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The next-generation energy economy relies heavily on hydrogen. Handling hydrogen during production, storage, and transportation requires risk mitigation. In this regard, the application of halide-free additives is very crucial. The present study experimentally and theoretically investigates the individual and combined inhibiting effect of propane and propene on hydrogen-air explosions. The experiments are carried out at 298 K and 1 bar, with additives ranging from 0.5 to 5% for the individual and 1–2% each for the combined effect in the 20–50% hydrogen-air mixture. Experimentally, the additive content in the stoichiometric and rich mixture decreases the explosion pressure, maximum pressure rise (MPR) rate, laminar burning velocity (LBV), and flame temperature, while increasing minimum ignition energy. For instance, the addition of 2% propane in a 50% hydrogen-air mixture, reduces the MPR rate by 98%, whereas such an effect is observed with 2.5% propene. Theoretical study shows that 3% equivalent additive augments inhibiting reactions, countering the main flame-promoting reaction R1 (H + O 2 O + OH) and thereby reducing LBV. Due to its low activation energy, propene consumes the active radicals twice the rate of propane, while propane not only scavenges the active radicals but also promotes oxygen consumption in the prior phase of combustion, weakening flame propagation. Overall, this approach exhibits a significant step forward in harnessing the potential of hydrogen while mitigating the safety risks associated with its use. [Display omitted] • The effect of C 3 -Hydrocarbons and their Mixtures on H2-air explosion is explored. • The additives decrease explosion pressure, MPR rate and LBV while increasing MIE. • Propene increases the consumption rate of active radicals in the additive mixtures. • Propane promotes oxygen consumption in the prior phase of combustion, countering R1. [ABSTRACT FROM AUTHOR]

This study presented the development of a reaction kinetics scheme based on saturates–aromatics–resins–asphaltenes (SARA) fractions to represent the complicated chemical reactions occurring during high-pressure differential scanning calorimetry (HP-DSC) tests. The heat release characteristics during heavy crude oil combustion were analyzed from a set of HP-DSC results. On the basis of this analysis, an improved reaction kinetics model, including low-temperature oxidation (LTO) reactions of SARA fractions, cracking of oxidized asphaltenes, and coke combustion, was established. Following that, this model was incorporated into Computer Modeling Group STARS to simulate the HP-DSC results. Both activation energy and frequency factor of each reaction were continuously tuned until the correct kinetics parameters were obtained by matching the simulation data with the HP-DSC experimental data. The experimental results indicated that the heavy crude oil experienced greater heat release due to LTO rather than high-temperature oxidation at 5 MPa, which differed from the results observed at atmospheric pressure. The simulation results showed that the energy required to activate the oxidation reactions in the HP-DSC experiments was similar to that in the numerical simulation. However, the oil sample was subjected to higher molecular collision frequency in the HP-DSC experiments than in the numerical simulation. Therefore, more attention should be given to adjusting frequency factor when determining the oxidation kinetics parameters in the numerical model. Overall, the SARA-based oxidation kinetics model successfully simulated the exothermic characteristics of the heavy oil during heating. [ABSTRACT FROM AUTHOR]

Pt-Pd-based noble metal catalysts are widely used in engine exhaust aftertreatment because of their better carbon soot oxidation performance. At present, the synergistic effect of Pt and Pd in CDPFs, which is the most widely used and common doping method, in catalyzing the combustion of carbon smoke has not been reported, and it is not possible to give an optimal doping ratio of Pt and Pd. This paper investigates the carbon soot oxidation performance of different Pt/Pd ratios (Pt/Pd = 1:0, 10:1, 5:1, 1:1) based on physicochemical characterization and particle combustion kinetics calculations, aiming to reveal the Pt-Pd synergistic effect and its carbon soot oxidation law. The results show that Pt-based catalysts doped with Pd can improve the catalyst dispersion, significantly increase the specific surface area, and reduce the activation energy and reaction temperature of carbon soot reactions, but excessive doping of Pd leads to the enhancement of the catalyst agglomeration effect, a decrease in the specific surface area, and an increase in the activation energy and reaction temperature of the carbon soot reaction. The specific surface area and pore capacity of the catalyst are the largest, and the activation energy of particle oxidation and the pre-exponential factor are the smallest (203.44 kJ∙mol−1 and 6.31 × 107, respectively), which are 19.29 kJ∙mol−1 and 4.95 × 108 lower than those of pure carbon soot; meanwhile, the starting and final combustion temperatures of carbon soot (T10 and T90) are the lowest at 585.8 °C and 679.4 °C, respectively, which are 22.1 °C and 20.9 °C lower than those of pure carbon soot. [ABSTRACT FROM AUTHOR]

In this work, the overall activation energy of the combustion of lean hydrogen–methane–air mixtures (equivalence ratio φ = 0.7−1.0 and hydrogen fraction in methane α = 0 , 2, 4) is experimentally determined using thin-filament pyrometry of flames stabilised on a flat porous burner under normal conditions ( p = 1 bar, T = 20 °C). The experimental data are compared with numerical calculations within the detailed reaction mechanism GRI3.0 and both approaches confirm the linear correlation between mass flow rate and inverse flame temperature predicted in the theory. An analysis of the numerical and experimental data shows that, in the limit of lean hydrogen–methane–air mixtures, the activation energy approaches a constant value, which is not sensitive to the addition of hydrogen to methane. The mass flow rate for a freely propagating flame and, thus, the laminar burning velocity, are measured for mixtures with different hydrogen contents. This mass flow rate, scaled over the characteristic temperature dependence of the laminar burning velocity for a one-step reaction mechanism, is found and it can also be used in order to estimate the parameters of the overall reaction mechanisms. Such reaction mechanisms will find implementation in the numerical simulation of practical combustion devices with complex flows and geometries. [ABSTRACT FROM AUTHOR]

Ultrafine materials with unique characteristics have a broad range of utilization. The motivation of this paper was to investigate the size effect on the thermo-oxidative degradation behaviors and chemical kinetics of polystyrene (PS) solid particles. In this study, microscopic PS particles with four different-diameter distributions, containing 5, 10, 15, and 50 μm, were picked as tested samples. Then, the thermogravimetry analysis test of PS samples was conducted under an air atmosphere with three different heating rates. Activation energies were calculated and validated by multiple traditional kinetic approaches, and a linear relationship between activation energy and the reciprocal of the particle diameter has been concluded. A distributed activation energy model (DAEM) with two pseudo-components was developed and employed to decouple the polyurethane pyrolysis in the air atmosphere. A set of nth-order reactions is hypothesized to occur with a constant pre-exponential factor and having a continuous activation energy distribution pattern conforming to the Gaussian density function in each kinetic process. A multi-parameter optimization program was developed to calculate ten DAEM parameters based on the experimental data from three different heating rates by avoiding the ill condition resulting from the kinetic compensation effect. Moreover, the numerical relationship between activation energies and particle diameter has been analyzed. The results of this study are instructive for the determination method of kinetic triplets, the modification of reaction models, and especially the construction of waste polymer kinetics and combustion models. [ABSTRACT FROM AUTHOR]

A set of eight coals from the premium Argonne coal sample program were studied using thermogravimetric and evolved gas analysis. Gaseous combustion products were analyzed using an FTIR spectrometer and a chemiluminescence analyzer. Additionally, modulated thermogravimetric experiments were carried out to determine activation energies associated with the combustion of each sample. The exhaust from the thermogravimetric analyzer was directed to the gas analyzers for detecting and quantifying CO, CO2, and NO. Evolved gas analysis was conducted at a ramp rate of 5°C for CO, CO2 evolution, and 20°C per minute for nitric oxide evolution, with the furnace temperature varying between 20°C–750°C. Modulated thermogravimetric analysis experiments were carried out in the same temperature range. The temperature was increased at a rate of 2°C per minute for the modulated experiments. Each test had a superposed temperature modulation with amplitude ±5°C and a period of 200 seconds. The experiments provide valuable information on the combustion kinetics and emission characteristics of selected American coals. [ABSTRACT FROM AUTHOR]

Water hyacinth(WH) is a promising resource produced as a by-product of treating pollution in watersheds, but little study has been done on its high-value applications. In this work, the combustion characteristics of WH, anthracite (AN), and their blends under different ratios, and heating rates were investigated by the thermogravimetric (TG) analyzer. The Kissen-Akahira-Sunose (KAS) and Flynn-WallOzawa (FWO) methods are used to calculate the dynamics, and the interaction between the mixed materials is discussed. The results show that the combustion characteristics of WH are better than those of AN because of its higher volatile components. With the increase of WH, the comprehensive combustion index increased from 0.15(pure AN) to 2.22(WH: AN=5:5). With the increase in heating rate, there is no significant difference in residual. The difference in thermogravimetric curves of mixed fuel in the volatile combustion stage and fixed carbon combustion stage shows that there is an interaction between WH and AN in the process of co-combustion, indicating that the mixed fuel is suitable for co-combustion. This study provides a theoretical basis for improving the efficiency of clean energy and reducing the consumption of fossil energy. [Display omitted] • The comprehensive combustion index increased significantly from 0.15 to 2.22. • 5:5 is a better solution for co-firing WH with AN. • There are interactions between WH and AN co-firing. [ABSTRACT FROM AUTHOR]

The challenges of this work focus on better understanding combustion characteristics and their importance to fire hazard by performing thermogravimetric analysis (TGA). The ultimate goal is to provide a methodology for determining the most relevant indices for a robust fire hazard classification of the species. One of the principles of this methodology is the use of a linear regression method for determining the indices and the activation energy. To achieve this scope, chemical, thermal and kinetic analysis will be performed. Nine combustion indices were calculated and compared to assess combustion characteristics such as ignition, combustion and burnout. Experiments were carried out at three heating rates of 10, 15 and 20 °C min−1 under air atmosphere. A selection of forest materials frequently devastated by wildfire, i.e., Quercus pubescens (QP), Quercus suber (QS), Olea europaea (OE) and Genista Salzmannii needles (GSN), were studied. The TG-DTG curves have shown that the combustion process consists of two stages: devolatilization and char oxidation. The whole process was controlled by the release of volatile gases. According to the relative linearized (RL) index of spontaneous ignition, the samples were ordered as follows: OE > GSN ≥ QS > QP. OE appears to be the most reactive and prone to spontaneous ignition compared to the other samples. The same order was achieved for the combustion characteristic index and, approximately, for the integrated flammability. On the other hand, the average Ea at the low temperature stage of the combustion process was low for GSN (147 ± 9 kJ mol−1) and OE (159 ± 4 kJ mol−1) and high for QP (179 ± 14 kJ mol−1) and QS (174 ± 3 kJ mol−1). Finally, this work provides valuable insight into the relationship between chemical properties and combustion indices and the components that make some indices more effective than others. [ABSTRACT FROM AUTHOR]

Pyrolysis of rice husk (RH), alkali-treated cellulose-rich rice husk (RHC), chemically modified RHC (RHCM) and RH-biocomposites by thermogravimetric analysis was carried out to determine combustion and kinetic parameters at three different heating rates of 20, 40 and 50 °C min−1. Combustion performance was analyzed from results of ignition temperature, burnout temperature, combustion rates, flammability index and combustion characteristic index. Increase in heating rate from 20 to 40 and further to 50 °C min−1 increased the onset of degradation, burnout and peak temperatures as observed by curve shifts to the right. Maximum combustion rates were around 0.57–0.59% min−1, 1.03% min−1 and 0.63–0.69% min−1 for RH, RHC and RHCM, respectively. For the RH-biocomposites, the maximum combustion rates were in a 0.76–0.97% min−1 range. Their average pre-exponential factors using KAS method were in the 2.24E-03–8.07E-03 range, respectively, while those for OFW method were in the 7.75E + 04–4.55E + 06 range, respectively. Average activation energies of RH-biocomposites were in the 41.0–58.2 kJ mol−1 and 48.3–67.7 kJ mol−1 ranges for KAS and OFW methods, respectively. The data were well fitting with coefficient of determination (R2) values close to 1. Average ΔG value ranges for RH-biocomposites ranged between 148.2 and 161.7 kJ mol−1. The low-energy barrier (≤ 5.4 kJ mol−1) between activation energy and enthalpy changes indicated that reaction initiation occurs easily. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The concerted elimination reaction class of peroxyl-hydroperoxyl alkyl radicals (•OOQOOH) plays a crucial role in the low-temperature combustion of normal-alkyl cyclohexanes. The generation of the relatively unreactive HO2 radicals in this reaction is one of the factors leading to the negative temperature coefficient (NTC) behavior, which hinders the low-temperature oxidation of normal-alkyl cyclohexanes. In this study, 44 reactions are selected and divided into 4 different subclasses according to the nature of the carbon atom where the H atom is eliminated and the reaction center position. Utilizing the CBS-QB3 method, we compute the energy barriers for the concerted elimination reactions of peroxyl-hydroperoxyl alkyl radicals. Following this, we assess both the high-pressure limit and pressure-dependent rate constants for all reactions by applying TST and RRKM/ME theory. These calculations allow for the development of rate rules, which come to fruition through an averaging process involving the rate constants of representative reactions within each subclass. Our work provides accurate rate constants and rate rules for this reaction class, which can aid in constructing more accurate combustion mechanisms for normal-alkyl cyclohexanes. [ABSTRACT FROM AUTHOR]

This research investigates the non-isothermal thermogravimetric analysis and kinetics of oil shale samples at different heating rates and in the air atmosphere. In all the oil shale samples studied, the TG-DTG curves indicated that the decomposition of oil shale samples followed two successive reaction stages in different temperature intervals, known as combustion and mineral decomposition. This stage determines reaction intervals, peak temperature, mass loss, and derivative mass loss rate values of oil shale samples. At the same time, the different combustibility indices such as the ignition index, combustion index, and reactivity of oil shale samples are also determined. Also, for each reaction region, activation energy values were calculated using four different model-free methods known as Kissinger—Akahira—Sunose, Ozawa—Flynn—Wall, starink, and distributed activation energy model. In combustion and mineral decomposition regions, the activation energy values varied between 122.9–162.5 kJ mol−1 and 169.9–264.2 kJ mol−1, respectively. At the same time, kinetic models were validated by comparing the experimental and simulated conversion curves. [ABSTRACT FROM AUTHOR]

This study investigated the pyrolysis properties and kinetic behavior of Ermenek (Konya, Turkey) lignite. For this purpose, lignite was carbonized at 500°C and different heating rates (5, 10, 15, and 20°C/min). Proximate, elemental, XRF, and TGA-DTA lignite and chars were performed. Thermal analyses were performed at a heating rate of 10°C/min from room temperature to 1000°C and an inert (N2) gas flow of 50 ml/min. Peak temperatures and mass losses were determined from the data obtained from the experiments. By examining the thermogram curves, three different temperature regions depended on moisture loss, the release of volatile matter, and fixed carbon combustion. In addition, from these data, kinetic calculations were performed using Arrhenius and Coats-Redfern approaches, and the apparent activation energies were calculated for each region. The activation energy values calculated according to the Coats-Redfern kinetic model are significantly lower than those calculated according to the Arrhenius kinetic model. The highest activation energies calculated were: for Region 1 and Region 2 at 5°C/min heating rate and for Region 3 at 10°C/min heating rate. [ABSTRACT FROM AUTHOR]

Coal mine conveyor-belt fires account for numerous mine disasters. Accurate prediction of burning degree is one of the critical factors in preventing and controlling conveyor-belt fires. The sparse qualitative smoke-detection method is challenging to meet the precise early warning of belt fire. Therefore, the Tangkou mine transportation belt was used to analyze TG-DTG curve change late, gas generation law, conversion rate, and apparent activation energy, and other factors at four heating rates via TG-FTIR experiments. The seven characteristic temperatures and their thresholds during belt combustion were experimentally determined, and the process was divided into three stages (I, II, III). The process mainly generated CH4, CO, CO2, and other gases, and the temperature range of various gases was identified. The conversion degree rate of each stage was positively correlated with the temperature. In Stages I and II, activation energy increased with the conversion rate and then decreased. Rate and temperature corresponding to the maximum activation energy were determined. Dynamic compensation effect of the belt combustion process was found. The reactions that could occur at each stage were inferred based on the above-mentioned characteristics; these findings were essential to intelligent comprehensive monitoring and early warning of conveyor-belt fire in a mine laneway. [ABSTRACT FROM AUTHOR]

It has been established that, contrary to previous ideas, chemical processes in flame propagation, explosion, and detonation of gases are chain reactions proceeding according to previously unknown laws of nonisothermal chain processes. The characteristic reaction times in deflagration and detonation in the combustion zone are less than a ten-thousandth and millionth of a second, respectively. The mechanisms and laws that determine these high rates and accelerations of reactions and their extremely strong temperature dependence were revealed. The critical role of atoms and radicals, formed in concentrations reaching tens of percent of the concentrations of the initial reagents, was shown using kinetic and spectroscopic methods. Efficient chemical methods for controlling all combustion modes were developed. [ABSTRACT FROM AUTHOR]

Degradation behavior of combustible fuel is the core factor in determining combustion characteristics. To investigate the effect of ambient atmosphere on the pyrolysis process of polyoxymethylene (POM), the pyrolysis mechanism of POM was studied with thermogravimetric analyzer tests and Fourier transform infrared spectroscopy tests. The activation energy, reaction model, and estimated lifetime of POM pyrolysis under different kinds of ambient gases have been estimated in this paper based on different results of the kinetics. The activation energy values, obtained with different methods, were 151.0–156.6 kJ mol−1 in nitrogen and 80.9–127.3 kJ mol−1 in air. Then, based on the Criado analysis, the pyrolysis reaction models of POM in nitrogen were found to be mastered by the "n + m = 2; n = 1.5" model, and by the "A3" model in air. The optimum processing temperature for POM was estimated, with a range from 250 to 300 °C in nitrogen and from 200 to 250 °C in air. IR analysis revealed that the significant difference in POM decomposition between N2 and O2 atmospheres is the formation of isocyanate group or carbon dioxide. Combustion parameters of two POMs (with and without flame retardants) obtained using cone calorimetry revealed that flame retardants can effectively improve the ignition time, smoke release rate, and other parameters of POM. The outcomes of this study will contribute to the design, storage, and transportation of polyoxymethylene. [ABSTRACT FROM AUTHOR]

The behavior of the coal was investigated in order to estimate the kinetics of the devolatilization, owing to the fact that combustion and gasification were strongly dependent on this step. The purpose of this work was to advocate the mathematical model supported by the parameters obtained from the thermogravimetric analyzer and pot apparatus experimental data. The thermal decomposition of coal follows a distributed activation energy model, which describes the kinetics of volatile matter release as a set of independent, parallel first-order reactions resulting from the coal ultimate analysis. The coke yield was calculated using the mass balance method, which develops the correlation for changes in the composition and mass of the solid residue. The present work develops a numerical code to solve the equations for standardized volatile coals under constant heating rate conditions and calculates the yields, composition of species, semi-coke, and mean relative atomic mass in the charge. [ABSTRACT FROM AUTHOR]

The application of one-step irreversible Arrhenius kinetics to the numerical description of biogas supersonic combustion (also known as detonation) with nitrogen N2 dilution is investigated in this study. The three model parameters: the temperature exponent n, the activation energy Ea, and the pre-exponential factor Ar are chosen to describe biogas detonation velocities. It can be seen that as the N2 dilution reached 50%, changes in Ea caused a significant drop in biogas detonation velocity, which was also observed in the current biogas detonation experiment, demonstrating that the dependence of high and low Ea values could appropriately tailor for changes in the thermodynamic condition of the reaction zone behind the detonation fronts as the N2 dilution increased. Via the validation feedback loop processes with the experimental and detailed chemistry (GRI Mech 3.0) results as the main validation basis, the resulting chemistry description in the one-step model is able to reproduce biogas detonation velocities with reasonable accuracy (< 15% discrepancy). Hence, the model overcomes the known gap of prior establishments of one-step Arrhenius kinetics for detonation by incorporating the N2 dilution effect and biogas as a fuel for detonation emergence. [ABSTRACT FROM AUTHOR]

The paper presents the thermal degradation of low-density wood sawdust (LDS) and high-density wood sawdust (HDS) under a nitrogen gas atmosphere using thermogravimetric analysis together with the assessment of their combustion parameters. A thermal conversion experiment was carried out at three different heating rates (5°C, 10°C, and 15°C/min) for three different particle sizes (<0.6, 0.6 ≤ x ≤ 0.8 , 0.8 > x ≤ 1 mm). The DTGmax showed that the HDS ( ≤ 17.9) experienced more weight loss than the LDS ( ≤ 15.8) , for the three particle sizes at different heating rates. There were no relevant differences in ignition temperature and burnout temperature for the two sawdust at different particle sizes. The HDS had more ignition index (between 2.02 and 58.83 wt.%/min3 *10−3) at all particle sizes, indicating better performance than the LDS (between 1.27 and 49.99 wt.%/min3 *10−3). The kinetics analysis shows that the activation energy varies with heating rate and particle size. The average activation energy for the HDS ranged between 51.43 and 154.69 kJ/mol, while for the LDS it ranged between 45.90 and 172.78 kJ/mol. This indicates that the HDS burns quicker and is a better fuel. Also, these combustion parameters will aid in optimizing combustion processes and designing efficient combustion systems. [ABSTRACT FROM AUTHOR]

Cables modified with flame retardants are widely used in the coal mining process to enhance their fire safety performance. This paper investigates experimentally and numerically the thermo-oxidative degradation process of PVC-based mining cable sheath, which consists of PVC resin and plasticizers (Phthalate esters), fillers (Calcium carbonate), and flame retardant (Antimony trioxide) as additives. Thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) experiments were performed at different heating rates in an air atmosphere. TG results showed that the decomposition processes of mining PVC cable sheath are more complicated than those of pure PVC with additional degradation steps, which was further confirmed by FTIR gas analysis. A deconvolution method was used to distinguish the independent reactions from the overlapped derivative thermogravimetric (DTG) peaks. It was found that the whole degradation process can be divided into seven steps, based on which an oxidative pyrolysis model was developed: pyrolysis of plasticizers (steps 1 and 2), dehydrogenation (step 3), emission and combustion of volatile fraction (step 4), carbon combustion (step 5), oxidative pyrolysis of complicated additives (step 6), and decomposition of residues (step 7). The kinetic triplets (activation energy, pre-exponential factor, and reaction model function) for each reaction were firstly calculated using three commonly used model-free methods and then further optimized using the genetic algorithm (GA). Based on the optimized parameters, the reaction mechanisms and their associated kinetic parameters were determined. The findings of this study are important in understanding the oxidative pyrolysis process of PVC cable sheath, and the obtained kinetic parameters can also be used for its pyrolysis and fire modeling, waste recycling, and risk assessment. [ABSTRACT FROM AUTHOR]

In O2/N2 and O2/CO2 atmospheres with oxygen concentrations of 21%, 30%, and 50%, combustion characteristics index, apparent activation energy, and kinetics models of D.P.R Korea's anthracite (KA) were estimated and compared. At the same oxygen concentration condition, combustion characteristics of KA in O2/CO2 atmosphere were more clearly reduced than those in O2/N2 atmosphere. And the ignition, burnout and comprehensive combustion indexes in 21% O2/79% N2 (general air) and 30% O2/70% CO2 atmosphere were almost identical. As a result of estimating the apparent activation energy, the lowest average of it was recorded in both O2/N2 and O2/CO2 atmosphere at 30% oxygen concentration among three oxygen concentration. Besides, it was found that when KA was burned in an O2/CO2 atmosphere condition with an oxygen concentration of 30%, the average apparent activation energy was the smallest. Kinetics models under various heating rates were estimated using the Kissinger–Akahira–Sunose (KAS) method. As a result of comparison, the consistency between 21% O2/79% N2 (general air) and 30% O2/70% CO2 was further confirmed in kinetics model. [ABSTRACT FROM AUTHOR]

The combustion behavior of fructose-derived hydrochar was investigated using a kinetic evaluation protocol that brings about novel elements related to the use of hydrochars as combustibles. The assessment procedure involves three steps implying the determination of the apparent activation energy (E) dependence on the conversion degree via model-free (isoconversional) methods, the estimation of the proposed kinetic scheme and corresponding kinetic parameters via nonlinear regression procedures, and the confirmation of the obtained results via different additional thermal analysis programs. The most probable kinetic scheme and corresponding kinetic parameters of the carbonaceous materials thermo-oxidation consists in five successive degradation processes following the Avrami–Erofeev model. The pair kinetic scheme–kinetic models leads to satisfactory agreement between experimental and calculated data and can be used in predictions of the conversion degree versus time development under different temperature programs. The used protocol is a first step to comparing hydrothermal carbonaceous materials' combustion performance. [ABSTRACT FROM AUTHOR]

To study the thermal decomposition behavior of 4,4′-azobis(1,2,4-triazole) (ATRZ), the non-isothermal thermal decomposition kinetics of ATRZ were studied using the thermogravimetric–differential scanning calorimetry (TG–DSC) method. The TG–DSC of ATRZ was analyzed at heating rates of 5, 10, 15, and 20 K·min−1 in an argon atmosphere. The thermal decomposition kinetic parameters at peak temperature (Tp), such as apparent activation energy (Ea) and pre-exponential factor (lgA) of ATRZ, were calculated using the Kissinger, Ozawa, and Satava–Sestak methods. Ea and lgA calculated using the Kissinger, Ozawa, and Satava–Sestak methods are very close, at 780.2 kJ·mol−1/70.5 s−1, 751.1 kJ·mol−1/71.8 s−1, and 762.1 kJ·mol−1/71.8 s−1, respectively. Using a combination of three methods, the reaction mechanism function g(α) of ATRZ was obtained. The results show that the decomposition temperature of ATRZ is about 310 °C, and the decomposition is rapidly exothermic. The pyrolysis path of ATRZ was investigated through a pyrolysis-gas chromatography mass spectrometry (PY-GC/MS) experiment. ATRZ has three different decomposition paths and finally generates N2, HC-N-CH, N≡C-N, and HC=N-C≡N. The laser ignition combustion duration of ATRZ was 0.5033 s and the peak temperature was 1913 °C. The laser ignition combustion duration of ATRZ+CL-20 was 1.0277 s and the peak temperature was 2105 °C. The rapid energy release rate of ATRZ promotes the combustion energy release of CL-20. [ABSTRACT FROM AUTHOR]

Through TG analysis, the effects of four heating rates on the combustion behavior of sludge in air atmosphere were studied. Two models of Flynn-Wall-Ozawa（FWO） and Distributed-Activation-Energy-Model（DEAM） were used to calculate the kinetic and thermodynamic parameters of sludge combustion. The experiments showed that when the heating rate was 20 K·min-1, there was a relatively obvious main peak in the DTG curve of sludge in the air atmosphere. The main combustion stage occurred between 433 and 923 K, and the mass loss of sludge was 33. 646%. The heating rate basically had no effect on the sludge combustion process and the values of S, C and Di under the four heating rates all gradually increased with the increase of the heating rate. The average values of Ea calculated by the two models were 53. 875 and 50. 298 kJ·mol-1, and the average values of R~2 were 0. 9616 and 0. 9531, respectively, indicating that both FWO and DEAM can estimate the activation energy of sludge combustion. Reset [ABSTRACT FROM AUTHOR]

Methyl acetate is considered a prototype molecule to study biodiesel ignition and combustion and is seen as a possible fuel or fuel additive. For this reason, methyl acetate decomposition paths have been investigated in recent years. In the present study, hydrogen abstraction reactions on methyl acetate by OH(2Π), HO2(2A'), H(2Σg), O(3P), and O2(3Σg) were conducted, and the effect of methodology and anharmonic corrections on the rate coefficients were evaluated. The M06-2X and B3LYP-D3 functionals with the cc-pVDZ, cc-pVTZ, aug-cc-pVDZ, and aug-cc-pVTZ basis set were used for methodology evaluation and the CCSD(T)/cc-pVTZ//M06-2X/aug-cc-pVTZ for the rate coefficients calculation and literature comparisons. The rate coefficients were calculated in the range of 250–3500 K, including tunneling corrections, methyl-hindered rotations, and anharmonic effects calculated by the VPT2 method. The methodology analysis showed that the B3LYP-D3 functional leads to lower activation energies for all elementary reactions studied, and the double-zeta basis is insufficient to calculate precise rate coefficients. The inclusion of anharmonic corrections consistently lowered the rate coefficients of all elementary reactions studied and changed the Arrhenius plot profile with the temperature. Significant anharmonic effects were observed at higher temperatures, being the reaction with O2(3Σg) the most affected by this correction. Differences superior to 105 cm3 molec−1 s−1 in the rate coefficients were observed in some cases. [ABSTRACT FROM AUTHOR]

Aerosol forming composite (AFC) is an important component of condensed aerosol-based fire extinguishing system (CAFES). As per literature no attempts have been made so far for the detailed study of AFCs. Therefore, for the insight AFCs were prepared with potassium nitrate as an oxidizer and phenol formaldehyde resin as a combustible binder. Five metal oxides, namely MnO2, Fe2O3, NiO, CuO and CeO2, (3%, w/w) were added as catalysts in AFC. The catalytic effect of these metal oxides was investigated for various parameters such as combustion efficiency, burn rate, minimum fire extinguishing concentration (MEC), decomposition temperature and activation energy. Addition of CuO, 3%, w/w increased the burn rate of AFC by 51.4% and reduced the MEC by 29.4%. Thermogravimetric analysis and differential scanning calorimetry analysis clearly indicated the reduction in decomposition temperature from 445.65 to 396.48 °C while adding CuO. Activation energies of decomposition for base AFC and AFC-CuO calculated using model-free methods of Kissinger, Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose were found to be 181.12, 183.50 and 180.75 kJ/mol and 146.61, 149.98 and 163.18 kJ/mol, respectively. The functions 1−(1−α)2/3 (model F1/3: One-third order) and [1−(1−α)1/2] (model R3, F2/3: power law) were found as the most probable mechanism for the thermal decomposition of base AFC and CuO-AFC, respectively. Aerosol characterization with X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and particle counter indicated mostly 2 µm particles of potassium carbonate/bicarbonate. Total flooding and dispersion characteristics of aerosols were confirmed using pH measurements at various locations. Overall, prepared AFCs were found promising for use within CAFES. [ABSTRACT FROM AUTHOR]

The 3D metal–organic framework (MOF), MIL-88B, built from the trivalent metal ions and the ditopic 1,4-Benzene dicarboxylic acid linker (H2BDC), distinguishes itself from the other MOFs for its flexibility and high thermal stability. MIL-88B was synthesized by a rapid microwave-assisted solvothermal method at high power (850 W). The iron-based MIL-88B [Fe3.O.Cl.(O2C–C6H4–CO2)3] exposed oxygen and iron content of 29% and 24%, respectively, which offers unique properties as an oxygen-rich catalyst for energetic systems. Upon dispersion in an organic solvent and integration into ammonium perchlorate (AP) (the universal oxidizer for energetic systems), the dispersion of the MOF particles into the AP energetic matrix was uniform (investigated via elemental mapping using an EDX detector). Therefore, MIL-88B(Fe) could probe AP decomposition with the exclusive formation of mono-dispersed Fe2O3 nanocatalyst during the AP decomposition. The evolved nanocatalyst can offer superior combustion characteristics. XRD pattern for the MIL-88B(Fe) framework TGA residuals confirmed the formation of α-Fe2O3 nanocatalyst as a final product. The catalytic efficiency of MIL-88B(Fe) on AP thermal behavior was assessed via DSC and TGA. AP solely demonstrated a decomposition enthalpy of 733 J g−1, while AP/MIL-88B(Fe) showed a 66% higher decomposition enthalpy of 1218 J g−1; the main exothermic decomposition temperature was decreased by 71 °C. Besides, MIL-88B(Fe) resulted in a decrease in AP decomposition activation energy by 23% and 25% using Kissinger and Kissinger–Akahira–Sunose (KAS) models, respectively. [ABSTRACT FROM AUTHOR]

The study aims to discover the co-combustion reaction mechanism of agricultural waste hydrochar and anthracite and to clarify the main influencing factors of the co-combustion reaction of the mixture. At the same time, it also provides a theoretical basis for revealing the optimal ratio of biomass hydrochar in the mixture and the application of biomass hydrochar in steel plants. Biomass hydrochar and anthracite were systematically investigated by physicochemical property analysis and non-isothermal thermogravimetric analysis. The results show that biomass hydrochar has better combustion performance due to the lower graphitization order and larger specific surface area, while the combustion performance of anthracite is relatively poor. The addition of biomass hydrochar can improve the combustion performance of anthracite. There is an obvious synergy in the co-combustion process due to the differences in the volatile content and graphitization degree of different samples. Two kinetic equations, Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO), are used to perform kinetic fitting on the combustion reaction of the mixture, but the fitting effect of the FWO equation is better than that of the KAS equation. The FWO kinetic fitting results indicate the optimum addition amount of 60% hydrochar with the smallest activation energy (118.95 kJ/mol). The research on the co-combustion of biomass hydrochar and anthracite is vital, contributing to the formation of biomass resource industrial applications. [ABSTRACT FROM AUTHOR]

Global warming and the GHG effect have forced the reduction of the energetic dependence on fossil fuels. Because of that, research focusing on biomass properties, characteristics and energetic conversion has increased in the last decades. The present study was carried out in terms of determination of kinetic parameters, focusing on two different energetic conversion processes: pyrolysis, carried out under nitrogen atmosphere, and oxygen-enriched combustion, using an atmosphere of air enriched with 30% oxygen. Three different lignocellulosic biomass samples were used. Thermogravimetric analysis was performed using four different heating rates in order to carry out a kinetic analysis using model free methods (Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa). The results showed that oxygen-enriched combustion produced a more complete reaction with low char values and activation energy values greater than pyrolysis values. Among the kinetic methods, Friedman reported the most different values, acceptable for pyrolysis process but not so much for oxygen-enriched combustion. [ABSTRACT FROM AUTHOR]

Random stacking of waste foundry sand will cause great environmental pollution, so it is necessary to recycle the waste foundry sand produced by resin-bonded sand technology by hot-reclamation to eliminate the residual resin on its surface. The study of thermodynamics analysis of resin binder for casting in combustion decomposition process can provide theoretical support for thermal reclamation. In this paper, TG–DTA technology was applied to measure TG, TGA, DTG curves of the three kinds of resin binders at 0–800 °C (furan resin binder, phenolic urethane resin binder and alkaline phenolic resin binder). The ignition point, reaction peak temperature, activation energy, mode function and other parameters of the three resin binders were calculated by the curves, and conclusions are as follows: (1) Furan resin binder, phenolic urethane resin binder and alkaline phenolic resin binder were heated to 800 °C in air at a heating rate of 15 °C min−1, and their residual mass was 9.8%, 2.7% and 33.7%, respectively; (2) the highest activation energy of furan resin binder, phenolic urethane resin binder and alkaline phenolic resin binder was 82.35 kJ mol−1, 90.77 kJ mol−1 and 335.77 kJ mol−1, respectively; (3) the reaction mode of three resin binders in each stage is Acceleratory α-time(n = 1), f(α) = α, G(α) = lnα. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) are interesting materials for use in several aspects: energy storage material, gas sensing, and photocatalysis. The thermal stability and pyrolysis process are crucial to determine the active phase of the material. A deep understanding of the pyrolysis mechanism is in demand. So, the thermodynamics and combustion process with different heating rates were examined, and the kinetic parameters were computed employing thermogravimetric tests. Based on the TG analysis of combustion, pyrolysis moves to the high-temperature region with an increase in heating rate. The decomposition process can be separated into dehydration (300–503 K) and pyrolysis reaction (703–1100 K). Three points of the decomposition process are performed by dynamical analysis owing to shifts of slopes, but the combustion process has only one stage. Dynamical parameters, for instance, the possible mechanism, the pre-exponential factor, and the apparent activation energy were obtained through comparison using the Kissinger formula. The thermodynamics analysis of the Zn1−xCox ZIF-8 materials is an effective way to explore the temperature influence on the process of pyrolysis, which can benefit in several recent applications. [ABSTRACT FROM AUTHOR]

• Effects of blending ratios and 21%–50% O 2 -enriched O 2 /CO 2 atmospheres were studied. • As O 2 enrichment increased, ignition (T i) and burnout (T e) temperatures decreased. • T i increased and T e decreased as coal content increased. • Combustion characteristic index (S) increased with coal addition and O 2 enrichment. • The larger the conversion degree, the smaller the activation energy value. This research investigated the thermogravimetric analysis (TGA) and combustion kinetics of sewage sludge and Australian sub-bituminous coal and their blends with different mixing ratios (sludge/coal = 100/0, 80/20, 50/50, 20/80, 0/100 by weight) under air atmosphere (O 2 /N 2 = 21/79 by volume), oxy-fuel combustion (O 2 /CO 2 = 21/79, 25/75, 35/65, and 50/50 by volume), and pyrolysis (pure N 2 atmospheres). The gaseous products that evolved from the TGA experiments were also analyzed using a Fourier transform infrared (FTIR) spectrometer under pyrolysis conditions. Results showed that the mixed fuel with higher coal blending ratio had higher ignition temperature, lower burnout temperature and larger combustion characteristic index. Furthermore, TGA–FTIR experiments of the 20 % sludge + 80 % coal blended fuel under nitrogen atmospheres showed more gasification components in pure coal than in sludge. The combustion kinetics analytical results via the Flynn–Wall–Ozawa method indicated that the larger the conversion degree, the smaller the obtained activation energy value. Under the oxy-fuel combustion conditions, when the oxygen concentration increased from 21 % to 50 % for the 20 % sludge + 80 % coal blended fuel, the ignition and burnout temperatures decreased, and the combustion characteristic index increased nearly three times. Oxygen enrichment can clearly improve combustion characteristics and flammability. [ABSTRACT FROM AUTHOR]

In this study, inorganic salts (KMnO 4 , Ba(NO 3) 2) and enzymolysis lignin were added into torrefied biochar to improve the drawback of high ignition temperature during combustion when biomass underwent torrefaction. Weight loss characteristics, gas products, combustion kinetics of torrefied biochar with different additives were investigated. The addition of KMnO 4 , Ba(NO 3) 2 , enzymolysis lignin, and their blends can reduce the ignition point of torrefied biochar, and the addition of Ba(NO 3) 2 can also extent the burnout time. When KMnO 4 , Ba(NO 3) 2 and lignin were added at the same time, the first weight loss peak temperature was reduced, and the reaction rate was accelerated. The combustion kinetics of torrefied biochar with different inorganic salts/lignin can be described by a simple first-order reaction. The addition of different inorganic salts/lignin additives is beneficial to reduce the activation energy of the low temperature reaction stage, and the activation energy of torrefied biochar with lignin addition decreases the most. [Display omitted] • KMnO 4 , Ba(NO 3) 2 and lignin could be used as combustion improver. • Ignition temperatures of torrefied biochar decreased with additives. • Activation energy of torrefied cellulose decreased with additives. • The number of effective molecular reactions of lignin increases with additives. • Inorganic salts addition could enhance depolymerization of cellulose. [ABSTRACT FROM AUTHOR]

• Static oxidation tests on tight shale were conducted. • Negative ion FT-ICR MS was used to analyze compositional alterations in shale oil due to oxidation. • Self-ignition potential of shale oil was evaluated using ARC. • Reaction order and activation energy during shale oil oxidation were determined. The oxidation behavior and kinetics of crude oil within tight shale differ from those of traditional light and heavy oils. In this study, the static oxidation tests on tight shale samples were conducted under different oxygen concentrations (11%, 16%, 21%, and 26%), followed by analysis of effluent gas and oxidized oil. Specifically, the compositional changes in shale oil at the molecular level were studied. Additionally, the self-ignition potential of shale oil under different oxygen concentrations was evaluated using accelerating rate calorimetry, and the corresponding kinetic parameters were determined. The results indicated that as the oxygen concentration increased from 16% to 26%, the relative abundance of O 1 species decreased from 10.96% to 8.66%, whereas that of O 3 species increased from 6.16% to 8.46%. Also, the relative abundance of chain saturated aliphatic acids and tricyclic naphthenic acids was observed to decrease and increase, respectively, in the shale oil oxidized at 26% oxygen concentration compared to the other shale oils oxidized at oxygen concentration lower than 26%. The shale oil displayed significant oxidation activity under different oxygen concentrations (16%, 21%, and 26%), and an increased oxygen partial pressure resulted in a shorter induction period of oxidation and higher combustion intensity. The kinetics results showed that the combustion activity of coke was enhanced while increasing oxygen concentration from 16% to 26%. The shale oil encountered fewer concentration-dependent oxidation reactions under higher oxygen concentration. Overall, this study provides valuable insights into the oxidation behavior of crude oil within tight shale. [ABSTRACT FROM AUTHOR]

The green gas generator 5-aminotetrazole (5-AT) is widely applied as an energetic material due to its exceptional characteristics. To investigate the impact of oxidants on the decomposition performance of 5-AT, we prepared three samples using three different oxidants (Sr(NO 3) 2 , KNO 3 , and KClO 4) along with 5-AT under the principle of zero oxygen balance. Then, thermal behavior of the three samples was examined using TG-DTA and TG-FTIR, and their activation energies for each reaction stage were calculated using iso-conversional methods. Results show that the decomposition of these samples occurs in multiple reaction stages and all oxidants, particularly KNO 3 , facilitate the thermal decomposition of 5-AT. Furthermore, the detailed decomposition mechanism of 5-AT with oxidants was speculated, including that there are two simultaneous ring-opening paths in the first thermal decomposition step of each 5-AT isomer. Eventually, this research can give a meaningful instruction to the formulation design of gas-generation propellant with fewer restrictions in their application. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sealing strips + filling materials (EPDM &EG) evaluated to use as value-added fuels. • Comprehensive evaluations of pyrolysis, kinetic, combustion parameters carried out. • EPDM exhibits good thermal stability. • EG demonstrates favorable pyrolysis properties and expansion densification. • Under effect of high temperature, smoke released from EPDM-R is larger than EPDM-O. • Average activation energies of EPDM-O and EPDM-R were 68.35 and 92.40 kJ·mol−1. Seals play a crucial role in preventing flame penetration through building exterior windows. However, as urban renewal accelerates, the number of discarded seals is also gradually increasing, which is not in line with the concept of green, energy-saving sustainable development. To gain a better understanding of the pyrolysis and combustion characteristics of sealing strips and facilitate their effective resource utilization and conversion into value-added fuels, we employed thermogravimetry, cone calorimetry, and flue gas spreading test equipment. Typical sealing and filling materials used for external windows of buildings, including EPDM ordinary adhesive strips (EPDM-O), EPDM flame-retardant adhesive strips (EPDM-R), as well as 20-fold expanding graphite strips and 30-fold expanding graphite strips (EG-20 and EG-30), were investigated. Comprehensive evaluations of their pyrolysis behaviors, kinetic parameters, and combustion characteristic parameters were carried out. The results showed that EPDM exhibits good thermal stability, while EG had better demonstrates favorable pyrolysis properties and expansion densification. Average activation energies of EPDM-O and EPDM-R in the combustion phase were 68.35 kJmol−1 and 92.40 kJmol−1, respectively. Moreover, the average activation energies of EG-20 and EG-30 in the expanding combustion phase were 67.42 kJ·mol−1 and 68.62 kJ·mol−1, respectively. The reaction rate of combustion stage is faster than that of pyrolysis stage. Furthermore, For the combustion, the flame growth index (FGI) of EPDM is greater than that of EG, whereas the flame spread index (FPI) is lower than EG. When EPDM burns, the flame spreads rapidly, while EG expands and generates a large number of wormlike substances, effectively preventing the high temperature from spreading to the interior of the material. Analyses of smoke spreading tests have shown that both EPDM and EG can produce irritating flammable fumes at high temperatures, affecting the environment. These results provide a basis for the development of new materials and contributes to fire safety, smoke management, and personnel escape planning. [ABSTRACT FROM AUTHOR]

• Mechanism of 1,3-C 4 H 6 oxidation with O 2 was studied by quantum chemical calculation1. • 1, 3-C 4 H 6 can be oxidized by O 2 with an important effect on the H radical, reducing the entrance reaction barrier and generating C 2 H 3 CHO through the optimal path. • Due to competition of different pathways, product C 2 H 2 inhibits product C 2 H 3 CHO formation. • A performance assessment analysis found that the updated reaction mechanism can generate better predictions of experimental data than the latest kinetic model. 1,3-Butadiene (1,3-C 4 H 6) is a ubiquitous pollutant produced during the combustion of hydrocarbon fuels in engine cylinders. In this study, we delved into the potential energy surface (PES) and rate constant of 1,3-C 4 H 6 employing the density theory (DFT) method and transition state theory (TST). This study comprehensively clarifies the process of O 2 oxidation 1,3-C 4 H 6 and its significance on the prediction of combustion dynamic models. Our research reveals that the addition of O 2 to the terminal carbon atom of 1,3-C 4 H 6 is the dominant path for addition reactions, leading to the formation of peroxyl radicals. Subsequently, these reactions predominantly yield acrolein and aldehyde groups. Moreover, our data indicates a barrierless and exothermic path for the generation of peroxyl radicals by the O 2 addition to the C 4 H 5 radical site. The energy barrier for the dominant path, 1,3-C 4 H 6 +H → iC 4 H 5 +H 2 , has been calculated to be 57.6 kJ/mol with a rate constant of 7.89×1010 cm3 mol−1 s−1. This study integrates the kinetic and thermochemical data derived from our targeted reaction system into the updated AramcoMech 3.0. An in-depth analysis reveals the capability of this mechanism to simulate combustion characteristics of 1,3-C 4 H 6 , emphasizing its temperature-dependent species profiles. Comparatively, the performance evaluation of the proposed 1,3-C 4 H 6 kinetic mechanism demonstrates its improvement over its predecessor, showing good agreement with experimental results. [ABSTRACT FROM AUTHOR]

This study investigates thermal and combustion kinetics of raw and bio-char samples of eucalyptus wood and bark. Raw samples of eucalyptus wood and bark were subjected to pyrolysis at temperatures of 300, 350, 400, and 450°C. The maximum mass yield was obtained at 350°C for both bio-char samples of wood and bark. Gross calorific value, proximate, ultimate, and chemical analyses of the raw and their derived bio-chars showed high energy yield of bio-chars as compared to raw samples. Thermal analysis of raw and their respective bio-chars was also studied using thermogravimetric analysis in air at heating rates of 25, 35, and 45°C min−1. Raw wood and bark in comparison to their bio-chars showed delayed ignition that resulted in increase of ignition, peak, and burn-out temperatures. Mean reactivity of raw and bio-char samples was obtained using Ghetti model that showed higher reactivity of raw samples than bio-chars. Kinetic parameters including activation energy and order of reaction were found using Arrhenius model. For different heating rates, activation energies lied in the range of 61–108 kJ mol−1 (wood) and 42–79 kJ mol−1 (bark). Higher carbon contents in the bio-char samples resulted in higher activation energies than raw samples. This increasing carbon contents trend also furnished increase activation energies of bio-chars. [ABSTRACT FROM AUTHOR]

In order to prevent the spread of Covid 19, most countries have made face masks compulsory. Millions of face masks are disposed of daily in the community. Therefore, the aim of the present research work is to carry out the pyrolysis and combustion process of the face mask in a thermogravimetric machine. The kinetic parameter activation energy was calculated using model-free methods (Flynn-Wall-Ozawa, Kissinger-Akihara-Sunose, and Starink) at four different heating rates (5, 10, 15, and 20°C/min). Results have shown that face masks decompose in the temperature range of 320–480°C during pyrolysis with a maximum derivative weight loss of 2.5%/°C. Combustion took place between 200°C and 370°C with a maximum derivative weight loss of 1.25%/°C. The residue char at 500°C for pyrolysis and combustion was in the range of 1.74 to 2.73 wt.%. The average activation energies calculated using model-free methods for pyrolysis and combustion were ~135 kJ/mol and ~65 kJ/mol, respectively. In conclusion, combustion process could be the immediate solution to dispose of the face mask due to lower activation energy and decomposition temperature and low emissions as compared to pyrolysis process. [ABSTRACT FROM AUTHOR]

In this study, the effects of particle size on combustion kinetics, mechanisms, and decomposition characteristics of five wood samples were examined using thermogravimetric analysis (TGA) under air atmosphere and three different heating rates (10, 40, and 80 °C/min). By using the both Flynn-Wall-Ozawa and Coats-Redfern methods, the highest activation energies were found to be for the coarse samples except untreated pine samples. Only a few studies in the literature investigated the effect of particle size on both thermal kinetics and responsible mechanisms of solid biomass fuels under oxidative environment. Therefore, the findings can be taken into consideration for highly efficient design and operation of industrial thermochemical processes by using waste lignocellulosic biomass as a fuel. In this study, the average activation energies calculated by Flynn-Wall-Ozawa were 166.57, 153.08, and 171.42 kJ/mol for the smallest, medium and coarse samples, respectively. A similar trend but lower values were also evaluated by Coats-Redfern and it was stated as 131.34, 137.52, 146.22 kJ/mol for the smallest, medium, and coarse samples, respectively. As particle size increased lower combustion performance indexes were also obtained. Therefore, in addition to the particle size, the chemical content of the samples also had an impact on the alteration of the kinetic mechanisms and thermal decomposition properties of the samples. [ABSTRACT FROM AUTHOR]

This work focused on the evaluation of co-combustion of sewage sludge (SS) and rice husk (RH) using thermogravimetric–Fourier transform infrared spectrometry method (TG–FTIR). The thermal behavior was assessed through the combustion characteristic, interaction, kinetics, and gaseous product characteristics. The (co-)combustion process was divided into three stages. Index D exponentially increased as RH blending ratio increased and index S also increased from 10 to 70% RH blending ratio, indicating that the combustion behavior was improved by the RH blending. The activation energy was evaluated by two model-free iso-conversional methods: Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). The minimum value of average activation energy among blends was obtained at sample with 30% RH blending, which was 103.31 kJ/mol by FWO and 97.81 kJ/mol by KAS. Several typical gaseous products and functional groups were detected by FTIR spectrum. The results showed that CO2 was the main volatile and its yield increased with the RH blending ratio. [ABSTRACT FROM AUTHOR]

To explore the influence of CuO additive on the thermal kinetics and combustion performance of thermite, Al/MoO 3 thermite composites with different mass fractions of CuO were prepared by ball milling. Field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and differential scanning calorimeter (DSC) were used to test the samples. From the DSC results, Al/MoO 3 thermite and Al/CuO thermite released 1066 J/g and 849 J/g heat, respectively. The peak temperature of the exothermic reaction was 560.22 °C and 609.43 °C. Interestingly, the Al/MoO 3 thermite with 5% CuO released higher heat, about 1747 J/g. The temperature of the exothermic peak was also greatly advanced to 526 °C. Thermodynamic analysis results showed that the activation energy (Ea) of Al/MoO 3 /5% CuO thermite was merely 184.75 kJ mol−1, which was a decrease of 18.3% and 20.8% of the Al/MoO 3 and Al/CuO thermite. The reaction mechanism function of Al/MoO 3 thermite, Al/MoO 3 /5% CuO and Al/CuO thermite can be set as f (α) = 1 − α. The fast electric heating wire ignition experiment showed that the flame brightness of the Al/MoO 3 /5% CuO thermite was the brightest and the burning time was the longest. Surprisingly, when the mass fraction of CuO additives in Al/MoO 3 thermite reached 10% and 20%, the thermal kinetics and combustion performance of the thermite were completely changed. There was a violent and sharp exothermic peak accompanied by a large amount of heat release of 2042 J/g and 2252 J/g, respectively. The reaction mechanism of Al/MoO 3 thermite with 10% and 20% CuO addition can be set as f (α) = 3 / 2 ∗ (1 − α) [ − ln (1 − α) ] 1 / 3 . The burning speed became faster and the flame was bright with sparks. This work lays the foundation for the further study of the thermite mechanism. [ABSTRACT FROM AUTHOR]

At present, inhibitors have been widely used in the field of coal fire prevention and control, but there are some defects in the use of them. So it is necessary to find a new practical and economical inhibitor. Dissolvable tiny-foam extinguisher (DTE) is environment-friendly, high in thermal stability, and fast in cooling. In view of the good performance of the product, the thermal behavior effects of DTE on coal spontaneous combustion were investigated through experimental tests. A scanning electron microscopy was used to study changes in the surface microstructure of raw coal after DTE treatment. Laser thermal conductivity analysis and simultaneous thermal analysis were used to test the effects of DTE at mass fraction of 0%, 5%, 10%, and 15% on the thermophysical properties, mass loss, characteristic temperature, and heat release of coal during heating. The surface of the DTE-treated coal sample was covered in a dense film. The treated coal sample had lower thermal diffusivity and thermal conductivity values and a higher specific heat capacity. Moreover, coal treated with DTE showed no obvious oxygen absorption or mass gain during initial heating, and the dry cracking temperature was greatly increased by 37 °C, 53 °C, and 100 °C, respectively. The initial heat release temperature increased by more than 170 °C, and the amount of the initial heat absorption was more than 52.2 times that of untreated samples. Oxidation kinetics were applied to calculate the activation energy of the coal during thermal decomposition and ignition, and the activation energies of the treated samples at the thermal decomposition and combustion stages increased by 161%, 179%, and 173%, respectively. From these results, we concluded that DTE could inhibit heat accumulation by blocking oxygen contact with the coal and greatly reducing heat release during heating. Besides, only a small quantity of DTE was needed to effectively inhibit coal self-ignition. These results provide reference for the field application of DTE in restraining coal spontaneous combustion. [ABSTRACT FROM AUTHOR]

Controlling the emission of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) presents a huge challenge in the thermo-chemical conversion of halogenated waste. It is crucial to understand the formation of PBDD/Fs to effectively control their emissions. This paper utilizes density functional theory calculations to comprehensively explore the mechanisms and kinetics of PBDD/Fs formation using 65 polybrominated diphenyl ethers (PBDEs) with varying bromination arrangements and levels. The study uncovers two new pathways for the formation of PBDFs from PBDEs, i.e., two-step H 2 elimination and ether-ketone isomerization at ortho -C(H) sites. These pathways are applicable to PBDEs with specific bromination arrangements. In the case of some PBDEs, their initial energy barriers are comparable to the generally accepted direct HBr elimination. It is found that low-brominated PBDEs have a higher risk of forming PBDD/Fs, while high-brominated PBDEs are more likely to break ether bonds and generate polybromobenzenes. The study also investigates the effects of polymer materials and metals on the formation of PBDD/Fs from PBDEs to explain the high yield of PBDD/Fs in the co-treatment of PBDEs with polymers and metals. The involvement of polymers and metals significantly reduces the energy barriers for the formation of PBDD/F precursors, namely ortho -phenyl-type radicals, accelerating the formation of PBDD/Fs. This study markedly advances the present understanding of the transformation of PBDEs into PBDD/Fs and provides theoretical guidance for reducing pollutant emissions in the thermal treatment and cleaner conversion of PBDE-containing waste. [Display omitted] • 65 PBDE congeners were selected to study the formation mechanism of PBDD/Fs. • A two-step H 2 elimination mechanism for the formation of PBDFs was proposed. • Assess the importance of ether-ketone isomerization reactions at ortho C(H) sites. • Explain the effects of polymers and metals on the formation of PBDD/Fs from PBDEs. [ABSTRACT FROM AUTHOR]

The environmental conditions in the mining region were severely impacted by the high temperature and buried depth of residual coal, which considerably enhanced the likelihood of spontaneous coal combustion and worsened the coal's pyrolysis behavior. Therefore, the change laws of mass and heat during coal oxidation were investigated using industrial analysis and synchronous thermal analysis, and reaction models of coal samples at various phases of oxidation were derived using the Bagchi technique. The findings indicated that the activation energy during the stage of water loss and weight loss increased with the coal's water content, while the activation energy of coal in the early stage of oxidation combustion increased with lower ash percentage and higher carbon content. Additionally, the stages of water loss and weight loss and the stage of oxygen absorption and weight increase in the stable exothermic process of coal samples showed a positive correlation between DTG and DSC. The reaction models for the oxidation and combustion stages were both consistent with the number 7 reaction mechanism. The study's findings may serve as a theoretical roadmap for the further investigation and development of flame retardant avoidance strategies for residual coal oxidation in deep mines. [Display omitted] • Research on quality and heat change during oxidation of residual coal in deep mine. • The relationship between the change of mass and heat in the process of coal oxidation and the activation energy is calculated. • The reaction model of coal samples at different oxidation stages was deduced by Bagchi method. [ABSTRACT FROM AUTHOR]

Pressurized O 2 /H 2 O combustion is a potential CCS technology. In this study, a pressurized horizontal furnace was used to prepare pyrolysis char under pressurized inert atmosphere, and then a pressurized drop tube furnace was used to carry out char combustion under pressurized O 2 /H 2 O atmosphere (5% O 2 , 20% H 2 O) at the same pressure and temperature as the pyrolysis process. The carbon conversion of char under different pressures (0.4/0.7/1.0 MPa), temperatures (900/950/1000 °C), and residence time (1.38/2.76/4.14 s) was studied by proximate analysis. The random pore model was used to calculate reaction kinetic parameters of char combustion at different pressures. The results show that when the pressure increased from 0.4 MPa to 0.7 MPa, the carbon conversion increased significantly, with the increment reaching up to 9.90 percentage points. The marginal diminishing effect became significant when the pressure was greater than 0.7 MPa. The reaction activation energy and pre-exponential factor at 0.4/0.7/1.0 MPa were 66.53/66.29/35.79 kJ/mol and 20.54/36.84/1.69 s−1, respectively. • Pressurization promote carbon conversion of char combustion in O 2 /H 2 O atmosphere. • The promotion of pressurization weakened when pressure was greater than 0.7 MPa. • Activation energy at 0.4/0.7/1.0 MPa was 66.53/66.29/35.79 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

• Function group and structures of oil and SARA fractions were tested by FTIR and NMR. • TG-DSC-FTIR-MS was used to study the thermo-oxidative behavior of heavy oil. • Heating rate has a more significant effect on LTO exothermal compared to mass loss. • Large amounts of CO 2 and aromatic ring were observed in FD and HTC than LTO. • Temperature range of ion current peaks were determined under varying heating rates. To better understand in-situ combustion (ISC) theory and reveal the oxidation behavior and mechanism of Hongqian (HQ) heavy crude oil, the thermo-oxidative characteristics and kinetics of HQ heavy oil were studied under air conditions using TG-DSC-FTIR-MS technique. According to the TG/DTG-DSC curves, the oxidation reactions of HQ heavy oil can be divided into low temperature oxidation (LTO), fuel deposition (FD) and high temperature combustion (HTC) stages. The reaction mechanism for each reaction interval was comprehensively analyzed by online FTIR and MS analysis. In FTIR spectra, H 2 O, hydrocarbon, CO 2 , CO, –COOH, and aromatic ring were observed during the oxidation process, which are used to explain the occurrence of the possible decomposition/isomerization of hydroperoxides in the later stage of LTO and the important role of light hydrocarbons evaporation, thermal oxidative cracking and polycondensation for coke formation at FD stage, coke combustion at HTC stage, as well as the possible hysteresis of dehydrogenation and aromatization at FD and HTC stages. The strong variation of activation energy with conversion degree confirms the complex oxidation reactions. MS analysis of H 2 , CH 4 , H 2 O, CO, O 2 , and CO 2 produced during oxidation process helps to verify these reaction mechanisms; and provide more information about the in-situ H 2 generation and the conditions where H 2 generation may occur as well as the generation of CO and its possible reaction mechanism in LTO reactions. These obtained data aid in a deeper insight into crude oil oxidation mechanism and provide reference for establishing accurate reaction scheme and reaction kinetic model for the precise simulation of ISC processes. [ABSTRACT FROM AUTHOR]