Journal articles on the topic 'Chemical and thermal processes in energy and combustion'
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1
Wolfrum, J. "Laser Induced Chemical Reactions in Combustion and Industrial Processes." Laser Chemistry 6, no. 2 (January 1, 1986): 125–47. http://dx.doi.org/10.1155/lc.6.125.
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The rapid development of powerful UV-laser sources allows the investigation of macroscopic and microscopic details of elementary chemical reactions important in combustion processes. Experimental results on the effect of selective translational and vibrational excitation of reactants in elementary combustion reactions using laser photolysis and time-resolved atomic line resonance absorption, laser-induced fluorescence and CARS spectroscopy are compared with the results of theoretical studies on ab initio potential energy surfaces and thermal rate parameters. Thermal elimination of hydrogen chloride from 1,2-dichloroethane and 1,1,1-chlorodifluoroethane is a main industrial route to some important monomer compounds. Inducing these radical chain reactions by UV-exciplex laser radiation offers the advantage that a monomolecular process with low activation energy becomes the rate determining step. This allows lower process temperatures with decreasing energy expense and avoiding the high temperature formation of byproducts.
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Demin, A. V., R. Ya Dyganova, and N. N. Fakhreev. "Analysis of Processes of Thermal Utilization of Biowaste." Ecology and Industry of Russia 22, no. 5 (May 23, 2018): 50–53. http://dx.doi.org/10.18412/1816-0395-2018-5-50-53.
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The problems associated with the thermal utilization of droppings litter, which is formed at poultry farming facilities, are considered. The results of numerical studies for the biogas combustion method based on preliminary gasification of fuel are presented. A method for estimating the composition of thermal decomposition products based on the thermodynamic calculation of the chemical and phase equilibria is proposed. Calculated indicators of energy efficiency and environmental characteristics of combustion products are presented for a multi-zone combustion scheme.
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Barysheva, Olga, and Alina Mokhova. "Formation of soot in the disposal of municipal solid waste." E3S Web of Conferences 274 (2021): 08001. http://dx.doi.org/10.1051/e3sconf/202127408001.
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In power plants intended for the disposal of solid household waste, the processes take place at a high temperature. For such installations, nonequilibrium processes are characteristic of a change in the composition of combustion products caused by the final rates of the ongoing chemical reactions. This affects the basic characteristics of the combustion process of municipal solid waste. A mathematical model has been created for calculating the chemically nonequilibrium composition of the fuel. Solid household and industrial waste is a high-energy fuel. It is a high energy fuel. The process of thermal neutralization of solid household waste is considered. An alternative calculation method is presented that allows one to find the composition of combustion products under conditions of nonequilibrium in the process of thermal utilization of solid domestic waste. The data on the composition and properties of solid household waste obtained by the developed method of calculation allow predicting the yield of super Eco toxicants in combustion products. On the basis of the equations of formal chemical kinetics, an alternative was created, which consists in determining the composition of combustion products taking into account the kinetics of chemical reactions. The assumption is introduced that transformations in the gas phase are elementary, one-stage. Various chemical interactions can be represented by a set of elementary stages. The most probable are mono-, biand three molecular chemical reactions. The method allows predicting the yield of Eco toxicants by finding the composition of the fuel combustion products prior to its utilization.
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Liang, Yuntao, and Rui Zhou. "Numerical Simulation of Coupled Thermal-Hydrological-Mechanical-Chemical Processes in the Spontaneous Combustion of Underground Coal Seams." Geofluids 2021 (August 12, 2021): 1–12. http://dx.doi.org/10.1155/2021/9572502.
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In this study, we develop a fully coupled thermal-hydrological-mechanical-chemical (THMC) model to analyze the spontaneous combustion process of underground coal seams, focusing on investigating the influences of the pressure difference between oxygen and coal, the rate of coal-oxygen reaction heat, and the activation energy. The simulation results show that as oxygen propagates into the coal seams, the coal-oxygen reaction causes the spontaneous combustion of coal to heat. The consumption of oxygen leads to an increase in oxygen consumption along the way and a decrease in gas pressure. The permeability near the right boundary increases while significantly reducing the area far away from the right boundary as the predominant effect of spontaneous combustion. Additionally, a sensitivity study shows that a more considerable pressure difference and coal-oxygen reaction heat contribute to promoting the coal temperature, while the activation energy has a slight effect. Moreover, an increase in coal-oxygen reaction heat and activation energy accelerates the oxygen consumption rate and thus causes a lower oxygen concentration. Overall, the results provide a basis for the prediction and prevention of coal seam spontaneous combustion.
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Demin, A. V., and G. V. Demina. "Environmental characteristics of thermal utilization of waste with external and internal supply of thermal energy." Power engineering: research, equipment, technology 24, no. 6 (January 11, 2023): 143–52. http://dx.doi.org/10.30724/1998-9903-2022-24-6-143-152.
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THE PURPOSE. Identification of optimal regimes for autothermal and allothermic methods of gasification of plant biomass in terms of energy parameters of generator gases, as well as determination of environmental indicators during subsequent combustion of generator gases to obtain thermal energy.METHODS. When modeling gasification processes, a nonstoichiometric model was used, based on the assumption that a chemically reacting multicomponent mixture is in a state of thermodynamic and chemical equilibrium, which corresponds to the minimum value of the isobaric-isothermal potential. When modeling the combustion of generator gas in a mixture with air, a kinetic model of a perfectly mixed flow reactor was used and the detailed mechanism of chemical interaction for the C-H-O-N-S reacting system was taken into account. The calorific value of generator gas obtained by steam gasification and external supply of thermal energy is significantly higher than the calorific value of gas obtained by internal supply of thermal energy. However, the values of the energy potential and thermochemical efficiency are very close for both types of gasification.RESULTS. For plant biomass with a given averaged elemental composition, gasification conditions are determined that increase the degree of conversion of initial materials into generator gas. In particular, for the autothermal gasification method, the maximum calculated values of the energy potential of dry ash-free generator gas and thermochemical efficiency were obtained at an excess air coefficient α ≈ 0.32. For the allothermic gasification method, the maximum calculated values of the energy potential of the generator gas and the thermochemical efficiency correspond to the gasification temperature range T ≈ 1050 -1100 K and the mass fraction of the supplied steam gH2O ≈ 0.217. To ensure these conditions, it will be necessary to supply thermal energy through combustion of ≈ 37 wt. % generator gas. Generator gas produced by the allothermic method has higher energy performance, and the negative impact on the environment during its subsequent combustion is characterized by lower specific CO and CO2 emissions in terms of a ton of reference fuel.
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Barmina, Inesa, Harijs Kalis, Antons Kolmickovs, Maksims Marinaki, Liiva Ozola, Uldis Strautins, Raimonds Valdmanis, and Maija Zake. "MATHEMATICAL MODELLING AND EXPERIMENTAL STUDY OF STRAW CO-FIRING WITH GAS." Mathematical Modelling and Analysis 24, no. 4 (October 25, 2019): 507–29. http://dx.doi.org/10.3846/mma.2019.031.
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The main goal of the present study is to promote a more effective use of agriculture residues (straw) as an alternative renewable fuel for cleaner energy production with reduced greenhouse gas emissions. With the aim to improve the main combustion characteristics at thermo-chemical conversion of wheat straw, complex experimental study and mathematical modelling of the processes developing when co-firing wheat straw pellets with a gaseous fuel were carried out. The effect of co-firing on the main gasification and combustion characteristics was studied experimentally by varying the propane supply and additional heat input into the pilot device, along with the estimation of the effect of co-firing on the thermal decomposition of wheat straw pellets, on the formation, ignition and combustion of volatiles (CO, H2). A mathematical model has been developed using the environment of the Matlab (2D modelling) and MATLAB package ”pdepe”(1D modelling) considering the variations in supplying heat energy and combustible volatiles (CO, H2) into the bottom of the combustor. Dominant exothermal chemical reactions were used to evaluate the effect of co-firing on the main combustion characteristics and composition of the products CO2 and H2O. The results prove that the additional heat from the propane flame makes it possible to control the thermal decomposition of straw pellets, the formation, ignition and combustion of volatiles and the development of combustion dynamics, thus completing the combustion of biomass and leading to cleaner heat energy production.
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Ion, Ion V., Florin Popescu, Razvan Mahu, and Eugen Rusu. "A Numerical Model of Biomass Combustion Physical and Chemical Processes." Energies 14, no. 7 (April 2, 2021): 1978. http://dx.doi.org/10.3390/en14071978.
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Identifying a modeling procedure of biomass thermal decomposition that is not only simple enough to implement and use, and computationally efficient, but also sufficiently accurate for engineering design activities, and with a spectrum of applications as broad as possible is a very difficult task. The authors propose a procedure which consists of two main stages: (a) the static modeling phase with the purpose of generating the algorithm (macro functions) that supplies a Computational Fluid Dynamics (CFD) model with specific input data (source/sink terms and local material properties) and (b) the dynamic modeling phase, where the CFD model is bi-directionally coupled to the external biomass decomposition model in the form of a User-Defined Function (UDF). The modeling approach was successfully validated against data obtained from single particle decomposition experiments, demonstrating its applicability even to large biomass particles, under high heating rates and combusting conditions.
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Yang, Qingfeng, Karla Dussan, Rory F. D. Monaghan, and Xinmin Zhan. "Energy recovery from thermal treatment of dewatered sludge in wastewater treatment plants." Water Science and Technology 74, no. 3 (May 31, 2016): 672–80. http://dx.doi.org/10.2166/wst.2016.251.
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Sewage sludge is a by-product generated from municipal wastewater treatment (WWT) processes. This study examines the conversion of sludge via energy recovery from gasification/combustion for thermal treatment of dewatered sludge. The present analysis is based on a chemical equilibrium model of thermal conversion of previously dewatered sludge with moisture content of 60–80%. Prior to combustion/gasification, sludge is dried to a moisture content of 25–55% by two processes: (1) heat recovered from syngas/flue gas cooling and (2) heat recovered from syngas combustion. The electricity recovered from the combined heat and power process can be reused in syngas cleaning and in the WWT plant. Gas temperature, total heat and electricity recoverable are evaluated using the model. Results show that generation of electricity from dewatered sludge with low moisture content (≤ 70%) is feasible within a self-sufficient sludge treatment process. Optimal conditions for gasification correspond to an equivalence ratio of 2.3 and dried sludge moisture content of 25%. Net electricity generated from syngas combustion can account for 0.071 kWh/m3 of wastewater treated, which is up to 25.4–28.4% of the WWT plant's total energy consumption.
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Kijo-Kleczkowska, Agnieszka, and Adam Gnatowski. "Recycling of Plastic Waste, with Particular Emphasis on Thermal Methods—Review." Energies 15, no. 6 (March 14, 2022): 2114. http://dx.doi.org/10.3390/en15062114.
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The civilization development requires improvement of technologies and satisfaction of people’s needs on the one side, but on the other one it is directly connected with the increasing production of waste. In this paper, the authors dealt with the second of these aspects, reviewing the recycling of plastic waste, which can be processed without changing its chemical structure (mechanical recycling), and with changing its chemical structure (chemical recycling, of which thermal recycling). Mechanical recycling involves shredding the waste in order to obtain recyclate or regranulate that meets specific quality requirements. Chemical recycling consists of the degradation of the material into low-molecular compounds, and it can take place in the processes of hydrolysis, glycolysis, methanolysis by means of chemical solvents, and during thermal processes of hydrocracking, gasification, pyrolysis, combustion, enabling the recovery of gaseous and liquid hydrocarbons foundings in application as a fuel in the energy and cement-lime industry and enabling the recovery of thermal energy contained in plastics. The paper focuses on thermal methods of plastics recycling that become more important due to legal regulations limiting the landfilling of waste. The authors also took up the properties of plastics and their production in European conditions.
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Askarova, Aliya, Saltanat Bolegenova, Symbat Bolegenova, Meruyert Beketayeva, Valeriy Maximov, Aizhan Nugymanova, and Pavel Šafařík. "SIMULATION OF LOW-GRADE COAL COMBUSTION IN REAL CHAMBERS OF ENERGY OBJECTS." Acta Polytechnica 59, no. 2 (April 30, 2019): 98–108. http://dx.doi.org/10.14311/ap.2019.59.0098.
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The aim of the work is to create new computer technologies for 3D modelling of heat and mass transfer processes in high-temperature physicochemically reacting environments that will allow to determine the aerodynamics of the flow and heat and mass transfer characteristics of technological processes occurring in the combustion chambers in existing coal-fired thermal power plants of the Republic of Kazakhstan. The novelty of the research lies in the use of the latest information technologies of 3D modelling, which will enable project participants to obtain new data on complex heat and mass transfer processes when burning pulverized coal in real combustion chambers operating in Kazakhstan’s Thermal Power Plants (TPP). A numerical simulation, including thermodynamic, kinetic and threedimensional computer simulation of heat and mass transfer processes when burning low-grade fuel, will allow finding optimal conditions for setting adequate physical, mathematical and chemical models of the technological process of combustion of burning high ash coals. The computer modelling methods proposed for the development are new and technically feasible, since coal-fired power plants all over the world use all types of coal. The developed technologies will allow replacing or eliminating the conduct of expensive and labour-consuming natural experiments on coal-fired power plants.
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Atgur, Vinay, G. Manavendra, Nagaraj R. Banapurmath, Boggarapu Nageswar Rao, Ali A. Rajhi, T. M. Yunus Khan, Chandramouli Vadlamudi, Sanjay Krishnappa, Ashok M. Sajjan, and R. Venkatesh. "Essence of Thermal Analysis to Assess Biodiesel Combustion Performance." Energies 15, no. 18 (September 10, 2022): 6622. http://dx.doi.org/10.3390/en15186622.
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The combustion phenomena are always complex in nature due to the involvement of complex series and parallel reactions. There are various methods that are involved in analyzing combustion phenomena. Viscosity is the first and foremost factor that acts as the DNA of fuel. By evaluating the viscosity, it is possible initially to understand the combustion phenomena. Thermophysical and transport properties are helpful during the intensification of the combustion process. Combustion experiments are economically infeasible and time-consuming processes. Combustion simulations demand excellent computational facilities with detailed knowledge of chemical kinetics. So far, the majority of researchers have focused on analyzing coal combustion phenomena, whereas less work has been carried out on liquid fuels, especially biodiesel combustion analysis. Traditional engine testing provides only performance parameters, and it fails to have oversight of the thermodynamic aspects. The application of thermal analysis methods in combustion research is useful in the design, modeling, and operation of the systems. Such investigations are carried out extensively in the combustor, engine, and process industries. The use of differential scanning calorimetry (DSC) and thermogravimetry (TG) to assess the properties of biofuels has been attracting researchers in recent years. The main objective of this paper is to discuss the application of TGA and DSC to analyze heat flow, enthalpy, thermal stability, and combustion indexes. Moreover, this paper reviews some of the other aspects of the kinetics of combustion, transport properties’ evaluation, and combustion simulations for biodiesels and their blends. TG curves indicate two phases of decomposition for diesel and three phases for biofuel. The B-20 blend’s (20% biodiesel and 80% diesel) performance was found to be similar to that of diesel with the combustion index and intensity of combustion nearly comparable with diesel. It is thermally more stable with a high offset temperature, confirming a longer combustion duration. A case study reported in this work showed diesel and B20 JOME degradation start from 40 °C, whereas jatropha oil methyl ester (JOME) degradation starts from 140 °C. JOME presents more decomposition steps with high decomposition temperatures, indicative of more stable compound formation due to the oxidation process. The peak temperature of combustion for diesel, JOME, and B20 JOME are 250.4 °C, 292.1 °C, and 266.5 °C, respectively. The ignition index for the B-20 blend is 73.73% more than that of diesel. The combustion index for the B20 blend is 37.81% higher than diesel. The B20 blend exhibits high enthalpy, better thermal stability, and a reduced peak temperature of combustion with an improved combustion index and intensity of combustion nearly comparable to diesel.
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Hutchins, T. E., and M. Metghalchi. "Energy and Exergy Analyses of the Pulse Detonation Engine." Journal of Engineering for Gas Turbines and Power 125, no. 4 (October 1, 2003): 1075–80. http://dx.doi.org/10.1115/1.1610015.
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Energy and exergy analyses have been performed on a pulse detonation engine. A pulse detonation engine is a promising new engine, which uses a detonation wave instead of a deflagration wave for the combustion process. The high-speed supersonic combustion wave reduces overall combustion duration resulting in an nearly constant volume energy release process compared to the constant pressure process of gas turbine engines. Gas mixture in a pulse detonation engine has been modeled to execute the Humphrey cycle. The cycle includes four processes: isentropic compression, constant volume combustion, isentropic expansion, and isobaric compression. Working fluid is a fuel-air mixture for unburned gases and products of combustion for burned gases. Different fuels such as methane and JP10 have been used. It is assumed that burned gases are in chemical equilibrium states. Both thermal efficiency and effectiveness (exergetic efficiency) have been calculated for the pulse detonation engine and simple gas turbine engine. Comparison shows that for the same pressure ratio pulse detonation engine has better efficiency and effectiveness than the gas turbine system.
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Wang, Fei, Xueming Li, Shuai Feng, and Yunfei Yan. "Numerical Study on the Characteristics of Methane Hedging Combustion in a Heat Cycle Porous Media Burner." Processes 9, no. 10 (September 28, 2021): 1733. http://dx.doi.org/10.3390/pr9101733.
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With the rapid development of portable devices and micro-small sensors, the demand for small-scale power supplies and high-energy-density energy supply systems is increasing. Comparing with the current popular lithium batteries, micro-scale burners based on micro-thermal photoelectric systems have features of high power density and high energy density, the micro-scale burner is the most critical part of the micro-thermal photovoltaic system. In this paper, the combustor was designed as a heat cycle structure and filled with porous media to improve the combustion characteristics of the micro combustor. In addition, the influence of the porous media distribution on the burner center temperature and wall temperature distribution were studied through numerical simulation. Furthermore, the temperature distribution of the combustor was studied by changing the porous media parameters and the wall parameters. The research results show that the heat cycle structure can reduce heat loss and improve combustion efficiency. When the combustion chamber is filled with porous media, it makes the radial center temperature rise by about 50 K and the temperature distribution more uniform. When filling the heat cycle channel with porous media the wall temperature can be increased. Finally, the study also found that as methane is combusted in the combustor, the temperature of the outer wall gradually increases as the intake air velocity increases. The results of this study provide a theoretical and practical basis for the further design of high-efficiency combustion micro-scale burners in the future.
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Yarmolchick, Yu Р., R. Schröger, H. Haberfelner, M. Pichler, D. Kostić, and G. V. Moroz. "Combined Combustion of Various Industrial Waste Flows in Boiler Furnaces. Part 2." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no. 6 (December 2, 2020): 526–40. http://dx.doi.org/10.21122/1029-7448-2020-63-6-526--540.
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When industrial waste flows (mixtures of different substances) are burned, thermal energy is generated in the combustion chambers of the heat generating plants. In this case, the energy contribution of the chemical compounds included in their composition is different. The article considers the enthalpies of combustion of the most characteristic chemicals, formulates the energy balance equations while simultaneously burning several mass flows of fuels, taking into account their calorific value. The general mechanisms of heat transfer to the walls of the combustion chamber are investigated. An analysis is made of the contribution of convection and the radiation mechanism to the total amount of heat transferred to the heat generator, depending on the process temperature. It is demonstrated that the heat transfer by radiation between the combustion chamber and the boiler tubes depends on the thermal radiation properties of ash deposition. In this case, the emissivity of the resulting ash deposition decreases with increasing temperature. The dependence of the maximum flame radiation on the C/H ratio by weight is considered using the example of the initial combustible chemicals that are part of solid, liquid and gaseous wastes of industrial technologies. The main pollutants which emerge during the combustion of industrial waste are determined. The mechanisms of formation of nitrogen oxides (NOx), particulate matter, sulfur oxides (SOx), halogen acids, polymers, soot, volatile organic compounds and ash are considered in detail. The distribution of various processes of formation of nitrogen oxides depending on the value inverse to the coefficient of excess air (φ = 1/α) is determined. A physical scheme and a system of chemical equations of the mechanism of soot formation which includes the most important stages of the formation of polycyclic aromatic hydrocarbons are presented. The stages of the separation of reactive ash-forming elements are considered. It is demonstrated that ash deposits pose serious problems in the operation of heat generators, especially those that have such a developed heat exchange surface, such as boiler plants. In this regard, the forms and conditions of the processes of ash deposition are also considered separately. The combustion conditions affecting the state, size and distribution of solid particles and the condensed phase of ash are determined.
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Bhaskaran Anangapal, Hari. "Energy and exergy analysis of fuels." International Journal of Energy Sector Management 8, no. 3 (August 26, 2014): 330–40. http://dx.doi.org/10.1108/ijesm-04-2013-0012.
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Purpose – The purpose of this study is to carry out energy and exergy analysis of fuels. Production of power and heat in industrialized countries is almost entirely based on combustion of fuels. Usually, combustion takes place in boilers or furnace; well-designed boilers have high thermal efficiencies of > 90 per cent. Even very high efficiencies, close to 100 per cent can be achieved depending on the applied fuel and boiler type. These high thermal efficiencies do suggest that combustion processes are highly optimized and do not need further improvements with regard to their thermodynamic performance. Second law (entropy or exergy) evaluations, however, shows that thermodynamic losses of boiler and furnaces are much larger than the thermal efficiencies do suggest. During combustion, air is predominantly used. When using air, the adiabatic combustion temperature depends only on the properties of fuel and air. The determining parameters for optimal fuel utilization are the fuel type, their composition and moisture content, the air temperature and air factor at combustion inlet. Design/methodology/approach – Following assumptions are made for the analysis: calculation on the basis of 100 kg of dry and ash free fuel entering the control volume; fuel entering the control volume at T0, P0 and reacting completely with air entering separately at T0, P0 to form CO2, SO2, N2 and H2O, which exit separately at T0, P0 (T0 = 298 K; P0 = 1 atm); all heat transfer occurs at temperature T0; and the chemical exergy of the ash has been ignored The availability change and the irreversibility for chemical reactions of hydrocarbon fuels were studied because fuel and dry air composed of O2 and N2 react to form products of combustion in the restricted dead state, and fuel and dry air composed of O2 and N2 react to form products of combustion which end up in the environmental (unrestricted) dead state. The difference between the above two statement, is the chemical availability of the product gases as they proceed from the restricted to the unrestricted dead state. These evaluations were made in terms of enthalpy and entropy values of the reacting species. T0 extend these concepts to the most general situation, it is considered a steady-state control volume where the fuels enters at the restricted dead state, the air (oxidant) is drawn from the environment, and the products are returned to the unrestricted dead state. Findings – It is evident from the analysis that an air factor of 1.10-1.20 is sufficient for liquid fuels, whereas solid fuels will require air factors of 1.15–1.3. When the temperatures of the products of combustion (Tp) are cooled down to that of T0, the maximum reversible work occurs. From the analysis, it is clear that the rather low combustion temperature and the need for cooling down the flue gases to extract the required heat are the main causes of the large exergy losses. The maximum second law efficiency also occurs when Tp is set equal to T0. The maximum second law efficiency per kilo mole of fuel is found to be 73 per cent, i.e. 73 per cent of the energy released by the cooling process could theoretically be converted into useful work. It is evident that reducing exergy losses of combustion is only useful if the heat transferred from the flue gas is used at high temperatures. Otherwise, a reduction of exergy loss of combustion will only increase the exergy loss of heat transfer to the power cycle or heat-absorbing process. The exergy loss of combustion can be reduced considerable by preheating combustion air. Higher preheat temperatures can be obtained by using the flue gas flow only for preheating air. The remainder of the flue gas flow can be used for heat transfer to a power cycle or heat-absorbing process. Even with very high air preheat temperatures, exergy losses of combustion are still > 20 per cent. The application of electrochemical conversion of fuel, as is realized in fuel cells, allows for much lower exergy loses for the reaction between fuel and air than thermal conversion. For industrial applications, electrochemical conversion is not yet available, but will be an interesting option for the future. Originality/value – The outcome of the study would certainly be an eye-opener for all the stakeholders in thermal power plants for considering the second law efficiency and to mitigate the irreversibilities.
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Tarver, Craig M., and Steven K. Chidester. "On the Violence of High Explosive Reactions." Journal of Pressure Vessel Technology 127, no. 1 (February 1, 2005): 39–48. http://dx.doi.org/10.1115/1.1845474.
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High explosive reactions can be caused by three general energy deposition processes: impact ignition by frictional and/or shear heating; bulk thermal heating; and shock compression. The violence of the subsequent reaction varies from benign slow combustion to catastrophic detonation of the entire charge. The degree of violence depends on many variables, including the rate of energy delivery, the physical and chemical properties of the explosive, and the strength of the confinement surrounding the explosive charge. The current state of experimental and computer-modeling research on the violence of impact, thermal, and shock-induced reactions is briefly reviewed in this paper.
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Oost, Guido Van. "Applications of Thermal Plasmas for the Environment." Applied Sciences 12, no. 14 (July 17, 2022): 7185. http://dx.doi.org/10.3390/app12147185.
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Thermal processing such as incineration is most commonly used for the treatment of waste streams, whereby often-incomplete combustion of organic waste can lead to dangerous products in the exhaust gases. Thermal plasma technology with its wide temperature range is suitable to treat almost any chemical composition of wastes. It enables the efficient and environmentally friendly conversion of organic waste into energy or chemicals, as well as the pyrolysis of hazardous organic compounds The limitations of conventional technologies and stricter environmental legislation on the processing of wastes make plasma technologies increasingly attractive. Priority is given to environmental quality at affordable costs and to the use of innovative thermochemical conversion technologies (gasification and pyrolysis) to contribute to sustainable development and circular economy in which waste is managed as a resource.
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Barmina, Inesa, Antons Kolmickovs, Raimonds Valdmanis, Maija Zake, Sergejs Vostrikovs, Harijs Kalis, and Uldis Strautins. "Electric Field Effect on the Thermal Decomposition and Co-combustion of Straw with Solid Fuel Pellets." Energies 12, no. 8 (April 22, 2019): 1522. http://dx.doi.org/10.3390/en12081522.
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The aim of this study was to provide more effective use of straw for energy production by co-firing wheat straw pellets with solid fuels (wood, peat pellets) under additional electric control of the combustion characteristics at thermo-chemical conversion of fuel mixtures. Effects of the DC electric field on the main combustion characteristics were studied experimentally using a fixed-bed experimental setup with a heat output up to 4 kW. An axisymmetric electric field was applied to the flame base between the positively charged electrode and the grounded wall of the combustion chamber. The experimental study includes local measurements of the composition of the gasification gas, flame temperature, heat output, combustion efficiency and of the composition of the flue gas considering the variation of the bias voltage of the electrode. A mathematical model of the field-induced thermo-chemical conversion of combustible volatiles has been built using MATLAB. The results confirm that the electric field-induced processes of heat and mass transfer allow to control and improve the main combustion characteristics thus enhancing the fuel burnout and increasing the heat output from the device up to 14% and the produced heat per mass of burned solid fuel up to 7%.
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Balogun, Ayokunle O., Adekunle A. Adeleke, Peter P. Ikubanni, Samuel O. Adegoke, Abdulbaset M. Alayat, and Armando G. McDonald. "Study on Combustion Characteristics and Thermodynamic Parameters of Thermal Degradation of Guinea Grass (Megathyrsus maximus) in N2-Pyrolytic and Oxidative Atmospheres." Sustainability 14, no. 1 (December 23, 2021): 112. http://dx.doi.org/10.3390/su14010112.
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This study provides an extensive investigation on the kinetics, combustion characteristics, and thermodynamic parameters of the thermal degradation of guinea grass (Megathyrsus maximus) in N2-pyrolytic and oxidative atmospheres. A model-fitting technique and three different iso-conversional techniques were used to investigate the kinetics of the thermal process, after which an analysis of the combustion characteristics and thermodynamic parameters was undertaken. Prior to this, experiments on the physico-chemical characterization, thermogravimetric, and spectroscopic analyses were carried out to provide insight into the compositional structure of the guinea grass. The volatile matter, fixed carbon, and total lignin contents by mass were 73.0%, 16.1%, and 21.5%, respectively, while the higher heating value was 15.46 MJ/kg. The cellulose crystallinity index, determined by XRD, was 0.43. The conversion of the GG in air proceeded at a relatively much higher rate as the maximum mass-loss rate peak in a 20 K/min read was −23.1 and −12.3%/min for the oxidative and the pyrolytic, respectively. The kinetics investigation revealed three distinctive stages of decomposition with their corresponding values of activation energy. The average values of activation energy (FWO) at the latter stages of decomposition in the pyrolytic processes (165 kJ/mol) were higher than those in the oxidative processes (125 kJ/mol)—an indication of the distinctive phenomenon at this stage of the reaction. The Coats–Redfern kinetic model revealed that chemical reactions and diffusional models played a predominant role in the thermal decomposition process of the GG. This study showed that the thermodynamic parameters varied with the conversion ratio, and the combustion performance increased with the heating rates. The use of GG as an energy feedstock is recommended based on the findings from this work.
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Brandauer, M., A. Schulz, and S. Wittig. "Mechanisms of Coke Formation in Gas Turbine Combustion Chambers." Journal of Engineering for Gas Turbines and Power 118, no. 2 (April 1, 1996): 265–70. http://dx.doi.org/10.1115/1.2816587.
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New gas turbine combustor designs are developed to reduce pollutant and NOx emissions. In these new combustors, the formation of carbonaceous deposits, especially in prevaporizers, affects the reliability and effectiveness of operation. To avoid deposits, a detailed knowledge of the origins and mechanisms of formation is required. To obtain a deeper insight, the phenomena were studied systematically. The deposits under consideration show differing characteristics suggesting more than one formation mechanism in the combustor. Consequently, the primary goal was to identify the formation mechanisms and, subsequently, to simulate the mechanisms under well-defined conditions in bench tests for determining the relevant parameters of deposit build-up. The mechanisms of formation were identified based on the properties of the deposits in the combustion chamber. In order to characterize the deposits, physical and chemical analysis techniques were utilized. In summary, tests and numerical predictions identified two major paths of formation: a deposit build-up resulting from flame products such as soot or coked droplets and a deposit build-up resulting from liquid fuel impinging the wall accompanied with chemical reactions at the wall. The deposits caused by fuel droplet impingement were intensively studied in bench tests. In analyzing the processes, the influence of wall temperature, fuel composition, and the oxygen content in the environment is shown in detail. In addition, the importance of thermal instabilities of the fuel, previously studied under fuel supply system conditions, is demonstrated for a deposit formation inside a combustion chamber.
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Peters, Bernhard, and Joanna Smuła-Ostaszewska. "A Numerical Approach to Predict Sulphur Dioxide Emissions During Switchgrass Combustion." Chemical and Process Engineering 34, no. 1 (March 1, 2013): 121–37. http://dx.doi.org/10.2478/cpe-2013-0011.
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Abstract The demand for a net reduction of carbon dioxide and restrictions on energy efficiency make thermal conversion of biomass a very attractive alternative for energy production. However, sulphur dioxide emissions are of major environmental concern and may lead to an increased corrosion rate of boilers in the absence of sulfatation reactions. Therefore, the objective of the present study is to evaluate the kinetics of formation of sulphur dioxide during switchgrass combustion. Experimental data that records the combustion process and the emission formation versus time, carried out by the National Renewable Energy Institute in Colorado (US), was used to evaluate the kinetic data. The combustion of switchgrass is described sufficiently accurate by the Discrete Particle Method (DPM). It predicts all major processes such as heating-up, pyrolysis, combustion of switchgrass by solving the differential conservation equations for mass and energy. The formation reactions of sulphur dioxide are approximated by an Arrhenius-like expression including a pre-exponential factor and an activation energy. Thus, the results predicted by the Discrete Particle Method were compared to measurements and the kinetic parameters were subsequently corrected by the least square method until the deviation between measurements and predictions was minimised. The determined kinetic data yielded good agreement between experimental data and predictions.
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Su, Yinjiao, Xuan Liu, Yang Teng, and Kai Zhang. "Mercury Speciation in Various Coals Based on Sequential Chemical Extraction and Thermal Analysis Methods." Energies 14, no. 9 (April 21, 2021): 2361. http://dx.doi.org/10.3390/en14092361.
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Coal combustion is an anthropogenic source of mercury (Hg) emissions to the atmosphere. The strong toxicity and bioaccumulation potential have prompted attention to the control of mercury emissions. Pyrolysis has been regarded as an efficient Hg removal technology before coal combustion and other utilization processes. In this work, the Hg speciation in coal and its thermal stability were investigated by combined sequential chemical extraction and temperature programmed decomposition methods; the effect of coal rank on Hg speciation distribution and Hg release characteristics were clarified based on the weight loss of coal; the amount of Hg released; and the emission of sulfur-containing gases during coal pyrolysis. Five species of mercury were determined in this study: exchangeable Hg (F1), carbonate + sulfate + oxide bound Hg (F2), silicate + aluminosilicate bound Hg (F3), sulfide bound Hg (F4), and residual Hg (F5), which are quite distinct in different rank coals. Generally, Hg enriched in carbonates, sulfates, and oxides might migrate to sulfides with the transformation of minerals during the coalification process. The order of thermal stability of different Hg speciation in coal is F1 < F5 < F2 < F4 < F3. Meanwhile, the release of Hg is accompanied with sulfur gases during coal pyrolysis, which is heavily dependent on the coal rank.
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Demin, Alexey, Grigorii Pavlov, and Mansur Khasiyatullov. "Thermo-chemical analysis and modeling of combustion of waste pyrolysis gaseous products." E3S Web of Conferences 247 (2021): 01056. http://dx.doi.org/10.1051/e3sconf/202124701056.
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The results of the study of joint pyrolysis of various types of waste (municipal solid waste, plastic waste, etc.) are presented. Preliminarily crushed and dried wastes were fed into the pyrolysis chamber of the model experimental setup. Thermal energy required for heating raw materials and carrying out their thermal destruction was obtained by burning a part of the pyrolysis gases. The rest of these gases were removed from the pyrolysis chamber and cooled. The temperature in the pyrolysis zone was about 650 °C. Plant productivity was up to 500 kg/h. The target product was the liquid phase, which is a mixture of hydrocarbon compounds. When organizing the processes, the yield of solid carbon residue was minimized. The obtained mass ratio of the final gas/liquid products was approximately equal to 1/6. Experimental results of the analysis of the chemical composition of the gas and liquid fractions are presented. The results of modeling the combustion of pyrolysis products at different amounts of supplied air are also shown. The operating parameters at which the optimum temperature level in the pyrolysis zone is maintained are numerically determined and recommended.
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Poletaev, N. I., V. G. Shevchuk, and M. E. Khlebnikova. "Energy and Technological Aspects of the Combustion of Ionized Gas-Dispersed Systems." Eurasian Chemico-Technological Journal 18, no. 3 (November 5, 2016): 215. http://dx.doi.org/10.18321/ectj427.
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This paper discusses the fl ame ionization effect on the combustion processes in gaseous suspensions of the dispersed fuels. It is shown that the two-phase fl ame ionization<br />affects almost all the processes of the fuel conversion – kinetics of the dispersed fuel combustion, processes of the interphase heat and mass transfer, processes of the nucleation and coagulation in the fl ame, formation of nanoscale products of the metal particles combustion. It is shown that the electrostatic interaction between the charged nanoparticles and ions or polar molecules in the gaseous phase leads to the appearance of molecular “pumps” that can signifi cantly change the kinetics of the heterogeneous chemical reactions and the heat exchange between particles and gas. The infl uence of the thermal ionization of the fl ame on the nucleation mechanism<br />and rate in gas-dispersed systems is discussed. The possibility of a barrier-free homogenous and heterogeneous nucleation in the dusty fl ame of metallic particles is shown. The effect of electrostatic and polarizing interactions of ions and molecules<br />on the kinetics of the ternary gas-phase reactions is considered. The infl uence of the monodisperse aerosol ionization degree on the kinetics of its coagulation is analyzed. It is concluded that electrostatic interaction between the particles strongly affects the inhibition of the coagulation process in gas-phase combustion products and the possibility of very fast (explosive) charged particle coagulation of monodisperse aerosols. The possibility of the targeted size of metal oxides nanoparticles control, controlled ionizing of dusty fl ames and the role of ion particle entrainment, the dependency of their size of the fl ame ionization degree are discussed. Some effects arising in complex plasma of condensed combustion products under its own electric fi elds in fl ames, also when the burning dust is entrained into a constant electric field and their practical applications for diagnosis are considered.
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Kajda-Szcześniak, Małgorzata, and Monika Czop. "Comparison of Pyrolysis and Combustion Processes of Vinyl Floor Panels Using Thermogravimetric Analysis (TG-FTIR) in Terms of the Circular Economy." Energies 15, no. 4 (February 18, 2022): 1516. http://dx.doi.org/10.3390/en15041516.
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The article analyzes the thermal degradation in the inert and oxidative atmosphere of waste vinyl panels, the main component of which is PVC. Both pyrolysis and incineration of plastic waste are difficult, complex and multifaceted processes due to several physical and chemical phenomena occurring during their performance. The coupled TG-MS (thermogravimetry-mass spectrometry) analysis combined with the Fourier transform infrared spectrometry (TG-FTIR) analysis was used to identify the decomposition mechanisms of waste vinyl panels. Thermogravimetric tests were carried out for two heating rates of 5 and 20 K/min in the temperature range of 40–1000 °C, mass losses were determined, and products resulting from thermal degradation were identified. It was found that the individual components decompose at different temperatures depending on the heating rate and the choice of an inert or oxidative atmosphere. Vinyl floor panels were treated in terms of secondary raw material, which, in the light of the circular economy, may constitute a potential energy or chemical resource.
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Nguyen, Phuc-Danh, Huu-Tri Nguyen, Pascale Domingo, Luc Vervisch, Gabriel Mosca, Moncef Gazdallah, Paul Lybaert, and Véronique Feldheim. "Flameless combustion of low calorific value gases, experiments, and simulations with advanced radiative heat transfer modeling." Physics of Fluids 34, no. 4 (April 2022): 045123. http://dx.doi.org/10.1063/5.0087077.
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Thermal radiation is the dominant mode of heat transfer in many combustion systems, and in typical flameless furnaces, it can represent up to 80% of the total heat transfer. Accurate modeling of radiative heat transfer is, thus, crucial in the design of these large-scale combustion systems. Thermal radiation impacts the thermochemistry, thereby the energy efficiency and the temperature sensitive species prediction, such as NOx and soot. The requirement to accurately describe the spectral dependence of gaseous radiative properties of combustion products interacts with the modeling of finite rate chemistry effects and conjugates heat transfer and turbulence. Additionally, because of the multiple injection of fuels and/or oxidizers of various compositions, case-specific radiative properties' expressions are required. Along these lines, a comprehensive modeling to couple radiation and combustion in reacting flows is attempted and applied to the simulation of flameless combustion. Radiation is modeled using the spectral line-based weighted-sum-of-gray-gases approach to calculate gaseous radiative properties of combustion products using the correlation of the line-by-line spectra of H2O and CO2. The emissivity weights and absorption coefficients were optimized for a range of optical thicknesses and temperatures encountered in the considered furnace. Efforts were also made on the development of a reliable and detailed experimental dataset for validation. Measurements are performed in a low calorific value syngas furnace operating under flameless combustion. This test rig features a thermal charge which can extract about 60% of combustion heat release via 80% of radiative heat transfer, making it of special interest for modeling validation. The comparison between the simulation and the experiment demonstrated a fair prediction of heat transfer, energy balance, temperature, and chemical species fields.
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Kryzhanovskiy, K. S. "THE SYSTEM OF AUTOMATIC COMBUSTION CONTROL IN GAS-BURNING PLANTS BY CORRECTIVE PARAMETER." Energy Technologies & Resource Saving, no. 3 (September 14, 2018): 66–71. http://dx.doi.org/10.33070/etars.3.2018.08.
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The wide application of gaseous fuels in technology and energy, its high cost, pose the task of improving the quality of its use. The task of automation of technological processes of thermal units heated by natural gas is to increase the safety of operation and the efficiency of their operation. This problem is especially acute in conditions of continuous operation of thermal units, when the state of the environment varies from day to day and from summer to winter. The temperature of the air for combustion, its humidity, the heat of combustion of the gas and the atmospheric pressure fluctuate particularly sharply. In these conditions, when putting into operation the heat unit, it is necessary to set such tinctures that, in the event of unfavorable external conditions, there always was enough oxygen to completelyburn the gas. This can be achieved by increasing the efficiency of the automatic control system of the ratio of the combustion components and the temperature parameters of the unit, according to the optimal regime for each particular technological process. To achieve this goal, we used the results of research into the chemical processes of interaction of combustion products using means for measuring the electrical parameters of a flame based on physical methods of ionization control of the combustion process. The established features and obtained results made it possible to develop a device for monitoring the ionization properties of the combustion process, on their basis, automatic control systems of burners for industrial heat x aggregates. Bibl. 7, Fig. 3.
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Boycheva, Silviya, Denitza Zgureva, Hristina Lazarova, Katerina Lazarova, Cyril Popov, Tsvetanka Babeva, and Margarita Popova. "Processing of high-grade zeolite nanocomposites from solid fuel combustion by-products as critical raw materials substitutes." Manufacturing Review 7 (2020): 22. http://dx.doi.org/10.1051/mfreview/2020019.
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High-grade zeolite nanocomposites are synthesized utilizing solid by-products from combustion of coal for energy production in Thermal Power Plants applying alkaline aging, hydrothermal and fusion-hydrothermal activation procedures. The obtained coal ash zeolites were studied with respect to their chemical and phase composition, morphology, surface parameters and thermal properties. It was found that they are distinguished in nanocrystalline morphology and significant content of iron oxide nanoparticles (γ-Fe2O3, α-Fe2O3, γ-Fe3O4) and doping elements (Cu, Co, Mn, V, W, etc.) transferred from the raw coal ash, and therefore they are assumed as nanocomposites. Coal fly ash zeolite nanocomposites are characterized by a mixed micro-mesoporous texture, significant concentration of acidic Brønsted centers due to their high surface insaturation, high chemical and thermal stabilty. This unique combination of compositional and textural properties predetermines the application of these materials as catalysts for thermal oxidation processes, anticorrosion barrier coatings, carbon capture adsorbents, matrices for hosting functional groups, detergents etc. Examples for coal fly ash zeolite applications for substitution of critical raw materials in practice are provided.
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Teh, Jun Sheng, Yew Heng Teoh, Heoy Geok How, and Farooq Sher. "Thermal Analysis Technologies for Biomass Feedstocks: A State-of-the-Art Review." Processes 9, no. 9 (September 8, 2021): 1610. http://dx.doi.org/10.3390/pr9091610.
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An effective analytical technique for biomass characterisation is inevitable for biomass utilisation in energy production. To improve biomass processing, various thermal conversion methods such as torrefaction, pyrolysis, combustion, hydrothermal liquefaction, and gasification have been widely used to improve biomass processing. Thermogravimetric analysers (TG) and gas chromatography (GC) are among the most fundamental analytical techniques utilised in biomass thermal analysis. Thus, GC and TG, in combination with MS, FTIR, or two-dimensional analysis, were used to examine the key parameters of biomass feedstock and increase the productivity of energy crops. We can also determine the optimal ratio for combining two separate biomass or coals during co-pyrolysis and co-gasification to achieve the best synergetic relationship. This review discusses thermochemical conversion processes such as torrefaction, combustion, hydrothermal liquefaction, pyrolysis, and gasification. Then, the thermochemical conversion of biomass using TG and GC is discussed in detail. The usual emphasis on the various applications of biomass or bacteria is also discussed in the comparison of the TG and GC. Finally, this study investigates the application of technologies for analysing the composition and developed gas from the thermochemical processing of biomass feedstocks.
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Camera, S., T. Pineda-Vásquez, F. M. Bianchi, L. S. Martins, E. Virmond, and E. S. Watzko. "ALTERNATIVES OF DOMESTIC WASTEWATER SLUDGE DRYING PROCESSES FOR ENERGY RECOVERY : A REVIEW." Revista de Engenharia Térmica 20, no. 3 (October 10, 2021): 44. http://dx.doi.org/10.5380/reterm.v20i3.83270.
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As communities grow, cities need to increase their capacity to collect and treat domestic wastewater. The need of larger domestic wastewater treatment plants and proper disposal of its solid waste has attracted the scientific community to research about new technologies that will use those systems and waste as a way to generate energy. The moisture content of a fuel effects the combustion products and the energy released by the reaction. Therefore, in order to make biomass to be a viable fuel option, the technological and scientific challenges of the drying process of wastewater sludge must be faced and overcome so the lowest moisture content level is achieved. Conventional drying processes as for example, direct and indirect thermal drying, are commonly used. However, other processes using renewable energy as for example solar drying are also being studied by the scientist around the world. Moisture content, physical-chemical properties as for example, heating values, composition, ash fusibility are all relevant properties taken into consideration when choosing a fuel for a specific application. The herein review is intended to present some existing domestic wastewater drying processes, alternative ways of improving the efficiency of those processes.
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Al-Moftah, Ahmad Mohamed S. H., Richard Marsh, and Julian Steer. "Thermal Decomposition Kinetic Study of Non-Recyclable Paper and Plastic Waste by Thermogravimetric Analysis." ChemEngineering 5, no. 3 (August 30, 2021): 54. http://dx.doi.org/10.3390/chemengineering5030054.
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The global net emissions of the Kyoto Protocol greenhouse gases (GHG), such as carbon dioxide (CO2), fluorinated gases, methane (CH4), and nitrous oxide (N2O), remain substantially high, despite concerted efforts to reduce them. Thermal treatment of solid waste contributes at least 2.8–4% of the GHG in part due to increased generation of municipal solid waste (MSW) and inefficient treatment processes, such as incineration and landfill. Thermal treatment processes, such as gasification and pyrolysis, are valuable ways to convert solid materials, such as wastes into syngas, liquids, and chars, for power generation, fuels, or for the bioremediation of soils. Subcoal™ is a commercial product based on paper and plastics from the source segregated waste that is not readily recyclable and that would otherwise potentially find its way in to landfills. This paper looks at the kinetic parameters associated with this product in pyrolysis, gasification, and combustion conditions for consideration as a fuel for power generation or as a reductant in the blast furnace ironmaking process. Thermogravimetric Analysis (TGA) in Nitrogen (N2), CO2, and in air, was used to measure and compare the reaction kinetics. The activation energy (Ea) and pre-exponential factor A were measured at different heating rates using non-isothermal Ozawa Flynn Wall and (OFW) and Kissinger-Akahira-Sonuse (KAS) model-free techniques. The TGA curves showed that the thermal degradation of Subcoal™ comprises three main processes: dehydration, devolatilization, and char and ash formation. In addition, the heating rate drifts the devolatilization temperature to a higher value. Likewise, the derivative thermogravimetry (DTG) results stated that Tm degradation increased as the heating rate increased. Substantial variance in Ea was noted between the four stages of thermal decomposition of Subcoal™ on both methods. The Ea for gasification reached 200.2 ± 33.6 kJ/mol by OFW and 179.0 ± 31.9 kJ/mol by KAS. Pyrolysis registered Ea values of 161.7 ± 24.7 kJ/mol by OFW and 142.6 ± 23.5 kJ/mol by KAS. Combustion returned the lowest Ea values for both OFW (76.74 ± 15.4 kJ/mol) and KAS (71.0 ± 4.4 kJ/mol). The low Ea values in combustion indicate shorter reaction time for Subcoal™ degradation compared to gasification and pyrolysis. Generally, TGA kinetics analysis using KAS and OFW methods show good consistency in evaluating Arrhenius constants.
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Jia, Guohai. "Combustion Characteristics and Kinetic Analysis of Biomass Pellet Fuel Using Thermogravimetric Analysis." Processes 9, no. 5 (May 14, 2021): 868. http://dx.doi.org/10.3390/pr9050868.
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Biomass pellet fuel is one of the development directions of renewable energy. The purpose of the article is to study the combustion characteristics of five kinds of biomass pellet fuel that can be used as biomass fuel and analyze their combustion kinetics. The thermogravimetric method (TG method) was used to analyze the combustion characteristics of five kinds of biomass pellet fuel and to calculate the index S of comprehensive combustion characteristic. The Arrhenius equation and the Coats–Redfern method were used to analyze the combustion kinetics of five kinds of biomass pellet fuel. The activation energy and pre-exponential factor were obtained according to different temperature ranges. Conclusions are as follows: The pyrolysis of five kinds of biomass pellet fuel mainly includes three stages: (1) water evaporation stage, (2) volatile component combustion stage, (3) fixed carbon oxidation stage. The TG curves of five kinds of biomass pellet fuel are roughly the same at the same heating rate. The peaks of thermal weight loss rate and maximum degradation rate are both in the high temperature range. The differential thermal gravity (DTG) curves of five kinds of biomass pellet fuel have an obvious peak. The peak temperature of the largest peak in the DTG curves is 280–310 °C. The first-order reaction equation is used to obtain the kinetic parameters in stages. The correlation coefficients are bigger than the value of 0.92. The fitting results are in good agreement with the experimental results. The activation energy of each sample is basically the same in each stage. The value in the volatile matter combustion stage is 56–542 kJ/mol, and the activation energy of the carbon layer slowly increases rapidly. The five kinds of biomass pellet fuels have good combustion characteristics and kinetic characteristics, and they can be promoted and applied as biomass pellet fuels in the future.
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Henne, Reny Aldo, Martha Andreia Brand, Viviane Aparecida Spinelli Schein, Ederson Rodrigues Pereira, and Bianca Schveitzer. "CHARACTERIZATION OF ASHES FROM FOREST BIOMASS COMBUSTION IN BOILERS: A SYSTEMIC VIEW OF POTENTIAL APPLICATIONS." FLORESTA 50, no. 1 (December 20, 2019): 1081. http://dx.doi.org/10.5380/rf.v50i1.61229.
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The description of the ash formation process during biomass burning and the determination of its physical and energetic properties are fundamental for the improvement of energy generation processes and the prospection of this residue’s reuse. Thus, this study aimed to evaluate the energy quality of the biomass burned and the ash generated in the boiler of a thermal power plant that uses forest biomass as fuel, as well as to consider the potential applications of this residue. To this end, the following properties of the ashes collected at four different collection points of the boiler (readler, hopper, scrubber, and decanter) were determined: moisture content; organic and inorganic elemental composition; proximate composition; and gross calorific value. The biomass was calcined in the laboratory and evaluated together with the ashes from calcination to compare the results. Although the wood biomass used by the thermal power plant was a residual material, it presented high energy quality. The physical, chemical and energetic properties of the ashes produced in the boiler varied according to the thermal power plant’s operation conditions. The ashes collected in the hopper showed a high energy potential, but further studies about furnace reconfiguration and retention time in the chamber are needed to allow its efficient burning for energy generation. Ashes from the hopper have the potential to be used as household charcoal and as biochar. The results obtained in this study are fundamentally important and provide a basis for further studies.
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Mortari, D. A., I. Avila, A. M. Dos Santos, and P. M. Crnkovic. "STUDY OF THERMAL DECOMPOSITION AND IGNITION TEMPERATURE OF BAGASSE, COAL AND THEIR BLENDS." Revista de Engenharia Térmica 9, no. 1-2 (December 31, 2010): 81. http://dx.doi.org/10.5380/reterm.v9i1-2.61937.
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In Brazil, due to its availability, sugar cane bagasse has a high potential for power generation. The knowledge of ignition behavior, as well as the knowledge of the chemical kinetics, in of fuels combustion process is important features in boilers projects and in the stability of the combustion process control. The aim of this study is to investigate the thermal behavior of sugar cane bagasse, coal and their blends. The methodology proposed by Tognotti et al. (1985) was applied to determine the ignition temperature for all samples. Ignition temperatures were 256oC for neat bagasse and 427oC for neat coal, and 275oC for both blends (50-50% and 25-75%). The Model-Free Kinetics was applied to determine the apparent activation energy (Eα) of the thermal decomposition of sugar cane bagasse. For the two major events of mass loss of bagasse which correspond to the thermal decomposition of organic matter (mainly hemicellulose, cellulose and lignin), average values of Eα were obtained for both combustion and pyrolysis processes. In synthetic air atmosphere, the Eα were 170.8±26.3 kJ⋅mol-1 and 277.8±58.6 kJ⋅mol-1, while in nitrogen atmosphere, the Eα were 185.0 ± 11.4 kJ⋅mol-1 and 82.1±44.4 kJ⋅mol-1. The results obtained can be explained by synergistic effects when both bagasse and coal were blended, changing the fuel reactivity.
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Stobart, R. K. "An availability approach to thermal energy recovery in vehicles." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, no. 9 (September 1, 2007): 1107–24. http://dx.doi.org/10.1243/09544070jauto463.
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Availability is a well-established and widely recognized way of describing the work-producing potential of energy systems. A first-law analysis is helpful in setting the energy context and ensuring that energy flows balance, but it is a second-law analysis based on availability that places an upper bound on the potential work output. In this analysis a new approach to thermal management intended for vehicle propulsion is examined and developed. Starting with a simple analysis of the chemical energy flow, a realistic heat exchange performance is introduced to establish a practical architecture. Within this framework, the availability analysis shows that effective thermal efficiencies of between 25 and 30 per cent are feasible. With a spark ignition engine operating at a high load condition, and the thermal recovery system at an operating pressure of 100 bar, the maximum efficiency possible with a steady flow work-producing device is 37 per cent (with fully reversible thermodynamic processes). In a water-based thermal recovery system, work could only reasonably be produced with heat transfer from a reservoir at the saturation temperature corresponding to the operating pressure. At 100 bar the maximum efficiency would be 33 per cent. In a different mode of operation, where heat is transferred incrementally to a thermal accumulator and work produced as required, the efficiency is 32 per cent at only 20 bar operating pressure. These efficiency values apply to work production to supplement a combustion engine at any operating condition. An analysis of a reciprocating expander as the work-producing device shows substantial flexibility in operation. Control of system operating pressure is shown to be of value in that periodic adjustments enhance the availability content of the thermal reservoir. The operating pressure of a fluid power system is related to the temperature of operation, and therefore the heat transfer processes. Choice of too high a pressure leads to reduced heat transfer, and ultimately a reduction in work output. There is an optimum condition that can be selected at design time and maintained during the running of the system.
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Bożym, Marta, Arkadiusz Gendek, Grzegorz Siemiątkowski, Monika Aniszewska, and Jan Malaťák. "Assessment of the Composition of Forest Waste in Terms of Its Further Use." Materials 14, no. 4 (February 18, 2021): 973. http://dx.doi.org/10.3390/ma14040973.
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This paper presents the results of the analysis of the chemical composition and content of heavy metal contamination in forest logging residues, in order to assess the possibility for their further utilisation. The samples were divided into 9 groups, which included coniferous tree cones, wood, and other multi-species logging residues. The elementary composition, ash content, and calorific value were determined as energy use indicators for the samples. Additionally, the content of heavy and alkali metals, which may affect combustion processes and pollutant emissions, was tested. The high content of heavy metals may also disqualify these residues for other uses. The research shows that the test residues are suitable for energy use due to their high calorific value and low content of heavy metals. However, an increased ash content in some samples and the presence of alkali metals, causing high-temperature corrosion of boilers, may disqualify them as a potential fuel in the combustion process. The forest residues may be used in other thermal processes such as pyrolysis or gasification. A low content of heavy metals and a high content of organic matter permit the use of these residues for the production of adsorbents or composite materials.
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Žarković, Mileta, Vladimir Antonijević, Aleksandar Milićević, and Srđan Belošević. "Application of CFD and Artificial Intelligence for Prediction of Biomass Particle Burnout and Residence Time in the Reactor." Energija, ekonomija, ekologija XXIV, no. 1 (2022): 40–46. http://dx.doi.org/10.46793/eee22-1.40z.
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In planning the development of the energy sector, increasing attention is paid to renewable energy sources, such as biomass. The process of (co)combustion of biomass in boiler furnaces is extremely complex with many coupled parameters. Because of that, the development and application of computational fluid mechanics and artificial intelligence are approached, as efficient tools for the analysis of physical and chemical processes that take place during combustion. The paper presents the applied CFD code and the methodology of application of adaptive neuro-fuzzy systems (ANFIS) in the field of machine learning for predicting the biomass particle burnout and residence time in a 150 kW reactor. Test cases for combustion of three types of pulverized biomass with different diameters and shape factors were considered. A database with the values of mass burnout and residence time of particles was obtained by means of numerical simulations using the in-house developed computer code. The results of ANFIS application on the formed base indicate the possibility of a reliable assessment of mass burnout and residence time of particles, based on knowledge of the type, diameter and shape factors of the fuel introduced into the furnace. The presented models represent a good basis for the implementation and application of CFD and ANFIS models at various thermal energy plants, in order to assess the efficiency of fuel combustion in the furnace.
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Zhang, Yangsheng, and Gregory C. Stangle. "A micromechanistic model of the combustion synthesis process: Part I. Theoretical development." Journal of Materials Research 9, no. 10 (October 1994): 2592–604. http://dx.doi.org/10.1557/jmr.1994.2592.
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A theoretical model of the combustion synthesis process has been developed. In particular, a set of nonlinear and interrelated partial differential equations is given that accounts for all of the relevant physical and chemical processes that occur during the combustion synthesis process. The appropriate conservation equations for thermal energy, mass, and momentum densities are correctly described—for each phase at each point in the sample—at all times during the process. In addition, details of the necessary interphase transfer terms are expressed in a number of constitutive relationships, in which the dependence of an independent variable upon its dependent variable(s) is given explicitly. In doing so, microstructural details are accounted for, derived primarily from percolation concepts as applied to disordered porous media. All assumptions that are incorporated into the theoretical model have been tabulated in detail. This theoretical model establishes an approach to the development of a sound, quantitative, and fundamental understanding of the combustion synthesis process, particularly with respect to the processing-microstructure-properties relationship. It also provides a point of departure for conducting detailed, quantitative computer experiments of the combustion synthesis process.
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Sifat, Najmus S., and Yousef Haseli. "A Critical Review of CO2 Capture Technologies and Prospects for Clean Power Generation." Energies 12, no. 21 (October 30, 2019): 4143. http://dx.doi.org/10.3390/en12214143.
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With rapid growth in global demand for energy, the emission of CO2 is increasing due to the use of fossil fuels in power plants. Effective strategies are required to decrease the industrial emissions to meet the climate change target set at 21st Conference of the Parties (COP 21). Carbon capture and storage have been recognized as the most useful methods to reduce the CO2 emissions while using fossil fuels in power generation. This work reviews different methods and updates of the current technologies to capture and separate CO2 generated in a thermal power plant. Carbon capture is classified in two broad categories depending on the requirement of separation of CO2 from the gases. The novel methods of oxy combustion and chemical looping combustion carbon capture have been compared with the traditional post combustion and precombustion carbon capture methods. The current state of technology and limitation of each of the processes including commonly used separation techniques for CO2 from the gas mixture are discussed in this review. Further research and investigations are suggested based on the technological maturity, economic viability, and lack of proper knowledge of the combustion system for further improvement of the capture system.
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Tang, Yan, Wei-Chun Chen, Hai-Lin Zhou, Jing-Yu Zhao, Chi-Min Shu, and An-Chi Huang. "Study of Gases and Thermal Behavior of Oxidized Coal during Spontaneous Combustion Process." Processes 10, no. 9 (September 14, 2022): 1849. http://dx.doi.org/10.3390/pr10091849.
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Coal spontaneous combustion is one of the most severe and constant hazards in the coal industry. Understanding the mechanisms is the basis for effective hazard control in the coal-producing process. This paper investigated two types of oxidized coal samples from the re-mining faces of an underground coal mine. Proximate analysis, elemental analysis, surface analysis, temperature-programmed experiments, and differential scanning calorimetry analysis were conducted to study the spontaneous combustion characteristics. Various reaction mechanism functions were adopted to calculate the kinetic parameters, and multiple linear regression was performed to simulate the reaction behavior. The results show that the thermal decomposition of the oxidized coal followed a two-stage reaction model. The first stage reaction occupied smaller apparent activation energy and promoted the second stage reaction, dominating the heat production. Therefore, significant prevention measures for coal spontaneous combustion should be conducted and emphasized appropriately in the first stage to break the continuous reaction. The findings of this study can serve as a reference for predicting and preventing spontaneous combustion of oxidated coal.
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Półka, Marzena. "Leather Thermal and Environmental Parameters in Fire Conditions." Sustainability 11, no. 22 (November 16, 2019): 6452. http://dx.doi.org/10.3390/su11226452.
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The thermal decomposition of leather-product combustion produces some inflammable and harmful compounds after tanning, fat liquoring, dyeing, and finishing processes. These organic compounds are ignited and release a lot of toxic gases and smoke in fire conditions, polluting the atmosphere air. On this account, it is very important to know leather safety performance for fire prevention. The flammability and thermal stability of types of leather at thermal expositions stimulating fire conditions were analyzed. Five types of leather were used in experimental testing, four of animal origin and an artificial one. Results showed that, in the analyzed heat exposure, the highest average heat-release rate (174 kW/m2) and smoke generation, and the lowest temperature of the beginning of thermal decomposition, were recorded for the artificial leather. Leather flammability essentially depends on the type of applied energy stimulus, as well as hide composition and origin. A possible cause for differences in the obtained results of the leather analyses is the percentage of certain leather components and their chemical composition.
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VORONIN, D. V. "TRIGGERING OF DETONATION PROCESSES IN PROPULSION CHAMBER." Gorenie i vzryv (Moskva) - Combustion and Explosion 14, no. 2 (May 31, 2021): 40–45. http://dx.doi.org/10.30826/ce21140204.
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The Navier-Stokes equations have been used for numerical modeling of chemically reacting gas flow in the propulsion chamber. The chamber represents an axially symmetrical plane disk. Fuel and oxidant were fed into the chamber separately at some angle to the inflow surface and not parallel one to another to ensure better mixing of species. The model is based on conservation laws of mass, momentum, and energy for nonsteady two-dimensional compressible gas flow in the case of axial symmetry. The processes of viscosity, thermal conductivity, turbulence, and diffusion of species have been taken into account. The possibility of detonation mode of combustion of the mixture in the chamber was numerically demonstrated. The detonation triggering depends on the values of angles between fuel and oxidizer jets. This type of the propulsion chamber is effective because of the absence of stagnation zones and good mixing of species before burning.
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Acha, Esther, Alexander Lopez-Urionabarrenechea, Clara Delgado, Lander Martinez-Canibano, Borja Baltasar Perez-Martinez, Adriana Serras-Malillos, Blanca María Caballero, et al. "Combustion of a Solid Recovered Fuel (SRF) Produced from the Polymeric Fraction of Automotive Shredder Residue (ASR)." Polymers 13, no. 21 (November 3, 2021): 3807. http://dx.doi.org/10.3390/polym13213807.
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The use of alternative fuels derived from residues in energy-intensive industries that rely on fossil fuels can cause considerable energy cost savings, but also significant environmental benefits by conserving non-renewable resources and reducing waste disposal. However, the switching from conventional to alternative fuels is challenging for industries, which require a sound understanding of the properties and combustion characteristics of the alternative fuel, in order to adequately adapt their industrial processes and equipment for its utilization. In this work, a solid recovered fuel (SRF) obtained from the polymeric fraction of an automotive shredder residue is tested for use as an alternative fuel for scrap preheating in an aluminium refinery. The material and chemical composition of the SRF has been extensively characterized using proximate and ultimate analyses, calorific values and thermal degradation studies. Considering the calorific value and the chlorine and mercury contents measured, the SRF can be designated as class code NCV 1; Cl 2; Hg 2 (EN ISO 21640:2021). The combustion of the SRF was studied in a laboratory-scale pilot plant, where the effects of temperature, flow, and an oxidizer were determined. The ash remaining after combustion, the collected liquid, and the generated gas phase were analysed in each test. It was observed that increasing the residence time of the gas at a high temperature allowed for a better combustion of the SRF. The oxidizer type was important for increasing the total combustion of the vapour compounds generated during the oxidation of the SRF and for avoiding uncontrolled combustion.
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Petrovic, David, Dusko Djukanovic, Dragana Petrovic, and Igor Svrkota. "Contribution to creating a mathematical model of underground coal gasification process." Thermal Science 23, no. 5 Part B (2019): 3275–82. http://dx.doi.org/10.2298/tsci180316155p.
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Underground coal gasification, as an auto thermal process, includes processes of degasification, pyrolysis, and the gasification itself. These processes occur as a result of a high temperature and the management of coal combustion during addition of gasification agent. Air, water vapor mixed with air, air or water vapor enriched with oxygen, or pure oxygen, may be used as gasification agents. Resulting gas that is extracted in this process may vary in chemical composition, so it is necessary to adjust it. That is the reason why it is necessary to develop a mathematical model of the underground gasification process prior to any operations in coal deposit, in order to obtain as much accurate prediction of the process as possible. Numerical calculation provides prediction of gas mixture?s chemical composition, which enables calculation of gas components? energy contents and total energy content of the gas in predicted underground coal gasification process. It is one of the main criteria in the economic assessment of underground coal gasification process. This paper, based on available data on researches in this area, provides a contribution to creation of mathematical model of underground coal gasification.
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Paprika, Milijana, Mirko Komatina, Milica Mladenovic, Goran Zivkovic, and Dragoljub Dakic. "Mechanism of primary fragmentation of coal in fluidized bed." Thermal Science 20, suppl. 1 (2016): 125–32. http://dx.doi.org/10.2298/tsci150603224p.
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In order to lay a foundation of a credible primary fragmentation model, a theoretical analysis of the thermo-mechanical processes in a devolatilizing solid fuel particle was carried out. The devolatilization model comprises heat transfer, chemical processes of generation of gaseous products of combustion (volatiles), volatile transfer, and solid mechanic processes. A spatial and temporal analysis of the stresses within the particle showed that the radial stress is caused primarily by the pressure of generated volatiles. This stress monotonously decreases from the particle center towards the particle surface, without changing its sign. The tangential stress is caused primarily by the thermal shock. Close to the surface, it changes its sign. In the particle cross-section, the radial stress prevails close to the particle center, whilst the tangential stress is dominant in the surface region. At the points where these stresses exceed the particle tensile strength, cracks occur. Cracks extend tangentially close to the surface, and radially close to the center of the particle.
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Bujak, Janusz, Piotr Sitarz, Krzysztof Bujak, Sebastian Majkowski, and Rafał Pasela. "Estimation Complete Combustion Coefficient in Rotary Kilns." Energies 15, no. 3 (February 3, 2022): 1143. http://dx.doi.org/10.3390/en15031143.
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This paper presents a model-based analysis of variability of thermodynamic and chemical parameters in a rotary kiln (RK) during thermal treatment of animal waste. The core process of chemical treatment of waste takes place in RKs; the process involves heating, gasification and partial combustion of the waste. Control over these parameters, and especially the level of complete combustion, determines the quality and efficiency of the process. In operational practice, control and analysis of the variability of process parameters is complicated by the high degree of simultaneity of individual transformations, random disruptions of the process and metrological difficulties resulting from high temperature and chemical activity of the materials being processed. The purpose of preparing the model was to obtain a tool for predicting variability of selected process parameters. By definition, model calculations assume no influence of disturbances on output values, which makes it possible to acquire accurate results that can be compared with corresponding empirically obtained data. The result of the analyses conducted is a theoretical model of the analysed process and a graphical presentation of the calculation results in the form of graphs and charts. A formula for calculating the level of complete combustion and the results of calculation of this index on the basis of empirical data from an industrial waste incineration plant are also presented herein. The presented model is a useful tool providing an insight into interdependencies between selected process parameters and facilitating design of corrective actions oriented towards process optimisation.
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Osorio-Castiblanco, Diego F., Gwendolyn Peyre, and Juan F. Saldarriaga. "Physicochemical Analysis and Essential Oils Extraction of the Gorse (Ulex europaeus) and French Broom (Genista monspessulana), Two Highly Invasive Species in the Colombian Andes." Sustainability 12, no. 1 (December 19, 2019): 57. http://dx.doi.org/10.3390/su12010057.
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Gorse (Ulex europaeus) and French broom (Genista monspessulana) are two highly invasive species that have become a threat to tropical countries, especially in Andean ecosystems. This research focused on providing a physicochemical characterization and essential oils extraction of both species to better understand their potential valorization and guide further environmental management efforts. For this purpose, the following analyses were conducted for both species: higher heat value (HHV), elemental analysis, proximate analysis, thermogravimetric analysis to obtain constituent natural polymers (hemicellulose, cellulose, and lignin), and extraction of essential oils and other interest chemical compounds through supercritical fluids. Ecological closeness was found between the two species mostly regarding HHV, fixed carbon, and volatile matter, which calls for similar potential uses. Both species were also found to be suitable for combustion processes, gasification, extraction of chemical compounds, and use of lignocellulosic content; however, only U. europaeus appeared suitable for activated carbon obtention. Therefore, this work provided relevant data that can be used as preliminary basis to establish strong scientifically-based management and control strategies for these two invasive species. We recommend focusing primarily on thermal processes such as pyrolysis, gasification, or combustion, and also essential oils extractions of acetic acid, dodecanoic acid, anagyrine, amylene hydrate, caulophylline, and maltol in the future.
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Goldšteins, Linards, Māris Gunārs Dzenis, Raimonds Valdmanis, Maija Zaķe, and Alexandr Arshanitsa. "Thermo-Chemical Conversion of Microwave Selectively Pre-Treated Biomass Blends." Energies 15, no. 3 (January 20, 2022): 755. http://dx.doi.org/10.3390/en15030755.
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Possibilities of more efficient use of regional lignocellulosic resources (wood, wheat straw, peat) of different origin for an environmentally friendly energy production using selectively MW pre-treated blends of commercial wood or wheat straw pellets with raw peat pellets are studied. A hypothesis is proposed and tested that selective MW pre-treatment of wood or wheat straw pellets at the frequency 2.45 GHz and blending of MW pre-treated pellets with raw peat pellets can be used to enhance and control the thermo-chemical conversion of biomass blends. To test this hypothesis, a combined experimental study and mathematical modelling of the processes were performed. The thermo-chemical conversion of selectively activated blends was experimentally studied using a batch-size pilot device, which consists of a biomass gasifier and a combustor. To evaluate the effect of selective MW pre-treatment of biomass pellets on the thermo-chemical conversion of pre-treated blends, measurements of the kinetics of weight loss, yield of combustible volatiles, flame temperature, heat output of the device, and composition of emissions were made at different MW pre-treatment regimes of wheat straw and wood pellets and different mass fractions of pre-treated pellets in biomass blends. The developed novel 2D numerical model of thermo-chemical conversion of MW pre-treated straw confirmed that the pre-treatment of wheat straw pellets increases the generated heat and significantly affects the temperature distribution in the flame/bed zones. It was confirmed that MW pre-treatment leads to a faster thermal decomposition of biomass pellets, synergistically activating the non-treated parts of blends. The overall improved yield of combustible volatiles and their complete combustion provide a surplus of heat production by limiting the formation of GHG emissions, which allows promoting MW pre-treated biomass of different origin as efficient regional bioenergy resources for energy production.
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Bobkov, Vladimir I., and Maxim I. Dli. "PECULIARITIES OF CALCULATION OF HEAT AND POWER BALANCE FOR ROASTING CONVEYOR MACHINE." Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 58 (2021): 70–76. http://dx.doi.org/10.36807/1998-9849-2021-58-84-70-76.
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The work examines the chemical and energotechnological processes of pellet production from fine apatite-nepheline raw materials: moisture removal, carbonate dissociation, taking into account the thermal and technological features of the functioning of roasting conveyor machines. It was established that the same physicochemical processes differ in quantitative characteristics in the process zones of heating, roasting and recovery. The need of the charge for the heat carrier gas for the corresponding zones, the content of carbon dioxide, iron oxide and carbon in dry pellets, which depend on the chemical composition, the degree of carbon dioxide release, iron oxide oxidation and carbon combustion are taken into account. According to the results of the experimental data and depending on the composition of the charge the following characteristics are calculated for each of the zones: heat consumption for limestone decomposition, specific volume of carbon dioxide, heat output during the oxidation of iron oxide, oxygen flow for iron oxide oxidation, heat introduced by carbon dioxide, initial and final heat of heat carrier gas. The mathematical description of heat and power peculiarities of functioning of roasting conveyor machines is proposed. It is based on energy-balance mathematical models and takes into account thermally activated chemical-energotechnological processes, which take place in apatite-nepheline technogenic raw materials during heating
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Bond, Nicole, Robert Symonds, and Robin Hughes. "Pressurized Chemical Looping for Direct Reduced Iron Production: Carbon Neutral Process Configuration and Performance." Energies 15, no. 14 (July 19, 2022): 5219. http://dx.doi.org/10.3390/en15145219.
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To achieve net-zero iron and steel production by 2050, many iron and steel producers are turning to direct reduced iron (DRI)—electric arc furnace (EAF) steel production as an opportunity to achieve significant CO2 emissions reductions relative to current levels. However, additional innovations are required to close the gap between DRI and net-zero steel. Pressurized chemical looping-DRI (PCL-DRI) is a novel technology explored to meet this target, in which the reformer firebox and fired process gas heaters are replaced with PCL combustion units. Captured CO2 is conditioned and compressed for pipeline transportation and storage/utilization. The performance of two different PCL-DRI configurations relative to traditional DRI processes was explored via process simulation: a Midrex-type process and an Energiron-type process. The PCL-DRI processes were shown to have equivalent or lesser total fuel consumption (8% reduction) compared to the base cases, and greater process water production (170–260% increase), with minimal or no loss in thermal efficiency. PCL-DRI is a strong competitor to alternative methods of reaching net-zero DRI due to lower energy penalties for carbon capture, no required changes to stream chemistry in or out of the EAF, and no requirement for hydrogen infrastructure.