Pyrolysis Rate Research Articles

Experimental and numerical study on pyrolysis characteristics of organic impurities in waste salt

The efficient removal of organic impurities in waste salts is significant for their recycling and environmental protection. The pyrolysis process of organic impurities in waste salt was investigated by thermogravimetric experiment to analyze the reaction kinetics characteristics. The results indicate that the pyrolysis reaction temperature range for the present waste salt is between 641.15 K and 726.22 K. The activation energy is 177.59 kJ mol−1, and the pre-exponential factor is 2.98 × 1011 s−1. Based on this, a numerical model was established to investigate the pyrolysis performance of organic impurities in practical tubular reactor. The effects of configuration and operating parameters on reaction performance and energy consumption were revealed. It was discovered that increasing the heating rate and wall temperature can accelerate pyrolysis rate but results in higher energy consumption. To balance reaction time and energy consumption, the heating rate of 15 K/min and heating temperature of 773.15 K are recommended. The content of organic impurities and bed porosity have minimal impact on the reaction rate and energy consumption, indicating that the tubular reactor has wide applicability in various working conditions. Additionally, reducing bed porosity can improve the processing rate and daily processing capacity. This paper provides a method to analyze the pyrolysis performance of organic impurities in waste salt, which is significant for designing and selecting working conditions of practical reactor for waste salt treatment.

Modulatory Role of Biochar Properties and Environmental Risk of Heavy Metals by Co-Pyrolysis of Fenton Sludge and Biochemical Sludge.

Recent studies have reported that Fenton sludge and biochemical sludge contain high concentrations of toxic substances and heavy metals (HMs), whereas improper treatment can pose serious threats to environmental safety. Pyrolysis is considered an efficient technology to replace conventional sludge treatment. This study investigated the pyrolysis and kinetic processes of Fenton sludge and biochemical sludge, revealed the physicochemical properties of sludge biochar, and highlighted the role of co-pyrolysis in sludge immobilization of HMs and environmental risks. Results showed that Fenton sludge and biochemical sludge underwent three stages of weight loss during individual pyrolysis and co-pyrolysis, especially co-pyrolysis, which increased the rate of sludge pyrolysis and reduced the decomposition temperature. The kinetic reaction indicated that the activation energies of Fenton sludge, biochemical sludge, and mixed sludge were 11.59 kJ/mol, 8.50 kJ/mol, and 7.11 kJ/mol, respectively. Notably, co-pyrolysis reduced the activation energy of reactions and changed the specific surface area and functional group properties of the biochar produced from sludge. Meanwhile, co-pyrolysis effectively immobilized Cu, Pb, and Zn, increased the proportion of metals in oxidizable and residual states, and mitigated the environmental risks of HMs in sludge. This study provided new insights into the co-pyrolysis properties of sludge biochar and the risk assessment of HMs.

МОДЕЛИРОВАНИЕ КИНЕТИКИ ПРОЦЕССА ПИРОЛИЗА БИОМАССЫ С УЧЕТОМ ВЛИЯНИЯ СОСТАВА СЫРЬЯ В ТРУБЧАТЫХ РЕАКТОРАХ

The pyrolysis process of plant biomass can be better understood by investigating the kinetic mechanism of the decomposition process of various components. Biomass can have different structures, thermophysical properties and chemical composition, which affects the kinetics of the pyrolysis process. (Research purpose) The research purpose is simulating and studying the kinetics of the pyrolysis process of corn cob particles, which allows to determine the rate of chemical reactions occurring during the decomposition of the material, and identifying the main factors affecting the rate and efficiency of pyrolysis. (Materials and methods) The biomass of corn cobs, which has a particle size of 0.02 square meters and has thermophysical properties, was used for analysis using Comsol multiphysics software. (Results and discussion) We have obtained models that describe temperature trends, especially the temperature in the center of biomass. It was shown that the temperature on the surface of the biomass reaches a peak of 727 Kelvin after 460 seconds; the temperature in the center of the biomass reaches 794 Kelvin after 433 seconds. It was shown that the activation energy and frequency coefficient are derived from the slope of the linear regression line and the intersection. (Conclusions) It was found that the process of pyrolysis of biomass of a corn cob particle occurred in the temperature range of 190-432 degrees Celsius; at a temperature of 190 degrees Celsius, the biomass began to lose mass, and the mass loss stopped at a temperature of 432 degrees Celsius. The kinetic parameters were calculated by the Kissinger method. The least squares method and correlation analysis were used to calculate kinetically constant parameters. It was stated that the results will be useful to optimize the process of pyrolysis of biomass. It was determined that in the Kissinger method the kinetic parameters were the same for the entire pyrolysis process; the correlation coefficient between temperature and heating rate in the model is 0.79.

Cellulose pyrolysis kinetic model: Detailed description of volatile species

Lignocellulosic biomass is typically composed by a major fraction of cellulose. Its decomposition influences on large extent the biomass rate of pyrolysis and product distribution, affecting process behaviour in thermochemical conversion processes. Containing approximately 90 % of volatile matter, volatile products from cellulose pyrolysis are very important in the characteristics of flames and ignition properties. Recent developments in analytical methods allowed a detailed identification of these volatile products, giving valuable information to process development and better understanding of kinetics. Predictions of a previous kinetic model are compared with these new findings, revealing large space for improvements. In this work, we propose a multi-step kinetic model of cellulose pyrolysis, incorporating the most recent experimental findings into the detailed product description. The model consists of four main reactions for the decomposition of cellulose, with formation of gases, volatiles, char and metaplastic species. The release of metaplastic species is described by a set of six reactions. The formation and release of 13 oxygenated hydrocarbons is predicted by the model, including anhydrosugars, furans, aldehydes, alcohols, ketones and carboxylic acids. The model also describes the formation of levoglucosan in metaplastic state before its release, explaining high heating rate mass loss behaviour. The model is compared with a large variety of experiments from literature, and validated for mass loss rates and product distribution, achieving overall good agreement despite experimental uncertainties and the large simplifications characteristic of the model formulation. Besides effectively quantifying the yields of gaseous, condensable and solid products, the model accurately captures the distribution of volatiles in terms of functional groups and C-chain length.

Far-field signature of fire in low gravity: Influence of ambient oxygen content and pressure on size distribution of smoke particles

Fire detection in space habitats is hindered by the unique characteristics of smoke particles released by weakly buoyant flames. For the first time, non-invasive measurements of particle concentration, size, and light absorption properties are performed in the downstream flow of a flame spreading in microgravity. The studied flame spreads over Low Density PolyEthylene (LDPE) coated Nickel/Chrome (NiCr) wires in an opposed oxidizer flow. The far-field signature can then be contrasted with previous measurements performed over the same configurations and related to the morphology of soot particles sampled in and behind the flame.Following measurements regarding the impact of gravity, the influence of ambient pressure and oxygen content on the characteristics of the particles is reported in microgravity. Increased pressure boosts the soot production rate, leading to higher concentration levels of particles detected for any class of particle size. Higher pressure also causes larger aggregates that exhibit a higher level of polydispersity among the constituting primary particles. This tends to enhance light absorption, more specifically at larger particle size. Less intuitively, increased oxygen content accelerates the pyrolysis rate, therefore hastening soot particles’ maturity, and ultimately increasing the detected soot concentration. In addition, enhanced oxygen content reduces organic carbon within particles, boosting light absorption regardless of the particle size. The far-field signature and its sensitivity to the ambient conditions are in decent agreement with observations of soot particles collected at the trailing edge of the flame. As a result, combining higher oxygen content and lower pressure in future space habitats as projected by the main space agencies can cancel out the effect on the detection threshold of a given flame if this threshold only includes the concentration level.

Preparation of ceramifiable and ablatively resistant epoxy resins by microphase structure modulation of silicones

The development of ceramic-polymer composites is a focal point in the research of thermal protection systems, and the control of microstructure is crucial for fabricating high-performance resins. In order to investigate the effect of the silicon phase structure on the properties of epoxy resins and preparate the ablation-resistant ceramifiable resins, the homogeneous and “sea-island” phases of epoxy resins with different amounts of silicones were prepared by ring-opening and grafting reactions. The reaction mechanism and the microphase structure of silicone were verified by SEM and TEM. It was found that the homogeneous silicone-epoxy resins exhibited exceptional ablation resistance, with mass and linear ablation rates of 0.0646 g/s and 0.0073 mm/s, which were 78.61 % and 98.36 % lower than those of epoxy resins, and exceeded most of the resin-based ablation-resistant materials reported in the literatures. The homogeneous silicone further slows down the pyrolysis rate of the epoxy resin and inhibits the release of pyrolysis products. During the carbonization and ceramization, the carbothermal reduction reaction between silicon and carbon occurs sufficiently in the homogeneous system, which enhanced the content of SiC ceramics in the carbon layer. Eventually, a dense char layer with low porosity and a highly graphitized structure constructed in situ on the ablative surface, which greatly improves the ablative resistance. Furthermore, its exceptional mechanical properties render it capable of substituting conventional resin-based thermal protection materials, thereby meeting the stringent demands of challenging environments.

Effect of simultaneous H2 and NH3 addition on soot formation in co-flow diffusion CH4 flame

Simultaneous blending of hydrogen (H2) and ammonia (NH3) to hydrocarbon fuels can tackle the safety issues of H2 and improve burning efficiency of NH3. While this strategy brings challenges for soot prediction due to the promotion effect of H2 and the suppression effect of NH3, and the interactions between H2 and NH3. In this study, the simultaneous addition of NH3 and H2 on soot formation was experimentally and numerically investigated in a co-flow diffusion CH4 flame. The interactions between NH3 and H2, and how they impacted different soot formation processes were comprehensively revealed using a detailed soot sectional model. The decrease of peak SVF in CH4 flame caused by NH3 was 0.013 ppm, about 31.6 % smaller than that in CH4/H2 flame (0.019 ppm), indicating that the inhibitive effect of NH3 on soot formation was promoted by H2. The existence of H2 promoted the suppression effect of NH3 on soot nucleation, condensation and HACA processes in the CH4 flame. Compared with CH4/NH3 flame, the pyrolysis rates of NH3, NH2 and NH in the CH4/NH3/H2 flame were higher since more H and OH radicals were generated via H2 decomposition. This led to a larger consumption rate of H and OH radicals, which decreased the reaction rates of CH4+OH=CH3+H2O and C2H4+OH=C2H3+H2O, and promoted the combination of NO and C2H. Both factors accounted for a stronger suppression effect of NH3 on the formation of A1 in CH4/H2 flame than that in CH4 flame, and thus a stronger inhibitive effect on soot inception and condensation. Compared with the CH4 flame, NH3 resulted in a larger decline of H and OH radicals mole fractions in the CH4/H2 flame, which explained the stronger suppression effect of NH3 on the HACA surface growth process in the CH4/H2 flame.

New insights into brominated epoxy resin type WPCBs pyrolysis mechanisms: Integrated experimental and DFT simulation studies

Pyrolysis is a recycling technology for waste circuit boards (WPCBs) with a wide range of applications. In this research, the brominated epoxy resin (BER) type WPCBs were taken as the research object, and the optimal pyrolysis process parameters were determined. Combined with experiments and density functional theory (DFT) calculations, the pyrolysis gaseous generation pattern and product distribution of BER type WPCBs were analyzed, and the generation mechanism of phenol, bromide and other pyrolysis products was investigated in depth. The results of the study showed that the pyrolysis rate of WPCBs exceeded 95 % under optimal reaction conditions. In the initial phase of the pyrolysis of WPCBs, the BER's CO bonds and a portion of Ph-Br bonds will be broken, leading to the production of intermediates such propylene oxide, bisphenol A, isopropyl alcohol, tetrabromobisphenol A and HBr. Among them, propylene oxide can generate ethylene oxide through free radical reaction. In the second stage, intermediates such as bisphenol A undergo homolytic cleavage and radical addition to form phenols, bromides, alcohols, ketones and other pyrolysis products.

Measurements of the local equivalence ratio and its impact on the thermochemical state in laminar partially premixed boundary layer flames

Local fuel–air equivalence ratios, gas phase temperature and CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {CO}_2$$\\end{document} mole fractions were measured by a combination of laser-induced fluorescence of nitric oxide used as a tracer and dual-pump coherent anti-Stokes Raman spectroscopy in a vertically oriented partially premixed boundary layer flame under laminar flow conditions. By embedding a secondary effusive fuel inlet into the temperature-controlled wall of a sidewall-quenching configuration, different pyrolysis rates of a wall-embedded polymer are mimicked with reduced chemical complexity and well-controlled boundary conditions. The resulting boundary layer flames were investigated experimentally and numerically. The simulation results and measurements show a very good agreement on the complex interplay between local mixing and heat losses, even though inhomogeneities of the wall inlet complicate the comparison of data. Local equivalence ratios upstream of the reaction zone reach values of up to Φ=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varPhi = 2$$\\end{document}. Under these conditions, a clear quenching location could not be identified based on the experimental data. A significant trend toward lower temperatures and CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {CO}_2$$\\end{document} mole fractions with increasing amount of secondary fuel was found in the thermochemical state close to the temperature-controlled wall, downstream of the effusive inlet.Graphical abstract

Study on the suppression characteristics and mechanism of ABC powder on pulverized coal explosion based on the analysis of thermal decomposition characteristics and reaction kinetics

This study investigates the inhibitory characteristics and mechanisms of ABC powder on coal powder explosion using a combination of experimental, theoretical, and numerical methods. In a 20 L spherical explosion experimental system, coal powder was mixed with ABC powder at various mass concentrations. The microstructure and major functional groups of the explosion products were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The proportions of the major functional groups were determined through peak fitting analysis. The research findings demonstrate that the introduction of 60 wt% ABC powder into the coal sample led to a significant decrease in the maximum explosion pressure, from 0.683 MPa to 0.454 MPa, indicating a remarkable reduction of 33.38%. Moreover, the inclusion of 70 wt% ABC powder exhibited complete suppression of coal dust explosions. Thermal decomposition characteristics of the mixed system were investigated using a thermogravimetric analyzer, and the Coats-Redfern integral method was employed to analyze the pyrolysis experimental data. The results suggest that the optimal reaction kinetics models for the combustion stage of coal powder and the mixed system are F1 and F2, respectively. Adding ABC powder increases the activation energy by 27.35% and slows down the pyrolysis rate by 37.97%. Furthermore, numerical simulations using CHEMKIN software were conducted to study the inhibitory effect of ABC powder on coal powder explosion. The results demonstrate that the addition of ABC powder significantly reduces the content of O·, H·, and OH·radicals, which are responsible for sustaining explosive chain reactions within the explosion system. By incorporating the findings of this investigation, the present study offers a comprehensive explication of the intricate micro-level mechanisms that underlie the inhibitory properties exerted by ABC powder on coal dust explosions. These results contribute novel scientific and theoretical foundations, yielding profound insights into the prevention and mitigation of calamitous coal dust explosion incidents within coal mining environments.

Improving the transient thermal response and ablation properties of epoxy‐modified silicone rubber composites by adding fluxing agent

AbstractIn this work, transient thermal response and ablation behavior of liquid silicone rubber composites containing fluxing/ceramic forming fillers were investigated under different heat flows using an oxyacetylene flame. The results indicated that the introduction of zinc borate (ZB) and aluminum oxide (Al2O3) effectively reduced the temperature at various depths of the samples, and they improved the thermal insulation properties and lowered pyrolysis rates. The above finding was attributed to the heat absorption arising from water release and melt filling as well as the vitrified reaction of solid melt due to the decomposition of ZB. Besides, the melting and exfoliation of Al2O3 and the formation of aluminum silicate (Al2SiO5) caused heat absorption effect. Additionally, the mass ablation rates and line ablation rates increased with rising heat flows coupling with a decrease of compressive strength of the char layers. In a nutshell, the effect of adding ZB/Al2O3 on the thermal insulation behavior of epoxy‐modified vinyl silicone rubber (EMVSR) composites under different heat flows was elucidtaed. This work served as a reference for the design and preparation of flexible ablative materials for thermal protection applications.

A study on the pyrolysis of n-hexane initiated by 1-nitropropane: Molecular dynamics simulations and SVUV-PIMS experiments

To investigate the influence of 1-nitropropane (1-NP) initiator on the pyrolysis of n-hexane (n-C6H14), molecular dynamics (MD) simulations and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) experiments were used to analyze the pyrolysis processes of n-C6H14 and n-C6H14 with 10 % 1-NP added. ReaxFF MD simulations were used to analyze the pyrolysis rates and product distributions of n-C6H14 and 1-NP/n-C6H14 at different temperatures. The mechanism of action of n-C6H14 pyrolysis initiated by 1-NP was investigated. Additionally, the pyrolysis products of n-C6H14 and 1-NP/n-C6H14 were identified and quantitatively analyzed using the SVUV-PIMS technique. These experimental results were compared with the ReaxFF MD simulation results to validate the reliability of the simulations and to complement each other. The results indicate that the presence of 1-NP promotes the pyrolysis of n-C6H14 and significantly improves the chemical heat sink of the fuel. The chemical heat sink in the 1-NP/n-C6H14 system differs from that in the n-C6H14 system by 28.78 kJ/kg at 2103 K. A significant increase in C2H4 production in the pyrolysis products of n-C6H14 with the addition of 1-NP. The pyrolysis of 1-NP/n-C6H14 yielded approximately twice as much C2H4 as n-C6H14 at 2103 K. The pyrolysis reactions were described by first-order kinetics, and the activation energy for the pyrolysis of 1-NP/n-C6H14 was determined to be 140 kJ/mol, approximately 48 % lower than that of n-C6H14. The composition of the pyrolysis products was confirmed by SVUV-PIMS experiments, which were in good agreement with the ReaxFF MD simulations. The mechanism of pyrolysis of n-C6H14 initiated by 1-NP was elucidated: the NO2 radicals generated by 1-NP react with H radicals of the system to form OH radicals. The primary reaction of n-C6H14 involves the abstraction of H by OH, leading to the formation of C6H13. Subsequently, C6H13 is further decomposed to form 1-C3H7, 1-C4H8, 1-C5H10 and 2-C6H12.

Study on Pyrolysis Behaviors and Characteristics, Thermodynamics, Kinetics, and Volatiles of Single-Base Propellant, a Typical Energy-Containing Material

The widespread use of single-base propellant may contribute to serious pollution of the environment. The study of single-base propellant pyrolysis could provide an in-depth understanding of the combustion mechanism, reveal the key steps and reaction kinetics of the combustion process, and reduce the damage when using single-base propellant to the environment. In the present study, the pyrolysis behaviors, pyrolysis characteristic parameters, kinetics, thermodynamics, and volatiles of single-base propellant pyrolysis in an argon atmosphere were studied. The results showed that the main temperature ranges of pyrolysis and heat variation were 400–700 K and 450–520 K, respectively. With the increase in the heating rate, the maximum/average reaction rate of pyrolysis increased, the maximum instantaneous heat flow and the heat flow integral increased, the pyrolysis and combustion performance increased, and the thermal stability decreased. The average global activation energy and pre-exponential factor of the pyrolysis were 202.82 kJ and 9.48 × 1021, respectively. Thermodynamic analysis showed that the single-base propellant pyrolysis was a spontaneous endothermic reaction with a low energy barrier and fast reaction rate, which was beneficial to the formation of active complexes. In addition, information on the main volatiles was obtained, including H2, CH4, C2H4, C2H6, H2O, HCN, HCOOH, NO2, HONO, and CO2.

An engineering model for the pyrolysis of materials

Accurately representing the time dependent heat release rate of fuels is critical to performance-based design in fire safety applications. Existing simplified models either use average pyrolysis rates at different heat fluxes or do not account for the change in burning behavior at higher heat transfer rates. This paper presents the theoretical basis of a scaling-based pyrolysis model, S-Pyro. The model is based on the concept of maintaining the shape of a reference heat release rate per unit area curve but scaling the magnitude and time based on a dynamic thermal exposure. The model has been implemented in the computational fluid dynamics software Fire Dynamics Simulator (FDS). The model is validated with solid-phase only and multi-phase simulations of cone calorimeter experiments. The solid-phase simulations evaluated the capability of the model to predict the heat release rate per unit area of 149 materials tested at heat fluxes other than the reference flux. Multi-phase simulations of bench-scale fire experiments with a single material, Canada Pine and Spruce plywood, were used to evaluate the performance of the pyrolysis model in FDS. The model uncertainty was lower for high heat release rate materials, with the model uncertainty approaching the experimental uncertainty at higher burning rates.

Comparative pyrolysis characteristics and kinetics of agricultural food grains by thermogravimetric analysis

Pyrolysis precedes the development of smouldering or flaming fires in storage and processing facilities. Understanding this process and determining the parameters that characterise it is essential for controlling fires. This study analysed the pyrolysis of African food grains that are important for food security but historically have received limited attention. Cowpeas, lentils, millet, soybeans, unshelled peanuts, flax, sunflowers, shelled peanuts, and sesame were subjected to thermogravimetry in a nitrogen atmosphere at heating rates of 5, 10, 20, and 40 °C/min from ambient to 600 °C. All grains were completely dehydrated at 170 °C and started decomposing at about 180 °C. The decomposition patterns varied with the relative proportion of hemicellulose, cellulose, protein and, particularly, lipids (oil content). Pyrolysis rates peaked at lower temperatures of about 300 °C for non-oil grains but at higher temperatures of 400 °C for oil grains. Friedman and Coats-Redfern methods were used to determine activation energies (130–355 kJ/mol), preexponential factors (8.1 × 107–1.0 × 1031 s−1) and the numerical values of the complex, multistep reaction models. Oil grains (or their powder) generally have lower activation energies, are thus more reactive than non-oil grains, and therefore constitute critical consideration for fire safety in processing facilities. The work is important for developing fire engineering solutions for food facilities based on quantitative fire behaviour data.

Effects of pressure and heating rate on coal pyrolysis: A study in simulated underground coal gasification

Underground coal gasification (UCG) is a promising technology which in-situ converts coal into fuel gases through controlled chemical reactions. In order to precisely control coal pyrolysis and increase the char yield, it is vital to understand the influences of operating factors such as heating rate and pressure, on coal pyrolysis. In this study, the effects of heating rate and pressure on the char formation of bituminous coal pyrolysis are investigated. The reaction mechanism of coal pyrolysis and the solid-state kinetic model are firstly reviewed. Subsequently, thermal experiments are conducted to study the effects of heating rate and pressure on coal pyrolysis characteristics. Moreover, the connection between the dominant coal pyrolysis reaction type and corresponding solid-state kinetic model is revealed. An empirical model of coal pyrolysis rate, pressure, and heating rate is also developed, which can be used to quantitatively predict pyrolysis rates under varying heating rate and pressure conditions. The results show that the optimal heating rate for char generation is at around 10 °C/min. On the other hand, when the pressure exceeds 2 MPa, it will enhance the char production by obstructing the physical release of volatiles and has insignificant impact on the reaction type. This study contributes to our understanding of the coal pyrolysis mechanism, and the proposed empirical model can provide valuable insights for optimizing operating parameters during UCG process.

Valorization of royal palm tree agroindustrial waste via pyrolysis with a focus on physicochemical properties, kinetic triplet, thermodynamic parameters, and volatile products

This work reports experimental findings for pyrolysis of the royal palm tree (RPT) waste, particularly emphasizing the kinetic triplet, thermodynamic parameters, and characterization of volatile products. Pyrolysis experiments were conducted in a thermogravimetric analyzer and an analytical pyrolyzer coupled with a gas chromatography-mass spectrometry (Py–GC/MS). First, pyrolysis of RPT waste was considered to proceed in four independent devolatilization reactions linked to extractives, hemicellulose, cellulose, and lignin. The fractional contributions for these pseudo-components were determined as follows: 0.0600 for extractives, 0.3140 for hemicellulose, 0.2667 for cellulose, and 0.3196 for lignin. The following standard procedure for determining the kinetic triplet was adopted: four isoconversional methods (Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Starink), Kissinger's method, and integral master plots. The mean overall activation energy and the pre-exponential factor for the four independent devolatilization reactions are 78.3 kJ mol−1 and 9.5 × 107 min−1, 107.2 kJ mol−1 and 5.7 × 109 min−1, 130.6 kJ mol−1 and 7.0 × 1010 min−1, and 153.6 kJ mol−1 and 1.2 × 1013 min−1, respectively. The most suitable reaction models for the pyrolysis of RPT waste belong to the nucleation-growth and n-order reaction mechanisms. The resulting values of the thermodynamic parameters ΔH, ΔG, and ΔS were respectively within 71.8–144.3 kJ mol−1, 138.0–173.2 kJ mol−1, and −138.4–(−43.7) J mol−1 K−1. Numerical simulations were performed to verify the kinetic triplets' results in one overall pyrolysis rate expression. The simulated and experimental kinetic curves exhibited a strong agreement, indicating a high level of consistency between them. The findings from this work suggest the suitability of royal palm waste as a promising raw material for producing bioenergy and renewable chemicals, in addition to being valuable for designing large-scale pyrolyzers for this type of waste.

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.

Nanoscale MOF-catalyzed pyrolysis of oil shale and kinetic analysis

Oil shale is of increasing interest as it is considered an essential alternative to traditional energy sources due to its abundant reserves. In this research, nanoscale Co/MOF and Ni/MOF were prepared by modified methods, and the catalytic pyrolysis mechanism of oil shale was studied using structural characterization and pyrolysis experiments. The TG and DTG curves show that MOF catalysts increase the total weight loss rate of oil shale pyrolysis and decrease the temperature corresponding to the initial temperature, final temperature, and maximum weight loss rate of oil shale pyrolysis. Kinetic analysis shows that Co/MOF and Ni/MOF catalysts reduce the activation energy of oil shale pyrolysis reaction by 32 KJ/mol and 25 KJ/mol, respectively. The change in the yield and composition of the products before and after catalytic pyrolysis was compared through the dry distillation experiment. It was found that MOF had a good catalytic effect, and the shale oil output was significantly increased. The FT-IR and GC/MS analysis of the catalytic pyrolysis of shale oil shows that the addition of Co/MOF and Ni/MOF catalysts is conducive to the increase of aromatics, olefins, and alkanes and the decrease of oxygen-containing compounds. The effect of the catalysts on the nature of the products and on the yields suggests that the Lewis and Bronsted acid groups on the surfaces of the MOF catalysts and that these can induce positive charges on carbon atoms in alkanes, alkenes etc to promote pyrolysis generate more oil.

Spatially Directed Pyrolysis via Thermally Morphing Surface Adducts

AbstractCombustion is often difficult to spatially direct or tune associated kinetics—hence a run‐away reaction. Coupling pyrolytic chemical transformation to mass transport and reaction rates (Damköhler number), however, we spatially directed ignition with concomitant switch from combustion to pyrolysis (low oxidant). A ‘surface‐then‐core’ order in ignition, with concomitant change in burning rate,is therefore established. Herein, alkysilanes grafted onto cellulose fibers are pyrolyzed into non‐flammable SiO2 terminating surface ignition propagation, hence stalling flame propagating. Sustaining high temperatures, however, triggers ignition in the bulk of the fibers but under restricted gas flow (oxidant and/or waste) hence significantly low rate of ignition propagation and pyrolysis compared to open flame (Liñán's equation). This leads to inside‐out thermal degradation and, with felicitous choice of conditions, formation of graphitic tubes. Given the temperature dependence, imbibing fibers with an exothermically oxidizing synthon (MnCl2) or a heat sink (KCl) abets or inhibits pyrolysis leading to tuneable wall thickness. We apply this approach to create magnetic, paramagnetic, or oxide containing carbon fibers. Given the surface sensitivity, we illustrate fabrication of nm‐ and μm‐diameter tubes from appropriately sized fibers.