FWO Methods Research Articles

Pyrolysis and Physicochemical, Thermokinetic and Thermodynamic Analyses of Ceiba aesculifolia (Kunth) Britt and Baker Waste to Evaluate Its Bioenergy Potential.

Ceiba aesculifolia is an important species in Mexico that generates significant amounts of biomass waste during its exploitation, which can be utilized to produce energy. This study presents the characterization of this waste based on chemical (proximal and elemental) and thermal analyses (TGA-DTG) at different heating rates (β = 10-30 °C/min (283-303 K/min)) in the presence of nitrogen and in a temperature range of 25-900 °C. Kinetic parameters were calculated and analyzed as well. Activation energy (Ea) and the pre-exponential factor (A) were determined using the Friedman (132.03 kJ/mol, 8.11E + 10 s -1), FWO (121.65 kJ/mol, 4.30E + 09), KAS (118.14 kJ/mol, 2.41E + 09), and Kissinger (155.85 kJ/mol, 3.47E + 11) kinetic methods. Variation in the reaction order, n (0.3937-0.6141), was obtained by Avrami's theory. We also calculated the thermodynamic parameters (ΔH, ΔG, ΔS) for each kinetic method applied. The results for Ea, A, n, ΔH, ΔG, and ΔS show that this biomass waste is apt for use in pyrolysis. Moreover, the moisture (<10%), ash (<2%), volatile material (>80%), and HHV (>19%) contents of C. aesculifolia allowed us to predict acceptable performance in generating energy and fuels. Finally, infrared spectroscopy analysis (FT-IR) allowed us to identify important functional groups, including one that belongs to the family of the aliphatic hydrocarbons.

Investigation of the Thermokinetic and Thermodynamic Parameters of Biodiesel and Associated Oil from Palm Kernel Oil During Thermal Degradation

ABSTRACT This study investigates the kinetic and thermodynamic parameters of the thermal degradation of biodiesel produced from low-grade palm kernel oil. In this work, biodiesel was produced through a two-step transesterification from a palm kernel oil having a free fatty acid content of 5.7%. The first step uses 25% methanol (wt% of palm kernel oil) and 1% sulfuric acid (wt% of palm kernel oil) to reduce the free fatty acids content to 0.3% within 30 min reaction time. In the second step, a methanol-to-oil molar ratio of 6:1 and 0.6% (wt% of palm kernel oil) of KOH yielded a palm kernel oil conversion of 96.96% after 30 min reaction time. The palm kernel biodiesel was analyzed using Fourier Transform Infrared spectroscopy, gas Chromatography tandem mass spectrometry, nuclear magnetic resonance spectroscopy (1H and13C), and thermogravimetric analysis. The thermal stability of palm kernel biodiesel was assessed through the kinetic and thermodynamic parameters of biodiesel thermal decomposition using isoconversional techniques. The Flynn-Wall-Ozawa, Kissinger-Akariha-Sunose, and Starink models were used to evaluate the kinetic parameters, while the Coats and Redfern technique was used to forecast the most probable mechanism of the palm kernel biodiesel thermal degradation. The average activation energies of 108.60 kJ mol−1, 107.75 kJ mol−1 and 95.77 kJ mol−1 using the Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink methods, respectively. FWO method best described palm kernel oil and biodiesel decomposition, with the highest R2 values of 0.94 for the oil and 0.93 for biodiesel The results obtained from the thermodynamic study (ΔH = 218.48 kJ.mol−1, ΔG = 200.05 kJ.mol−1 and ΔS = 27.10 J.mol−1.K−1) revealed that the biodiesel thermal degradation was an endothermic, non-spontaneous process governed by a three-dimensional diffusion reaction mechanism.

Phase transformation and roasting kinetics of CIGS waste in air atmosphere

Copper indium gallium diselenide (CIGS) solar cells produce a lot of CIGS waste in the production process. TAK method was used to study the roasting kinetics of CIGS waste to separate and recovery harmful elements of environment. The oxidation of CIGS is different for different heating rates, oxides of various metal elements are formed at lower roasting rates, but InGaCuO4 is formed at higher roasting rates. The E of each oxidation process was obtained by FWO method and KAS method respectively. The E of element In at lower roasting rates are 104.43 KJ/mol and 112.17 KJ/mol. The E of Ga are 105.86 KJ/mol and 113.52 KJ/mol. The E of Cu are 134.46 KJ/mol and 141.35 KJ/mol. The E of InGaCuO4 were 33.45 KJ/mol and 45.53 KJ/mol. The model function of CIGS waste reaction was determined by Malek method analysis. The oxidation mechanism model of element In is No.39 and No.40 functions: Exponential law. The oxidation mechanism model of the element Ga is function No.37: Chemical reaction control, and the oxidation mechanism model of the element Cu is function No.9:3-D diffusion Zhuraalev-Lesokin-Tempelman. The mechanism model of CIGS waste higher roasting rates in second stage is function No.9:3-D diffusion Zhuraalev-Lesokin-Tempelman. The results show that the heating rate of roasting process obviously affects the oxidation behavior of CIGS waste, so it is of great significance to control the heating rate to oxidizes CuO, Ga2O3 and In2O3 in CIGS waste, and to improve the separation and recovery efficiency of elements in the subsequent process.

Study on slurry forming performance and slurry combustion characteristics of diesel modified coal

In this study, modified low rank coal water slurry (M-LRCWS) was prepared by using diesel modified low rank coal (LRC) and compared with low LRC water slurry (LRCWS) to investigate the slurry formation mechanism and combustion characteristics of coal water slurry. Meanwhile, the combustion kinetics of coal-water slurry was investigated using kinetic methods to probe the combustion reaction mechanism. The results showed that the slurry formation concentration of LRC was 70 %, while the slurry formation concentration of M-LRCWS was 72 %, which was an increase of 2 %. The diesel modification positively affected the stability of CWS. The comprehensive combustion characteristics index of the same slurry deteriorated with increasing heating rate. At the same heating rate, M-LRCWS has better combined combustion performance, higher flammability and more stable ignition performance. Combustion kinetics calculations showed that the reaction activation energies were 105.50 kJ/mol for M-LRCWS and 99.59 kJ/mol for LRCWS using the FWO method, and 93.48 kJ/mol for M-LRCWS and 92.68 kJ/mol for LRCWS using the Starink method. The activation energy of M-LRCWS is slightly higher than that of LRCWS, which indicates that the diesel fuel is encapsulated in the coal particles and it is difficult to activate the substance. As a result, the dispersion system is more stable and favorable for storage and transportation. The physical functions of LRCWS and M-LRCWS were calculated using the Achar differential equation and the Coats-Redfern integral equation, and the results showed that both LRCWS and M-LRCWS followed the tertiary reaction (F3) mechanism.

Co-pyrolysis Behavior of Coal and Biomass: Synergistic Effect and Kinetic Analysis.

Co-pyrolysis of coal and biomass is an efficient way to utilize resources. This study investigates the co-pyrolysis behavior and kinetics of coal and biomass using thermogravimetric analysis (TGA) and TG-FTIR. Co-pyrolysis of coal and biomass exhibits a synergistic effect. When the biomass is 25%, the weight loss increases, showing a positive synergistic effect. When the biomass is 50%, it exhibits a negative synergistic effect. Increasing the heating rate can promote the generation of a synergistic effect. Co-pyrolysis involves two central pyrolysis stages: stage III (250-380 °C) and stage IV (380-550 °C). Friedman, FWO, KAS, and STA methods are used to calculate the activation energy for stages III and IV. The activation energy (E α) for co-pyrolysis is higher than that for coal or biomass pyrolysis alone. A positive synergistic effect is observed in stage III, while a negative synergistic effect is noted in stage IV. The master curve method determines an accurate reaction order (n) and pre-exponential factor (A) value of Coal75-Bio25. In stage III, E α = 238.81 kJ/mol, n = 2.4, A = 1.30 × 1021 s-1. In stage IV, E α = 37 8.01 kJ/mol, n = 4.0, A = 1.10 × 1027 s-1. The kinetic parameters in stage IV are significantly higher than those in stage III. TG-FTIR is used to analyze the synergistic effect of co-pyrolysis. Compared with coal and biomass pyrolysis separately, the Coal75-Bio25 pyrolysis process releases less CO2 and more CH4. These findings support the synergistic effect of coal and biomass during co-pyrolysis.

Catalytic co-pyrolysis of bauhinia purpurea seed and waste medical plastics for sustainable biofuel production: Kinetic analysis and prediction modeling

The present study aims to investigate the potential of Bauhinia purpurea seed (BPS) and waste medical plastic (WMP) as renewable fuels. Physicochemical and thermal studies show that BPS is a great raw material for pyrolysis because it has high calorific value, rich volatility, a lot of large functional groups, and favourable surface morphology. The activation energy was calculated using the KAS, FWO, Starink, and Friedman methods. Both RSM and ANN identified the optimal conditions for bio-oil production at a temperature of 550°C, a heating rate of 10 °C/min, a blend ratio of 70 % BPS (30 % WMP), and a particle size of 1 mm, with a generated bio-oil of 43.24 %. Notably, the predicted bio-oil yield (44.4 %) closely matched the experimental result (43.24 %). The bio-oil is obtained through pyrolysis, co-pyrolysis, and catalytic co-pyrolysis at optimum conditions. An analysis determined the suitability of bio-char as an activated carbon in catalytic pyrolysis.

Nano clay treated jute fiber reinforced epoxy composites: Thermo‐kinetic, morphological and mechanical analysis

AbstractCurrent scientific research prioritizes sustainable and cost‐effective materials due to the depletion of traditional non‐renewable sources. Natural fiber reinforced composite materials emerge as promising solutions. However natural fibers being hydrophilic in nature are less compatible with hydrophobic epoxy matrix, to address this issue nano clay treatment of jute fibers have been done and epoxy composites were formed with their reinforcement. Through FT‐IR, thermal, mechanical, and morphological analyses, both treated and untreated composites are evaluated. The treated composites exhibit a notable 19% increase in activation energy (FWO and KAS methods) compared to untreated ones (217.5–259 KJ/mol), indicating improved thermal stability. Moreover, the treated composite demonstrates a significant 38% boost in tensile strength (30–41.4 MPa) and a 28% enhancement in flexural strength (50–64 MPa), highlighting the impact of alkali‐nano clay treatment in reinforcing structural integrity. These enhancements suggest the potential applicability of composites manufactured with alkali‐nano clay treated jute fibers (A/NC/J fiber) across various industries. This innovative approach not only bridges the gap in sustainable material development but also offers cost‐effective solutions for commercial utilization.Highlights Analyzed alkali‐nano clay treatment effects on jute fiber in epoxy composites. Studied activation energy (FWO, KAS) for untreated and treated composites. Treated composites show a 19% increase in activation energy: Thermal stability Significant improvements: 38% rise in tensile, 28% increase in flexural strength.

A TGA-FTIR study on the pyrolysis of oil-based drilling cuttings and the influence of its solids on pyrolysis characteristics

During the drilling process in oil and gas fields, rock cuttings and other solid impurities are returned to the wellhead along with oil-based drilling fluids, forming oil-based drill cuttings. Organic pollutants in oil-based drill cuttings can be removed through pyrolysis. Although there has been some research on the pyrolysis of oil-based drilling cuttings, there is little analysis of the impact of rock-solid impurities in oil-based drill cuttings on the pyrolysis of organic components. Therefore, in this study, thermogravimetry coupled with infrared spectroscopy was used to analyze the pyrolysis characteristics of oil-based drill cuttings, exploring the major volatile components at different pyrolysis temperatures. Meanwhile, the oil and solids in oil-based drilling cuttings were separated by Soxhlet extraction, and the influence of solids on pyrolysis characteristics was studied. The results showed that the average pyrolysis activation energy and pre-exponential factor of the main pyrolysis stage of oil-based drill cuttings obtained by the FWO method were 50.6 KJ/mol and 3.951×104 s−1, respectively, while those of the separated residual oil were 84.7 KJ/mol and 2.905×109 s−1, respectively. This indicates that solids in oil-based drilling cuttings is increasing the mass loss rate during pyrolysis. The difference in pyrolysis kinetics between oil-based drilling cuttings and residual oil indicates that the solid in oil-based rock cuttings provides a surface for the reaction, which provides a reaction site for the decomposition of hydrocarbons to produce lighter volatile hydrocarbons. Additionally, the results of infrared spectroscopy indicated that the volatile products of the pyrolysis of oil-based drilling cuttings include CH4, CO, CO2, H2O, aldehydes, organic acids, etc. CH4 is the main product of the first weight loss stage, mainly released between 150°C and 200°C. With the increase in temperature, the concentrations of H2O, CO2, aldehydes, and organic acids gradually increased. At 600°C, the maximum concentration of CO2 release occurred, and the release of CO2 was the main reason for the third-stage weight loss in the pyrolysis of oil-based drilling cuttings

Determination of Kinetic and Thermodynamic Parameters of Biomass Gasification with TG-FTIR and Regression Model Fitting

In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as a basis for kinetic analysis with three different isoconversional, model-free methods, which were the KAS, FWO and Friedman methods. Afterwards, the activation energy and the pre-exponential factor were determined, and no significant difference could be identified among the used methods (difference was under 5%), achieving 203–270 kJ/mol of Ea on average. Thereafter, the thermodynamic parameters were studied. Based on the TG-FTIR data, a logistic regression model was fitted to the data, which gives information about the thermal degradation and the obtained components with different heating rates. The FTIR analysis resulted in differential peaks corresponding to the studied components that were detected within the temperature range of 350–380 °C. The primary degradation processes occurred within a broader temperature range of 200–600 °C. Accordingly, in this work, the use of logistic mixture models as an alternative to traditional kinetic models for the description of the TGA process was also investigated, reaching adequate performance in fitting by a validation data coefficient of determination of R2 = 0.9988.

Design, synthesis, characterization, in vitro cytotoxic, antimicrobial, antioxidant studies, DFT, thermal and molecular docking evaluation of biocompatible Co(II) complexes of N4O4-macrocyclic ligands

Bioactive cobalt (II) macrocyclic complexes [Co(N4O4ML1)Cl2]-[Co(N4O4ML3)Cl2] have been synthesized by using the macrocyclic ligands [N4O4ML1], [N4O4ML2], and [N4O4ML3] that have an N4O4 core. These three macrocyclic ligands were all isolated in pure form, together with their complexes. Microanalytical investigations, FT-IR NMR, Mass, magnetic moments, electronic, PXRD, TGA, and EPR spectrum studies were used to analyse their structures. For these complexes, an octahedral geometry is proposed for the metal ion. By using molecular weights and conductivity measurements the monomeric and non-electrolytic nature has been confirmed. The Coats-Redfern and FWO methods are used to determine the thermodynamic characteristics of the ligands and their Co(II) complexes. The molecular modelling using the DFT technique displays the bond angle, bond lengths and quantum chemical properties. To determine their ability to prevent the growth of harmful fungus and bacteria, the ligands [N4O4ML1]- [N4O4ML3] and their complexes were tested in vitro against A. Niger, C. albicans and B. subtilis, S. aureus, E. coli and S. typhi fungal and bacterial organisms, respectively. By using DPPH free radical scavenger assays, the in vitro antioxidant capabilities of each compound were evaluated. The [Co(N4O4ML3)Cl2] antioxidative capabilities revealed significant radical scavenging power. The MTT assay was used to assess the toxicity of all the synthesised compounds under inquiry on MCF-7, HeLa, and A549 cancer cells. The findings revealed that the ligand and the compounds gave outstanding IC50 values in the range of 9.07–36.25 (uM) at a concentration of 25 ppm. Among all the substances evaluated, [Co(N4O4ML3)Cl2] complex was discovered to be the most active and least cytotoxic. Additionally, docking investigations of the produced compounds were carried out in order to validate the biological outcomes.

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.

Pyrolysis study of a waste plastic mixture through different kinetic models using isothermal and nonisothermal mechanism.

Pyrolysis can be a convenient way to produce oils and gases simultaneously, as well as hydrocarbons and even crude petrochemicals. It can also be used to produce energy from a waste plastic mixture (WPM). To ascertain the kinetics parameters at the heating rates of 5, 10, 20, and 50 °C min-1, various kinetic models, including (a) model-fitting and (b) model-free, which are further separated into isothermal and non-isothermal categories, have been selected. The apparent activation energy (E a) and pre-exponential factor (A a) were calculated using the Friedman (model-free isothermal), KAS, FWO (model-free non-isothermal), and Coats-Redfern (model-fitting non-isothermal) approaches. The activation energy (E a), pre-exponential component (A a), and overall reaction order (n) were also calculated using a multi-linear regression methodology. In addition, the solid fuel characterization of WPM has been compared with previous literature results, as have the physico-chemical characteristics of pyrolytic oil. Finally, a brief mention of WPM's kinetic process has been included in this work. However, the results indicated two stages of thermal degradation and volatilization of the WPM zone during pyrolysis (410-510 °C, 510-770 °C). In the temperature range of 410-510 °C, 510-770 °C, two-stage thermal degradation zones are used to analyze the kinetic parameters for WPM. The result showed the average activation values obtained by the KAS, FWO, and Friedmam methods were 297.61, 295.25, and 267.26 kJ mol-1. In the case of the Coats-Redfern methods, the lowest activation energy was obtained by the PT1 kinetic model at 22.56 kJ mol-1, and the highest activation energy was found in the D3 kinetic model at 418.80 kJ mol-1 in the temperature zone of 410-510 °C. The temperature zone with the lowest activation energy was found to be between 510 °C and 770 °C.

Co-gasification of waste shiitake substrate and waste polyethylene in a fluidized bed reactor under CO2/steam atmospheres

This study investigated the co-gasification of agricultural and plastic wastes, which is a potential method for waste disposal. Waste shiitake substrate (WSS) and polyethylene (PE) were selected and their properties were investigated. The thermal degradation behavior and gases produced were explored using thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG-FTIR). In addition, the activation energy was determined by the FWO method, and the synergistic effect and gas yield were estimated. The co-gasification of WSS and PE assisted by CO2 and steam was conducted using a bubbling fluidized bed gasifier. Results indicate that BR60 % had the maximum C–O band, C–C bond, C–H band, and CO yields. Blending WSS and PE resulted in an evident synergistic effect. The activation energies of BR20 % had the lowest value. The Taguchi method was used to determine the optimal parameters, maximum normalized H2 concentration, H2/CO ratio, CGE, and exergy efficiency. The H2 yield and H2/CO ratio were predominantly affected by the CO2/(CO2+H2O) ratio, and the best concentration and ratio were 28.6 % and 1.34. The CGE and exergy efficiencies were predominantly affected by gasification temperature, and the best results were 71.6 % and 72.4 %, respectively. Finally, the collected tars were analyzed using gas chromatography-mass spectrometry (GC/MS).

Phase transformation and roasting kinetics of vanadium slag in air atmosphere

The essential supply of vanadium for production, vanadium slag, is generally extracted by way of roasting-leaching process. In roasting, it was located that the leaching charge of vanadium improved and the break of spinel is more obvious with the rise of roasting temperature. The phase transformation of vanadium slag happened in the roasting process, but it is unclear that the “kinetic triplet factors” of the activation of vanadium slag after roasting. Therefore, the apparent activation energy (E) and the pre-exponential factor (A) of olivine and spinel oxidation were obtained by FWO method and KAS method. The E value were 140.97 kJ/mol (olivine) and 214.68 kJ/mol (spinel). The pre-exponential factors were 446491.41 min−1 (olivine) and 420236191.33 min−1 (spinel). The chemical reaction control and 3-D diffusion Zhuraalev-Lesokin-Tempelman mechanism model were determined by Malek method. The results show that the activation energy of vanadium oxidation process can be increased by increasing the roasting temperature at 1100 K-1250 K, which makes the conversion of spinel phase difficult. From the perspective of kinetics, it is important to select a reasonable roasting temperature to improve the activation roasting efficiency of vanadium slag. This study provides some theoretical guidance for strengthening the roasting process and efficient extraction of V element of vanadium slag.

Effect of water soaking and air drying on the thermal effect and heat transfer characteristics of coal oxidation at the low-temperature oxidation stage

The microstructure, thermal behaviour (30 °C-300 °C) and thermophysical properties (30 °C-300 °C) of raw and water-soaked air-dried coal samples were analysed through scanning electron microscopy, differential scanning calorimetry and laser thermal conductivity meter to study the effect of water soaking and air drying on the thermal effect and heat transfer characteristics of coal at the low-temperature oxidation stage. Experimental results show that the action of water soaking and air drying changes the apparent morphology of coal, increasing the density of surface pore distribution and number of all pore types to different degrees. Under the same temperature conditions, water-soaked air-dried coal has lower heat absorption and heat release than raw coal. Moreover, the time required by water-soaked air-dried coal to reach thermal equilibrium is 32.4 s faster than that needed by raw coal. The activation energy of water-soaked air-dried coal calculated by using the KAS and FWO methods is reduced to about 83% of that of raw coal. This result indicates that water soaking and air drying increase the tendency of coal to self-ignite. The thermal diffusivity of water-soaked air-dried coal is higher than that of raw coal and shows a maximum difference of 0.005 mm2/g at 60 °C. The specific heat capacity and thermal conductivity of water-soaked air-dried coal are lower than those of raw coal and show the maximum differences of 0.19 J g/K and 0.18 W/m·K at 210 °C and 300 °C, respectively. Although the spontaneous combustion of water-soaked air-dried coal spreads at a faster rate than that of raw coal, the hazards following the spontaneous combustion is less than that of raw coal. This research contributes to understanding the effect of water soaking and air drying behaviour on coal spontaneous combustion characteristics.

Catalytic Effects on Combustion Behavior of Oil Shale: Thermal Conversion, Kinetic, Mechanism Analyses

ABSTRACT In order to solve the problem of traditional energy combustion and to achieve the comprehensive use of oil shale. This work investigated the impact of potassium-containing catalysts on the combustion reactivity of Beipiao oil shale through TG, FTIR, and SEM analysis. Results showed that the catalyst of different proportions reduced the oil shale ignition temperature by 9.34–17.67°C and burnout temperature by 9–51.67°C, optimal catalyst addition (5%) exhibited the most effective catalytic effect. The catalyst effect was affected by heating rates, the lower the heating rate, the more favorable the oil shale combustion. In addition, the hydroxyl and ether oxygen groups of combustion residue increased with catalyst, the absorption peak intensity of carbonate reduced. Suggesting that the catalyst promoted the decarbonization cracking of oil shale, thereby accelerating the release of volatiles and the decomposition of inorganic mineral carbonate. Finally, activation energy was calculated using the Friedman and FWO methods. The results obtained from both kinetic methods were highly consistent, obviously reductions in activation energy under catalytic action.

Pyrolytic energy performance and byproducts of Ganoderma lucidum: Their multi-objective optimization

Fossil fuels-related environmental issues, such as global climate change and soil and water acidification, are driving countries to develop biomass energy sources. As a second-generation biofuel with a significant spatiotemporal availability for global consumption, Ganoderma lucidum (GL) calls for the characterization and multi-objective optimization of its pyrolytic performance and byproducts. The GL pyrolysis was divided into three stages, with the main stage occurring between 205 and 630 °C. The activation energy for the main stage was estimated at 221.23 kJ/mol and 222.83 kJ/mol according to the FWO and KAS methods, respectively. The primary volatile products of the GL pyrolysis between 200 and 600 °C included H2O, CH4, CO2, CO, CO, C-O(H), CC, and NH3. The multi-objective optimization indicated that the GL pyrolysis between 650 and 750 oC jointly led to maximum energy yield and minimum gas emission. Biochar produced from GL (GLB) between 400 and 600 °C enhanced its aromaticity and stabilized the functional groups in the carbon structure. GLB obtained exhibited an increased number of porous structures and decreased aromaticity. These results provide a theoretical and practical basis for enhancing and volarizing the comprehensive circularity of GL biomass.

Characterization, kinetics and thermodynamic evaluation of struvite produced using ferrochrome slag as a magnesium source

There is limited data on studies that have focused on the kinetics, thermodynamics, and characterization of struvite crystallization from alternative magnesium sources. This study focused on thermal analysis of struvite (produced using ferrochrome slag as a magnesium source) and the results indicated that the residual quantities of struvite were lower than the theoretical mass loss of struvite of 51.42%. When using ferrochrome slag (FCS) as the magnesium source, 47.9%, 47.4%, and 46.9% losses in mass were observed for heating rates of 5°C/min; 10°C/min and 15°C/min respectively. The mean activation energies for struvite produced using FCS were deduced using isoconversional kinetic methods and ranged from 49.81to 56.20 kJ/mol which is very similar to the activation energies deduced using MgCl2. The study also focused on the surface morphology, and particle size of the final product at different pH and N:P ratios. The final particle size distribution of the product was significantly influenced by the solution pH. To improve the crystal growth kinetics for both MgCl2 and FCS, a high ratio of N:P molar ratios should be adopted. The product's highest median particle size was obtained using FCS as the magnesium source at a low pH. Median particle size increased with decrease in pH, at a pH of 7.5 the recorded median particle size was 96 µm whilst, the lowest was 31 µm at a pH of 9.5. The highest percent of fines (<10 µm) was recorded at a pH of 9.5 using FCS as magnesium source in the metastable region of struvite precipitation whereas at a pH of 7.5 no fines (<10 µm) were recorded. SEM images confirmed that the struvite underwent morphological changes when prepared with FCS in comparison to that produced using MgCl2. The surface morphology of the finished product demonstrated the presence of irregular shaped particles, due to presence of impurities. The kinetic data showed that struvite precipitation was limited by the chemical reaction step. Model fitting was used to determine the reaction control mechanism and the average activation energies obtained by four model free methods were FWO (56.2), KAS (51.67) Starink (49.61) and Tang (49.81) kJ/mol, indicating that the FWO method was the least accurate method. The thermodynamic data indicated that the thermal degradation of struvite crystals has a high degree of disorder, and the process is endothermic, irreversible, and non-spontaneous.

Waste catalyst potential for co-pyrolysis of biomass and single-use plastics: model-free isoconversional kinetics and thermodynamics

AbstractThe study aims to investigate the kinetic and thermodynamic characteristics of single and binary pyrolysis of biomass (date pits: DP) and single-use-plastics (polypropylene: PP, and polystyrene: PS), and the effect of adding natural catalysts—seashell (SS) and cuttlebone (CB) for ternary co-pyrolysis of the feeds. The activation energy (Ea) was calculated using different model-free kinetic methods, including Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (FWO), and Starink, utilizing information from the degradation at three heating rates from room temperature to 1173 K. The results showed that all three methods produced relatively similar Ea values with a high coefficient of correlation (R2), indicating a good fit for the data. The Ea values for single feeds of DP, PP, and PS using the FWO method were found to be in the range of 196–223 kJ/mol, while for binary feeds—DPPP and DPPPS—the values were found to be lower than for the individual plastics. The high Ea values of the binary plastic mixture are also reduced by ~ 40 kJ/mol in the ternary mixture due to biomass co-pyrolysis. Additionally, the study revealed that the addition of SS and CB catalysts positively affected the ternary co-pyrolysis by reducing activation energy by 28.5 and 5.8%, respectively, due to the catalytic activity of 20 wt% of CaCO3 decomposition from the seashell and cuttlebone added in situ to the feeds. The research contribution of this study lies in its comprehensive investigation of the kinetic and thermodynamic characteristics of biomass and plastic pyrolysis, including single and binary systems, as well as the introduction of natural catalysts for ternary co-pyrolysis. The findings highlight the effectiveness of the studied catalysts in reducing activation energy and provide valuable insights for the development of efficient biomass and plastic waste conversion processes.

Thermal Analysis Kinetics Study of Pulverized Coal Combustion under Oxygen-Rich Atmosphere.

The thermal analysis kinetic behavior of pulverized coal combustion in different oxygen-rich atmospheres is studied with a thermogravimetric (TG) analyzer. The effects of heating rate on combustion characteristic are considered. The results showed that the combustion rate of pulverized coal increased and the burnout time decreased under the conditions of an oxygen-enriched atmosphere and high heating rate. As the heating rate increases, the TG and derivative TG curves of the coal samples generally move toward the high-temperature region, and the thermal hysteresis phenomenon occurs. The changes in oxygen concentration and heating rate mainly affect the combustion stage of coal samples. The decrease in heating rate or the increase in oxygen concentration will cause a decrease in ignition point temperature and burnout temperature. Under the condition of 40% O2, the oxygen concentration and heating rate have the greatest influence on the combustion characteristic parameters. In addition, the combustion reaction of pulverized coal in the warming process was analyzed by FWO and KAS methods, respectively. The results showed that the changes in oxygen concentration and heating rate affected the activation energy, and the activation energy of coal samples increased with the increase in oxygen concentration.