Kinetic Parameters Of Thermal Degradation Research Articles

Determination of the Kinetic Parameters of Thermal Degradation and Hydrodemetallization of a Mixture of the Heavy Fraction of Low-Temperature Coal Tar and Coal Shale

The laws of thermal degradation of the mixture of the heavy fraction of low-temperature coal tar and coal shale were investigated using dynamic thermogravimetry. The kinetic characteristics of the process were determined using various methods, including the Ozawa–Flynn-Wall, Friedman, non-parametric kinetics and Šesták–Berggren methods. It is shown that coal shale initiated changes in the kinetic parameters and decomposition rate of the heavy fraction of coal tar. It was found that a 13% content of coal shale in the mixture led to the maximum rate of weight loss of the heavy fraction of coal tar. A hydrodemetallization kinetic model of the mixture of the heavy fraction of low-temperature coal tar and coal shale is proposed. The kinetic parameters of the hydrodemetallization process were determined; in addition, the rate constants at various temperatures were estimated. The study shows that the distribution of trace elements in the hydrogenate from the initial mixture and in the hydrogenate from the solid residue was characterized by relatively low values of reaction rate constants. The maximum microelement distribution rate was achieved in the hydrogenate solid residue. Energy indicators of activation processes indicated that hydrodemetallization at low temperatures is advantageous from an energy point of view.

Effect of different pre-treatment techniques on thermogravimetric characteristics and kinetics of lignocellulosic biomass pyrolysis

In this study, effect of pre-treatments on biomass pyrolysis kinetics was evaluated. Fir wood sawdust (F), pine wood sawdust (P) and hazelnut shell (H) were selected as raw biomass sample. Acidic pre-treatment was applied by using 1M-H2SO4 at room conditions and hydrothermal pre-treatment applied by using high pressure and temperature reactor. Thermogravimetric analysis was executed to specify thermal degradation behavior of the samples. Thermogravimetric analysis was also used to determine kinetic parameters of thermal degradation for biomass and pre-treated biomass samples. Having knowledge thermal degradation behavior and kinetic parameters of pyrolysis process such as activation energy and reaction rate are very important for reactor design. Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW) and Coats-Redfern (CR) methods were used to investigate the effect of different pre-treatment techniques on the kinetic parameters. Activation energies of pyrolysis reactions for F, P and H were found as 158.47 ± 1.08 kJ/mol, 126.0 ± 1.78 kJ/mol and 158.66 ± 1.24 kJ/mol, respectively. The calculated activation energy values increased while acidic and hydrothermal pre-treatment were applied to each biomass samples. In conclusion, acidic and hydrothermal pre-treatments influenced the serial and parallel reaction rates during the thermal degradation process and the calculated activation energy values changed accordingly. Inorganics that catalyzed the pyrolysis reactions were removed by acid pre-treatment. The condensed species during hydrothermal pre-treatment prevented the easy volatilization. As a result of experimental studies and kinetic calculations, it has been determined that pre-treatments applied to biomass increased the activation energy value in thermal degradation reactions.

Pyrolysis of Pine Wood in the Presence of Boron-Nitrogen Compounds.

The actuality of this research is determined by the intensification of new ways of processing woody biomass. This requires revealing the impact of various physicochemical factors on the thermal degradation of wood biopolymers. Boron-nitrogen surface modifiers are used for wood antisepsis and we decided to check their effect on flammability. The aim of the research was to evaluate the flame retardant effect of boron-nitrogen surface modifiers of wood in an inert atmosphere (nitrogen was used). The evaluation was carried out by thermal analysis of modified and the control pine wood samples. The thermal analysis included thermogravimetry, differential scanning calorimetry and kinetic parameters of thermal degradation. It was found that the flame retardant effect of boron-nitrogen wood surface modifiers was not significantly pronounced in the nitrogen atmosphere. The mechanism of the flame retardant effect of boron-nitrogen compounds is reduced to "shielding" of the surface and increasing the proportion of carbonized residue. On the basis of correlation-regression analysis of kinetic parameters of wood thermodestruction in a nitrogen atmosphere, mathematical models of activation energy dependence on conversion were obtained and substantiated. The developed models can be further applied to calculate the predicted value of wood activation energy in the nitrogen atmosphere at any conversion value.

Thermal conversion performance, kinetic mechanism, and products of electric vehicle lithium battery diaphragms

The proliferation of waste lithium batteries is on the rise; however, the thermal treatment attributes of these batteries are largely overlooked, and the conversion mechanism of lithium battery separators remains unclear. This study marks the first comprehensive to compare the thermal degradation characteristics, kinetic parameters and mechanisms, thermal degradation products, and degradation pathways of polypropylene (PP) and polyethylene (PE) lithium battery diaphragms. The pyrolysis temperatures for the PP and PE were 340–500 and 440–530 °C, respectively. PP and PE exhibited average activation energies of 65.19–73.04 and 207.62–209.40 kJ/mol, respectively. At 600–800 °C, the yields of PP and PE pyrolysis gases and gasoline products increased with increasing temperature, while the yields of diesel and paraffin products decreased. The most dominant products generated from the pyrolysis of PP and PE were olefins, and the amount of olefin products from PE increased with increasing pyrolysis temperature. CH3 fracture was the first reaction step that occurred during PP pyrolysis. Our study provides useful information for industrial recycling, disposal, and utilization of electric vehicle lithium battery separators as well as data on the pyrolysis behaviours and transformation mechanisms of polyolefin wastes.

Unlocking energy potential: Investigating thermal degradation and kinetic modeling of health‐care waste polymers for enhanced pyrolysis conversion

AbstractRecently, the main polymers present in the health‐care waste (HCW) of a Brazilian university hospital were identified, revealing a composition of polypropylene (85%), high‐density polyethylene (6%), polystyrene (5%), and cellulose (4%). Recognizing the potential for these materials to generate energy through pyrolysis, this study aimed to assess the thermal degradation of the HCW polymers and their respective polymer mixture using thermogravimetric analysis. Thermalgravimetric analysis encompassed three heating rates (5, 10, and 20°C min−1). The kinetic parameters of thermal degradation were estimated using the first‐order reaction model. Friedman differential isoconversional method, as well as Ozawa, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose integral isoconversional methods, were applied to obtain the kinetic parameters, which can predict the thermal degradation kinetics of the polymers in thermal conversion process. Through statistical evaluation of the parameter estimation, it was demonstrated that the proposed methodology yielded fitted models for the experimental data on HCW. These models may be implemented in designing pyrolysis reactors that convert these polymers into energy, thereby mitigating environmental pollution.

Improved thermal stability of roselle anthocyanin by co-pigmented with oxalic acid: Preparation, characterization and enhancement mechanism

The enhancement effects of co-pigmentation on thermal stability of roselle anthocyanin extract (RAE) were investigated. The introduction of organic acids maintained color stability of RAE, and RAE co-pigmented with oxalic acid (OA) presented less color fading rates (19.46 ± 0.33 %) and higher redness (41.33 ± 3.51). Subsequently, suitable co-pigmentation concentration (OA:RAE = 1:2) was obtained regarding with lower ΔE (48.70 ± 2.36). Then, improvement behaviors of co-pigmentation on OA-RAE were evaluated. Results demonstrated that OA-RAE exhibited better thermal stability, as manifested by larger retention rates and more favorable thermal degradation kinetic parameters. Furthermore, both molecular docking simulation and experimental structural characterization revealed that hydrogen bonds and other non-covalent bonds made up the main parts of molecular interactions, leading to formation of stable binary complex. As a result, the aromatic ring of RAE was protected. In conclusion, the co-pigmentation of RAE via introduction of OA was effective in stability enhancement due to the generation of molecular bindings.

Thermal decomposition characterization and kinetic parameters estimation for date palm wastes and their blends using TGA

TGA has been used to evaluate the thermal degradation profiles and kinetic parameters for the pyrolysis of date leaves, date seeds, and leaf stems and their blend at various heating rates (β) in N2. Using Kissinger–Akahira–Sunose (KAS), and Ozawa-Flynn-Wall (OFW), kinetic parameters like activation energy (E) and frequency factor (A) were estimated. The diffusion, reaction order, and power law models were used to estimate the frequency factors based on the (E) values obtained from the OFW and KAS approaches. Thermal degradation profiles showed two major loss processes: volatilization of cellulose, hemicelluloses, and lignin; and slow oxidation of the residual char. The findings demonstrated that as β increased, the TG profiles shifted to higher temperature ranges. The date palm's decomposition was not favourably reflected by the high (ΔGav) values obtained. The high (ΔSav) values obtained using OFW compared to KAS confirm these materials' high reactivity. The average activation energies (Eav) for the different parts of the date palm wastes ranged between 86 and 117 kJ/mole as predicted by the KAS method, while they were between 92 and 120 kJ/mole using the OFW method. The calculated frequency factor (A) values, evaluated by the KAS and the OFW methods, ranged between 0.0 and ∼ 0.8 × 1019min-1. The difference in (Eav) values between the KAS and OFW techniques is no greater than 8 kJ/mole. For the diffusion models of DSW, DL, and Blend, the best frequency distribution profiles are essentially normal, and the blend exhibits high frequency (A) values in a relatively constrained range of (α). That denotes quick and efficient pyrolysis. The pyrolysis index (CPI) significantly increased as β increased, indicating that pyrolysis was profitable at high heating rates. The volatile release index (Ddev) increases significantly with increasing (β) value, showing that volatiles was easier to release at a high heating rate.

Methanolysis of fresh and used soybean oil to biodiesel under mild conditions: Process optimization, fuel quality characterization and thermal stability studies

Methanol is a basic monohydric alcohol often used in excess for the biodiesel synthesis via catalyzed transesterification process because it is relatively cheap, readily available and facilitates easy separation of glycerol from product mixture. Herein, biodiesel was synthesized from fresh and used soybean oil (FSO and USO) via low temperature methanolysis process. Taguchi design method was used to optimize the biodiesel production process, and thermogravimetric analysis (TGA) of biodiesel was conducted at a heating rate of 20 °C/min in the temperature range of 30 to 900 °C. Thermal degradation kinetic and thermodynamic parameters were estimated based on TGA data using Coats-Redfern (CR) model. According to Taguchi design, reaction temperature was found to be the most influential variable, followed by methanol/oil molar ratio. At the optimum conditions of 30 °C reaction temperature, 30 min reaction time, 12:1 methanol/oil molar ratio and 1.0 wt% KOH concentration, the FAME contents in FSO-biodiesel (FSO-B) and USO-biodiesel (USO-B) were 99.3% and 97.09%, respectively, which conformed to European Standard EN 14214. The TGA data fitted well to the CR model with average activation energies of 47.59 kJ·mol−1 and 35.78 kJ·mol−1 for FSO-B and USO-B, respectively. Thermodynamic parameters such as enthalpy change, Gibbs free energy change and entropy change were all estimated for both biodiesel samples.

Thermal Aspects of Kumada Rearrangement in Symmetrical and Asymmetrical Polysilanes-Interdependence of Molecular Structure, Thermal Degradation, and Stability

Thermal degradation behavior, exothermic patterns, and kinetic parameters of symmetrically/asymmetrically substituted polysilanes during the kumada thermal rearrangement in the temperature range of 100–450 °C, were investigated applying thermogravimetric (TGA) and differential scanning calorimetric (DSC) techniques. Three kinds of polysilanes, viz., Polydimethylsilane (PDMS), Polydiphenylsilane (PDPS) and Polymethylphenylsilane (PMPS) were synthesized through Wurtz/Wurtz-Fittig polycondensation. As-synthesized polysilanes were then characterized by FT-IR, CHNO, and TGA–DSC techniques. FT-IR spectra confirmed the presence of methyl, phenyl, and a combination of methyl-phenyl functional groups in PDMS, PDPS, and PMPS, respectively. From CHNO analysis, the chemical/empirical formula of PDMS, PDPS, and PMPS was found to be SiC2.01H6.25, SiC12.50H10.26, and SiC6.45H7.76, respectively. TGA results confirmed that PDPS was more thermally stable as compared to PDMS and PMPS. The kinetic parameters of polysilanes were determined by using isoconversional methods such as Ozawa and modified Kissinger–Akahira–Sunose (KAS) methods. The average value of activation energy for PDPS obtained from Ozawa and KAS methods was found to be 1078.49 and 1068.32 kJ/mole, respectively, which is very much higher as compared to that of PDMS and PMPS.

Thermal Characteristics and Simulation of Enzymatic Lignin Isolated from Chinese Fir and Birch

Lignin is one of the main components of the plant cell wall, and the thermal properties of in situ biomass lignin are crucial for the multi-scale modeling of biomass properties and the thermodynamic modeling of lignin. In this study, high yields of double enzymatic lignin (DEL) were successfully isolated from softwood Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) and hardwood white birch (Betula platyphylla Suk.) to represent the in situ wood lignin. Their thermal properties, including specific heat capacity, thermal conductivity, thermal stability, and thermal degradation kinetic parameters, were tested and simulated. The results showed that Chinese fir DEL has different chemical structural units and thermal properties than birch DEL. The specific heat capacities of Chinese fir DEL and birch DEL at 20 °C were 1301 and 1468 J/(kg·K), respectively, and their thermal conductivities were 0.30 and 0.32 W/(m·K). Their specific heat capacity and thermal conductivity showed a positive linear relationship over a temperature range of 20–120 °C. Chinese fir DEL had a better thermal stability and a higher carbon residue than birch DEL. The average activation energy and pre-exponential factor changed with the conversion rate, and their relationships were simulated using linear or quadratic equations in the conversion rate range of 0.02–0.60. A second-order reaction function was found to be the best mechanism function for DEL thermal degradation.

Gamma irradiation effects on styrene butadiene rubber/Pb3O4: Mechanical, thermal, electrical investigations and shielding parameter measurements

Polymer composites of Styrene-Butadiene Rubber SBR filled with Pb3O4 have been prepared with different concentrations ranging between (4.5–37.8 wt%). The linear μ and mass attenuation coefficients μm of all samples have been investigated at energies 1173, 1333 and 662 KeV from 60Co and 137Cs point sources, and results were compared with the calculated one via WinXcom at the same photon energies, it was clear that μm increases in proportion to the concentration of filler. The radiation protection efficiency RPE% increased with increasing filler concentration while HVL (half-value layer) and TVL (tenth value layer) were decreased with increasing filler concentration; also, atomic effective number Zeff has computed. Activation energy of decomposition was calculated for samples that ranged from (190.71–225.74 J/K.mol), and kinetic parameters for thermal degradation of the SBR/Pb3O4 have been tabulated. The samples were irradiated with doses (50,100,150 and 200 kGy), mechanical properties have been carried out such as tensile strength, hardness (shore A) and elastic modulus, all showed improvement with irradiation doses up to 100 kGy except elongation at break decreased with increasing filler content. Electrical properties have been measured for the samples at room temperature to identify the conduction mechanism, which showed the applicability of Schottky-Richardson mechanism. The hopping distance of the charge carrier has been determined theoretically, ranging between (3 × 10−8 -1.43 × 10−8 m). Also, the dispersion and morphological analysis of composites have been studied using the Scanning Electron Microscope. The composites showed good performance as light-shielding material for low energies up to 300 KeV, where RPE% increased by increasing Pb3O4 concentrations from 8% (SBR1) to reach 46% (SBR5) at 662 KeV; similarly, the HVL decreased by 64% from (SBR1) to (SBR5).

Kinetic, thermodynamic and chemical reaction analyses of typical surgical face mask waste pyrolysis

The epidemic of Corona Virus Disease 2019 (COVID-19) has led to the generation of a large number of waste surgical masks. In recent years, pyrolysis is considered to be an environmental-friendly and efficient method to dispose such solid waste. In this work, the thermal degradation behaviors, kinetic parameters, thermodynamic parameters, pyrolytic products and chemical reactions of typical surgical face mask waste were studied using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR)-mass spectrometry (MS) analysis in inert atmosphere. It is concluded that the surgical face mask waste pyrolysis in nitrogen can be considered to be a one-step reaction. In addition, the mean E (activation energy) value and the mean A (pre-exponential factor) value are 237.19 kJ/mol and 1.36 × 1014 min−1, respectively. g(α) = (−ln(1-α))2/3 (reaction model) may be utilized to characterize the surgical face mask waste pyrolysis in nitrogen. The above kinetic parameters are capable to estimate the surgical face mask waste pyrolysis behaviors in nitrogen. Thermodynamic parameters suggest that the surgical face mask waste pyrolysis can be considered to be an endothermic and non-spontaneous reaction. Inorganic substances, alkanes, alkenes, naphthenic hydrocarbons, aldehydes and ketones are the major volatile products. The amount of the aliphatic compounds is the highest. Specific chemical reactions generating these volatile products are proposed.

Thermogravimetric and kinetic analysis of biomass and polyurethane foam mixtures Co-Pyrolysis

Alternative fuels are crucial for the decarbonisation of high-energy demanding processes. The utilisation of waste materials to produce alternative fuels is especially interesting since, the co-pyrolysis of waste plastics and biomass was lately introduced as promising method since the synergistic effect might enhance the product properties compared to those from individual pyrolysis. Furthermore, the utilisation of waste biomass, like sawdust, is interesting since it does not influence the sustainability of biomass consumption, and even more, it avoids the usage of raw feedstock. Thermogravimetric analysis is performed to determine the thermal degradation behaviour and kinetic parameters of investigated mixtures to find the most appropriate utilisation method. Co-pyrolysis was conducted for three mixtures with the following biomass/polyurethane ratios: 75-25%, 50-50%, 25–75%, over a temperature range of 30–800 °C, at three heating rates 5, 10 and 20 °C/min, under an inert atmosphere. Obtained results were subjected to comprehensive kinetic analysis to determine effective activation energy using the isoconversional model-free methods and provide a detailed analysis of the samples' thermal degradation process. This work aimed to identify the main thermal decomposition stages during co-pyrolysis of biomass and polyurethane mixtures and provide the mixture composition's influence on the considered thermochemical conversion process.

Comparison of waste plastics pyrolysis under nitrogen and carbon dioxide atmospheres: A thermogravimetric and kinetic study

It is important to understand the influence of pyrolysis atmosphere on the thermal degradation of waste plastics. In this study, the decomposition of waste plastics; high and low density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate were investigated from ambient temperature to 500 °C within nitrogen or carbon dioxide atmospheres. The thermal degradation characteristics and kinetic parameters of individual plastics and mixed plastics (household packaging, building construction and agricultural waste plastics) from three different waste treatment plants were investigated under N2, CO2 and N2/CO2 atmospheres. In all atmospheres, only one degradation peak temperature was observed between 250−510 °C. The replacement of N2 by CO2 showed different effects on the activation energy. Mixtures of N2/CO2 in the pyrolysis atmosphere resulted to lower activation energy for all plastic samples, with the exception of high density polyethylene, polystyrene and polyethylene terephthalate. The lower activation energy suggested that lower energy was required for the degradation process. However, a mixture of more than 30 % of CO2 may influence the degradation process of plastics due to a higher value of residue obtained after the experiment.

Thermal decomposition behaviour and numerical fitting for the pyrolysis kinetics of 3D spongin-based scaffolds. The classic approach

The kinetic parameters of thermal degradation of 3D skeletal biopolymer spongin - isolated from the marine demosponge Hippospongia communis, using thermogravimetric analysis (TG) were evaluated. The kinetic parameters of the pyrolysis in a nitrogen atmosphere were calculated using standard methods, including a model-fitting approach (Coats–Redfern method) and the model-free iso-conversional Friedman, Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) methods. Based on the kinetic parameters obtained from the respective equations, the changes of entropy (ΔS), enthalpy (ΔH), and free Gibbs energy (ΔG) were evaluated using the theory of the active complex of the reagent. It was found that the chemical reaction model best describes the experimental data. The activation energies calculated by the Coats–Redfern method were in the range 39.3–48.7 kJ/mol. The calculated values of kinetics parameters are slightly lower than for the commercial polyurethane foams. Nevertheless, this study provides a comprehensive insight into the pathway, mechanism, and outcomes of pyrolysis of spongin-based scaffolds with the relation to the physicochemical characteristics of finally obtained carbon materials. Moreover, a critical discussion of the obtained results is given, with regard to the physical meaning of the applied approximations.

Characterization, thermal and kinetic analysis of Pinusroxburghii

Uttarakhand has the maximum potential of pine of about 20 lakh tonnes/year including reserved forests and van panchayat which makes pine needle an abundant resource. The analysis of the pine needles reveals it a potential biomass feedstock for gasification to produce electricity. This manuscript deals with the combustion study of Pine needles (Pinusroxburghii) biomass using a thermogravimetric analyzer to investigate the thermal degradation behavior and kinetic parameters. The pine needles were heated in the presence of air at four different heating rates 5, 10, 25 and 50 °C/min, and the degradation phenomenon was studied. From the proximate and ultimate analysis of pine needles, it was observed that the biomass could be a potential feedstock for gasification. The TG-DTG curves revealed that the main decomposition was between 190 and 450 °C with the release of 80–84% volatiles. It was observed that as the heating rate increases, the maximum decomposition temperature also increases and the peak shifts to the right. The obtained thermal data were used to calculate the kinetic parameters using Kissinger–Akharia–Sunose, Ozawa-Flynn-Wall, Friedman and Kissinger. The average values obtained from the above methods are 190.74, 190.75, 199.48 and 172 kJ/mol and 2.749 × 1022, 5.13 × 1022, 4.21 × 1021 and 4.14 × 106/min, respectively. The model fitting method and Coats–Redfern method were used to determine the kinetic triplet (A, E and n). The above model-free methods and model fitting methods predicts the progress of gasification at different positions along the reactor. Considering proximate analysis and heating value, pine needles could be considered as a potential feedstock for energy production through gasification process. The estimated results help as a source to understand the thermal degradation of biomass during the gasification process and be used to design the systems.

Kinetic Analysis of Durian Rind Pyrolysis Using Model-Free Method

In this study, the thermal degradation behavior and kinetic parameters of durian rind were investigated by using the thermogravimetric analysis technique. The experiments were performed in the temperature range of 313 – 1,073 K with the heating rate of 5, 10, 20 and 40 Kmin−1. Three model-free methods namely Friedman (FR) method, Kissinger-Akahira-Sunose (KAS) method, and Flynn-Wall-Ozawa (FWO) method were used to attain the kinetic parameters. The results show that the thermal degradation of durian rind exhibits 3 stages including dehydration stage (up to 380 K), active pyrolysis stage (380 – 680 K) and passive pyrolysis stage (above 680 K). A maximum rate loss shifts to a higher temperature with an increases in the heating rate. The values of kinetic parameters obtained from FR, KAS and FWO methods are in a good agreement with the experimental results. The average activation energies calculated by FR, KAS and FWO methods are reported at 243.02, 220.38 and 218.33 kJmol−1, respectively. Combining with heating value and chemical structure of durian rind, it can be stated that durian rind can become a useful source of alternative fuels and/or chemical feedstocks.

Thermal characteristics of birch and its cellulose and hemicelluloses isolated by alkaline solution

AbstractCellulose and hemicelluloses were isolated from birch wood using a dilute alkaline solution and then consolidated into pellets as model compounds of cellulose and hemicelluloses in the wood cell wall. The purity of isolated cellulose and hemicelluloses was examined by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The density, thermal diffusivity, heat capacity, and thermal conductivity were experimentally determined for consolidated birch powder, cellulose, and hemicelluloses in over-dry condition. The thermal degradation kinetic parameters of these materials were successfully calculated using a conversion rate step of 0.01, and the relationship with conversion rate was established. The results show that cellulose and hemicelluloses consolidated under 25 MPa had densities of 1362 kg/m3and 1464 kg/m3, respectively. The cell wall of birch powder in the oven-dry state was not collapsed under 25 MPa. The thermal diffusivity of consolidated birch powder, cellulose, and hemicelluloses linearly decreased with temperature, with values of 0.08, 0.15, and 0.20 mm2/s at room temperature, respectively. The specific heat capacity (1104, 1209, and 1305 J/(kg·K) at 22 °C, respectively) and thermal conductivity (0.09, 0.24, and 0.38 W/(m·K) at 22 °C, respectively) linearly increased with temperature, except for those for hemicelluloses which exhibited a nonlinear relationship with temperature above 120 °C, and their linear experimental prediction equations were given. Birch cellulose was more thermally stable than hemicelluloses. The thermal degradation kinetic parameters including activation energy and pre-exponential factor of birch powder, cellulose, and hemicelluloses varied with the conversion rate and calculation methods, with average activation energy in a conversion rate range of 0.02–0.15 of 123.2, 159.0, and 147.2 kJ/mol, respectively (using the Flynn–Wall–Ozawa method), for average natural logarithm pre-exponential factors of 25.0, 33.1, and 28.7 min−1, respectively. Linear and quadratic equations were fitted to describe the relationship between the kinetic parameters and conversion rates. These results give comprehensive thermal properties of the densified cellulose and hemicelluloses isolated from a specific wood.

Calculation of Kinetic Parameters of Thermal Decomposition of Forest Waste using the Monte Carlo Technique

Abstract This paper deals with the pyrolysis of forest waste in the presence of an inert atmosphere. Experiments are carried out at different heating rates (5 °C, 10 °C and 15 °C) to determine derivative thermogravimetric behaviour of the material. Unlike the conventional scheme, the Monte Carlo technique is implemented to solve the distributed activation energy model (DAEM). DAEM is transformed into the inverse pyrolysis problem to determine the kinetic parameters of thermal degradation of forest waste. Activation energy, the preexponential factor and the distribution parameters are estimated by introducing the Monte Carlo Technique in the thermal conversion process.

An experimental study and numerical simulation of horizontal flame spread over polyoxymethylene in still air

A comprehensive study of thermal decomposition and combustion of a horizontally placed polyoxymethylene (POM) slab was performed. The kinetic parameters of thermal degradation of POM in supposition of two parallel reactions were determined and were used for simulation of the flame spread over the POM. The following main characteristics of the POM slab's combustion were measured: the flame spread rate, the slab's mass loss rate, the width of the pyrolysis zone, the flame height, the temperature profile of the upper and lower surfaces of the slab, the temperature field and the fields of the main flame species concentrations over the burning slab, and the conductive heat flux from the flame onto the fuel surface. It was concluded from analysis of experimental data that two global gas phase reactions may be identified: the reaction of formaldehyde pyrolysis with light combustible gas formed (with the properties close to those of СО) and the subsequent reaction of its oxidation in the flame to the end combustion products (СО2+H2O). This approach was implemented as the coupled combustion model was modified, taking into account a two-step reaction in the gas phase. The results of the calculations made showed good agreement with the experimental data.