Average Apparent Activation Energy Research Articles

A master plot approach on rice husk decomposition through pyrolysis and kinetic elucidation using iso-conversional models

The present study aimed at predicting the intricate mechanism followed by the pyrolysis of locally available rice husk, uses noval modified master plots through continuous slope-based differential techniques. An average apparent activation energy was found in the range of 187.29 (KAS model) and 199.85 kJ mol−1 (OFW model), respectively. The rice husk revealed higher volatile matter; 54.51 wt-%, HHV; 18.42 MJ kg−1and a critical pyrolysis zone around 250 to 550 °C with two sharp peaks through differential thermogravimetric analysis. Using Karl–Pearson correlation, experimental curve showed highest correlation coefficient of 0.94 and 0.75 with respect to A2 and A3 models (Avrami–Erofeev) for g( α). However, for Z( α), the process is limited by first-order multi-diffusion processes (D1) coupled with solid phase surface reaction (F3) showing correlation coefficient of 0.8. The experimental data worked out the generalized model of f( α) as f( α) = 12.74 α3 – 24 α2 + 12.6 α - 0.92 with R2 value of 0.99, narrating the usage of master plots for better understanding of the process.

Pyrolysis characteristics and kinetic investigation of waste groundnut shells using thermogravimetric analyzer, Py-FTIR, and Py-GC-MS

The objective of the present study was to investigate the bioenergy and resource recovery potential of groundnut shells (GNS) through pyrolysis. The release of vapours at short time scales and their composition were investigated using analytical pyrolysis coupled with Fourier transform infrared (FTIR) spectroscopy and gas chromatography/mass spectrometry (GC/MS). The thermal decomposition behaviour and kinetic evaluation were carried out using a thermogravimetric analyzer (TGA). Five iso-conversional models and master plots method were utilized to explore the kinetic parameters and reaction mechanism at dynamic heating rates (10, 20, and 30 °C min−1). X-ray fluorescence spectroscopy (XRF) was employed to detect the ash composition, which is essential to evaluate the slagging and fouling potential of the biomass when used for bioenergy. TG data revealed three distinct stages of decomposition, while an immense amount of biomass disruption was observed at a higher heating rate (30 °C min−1). Further, the average apparent activation energy of pyrolysis determined using KAS, ST, DAEM, and VZ were 223.26, 214.57, 207.97, and 117.24 kJ mol−1, respectively. The extreme emission of carbon dioxide and carbonyl compounds was discovered through Py-FTIR. The increased formation of hydrocarbons (14.22–34.26%), alcohols (1.41–9.43%), and reduction in phenols (19.13–18.67%) at different temperatures (450, 550, and 650 °C) were validated by Py-GC-MS. Overall, the findings demonstrate that GNS is a promising feedstock for pyrolysis to produce valuable fuel molecules and chemicals.

Oxidation kinetics of typical high FeO ferrous spinels

In this study, the isothermal oxidation kinetics of magnetite (OM), high-Mg magnetite (MM), titanomagnetite (TM), and chromite (CM) were investigated by applying thermogravimetry (TG) analysis at temperatures ranging from 1073 K to 1223 K. The results show that different high-FeO spinels possess distinct oxidizability. The oxidation process of OM in the temperature range from 1073 K to 1223 K is faster than others, followed by MM and TM. While CM exhibits the poorest oxidizability, and generally undergoes complex phase transitions. In the initial stage of oxidation, high FeO spinels have a higher oxidation rate due to the surface oxidation of spinel particles. However, the oxidation rate gradually declines in the later stages of oxidation due to increased internal diffusion resistance. The results of oxidation kinetics indicate that the initial oxidation stage of four spinels can be described as random nucleation and subsequent growth mechanism. The average apparent activation energies of the initial oxidation stage of OM, MM, TM, and CM are 25.09 kJ/mol, 32.39 kJ/mol, 58.10 kJ/mol, and 82.42 kJ/mol, respectively.

Research on the co-combustion characteristics and kinetics of rice husk hydrochar with anthracite

Co-combustion of anthracite and hydrochar derived from hydrothermal carbonization with process water recirculation was proposed as an effective way to achieve a transition to low-carbon energy in industries that rely heavily on coal combustion. In this study, thermogravimetric analysis and model-free methods were employed to investigate the co-combustion characteristics and kinetics of anthracite and hydrochar. The results demonstrate that the carbon content of hydrochar is lower than that of anthracite, but the volatile content is higher than that of anthracite, indicating that hydrochar has better combustion performance. There is a synergistic effect in the co-combustion reaction of hydrochar and anthracite. With the increase of the hydrochar addition ratio, the ignition and burnout temperatures of anthracite decrease gradually. With the increase of temperature rise rate, the combustion reaction is enhanced and the combustion performance of anthracite is improved under the fixed mixing ratio. According to the calculation of combustion activation energy by Flynn-Wall-Ozawa and Kissenger-Akahira-Sunose methods, the apparent activation energy of the mixed samples gradually decreases with the increase of combustion conversion rate. When the addition of hydrochar is 60 %, the average apparent activation energy of the mixed sample is the lowest, which is 66.51 kJ mol−1 and 54.62 kJ mol−1, respectively.

The phase structure, transitions, and non-isothermal crystallization kinetics of Zn2V2O7 glass

The Zn2V2O7 glass was prepared by solid-state reaction using the initial reactant ZnO and V2O5 powder. X-ray diffraction was employed to characterize the phase composition of the as-prepared Zn2V2O7 powder. The crystallization kinetics of Zn2V2O7 glass prepared by solid-state reaction was studied using differential thermal analysis under non-isothermal conditions. It was established that the crystallization process of Zn2V2O7 can be divided into two steps, which is controlled first by a Disc-like with kinetic equation G(α)=[-ln(1-α)]1/3 and then by a Fibril-type growth type with kinetic equation G(α)=[1-(1-α)1/3]1/2 . The apparent activation energy calculated by different methods (Kissinger method, Ozawa method, Tang method, and Starink method) under non-isothermal conditions were similar, varying between 335.6 kJ·mol−1 and 371.6 kJ·mol−1, and the average apparent activation energy was equal to 362.2 kJ·mol−1.

Titanium a novel catalyst and high energy dense material: an opportunity for composite propellants with enhanced performance

ABSTRACT Whereas aluminum with combustion enthalpy of 32 KJ/g is the universal reactive metal particles, its passive protective oxide layer could encounter its efficient combustion. While titanium can offer low combustion enthalpy (20 KJ/g), it does not expose passive oxide layer. The impact of both reactive particles on ammonium perchlorate (AP) decomposition enthalpy was investigated via DSC. Aluminum and titanium particles secured an increase in AP decomposition enthalpy by 46.9%, and 80.7% respectively. This significant impact of titanium particles was ascribed to full exploitation of metal energy content. The impact of titanium particles on AP decomposition kinetics was assessed via Kissinger, KAS, and FWO models using TGA. Whereas virgin AP demonstrated average apparent activation energy of 155 KJ/mol, Ti/AP demonstrated average apparent activation energy of 141.2 KJ/mol. Solid rocket propellant formulations based on 17 wt % metal (Al or Ti) were developed via mixing and vacuum casting. Ballistic performance was investigated using small-scale ballistic evaluation rocket motor. Ti-based formulation offered an increase in propellant burning rate, average operating pressure, average thrust by 18.2%, 26.5%, and 19.7% respectively. It was concluded that titanium particles have a dual effect as efficient high energy dense material and as a catalyst.

Investigation on prospective bioenergy from pyrolysis of macadamia nut shell waste using multicomponent Fraser-Suzuki kinetic model, kinetic triplet and thermodynamic parameters

The investigation of macadamia nut shell waste (MNSW) was conducted to elucidate its bioenergy potential through the analysis of physicochemical properties, kinetic triplet, reaction mechanism models, and thermodynamic parameters. The thermal degradation experiments were carried out using a thermogravimetric analyzer under nitrogen atmosphere at four different heating rates. The multicomponent Fraser-Suzuki kinetic model revealed that the primary decomposition stage could be successfully divided as the parallel devolatilization process of two, three, or four pseudo components. The thermal degradation process of MNSW can be divided into pseudo hemicellulose (PE-H), hemicellulose-lignin (PE-HL), hemicellulose-cellulose (PE-HC), cellulose (PE-C), and lignin (PE-L) employing the multicomponent Fraser-Suzuki kinetic model. The apparent activation energy (E) was calculated using Friedman, Ozawa-Flynn-Wall, Starink, and Kissinger-Akahira-Sunose four model-free methods. The average apparent activation energy calculated through the Starink model-free method was found to be 190.13 and 174.18 kJ/mol for PE-HL and PE-C, 143.79, 169.99, and 249.88 kJ/mol for PE-H, PE-C and PE-L, and 142.98, 157.15, 169.84, and 244.62 kJ/mol for PE-H, PE-HC, PE-C and PE-L, respectively. Evaluation of thermodynamic parameters showed that the pyrolysis process of each pseudo component was an endothermic non-spontaneous reaction independent of surface area and required additional heat and energy input. The pyrolysis process of all pseudo components was accurately characterized using order-based, nucleation, geometrical contraction, power law, and diffusional reaction mechanism models using master plots method. This work provides a theoretical basis for MNSW or other biomass wastes as attractive and environmentally friendly alternatives for bioenergy production, offering crucial insights for reactor design and improving conversion efficiency.

Pyrolysis of macadamia nut peel using multicomponent Gaussian kinetic modeling and ANN analysis

The physicochemical properties of macadamia nut peel (MNP) were explored based on pyrolysis characteristics, kinetics, thermodynamic parameters, reaction mechanism, and artificial neural network (ANN) application to evaluate its suitability and potential for pyrolytic conversion into bioenergy products. Pyrolysis experiments of MNP were performed using a thermogravimetric analyzer in a nitrogen atmosphere. The thermal degradation process of MNP can be successfully modeled into pseudo hemicellulose (PS–H1), cellulose (PS–C2), and lignin (PS-L3) using a multicomponent Gaussian kinetic model with high correlation coefficient (R2 > 0.99). The average apparent activation energy was 179.28 kJ/mol for PS-H1, 192.31 kJ/mol for PS-C2, and 129.42 kJ/mol for PS-L3 using Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang four model-free methods. Master plots method was used to determine the reaction mechanism models of three pseudo components, and the pyrolysis progress can be described well using order-based and nucleation mechanism models. The thermal degradation behaviors of MNP were predicted using artificial neural network, and the best artificial neural network prediction model was ANN (3*15*1). Based on the physicochemical properties, pyrolysis characteristics, kinetics, thermodynamic parameters, reaction mechanism and ANN prediction model, MNP is suitable for pyrolytic conversion into bioenergy products.

Effects of Aqueous Solution and Immersion Duration on Spontaneous Combustion Characteristics of Weakly Caking Coal

ABSTRACT Coal spontaneous combustion (CSC) severely affects the development of the coal industry and threatens the safety of coal miners. This study investigated how immersing coal in aqueous solution affects the CSC risk and evaluated the effect of the immersion duration. Fourier transform infrared spectrometry and thermogravimetric−differential scanning calorimetry analysis were performed. Coal samples were immersed in water from an underground coalmine or in distilled water for 30 or 60 days. Changes in microscopic functional groups and thermokinetic behaviors were determined. Immersion in distilled water for 60 days led to 4.41%, 2.26%, and 6.25% smaller masses of C=O, –CH3, and free hydroxyl groups, respectively, relative to their levels in raw coal. Additionally, the characteristic temperatures T 4 , T 5 , and T 6 were 8.8%, 9.0%, and 9.2% lower, respectively, and the average apparent activation energy was 15.67% lower. Immersion in water from an underground coalmine for 60 days led to 5.68%, 2.58%, and 6.54% higher masses of C=O, –CH3, and free hydroxyl groups, respectively, and 12.8%, 13.0%, and 13.5% higher characteristic temperature, respectively; the average apparent activation energy was 20.43% lower. These findings suggest that the coal immersed in water from an underground coalmine was the most susceptible to CSC.

Pyrolytic characteristics of abutilon stalk waste using TG-FTIR, Py-GC/MS, and artificial neural networks: Kinetics, thermodynamics, and gaseous products distribution

The physicochemical properties of abutilon stalk (ABUS) were investigated to assess its suitability for pyrolytic conversion into bioenergy and bio-based chemicals based on kinetic triplet state, thermodynamic parameters, decomposition mechanisms and product distributions. The pyrolysis behavior of ABUS was studied using a thermogravimetric analyzer at five heating rates in a nitrogen atmosphere. The Gaussian deconvolution function indicated that the pyrolysis process of ABUS can be successfully modeled as four parallel devolatilization events (R2 > 0.99), divided into the devolatilization of pseudo drying (PO-D), hemicellulose (PO-H), cellulose (PO-C), and lignin (PO-L), respectively. The average apparent activation energies were 34.89 kJ/mol for PO-D, 163.02 kJ/mol for PO-H, 169.55 kJ/mol for PO-C, and 107.51 kJ/mol for PO-L using four model-free methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang). The pyrolysis process was accurately predicted using diffusional, power law, geometrical contraction, and order-based reaction mechanism models. Thermal degradation process for each devolatilization event was successfully reconstructed using combined kinetics (R2 > 0.96), providing a useful theoretical basis and mathematical model for predicting the pyrolysis behavior of ABUS. The volatile products produced by ABUS pyrolysis were characterized using an integrated TGA-FTIR and Py-GC/MS system, confirming the proportion of high-energy compounds (benzenes, phenols, ketones, alcohols, aldehydes, acids, esters, hydrocarbons and their derivatives, N-heterocyclic substances, and N-containing compounds) and gas emission levels (CO > CH4 > C-O > H2O > CO2 > CO > C-O(H) > HCN > NH3 > SO2). Artificial neural network (ANN) was used to predict the pyrolysis behaviors of ABUS, and the best ANN model was ANN (5 *11 *1) with high R2 of 0.99998. Based on the kinetics, thermodynamics, and gaseous products distribution, ABUS has great application potential as raw material for bioenergy production.

Deep eutectic solvent assisted swell and highly efficient catalytic pyrolysis of raw coal

The development of catalytic pyrolysis strategy is the key to the efficient utilization of raw coal. Herein, a novel microwave-assisted deep eutectic solvent (DES) swelling strategy was used to catalyze the pyrolysis of Naomaohu coal. The multifunctional FeCl3-Levulinic acid DES was synthesized, it could not only act as the solvent to swell coal, but to highly efficient catalyzed the pyrolysis of the swelled coal. During the process of microwave swelling, DES enhanced the induced polarization of unsaturated bonds, destroyed the weak intermolecular chemical bonds, increased the spacing of aromatic layers and reduced the particle size of raw coal, thus exhibiting a superior swelling effect. Notably, with the catalytic action of DES, it effectively promoted the conversion of coal as well as the escape of light components in the pyrolysis process. Based on the advantages of DES, the pyrolysis tar yield increased significantly (from 11.85% to 17.63%) and the yield of Benzene-Toluene-Xylene was as high as 11.31% in the tar and its content was 14.48 mg g−1. The light component (BP ≤ 360 °C, 67.50%) and light oil (BP ≤ 170 °C, 42.00%) of the tar reached high levels. What’s more, the pyrolysis behavior and kinetics results indicated that the pre-exponential factor was 2.61 × 1016 min−1 and the average apparent activation energy was 267.39 kJ mol−1. The proposed efficient method is expected to provide novel strategy for the swell and catalytic pyrolysis of raw coal using diverse multifunctional DES.

Effects of nano-Al2O3 dosage on pyrolysis kinetics and formation of hydration products in tailings wet shotcrete

The use of tailings as aggregate for the preparation of wet shotcrete is one of the most important technical approaches to the sustainable development of mines. In this study, the pyrolysis kinetics of tailings wet shotcrete with different Nano-Al2O3(NA) dosage and the formation mechanism of hydration products are carried out based on the theory of pyrolysis kinetics and various micro characterization methods. The findings show that 1% NA dosage(NA1) specimen significantly improves uniaxial compressive strength by 48.72% and 34.69% compared to NA0 and NA2, respectively. Pyrolysis of concrete has 3 stages: dehydration of ettringite(AFt) and calcium silicate hydrate(C-S-H), dehydroxylation of calcium hydroxide(CH), and CO2 release from calcium carbonate decomposition. These stages conform to the S-B model. The average apparent activation energy for NA1 specimen during the first pyrolysis stage is 114.01 kJ/mol, indicating an increased energy barrier for the pyrolysis of hydration product, which diminishes when NA dosage exceeds 1%. Furthermore, NA1 specimen exhibits enhanced kinetic parameters, including a notable increase in the preexponential factor during the first pyrolysis stage. This suggests higher activation and effective collision of molecules, leading to optimal AFt and C-S-H formation at 1% NA dosage. Microscopic and thermal analyses reveal that NA aids TWSC hydration through gap filling, nucleation, bond-breaking recombination on tailings surfaces, and calcium (alumino) silicate hydrate(C-(A)-S-H) formation. This process augments hydration product generation, decreases microstructural porosity, and enhances macroscopic strength. However, exceeding 1% NA dosage inversely affects these properties, highlighting an optimal NA concentration for maximizing TWSC performance.

Micro-mesoporous ferrierite obtained using the cationic polymer Luviquat and post-synthesis treatment

This study investigated for the first time the synthesis of ferrierite zeolite through the vapor-phase transport method using the cationic polymer Luviquat as a mesopores-generating agent, followed by desilication treatment. The effect of ferrierite's textural and acid properties was then evaluated in the catalytic cracking of ultra-high molecular weight polyethylene (UHMWPE). The synthesized zeolites showed a crystallinity of 91%–100% and similar Si/Al ratios. After the desilication, there was a decrease in these values along with an increase in acidity, attributable to the extraction of structural silicon. The strong interaction between the polymer and the zeolite precursor during the self-assembly process led to the formation of intracrystalline mesoporosity. However, an internal diffusion limit and/or steric hindrance hinders the complete incorporation of the polymer into the ferrierite structure, especially at high polymer concentrations. Thus, the optimal composition was 40% Luviquat, which resulted in twice the volume of mesopores compared to the sample prepared without the polymer. The desilication of the samples synthesized with the Luviquat led to a substantial increase in mesoporosity, ranging from 67% to 183%, relative to microporous ferrierite. The introduction of mesoporosity and the modification of acid properties in ferrierite contributed to a reduction in the temperature for the cracking of UHMWPE, between 66 and 93 °C compared to the pure polymer. However, in all cases, there was an increase in the average apparent activation energy in relation to desilicated microporous ferrierite zeolite, possibly due to changes in product distribution.

Reduction of chengde vanadium titanium magnetite concentrate by microwave enhanced Ar–H2 atmosphere

In this study, a new method of microwave-enhanced hydrogen reduction was developed to carry out isothermal reduction experiments. The effects and mechanisms of different hydrogen volume fractions on the direct reduction behavior of a vanadium titanium magnetite concentrate (VTM) were investigated. The experimental results and theoretical analysis proved that combining the advantages of microwaves and hydrogen to reduce the VTM is feasible. The thermodynamics of the non-microwave field indicated that the hydrogen reduction of iron titanium oxides was more difficult than that of iron oxides and required a higher reaction temperature. Under microwave heating conditions, with an increase in hydrogen volume fraction, the metallization rate and reduction degree increased, the microscopic morphology developed into a porous sponge-like structure, the size of the internal pores increased, and the migration of metallic iron to the edges of the particles became obvious. When the hydrogen volume fractions exceeded 60%, the products did not contain TiO2, and the final products consisted of metallic iron containing a small amount of dissolved Ti. The reduction reaction was controlled by gas phase diffusion, and the average apparent activation energy was calculated to be 84.05 kJ/mol using a new kinetic model. Moreover, increased hydrogen volume fraction weakened the gas phase diffusion and was converted into internal diffusion.

Hydrogen-rich syngas production and insight into morphology-kinetics correlation for furfural residue steam gasification in a bubbling fluidized bed

Biomass steam gasification technology has attracted considerable interest for its potential of low-cost and high-efficiency in hydrogen production. However, there is still a large knowledge gap regarding morphology-kinetic correlation. To avoid the technical difficulties of thermogravimetric analysis and fixed bed studying steam gasification kinetics, this work pursues the design and building of a visualized bubbling fluidized bed with an online analysis system. According to the morphology evolution of biomass real-time observed by a high-speed camera, the shrinkage ratio during high-temperature gasification in a fluidized bed has been first deduced. Moreover, based on accurate monitoring of the gas products releasing behavior, multiple kinetic models were applied to evolve the activation energy at different carbon conversion efficiencies (CCE). The results showed that the synergistic regulation of steam concentration and temperature achieved a high H2/CO ratio (2.46) and H2 yield (869.5 L/kg). A comparative analysis of the coupling relationship between shrinkage ratio, activation energy and CCE successfully separated the volatile precipitation and char gasification processes. It was also revealed that the shrinkage rate peaked at the transition from pyrolysis to char gasification (20 % CCE). At CCE below 20 %, the reaction mechanism tended towards a nucleation and growth mechanism. As CCE reached 20 %, the reaction form shifted. Subsequently, the chemical reaction mechanism controlled the main reaction, and the average apparent activation energies of H2, CO2 and CO were 86.76, 31.27 and 39.90 kJ/mol, respectively. This work provides new insights and a theoretical basis for understanding and modeling the biomass steam gasification process in fluidized beds.

Isothermal reduction and nitridation kinetics of ilmenite concentrate in ammonia gas

Low-temperature chlorination is considered a suitable process for ilmenite containing high contents of MgO and CaO. However, reduction carbonization or nitridation is essential to convert titanium oxide to carbide or nitride, which can be enriched by magnetic separation. In this paper, the isothermal reduction–nitridation kinetics of Panzhihua ilmenite concentrate in an ammonia atmosphere was investigated. Both model–free and model–fitting methods were used to compare the isothermal kinetics. The reaction process can be divided into two successive stages: the reduction reaction and the nitridation reaction. The average apparent activation energy for the reduction reaction was 139.63 kJ/mol, obtained by the model–free method. The reduction process can also be subdivided into two stages by the model–fitting method. The chemical reaction (G(α) = 1–(1–α)1/3 = kt) and three–dimensional diffusion (G(α) = [1–(1–α)1/3]2 = kt) were identified as the mechanism function for the reduction process. The activation energies of these two stages were 121.73 kJ/mol and 141.40 kJ/mol, respectively. The function G(α) = 1–(1–α)1/3 = kt, which also corresponds to the chemical reaction mechanism (R3), exhibited the best fit for the nitridation stage. The corresponding activation energy was 32.10 kJ/mol. Metallic iron and Ti3O5 were formed in the reduction stage, while Ti3O5 was then transformed to Ti(N,O) in the nitridation stage.

Study of inflatable temperature–sensitive hydrogel to prevent the coal spontaneous combustion

A serious of inflatable temperature–sensitive hydrogel (HPMC–CS–EM) were prepared to prevent coal spontaneous combustion (CSC). Through performance tests, it was found that gel of 50 mPa∙s HPMC had good fluidity, the addition of EM can increase the water loss in the early pyrolysis stage. A50, B50 prepared by 50 mPa∙s HPMC and 0 %, 0.5 % EM had good performance which were suitable for the prevention of CSC. The inhibition of A50, B50 on CSC was tested by means of paramagnetic resonance spectroscopy and thermogravimetry. Inhibition experiments revealed that more water and hydrocarbon gas were released from B50 gel, thereby significantly reducing the concentration and amount of free radicals, the maximum water loss rate temperature and the dry crack temperature. The more carbon residue of A50 gel made it have better inhibition effect in the slow oxidation stage. The average apparent activation energy was obtained by the combination of universal integral and differential at multiple heating rates, indicating that these two gels remarkably reduced the tendency of CSC.

Effect of magnetite addition to ilmenite on hydrogen-rich reduction of its oxidized powder

In this study, the oxidation powder sample of ilmenite concentrate with 15% magnetite concentrate was prepared, and the subsequent isothermal reduction was investigated at temperatures in the range of 950–1050 °C with CO, H2, and their mixtures. The hydrogen-rich atmosphere, magnetite effect, apparent activation energy, and micromorphology of the reduced samples were investigated. The results indicated that the mass loss of the raw sample in the reduction process exhibited a similar tendency to that of the preoxidized ilmenite concentrate, although the addition of the magnetite concentrate increased the total mass loss. The influence of Fe2O3, which is produced by the oxidation of magnetite, on the mass-change ratio in the reduction process is separated and drawn novelty. The interaction between the magnetite and ilmenite concentrates in the oxidation process did not exhibit an apparent hindering effect following the hydrogen-rich reduction of the raw sample powder. The reducing atmosphere had a slight influence on the average apparent activation energy. The average apparent activation energies of the reduction of the raw sample were 55.34, 53.54, 52.78, 59.14, and 53.85 kJ/mol when the reducing atmosphere was CO, H2/CO = 0.4, H2/CO = 1, H2/CO = 2.5, and H2, respectively. Furthermore, the change in micromorphology of the reduced sample with the hydrogen-rich content in the reduction atmosphere is also discussed.

Investigation of thermodynamic and kinetic parameters of Albizia lebbeck seed pods using thermogravimetric analysis

Thermodynamic and kinetic studies are very necessary to evaluate the conversion efficiency of biomass to energy. Therefore, this current work reported the thermodynamic and kinetic parameters of Albizia lebbeck seed pods through thermogravimetric analysis, which was carried out at temperatures from 25 °C to 700 °C, and heating rates of 5, 10, 15, and 20 °C/min. Apparent activation energies were determined by applying three iso-conversional model-free methods including Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), and Starink. Resultantly, average apparent activation energy values for the three models of KAS, OFW, and Starink were found to be 155.29, 156.14, and 155.53 kJ/mol, respectively. In addition, thermodynamic triplets such as enthalpy, Gibbs free energy, and entropy were obtained as 151.16 kJ/mol, 150.64 kJ/mol, and −7.57 J/mol·K, respectively. The above results suggest Albizia lebbeck seed pods could become a potential source for bioenergy production aiming to achieve the sustainable goal and waste-to-energy strategy.

Comprehensive assessment of thermal characteristics, kinetics and environmental impacts of municipal solid waste incineration fly ash during thermal treatment

The volatilization of heavy metals and the release of harmful gases during the thermal treatment of municipal solid waste incineration (MSWI) fly ash (FA) can cause secondary pollution. Understanding the thermal characteristics, heavy metal behaviors and environmental emissions in FA roasting is significant for pollution control and heavy metal elimination. In this work, the thermodynamics, kinetics, environmental impacts, carbon emission, phase transition, leaching toxicity, transition behavior of chlorine and heavy metals in FA thermal treatment were investigated comprehensively for the first time through TG-FTIR, XRD, ICP-OES and IC. The apparent activation energy and thermodynamic parameters were obtained according to the kinetic modeling method. The average apparent activation energy values of the first, second, third, and fourth stages were 60.21, 114.91, 190.23, and 226.67 kJ/mol, respectively, and the reaction control models were chemical reaction model (No.3), assumed random nucleation and subsequent growth model (No.21), assumed random nucleation and subsequent growth model (No.14), and nucleation model (No.10). The environmental impacts illustrate that large amounts of gaseous products, including CO2, H2O, NO and SO2, are released during the thermal treatment of FA, and the emission of CO2 sharply increases as the temperature exceeds 550 °C. When treating 1 kg of FA at 1000 °C, the release of CO2 in stages I, II, III and IV is 0.18, 7.06, 116.34 and 177.21 g, respectively, and the total carbon emission is approximately 300 g. The leaching toxicity of heavy metals in FA is higher below 800 °C, and it is mainly caused by Pb. In addition, the volatilization rate of heavy metals and chlorine increased significantly as the calcination temperature exceeded 800 °C, among which, the volatilization rates of Pb, Cu, and Cl can reach 99.87%, 90.25% and 73.85%, respectively. At high temperatures, heavy metals in FA exist primarily in oxidizable and residual states. The obtained findings can provide theoretical guidance for pollution control and process optimization of FA thermal treatment.