalk as possible substrates for biogas production in croatia: a review. Chem. Biochem. Eng. Q. 31(3), 187–198 (2017) Characterisation of Agricultural Waste Co- and By-Products. Report of AgroCycle project, 2016. Unal, H., Alibas, K.: Determining of the suitable burning method for wheat straw and sunflower stalks. J. Appl. Sci. 6, 435–444 (2006) Zhurka, M., Spyridonidis, A., Vasiliadou, I.A., Stamatelatou, K.: Biogas production from sunflower head and stalk residues: effect of alkaline pretreatment. Molecules 25(1), 164 (2020) Guide to biogas. From production to use, FNR, 2012 Wellinger, A., Murphy, J., Baxter, D.: The Biogas Handbook. Science, Production and Applications. Woodhead Publishing Series in Energy (Book 52) (2013) Monlau, F., Barakat, A., Steyer, J.P., Carrere, H.: Comparison of seven types of thermo-chemical pretreatments on the structural features and anaerobic digestion of sunflower stalks. Biores. Technol. 120, 241–247 (2012) Monlau, F., Kaparaju, P., Trably, E., Steyer, J.P., Carrere, H.: Alkaline pretreatment to enhance one-stage CH4 and two-stage H2/CH4 production from sunflower stalks: mass, energy and economical balances. Chem. Eng. J. 260, 377–385 (2015) Brazil, O.A.V., et al.: Integral use of lignocellulosic residues from different sunflower accessions: analysis of the production potential for biofuels. J. Clean. Prod. 221, 430–438 (2019) Ruiz, E., Cara, C., Ballesteros, M., Manzanares, P., Ballesteros, I., Castro, E.: Ethanol production from pretreated olive tree wood and sunflower stalks by an SSF process. Appl. Biochem. Biotechnol. 130(1–3), 631–643 (2006) Raquel Ruiz E., et al.: Strategies for bioethanol production from sunflower stalks. Afinidad— Barcelona 68(556), 417–423 (2011) Yusoff, M.N.A.M., Zulkifli, N.W.M., Masum, B.M., Masjuki, H.H.: Feasibility of bioethanol and biobutanol as transportation fuel in spark-ignition engine: a review. RSC Adv. 5, 100184– 100211 (2015)

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49. International Organization for Standardization: Environmental Management: Life Cycle Assessment: Principles and Framework, vol. 14040. ISO (1997) 50. Nussbaumer, T., Oser, M.: Evaluation of biomass combustion based energy systems by cumulative energy demand and energy yield coefficient. Report for International Energy Agency and Swiss Federal Office of Energy, 2004 51. Directive (EU) 2018/2001 of the European Parliament and of the Council of 11 December 2018 on the promotion of the use of energy from renewable sources. https://eur-lex.europa.eu/ legal-content/EN/TXT/?uri=uriserv:OJ.L_.2018.328.01.0082.01.ENG&toc=OJ:L:2018:328: TOC

Chapter 13

Purification of Waste Oils from the Transport Industry Through Nanotechnology Ionel Pisa, Mihai Dragne, and Elena Pop

Abstract Waste oils are considered toxic and hazardous waste for both the environment and humans. Environmental pollution with waste oils can be reduced if this hazardous waste is recovered by purifying and reusing it in the automotive and industrial fields. This technology of purification of waste oils requires organizational, scientific, and economic efforts for an evolution of this branch. This chapter promotes the exploitation and use of deposits of natural absorbents (bentonites, zeolites) and the use of new energy resources, while saving classical resources. Keywords Bentonite


Engine
Environmental impact
Waste oils

1 Introduction Waste oils result from lubricants of natural or synthetic origin, used in internal combustion engines and in industrial processes. At the same time, waste oils are considered toxic and hazardous waste for both the environment and humans. Holders of waste oils are obliged to ensure the sorted storage and sealing of containers of different types of waste oils. Sealed containers, in which used oils are collected, require a fairly high resistance to mechanical and thermal shock, as they are stored in spaces specially designed to prevent environmental pollution in the event of unforeseen leaks. Mixing of used oils with each other or of oils containing polychlorinated biphenyls or other similar compounds, their discharge into the ground and their discharge is strictly prohibited.

I. Pisa (&)
M. Dragne
E. Pop Mechanics and Mechatronics Faculty, University Politehnica of Bucharest, Bucharest, Romania e-mail: [email protected] E. Pop e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_13

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Individuals owning used oil have the obligation to hand over the full amount free of charge to legal entities authorized to collect used oils. The oils used, which come from heat engines, wear out during operation, causing their properties to change, and need to be changed. In general, the common factors that lead to oil wear are the metal particles in the engine left in the oil, dirt and sometimes water. Waste oils contain metal particles and hydrocarbons. Environmental pollution with waste oils can be reduced if this hazardous waste is recovered by purifying and reusing it in the automotive and industrial fields. This technology of purification of waste oils requires organizational, scientific, and economic efforts for an evolution of this branch. The paper proposes the development of advanced and integrated technologies for materials with adsorbent properties (e.g., bentonite) and the use of these materials in waste oil. Recovery processes, with purifying and energy recovery effect. The main objective is to replace diesel fuel, which is an expensive fuel with purified oils for energy production. To achieve this, we must turn our attention to two important sets of laboratory experiments. The first tests are related to determining the optimal concentration of bentonite to remove metals from used oil. Purification of waste oil leads to the protection of the combustion plant, to increase its life and to reduce pollutant emissions. The second set of experiments concerns the determination of the energy characteristics of waste oil and purified waste oil for energy production. Elemental analysis, lower calorific value, viscosity, density, and ash analysis were determined. Experimental testing of the combustion process on a small-scale boiler was performed, and the results showed an improved combustion process and reduction of pollutant emissions for purified waste oil. Environmental pollution is a topical issue and the attempt to obtain non-polluting fuels or the recovery of waste materials for energy purposes is of concern to many researchers today. Used engine oils can be contaminated with impurities resulting from unwanted oxidation processes: sediments, water, metal particles and degraded additives [1]. There are several ways to remove these contaminants. The proposed technology aims at the process of purification of residual oils from internal combustion engines, by treatment with natural or modified nanostructured compounds. In this regard, bentonite was chosen as the nanostructured material. Bentonite powder plays an important role in the purification of waste oils [2]. Finally, this method of purifying used oil was applied to an industrial hall, from a car service. The application of the research results will contribute to ensuring a sustainable economic development at the level of the analyzed field. This promotes the exploitation and use of deposits of natural absorbents (bentonites, zeolites) and the use of new energy resources, while saving classical resources. An important benefit of waste oil treatment-purification is the elimination of a complex source of pollution and the return to consumption of a combustible material. As a result of the investments for the exploitation and use in the field of the project of the natural

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deposits of absorbents, an economic development of the respective geographical area will take place, which will lead to the improvement of the living and health conditions of the local population. By creating new jobs, so by increasing the employment rate, it also contributes to increasing the living standards of the population. Also, through the works within the topic, jobs are supported for high value specialists in the field of research, while providing conditions for training specialists in the field and enriching the experience by accumulating the latest knowledge in the field. Purification, as well as regeneration of waste oils, in high level application, encounters great organizational and economic difficulties. The major difficulty is the collection, storage, transport, and processing by appropriate categories in order to apply the appropriate technologies, for obtaining in economic conditions some high-quality base oils. To minimize these difficulties, it is expected to collect used oils in three categories: engine oils (including turbine, hydraulic and vehicle transmissions), electrical transformer oils and other oils. In the European Union, the collection and recycling of used edible oils and fats are carefully regulated due to the danger posed by this waste to human health and the environment. A global approach to the problem consists in finding a simple and efficient method as well as the realization of economically accessible installations that using nanostructured materials can be applied directly to the place of collection of these used oils. The waste collected is recovered, becoming, in the simplest case, a source of energy and more. Nanotechnology for the purification of used oils by their adsorption in bentonite is a reliable and economical solution for extracting metal particles resulting from the wear of moving parts of internal combustion engines. The oil thus purified can be reused, regenerated, or burned in order to produce energy. The companies that collect edible waste oil are more and more common in Romania, and most of them conclude contracts with restaurants, pizzerias, fast food, etc. offering also safe containers for storage, but also the transport of used oil, free of charge. In Romania, there were concerns for the collection and reuse of waste oils within the program of the three Rs (recovery, reconditioning and reuse), but more for economic reasons. The waste oils collected annually had reached the end of 1989 at the amount of 85,000 tons. However, they were not checked or collected on assortments and consequently not properly processed in an oil regeneration installation in order to be used efficiently later. After 1990, the amount of used oils collected for regeneration in Romania decreased almost 20 times, reaching less than 1000 tons at the end of 2000, although the national fleet of vehicles increased a lot, the number of fuel supply units Fast food and department stores have practically exploded, with the rest of the quantities of waste oils, especially in industry, declining slightly. Uncollected waste oils are a major source of soil and water pollution. This situation was also reached due to the fact that users were able to procure the necessary lubricants from

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Romanian or foreign companies—which no longer required them to deliver used oil —a situation that continues today. Law no. 22/2011 of July 28, 2011, is particularly important for the topic of this research, on establishing limit values, threshold values and criteria and methods for evaluating the metal content of waste oil. The purpose of this law is to prevent, eliminate, limit damage, and improve air quality in order to avoid adverse effects on human health and the environment [3]. Following the combustion process of the used oil, a considerable amount of ash remains, which contains metal residue, which is largely eliminated by the flue gases. Following the experiments, 1 L of used oil contains about 200 mg of metal impumg rities, at 10 m3N flue gases, resulting in a heavy metal concentration of 20 m3 N, being a fairly large amount, which is removed into the air and then infiltrates the soil. Metals with a fairly high percentage, which are found in the composition of used oil and which affect humans are: iron (Fe), zinc (Zn), Lead (Pb), Cadmium (Cd), Copper (Cu), Nickel (Ni). Iron, although the proper functioning of the immune system is dependent on this element, inhaled and ingested in excessive amounts, it becomes toxic to humans because it reacts with peroxides in the body, producing free radicals and triggering diseases such as Alzheimer’s, cancer, Parkinson’s, arthritis, cardiovascular disease and more [4]. Acute exposure to zinc oxides causes irritation of the respiratory tract and has symptoms such as chest pain, cough, fever, headache, nausea, and muscle aches [3]. The effect on health associated with lead pollution and its compounds leads to decreased hearing, developmental delays (in newborns), hypertension, neurotoxicity, increased infertility, especially in men, and hemoglobin synthesis. Reducing the synthesis of hemoglobin in the blood increases the chances of severe anemia and, at the same time, can cause inability to concentrate and decreased memory, which are consequences of central nervous system disorders. Children are most affected by this element, as the probability of ingesting lead-contaminated soil is higher in children under 5 years of age [3]. The organs most affected by cadmium exposure are the lungs and kidneys, due to ingestion or inhalation. Another effect of cadmium exposure is that it increases the appearance of impotence in men. Atherosclerosis can also occur, depending on the amount of cadmium in the blood. In the kidneys, the most common diseases are the accumulation of minerals [3]. Nickel allergies are frequently noticed in those who come into frequent contact with it, more precisely in the dermal level, thus causing allergic contact dermatitis. The most important health problem when exposed to nickel is lung cancer, cancer of the nostrils and sinuses of the paranasal sinuses, even if this residue is inhaled in small amounts. Other ailments recorded on nickel exposure are the sensation of metallic taste and decreased vitality, both physical and mental. Waste oils are a more attractive raw material for obtaining base oils than the corresponding crude oil fractions because the yield is higher and does not require extraction or solvent deparaffination operations. However, the processing of waste

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oils encounters great difficulties and increasingly complex technologies have been developed. For the future there are two variants of installation design: The first solution is to purchase the installation as such, being necessary modifications regarding the adaptation of the mixture between bentonite and used oil, by an automated electric mixer. Also, the bottom of the tank where the amount of metal ions adsorbed by bentonite and the bentonite itself will be deposited must be adapted in such a way that they are eliminated. The second solution would be for the equipment supplier to implement the mentioned changes from the beginning [3].

2 Current State of the Valorization by Burning of Waste Oil from Romania and the Physico-chemical Characteristics of Waste Oil This chapter presents the problems of waste oils from the automotive field, such as the collection, storage, transport, and processing by appropriate categories of this residue. Numerous studies have been conducted worldwide, which have led to the toxicity of waste oils, based on which technologies have been developed to purify them. Currently, among the most well-known and applied technological processes are: the TDA process, the INTERLINE process and the CEP-Mohawk process. They separate a fuel and a fraction of purified oil which, following processing, is used in the manufacture of lubricating oils. The problems related to the reduction of pollution with waste oils and related to the recovery of this hazardous waste are still numerous and require, at all times, many organizational, scientific and economic efforts to solve. The following is a block diagram of the waste oil purification process (Fig. 1). Starting from this scheme, the aim was to remove impurities from the used oil, without resorting to a chemical process. Also, in this chapter are presented the physical–chemical and energetic characteristics of mineral and used oils. The lubrication of the heat engines is done with the help of: • Basic oils, approximately 75–85% • Additives, approximately 15–25% Basic oils have the main role of lubricating parts. Depending on the classification, the raw material used and the manufacturing technique, they are: • mineral base oils, when the raw material is oil; • synthetic base oils, which are obtained by chemical methods; • semi-synthetic base oils are mixtures of mineral oils and synthetic oils in a proportion of approximately 20–30%. Additives are chemicals that, by mixing with the base oil, significantly improve its characteristics in the lubrication system of heat engines (Fig. 2).

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Fig. 1 Block diagram of the waste oil purification process [5]

Fig. 2 Composition of additives in an engine oil (SAE 5W-30) [6]

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The physico-chemical properties of engine oils depend to a large extent on the type of base oil, the technology applied in manufacturing, as well as the nature of the additives implemented in the base oil. Unctuousness and viscosity are the main lubrication and flow characteristics of oils. The density of the oils varies between 0.88 and 0.99 g/cm3. The flash point is the minimum temperature at which oil vapors ignite in the presence of a flame, which is between 200–250 °C for oil. The methods of analysis are the same for both the characteristics of waste oils and the characteristics of mineral oils (lubricants). Following the analysis of some waste oil samples, resulting from different categories, an average composition of the used oil was established (Table 1). Characteristics of waste oils: (a) TIN oils (Table 2) (b) Oils L (Table 3) (c) Oils H (Table 4) The following is a comparison between the characteristics of mineral and used oils, as follows: Mineral oils are obtained by vacuum distillation of fuel oil. The distillation process results in oils, Vaseline, and asphalt. Oils are mixtures of alkanes, alkenes, cycloalkanes, aromatic hydrocarbons, cyclic compounds with nitrogen and sulfur with a molecular weight of between 300 and 1000 atomic units of mass. The presence of alkanes (paraffins) is desirable in the composition of oils, while olefins (alkenes) and sulfur compounds greatly diminish the qualities of a lubricant. Waste oils are obtained from the wear of lubricating mineral oils, this process requiring adequate collection and sorting, in airtight containers, resistant to mechanical stress. The water content has undetectable values in mineral oils compared to used oils and has a share of 0–10% of the density of mineral oils, as well as used ones, which is temperature dependent, but differs slightly (880–990) kg/m3 at mineral oils compared to (950–990) kg/m3 for waste oils.

Table 1 Average composition of waste oils [7]

Component

% mass

Gasoline (final boiling point 177 °C) Diesel (final boiling point 177–343 °C) Oil (boiling range 343–429 °C) Heavy oil (bright stook) Water Additives Oxidation products Solid particles (dust, coal)

1–6 10–15 60–70 0–10 0–10 7–15 5–8 1–3

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Table 2 Characteristics of TIN oils [7] Characteristics

TIN 82/EP/90

TIN 125/EP/100

Density at 20 °C max., g/cm3 Freezing point, 0 °C max Viscosity at 50 °C, cSt Corrosion on copper blade, max Corrosion on steel Organic acidity KOH/g, min Water (distillation method) % Mechanical impurities, %

0.919 –20 82–90 2 – – Missing Missing

0.924 –15 130–140 2 – – Missing Missing

Table 3 Characteristics of L oils [7] Characteristics

L235

Relative density at 20 °C, g/cm3 Viscosity at 50 °C, cSt Engler viscosity °E, la 50 °C Viscosity at 100 °C, cSt Viscosity at 100 °C, °E Freezing point, 0 °C max Mechanical impurities Ash, %, max Coke figure, % max Mineral acidity and alkalinity Organic acidity, KOH/g, max Water (distillation method)

0.910 228–244 30–32 26 3.6 −4 Missing 0.01 1.4 Missing 0.04 Missing

Table 4 Characteristics of H oils [7] Characteristics

H100

H46A

Relative density at 15 °C max., g/cm3 Kinematic viscosity at 40 °C, cSt Organic acidity KOH/g, max Pour Point, °C Corrosive action on copper The tendency to foam under 5′ of blowing air Ash, % max

0.910 90–110 0.05 −8 16 15 0.01

0.905 44–49 0.2 −35 16 9 0.01

The density of diesel is about 830 kg/m3. Due to the close density of diesel and oils, they are easily miscible and do not separate after mixing. The flash point is the minimum temperature at which vapors released in admixture with air ignite from an incandescent source at normal atmospheric pressure. Mineral oils have a flash point between (200–250) °C, compared to used

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oils, which have a flash point between (160–190) °C. These values are much higher than that of diesel (8 °C). However, mixtures with light liquid fuel have a flash point close to that of diesel [8]. The viscosity of the mineral oil is temperature dependent. At a temperature of 20 °C, it will have a viscosity between the values (13.2–14.5) °E. The viscosity of used oil is also temperature dependent. At a temperature of 50 °C, it will have a viscosity between (16.6–14.7) °E. The percentage of sulfur in mineral and used oil is almost non-existent, this being a positive aspect, because, following the burning of sulfur, sulfur dioxide SO3 is formed, which, by hydration with water from the flue gases, forms sulfuric acid H2SO3. The advantage of low amounts of sulfur in oils is that it reduces the corrosion process of the cold surfaces of the boilers [8].

3 Technologies for the Purification of Waste Oils Filtered Nanostructured Materials This chapter is intended for the presentation of adsorbent materials and especially bentonite. This clay will be used in the experiments performed. In this chapter, we will present and compare other methods of purification of waste oils. Bentonites are mainly made of montmorillonite, they have a low hardness, are light, have a white color with shades of green–blue, pink, yellow, brown. The granulation varies between 1–500 mµ. The crack is typically conchoidal. The specific weight is between 2.7–2.8 g/cm3 and 1.6–1.8 g/cm3. They have a compact or porous appearance [9]. The chemical formula of montmorillonite is:
 ðNa; CaÞ0:3 ðAl; MgÞ2 Si4 O10 ðOHÞ2 nH2 O: Hydrated aluminosilicates are the formations that make up bentonite, which has a high adsorption and ion exchange capacity, due to the fact that it is largely composed of montmorillonite. Some cations can be replaced due to hydrated aluminosilicates, which make up complex molecules. Cation exchange and adsorption capacity depend on the crystallinity of the particles, the pore structure, the textural and structural features, the pH and temperature of the solution, the solution-adsorbent contact time, the chemical nature of the sorbent surface and the cation present in the mobile layer. Waste oil purification technologies are vast, but in this chapter were presented only the closest to the method of purification of waste oil in the research, namely: Prop technology. Technology name: PROP [10] Licensor: Phillips Petroleum Company.

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Process description: In this process, the used oil is treated with diammonium phosphate dissolved in water to separate metals and ash. The next step is that the preheated mixture, consisting of the used oil and the descaling solution, is sent to a container in which the saltwater is dispersed in the oil. The metal-phosphate compounds formed as a result of the chemical reaction are removed by filtration. Phosphates do not pose a danger to the environment, so they can be easily removed. The filtered oil is refreshed by separating light hydrocarbons and water, which can be used for plant needs. After cooling, the oil is mixed with hydrogen and filtered with diatomaceous earth to remove traces of compounds, which may poison the hydrotreating catalyst. The substances retained by the filter are generally burned and the diatomaceous earth is recycled. Finally, the oil is passed through the nickel/molybdenum catalyst in the hydrogenation reactor, where the compounds containing oxygen, sulfur, chlorine, nitrogen are removed, and the color of the oil is improved. Conclusions: This method is quite expensive. Both adsorption and hydrofining treatment are needed. The advantage is the quality of the oil, which contains less than 10 ppm of metal scrap. So far, the method has been applied in industry. Several plants have been built, but they are not operational due to financial problems (Fig. 3).

4 Adsorption Capacity Modeling Study for the Purification of Waste Oils The adsorption as a unit operation was deepened from the specialized literature, as well as the thermodynamic equilibrium of adsorption, the equilibrium at adsorption of strong electrolyte ions, activated adsorption, adsorption process kinetics, theories on adsorption process, types of diffusion encountered in adsorption, diffusion coefficients on adsorption, mass transfer on adsorption, mass transfer rate on adsorption, phase contacting methods for mass transfer in adsorption operations, step contacting and fixed layer contacting. This chapter led to the development of a mathematical model in this research and to the choice of the closest calculation relationship that reflects the process of purification of waste oil, using bentonites.

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Fig. 3 Prop technological scheme [10]

5 Methods and Determinations Regarding the Amount of Metal in the Used Oil Two types of oil “Castrol Edge Turbo Diesel 5W40” and “Castrol Magnatec 10W40 A3/B4” were used for the analysis of engine oil residues. The first oil was extracted from an engine of Volkswagen Transporter, year of manufacture 2002, cylindrical capacity 2182 cm3 diesel fuel. The second type of oil comes from a Volkswagen Golf IV car engine, year of manufacture 2004, cylinder capacity 1400 cm3 engine with gasoline fuel. The experiments were performed in the laboratory of the Faculty of Oil and Gas in Ploiesti and I.N. ICEMENERG BUCHAREST. Figure 4 shows two oil samples, before and after their use in the engine. From the analysis bulletin made by I.N. ICEMENERG BUCHAREST on a sample of used oil, there is a low water content, the upper caloric power being 51,365 kJ/kg and the lower 48,186 kJ/kg. The content of carbon, hydrogen, nitrogen, sulfur, oxygen was within normal limits for liquid fuels.

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a

b

Fig. 4 Appearance of oil samples: a crude oil; b used oil

The kinematic viscosity of the used oil was determined at temperatures of 50 °C, 80 °C, 100 °C with values of 4.05 °E, 2.01 °E and 1.52 °E, respectively, the flash point of the used oil was of 152 °C. The analysis of used oil for spark ignition engines (SI engines) and compression ignition engines (CI engines) was performed in the UPG Ploiesti laboratories. The analysis of three used oil samples was performed, both for SI engines (spark ignition engines) and for CI engines (compression ignition engines) in order to bring the samples in aqueous solution in order to find out the level of nickel and iron in them. After an accurate measurement of the used oil sample, it is placed in an oven where it is subjected to a temperature between 700–800 °C (700 °C was used in the experiment). When the oven reaches the desired temperature of 700 °C the sample is left for one hour. A sample comprises a quantity of 5–10 g, during the experiments, for example, sample 1 B had the quantity of 5.81 g. The oven was of the DENKAL type 4. The technical characteristics of the oven are: • • • • •

External dimensions: 370  490  420 mm; Interior dimensions (thermal enclosure 0: 150  130  170 mm; Nominal temperature: 1100 °C; Weight: 28 kg; Rated power: 1500 W.

After one hour when the temperature starts to drop, remove the crucible, and insert it for cooling in the desiccator. Place 5 ml of normal hydrochloric acid 2 over the sample thus obtained, take the crucible from the desiccator, and place it on the sand bath and heat it to a

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temperature of approximately 200–300 °C and leave it until the volume reaches a quarter of total volume. Existing data show that, compared to fresh lubricating oils, waste oils contain large proportions of iron from the wear of moving engine parts. The other chemical elements (calcium, barium, zinc, phosphorus, magnesium) are also found in fresh oil and come from additives. Waste oils are a more attractive raw material for obtaining base oils than the corresponding crude oil fractions because the yield is higher and does not require extraction or deparaffining operations with solvents. However, the processing of waste oils encounters great difficulties and increasingly complex technologies have been developed that take into account the type and degree of impurity of the waste oil. The remaining solution is placed in a volumetric flask over which it is completed with distilled water up to a maximum capacity of 100 ml and stirred until it is observed that no impurities remain. The operation will be applied for the remaining samples, the samples being presented in Fig. 5. After processing the six samples, the concentration of iron (Fe) and nickel (Ni) is analyzed by the atomic absorption method, using the fast sequential absorption spectrometer (VARIAN), by inserting the Fe and Ni lamps inside the device that work separately each of the two elements, the spectrometer being presented in Fig. 6. Oxyacetylene fuel was used in the burner, and in the flame, the sample is atomized, and the absorption is measured according to Lambert–Beer’s law, namely “Absorbance increases linearly with concentration”. Being known the concentration of the standards (samples), the wavelength was chosen according to the concentration. Water solvent is used in the device to measure the amount of metal in it for greater accuracy and precision on the results. The flame ignites, the M1 standard is inserted into the device and the analysis process begins. The spectrometer makes

Fig. 5 Samples completed with distilled water in a volumetric flask up to a capacity of 100 ml

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Fig. 6 Fast sequential atomic absorption spectrometer

three readings within five seconds, but the displayed value is only one, automatically making the arithmetic mean of the three readings. When changing the standards, the spectrometer is cleaned for ten seconds for a more accurate reading of them. “Flame Atomic Absorption Spectrometry Analytical Methods” according to Annex 2 and 3 respectively. The average Ni concentration was 1.11 ml/kg. The transformation from ml/l to ml/kg of metal concentration in oil is performed with the following formula: We note the concentration with C and the quantity with Can based on the formula: C¼

C  0:1 ml
Can  103 kg

Another experiment was done in the ICEMENERG laboratory on the calorific value of used oil and elemental analysis. Table 5 presents the results of all 6 samples analyzed:

Table 5 Test results from used oils

Quantity (g) Nickel concentration (Ni) (ml/kg) Iron concentration (Fe) (ml/kg)

Used oil SI engine B 1 2 3

Used oil CI engine M 1 2 3

5.81 0 148.88

5.15 2.13 220.19

5.5 0 94.9

5.75 0 101

5.87 0.68 127.19

5.75 0.52 117.56

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6 Prerequisites Calorific value was determined on a general analysis sample according to ASTM D240-17. The sample is transported to the laboratory in suitable tightly closed containers. After homogenization of the sample and for an operative viscosity, the sample will be placed in an oven at a temperature of 40 °C. The analysis of the sample is done with the help of a calorimeter brand IKA C2000 which consists of the calorimeter itself and a vessel with cooling water brand IKA-KV600 (Fig. 7). The cooling water temperature must be at a temperature of 19 °C. Take about 3.5 g of used SI engine and CI engine homogenized oil and place in a crucible. The temperature that is released in the crucible is taken over and the bomb is inserted. Insert the weight of the sample on the central panel and start the analysis. Ignition of the sample, duration of combustion, period of heat transfer between the calorimetric vessel and the jacket are set automatically. The crucible together with the sample will be attached to a cotton thread at two electrodes. Insert 1 ml of distilled water. The role of this cotton thread is fulfilled when it is inserted into the “bomb”. The electrodes produce an electric arc that ignites the cotton thread, it falls on the sample and ignites the sample. After the sample is inserted into the “bomb”, the “bomb” is assembled, inserted into the head of the measuring cell, which closes automatically and the combustion vessel with the sample is lowered into the inner vessel. Combustion is done with oxygen, so it is necessary to introduce oxygen from the cylinder into the combustion vessel until the pressure of 30 bar is reached. The water from the cooler circulates through the appliance and is heated to 25 °C.

Fig. 7 IKA C2000 calorimeter and an IKA-KV600 cooling water vessel

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Fig. 8 The “bomb” is automatically assembled and removed from the device after performing the analysis

The magnetic stirrer ensures a uniform distribution of heat in the water in the inner vessel. After the combustion has taken place, the bomb is lifted from the device, removed from its support, and depressurized manually. The duration of the analysis performed by the device is 20–25 min per sample (Fig. 8). The combustion of used SI engine and CI engine oil has a satisfactory combustion, there is no need to add combustion aids. The burning of SI engine waste oil left a few grains of ash, and the burning of CI engine waste oil was a complete burning. For elementary analysis of used oil was used the elementary analysis device EA 1110 (Fig. 9) consisting of basic instrument, universal autosampler (Fig. 7) for liquid or solid samples, electronic microbalance Sartoris XM 1000 P (Fig. 8), computerized unit of control (Fig. 9), carrier gas cylinder (helium) and technical oxygen cylinder (Fig. 10) for pneumatic actuation and pure oxygen cylinder (Fig. 11). With this apparatus, the carbon (C), hydrogen (H) and nitrogen (N) of the waste oil used in the experiment will be determined. As a way of working, a homogeneous amount of waste oil will be used and it will be put in tin capsules, with the help of tweezers, then the sample will be weighed on the electronic microbalance, hermetically sealed, so that it will not be contaminated with nitrogen from air. The amount of used oil should be between 2–3 mg because the calorific value of the used oil was considered normal. The samples were doubled for the experiment. After measuring the weight, take the tin capsule with tweezers and put it in the autosampler. The sample enters a chamber heated to 1000 °C, the process takes 30 s to burn the sample. The gas resulting from combustion is passed through a chromatographic column and read by the computer unit. The helium cylinder of the device has the role of moving the compounds toward the chromatographic column because it is an inert gas.

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Fig. 9 Gas analyzer EA 1110

99.99% pure oxygen cylinder has the role of improving combustion, resulting in complete combustion. The technical oxygen cylinder has a pneumatic role for the movement of the autosampler. The results of the tests are included in Tables 6 and 7.

7 Use of Bentonites in the Purification of Waste Oils from the Transport Industry 7.1

General Aspects

Bentonites are mainly made of montmorillonite, they have a low hardness, are light, have a white color with shades of green–blue, pink, yellow, brown. The granulation varies between 1–500 mµ. The crack is typical conchoidal. The specific weight is between 2.7–2.8 g/cm3, 1.6–1.8 g/cm3. Hydrated aluminosilicates are the formations that make up bentonite, which has a high absorption and ion exchange capacity, this is due to the fact that it is largely composed of montmorillonite. Depending on the degree of crystallinity of the particles, the pore structure, the textural and structural features, the pH and temperature of the solution and the solution-adsorbent contact time, the chemical nature of the sorbent surface, the cation present in the mobile layer, it depends on adsorption capacity and cation exchange.

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Fig. 10 Working scheme of the experiment

Fig. 11 Ash samples of used oil with 20 g, 40 g, 60 g, 80 g, bentonite

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Table 6 Waste oil—gasoline engine No

Characteristic

Measurement unit

Value

Method of determination

1

Lower calorific value, Qi Carbon content, C Hydrogen content, H Nitrogen content, N

10.023 41.96 83.56 13.17 0.41

ASTM D 240

2 3 4

Kcal/kg MJ/Kg % % %

ASTM D 5291–16 ASTM D 5291–16 ASTM D 5291–16

Table 7 Waste oil—diesel engine No

Characteristic

Measurement unit

Value

Method of determination

1

Lower calorific value, Qi Carbon content, C Hydrogen content, H Nitrogen content, N

10.110 42.33 84.12 14.29 0.33

ASTM D 240

2 3 4

Kcal/kg MJ/Kg % % %

ASTM D 5291–16 ASTM D 5291–16 ASTM D 5291–16

The adsorption capacity of bentonite is caused in proportion of 80% by inter-crystalline nature, caused by isomorphic changes in the network and approximately 20% by uncompensated negative electrical charges. In the experiment, bentonite from domestic production was used, namely from Valea Chioarului, Romania. The working scheme of the experiment is presented in the following logical scheme.

7.2

Experimental Research

Within this chapter, experimental research activities were carried out with the aim of highlighting the particularities and performances of the process of burning purified waste oil, from the automotive industry. Their role is to confirm the possibility of carrying out an appropriate spray, followed by a proper ignition and combustion, compatible with the requirements of energy installations. The experiments took place in the Combustion Installations laboratory of the Thermotechnics, Engines, Thermal and Refrigeration Equipment Department of the Faculty of Mechanical and Mechatronics Engineering within the Polytechnic University of Bucharest. The research carried out up to this stage has highlighted the possibility of capitalizing by burning purified waste oil. The efficiency of the combustion plant depends on the judicious choice of the constructive and functional parameters of the injectors used. The characteristics of the spray jet for mechanical injectors with vortex chamber (return) are:

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Fuel flow and its adjustment range; Jet flaring angle; Liquid fuel distribution density; Spray fineness (average diameter and droplet distribution); Maximum diameter of the fuel drop.

These characteristics must be achieved for the well-defined physical properties of the purified oil used: (viscosity, surface tension and density) and at a preheating temperature necessary for a corresponding fluidity (2–3 °E). To determine the kinematic viscosity of the used oil, determinations were performed at temperatures of 50 °C, 80 °C, 100 °C, having values of 4.05 °E, 2.01 °E, respectively 1.52 °E. The flash point of the used oil used is 152 °C. All the characteristics of the waste oil analysis bulletin were performed in the I.C.E.M.E.N.E.R.G. and are found in Tables 6 and 7. From the analysis of waste oils (both from SI engines and from CI engines), the initial concentration of metal ions is between 50 and 200 mg/l. Four (4) classes are required, namely: 50, 100, 150 and 200 mg/g. The equilibrium adsorption capacity was calculated for these 4 classes and the values in Table 8 were obtained. The following experiment was performed at the National Center for Micro and Nanomaterials (C.N.M.N.), the structural analysis laboratory within the U.P.B. It is mentioned that the bentonite used in the experiment was procured from Romania, more precisely from the calcium bentonite quarry from Orașul-Nou, activated by a specific process, having the following technical data presented in Table 9. After mixing, we took the mixture between adsorbed metal ions and bentonite. Mixing time was not monitored in these experiments. The ash test was performed by burning the mixture for 2 h at 815 °C. Subsequently, elementary ash analysis was performed using Agilent 8800 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) equipment (Agilent Technologies, Japan). Prior to ICP-MS measurements, the samples were weighed individually and placed in special TFM tubes. After the addition of 2 ml of nitric acid (HNO3), the samples were digested in a microwave system (Milestone Ethos, FKV, Bergamo, Italy) at 200 °C for 35 min at a maximum power of 1800 W. After cooling, the digestion fluids were diluted with ultrapure water to 25 ml. The measurements were performed for the most abundant isotopes of each element and the results are presented in Table 10. From these analyses, it was possible to draw two graphs in order to choose the best sample for the experiment (Figs. 12 and 13).

Table 8 Initial metal ion quantity and equilibrium adsorption capacity Initial metal ion quantity, mg/l Adsorption capacity, mg/l

50 5

100 10

150 15

200 20

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Table 9 Technical data on bentonite used in the experiment Color

Maximum granulation (mm)

Bulk density (kg/m3)

Moisture

pH

Compression strength (wet) (N/cm2)

Bentonite number

Cream colored

Ø 0.063 • sort B6SA max. 25% • sort B5SA max. 15%

800–850

Max. 10%

Min. 8%

4–5

Min. 0.85

Table 10 Results after analysis of bentonite ash mixed with used oil Sample

Quantity (g)

56 Fe (mg/g)

63 Cu (mg/g)

66 Zn (mg/g)

111 Cd (mg/g)

208 Pb (mg/g)

B B B B B

0.1004 0.1009 0.1005 0.0999 0.1002

41.13 63.24 75.24 71.16 71.93

0.028 0.077 0.058 0.043 0.046

0.19 9.8 10.5 9.4 9.8

0.00067 0.0012 0.00078 0.00091 0.0011

0.154 0.122 0.178 0.101 0.482

20 40 60 80

g g g g

From the presented results it was chosen to perform the calculations and experiments, for 20 and 40 g of bentonite introduced in a liter of used oil. The aim was to make as little bentonite as possible. The optimal mixing time is of the order of minutes (between 10–30 min). Note that the mixture was made with a battery mixer. Obviously, at the combustion plant to be implemented, the mixture in the used oil tank will be coordinated by an automatically operated electrical device.

Fig. 12 Graphical determination of Cu, Zn, Cd, Pb impurities, adsorbed by bentonite

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Fig. 13 Graphical determination of Fe impurities, adsorbed by bentonite

In order to calculate the minimum mixing time between the used oil and bentonite, so as to reach the adsorption capacity at equilibrium with minimum electricity consumption, the following equation [11] was derived in relation to time, obtaining:   dQt V dCt Qe  ¼ m ds ds 0

ð1Þ

Next, the equation was solved [11]. In order to solve the mathematical model, an experimental constant determined by tests and validated by experiments was needed. Adsorption is done from the initial concentration C0 to the equilibrium concentration Ce. The adsorption capacity at equilibrium is given by Freundlich’s isotherm: 1=n

Qe ¼ KF
C0

ð2Þ

where, in addition: Qe is the adsorption capacity at equilibrium, mg/g; KF is Freundlich’s isothermal constant. The equation that describes the variation of the concentration in time: Ct ¼ Ce þ ðC0  Ce Þ eakL s Ct Co Ce akL s

concentration at a given time; the initial concentration of metal ions; equilibrium concentration; volumetric mass transfer coefficient (does not vary over time); period of time;

ð3Þ

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The equation that defines the adsorption capacity at equilibrium Qe is presented below: 1 VðC0 Ce Þ ¼ Qe ¼ KF
C0n mbentonite

ð4Þ

V---Vsolution þ Vbentonite mbentonite Qe KF n

bentonite mass adsorption capacity at equilibrium Freundlich isothermal constant experimentally established constant.

In the next step, certain values were introduced to determine which has the highest adsorption capacity of impurities, depending on the amount of bentonite introduced into the solution. The experimental mathematical calculation was done with the help of a program adapted in Excel, using the equations presented above. The results are presented in Table 11. This table will be presented only 2 graphs for P1 and P5 (Figs. 14 and 15): As can be seen from the experiments and graphs above, at 40 g of bentonite added to a liter of oil, bentonite has the best adsorption and a shorter time for iron (Fe), and for the metals copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), 20 g/l bentonite is optimal. For the experiment, 30 g of bentonite/l waste oil was chosen, in order to have a balance in the adsorption of all metals in the waste oil.

7.3

Research on the Combustion of Waste Oils Purified by Adsorption in Bentonite

In order to obtain a good fineness of the drops formed when using purified oil characterized by kinematic viscosity m = 12–19 cSt, surface tension r = 2.4–2.6 N/m and density q = 830–870 kg/m3, the following connections are recommended between the supply pressure and the outlet diameter: pal  15 bar, for debits Gd  1500 kg/h you can choose the diameter of the vortex chamber, de = 6–7 mm and the converging angle of the outlet nozzle c = 90–120°. Table 11 Optimal mixing time on adsorption Initial concentration of metal ions (mg/l) Adsorption capacity (mg/l) Sample Mixing time with 20 g of bentonite (s) Sample Mixing time with 40 g of bentonite (s)

50 5 P1 2261 P5 1269

100 10 P2 2335 P6 1354

150 15 P3 2409 P7 1456

200 20 P4 2483 P8 1590

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Fig. 14 Variation of metal concentration Ct in the adsorption process for P1

Fig. 15 Variation of metal concentration Ct in the adsorption process for P5

An important feature of the vortex injector, which largely determines its scope, is the size distribution of the droplets formed. Experimental research has shown that the maximum diameter of the droplets in the sprayed liquid is proportional to the radical of the injector scale and inversely proportional to the square root of the total pressure drop in the injector, according to the relation below: dmax ¼ C


pffiffiffiffiffiffiffiffiffiffiffiffiffiffi Mi =Dp

ð5Þ

where: dmax is the maximum droplet size, in lm; Mi—injector scale, in mm2, Δp— pressure drop through the injector (generally equal to the supply overpressure) in bar; C is a proportionality coefficient, which depends mainly on the physical properties of the liquid to be sprayed and the processing quality of the component parts of the injector. For injectors with superior processing quality C = 1500, and for those with medium quality C = 2000. The first step is to calculate the scale of the injector with the relation: Mi ¼

Gd pffiffiffiffiffiffiffiffiffiffiffiffi 0:77
Dp
d

ð6Þ

For low and medium thermal powers (Pt  200 kW) results in an oil flow of approximately 25 kg/h, at a lower calorific value of the oil of 37,000 kJ/kg. Under these conditions the injector scale Mi = 0.288 mm2 (for a Δp = 15 bar). Finally, the maximum diameter of the drop is calculated: dmax

rffiffiffiffiffiffiffiffiffiffiffi 0:288 ¼ 1500
¼ 207 lm 15

ð7Þ

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It can be concluded that a spray nozzle diameter of 0.5 mm is optimal for the combustion plant that will equip the car workshop building, presented in this research. By removing the metal ions, which are found in the largest proportions in the used oil, increases the life of the injector nozzle, which will no longer be impacted by these metal ions, thus avoiding the phenomenon of corrosion. Experimental research consists in the analysis of the burning process of used oil from the automotive industry. This experiment can help depollute the environment by burning used and purified oil in ecological conditions. The experiment was performed on a mixture of waste oil purified with 30 g of bentonite. The tests were performed on automotive waste oil and bentonite purified waste oil, also from the automotive field. The characteristics of the flue gas composition measurements for the fuel waste oil and purified waste oil are summarized in Table 12, using the spray nozzle with a diameter d = 0.5 mm. The temperature values for the experiment flame were determined using the Fluke TiX560 thermal imaging camera. The appearance of the flame jet during the first experiment for waste oil is shown in Figs. 16 and 17 (Table 13). The appearance of the flame jet during the experiment on purified waste oil is shown in Figs. 18 and 19.

Table 12 Waste oil flue gas measurements Sample

O2 (%)

CO (ppm)

CO2 (%)

NO (ppm)

NO2 (ppm)

SO2 (ppm)

NOx (ppm)

t gas (°C)

k

1 2 3

17.3 17.3 17.2

1628 1722 1813

2.7 2.7 2.8

11 14 15

0 0 0

0 0 0

11 14 15

238 238 242

5.68 5.68 5.53

Fig. 16 Appearance of the flame outside the hearth

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Fig. 17 Appearance of the flame with the help of the thermal imaging chamber with used oil fuel, temperature between 860–920 °C Table 13 Flue gas measurements purified waste oil with 30 g bentonite Sample

O2 (%)

CO (ppm)

CO2 (%)

NO (ppm)

NO2 (ppm)

SO2 (ppm)

NOx (ppm)

t gas (°C)

k

1 2 3

16.9 16.9 17.4

1172 1293 1277

3 3 2.6

28 27 20

4 4 4

0 0 0

32 31 24

280 278.3 263.3

5.12 5.12 5.83

Fig. 18 Appearance of the flame outside the hearth

The reduced width of the flame is also represented by the thickness/length ratio, which had values in the range 0.26–0.29 m. The pollutant emissions were within the accepted limits for a low thermal capacity installation.

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Fig. 19 Appearance of the flame with the help of the thermal imaging chamber with purified used fuel oil, temperature between 950–1020 °C

8 Transfer of Waste Oil Purification Technology to an Industrial Installation Based on experimental data obtained in the laboratory, this data is transferred to a real installation, having at its disposal a company dealing with the automotive field (repairs and overhauls of road vehicles). A heating installation will be designed for the two halls of the company, using purified used engine oil. For this purpose, the heat losses of the buildings, the heat demand, the fuel flow were calculated, resulting according to the calorific value. The hall has a metal frame, plated with 200 mm isopan (walls) and 70 mm (roof), respectively. The construction consists of two annexes, with a total area of 222 m2, having a door framed in the common wall that separates the 2 annexes (Fig. 20). Below is the calculation of the combustion plant and the consumption of purified waste oil. The fuel used is a waste oil that has the following analysis with reference to the initial state: C i ¼ 84:5%; H i ¼ 8:2%; Sci ¼ 0:4%; Ni ¼ 1%; Oi ¼ 3:5%; Ai ¼ 1:9%; Wti ¼ 0:5%; Wf ¼ 0%; The following data are also given: • room temperature: t0 = 15 °C g • absolute air temperature: x ¼ 10 kg aer

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Fig. 20 Presentation of the industrial hall on which the transfer of the technology developed in the research was analyzed

Calculation of calorific value Qi ¼ 339
Ci þ 1030
ðSci  Oi Þ  25:1
Wti ¼ 36741:05

m3 N kg

ð8Þ

Calculation of air and flue gas volumes  m3 N V0 min ¼ 0:01
1:867
C i þ 5:6
H i þ 0:7
Sci  0:7
Qi ¼ 2:015 kg Va0 ¼

100 m3 N
V0 min ¼ 9:596 21 kg

Vaum0 ¼ ð1 þ 0:00161
xÞ
Va0 ¼ 9:75 VCO2 ¼ 0:01867
Ci ¼ 1:578 VSO2 ¼ 0:007
Sci ¼ 0:003

ð10Þ m3 N kg

m3 N kg

VRO2 ¼ VCO2 þ VSO2 ¼ 1:58

m3 N kg

ð11Þ ð12Þ

m3 N kg

V0N2 ¼ 0:79
Va0 þ 0:008
Ni ¼ 7:589

ð9Þ

ð13Þ m3 N kg

ð14Þ ð15Þ

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V0gu ¼ VRO2 þ V0N2 ¼ 9:169

375

m3 N kg

V0H2 O ¼ 0:112
H i þ 0:01242
Wti þ 1:242
Wf þ 0:00161
x
Va0 ¼ 1:079

V0g ¼ V0gu þ V0H2 O ¼ 10:248

m3 N kg

ð16Þ m3 N kg ð17Þ ð18Þ

kev ¼ 1:5 k1 ¼ 1:5 k0 ¼ 1:5 tp00 ¼ 15  C t0 ¼ 15  C tc ¼ 35  C Determination of yield The efficiency of the boiler is determined by the relation:  gi ¼ 100  qev þ qch þ qm þ qex þ qrf %

ð19Þ

qm ¼ 0:8% qch ¼ 0% For kev ¼ 1:5 and tev ¼ 160  C ð160  100Þ
ð4197:491  2075:782Þ kJ þ 2075:782 ¼ 3348:807 Ig1:5;160 ¼ 200  100 kg ð20Þ At t0 ¼ 15  C I0aum t0 ¼

1291:123
15 kJ ¼ 193:668 100 kg i c0 ¼ cc
t 0

ð21Þ ð22Þ

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Qev is calculated with the relation:  kJ Qev ¼ ð1  0:01
qm Þ
Ig1:5;160  kev
I0aum t0  ic0 ¼ 3006:456 kg qev ¼

Qev
100 Qi

ð23Þ ð24Þ

qev ¼ 8:183% aantr ¼ 0:90 kJ Qrf ¼ 0 kg qrf ¼ 0% qev ¼ 8:183% qex ¼ 1% gi ¼ 90:017%

Determination of useful heat and fuel consumption gi ¼ 90:017% k0p ¼ 1:5 Qu ¼ 80 kW I0aum 15 ¼ 1291:193
0:15 ¼ 193:679 B¼

kJ kg

Qu kg ð25Þ ¼ 0:00238 s 0:01
Qi
gi þ ð1  0:01
qm Þ
k0p
ðI0aum 15  I0aum t0 Þ

The actual fuel flow is: Bef ¼ ð1  0:01
qm Þ
B ¼ 0:002 Bef ¼ 0:002
3600 ¼ 7:2

kg s

kg h

Bef month ¼ 10:8
8
25 ¼ 1440

kg month

ð26Þ ð27Þ ð28Þ

The above calculations were made in order to find out the heat demand as well as the heat loss. The calculations were made at an ambient temperature of 20 °C, resulting in a heat demand of 80 kW for both halls.

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Three (3) heating solutions for the industrial hall are proposed and the most efficient and economical solution is chosen, namely: • OHA radiant tubing (gas) • Radiant ceiling panels (electric) • Boiler on purified used oil. OHA radiant tubing (gas) The radiation heating system can be used for: industrial halls, warehouses, car services, gyms, high-rise spaces, exhibition pavilions, showrooms, flower and vegetable greenhouses, animal farms, ovens with strictly controlled temperature. The OHA radiation heating system is recommended for heating industrial spaces and spaces with medium and high heights. The flexibility of the system consists in adapting the radiant piping to any requirements regarding its route inside the heated room. The radiant piping can have different configurations, depending on the heat demand and the height of the building, which can be mono-tubular or bi-tubular. The disadvantages of this system are the high installation and maintenance costs due to the fuel consumed (gas). In conclusion, this hall heating system will not be chosen (Fig. 21). Radiant ceiling panels Central heating systems that use local heaters transmit heat, mostly through radiation. Heat transfer by convection promotes the formation of air currents. The warm air rises next to the heater to the top of the room and sets in motion dust particles that largely deposit on the surface of the walls near the heater and the rest is transported to the room. The air circulation is more or less active, depending on the location of the heater. In all cases, the air near the ceiling is warmer than that near the floor (Fig. 22). The disadvantages of this installation are: • a radiant panel does not heat the air: it only heats solid bodies such as furniture, floor or people in the space, but only the surfaces that the radiant panel “sees”.

Fig. 21 OHA radiant tubing (gas)

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Fig. 22 Radiant ceiling panels

• no savings on the electricity bill: for 1 kWh of heat, at least 1 kWh of electricity is consumed. • thermal inertia—practically non-existent. A radiator stays warm for 30–40 min, after the boiler is switched off, the heated floor remains warm for 2–4–6 h, unlike radiant cooling panels. Boiler for purified waste oil One of the great advantages of this heating solution is the production of “clean heat”, using cheap fuel and high performance. The boiler uses a separate suction pump, takes the fuel from the tank, and pumps it safely to the burner, even over long distances. There, it is filtered to 100 µ and preheated to 35 °C in the heat filter. Subsequently, the oil enters the combustion chamber and heats to the desired temperature, which is different depending on the oil used. This is important to have both a good and constant ignition. The fuel is sprayed with compressed air at a relatively low pressure This allows the use of larger nozzles that do not clog, even if they are dirty or semi-fluid oils are used. Both used and purified oils can be used as fuel without too many changes to the burner. All that needs to be done is to mount a dial to readjust the preheating temperature and combustion air according to the fuel used. The used oil boiler is the most economical way to heat commercial or industrial halls, production halls and warehouses. Boilers can be easily equipped with a universal oil burner to be able to use purified waste oil, as it is an economical and environmentally friendly fuel (Figs. 23 and 24). Analyzing all three heating systems in an industrial hall, it is admitted that the heating system based on purified waste oils is the most advantageous and, at the same time, economical choice. The boiler is designed to always maintain a constant temperature, thus reducing fuel consumption. The exhaust pipe is kept clean due to its inclination, the ash is collected in the tray, which must be emptied periodically.

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Fig. 23 Waste oil boiler

Fig. 24 Waste oil boiler burner

Normally, cleaning is done in a few minutes. The installation on which the experiment was made is a Hiton HP-145 used oil boiler.

9 Conclusions The paper aimed to develop a scientific idea on the purification of waste oils in a way that is as economical and environmentally friendly as possible. Following the studies and experiments performed, it was possible to identify several advantages deriving from the waste oil purification process. In general, the pollution of the environment with waste oils can be reduced, if this hazardous waste is capitalized by its purification and reuse in the automotive and industrial fields.

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Although such waste oil purification technology requires organizational, scientific, and economic efforts to be implemented, it can be considered a real success, as it contributes to the protection of the environment and the reduction of pollution facing contemporary society. Another particularly important aspect is that waste oil pollution has a harmful effect on human health, because, through the process of burning this residue, large amounts of heavy metals (iron particles, cadmium, nickel, zinc, lead) are released into the atmosphere through the ash. These, ingested or inspired by humans, can lead to diseases such as cancer, Alzheimer’s, Parkinson’s, arthritis, cardiovascular disease and many more. In other words, used car oil can be considered one of the main sources of pollution today, due to the dramatic increase in the number of vehicles. Through this paper it can be demonstrated that waste oil is an ecological alternative in the field of fuels, also contributing to the reduction of pollutant emissions. From the experiment of burning waste oil and purified waste oil, it was observed, based on data obtained with the MAXILYZER gas analyzer, that carbon monoxide (CO) decreases by about 30% when burning purified waste oil, but at the same time also observed an increase in nitrogen oxides (NOx) by 50%–60%. Thus, it can be concluded that this increase is due to the fact that in purified oils, combustion is better due to the retention of metal ions, and the increase in temperature has led to an increase in nitrogen oxides (NOx). The results were presented in Tables 11 and 12, respectively. It is important to note that NOx emission values are lower than required by law. In particular, attention has been paid to used automotive oil to highlight the composition of impurities. Following the analyzes performed on the used oil, heavy metal residues were discovered, as presented in Tables 11 and 12. Another conclusion from the in-depth study of other waste oil purification technologies currently in use (Revivoil technology, Blowdec technology, Dunwell WFE technology, Prop technology) is that most of them require chemical and physical processes that involve substantial financial costs, thus presenting a major disadvantage. In the scientific approach, we started from Prop technology, the only one that uses clay as an adsorbent, and developed a new technology for purifying used oil. The innovative element of this paper is the use of bentonite, which, although known as a filter material, has never been used in the automotive field as an adsorbent. Certainly, it could be observed that bentonite is a clay, an accessible material, which is found in quite large quantities in Romania, has remarkable characteristics of adsorption of impurities, ion exchange, plasticity, discoloration power, high degree of dispersion and, which makes it even more attractive, is a relatively inexpensive material. Following the theoretical studies on the model of the adsorption process, it became necessary to develop a mathematical model in the case studied, starting

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from the calculation relations [11], more precisely relations (1) and (2), because they best reflected the process of purifying used oil using bentonite. The calculation of the minimum mixing time between waste oil and bentonite, so as to reach the adsorption capacity at equilibrium with minimum electricity consumption, was performed by deriving in relation to time, the equation (2) and of Freundlich’s equation (1), giving rise to a new mathematical model (4), which is another innovative element of the paper. Another conclusion came from the experiment on the analysis of ash resulting from the burning of the residue resulting from the bentonite adsorption process, where it was observed that the sample with the mixture of 40 g of bentonite added in a liter of oil has the best adsorption capacity for iron (Fe), and the sample with the mixture of 20 g bentonite/l of oil is optimal for the metals copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb). In order to have a balance in the adsorption of all metals in the used oil, the sample with the mixture of 30 g bentonite/l used oil was chosen for the continuation of the energy recovery experiments. Thus, at a theoretical level, the combustion characteristics of the fuel jet were determined, and it was concluded that a diameter of the spray nozzle of 0.5 mm is optimal for the combustion plant that will equip the car workshop building. Another aspect found is that by removing metal ions, which are found in large proportions in used oil, it increases the life of the injector nozzle, which will no longer be impacted by these metal ions, thus avoiding the phenomenon of corrosion. Following the experiments performed in the laboratory on used oil and purified used oil, it was found that the flame intensity of purified used oil is higher compared to that of used oil, these results being shown in Figs. 16, 17, 18 and 19. Theoretically, 3 methods of heating the industrial hall were analyzed, namely: with OHA radiant gas tubes, with radiant ceiling panels and with the boiler on purified used oil. Following this analysis, it was concluded that the most efficient heating method from an economic point of view, as well as ecologically for a car service, is the heating through the boiler on purified used oil. At a practical level, the experiment initially performed on a pilot boiler was subsequently applied on an industrial scale, in a hall, which show the following conclusions on emissions from the combustion process: • the CO concentration decreased by an average of 52% when the purified oil was burned. • NOx concentration increased by 57% (from 33 to 52 ppm), due to the increase in the temperature in the hearth when burning the purified oil. It turns out, through these data, that the results obtained from the experiments on the pilot boiler at the Polytechnic University of Bucharest can be found, on another scale, in the industrial installation on the Hiton boiler.

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Bibliography 1. Mihăescu, L., Oprea, I., Prisecaru, T., Negreanu, G., Pop, E., Popper, Pîșă, I.: Valorificarea energetică a uleiurilor vegetale brute, Editura Printech, p. 140 (2011). ISBN: 978-606-521-690-7 2. Oprea, I., Pîşă, I., Mihăescu, L., Prisecaru, T., Lăzăroiu, Gh., Negreanu, G.: Research on the combustion of crude vegetable oils for energetic purposes. Environ. Eng. Manag. J. 8(3), 475–482 (2009), indexat de ISI, Thomson Scientific Proceedings 3. Pișta, A.: Contribuții privind evaluarea și modelarea transferului de poluanți de la depozitele de zgură și cenușă în sol și pânza freatică- pentru evaluarea riscului pentru sănătatea populației, Teza doctorat, U.P.B. (2007) 4. Dragne, M., Pîşă, I., Covaliu, C., Lăzăroiu, Gh.: Nanostructured materials for energy valorisatoin of used oils. In: 7-rd International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Drobeta Tr. Severin, pp. 457–460, 31 May-02 June 2018. ISSN 2359-7941 5. Pop, E., Mihăescu, L., Lăzăroiu, Gh., Pîşă, I., Negreanu, G., Dragne, M.: Energetic characteristics of animal fats waste from tannery for energy production. In: 4-rd International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Vidraru, pp. 475–478. ISSN: 2359-7941, 04–06 iunie 2015 6. http://www.e-automobile.ro/categorie-motor/20-general/144-ulei-motor-sae-w.html. accesat la data 07.03.2016, ora 19:23 7. Rădulescu, G.A., Petre, I.: Combustibili, uleiuri., Editura Tehnica Bucureşti (1986) 8. Alcantara, R., Amores, J., Canoira, L., Fidalgo, E., Franco, M.J., Navarro, A.: Biomass and Bioenergy, vol. 18, p. 515 (2000); [48] (Canakci, M., van Gerpen, J.: (Trans.) ASAE, 42(5), p. 1203, 1999) 9. Lăzăroiu, Gh., Mihăescu, L., Pîşă, I., Bondrea, D., Negreanu, G., Dragne, M.: Researches on the design of a pellets burner of a 150 kW from agricultural waste. In: 4 th Renewable Energy Sources—Research and Business Conference, Wroclaw, Poland (2018) 10. Dragne, M., Pop, E., Covaliu, C., Matei, E., Pîşă, I.: Experiments in use of bentonite for energy recovery of used oils. In: 8-rd International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Târgovişte, 6–8 June 2019. ISSN: 2359-7941 11. Dragne, M., Pop, E., Pîşă, I.: Application of waste oil purification technology on a heating installation of an industrial hall. In: 9th International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Bucharest, 2–3 June 2020. ISSN: 2359-7941 12. Lăzăroiu, Gh., Mihăescu, L., Pîşă, I., Pop, E., Ciobanu, C., Dragne, M., Desideri, D., Simion, G.: Experimental analyze of the hydrogen impact of solid biomass combustion for the development of innovative efficient technologies. In: 4-rd International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Vidraru, pp. 45–50, 04–06 June 2015. ISSN: 2359-7941 13. http://www.rompetrol.com/ro/ecomaster-3. accesat la data : 21/10/2015, ora 19:21 14. Paris: https://www.scribd.com/doc/303864041/Regenerarea-uleiurilor-uzate. accesat la data: 06/09/2020, ora 10:11 (1952) 15. https://ec.europa.eu/growth/toolsdatabases/tris/en/index.cfm/search/?trisaction=search.detail& year=2017&num=313&dLang=RO. accesat 04/10/2020, la ora 10:07 16. Al. Polihroniade: Absorbția Adosrbția, Editura Tehnică București (1967) 17. Prisecaru, T., Adam, A., Mihăescu, L., Pîșă, I., Pop, E., Berbece, V., Dragne, M.: Combustion experiments on a solid fuel with low sulphur content. In: 9th International Conference of Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD, Bucharest, 2–3 June 2020. ISSN: 2359-7941 18. Dragne, M., Pop, E., Pîşă, I.: Technology for purifying waste oils with nanostructured materials for energy purposes. U.P.B. Sci. Bull., Series D, în curs de apariție. ISSN: 1223-7027

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19. Cosmin Dragne: Utilizarea Energetică a combustibililor lichizi regenerabili, Proiect de dizertaţie Bucureşti (2015) 20. Katiyar, V., Husain, S.: Recycling of used lubricating oil using 1-butanol. Int. J. Chem. Sci. R. Soc. Chem. (2010) 21. Kupareva, A., Arvela, P.M., Murzin, D.Y.: Techology for re-refining used lube oils applied in Europe: a review. J. Chem. Technol. Biotechnol. 88, 1780–1793 (2013) 22. Stevens, D.J.: Status and prospects of biofuels for transportation. Proceedings of the Twelfth European Biomass Conference, Amsterdam, 17–21 June 2002 23. Gavrilă, L.: Fenomene de transfer, Ed. Alma Mater, Bacău (2000) 24. Holban, E.: Teoria şi practica EVOP ȋn industria alimentară, Ed. Tehnică, Bucureşti (1981) 25. Isah, A.G., Abdulkadir, M., Onifade, K.R., Musa, U., Garba, M.U., Bawa, A., Sani, Y.: Regeneration of used engine oil. In: Proceedings of the World Congress on Engineering, vol. 1 (2013) 26. Levizzari, A., Voglino, M., Volpi, P.: Refined product in lubricant sectors. Environmentaln Analisis and Economical Evaluations, Tribology 2000—Plus, 12th International Colloquim, Esslingen, vol. 1, p. 1933, 11–13 January 2000 27. Amarfi, R.: Examene: Operaţii unitare ȋn industria alimentară. Ed. Pax Aura Mundi, Galaţi (2001)

Chapter 14

Environmental Impact and Risk Analysis of the Implementation of Cogeneration Power Plants Through Biomass Processing Iliya Iliev and Angel Terziev

Abstract Environmental impact and risk assessment during the implementation phase of large-scale projects in the renewable energy field is a key issue. This chapter shows the specifics in the environmental aspect of the introduction of cogeneration plants through biomass gasification, as well as the significant possible risks in the introduction of such large-scale power plants. The significance of the risk is presented in matrix form, as well as the actions for its reduction are indicated. Keywords Environmental impact assessment


Risk analysis
Cogeneration

1 Introduction Globally, the amount of recoverable waste wood can be defined as very significant —401 Tg dry matter per year (Tg.yr-1) (Chap. 7) [1]. This is the main driving mechanism for the significant evolution of the systems for the utilization of waste biomass [2, 3]. The type of technology using waste wood is very diverse. They are mostly divided into direct use of biomass (combustion processes) and installations for the production of combustible gas during the processing of biomass phase and further combustion in cogeneration units. Biomass processing plants use different technologies for the production of combustible gas, such as processes taking place in the presence or absence of oxygen, and low or gage pressure. In addition, the most common methods in the processing of waste wood are gasification, fermentation, pyrolysis, and others [4–7]. I. Iliev (&) Agrarian and Industrial Faculty, University of Ruse, Ruse, Bulgaria e-mail: aterziev@tu-sofia.bg A. Terziev Faculty of Power Engineering and Power Machines, Technical University of Sofia, Sofia, Bulgaria © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1_14

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The production of the gas itself, as well as its combustion, is associated with the release of various substances and gases that need to be purified or separated before being discharged into the environment. It is necessary to observe very carefully the current environmental norms and standards in the country where the installation will be installed. Already in the process of prefeasibility study, it is necessary to make a very careful assessment in terms of harmful substances and gases emitted into the environment, as well as the efficiency of the respective technology. The main risks related to the implementation of the cogeneration systems can be divided into those that are in the processes of prefeasibility study, incl. selection of appropriate technology taking into account local specifics; risks in the process of construction of the facility and those during its commissioning. It is very important to assess the risk qualitatively rather than quantity and to make a prescription for those risks that are classified as “significant”.

2 Environmental Analysis The waste wood is transported from the storage piles to chipping area using loading equipped with a wood clip. The waste wood is placed on the transport line, and it goes to the chipper machine. Each of the technologies using waste biomass for combined production of electricity and heat must be considered individually, according to the local site specifics. The concerned cogeneration set operating through biomass gasification includes a number of technological systems, and for each system, it is necessary to make the appropriate analysis in terms of environmental impact. Such an approach should be applied not only for this cogeneration plant but to any such type of system. The present system includes the following general equipment: • Wood chipper—initial processing of the raw material. Mobile and local wood chippers can be used to process the biomass; • Dryer—it is used to reduce the initial moisture content of the material in order to meet the gasifier specifics. Optimal moisture content before the gasifier amounted to 15%; • Gasifier—different technologies can be applied—updraft; downdraft; double fire and two stages (Chap. 7); • Syngas treatment system—where the gas is cleaned, cooled and dried; • Syngas combustion systems—cogeneration set is used for simultaneous production of electricity and thermal energy. Environmental impact assessments are not required for the Plants. No special requirements of the installation are outside the protected habitats of birds and plants. If Plant follows the existing environmental regulations, and requirements identified during the permitting process no issues are foreseen.

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During the process of gasification of biomass, a certain amount of odors may emit, especially when the gasifier running at gage pressure. Odor is not expected at the plant where the gasifier design keeps the pressure below the atmospheric pressure. Some solid wastes (e.g., ash) are expected to be generation during the process of operation. The ash will be sold or could be used as a soil amendment. The management authority is responsible for the classification of all wastes generated during the plants operation and makes arrangements for their environmentally sound and legal disposal or utilization. According to the equipment specifications of the cogeneration unit, Table 1 summarizes the air pollutants expected from the generator’s combustion process. To limit air emissions, lean burning combustion is used by the GE/Jenbacher engines to reduce NOx emissions and air purification equipment is installed at each GFP plant. Physical processes are used to clean the exhaust gases. First the combustion gases flow through air-cyclones for separation of the course dust particles. Next, the gasses are fed in an aerosol scrubber. Then they undergo treatment in a wastewater-cooling tower followed by scrubbers with Venturi pipes, spray-type scrubber and filters. According to the Air Purity Regulations, the company must: • Erect a stack with a certain height; • Submit protocols for equipment tests, emission measurements, and operating instructions for the air purification facility to the local authorities; • Establish and conduct emission monitoring; • Establish a program for equipment maintenance of air purification equipment. A very common problem at biomass power plants is foul odors emanating from woodpiles and woodpile heating and at times spontaneous combustion. The fuel yard will have to be carefully managed by entity. Woodpiles cannot be allowed to sit for long periods. Emissions from the Plant area including, waste and chipped wood storage, gasification, wastewater treatment, co-generator operations, must be carefully monitored and managed. The responsibility of the enterprise is to undertake the necessary measures to meet the legal requirements of the Air Purity Act and related ordinances.

Table 1 Summary of the air pollutants emitted by the Jenbacher co-generator Pollutant NOx: Particulate matter Unburned hydrocarbons SOx: Carbon monoxide (CO): Source Jenbacher

Concentration Equipment producer 3

500 mg/Nm (at 5% O2) PM10: 1%, respectively, though the amounts of these elements in MBM mixtures examined previously by Kantorek [49] were, similarly to the case of sample studied by Senneca [29], at the lowest mostly determined levels. Table 1 Physical and chemical properties of MBM Kantorek [49], Kantorek et al. [24] Proximate analysis (% as received) Moisture 5.5 Ash 25.09 Volatile matter 54.08 Fixed carbon 15.33 Ultimate analysis (% as received) Carbon 40.14 Hydrogen 6.81 Nitrogen 6.05 Sulphur 0.21 Oxygen 16.05 Chlorine 0.15 Physical properties 578 Apparent density, kg/m3 652 Bulk density, kg/m3 HHV, MJ/kg 19.18 LHV, MJ/kg 14.31

Senneca [29]

Cascarosa et al. [22, 47]

6.0 20.0 64.0 10.0

1.35–8.3 10.38–38.8 32.7–80.1 2.8–26.1

43.4 6.4 9.2 0.4 – 0.3

31.1–55.67 4.8–8.03 0.4–10.4 0.05–10.9 11.9–38.4 0.26–1.1

– – 15.50 14.47

– – 14.19–37.71 13.06–30.29

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3 Properties of Mineral Fraction of Animal Meal Considering the relatively high ash content in MBM, the detailed characterization of ash becomes vital for estimating its behaviour during combustion in terms of assessing its possible impact on the particulates emissions and on a long-term installation operation. To avoid operational problems related to ash deposition, slagging and fouling on heat transfer surfaces, an attention has to be paid to the elementary composition of non-organic substances that influences the physicochemical properties of ash, thereby affecting the nature of its physical transitions when exposed to high temperatures. In this respect, particularly negative effect is attributed to calcium which is the dominant mineral element, as well as to magnesium, sodium and potassium. It has been proved that bone meal ash has higher contents of calcium and phosphorous [49, 53, 55] compared to meat meal ash. The studies of Kantorek [49], as shown in Fig. 2, have indicated the calcium percentages of 54% and 37% for bone and meat meal ashes, respectively, whereas the contents of phosphorous were identified at 18% and 12%, respectively. On the other hand, bone meal ash proved to contain less magnesium (4%) than meat meal ash (9%). The alkali (Na and K) are considered to substantially reduce the temperature of ash softening, and thereby they are of major concern with regard to the formation of fireside deposits [56]. According to measurements (Fig. 2), meat meal ash contains less sodium (9%) and far more potassium (16%) compared to bone meal ash (11% and 7%, respectively). Crucial for environmental reasons is to ensure the possibly lowest contents of combustibles in the ashes. In the context of MBM combustion, importance is thus to determine the characteristics of ash behaviour, including the temperatures of sintering, softening, melting and flow. Studies of animal waste samples, namely pure meat meal (MM) and bone meal (BM) derived from pigs, cattle and poultry, and a mixture (MBM) of those (50%/50% by weight), coming from one of the Polish meat-processing companies (Zakłady Przetwórstwa Mięsnego “Ostrowite”) [24], have shown that in the case of meat meal these temperatures exceed 1000 °C and are far higher (of *200 degrees) than for the bone meal. Consequently, large

P 12%

Al 1%

Si 4%

Na 9%

Fe 6%

Zn 5%

P 18%

Cu 1% Mg 9%

K 16%

Si 3%

Al 2%

Fe 1%

Mg 4%

Na 11%

K 7%

Ca 54%

Ca 37%

(a) Fig. 2 Ash composition of meat meal (a) and bone meal (b) [49]

(b)

422 Table 2 Chemical composition of MBM-derived ash (wt% ash base) [48]

M. Kantorek et al. SiO2 Al2O3 Fe2O3 CaO 5CaO3Al2O3 K2SO4 CaSO4O5H2O MgO Na2O K2O CaSO4 P2O5

2.81 1.54 0.50 22.01 6.44 13.02 22.37 2.09 0.36 1.68 11.48 15.70

share of bone meal contributes to lowering the MBM transition temperatures. This was evidenced by the measurements for investigated MBM, which were 840 °C (sintering), 880 °C (softening), 1010 °C (melting) and 1020 °C (flow). Additionally, since MBM is regarded as a waste fuel, special attention is given to the ash quality to recognize any potentially harmful environmental effect of its disposal. Numerous studies have proved the MBM ash to be a valuable combustion by-product with fertilizing properties due to significant contents of phosphorous, calcium, magnesium and potassium compounds [29, 30, 33, 53]. For instance, the results of Deydier et al. [53] show the MBM burning residues to be rich particularly in phosphates (56.3%) and calcium compounds (30.7%) that is due to bone fraction, the mineral matter of which consist of calcium phosphates in general, basically in form of hydroxyapatite [54]. Similar trends have also been evidenced by the analysis of an average ash composition that remained after the staged meal incineration in a pilot large-scale installation [48] (see Table 2). The derived ash featured high contents of CaO (22.01%) and P2O5 (15.7%). The quantities of other minerals in form of oxides, i.e. K2O, Na2O, MgO, etc., though smaller, were also identified.

4 Sub-processes of Thermal Conversion There is limited number of works devoted to the analysis of particular mechanisms, accompanying the thermochemical conversion of MBM, such as kinetics of drying and thermal decomposition, the yield and composition of pyrolysis products and the combustion kinetics. The characteristics of MBM drying were analysed, for instance, by Jesionek et al. [13], whereas the kinetics of its pyrolysis by Senneca [29], Ayllón et al. [57], Karcz et al. [58] and Jesionek et al. [59]. Also, very few researches can be found to date that covers the investigation of MBM combustion kinetics [27, 29]. Moreover, they basically focus on the oxidation of solid fraction. The literature review shows the lack of extended process examination that takes

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account of the combustion in a gas phase, though it influences the fuel-burning behaviour and the process pattern. The main reason behind this is the complexity of homogeneous reaction mechanisms.

4.1

Drying

Drying is an initial stage of thermal utilization, and it strongly affects the overall process course [60, 61]. The heat of water evaporation is quite large (*2.26 MJ/kg at atmospheric pressure). Therefore, it is of importance to determine the demand for additional energy while implementing the process of animal meal drying. The question to be answered is what the delay time is resulting from the moisture release out of a material. This, in consequence, directly leads to estimation of whether the raw animal meal should undergo preliminary drying prior to combustion process. The results of detailed experimental studies on meat-and-bone meals with regard to the dynamics of moisture release demonstrated that the drying time is proportional to the moisture content [24]. The test series, aiming at estimating the influence of temperature and time on a meal drying rate, was performed with the use of specially developed dedicated muffle stove with gas flow. The duration time of moisture evaporation was evaluated by measuring the composition of post-process outlet gases. The process completion time was represented by the time of a sudden rise in the concentration of CO2 yielded from the process of desorption. At higher process temperatures, the time of moisture release completion was estimated as the one corresponding with the observed upsurge in CO content in the analysed gas. The meals were examined within the wide range of sample size fraction, i.e. between 60 and 5000 lm. The investigation clearly showed that the amount of time needed to achieve an equilibrium state in a material depends on the size fraction and the type of morphological form. In the case studied, this state refers to temperature of 105 °C (analytic moisture measurement according to PN-64/G-04511 standard). The measurements for 15 g samples featuring the initial moisture content of 31.84% revealed that the times of free (unbound) moisture evaporation are longer for *8–10 min for the meat meal as compared to the bone meal, depending on the granulation. Therefore, the greater the meat mass fraction would be in the MBM, the longer would be the drying time of the mixture. For the examined 50%/50% meal mixture the evaporation times appeared to increase with an increase in a sample size fraction, attaining *33 min for the largest sample granulation, i.e. 5000 lm. This translates into the time and the rate of a total moisture release from the fuel sample. The results of experimental research demonstrated longer times for meat meal for any process temperature between 200 and 1000 °C [24]. For temperatures below 400 °C the drying time decreased relatively fast, from *98 down to *25 s for meat meal and from *42 down to *15 s for bone meal. For temperatures above 400 °C, these times gradually shortened heading asymptotically for a value characteristic for a given sample, i.e. *9 s and *4 s for the meat-and-bone meal,

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respectively. Simultaneously, regardless of a meal sample type, the rate of complete evaporation within the temperature range of 200 and 800 °C increases quite steadily; however, the most notable rate change was identified for the bone meal, as shown in Fig. 3. When exceeding 800 °C the rates asymptotically approach the values for specified samples, which are *1 g/s, 0.66 g/s and 0.8 g/s for the meat meal, the bone meal and 50%/50% MBM, respectively.

4.2

Pyrolysis

The determination of the pyrolysis gas composition permits to predict the efficiency of thermal decomposition and the possible ecologic threats. Pyrolysis gas derived from animal meal is composed mostly of CO, CO2, H2, CH4 and C2H4. Other components, including hydrocarbons such as C2H6 and heavier ones CnHm (i.e. C3H8 and C4H10), as well as H2S, constitute the minority, reaching the content levels of several per cent each, particularly at higher process temperatures. The gas analyses carried out for various pyrolysis temperatures [24] showed similar trends in the evolution of concentrations of particular compounds regardless of a sample type. Namely, the CO and H2 contents increased with the process temperature rise (Table 3). The change in C2H4 fraction followed the same tendency, except for the decomposition at 1000 °C that resulted in a slight C2H4 content decrease. It was observed that the percentages of other identified hydrocarbons reached their maximum levels at different temperatures. In the case of a meat meal these were, for instance, 600 °C for CH4, 400 °C for C2H6 and 500 °C

Fig. 3 Rate of complete evaporation depending on the process temperature and a sample type [24]

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Table 3 Pyrolysis gas yield and the main gas components (%vol.) for various process temperatures [24] Sample type

Yield, %

Temperature, °C

Component CO CO2

H2

CH4

C2H4

MM

69.1 78.2 83.2 86.7 87.4 87.4 23.1 32.9 44.7 47.6 50.8 51.9 46.1 55.5 63.9 67.2 69.1 70.0

500 600 700 800 900 1000 500 600 700 800 900 1000 500 600 700 800 900 1000

42.50 33.40 31.00 30.50 30.00 30.00 48.00 37.00 35.50 35.00 34.50 34.50 45.25 35.20 33.25 32.75 32.25 32.25

10.50 18.00 23.50 26.00 28.00 28.50 8.50 15.05 20.00 21.00 21.50 22.00 9.50 16.53 21.75 23.50 24.75 25.25

8.05 12.50 10.50 8.50 8.30 8.00 4.50 9.05 10.05 8.05 6.50 6.00 6.28 10.78 10.28 8.28 7.40 7.00

1.85 3.10 5.40 7.55 7.45 7.30 1.75 2.95 4.35 6.00 7.40 7.20 1.80 3.03 4.88 6.78 7.43 7.25

BM

MBM

9.00 12.00 13.50 14.00 14.50 15.00 11.10 13.50 14.50 16.00 16.50 17.00 10.05 12.75 14.00 15.00 15.50 16.00

for CnHm [24]. For bone meal these maxima were, in general, shifted to higher temperatures, and the peak concentrations were obtained at 700 °C for CH4 and at 600 °C for C2H6. Whereas the maximum of C2H2 content was recorded at the process temperature of 500 °C.

4.2.1

Release of Volatile Compounds

It is commonly accepted that the chemical composition of a raw material and the thermal regime of a thermochemical conversion are the basic factors determining the process course, and the yields and the quality of products [61, 62]. The detailed studies [24] indicated the differences in the characteristics of pyrolysis of individual animal meals, i.e. MM, BM and MBM, namely in terms of the heating rate, the start time and the duration of devolatilization. Relatively large differences may be observed with regard to the heating rates. The experimental data showed that the heating rate notably increases for process temperatures exceeding 600 °C, in particular for the meat meal. The rate thus changes from 10 K/s at 300 °C, through *120 K/s at 600 °C and up to 1250 K/s at 1000 °C. The heating rates for the bone meal and MBM demonstrated rather moderate variation, changing within the entire temperature range from 7.7 K/s to 305.7 K/s and from 9.1 K/s to

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500 K/s, respectively, as shown in Fig. 4. The study also revealed that the quantity of organic substance of a meal which decomposes into the gaseous constituents during fast heating is about 10–20% larger than the amount of volatiles that evolved under low heating rates. This was observed for the case when the adjusted process temperatures exceeded 700 °C. The rate of heating becomes then sufficiently high that the thermal mechanism of organic material degradation may alter, which results in yields of hydrocarbon gas larger compared to the specified by the carbon standard (PN-G-04516:1998) [63]. In addition, the evolution of hydrocarbons is accompanied by a release of a great number of carbon atoms, which are detached from the crystal networks and agglomerate forming an amorphous structure of soot. Measurement results demonstrated that the main organic mass of a meat meal undergoes thermal decomposition at temperatures below 500 °C, whereas for meal derived from the bone tissue this temperature limit is shifted towards 600 °C. Moreover, the decomposition of organic matter is completed at 800 °C for meat meal, and at temperatures exceeding 1000 °C for bone meal. Additionally, the highest gas yields are obtained for meat meal processing and show to be almost double the yields for the bone meal at the temperatures above 700 °C (see Table 3). Obviously, the measured amounts of pyrolysis gas from MBM are found intermediate resulted from the mass fractions of the meat-and-bone tissues in the meal. The thermal behaviour contributes to both, the start time and duration of devolatilization. The volatiles release begins with the desorption of CO2 from the surface of meal grains. This compound thus constitutes the majority (>80%vol.) of pyrolysis gas at this process stage. The start time of pyrolysis reduces with an increase in process temperature, however, appeared to be the shortest for the meat meal (Fig. 4). For pyrolysis temperature exceeding 600 °C, this time for the bone meal is nearly twice as long as for the meat meal. At lower temperatures, i.e. below

Fig. 4 Heating rate and the start time of devolatilization versus process temperature for various sample types [24]

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600 °C, these differences appeared to be considerably smaller. The longer start times of decomposition observed during tests with bone meal samples are mainly due to the high contents of mineral matter components, such as hydroxyapatites and carbonate apatites. The minerals forming ash amounts to 39.5% of mass in the case of bone meal, whereas for the meat meal they are found to constitute only 2.1%wt. The mineral parts are the basic components of a bone meal, and organic elements built into their crystallographic structure are released at higher temperature range as compared to the meat meal, i.e. far above 600 °C [49, 64, 65]. The start time of MBM decomposition is close to the one estimated for the meat meal, which is particularly evident for low temperatures. This similarity may be related to the desorption of CO2, the course of which in the case of low pyrolysis temperatures is to a less extent dependent on the type of material. As far as the duration time of devolatilization is considered, the measurements showed that for pyrolysis temperatures below 500 °C, the total time of gas release from the animal meal increases with the decrease in process temperature. They also proved the bone meal to decompose longer than the meat meal and MBM. This refers to the process at any temperature, as well as for any granulation size. However, clearly larger times of a complete thermal decomposition (full decomposition of organic and non-organic substances) for the bone meal as compared to the meat meal and MBM were obtained at the process temperatures ranging between 600 and 900 °C (Table 3). Furthermore, the results indicated that an increase in the grain size lengthens the time needed for the pyrolysis gas release to be completed [24]. Simultaneously, an influence of the meal granulation demonstrated greater influence on the total time of pyrolysis for lower process temperatures, e.g. for 500 °C, especially when the size fraction exceeds 1000 lm. This is probably due to lower heating rates recorded for lower process temperatures (see Fig. 4). At temperature of 1000 °C, the devolatilization time for the meal derived from meat tissue hardly depends on the granulation, and for the bone meal, the size fraction to a small extent affects the process duration time. At 800 °C, the granulation has relatively small effect on the time of release of volatiles from the meat meal, whereas in the case of the bone meal processing the influence of this parameter is more pronounced, reflected in devolatilization time extension from 6.5 to 14 s over the entire range of granulation.

4.2.2

Thermal Effect of Decomposition

From the point of view of implementing the efficient technology for thermal utilization of any organic material, importance is to estimate the possible energy generated/consumed during the chemical reactions between the volatiles (hydrogen and carbon compounds) and organic oxygen. The nature of decomposition reactions for meat-and-bone samples was previously identified by means of temperature measurements inside the considered samples, assuming that it represents the temperature of thermal degradation (chemical reaction temperature) of a material (Tr) [24]. The mechanism of thermal

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decomposition for adjusted process temperature (Tp) was thus estimated according to the scheme: 

Tr [ Tp Tr \Tp

! exothermic ! endothermic

ð1Þ

These relations (Eq. 1) mean that the rise of the inner sample temperature above the set pyrolysis temperature is due to the combustion process that occurs with the participation of organic oxygen, and the drop in the temperature inside a sample below the processing temperature is attributed to endothermic reactions that involve mainly the mineral components of bones. The results obtained for the meat tissue and bone tissue indicated similar temperature evolutions for both morphological forms of a meal (Fig. 5). Noticeable differences are however observed in the temperature level achieved and the rate of temperature rise inside a sample.

Fig. 5 Relation between the inner temperature of a sample and the decomposition temperature versus process duration time: (a) MM, (b) BM [24]

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It is noteworthy that the curves demonstrate a significant increase in the temperature inside a sample for the specified pyrolysis temperature. This effect reproduces the process stage directly following the moisture release from the organic matter and is due to increasing rate of the oxidation reaction that accompanies the sample decomposition. Further into the process, the temperature gradually decreases converging towards the ambient temperature. According to Eq. (1), it becomes evident that when the reaction temperature Tr and the process temperature Tp converge and stabilize at this level, with the sample mass remaining unchanged at the same time, the thermal decomposition of a material is completed. These measurements thereby allowed to define the total duration time of pyrolysis for individual samples depending on the process temperature and the morphological type of a meal. Meat meal demonstrated the longest time of a gas release within the wide range of studied temperatures, with thermal decomposition proved to be completed at temperatures exceeding 800 °C. The results also confirmed that for bone meal the decomposition process ends above 1000 °C. As regards the MBM, the process temperature that was recognized to represent the complete thermal degradation was 900 °C.

4.3

Combustion of Volatiles

Based on the diffusion theory describing the combustion of volatile compounds [66, 67], it is assumed that the main factor that determines the duration time of oxidation of the combustible gaseous components is the rate of formation of a pyrolysis gas mixture. The gas combustion zone is then defined as a surface at which the concentrations of the released gases and supplied oxygen after the oxidation drop down to zero and is referred to as microfront (Fig. 6). Furthermore, the reactants are considered to attain a combustion zone with a stoichiometric amount. The diffusional volatile combustion may then be described by an elementary model that involves an extended stationary model for fuel drop combustion, while considering the following assumptions: Fig. 6 Scheme of diffusive flame (microfront) [68]

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• the material decomposition proceeds at a constant rate, • gas oxidation takes place around the grain on the spherical surface, • the process is isothermal, and the combustion and ambient temperatures are the same, • volatile components burn to CO2 and H2O.

4.3.1

Combustion Time

The time of volatiles oxidation sV may be expressed as: sV ¼

1 ðd=2Þ2
qdaf
V daf a 
Y1 3 D
qdaf a;g
b þ Yf ;s

ð2Þ

3 where d [m] represents grain diameter, qdaf and qdaf a a;g [kg/m ] denote the reduced densities of a grain and the released volatiles, respectively, and V daf is the volume fraction of pyrolysis gases in a combustion mixture. Parameter D [m2/s] is the diffusion coefficient, Y1 and Yf ;s are the mass fraction of oxygen in an atmosphere and the mass fraction of pyrolysis gases in a combustion mixture, respectively, and b defines stoichiometric air-to-fuel ratio. As it was shown by experimental studies on the kinetics of combustion, performed for single grains of MM and BM in a horizontal kiln [24], the burning time of volatiles in general coincides with the duration time of meal devolatilization (see Fig. 7). It shall however be noted that pyrolysis takes place on a surface of a meal grain, whereas the volatiles are considered to be combusted at the microfront, which is formed in a space surrounding the grain. The surface area of reaction determines the equilibrium conditions between the combustion rate of a gas mixture and the rate of mixture formation. Thereby, the surface size of the burning microfront around the meal grain is limited by the rate of formation of the combustible mixture of hydrocarbons and air. The measurement results have clearly demonstrated that burn-out time of the released volatiles lengthens with an increase in a particle size and with the decrease in the process temperature. However, the relatively small reduction in the combustion time of pyrolysis gas mixture with an increasing process temperature, observed at temperatures above 800 °C, suggests that the process could be controlled by physical processes related to the rate of transport of the reactants and the formation of the combustible mixture.

4.3.2

Temperature of Combustion

The density of the released gaseous stream is considered to be similar to the density of the generated heat, which may be evaluated, inter alia, by the temperature estimation at the combustion microfront that is emerged around the meal grain.

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Fig. 7 An effect of grain diameter on volatiles burn out time for various decomposition temperatures: (a) MM, (b) BM [24]

Concerning the surface of a microfront to be formed close to the stoichiometric one, the burning temperature at the microfront can thus be treated with great probability as the theoretical combustion temperature of the resulting gas mixture. Test results revealed that burning temperature of volatiles strongly depends on the meal morphological type [24]. In general, the smaller the diameter of a grain, the lower the process temperature. Decrease in the size of the burned grains exerts a greater impact on the volatiles combustion than the reduction of a combustion chamber temperature within the considered range of particle size. However, the peak temperatures of combustion of pyrolysis gas from bone meal (BM) grains are lower than those observed for the meat meal (MM) grains by about 200 K. For the MM samples combusted in a chamber adjusted to a temperature of 1200 °C, the temperature of a combustion microfront exceeds 2000 °C (see Fig. 8a), whereas for the BM samples this temperature is *1850 °C. The experimental data also proved the grain size fraction smaller than 500 lm to have clear influence on the microfront temperature for both, the MM and the BM samples. Simultaneously, for grains larger than 700 lm in diameter, the impact on the gas oxidation temperature is less visible. On the other hand, within this grain size range, the microfront combustion temperature of volatile compounds is significantly affected by the temperature of combustion chamber (adjusted temperature of decomposition process). It is worth noting that this effect is particularly evident at lower chamber temperatures and is more noticeable for BM samples, as shown in Fig. 8b.

4.3.3

Mass Burning Rate of Volatiles—Determination of Kinetic Constants

To determine the mass combustion rate of pyrolysis gas compounds, the following assumptions are made: • the combustion microfront surface surrounding the grain is spherical in shape, • the released volatiles are burned completely at the microfront,

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Fig. 8 An effect of grain diameter on an average combustion temperature for various decomposition temperatures: (a) MM, (b) BM [24]

• the duration time of gas mixture oxidation is equal to that for a grain decomposition. Given the combustion time sV (Eq. (2)), an average mass rate of pyrolysis gas C at the microfront can then be determined from the equation: burning KS;g C KS;g ¼

d
qdaf mg d3 a;g daf ¼
d ¼ Sf ;av
sV 6
df2;av
sV a;g 6
u2f
sV

ð3Þ

where mg [kg] denotes mass of pyrolysis gas, Sf ;av [m2] is an average grain surface and df ;av [m] is an average diameter of microfront. Coefficient uf stands for the ratio of an average microfront diameter to the outer grain diameter. It has been experimentally demonstrated [24] that mass rate of gas combustion is strongly influenced by both, the morphological type of a meal and the burning temperature, in particular for small meal particles. The impact of these factors decreases with an increase in a grain size and becomes negligible for grains of diameters larger than 600 lm. Considering the size distribution of meal samples, the combustion microfront temperature may be determined as a weighted average of values measured for varying grain dimensions (see Fig. 8). This burning temperature thus showed to change from *1400 to *1850 °C for meat meal sample (the majority of grains 50–200 µm in diameter) and corresponded with a linear increase of mass rate from *1  10–4 to *2  10–4 kg/(m3s), respectively. For bone meal sample (basic fraction of grains sized 200–1000 µm), this temperature varied between *1270 and *1780 °C, being related to the combustion mass rate almost linearly increasing from *2  10–4 up to *1.22  10–3 kg/(m3s). Another fact is that homogeneous combustion of gaseous pyrolysis products may occur separately or may be accompanied by the char oxidation. The governing factors in this regard are the size of a grain and the morphological type of a meal. As shown hereinafter (Sect. 4.4), the volatiles combustion stage plays a considerable role in the ignition of meal grains, especially in the case of small grains (d < 400 lm). This has been experimentally observed in particular for the bone

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Fig. 9 An effect of grain diameter on the char burn out time for various decomposition temperatures: (a) MM, (b) BM [49]

meal samples that appeared to be characterized by much longer firing times (see further Fig. 9). However, for bone meal grains smaller than 150 lm in diameter, oxidation of pyrolysis gas mixture takes place rather occasionally. Using the Arrhenius equation [68] to describe the rate of volatiles combustion: 

 E K ¼ k0 exp ; RT

ð4Þ

C

the apparent values of kinetic constants E and k0 (or mass kinetic constants ES and kS;0 ) may be determined, assuming they are constant for a given reaction system and that the reaction mechanism remains unchanged within the temperature range representing the individual combustion stage. Given the mass transfer of oxidant and the reaction kinetics, the apparent mass activation energy ES is thus determined from equation: ES ¼ R


ln KSC1  ln KSC2 ; 1 1 T2  T1

ð5Þ

where KSC [kg/(m2s)] is the mass rate of combustion, and R [kJ/(kmol
K)] and T [K] represent the universal gas constant and the temperature, respectively. Coefficients k0 or kS;0 may be directly determined from the Arrhenius equation: ln kS;0 ¼ ln KSC þ

ES ; R
T

ln k0 ¼ ln K C þ

E ; R
T

where K C [1/s] represents the rate of combustion, defined as:

ð6Þ

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Table 4 Kinetic constants for combustion of volatiles from meat meal (MM) and bone meal (BM) [24] k0 E

1/s kJ/mol

MM

BM

7.219E–03 22.036

0.456 47.197

KC ¼

KSC d
qdaf a;g

:

ð6aÞ

Similarly, E [kJ/mol] is an activation energy: E¼

ES d
qdaf a;g

ð6bÞ

and k0 [1/s] defines the frequency constant given in the form: k0 ¼

kS;0 d
qdaf a;g

ð6cÞ

Obviously, the change in reaction mechanism due to combustion temperature increase results in the change in the kinetic constant values, i.e. the activation energy E and the corresponding coefficient k0 . These values, obtained for combustion of MM- and BM-derived volatiles, are given in Table 4.

4.4

Combustion of Char

Char combustion is strongly influenced by volatiles burning stage. It reveals from the experimental investigations [49] that meal grains combusted under devolatilization stage ignite much faster than those ignited directly. An effect of gas-phase burning on ignition of char particles is expressed by an increase in the reactivity and the temperature of a reaction surface. Thereby, since the combustion of solid phase is a heterogeneous process that is dependent on the activity level of its surface, porosity, including the fraction of open macro-pores, etc., these two factors are of importance for a meal grain ignition. Char remaining after the release and combustion of volatiles has a structure entirely different from the one of a raw material. This regards both, the shape and the size of grains, and the inner structure of particles, namely the porosity, the crystalline structure and reactivity. Combustion takes place on the outer and the inner surface of a grain, and it depends on a grain size and process conditions. Burning of small char particles, less than 200 lm in diameter, may take place throughout the lot volume, and the reaction relocates towards external surface with a diameter increase.

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4.4.1

435

Combustion Time

The change of burn out time of char formed after the devolatilization of organic material (including the grain heat up, ignition and volatiles combustion), dependent on a particle size and for various process temperatures is shown in Fig. 9. The presented results refer to fast pyrolysis of separate meals from meat-and-bone tissues, clearly demonstrating that the burning rates of char obtained from the meat meal are about 20 times higher compared to the rates identified for bone– meal-based char. For grains larger than 1000 lm these differences approach 30 times.

4.4.2

Temperature of Combustion

The change in trends of char combustion temperature with a particle size is similar for both morphological meal types, but the values of burning temperature are higher for a meat meal [49]. The nature of burning temperature evolution of a meal-derived chars results from the course of oxidation of carbon structure. In the case of meat meal char, it consists of nearly 100% of loosely arranged carbon graphite sheets, whereas in the case of bone char the graphite sheets are impregnated by ash mineral matter, which significantly slows down the oxidation of carbon contained in a grain. Figure 10 shows the impact of granulation size and the process atmosphere temperature on an average combustion temperature of meat and bone char particles (Fig. 10a, b, respectively). It shows that burning temperature of a meat meal char is affected equally by the size fraction and the combustion chamber temperature. At 1200 °C, the burning temperature of a meat meal char reaches 1720 °C. An increase in combustion chamber temperature from 1000 °C up to 1200 °C leads to an increase in char burning temperature by approximately 90–130 K. The maximum oxidation temperature measured for bone char grains is 1500 °C, which is lower than the one recorded for meat meal char by *200 K.

Fig. 10 An effect of grain size on an average combustion temperature of char for various decomposition temperatures: (a) MM, (b) BM [49]

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It shall additionally be noted that for particles larger than 2000 lm an influence of grain size on a burning temperature appears negligible at each process temperature.

4.4.3

Mass Burning Rate of Char—Determination of Kinetic Constants

The rate of solid-phase combustion depends on its chemical affinity for oxidant. And the affinity is determined by the physical structure and chemical composition of combustible grain substance. Microscopic research of meat meal char particles revealed that loosely arranged carbon sheets the char is composed in its majority feature high porosity, e  85%, and the strongly developed surface. As mentioned previously, bone char has quite another structure, the core of which is constituted by mineral compounds of calcium, potassium, phosphorous, sodium and magnesium. It is characterized by a dense structure and a porosity of e  34%. An average mass rate of char combustion for a given burning time sc may be expressed as follows: d
qdaf 1 d 3
qdaf 1 a;c a;c C
KS;k ¼
¼ 2
s 2
s 6 Ku
dc;av 6 K
u c u c c

ð7Þ

where uc and Ku denote the grain dilation and the shape factors, respectively, whereas qdaf a;c is an apparent density of char combustible substance. The latter may be experimentally determined using the relationship: qdaf a;c ¼


 1  Ad
qda
qA  daf
1  Vgp d d qA  A
qa

ð8Þ

where Ad represents ash content (%wt, dry basis), qda the apparent density of a meal (dry basis), qA the apparent density of a mineral substance, qA ¼ 2:6 g=cm3 and daf the content of volatiles (%wt, dry basis). Vgp Factor uc is defined by the ratio of an average char grain diameter to an initial meal grain diameter, thereby determines the surface of heterogeneous reaction of char particle burning. The kinetic constants for char combustion, obtained based on Arrhenius equation (Eq. 4) following the procedure applied in the case of volatiles burning, are shown in Table 5. Table 5 Kinetic constants for combustion of char from meat meal (MM) and bone meal (BM) [49] k0 E

1/s kJ/mol

MM

BM

0.201 17.159

0.284 20.024

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5 Staged Combustion of MBM The considered staged combustion [69, 70] consists of separating the main process stages of thermal treatment. The technology uses the rotary reactor to pyrolyze the feedstock material and the fluidized bed chamber to combust the pyrolysis gas and the remaining char. It thereby, regardless on whether the utilized waste fuel is hazardous or non-hazardous, shows itself as an environmentally safe method of thermal conversion resulting in flue gases free from any toxic compounds such as dioxins and furans. An important benefit from the staged incineration technology is the ability to control the individual stages of thermal degradation. This refers to the chemistry of a process, i.e. an elementary composition of a reactive atmosphere, as well as to the thermal regime, namely the characteristic process temperature range. The main advantages of the implemented solution that contribute to the overall system performance are: • fuel homogenization, prevention from sintered fuel deposition, and enhancement of efficiency of drying and devolatilization processes due to feedstock movement in a rotary pyrolizer, • good mixing of a solid post-pyrolysis residue in a fluidized bed chamber, • controllability of a combustion rate, • residence time for heavier combustible fractions sufficiently long to provide their complete burnout, • possibility to introduce sorbents to reduce pollutants. The technology thus enables to utilize the biodegradable waste containing up to 90% by weight of moisture in total, under stable process conditions and at maximum possible (optimum) thermal efficiency, while preserving high levels of environmental and health protection and, additionally, the optimum economical effect. It may be dedicated to incinerating biomass of different kinds but, crucially, the wide range of organic highly wet waste materials, such as the animal waste, the sewage sludge and the municipal solid waste. The physical structure of waste to be thermally processed may be either solid or in form of a pulp or a dense slurry. The combustion process is supplemented with the liquid or gas fuel. The amount of auxiliary fuel depends on the moisture content in a base (waste) fuel and ranges within 1.5–7.0% of a feedstock mass. However, having regard to the concept of sustainable development, the preferable solution is to use the renewable resources as supporting fuels. The required minimum quantity of a feedstock material for which the installation can be operated is 20% of its nominal efficiency, while the maximum reaches 150% for a material of 80% moisture content. The incineration takes place under conditions, which follow the relevant stringent requirements included in directives and regulations regarding the safe utilization of organic waste. Namely, the process is carried out at temperatures higher than 850 °C, with oxygen content exceeding 8% and the residence time longer than 2 s. The reported method of thermal conversion is a continuous-type process that proceeds in a system of integrated devices. They are equipped with control and

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measurement instruments for reading local parameters and remote transmission of signals to control units. Automatic control utilizes the prescribed operation algorithm. The control system covers the course and visualization of a technological process, data logging of operation parameters and recorded events, as well as monitoring of the parameters of process by-products, i.e. the solid (ash) and flue gas. The system thereby enables direct and immediate interference with the process progress in order to preserve the required operation parameters.

5.1

Combustion System Details

The schematic diagram of the installation for thermal utilization of animal meal is shown in Fig. 11. The raw meat-and-bone meal (MBM) to be incinerated is stored in the boiler tank together with the limestone in the proportions corresponding to the stoichiometric ratios needed to neutralize the sulphur and the chlorine contents in a fuel. The mixed feedstock material is first transported by the fuel feeder into the rotary kiln pyrolizer (1). The mixture falls into the reactor chamber via the chute of a feeding unit. In order to provide an even fuel feed into the pyrolizer chamber, the waste is supplied in a stream of flue gases that flow in a gas-box surrounding the feeder. In the central axis of a pyrolizer faceplate is located a supporting burner, either gas or oil, used to provide the thermal conditions required for drying and pyrolysis of a feedstock material. The other end of a rotary chamber is connected to the

Fig. 11 Schematic diagram of the system for thermal processing of meat-and-bone meal

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fluidized bed chamber (2). This connection is additionally sealed through an air canal equipped with a swirl unit and the compensating slides of vertical elongations. To ensure the efficient processing in a rotary chamber, i.e. the drying and devolatilization, the fuel is raised up to over 70% of the chamber diameter by the specially designed lifting flights mounted inside. This, as aforementioned, on the one hand, limits the risk of sintering and agglomeration of a feedstock at the chamber wall and, on the other hand, enhances the heat transfer within the material and promotes the moisture and gas release. It is important to control the temperature inside the rotary chamber which in the case of thermal utilization of animal meal should be kept between 900 and 1200 °C. The products of animal meal pyrolysis, namely the gas mixture and the solid residue (char), are supplied to the fluidized bed chamber, which is constructed from the sealed membrane-type walls bearing a heating medium. Pyrolysis gases are directed to the upper part of a chamber and combusted there, and the char is burned in a fluidized bed in a hopper-shaped lower part of chamber. The orifice plate (air distributor) at the chamber bottom is covered with a refractory concrete on the bedside. The plate closes the wind box below that is divided into a number of sections providing the adjustment of pressure and the gas inflow in each bed zone. The residual ash is removed from the fluidized bed by means of a discharging system. It comprises the discharge channel situated next to the vertical rear wall of a fluidized chamber hopper and the remotely operated rotary feeder. Ash is subsequently directed to the bucket feeder enclosed in a water container that serves as a water trap for a fluidized bed chamber. The bottom section of a chamber, namely the fluidized bed funnel space, is formed by a vertical front and the rear walls, and by the side walls inclined at an angle less than 45° towards the chamber centre. The chamber funnel is covered with an insulating refractory concrete to protect metal elements of the walls from erosion. To control the operation of a fluidized bed unit, the funnel part is equipped with a measuring system allowing to monitor the bed parameters and to regulate the amount of inert material and the fluidizing gas composition. The fluidizing agent is an air/flue gas mixture with the volumetric ratios ranging from 10%/90% to 90%/ 10%. The inert material, fed periodically into the chamber, is composed of a mixture of silica sand and fine grinded slag, blended with limestone. The mass fraction of a limestone depends upon the contents of sulphur, chlorine and fixed carbon in a utilized fuel. To prevent the bed temperature from exceeding the level characteristic for ash softening, the oxygen content in fluidizing gas varies between 2 and 20%vol. and the process temperature is kept within the range between 750 and 900 °C. The burner, mounted in a front wall in the upper part of a fluidized bed chamber, is powered by liquid or gas fuel and supports the pyrolysis gas ignition and stabilizes the combustion process. The fuel burning is conducted at temperatures of 1200–1300 °C and must be controlled so as not to exceed the maximum of 1300 °C to inhibit rapid formation of nitrogen oxides. To provide these conditions, the staged air supply system is implemented. The primary air (0.2–0.4 of the

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stoichiometric air) is fed through the sealing swirl vane duct, which connects the rotary pyrolizer and the fluidized bed chamber. The secondary and the third air are both supplied to the combustion chamber at the same amount as the primary air. Such configuration of air distribution provokes an extension of the combustion zone, leading in result to volumetric heat load of a chamber allowing to keep the process temperature below 1300 °C. The separation chamber (3), to which the exhaust gases are directed passing through the bank of tubes (upper festoon), constitutes the rear wall of a combustion chamber. It is closed by a baffle placed in front of a rotary pyrolizer and the chamber walls. The baffle, bended in its bottom section towards the chamber rear wall at a maximum angle of 45° serves as a tightly closing heated membrane-type surface. The rear chamber wall is of similar shape, but bended towards the opposite direction, thereby constituting the closing of the separation chamber. The bandings are covered with refractory cement protecting them against erosion. Exhaust gases, partially purified from particulates and vapours, are redirected when flowing through the upper festoon to the separation chamber. Due to the direction change and velocity reduction of the flow, they are further de-dusted. The treated flue gas then travels through the lower festoon to the afterburner chamber (4). The combustible gaseous compounds still remaining in a flue gas are burnt out with the use of oil or gas burner, ensuring ignition and the process stabilization. The complete burnout is provided by mixing the exhaust gases with an additional (fourth) airstream at the amount ranging from 0.1 to 0.3 of stoichiometric quantity. The upper section of the afterburning chamber contains a bulkhead superheater and the second stage superheater with the vapour temperature controller placed in a crossover duct. The flue gas cleaned from particulate and gaseous combustible components flows downstream to the convection duct (5) to give off the heat when passing through the system. This also includes the first stage superheater, the water heaters and the air heater that are mounted in a convection channel. Flue gas exiting from the boiler passes through the cleaning installation, comprising a bag filter, a water-based sprinkler and a scrubber, and then is guided to the stack. The flow of heating medium (water) in a fluidized bed chamber is forced by a circulation pump. Water is transferred from the heater to the drum, from which it is supplied through the downcomers to the radiant heating manifolds of the fluidized bed chamber and the after-burning chamber. The steam generated in a boiler flows back to the drum and then is directed to the superheaters and the turbine. Ash removed from flue gas in the discharge hopper of a firing zone, in the afterburning chamber hopper and the convection sections, and in the fabric filter, similarly as in the case of a fluidized bed chamber, is conveyed through the channels equipped with rotary feeders. It is finally routed away via bucket feeder to a disposal site.

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441

Operation of a 12 MW Pilot-Scale Installation

The pilot-scale system based on a staged combustion technology was put into operation in the town of Ostrowite, the Lniano municipality in Kujawy and Pomerania Province (Poland). It serves as a source of thermal energy intended to supply steam for the process needs in an animal waste treatment plant. As aforementioned, the MBM utilization is carried out by a continuous process. The facility is equipped with automatic monitoring and control system developed based on the prescribed control algorithms, which allows real-time adjustment of the unit operation settings so as to meet the required output parameters. This thereby ensures high availability and reliability of the prototype installation. The minimum quantity of meal required for operating the system amounts to 20% of a nominal capacity, whereas the maximum corresponds to the nominal capacity of 120%. The fuel supply unit, hermetically sealed to eliminate dusting and the spread of odours, is located in a room with continuous air extraction system. The discharged contaminated air is further used for fuel combustion. The meal is transferred by external conveyors to an interim bunker hopper and fed into a loading hopper of a rotary pyrolizer. The amount of a material is regulated by means of inverter setting the travelling speed of a feeder. The installation is also fitted with a grate for separating bones that exceed the dimension of 50 mm. The rotary kiln pyrolizer, in which the raw material is subjected to drying and devolatilization, is 1200 mm in diameter. The reactor chamber, made from an uncooled pipe with a refractory lining inside, rotates at 0.5–5 rpm and is inclined by 2–3° towards an outlet. It is equipped with specially designed material lifters alternately distributed inside in three sectors along the chamber length. From the front, the chamber is closed by a sealed faceplate with an oil burner installed in. In the faceplate, there is also mounted the meal/sorbent charging device. The burner is equipped with the systems of ignition and flame control. The quantity of liquid fuel is automatically adjusted according to the type of animal meal being utilized, in order to maintain the temperature of 850–1100 °C inside the chamber. It thereby ranges between 1.0 and 8.0%wt of a meal and depends on a moisture content in a raw waste material. During the start-up, namely at the stage needed to establish the thermal balance, the incineration system is operated with light heating oil. The airflow delivered to the rotary kiln pyrolizer is set depending on a supplementary fuel quantity to ensure its complete combustion and, simultaneously, the oxygen content close to zero in the drying and pyrolysis zones. The process is conducted in a reducing atmosphere to avoid meal burning and heat release. The ignition fuelling system is switched from heating oil to 80 °C hot animal fat of once the target temperature in a rotary pyrolysis reactor is achieved. Hence, since the type of used kindling fuel is classified as an alternative fuel from renewable resources, the total thermal energy generated by the system may be regarded as renewable. The rotary chamber is directly connected with a fluidized bed chamber, which is used to combust the pyrolysis products, namely the gas components in its upper section and the remaining solid (char) in its lower part. The devices are connected

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via a swirling element for primary air that is provided to partially combust evolved pyrolysis gas. The boiler chamber is made of tight water-wall tubes that constitute the evaporator unit. Burning of volatiles takes place in a controlled manner under the multistage air supply (i.e. primary, secondary and third air). At the chamber wall in a fluidized bed zone, there is installed a burner for igniting and supporting combustion stabilization. The air-distribution plate at the chamber bottom allowing to provoke fluidization is composed of several sections inclined towards an ash discharge hopper. Char combustion is controlled by regulating the oxygen concentration in a fluidizing gas, which is a mixture of air and recirculating flue gases. Temperature in a flame zone oscillates within 1100 and 1300 °C, and an oxygen content in a flue gas ranges within 7 and 8%. An excess–air ratio is maintained within 1.1 and 1.25, whereas an oxygen content in a fluidizing gas is 6%. The bed temperature varies between 700 and 950 °C and is being set at the level determined by the ash softening characteristics. The residence time of pyrolysis gas in a fluidized bed chamber at the required temperature range of 1200–1300 °C is 4–6 s, whereas the residence time of the solid pyrolysis residue in a fluidized bed is about 10 min. The flue gas undergoes primary cleaning when passing through the separation chamber, where the fly ash is extracted. After partially purified, it is next directed to the shell-type waste heat recovery boiler that generates superheated steam (temperature of 250–300 °C) at the pressure of 4–6 bars, depending on the technological needs. The prototype staged combustion facility, operated at the feed rate up to *3000 kg/h fuel with the maximum moisture content of 90%wt offers the possibility to treat large streams of more challenging alternative fuels. As shown in Table 6, there is a number of examples of thermal processing trials identified to date; however, they mostly involve the utilization of limited amounts of MBM (up to 25%) blended with base fuel in large-scale units. This regards co-combustion of MBM with coal in 0.5 and 1 MWth pulverized fuel boilers [42], in fluidized bed boilers (200 MWth district heating plant) or MBM co-firing with natural gas (power plant 285 MWe) [31]. Thermal conversion technologies dedicated for utilizing 100% animal waste, or high MBM-percentage fuel blends are rather implemented in small- and medium-scale systems. These include, for instance, the pilot-scale fluidized bed combustors of thermal output of *50–60 kW used to incinerate MBM/coal blends [26, 33]. Also, the conversion of MBM into bio-oil in a pilot-scale pyrolysis fluidized bed reactor at the fuel feed rate of 18 kg/h was conducted by Cascarosa et al. [22]. Full technical scale units for thermal utilization, able to treat large amounts of organic energy-valuable materials, including MBM in particular, are still developing. The facility with rotary kiln of capacity 700 kg/h for continuous waste treatment, however, limited to 70% maximum humidity of a feedstock was studied by Bujak [40]. The industrial-scale system for two-stage combustion of animal and post-slaughter waste with the maximum loading capacity of 1100 kg/h was reported by Poskrobko [35]. The incineration of MBM with an addition of other waste materials in a rotary furnace, for a total fuel feed rate of 2000 kg/h, was tested by Coutand et al. [54].

Not provided

12

MBM/other waste (plastic bags or sewage sludge) (95%/5%) MBM/post-slaughter waste (8–10%/92–90%), (animal fat as additional fuel) MBM, bio-waste of up to 90% humidity (at animal waste treatment plant))

Yes (steam generator) Yes (recovery boiler)

Not provided

Yes (recovery boiler)

*1.11 (waste) + *0.15 (natural gas)

3000

Animal waste, (natural gas as additional fuel)

n.a

n.a

n.a

Heat recovery

n.a

Not specified

2000

MBM

Pilot-scale fluidized bed pyrolysis (conversion to bio-oil) Rotary kiln and after-combustion chamber (at meat-processing factory) Industrial scale rotary furnace

*0.05

*0.06

Output, MWth

1080– 1100

700

MBM (5–100%)/coal

Bubbling fluidized bed combustion

Two-stage combustion system (gasification and combustion) Staged combustion system (pyrolysis and combustion)

Max. 16.5 (for 100% MBM) Max. 15.4 (for 100% MBM) 18

MBM (20–100%)/coal

Pilot-scale fluidized bed combustion

Feed rate, kg/h

Type of fuel

Technology

Table 6 Examples of facilities utilizing animal waste

Necessity to periodically replace the inner refractory concrete in a pyrolysis reactor

Not specified

Not provided

Waste parameters: density 200–1000 kg/m3, 70% max. humidity

–

–

Bed agglomeration above 820 ° C

Limitations/operation problems

Kantorek et al. [48]

Poskrobko [35]

Coutand et al. [54]

Bujak [40]

Cascarosa et al. [22]

Lopes et al. [33]

Gulyurtlu et al. [26]

Ref

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In this context, the implemented staged combustion technology [48, 71] proves its potential in supporting effective waste management and thus the renewable energy sector. The implemented staged combustion technology has also another advantage. The common technological solutions applied for waste incineration based on grate-type boilers do not provide the complete combustion, leading to slag formation. This slag has a considerable content of combustible char particles, exceeding 5% mass, that consist of carbon in nearly 100%. It is therefore regarded as waste, which has to be further disposed of. In the case of considered prototype installation for thermal conversion of organic waste, including MBM in the first place, the remaining ash exhibited trace levels of combustible parts which remain at 0.5% by weight. Furthermore, it appeared to be a valuable raw material for the production of phosphorous-, potassium- and calcium-magnesium-based fertilizers due to the high contents of mineral nutrients (see Table 2). The content of phosphates in ash, basically in form of P2O5, reaches 25–28% and is as high as 5 times the typical contents in natural minerals.

5.2.1

Thermal Performance of the System

The meal blend used for the combustion trials in the prototype utilization unit was sourced from the lot feed material that was available during the day of testing. The results of proximate and ultimate analysis of examined blend are presented in Table 7. The installation has been tested at several part load, corresponding to various meal feed rates between 500 and 2650 kg per hour (Table 8). During the facility tests carried out the temperature in a rotary kiln pyrolizer was set at 850 °C. Under the thermal equilibrium, the processes of feedstock drying, and decomposition were autothermic, which eliminated the necessity to apply auxiliary fuel. The measurements involved the control of: • • • • • • • • •

MBM feed rate, temperature distribution in a pyrolizer (5 points along the rotary axis), inlet/outlet negative pressure in a pyrolysis reactor chamber, outlet pyrolysis gas composition, temperature in the upper zone of fluidized bed chamber, outlet flue gas parameters (temperature and composition), steam parameters (output, temperature and pressure), supply water parameters (temperature and pressure), combustible content in ash.

During the operation tests, the system was supplied with chemically treated boiler water at temperature of 18–20 °C and a pressure of 6 bars.

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Table 7 Chemical composition and physical properties of MBM blend [48]

Proximate analysis (% as received) Moisture Ash Volatile matter Fixed carbon Ultimate analysis (% as received) Carbon Hydrogen Nitrogen Sulphur Oxygen HHV, MJ/kg Bulk density, kg/m3

445

2.53 21.26 67.82 8.39 36.3 5.07 7.3 0.33 12.47 16.13 608

Table 8 Results of measurements and balance calculations for the facility [48] MBM feed rate, kg/h 500 1000

1500

2000

2650

Thermal load (%) 18 38 56 75 100 2240.3 4480.6 6720.8 8961.1 11,873.5 Thermal inputa, kW Steam parameters Output, kg/h 2310 4815 7025 9390 12,720 Pressure, bar 4.95 5.05 5 5.1 5.2 Temperature, °C 254 250 248 252 252 Enthalpy, kJ/kg 2962 2960 2959 2960 2960 Heat capacity, kW 1901 3959 5774 7721 1046 84.9 88.4 85.9 86.2 88.1 Efficiencyb, % 1.19 1.1 1.15 1.12 1.13 Excess–air numberc Outlet flue gas temperature, °C 148 136 158 143 142 a Evaluated based on the determined HHV (see Table 7) b Determined using direct method c Based on CO2 content in flue gas and its max. value for biogas combustion (CO2, max = 1.7%)

The balance calculations were made based on an arithmetic means of the measurements. These average operation parameters for various thermal loads are listed in Table 8. The test results clearly demonstrate that the possibility of fine adjustment of supplied air to the demand allows to optimize the incineration process so as to minimize the losses of incomplete combustion. Maintaining relatively constant temperature of exiting flue gas (around 145 °C on average) and the excess–air number (at k * 1.1) enables to keep the system efficiency at the established level, close to the optimum one.

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Combustibles in Ash

The developed staged incineration system has proved to provide the complete combustion of animal meal, resulting in the elimination of combustible components from slag and the fly ash, and the flammable gases from fumes. The contents of particulate matter in the bottom and fly ashes are shown in Fig. 12. It appears that the issue of carbon leakage may be considered as negligible since the fraction of combustible solids in a bottom ash discharged from the fluidized bed did not exceed the level of 0.025% within the examined range of thermal load. On the other hand, the measurements demonstrated significant percentages of unburnt carbon in fly ash from MBM combustion, ranging between 1.0 and 1.5% (Fig. 12). This is to a large extent related to the physical structure of ash particulates. They display highly developed structure (large porosity), similar to that of a soot, which results in their low apparent density ranging between 0.2 and 0.3 g/m3 [49]. These parameters, in consequence, greatly contribute to driving considerable amounts of char particles out of the fluidized bed chamber.

5.2.3

Emission Levels

There has been a number of research carried out focusing on gas emissions from combustion of pure MBM and its co-combustion with other solid fossil fuels (i.e. peat, coal) in fluidized bed combustors. These trials have shown the positive impact of some MBM shares in a blend on the SO2 emission [26, 31, 43]. Gulyurtlu et al.

Fig. 12 Percentages of combustibles in fly and bottom ashes depending on the facility’s thermal load [48]

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[26] obtained a decrease from 502 mg/Nm3 for 20% MBM shares down to 14 mg/ Nm3 for 100% MBM for co-firing with coal (at 11% O2). McDonnell et al. [43] reported an opposite trend for combustion of MBM/peat pellets, namely an increase from 91 mg/Nm3 up to 383 mg/Nm3 (at 5.9–6.5% O2), respectively, though the SO2 emission for 20% fraction of MBM was less than for 15% MBM share (101 mg/Nm3). Fryda et al. [31] obtained the level of *770 mg/Nm3 on average for 20% MBM share in an MBM/coal blend. As regards the CO emissions, the study of Gulyurtlu et al. [26] revealed its decrease with an increasing share of MBM, showing the level of 8 mg/Nm3 (at 11% O2) for 100% MBM, whereas outcomes of Fryda et al. [31] and McDonnell et al. [43] indicate, in general, an increase of CO levels with an increased MBM percentages. McDonnell et al. [43] obtained a ninefold increase of CO concentration (from *27 to *236 mg/Nm3) with an MBM share increase from 20 to 100%. Similarly, various trends are observed for the NOx emissions. Gulyurtlu et al. [26] and Fryda et al. [31] recorded increased NOx concentrations in flue gas for increased percentages of MBM; however, at the same time the results of Gulyurtlu et al. [26] showed lower NOx emissions for 20% MBM share as compared to 100% coal combustion. On the other hand, McDonnell et al. [43] reported a decrease in NOx emissions with an increased MBM share (from 20 to 100%), arriving at *30 mg/Nm3 for 100% MBM. The measurement results for the pilot-scale staged combustion facility in “Ostrowite” have confirmed that control capabilities of the installation have led to maintain the stable operating parameters at any tested thermal load, ensuring acceptable emission levels of pollutants, mostly below the permissible standards [48]. The resulting emissions of CO, CO2, SO2 and NOx expressed at 6% O2 content in flue gas are shown in Fig. 13 and compared with other available data (Table 9). It has been recognized that stabilized oxygen content allowed to provide the burning conditions favourable to minimize the incomplete combustion loss. This was evidenced by low emission of CO that remained at an average level of *24 mg/Nm3. The test results also revealed that, despite the high content of nitrogen in MBM, an increase in a facility load did not significantly affect NOx concentration in flue gases, which remained at an acceptable level of 300 mg/Nm3 on average. This was due to small fluctuations in an excess-air number, and to the nearly constant process temperature regardless of the variations in a thermal load (see Table 8). Regarding the data given in Table 9, such level of NOx emission is significantly higher than the one measured by McDonnell et al. [43], but less compared to that reported by Gulyurtlu et al. [26]. The SO2 emission obtained during MBM combustion however appeared to be quite high, ranging between 116 and 233 mg/Nm3, which suggests that further steps have been taken to meet the current limits (Council directive 2010/75/EC) [72]. According to Poskrobko [35], who studied the combustion of MBM/ post-slaughter waste, lower SO2 concentrations are facilitated by a strongly oxidizing atmosphere (i.e. 12–17% O2). This aspect with regard to the considered operating system needs further investigations, possibly supported by three-dimensional CFD simulations that would allow to predict temperature

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Fig. 13 Flue gas composition (at 6% O2) depending on the facility’s thermal load [48]

Table 9 Examples of gas emissions from combustion and co-combustion of MBM Gulyurtlu et al. [26]

McDonnell et al. [43]

Fryda et al. [31]

Poskrobko [35]

Kantorek et al. [48]

Fuel type

MBM

MBM

11

6.4

MBM (8– 10%)/ post-slaughter waste 6–8

MBM

O2 in flue gas, % Excess-air CO, mg/Nm3

8

236

SO2, mg/Nm3 NOx, mg/Nm3

14 398

383 30

MBM (10– 20%)/ coal 6 1.3–1.6 *225– 1400 *770 *758– 1300

Not studied

*6 *1.1 *24

*800–1600 Not studied

116–233 270–330

distribution, the evolution and diffusion of individual compounds, as well as the pressure and velocity fields [67, 73]. Nowadays, the use of the numerical approach makes it possible to model the operation of not only the systems with a continuous structure, but also the porous structures in which there are creep flows covering the heat and mass exchange processes, which are extremely useful in determining the efficiency and emissivity of energy systems [74–77].

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6 Conclusions and Future Development Prospects Nowadays, the energy use of waste organics is regarded as desirable for implementing the idea of sustainable development and increasing the proportions of renewables in the energy market. It also commits to the concept of circular economy. Another important issue in the context of using fuels from waste is the construction of power plants with negative carbon dioxide emissions, an example of which was demonstrated by Ziółkowski et al. [78]. Animal meal, like other alternative fuels, has proved to have high potential to support these activities, though it has been considered as challenging fuel. Furthermore, due to constantly growing meat industry and, simultaneously, an increasing amount of waste, the safe and efficient management of animal meal gains in importance. The key issue in thermal utilization of biofuels, particularly those of high ash contents such as animal meal, is the process stabilization that allows to reduce environmentally harmful emissions. As far as animal meal is considered, the conversion process also requires the relevant stringent conditions to ensure destruction of any pathogens. These can be achieved based on the detailed analysis of the raw material itself as well as the in-depth recognition of particular process mechanisms. The chapter gives an overview of carried out extensive studies on the issues related to thermal conversion of meat-and-bone meal (MBM) that resulted in the development of a conceptual design of the staged combustion technology. As it is demonstrated, the performance of operating pilot-scale 12 MW unit based on this technology has proved to provide the MBM incineration with a maximum available thermal efficiency, i.e. between 88.4 and 84.8% depending on the thermal input, as well as the possibly minimum emission levels. Stable oxygen content has led to reduced loss of incomplete combustion, evidenced by low CO emission (*24 mg/ Nm3). It is particularly important that regardless of the system load, the level of temperature in a combustion zone of a fluidized bed chamber remained constant. This, alongside a consistent excess air, resulted in a nearly constant acceptable level of NOx emission (*300 mg/Nm3 on average). The emission of SO2 was at 116– 233 mg/Nm3, and therefore, further improvements should be introduced to meet the current emission limits. Moreover, the technology is promising due to low contents combustibles in bottom and fly ashes that remained below 0.025% and ranged within 1.0–1.5%, respectively, for each facility load. The system is continuously operated and complies with the relevant requirements without significant loss of efficiency; however, the issues related to ash deposition on the boiler walls, the corrosion and the variation in the system efficiency should additionally be considered. In further research perspective, the numerical studies involving the mass and thermal-FSI modelling are foreseen. This will start from modelling single-particle phenomena [27, 79] and will be followed by incorporating the fouling mechanism, the heat transfer deterioration phenomenon and the loss of boiler service life [80]. Similar computations have been hitherto performed for pulverized fuel boilers [81], and fluidized bed boilers [82].

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Index

A Ash (Aanh), 25, 26, 28, 49, 52, 59, 65, 85, 91, 188, 190, 191, 192, 204, 215, 225, 228, 285, 288, 292, 293–295, 303, 306–309, 348, 350, 353, 356, 362, 364, 366, 367, 378, 380, 381, 387, 354, 416, 419, 420, 421, 422, 427, 435, 436, 438, 439, 440, 442, 444, 445, 446, 449, 421, 422, 421 B Bovine Spongiform Encephalopathy (BSE), 417 C Carbon (C), 2, 6, 10, 13, 17, 26, 30–32, 50, 69, 71, 78, 93, 96, 98, 103, 130, 131, 143, 153, 154, 156, 177, 186, 198, 238, 239 Carbon dioxide (CO2), 2, 6, 71, 153, 155, 156, 183, 186, 238, 240, 243, 266, 289, 325, 449 Carbon monoxide (CO), 50, 78, 238, 240, 287, 288, 380, 387 Combined Heat and Power (CHP), 10, 56, 215, 283–285, 287–289, 336–338 Combustible sulphur (SC), 26 E Ethane, C2H4, 78, 158 Ethanol (C2H5OH), 31, 46, 77, 100, 255–260, 275, 294, 315, 316 F Fixed Carbon (Cfanh), 25, 26, 80, 91, 309, 420, 439, 445

H Hydrogen (H2), 26, 31, 75, 78, 92, 93, 98–100, 127, 153, 154, 156, 158, 186, 237, 239, 241–254, 265, 273, 274, 287, 292, 294, 309, 356, 357, 362, 365, 420, 427, 445 L Low Calorific Value (LCV), 27, 29, 36, 52, 54, 75, 77, 83, 84, 86, 92, 96–100 Low Heating Value (LHV), 70, 186, 190, 191, 216, 308, 309, 420 M Meat-and-Bone Meal (MBM), 416–427, 429, 437, 438, 441–449 Methane (CH4), 69, 71, 72, 78, 99, 149–153, 155, 156, 158, 165, 166, 167, 186, 239, 243, 245, 266, 287, 315, 316 Methanol (CH3OH),, 31, 39, 46, 77, 100, 237, 244, 255, 256, 260–265, 275, 276 Moisture, humidity (Wi), 52, 292, 294 N Nitrogen (N), 26, 31, 32, 71, 93, 98, 152–154, 156, 186, 215, 238–240, 243, 244, 249, 265, 266, 268, 269, 273, 276, 287, 292, 294, 306, 309, 353, 356, 357, 362, 365, 380, 417, 420, 439, 445, 447 O Oxygen (O), 26, 31, 32, 55, 71, 81, 98, 105, 108, 110, 154, 185, 238, 239, 252, 255, 258, 259, 266, 269, 274–276, 285, 289, 292, 294, 309, 356, 357, 361–363, 385,

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 G. Lazaroiu and L. Mihaescu (eds.), Innovative Renewable Waste Conversion Technologies, https://doi.org/10.1007/978-3-030-81431-1

455

456

Index 420, 427–430, 437, 439, 441, 442, 445, 447, 449

P Propane, C3H8, 78, 99, 156, 158, 266–270 R Recuperative Steam Generator (HRSG), 69

Renewable Energy Sources (RES), 1, 2, 41, 56, 69, 322, 396–399 V Volatiles (Vanh), 25, 26, 55, 79–81, 89, 92, 188, 420, 426, 427, 429–436, 442