Thermal Decomposition Of Biomass Research Articles

Functions of local structural surrounding in activity of Ca-containing catalysts for vapor upgrading during biomass thermal decomposition

The catalytic activity of calcium-containing complex oxides with perovskite structure (CaTiO3), brownmillerite structure (Ca2Fe2O5 and Ca2FeAlO5), spinel structure (CaAl2O4), and pseudowollastonite structure (CaSiO3) was compared to CaO for the upgrading of Oakwood fast pyrolysis vapors. Initial catalyst particle sizes range between 0.61 and 3.21 μm, while the BET surface area is between 0.2 and 8.7 m2/g. In contrast to CaO, the complex oxides compounds demonstrated negligible CO2 and H2O chemisorption during catalytic fast pyrolysis, thereby a low deactivation of catalysts, good structural and morphological stability and thus high reusage feasibility. Due to their unique features, Ca-containing catalysts were found to promote specific reaction pathways, such as the conversion of guaiacol to 3-methyl phenol, 4-ethenyl-2-methoxyphenol to 4-ethyl-2-methoxyphenol, 1-(4-hydroxy-3,5-dimethoxyphenyl)ethanone to 3,5-dimethoxy acetophenone and long chain carboxylic acids to acetic acid through a multitude of reaction routes including demethylation/demethoxylation, hydrogenation and hydrodeoxygenation, oxidative cleavage, and dehydration reactions. CaO and Ca2Fe2O5 promoted the alkylation reactions within the methoxy phenolics, whilst CaSiO3 promoted hydrogenation reactions. The formation of acetic acid was promoted over Ca2FeAlO5, CaAl2O4, and CaSiO3, while acetone, 2-butanone, new cyclic C5 ketones were revealed over CaO. The resulting ketonic fraction was noticeably affected by the use of Ca2Fe2O5 and CaAl2O4 catalysts.

A review on biomass thermal-oxidative decomposition data and machine learning prediction of thermal analysis

Thermochemical conversion is the most economical approach to recovering energy and alternative fuels from biomass feedstock. This work first reviews the literature data on thermal-oxidative decomposition for common biomass types and forms a database of 18 parameters, including element, proximate, and thermogravimetric analysis (TGA). Then, an Artificial Neural Network (ANN) model is developed for the prediction of TGA data. Pearson correlation coefficient analysis reveals that the influence of environment heating rate on biomass thermal decomposition is larger than that of fuel properties. By inputting biomass elemental/proximate analysis and heating rate, the ANN model successfully predicts 8 key TGA parameters, namely, pyrolysis-onset temperature, peak pyrolysis temperature, oxidation-dominant temperature, peak oxidation temperature, oxidation-end temperature, peak pyrolysis rate, oxidation-dominant rate, and peak oxidation rate, with R2 values greater than 0.98. A better performance can be achieved when all ten input features are considered. Final, an open-access online software, Intelligent Fuel Thermal Analysis (IFTA), is developed to predict thermal-oxidative decomposition across a wide range of heating rates and biomass types. This work provides a better understanding of biomass thermal-oxidative decomposition dynamics and a shortcut to obtain key parameters of biomass degradation without TGA tests.

Effect of alkali and alkali earth metals on reactions of stable free radicals during biomass pyrolysis: An in-situ EPR study

Stable free radicals are the long-lived macromolecule radicals formed in pyrolysis, and their reactions play an essential role in biochar formation. The alkali and alkaline earth metals (AAEMs) in biomass might be involved in the radical reactions during pyrolysis. Figuring out the effect of AAEMs on the reactions of stable free radicals can further understand the radical reaction mechanism and the formation of biochar in pyrolysis. In this paper, the in-situ electron paramagnetic resonance (EPR) spectroscopy was used to detect the stable free radicals in cocoanut pyrolysis, and the effect of AAEMs was analysed by the comparative experiments. The results indicate that the stable free radicals in nascent chars, which are generated from the thermal decomposition of biomass, could react and couple with each other. The AAEMs in biomass improve the activity of stable free radicals and promote the radical-radical coupling during high-temperature pyrolysis above 400 °C, which inhibits the condensation of aromatic structure and generates more weak bonds in hot nascent char. After stopping the heating, the weak bonds will be broken by cooling stress, thus inducing radical reactions and further changing the char structure.

Dispersibility study of GO-like biocarbons obtained from the thermal decomposition of biomass: Phragmites australis and Carya illinoinensis

In this work, we develop a cost-effective and straightforward methodology to upgrade earth-abundant biomass into high-value-added graphene oxide-like dispersions. The main idea is based on a controlled thermal treatment allowing the conversion of the two different biomass sources with different lignin content (Phragmites australis and Carya illinoinensis), in an air atmosphere and in a short time (15 min); no additional functionalization, catalysts, or high temperatures are necessary. The interface of both biocarbons is distinguished by different proportions of hybridized carbons (CC and C–C) and functional oxygenated groups (OH, C–O, CO, C–OH), characteristic of amphiphilic graphene oxide and responsible of the interactions with solvents. The results show that the most stable dispersions were achieved using polar solvents (Zave < 300 nm, ζ ±15 mV) with no surfactants. Also, we determined the dispersion states (qualitatively and quantitatively) and their zeta potential for all dispersions as well as a graphical map of their behavior, indicating that polar solvents promote the formation of stable dispersions, whereas non-polar solvents sediment instantly. The strategy reported here may be a feasible and unique approach to formulate stables dispersions using graphene based-materials obtained in a sustainable way, which have the potential for future applications in ink formulation for inkjet printing and electrochemical applications.

Unravelling the Recent Developments in the Production Technology and Efficient Applications of Biochar for Agro-Ecosystems

Considerable interest is being shown in using biochar production from waste biomass with a variety of disciplines to address the most pressing environmental challenges. Biochar produced by the thermal decomposition of biomass under oxygen-limited conditions is gaining popularity as a low-cost amendment for agro-ecosystems. The efficiency of biochar formation is affected by temperature, heating rate, feedstock type, particle size and reactor conditions. Properties such as pH, surface area and ash content of produced biochar increases with increasing temperatures. Biochar produced at lower heating rates may have high porosity and be beneficial for morphological changes in the soil. Biochar can help to enhance soil health and fertility as well as improve agricultural yield. As a result, biochar can assist in increasing food security by promoting sustainable agricultural systems and preserving an eco-friendly environment. Biochar is also widely being used as a sorbent for organic and inorganic pollutants, owing to its large surface area, allowing it to be immobilized from soil with ease. The functional groups and charges present on the surface of biochar play an important role in pollutants removal. This review focuses on the mechanisms of biochar production using different waste materials as a feed stock, factors that influence biochar quality as well as application of biochar in agricultural soil and their reclamation as well. This article also discusses knowledge gaps and future perspectives in the field of biochar-based toxic-pollution remediation.

Slow pyrolysis experimental investigation of biomass tar formation and hydrogen production by tar reforming

The characteristics of pyrolysis tar and catalytic hydrogen production during tar reforming with catalysts were investigated. Through the pyrolysis experiment of wheat straw at 400–800 °C, the change of tar yield and tar composition with pyrolysis temperature was obtained. In order to remove tar, different nickel-based catalysts were prepared and catalytic experiments were carried out. The results showed that the pyrolysis tar yield first increased and then decreased with the increase of temperature, and the maximum tar yield was 32.82% at 700 °C. The generation of tar mainly comes from the thermal decomposition of biomass before 500 °C, the homogeneous reactions of tar compositions begin to occur after 500 °C. Through the characterization of the catalysts and their catalytic performance, it was found that due to the interaction of Ni and Ce on the support surface, Ni particles were more evenly distributed on the surface of the support. By adding Ce into Ni/HZSM-5, more oxygen vacancies are formed on the catalyst surface, which makes the catalyst have higher reducibility and more active sites. Compared with 9Ni/HZSM-5, 9Ni3Ce/HZSM-5 has a better catalytic performance with the tar conversion of 89.34% and H2 composition of 0.43.

Experimental and simulation study of peanut shell-derived activated carbon and syngas production via integrated pyrolysis-gasification technique

Carbonaceous materials are among the most appropriate and widely used materials in the field of energy production, conversion, and storage. According to recent studies, biochar-based catalytic supports and adsorbents have shown great potential in the fields of energy production and the adsorption and storage of various gases due to their adjustable surface chemistry and porosity. In the present study, the pyrolysis of peanut shell to produce activated carbon as a precursor for catalyst support was investigated. Acid washing pretreatment was performed on raw biomass before pyrolysis to remove metals and impurities and reduce the ash content of the biomass. Before pyrolysis, thermogravimetric analysis was performed to determine the temperature range of biomass thermal decomposition. Pyrolysis was carried out at temperatures of 300, 400, and 500 °C to study the effect of pyrolysis temperature on biochar yield. KOH-activation on biochar was followed by subsequent pyrolysis at 650 °C to produce activated carbon. To study the effect of pyrolysis temperature and KOH activation on the structural and physiochemical characteristics of biochar, nitrogen adsorption/desorption and FTIR analyses were conducted. The pore size of the activated carbon surface changed from mesoporous to microporous with increasing the pyrolysis temperature and subsequent KOH activation, and the biochar specific surface area increased from 3.5 to 363.1 m2 g-1. In order to evaluate and optimize the operating conditions of the biochar and syngas production processes on larger scales, the integrated pyrolysis and gasification processes were simulated in Aspen Plus software. The effects of temperature, pressure, and air to biomass ratio on biochar production rate and H2/CO ratio were evaluated. A temperature of 650 °C, a pressure of 1 bar and an air to biomass ratio of 0.1 were selected as optimum operating conditions to simultaneously achieve maximum biochar production and maintain the quality of synthetic gas. The findings of the experimental and simulation sections of this study could provide a useful guide for the industrial-scale production of biochar and activated carbon as a catalytic support in various chemical production processes, as well as a water polutant adsorbent and gas adsorbent for various gas purification and storage processes.

Biomass waste as a clean reductant for iron recovery of iron tailings by magnetization roasting.

The magnetization roasting with coal as primary reductants adds cost and causes environmental pollution. Therefore, it is of great importance to investigate the biomass application as a reductant for magnetization roasting to recover iron from low-utilization iron tailings for emission mitigation and green utilization. This study systematically investigated the impact of biomass (pyrolysis gas from agricultural and forestry waste) as a reductant on the conversion of iron tailings to magnetite in magnetization roasting. Additionally, the thermal decomposition of biomass, phase transformation and microstructure evolution of iron tailings were analyzed by TG, XRD, BET, and other methods to elucidate the conversion mechanism for facilitating magnetized hematite in iron tailings with biomass-derived gas. The results showed that woody biomass was a more appropriate reductant for magnetization roasting; 650°C was the optimal temperature for the complete transformation of hematite to magnetite by reduction roasting with biomass waste. Through magnetic separation, the concentrate with an iron grade of 62.04% and iron recovery of 95.29% was obtained, and the saturation magnetization was enhanced from 0.60 emu/g to 58.03 emu/g of iron tailings. During the magnetization roasting, CO and H2 generated from biomass reduced the hematite in tailings particles from interior to exterior, forming a loose structure with rich microfissures, facilitating the subsequent separation operations. This study offers a novel reference for applying biomass to exploit hematite minerals and shows the potential of biomass for energy savings and emission reduction in the utilization of iron tailing resources.

Estudio computacional de la pirólisis rápida de biomasa en un reactor de lecho fluidizado

Biofuels are considered a promising source of renewable energy. Pyrolysis uses heat in an inert atmosphere to break down biomass and produce biofuels like bio-oil (tar) and synthesis gas. This paper presents a computational study of fast biomass pyrolysis in a laboratory fluidized reactor. A laminar flow regime and an Eulerian-Eulerian approach were considered. A comprehensive kinetic model consisting of sixteen irreversible, first-order reactions was coupled with conservation equations of mass, momentum, and energy. The computational model was validated with data reported in the literature. The effect of biomass type and reactor temperature on the thermal decomposition of biomass were analyzed, finding a direct relationship between the content of cellulose and production of tar and similarly between the content of lignin and production of char. Also, the absence of lignin in the biomass dramatically changes the tar and gas compositions. Energy requirements, temperature contours, the composition of the exit gases, and final product yields (tar, char, and gas) are reported.

Intensive exploration of the fuel characteristics of biomass and biochar from oil palm trunk and oil palm fronds for supporting increasing demand of solid biofuels in Thailand

This investigation explored the intensive characteristics of biomass and biochar from oil palm trunk (OPT) and oil palm fronds (OPF) for supporting the increasing demand of solid biofuels in Thailand. The characteristics of these samples were also compared to low grade sub-bituminous coal (LGSBC). The results indicate that converting OPT and OPF to biochar not only enhanced the fuel ratio and atomic ratios, but it also improved the energy content. The higher heating values (HHV) of OPT and OPF biochars were 26.92 and 28.05 MJ/kg. The fuel ratio, atomic ratio and HHV of biochars were better than those of LGSBC and biomass forms. Thermal decomposition and combustion characteristics of biomass and biochar from OPT and OPF were clearly different in N2 and air atmospheres. The biomass and biochar from OPT and OPF had high contents of alkali elements, consequently their ashes had high concentrations of some oxides like SiO2 and K2O. Biomass and biochar ashes from OPT and OPF had low initial deformation temperature (IDT). The IDT of OPT biochar ash was the lowest (907 °C), while the IDT of ash from LGSBC was above 1500 °C. The slagging and fouling indexes of biochars were clearly different from the LGSBC and biomass forms. Therefore, biomass and biochar from OPT and OPF have potential for solid biofuel use, and they are promising for further upgrading and applications. The user needs to be concerned with ash related problems like ash fusion, slagging, and fouling during combustion of these solid biofuels.

Morphology and Environmentally Persistent Free Radicals on Biochars: A Review

This paper examines the morphology and environmentally persistent free radicals on biochars. It is true that the increase in population has led to exponential increase in demand for energy leading to gradual depletion of fossil fuel reserves. Therefore arises the need to search for alternative renewable clean and sustainable energy resource. Biomass derived fuels offers the best alternative to fossil fuel. Pyrolysis is one of the techniques used to produce biofuel from biomass. Thermal decomposition of biomass in limited supply of oxygen leads to emissions of complex matrices that affect biofuel utilization and stability. The major by-products from biomass pyrolysis include liquid oil, biochar and gases depending on operating conditions such as temperature, particle size, heating rate and reactor configuration. Biochars generated tend to find its use majorly in industry, agriculture and cleaning of industrial waste. Nonetheless biochars may contain organic compounds such as furans, aldehydes, polyaromatic hydrocarbons (PAHS) and environmentally persistent free radicals which are of toxic, carcinogenic, cause oxidative stress and mutagenic. This review therefore focuses on the characteristics of biochar in terms of morphology and the nature of persistent free radicals embedded on the surface of the biochar. It is notable that the information on optimum conditions for production of biochars free of persistent free radicals is scanty if any.

Morphology and environmentally persistent free radicals on biochars: A review

This paper examines the morphology and environmentally persistent free radicals on biochars. It is true that the increase in population has led to exponential increase in demand for energy leading to gradual depletion of fossil fuel reserves. Therefore arises the need to search for alternative renewable clean and sustainable energy resource. Biomass derived fuels offers the best alternative to fossil fuel. Pyrolysis is one of the techniques used to produce biofuel from biomass. Thermal decomposition of biomass in limited supply of oxygen leads to emissions of complex matrices that affect biofuel utilization and stability. The major by-products from biomass pyrolysis include liquid oil, biochar and gases depending on operating conditions such as temperature, particle size, heating rate and reactor configuration. Biochars generated tend to find its use majorly in industry, agriculture and cleaning of industrial waste. Nonetheless biochars may contain organic compounds such as furans, aldehydes, polyaromatic hydrocarbons (PAHS) and environmentally persistent free radicals which are of toxic, carcinogenic, cause oxidative stress and mutagenic. This review therefore focuses on the characteristics of biochar in terms of morphology and the nature of persistent free radicals embedded on the surface of the biochar. It is notable that the information on optimum conditions for production of biochars free of persistent free radicals is scanty if any.

ارزیابی تأثیر بیوچار حاصل از دماهای مختلف پیرولیز بر رشد گیاه همیشه بهار تحت تنش شوری

ارزیابی تأثیر بیوچار حاصل از دماهای مختلف پیرولیز بر رشد گیاه همیشه بهار تحت تنش شوری

Green synthesis and characterization of Murraya koenigii leaf extract mediated IrO2, SnO2, and Ir-SnO2 nanoparticles

In the present work, green method of synthesis has been used to synthesize the IrO2, SnO2, and Ir-SnO2 mono and bimetallic oxide nanoparticles (NPs) using Murraya koenigii leaves extract. The synthesized particles are characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy, elemental mapping, transmission electron microscope (TEM), X-ray photoelectron spectroscopy and Fourier transform infrared spectra, thermal analysis (TGA, DTG, and DTA) techniques. The XRD patterns confirm that all samples have tetragonal crystal structure. The analysis of TGA data exhibits the weight loss of NPs (71.8% for IrO2, 73.6% SnO2, and 57.3% for Ir-SnO2) due to the thermal decomposition of biomass, and capping agent at the surface of NPs. The FE-SEM images demonstrate that the NPs of metal have different shapes like cube (IrO2), rods (SnO2), and intermixing of shape found in Ir-SnO2 sample (pseudo spherical and rod shaped). The approximate crystallite size of IrO2, SnO2, and Ir-SnO2 are ∼20, ∼5.23, and ∼1.23 nm, respectively, which are estimated from TEM images.

Energetic and thermal characteristics of Lavatera thuringiaca L. biomass of different age produced from He–Ne laser light stimulated seeds

The article presents the studies on the biomass yield, heating value and thermal decomposition process of the shoots of Lavatera thuringiaca L. plants (solid biofuel) of different age (one to three years old) grown from He–Ne laser stimulated seeds. Five combinations of Lavatera biomass characterized by different pre-sowing seed exposure times to laser light (1–30 min) were investigated. The results showed that the exposure time of, respectively, 10, 15 and 30 min had the most pronounced effect on the increase of biomass yield for two-year old shoots and the heating values for one-, two- and three-year old shoots biomass in relation to the control. Over the three experimental years, significant differences in the H, N, fixed carbon and ash content between the combinations of shoots were found. For the tested biomass after the exposition to laser light as well as for older plants, the ignition and burnout temperatures were shifted towards higher values. Stimulation with laser light affected the maximum mass loss rate as well as corresponding temperature for the investigated shoots. The two-year old combinations were characterized by better combustion index in comparison to one- and three-year old ones.As mentioned above, laser light stimulation of Lavatera seeds can contribute to the heating value and biomass yield increase and, as a result, to a more effective fossil fuel replacement.

A Numerical Model of Biomass Combustion Physical and Chemical Processes

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.

Physiochemical characterization of agricultural waste biochars for partial cement replacement

PurposeThe purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes.Design/methodology/approachBiochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests.FindingsAccelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement.Research limitations/implicationsWhile biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future.Practical implicationsCarbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs.Social implicationsReductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities.Originality/valueEmpirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.

Investigation of pyrolysis kinetics and gaseous compounds emitted during charcoal production from woods commonly used in the Eastern Mediterranean

AbstractAir pollution caused by the traditional charcoal production industry is an environmental problem for developing countries. Avocado (Persea americana) and Lemon (Citrus limon) trees that are commonly used in the charcoal industry in the Eastern Mediterranean were chosen as representatives of charcoal raw material in a wood pyrolysis kinetic study that was conducted using a thermogravimetric analyzer (TGA). The weight loss was measured in a nitrogen atmosphere with a heating rate of 10 °C.min−1 at a temperature range from 30 °C to 700 °C. Four main stages, denoted as dehydration, initial decomposition and both active and final decomposition, were registered in the wood thermal decomposition. The main gases produced were identified in the active decomposition stage for lemonwood and avocado wood, respectively, in the temperature range of 255 to 355 °C and 246 to 340 °C. The released gases in the biomass pyrolysis were measured on‐line using Fourier transform infrared (FTIR) spectroscopy. Main gas products of avocado and lemonwood pyrolysis were similar and included CO2, CO, H2O, CH4, and several organic compounds including methanol, formic acid, acetic acid, and furan. Charcoal production thermogravimetric analysis validated that the wood biomass thermal decomposition process has four stages: (1) water evaporation; (2) initial decomposition; (3) active decomposition, and (4) final decomposition. © 2021 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Coal/biomass co-combustion investigation by thermogravimetric analysis

In this study, the thermal characteristics and kinetic parameters of coal/biomass blended fuels (75:25, 50:50 and 25:75 wt.%/wt.%) were investigated by using the thermogravimetric technique under atmospheric air. Three types of agricultural waste biomass including cassava root, palm kernel shell and rice husk were used as raw materials. The experiments were performed under different temperatures, ranging from 313-973 K with the heating rate of 5, 10, 20 and 40 K/min. The results show that the thermal decomposition of biomass exhibit three-four stages including moisture and some light volatile removal stage (up to 463 K), volatile oxidation stage (423-663 K), char combustion stage (663-823 K) and inorganic oxidation stage (803-953 K). Lignite on the other hand exhibits only two main peaks during the entire combustion process, corresponding to the moisture removal (up to 433 K) and the decomposition/oxidation (433-833 K), respectively. In addition, it was also found that the blending of biomass residues improved the ignition temperature of the blended fuels, indicating an improvement of devolatilization of coal. Kinetic studies show that the average apparent activation energies of the co-combustion of coal/cassava root, coal/palm kernel shell and coal/rice husk calculated from the Kissinger-Akahira-Sunose method are reported at ca. 105.25, 179.66 and 121.84 kJ/mol, respectively.

Numerical estimation of the thermal stability boundaries for the process of thermochemical conversion processes of biomass in quasi-equilibrium approximation

The stationary process of pyrolysis and gasification of plant biomass in a wide range of conditions is considered. The reaction rate in a multicomponent system is a complex function of composition and temperature. To simplify the calculations, we use the approximation of the brutto-reaction: it is supposed that a slow reaction of thermal decomposition of biomass proceeds in the reaction zone with first order kinetics and Arrhenius dependence on temperature. Gas phase reactions rates are considered to be high enough to apply the quasi-equilibrium approximation. Calculations make it possible to estimate the temperature values at the boundary of thermal stability and the position of this boundary for different residence times of biofuel in the reaction zone.