Flynn Wall Ozawa Method Research Articles

Different Methods for Calculation of Activation Energies During Non-Isothermal Annealing of Mg72Zn27Pt1 and Mg72Zn27Cu1 Metallic Glasses

Mg72Zn27Pt1 and Mg72Zn27Cu1 metallic glasses were produced using a melt-spinner. Their crystallization kinetics were investigated during annealing with five heating rates using DSC. Amorphous Mg72Zn27Pt1 crystallized in the form of one and Mg72Zn27Cu1 crystallized in the form of two exothermic crystallization peaks. It was noticed that the glass transition, the onset crystallization and the crystallization peak temperatures were strongly heating-rate-dependent. The addition of Pt and Cu increased the stability compared to that of binary Mg-Zn glass, and especially so with Pt, due to its higher melting point and different atom size to those of Mg and Zn. The activation energies were calculated using six model-free methods: the Kissinger, Ozawa–Flynn–Wall, Boswell, Tang, Augis–Bennett and Gao–Wang methods. The Augis–Bennett and Gao–Wang methods allow for the calculation of only the activation energy at the crystallization peak but they are the only ones that consider Tx or dx/dT. For Mg72Zn27Pt1, the calculated values fluctuate in the ranges 114.60–117.99 kJ/mol, 102.46–105.98 kJ/mol and 71.16–98.62 kJ/mol for Eg, Ex and Ep, respectively, whereas, for Mg72Zn27Cu1, the calculated values are in the ranges of 98.51–101.77 kJ/mol, 95.15–98.51 kJ/mol and 55.15–93.34 kJ/mol for Eg, Ex and Ep, respectively. Both alloys are meta-stable in the amorphous state and crystallization occurs spontaneously. The Kissinger, Ozawa–Flynn–Wall, Tang and Boswell methods give similar values for the activation energy. The Gao–Wang method significantly underestimates values compared to other methods. The Augis–Bennett method shows much lower values for the local activation energy. Considering the ease of their formulas, best convergence and widespread use in the literature, the Kissinger and Ozawa–Flynn–Wall methods will work very well for any comparison.

Thermal Decomposition Kinetics Analysis and Its Application to Cigarette Flavouring of Methyl Cyclopentenolone Succinate Menthol Diester

ABSTRACTMethyl cyclopentenolone succinate menthol diester (compound 5) was synthesised from methyl cyclopentenolone, menthol and succinic anhydride using dicyclohexylcarbodiimide (DCC) and 4‐dimethylaminopyridine (DMAP) methods. The thermal decomposition process and kinetic behaviour of the compounds were studied at various heating rates (10°C, 20°C, 40°C, 60°C and 80°C min−1) using thermogravimetry‐derivative thermogravimetry (TG‐DTG), Kissinger‐Akahira‐Sunose (KAS) method, Flynn‐Wall‐Ozawa (FWO) method and Coats–Redfern method. The research revealed that TG curves approached the high‐temperature end with increasing heating rates, and the peak temperature of heat loss rate on the DTG curves tended to rise, but the magnitude of the change was smaller than that of heating rate. The apparent activation energy (Ea) of thermal decomposition increased with the conversion rate. The Ea of compound 5 ranged from 77.65 to 154.05 kJ mol−1 and from 82.56 to 156.43 kJ mol−1 calculated by KAS and FWO, respectively. The thermal decomposition process models of the compounds were found to be one‐dimensional diffusion models (D1). The results of the kinetic compensation effect showed that the fitting result of the KAS method was better than that of the FWO method. Pyrolysis results indicated the production of aromatic substances such as methyl cyclopentenolone, menthol and esters. Additionally, the results of cigarette flavouring showed that the smoking quality of cigarettes was improved by adding compound 5. In summary, the findings of this study not only offer insights into the thermal decomposition and development of slow‐release flavours under heated conditions, but also provide valuable references for assessing the thermal stability and utilisation potential of various substances, including biomass.

Thermoanalytical and Kinetic Studies for the Thermal Stability of Emerging Pharmaceutical Pollutants Under Different Heating Rates.

Emerging pharmaceutical pollutants like ciprofloxacin (CIP) and ibuprofen (IBU) are frequently detected in aquatic environments, posing risks to ecosystems and human health. Since pollutants rarely exist alone in the environment, understanding the thermal stability and degradation kinetics of these compounds, especially in mixtures, is crucial for developing effective removal strategies. This study therefore investigates the thermal stability and degradation kinetics of CIP and IBU, under different heating rates. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were employed to examine the thermal behavior of these compounds individually and in mixture (CIP + IBU) at heating rates of 10, 20, and 30 °C/min. The kinetics of thermal degradation were analyzed using both model-fitting (Coats-Redfern (CR)) and model-free (Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Friedman (FR)) methods. The results showed distinct degradation patterns, with CIP decomposing between 280 and 550 °C and IBU between 152 and 350 °C, while the mixture exhibited multistep decomposition in the 157-500 °C range. The CR model indicated first-order kinetics as a better fit for the degradation (except for IBU). Furthermore, CIP exhibits higher thermal stability and activation energy compared to IBU, with the KAS model yielding activation energies of 58.09 kJ/mol for CIP, 11.37 kJ/mol for IBU, and 41.09 kJ/mol for CIP + IBU mixture. The CIP + IBU mixture generally showed intermediate thermal properties, suggesting synergistic and antagonistic interactions between the compounds. Thermodynamic parameters (ΔH°, ΔG°, ΔS°) were calculated, revealing non-spontaneous, endothermic processes for all samples (except in the FWO method) with a decrease in molecular disorder and positive ΔG° values across all models and heating rates. The study found that higher heating rates led to less thermodynamically favorable conditions for degradation. These findings provide important information concerning the thermal behavior of these pharmaceutical pollutants, which can inform strategies for their removal from the environment and the development of more effective waste-treatment processes.

Effect of fullerene (C70) on the structural, morphological optical and thermal properties of poly(butyl methacrylate) (PBMA)

Poly(butyl methacrylate) (PBMA)/Fullerene (C70) nanocomposites were successfully prepared by solvent removal method and characterized by different techniques. Structural characterization showed an interaction between PBMA and C70 nanofiller. Morphological features showed that C70 was homogeneously distributed in the PBMA matrix. Optical analysis confirmed the formation of nanocomposites with wavelength shift in PBMA/C70 nanocomposites compared to pure PBMA. Photoluminescence spectra showed that the emission bands of PBMA/C70 nanocomposites shifted from blue to red and the presence of new emission spectra in the red region. The data obtained from thermal analysis showed that the Tg of the nanocomposites increased by about 10 °C compared to pure PBMA and the maximum decomposition temperatures improved by about 65–70 °C, confirming the increased thermal stability. The data obtained from thermogravimetric analyses performed at different heating rates were analyzed by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) equations to calculate the activation energy values. According to the regression coefficient values, the experimental results were in good agreement with the FWO method (R2 PBMA=0.937 and R2 PBMA/C70 (5 wt%)=0.953). The activation energy of PBMA and fullerene doped nanocomposite were calculated as 48 kJ/mol and 104 kJ/mol, respectively and the results showed that the Ea value of nanocomposite was higher than PBMA.

Kinetic analysis of coal oxidative pyrolysis before and after immersion effect

The oxidative pyrolysis kinetics of coal before and after immersion effect was studied by thermogravimetric experiments. Non-isothermal thermogravimetric analysis data were analyzed at four heating rates of 5, 10, 20 and 30 K/min. Furthermore, temperature-programmed experiments and Fourier-transform infrared (FTIR) spectroscopy were employed to understand the oxidation activity and chemical structure of raw coal and soaked coal. After coal immersion effect, the increase in the content of active functional groups, the increase in the concentration of gaseous products, and the decrease in crossing point temperature during oxidation process all indicate that soaked coal is easier to oxidize and spontaneously combust. Lastly, four model-free methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman and Kissinger methods are employed to calculate the activation energy (Eα). Kinetic analysis reveals that Eα value obtained by the former three methods significantly depends on the conversion of coal oxidative pyrolysis process, and the average Eα value of soaked coal obtained by four methods is lower than that of raw coal. For the kinetic analysis of coal oxygen adsorption and combustion stages, it is more reliable to adopt the FWO and KAS methods in turn. This research helps to better understand the mechanism of enhanced oxidation activity of soaked coal and optimizes the calculation method of kinetic parameters in different oxidation stages of coal.

Study on Thermal Oxygen Aging Characteristics and Degradation Kinetics of PMR350 Resin.

The thermal stability and aging kinetics of polyimides have garnered significant research attention. As a newly developed class of high thermal stability polyimide, the thermal aging characteristics and degradation kinetics of phenylene-capped polyimide prepolymer (PMR350) have not yet been reported. In this article, the thermo-oxidative stability of PMR350 was investigated systematically. The thermal degradation kinetics of PMR350 resin under different atmospheres were also analyzed using the Flynn-Wall-Ozawa method, the Kissinger-Akahira-Sunose method, and the Friedman method. Thermogravimetric analysis (TGA) results revealed that the 5% thermal decomposition temperature (Td5%) of PMR350 in a nitrogen atmosphere was 29 °C higher than that in air, and the maximum thermal degradation rate was 0.0025%/°C, which is only one-seventh of that observed in air. Isothermal oxidative aging results indicated that the weight loss rate of PMR350 and the time-dependence relationship follow a first-order exponential growth function. PMR350 resin thermal decomposition reaction under air atmosphere includes one stage, with a degradation activation energy of approximately 57 kJ/mol. The reaction model g(α) fits the F2 model, and the integral form is given by g(α) = 1/(1 - α). In contrast, the thermal decomposition reaction under a nitrogen atmosphere consists of two stages, with degradation activation energies of 240 kJ/mol and 200 kJ/mol, respectively. The reaction models g(α) correspond to the A2 and D3 models, with the integral forms represented as g(α) = [-ln(1 - α)]2 and g(α) = [1 - (1 - α)1/3]2 due to the oxygen accelerating thermal degradation from multiple perspectives. Moreover, PMR350 resin maintained high hardness and modulus even after thermal aging at 350 °C for 300 h. The results indicate that the resin exhibits excellent resistance to thermal and oxygen aging. This study represents the first systematic analysis of the thermal stability characteristics of PMR350 resin, offering essential theoretical insights and data support for understanding the mechanisms of thermal stability modification in PMR350 and its engineering applications.

Investigation of thermal properties and structural characterization of novel boron-containing Schiff base polymers

Three novel Schiff base polymers were synthesized by using the Schiff base monomer obtained using aldehyde containing boric acid and amines containing hydroxyl groups as the starting materials. The polymers were synthesized at the same temperature and using the same amount of oxidizing agent by the oxidative polycondensation method. The characterization of all polymers and monomers was achieved by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), nuclear magnetic resonance spectroscopy (1H-NMR), liquid chromatography-mass spectrometry (LC–MS), gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The thermal stability of these compounds was studied by employing thermogravimetric analysis (TGA), and thermodynamics parameters such as activation energy (Ea), enthalpy (∆H), entropy (∆S), and Gibbs free energy(∆G) for the decomposition process were calculated using the Flynn–Wall–Ozawa method.

Pyrolysis of metal oxides treated Canarium schweinfurthii Shell: Investigation of thermogravimetric kinetics and thermodynamics

Metal oxides as catalysts alter the properties of the pyrolysis vapor secondary reactions during the thermal decomposition of several biomass leading to high-value bio-oils. This study aimed to investigate the thermal decomposition characteristics of Canarium Schweinfurthii (CS) shells that were treated with various metal oxides (ZnO, CuO, Fe2O3/FeO, and Fe2O3) using pyrolysis. The study also sought to identify pyrolysis reaction parameters (kinetics and thermodynamics parameters) that are not widely documented. Thermogravimetric pyrolysis was carried out at different heating rates, and the undocumented pyrolysis kinetic parameters were determined using the Flynn-Wall Ozawa method (FWO) according to American Standard Testing and Materials (ASTM) 6441 guidelines for assessing biomass decomposition. The metal oxide-treated CS shells lost significant weight between 62 and 67 wt% during the thermogravimetric pyrolysis, lower than 75 wt% of the CS shell. The average activation energies (Eα) for pyrolysis of the ZnO, CuO, Fe2O3/FeO, and Fe2O3 treated CS shells were 203.04, 155.35, 338.85, and 219.92 kJ/mol, respectively in contrast to that of the untreated CS-shell. The Bayesian Information Criteria revealed that the diffusion kinetics of the Gistling-Brounshtein model best describes the pyrolysis of the shell mixed with metal oxides. The metal oxides affected the CS shells' pyrolysis kinetic parameter (Eα), which can promote pyrolysis vapor upgrading to encourage the widespread use of metal oxides in pyrolysis for bioenergy and chemical recovery.

Pyrolysis behavior of densified refuse-derived fuels (d-RDFs) via TGA: Investigating the impact of densification degree on thermal kinetics and thermodynamics

The conversion of municipal solid waste (MSW) into its energy-rich fraction, known as refuse derived fuel (RDF), addresses both MSW management and energy demand. RDF comprises a diverse blend of various non-hazardous waste streams, making it challenging to predict physical properties and chemical compositions. However, densification can help overcome these challenges. This work aims to explore the effect of densification degree on kinetic and thermodynamic parameters during the degradation of densified refuse-derived fuels (d-RDFs) in inert atmosphere. Herein, three d-RDFs samples obtained with varying degree of densification and die temperatures ranging from 55 °C to 118 °C, as well as a mixed fines (MF) sample produced during the pelletization process, were analyzed. Pyrolysis potential of d-RDFs and MF were determined using thermogravimetric analysis in the temperature range from 30 to 800 °C, at multiple heating rates of 5, 10, and 20 K min−1. The effect of the degree of densification on physical characteristics, and kinetic and thermodynamic parameters of d-RDF was investigated. Apparent activation energy (Eα) was estimated employing Friedman (FR), Kissinger-Akahera-Sunnose (KAS), and Flynn-Wall-Ozawa (FWO) methods. Derived Eα values were used to determine the pre-exponential factor (Aα) using the Kissinger method. Experimental results revealed that the durability of d-RDFs increased from 79.26 % to 98.73 % as the densification degree increased from II to IX. Furthermore, the Eα values exhibited a decreasing trend in the first peaks of the DTG profiles, while an opposite trend was observed in the second peaks of DTG curves. However, with an increase in the degree of densification, the mean values of Eα decreased by 5–10 % for all methods. The Aα values, assessed using the FR method, surpassed the critical value of (109 s−1) for all samples. However, with the KAS and FWO methods, these values fell below (109 s−1) within the conversion range of 0.05–0.25. Thermodynamic parameters confirmed the endothermicity of the thermal degradation process.

A kinetics study of microwave pyrolysis of sewage sludge and corn stalk mixture

AbstractFast pyrolysis of sewage sludge (SS), corn stalk (CS), and their mixture under both direct and indirect microwave heating was carried out in a prototype microwave thermogravimetric reactor at high heating rates, 179 and 203 K/min, respectively. It was found that the samples could be heated up rapidly by direct microwave heating, while there is a temperature lag of the sample to the heated reactor wall in indirect heating. The Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods were used to analyze the thermogravimetric data of SS, CS, and their mixture under direct microwave heating. When the FWO method was used, the average activation energies of SS, CS, and their mixture were obtained as 6.0, 18.9, and 39.8 kJ/mol, respectively. When the KAS method was used, the average activation energies of CS and mixture were 12.6 and 31.6 kJ/mol, respectively. Those values are much lower than reported under conventional heating, and likely result from the interaction of microwave irradiation and the biomass samples. The reaction kinetics of directly microwave‐heated biomass pyrolysis from this study provide essential data for modelling, scaling, and designing the microwave‐assisted in‐situ catalytic pyrolysis reactors with mixed biomass and catalyst particles.

Thermal and calorimetric investigations of some vegetative fuels

AbstractBushfires pose a significant threat to numerous countries, often causing vast property damages and loss of lives. Efforts to combat and manage these fires heavily rely on predicting the fires' rate of spread and intensity. A significant component of these predictions involves understanding the thermophysical characteristics of vegetative fuels. The accuracy of predictive models (especially physical models) also depends on obtaining precise thermophysical and combustion parameters. This research aims to provide a comprehensive set of thermal degradation and combustion parameters for surface and near‐surface fuel samples collected during prescribed fire experiment conducted in April 2022 in Little Desert National Park, Victoria, Australia. Firstly, fuel properties like fuel height, moisture content, bulk density, fuel load and heat of combustion were meticulously characterized for both surface and near‐surface samples. Then activation energies for degradation reactions were determined using the Flynn–Wall–Ozawa method and for the determination of pre‐exponential factors, in most cases these reactions closely aligned with a Second order model. This was followed by determination of other parameters such as heat of reaction, specific heat and conductivity. It was found that the density, activation energy and heat of combustion did not vary significantly across the six samples under question. The comprehensive set of obtained parameters will likely help to facilitate better predictions in fire propagation modelling.

Comprehensive investigation of almond shells pyrolysis using advance predictive models

This research focused on comprehensive characterization and assessment of almond shells pyrolysis for bioenergy potential through thermogravimetric analysis from ambient temperature to 900 °C at different heating rates of 10, 15, and 20 °C/min in inert environment. Iso-conversional model-free methods like Friedman, Ozawa-Flynn-Wall (OFW), and Kissinger-Akahira-Sunose (KAS) were used for kinetic analysis. Average activation energies (Ea) evaluated using Friedman, OFW, and KAS methods were 198.45 kJ mol−1, 204.43 kJ mol−1, and 204.97 kJ mol−1, respectively. The evaluation of thermodynamic parameters, including ΔH‡, ΔG‡, and ΔS‡, was also assessed. The average values of ΔH‡, ΔG‡, and ΔS‡, were found to be 199.4 kJ mol−1, 172.17 kJ mol−1 and 42.60 kJ mol−1 respectively. The reaction mechanism was obtained from combined kinetics. A high R2 value of 0.9933 demonstrates strong agreement between the combined kinetic analysis results and the experimental data. The distribution activation energy model was assessed employing four pseudo elements identified as PC1, PC2, PC3, and PC4. Artificial Neural Network (ANN) and Boosting regression trees (BRT) were used for the prediction of Ea of almond shells pyrolysis. The detailed understanding of thermokinetics and creating customized predictive and innovative modelling techniques like ANN and BRT sets a new benchmark for developing customized models for thermochemical conversion of varieties of almond shells.

Porous‐structured vermiculite/polybutylene adipate terephthalate composite films: The morphology, mechanical properties, and nonisothermal degradation kinetics

AbstractTo examine the impact of vermiculite (VMT) on the environmental and physical aspects of polybutylene terephthalate (PBAT), the thermal degradation behavior of VMT/polybutylene terephthalate polyadipate (VMT/PBAT) composite films was investigated by using the thermogravimetric analysis (TGA). To ensure precise calculation of the specific activation energy values of VMT/PBAT composite films in thermal degradation performance experiments, the Kissinger method (K‐method) and Flynn–Wall–Ozawa method (FWO method) were utilized. Additionally, the reaction mechanism was analyzed using the Coats–Redfern equation (CR equation). The introduction of VMT into the PBAT co‐polyester structure leads to an increase in the thermal degradation activation energy Ek of composite films.; the apparent activation energies were calculated by the Coats–Redfern method for different reaction mechanisms, and the interfacial diffusion reaction mechanism of the composite film was determined, with a thermal degradation reaction principle properties of g(α) = [1 − (1 − α)]2 and the number of reaction steps of 2.Highlights VMT/PBAT composite films prepared using a simple method. Analyzing nonisothermal degradation kinetics using K‐method and FWO method. Analyzing the degradation mechanisms using the Coats–Redfern equation. Addition of VMT enhances the thermal degradation properties of composite films. Addition of VMT reduces the mechanical properties of the composite film.

Investigation of Thermal Degradation Properties and Chemical Kinetic Characteristics of Biomass Pyrolysis via TG/DTG and FTIR Techniques: Sesame Stalks as Potential Source of Bioenergy in Ethiopia

The dependence on fossil fuels and the overexploitation of it is a bottlenecked problem of the globe leading to finding alternative renewable resources that may be used as an energy source in place of fossil fuels. Thermogravimetric analysis (TGA) is a technique used to identify potential renewable energy sources. This study investigated the kinetic, thermodynamic parameters, and pyrolysis characteristics of sesame stalk (SS) biomass pyrolysis using thermogravimetric (%) (TG)‐derivative thermogravimetry (DTG) techniques. The pyrolysis was carried out at different heating rates (15, 20, and 25°C/min). The chemical kinetics parameters were determined using isoconversional model‐free methods, including Kissinger–Akahira–Sunose (KAS), the Ozawa–Flynn–Wall (OFW), and model fitting techniques like the Coats–Redfern (CR) model. The thermodynamic parameters (∆H, ∆G, and ∆S) were calculated using kinetic data. The average activation energy for SS biomass was found to be 77.96 and 84.15 kJ/mole for the KAS and OFW methods, respectively. The activation energy (E) for SS biomass from the integral method varied between 29.61–142.58 kJ/mole for reaction order models and 4.90–122.33 kJ/mole for diffusion models. The distributions of pre‐exponential factor (A) for the reaction order models are virtually normal in the range of 0.2–0.7, upon the Eα values obtained using the OFW and KAS approach. The average value of enthalpy, Gibbs free energy, and entropy of SS were also reported. The study suggests that SSs are a potential biomass for sustainable bioenergy production, and kinetic and thermodynamic data are crucial for reactor design for the pyrolysis of SSs.

Co-combustion characteristics and kinetics of sludge/coal blends in 21%–50% oxygen-enriched O2/CO2 atmospheres

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 (O2/N2 = 21/79 by volume), oxy-fuel combustion (O2/CO2 = 21/79, 25/75, 35/65, and 50/50 by volume), and pyrolysis (pure N2 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.

Research on the characteristics of pressured pyrolysis products of marine plastics

The problem of marine plastic pollution, mainly composed of polyolefin plastics, is becoming increasingly serious, and reducing marine plastic pollution is urgent. Pyrolysis, as a promising technology for treating polyolefin plastics such as polystyrene (PS), has great potential in addressing marine plastic pollution issues. In order to explore the possibility of resource utilization of marine plastics, this article studied the effect of pressure changes on the pyrolysis products of marine plastics. Marine PS was prepared by soaking routine PS in artificial seawater and air drying, and the most significant difference between the two was found to be the salt attached to the surface. The dynamic characteristics of marine PS were analyzed using Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, and the apparent activation energy of marine PS calculated by FWO and KAS methods are 102.94 kJ·mol−1 and 95.76 kJ·mol−1, respectively. The effect of pressure at different temperatures on the pyrolysis products of marine PS was studied. The results indicate that the yield of pyrolysis oil decreases as the pressure is increased, while solid products are obtained from scratch. The increase in pressure will gradually make the composition of the thermolytic gas become monotonous. Under critical pressure, pressurization promotes an increase in CH4 content while reducing H2 content, causing the lower heating value of pyrolysis gas to increase to 4.355 kJ·g−1. Analysis of oil content found that increasing pressure promotes the growth of Benzene Toluene Ethylbenzene & Xylene (BTEX) to 33.61%, but excessive pressure can significantly reduce the higher heating value from 42.116 MJ·kg−1 to 31.825 MJ·kg−1. The solid products were characterized using FTIR and it was found that pressure did not have a significant impact on surface functional groups. Increasing the pressure properly promotes the agglomeration of amorphous carbon.

Thermal degradation kinetics, thermodynamics and pyrolysis behaviour of polycarbonate by TGA and Py-GC/MS

This paper elucidates the thermal and catalytic (mordenite and y-zeolite) pyrolysis characteristics of Polycarbonate (PC) as well the kinetics and thermodynamic parameters of the thermal decomposition of PC. Three distinct isoconversional methods, namely the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starkin methods, were employed to evaluate the kinetic and thermodynamic parameters. The average activation energies determined with the KAS, FWO, and Starink methods were 245.81, 235.36, and 249.99 kJ/mol respectively, and they were reduced by 17 % and 21 % when mordenite and y-zeolite were utilized as catalysts, respectively, according to the calculations performed with the KAS method. Py-GC/MS analyses showed that phenolic components were found to be dominant in the oil product obtained under non-catalytic conditions. Micropores in the structure of y-zeolite constitute 54.4 % of the total surface area, while micropores in the structure of mordenite constitute 95.5 % of the total surface area. Depending on the structure of the catalysts used, phenolic components decreased slightly, and aromatic and PAH (Polycyclic Aromatic Hydrocarbons) components replaced these components. As a result, phenolic compounds in the oil product obtained with y-zeolite (56.7 %) were less than those produced with mordenite (61.02 %). PAHs were 12.9 % and 7.5 % in the presence of y-zeolite and mordenite, respectively. Thus, the results evidence the molecular size of zeolite catalysts, as well as their acidic structure, which are crucial factors in the conversion of phenolic compounds.

Effect of sludge-based suppression materials on the explosive flame characteristics of aluminium dust

A study was conducted to investigate the inhibitory effect of sludge-based phosphate-containing composite powder explosion suppressants (MPP/AMS) on aluminium dust explosion and combustion. The experiment compared the inhibition characteristics of ordinary sewage sludge particles, high-temperature alkali-modified sludge particles, phosphate-containing particles, and phosphate-modified sludge particles. The study utilized a flame propagation experimental device and an explosion pressure testing device for comprehensive research. The experimental recording devices revealed that sludge-based composite powder explosion suppressants effectively inhibit aluminium powder explosion and combustion. Thermodynamic analysis of the rapid oxidation stage was performed using the Coats Redfern (C-R) method, and validation was conducted using the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) methods. The results theoretically explain that sludge-based composite powder explosion suppressants can effectively suppress aluminium powder explosions and exhibit a blocking effect. Surface morphology and material element characterization experiments were conducted before and after the explosion, combined with pyrolysis characteristics. The analysis demonstrated that the inhibition mechanism of sludge-based composite powder explosion suppressants on aluminium powder explosion primarily involves two aspects: physical inhibition (MPP coating inhibition, porous adsorption isolation) and chemical inhibition (decomposition heat absorption, product oxidation). The theoretical findings provide evidence of the superior inhibitory effects of sludge-based composite powder explosion suppressants, offering new insights for the resource utilization of sludge waste and the development of novel explosion suppression materials.

Pyrolysis of combustible fractions in excavated waste: Effect of landfill time on pyrolysis characteristics analyzed by TG-FTIR-MS

Excavated waste in landfills contains non-negligible amounts of combustible fractions, whose mining and thermochemical treatment are promising to save land occupation and achieve energy utilization. Considering the possible changes of combustible fractions in the excavated waste during landfill time, this study comprehensively analyzed the impact of landfill time on the thermogravity characteristics, pyrolysis kinetics, products composition, and pyrolysis pathways of excavated waste using TG-FTIR-MS. The findings indicated a positive correlation between landfill time and the remaining mass resulting from pyrolysis. The activation energies for pyrolysis of excavated waste were found to be greater than those of fresh waste. Specifically, the activation energy values increased from 230.49 kJ/mol to 289.11 kJ/mol for polyethylene, from 216.38 kJ/mol to 260.91 kJ/mol for polypropylene, from 219.04 kJ/mol to 240.06 kJ/mol for expanded polystyrene, and from 210.01 kJ/mol to 279.93 kJ/mol for polyethylene terephthalate, respectively. The increment of activation energies indicates an elevated level of difficulty in the pyrolysis reaction. The pyrolysis kinetics of excavated waste were examined by the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Starink methods. It was found that FWO method showed an optimal fitting result (R2 =0.9681–0.9819), while KAS and Starink methods also showed satisfactory fitting performance. The TG-FTIR-MS results revealed that the effect of landfill time on products categories are negligible, but the change in the content of pyrolysis products is more pronounced. This study is hoped to provide fundamental insights into the thermochemical disposal and energy recovery of excavated waste in landfills.

Study on the combustion characteristics and kinetics of water hyacinth co-combustion with anthracite

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.