Master Plot Method Research Articles

Influence of iron-containing petrochemical sludge ash on the pyrolysis of pine wood: Thermal behaviors, thermodynamic analysis, and kinetic parameters

The pyrolysis characteristics and kinetics of pine wood (PW) with the presence of iron-containing petrochemical sludge ash (PSA) were studied using thermogravimetric analysis at non-isothermal conditions. The thermal conversion of PW with the presence of PSA could be characterized via a three-stage reaction, including the moisture release, pyrolysis reactions and gas–solid reaction, and solid–solid reaction between char and iron oxides. The pyrolysis characteristic parameters analysis showed that the presence of PSA indeed promoted the conversion of PW. Thermodynamic analysis revealed that the Fe2O3 in PSA was characterized by a gradual loss of oxygen during co-pyrolysis. The kinetic parameters were calculated by the Starink method combined with master-plots method. The presence of PSA would decrease the activation energy, and the minimum average value was 167.00 kJ/mol at 15% PSA addition. The most suitable kinetic models for the pyrolysis of PW and its mixtures with PSA were D3 and D4, respectively.

Kinetic Analysis of Pyrolysis and Thermo-Oxidative Decomposition of Tennis String Nylon Wastes.

Thermal degradation of nylon-6 tennis string nylon wastes in inert nitrogen and air atmospheres was investigated by means of multiple heating-rate thermogravimetric analyses. The results obtained under the heating rates of 5–20 K/min are compared in terms of degradation feature and specific temperature for two atmospheres. Using nonisothermal data, kinetic analysis was thoroughly conducted using various isoconversional model-free methods, including Starink, Madhusudanan–Krishnan–Ninan, Tang, Coats–Redfern, and Flynn–Wall–Ozawa methods. With these kinetic analysis methods, the activation energy over the entire degradation process was successfully calculated. By means of the model-fitting master-plots method, the first-order chemical reaction model was determined to be the most appropriate mechanism function for describing pyrolysis and oxidative thermal degradation of nylon-6 waste. Using kinetic parameters, satisfactory matching against experimental data resulted using the Coats–Redfern method for both cases. Furthermore, thermodynamic parameters such as changes in entropy, enthalpy, and Gibbs free energy during thermal degradation processes were evaluated.

Pyrolysis of pigeon pea (Cajanus cajan) stalk: Kinetics and thermodynamic analysis of degradation stages via isoconversional and master plot methods

Detailed analysis of thermo-kinetics, reaction mechanism, and estimation of thermodynamic parameters are imperative for the design of reactor systems in thermochemical conversion processes. Present investigation was aimed at exploring the pyrolysis potential of pigeon pea stalk (PPS) by thermogravimetric experiments at 10, 20, and 30 °C/min heating rates. Maximum devolatilization of PPS was found to take place below 480 °C. The average activation energy for PPS pyrolysis was found to be 95.97, 100.74, 96.24, and 96.64 kJ/mol by Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Starink, and Friedman method, respectively. Statistical analysis by one way analysis of variance method by employing Tukey test revealed that the difference in activation energy estimated from different methods was insignificant. Thermodynamic parameters (ΔH, ΔS, and ΔG) together with reaction mechanisms were also evaluated. Difference in the activation energy and enthalpy was found to be less than 5 kJ/mol. R2 and R3 models were found best fitted with experimental PPS pyrolysis data.

Investigation of kinetic and thermodynamic parameters approaches to non-isothermal pyrolysis of mustard stalk using model-free and master plots methods

Present work based on thermogravimetric analysis (TGA) to decipher in detail the pyrolysis of mustard stalk (MS) for investigating its potential for bioenergy feedstock at three heating rates (5, 10, and 20 °C/min). The thermal degradation behaviors of MS were carried out at three heating rates (5, 10, and 20 °C/min). The kinetic and thermodynamic parameters were examined using model-free isoconversional Flynn- Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) model. The obtained activation energy for pyrolysis of MS using FWO and KAS to be 132.47 and 130.62 kJ/mol. Kissinger method was used to compute pre-exponential factor found to be in the range of 105 to 1016 s−1 at different heating rates. The average ΔH was 127.70, and 125.8 kJ/mol and ΔG is 127.74 and 127.87 kJ/mol from FWO and KAS respectively, all ΔH positive indicated endothermic nature. The Coats-Redfern approach was used to estimate the thermal degradation reaction mechanism, which revealed that the diffusion model was best suited to reflect the degradation process involving both exothermic and endothermic reactions. The analysis can help augment the experimental studies, and physicochemical characterization revealed its fuel characteristic since MS is sustainable and promising biomass for alternative processes in terms of waste management strategies.

Life cycle assessment of the co-combustion system of single-use plastic waste and lignite coal to promote circular economy

Single-use plastics waste is a thermosetting-thermoplastic polymer generated specifically from packaging industries. Incineration, landfilling, combustion, open discharge in liquids fail its effective disposal. Co-combustion via co-processing is a novel technique for disposal. In this study, investigative thermogravimetric analysis of the co-combustion of lignite coal (AL) and single-use plastic waste (PW) in the blend ratios of 50:50, 60:40, 70:30 was carried out under non-isothermal conditions to promote co-combustion via co-processing technique for environment-friendly disposal. Thermal degradation behavioral study was carried out at higher blending ratios of 30–50%. The effect of the mass ratio of PW to AL on co-combustion characteristics was analyzed. The Freeman-Carroll, Sharp-Wentworth methods derived energy of activation for the process of co-combustion in the limits of 65–155 kJ/mol, 44–75 kJ/mol. Volume Contracting and Diffusional Reaction 2D solid-state reaction mechanisms were followed by the co-combustion system as derived by Coats-Redfern and Kennedy-Clark methods. Master plot method validated the same results. The co-combustion performance was evaluated using co-combustion (CSI), ignition (IG), burnout (IB) indices. The highest CSI value was reported for the 60:40 blend. Burnout temperature (Tb) decreased with an increase in blending ratio and suggested an effective co-combustion process. Blend (70:30) reported the highest interaction in blends and confirmed the synergistic effect. The principal component analysis described the co-combustion process as three stages (100–200, 265–425, 425–700) oC with specific materials. The co-combustion process was optimized using the methodology of surface response and validated using neural network models (NNM 4,5) for the effect of temperature and blend ratio on mass loss. The characterization study confirmed the presence of minerals alumino-silicates, dimorphs pyrite, marcasite, gypsum, barite, hydrated sulfates, calcite, siderite, and functional groups –OH, -CH2, -Si-O responsible for autocatalytic reactions. Life cycle assessment confirmed the sustainability of the co-combustion process of lignite and plastic waste. The present study benefits for scale-up, optimization, waste to energy conversion, pollution reduction, and environmentally friendly disposal via the co-combustion process.

Properties, combustion behavior, and kinetic triplets of coke produced by low-temperature oxidation and pyrolysis: Implications for heavy oil in-situ combustion

This work aimed at investigating the crucial factor in building and maintaining the combustion front during in-situ combustion (ISC), oxidized coke and pyrolyzed coke. The surface morphologies, elemental contents, and non-isothermal mass losses of the oxidized and pyrolyzed cokes were thoroughly examined. The results indicated that the oxidized coke could be combusted at a lower temperature compared to the pyrolyzed coke due primarily to their differences in the molecular polarity and microstructure. Kinetic triplets of coke combustion were determined using iso-conversional models and one advanced integral master plots method. The activation energy values of the oxidized and pyrolyzed cokes varied in the range of 130–153 kJ/mol and 95–120 kJ/mol, respectively. The most appropriate reaction model of combustion of the oxidized and pyrolyzed cokes followed three-dimensional diffusion model (D3) and random nucleation and subsequent growth model (F1), respectively. These observations assisted in building the numerical model of these two types of cokes to simulate the ISC process.

Thermogravimetric pyrolysis of onion skins: Determination of kinetic and thermodynamic parameters for devolatilization stages using the combinations of isoconversional and master plot methods

Thermogravimetric pyrolysis of onions skins was studied thoroughly for the first time. Kinetic calculations of devolatilization stages were performed applying direct Arrhenius plot (DAP) method and combinations of isoconversional and Criado’s Z(α) master plot (CZMP) methods. The kinetic parameters calculated using combined methods were utilized successfully to reproduce the experimental kinetic curves whereas those calculated using DAP method failed in this sense. The average Ea values of isoconversional methods were between 164.0 and 172.0 kJ/mol. The CZMP method yielded multiple F-type reaction mechanisms. The simplified kinetic models of combined methods were also developed by using single reaction mechanisms deduced from multiple reaction mechanisms. The Friedman-CZMP combination was the best option for developing simplified/unsimplified kinetic models. Determination of reaction mechanism using DAP method by searching for the highest R2 value of regression equation among several candidates was found unreliable. ΔH, ΔG and ΔS values were calculated for 10 °C/min heating rate.

Thermogravimetric and Kinetic Analysis of High-Temperature Thermal Conversion of Pine Wood Sawdust under CO2/Ar

The gasification behavior of pine wood sawdust was investigated in CO2 with different heating rates of 5, 10, 15, and 20 °C/min from room temperature to 1400 °C by thermogravimetric analysis (TGA) and mass spectrometry (MS). It was also examined under Ar to compare the differences observed under CO2 at heating rate of 10 °C/min. Kinetics of pine wood sawdust thermal decomposition was determined by the models of FWO, KAS and master plot method. TGA results revealed different reaction sections from pyrolysis to char gasification under CO2. The pyrolysis behavior was similar under CO2 and Ar and had a similar energy required value about 590 kJ/kg from 250 °C to 420 °C. CO, CH4, and H2 were the primary gases obtained from thermal decomposition, and the amounts of which in CO2 atmosphere were higher than those obtained in Ar. The average activation energy for pyrolysis under CO2 was 184.72 kJ/mol.

Dynamic Pyrolysis Characteristics, Kinetics and Products Analysis of Waste Tire Catalytic Pyrolysis with Ni/Fe-ZSM-5 Catalysts Using TG-IR-GC/MS

Catalysts are usually used in the thermal conversion of waste tires to enhance the efficiency of the process and the quality of pyrolytic products. Recently, it has already been proved that Ni/Fe bimetallic catalysts had an effective catalytic effect on the thermal decomposition of organic solid wastes. Herein, we employed a TG-IR-GC/MS system to investigate the kinetics and product analysis of waste tire catalytic pyrolysis using Ni/Fe bimetallic ZSM-5 as catalysts. Iso-conversional methods and master-plot methods were employed to estimate the activation energies and reaction model of waste tire catalytic pyrolysis. The results illustrated that the ZSM-5 loading with 7 wt.% Ni and 3 wt.% Fe had the best catalytic effect on decreasing the activation energies with a reduction of 13%. The determination of kinetic models showed that both non-catalyzed and catalyzed pyrolysis were fitted to a Fn model while the addition of a catalyst reduced the reaction order to varying degrees. Both FTIR and GC/MS results suggested that the metallic Ni-based catalyst had strong ability to transform alkenes into aromatic hydrocarbons. Ni/Fe bimetallic catalysts showed almost the same catalytic performance as the Ni metallic catalyst, which could reduce the cost of the catalyst. Thus, this study could deepen the understanding and provide a basic guideline of Ni/Fe bimetallic catalysts on the catalytic pyrolysis process of waste tires.

Investigation on oxidation stability of V2AlC MAX phase

Nanolaminated V2AlC MAX phase has been synthesized through pressureless sintering by varying aluminum content. The oxidation stability of the V2AlC is studied under non-isothermal conditions through a TGA/DTA technique at multiple heating rates in the air atmosphere. It is observed that the oxidation of V2AlC occurred in two different stages. Thermodynamic calculations are also performed to predict the oxidation reaction pathway of V2AlC MAX phase. The kinetic triplets (activation energy, pre-exponential factor and reaction mechanism) are determined for both stages of oxidation. The Kissinger-Akahira-Sunose (KAS) and the Flynn-Wall-Ozawa (FWO) isoconversional kinetic methods are used to calculate the activation energy. The reaction mechanism is identified by employing the integral master plot method. The results indicated that the nucleation mechanism dominated the oxidation process in the V2AlC MAX phase. P4 and A4 nucleation reaction mechanisms are identified in stage I and stage II of oxidation, respectively.

Thermokinetic study of macadamia carpel pyrolysis using thermogravimetric analysis

AbstractThe macadamia productive process generates a large amount of waste, such as walnut carpel, that is improperly disposed of in most instances. This residue is a promising feedstock for biofuel production and it can be converted through thermochemical routes. Liquid pyrolysis products obtained contain a bio‐oil with great potential for the production of fuels and fine chemicals. The goal of this study was to characterize the macadamia carpel for the first time by ultimate, proximate, FTIR, and TG analysis, as well as HHV determination, which showed this is a potential candidate for thermochemical conversion processes. Thermodynamic and kinetic pyrolysis behaviours were evaluated using Ozawa, Kissinger, Starink, and KAS isoconversional models (140.12, 137.69, 137.41, and 146.63 kJ mol−1, respectively), which attested to the product favourability and the operational viability. Additionally, the master plot method was applied to complete the kinetic description, which identified diffusion and nucleation mechanisms during the carpel degradation. After 50% conversion, the third‐order reaction mechanism occurred due to a predominant lignin decomposition. The results showed that the macadamia carpel properties are similar to traditional feedstock, that it may be decomposed into bio‐oil, and that it can be used as an alternative energy source or bio‐chemicals precursor.

Insight into master plots method for kinetic analysis of lignocellulosic biomass pyrolysis

The determination of the kinetic triplet including the activation energy, frequency factor, and kinetic mechanism function is a key objective in kinetic analysis of solid-state reactions like lignocellulosic biomass pyrolysis. The master plots method is usually used to determine the kinetic mechanism function once the activation energies as a function of conversion are estimated from an isoconversional method. A critical study of the master plots method has been performed by analyzing theoretically simulated processes with varying activation energies and frequency factors. The accuracy of the resulting kinetic mechanism function calculated by the master plots method is strongly dependent on the variation degree of the frequency factor with conversion and the conversion dependency of activation energy from isoconversional methods. The utilization of the master plots method without considering the variation degree of the frequency factor with conversion may result in misestimating kinetic mechanism function.

Metallurgical Coke Gasification by Carbon Dioxide under Nonisothermal Conditions: A Kinetic Study.

Metallurgical coke gasification by carbon dioxide was kinetically investigated through the use of thermogravimetric analysis under nonisothermal conditions. The results showed that the activation energy, gained by the Cai–Chen iterative model-free method, was estimated to be 183.15 kJ·mol–1. Notwithstanding, the mechanism function f(α) cannot be directly determined due to the fact that f(α) and the pre-exponential factor Aα were lumped together as [Aαf(α)]; this situation may be tackled by means of the master-plot methods. The most probable mechanism function, determined by the Málek master-plot method (based on Z(α) master plots), was discovered to be the Johnson–Mehl–Avrami equation. The usefulness of the compound kinetic calculation technique founded upon complemental application of the Málek master-plot and Cai–Chen model-free methods in estimating reaction kinetics of metallurgical coke gasification was verified. The comparison between original and reconstructed kinetic curves judged the accuracy of the gained kinetic parameters. By means of gained nonisothermal kinetic results, the forecasting of kinetic curves in isothermal as well as nonisothermal conditions was performed. In this work, new kinetic equations were presented and applied to reproducing and forecasting kinetic curves.

Recovery of calcium sulfide from Tunisian phosphogypsum and olive mill wastewaters: a thermogravimetric and kinetic study

Large amounts of phosphogypsum (PG) and olive mill wastewaters (OMW) are rejected regularly in the environment. This paper deals with the valorization of both PG and OMW from Tunisia in order to recover calcium sulfide. It consists in studying the reduction of the former using the latter as a source of carbon, in nitrogen atmosphere with or without H2O vapor. Experiments were carried out by thermogravimetry in non-isothermal mode, and the solids were identified by X-ray diffraction. Raw (OMWR) and preheated samples (OMWP) of OMW were used, and the PG over OMW mass ratio was varied to find the stoichiometric proportion of the reaction between CaSO4 and carbon. It was found that in pure N2 atmosphere the use of OMW as a carbon source allows to significantly reduce both the onset reduction temperature and the reduction temperature interval: the PG reduction takes place in the temperature range of 600–750 °C (instead of 750–1080 °C with pure carbon) leading to CaS formation. Utilizing Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Kissinger, Satava-Sestak and master plots methods, activation energies, pre-exponential factors and the mechanism models of the reduction reaction were determined. The best models for PG + OMWP at 1.42 mass ratio and PG + OMWR at 0.23 mass ratio mixtures are Avrami-Erofeev A3 and A2 mechanisms, respectively. The kinetic models corresponding to the latter mixtures are: $$\frac{{{\text{d}}\alpha }}{{{\text{d}}t}} = 2.68~ \times 10^{{13}} {\text{~exp}}\left( { - \frac{{242.70~ \times 10^{3} }}{{RT}}} \right) \times 3\left( {1 - \alpha } \right)\left( { - \ln \left( {1 - \alpha } \right)} \right)^{{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}}}$$ and $$\frac{{{\text{d}}\alpha }}{{{\text{d}}t}} = 1.32~ \times 10^{{12}} ~\exp \left( { - \frac{{214.92~ \times 10^{3} }}{{RT}}} \right) \times 2\left( {1 - \alpha } \right)\left( { - \ln \left( {1 - \alpha } \right)} \right)^{{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}}}$$ , respectively. In wet atmosphere, the conversion rate of this reaction decreases by about 16% and the determined activation energies in that atmosphere were higher than in pure N2 one, supposing that the reduction reaction was influenced negatively by the wet atmosphere.

Thermogravimetric characteristics and kinetics of herb residues catalyzed by potassium carbonate

Thermal conversion technology of Chinese herb residues (CHR) becomes one of the most promising technologies in the large-scale clean utilization of herb residues due to its short process and high efficiency. In this study, non-isothermal thermogravimetric analysis of CHR samples without and with K2CO3 (5%K- 9%K) was implemented at 300−1125 K and the heating rates of 10−40 K/min. A model-free Starink method was applied to evaluate the thermal decomposition behavior and apparent activation energy (Eα) values. The estimated average activation energy decreases from 206.3 kJ/mol of raw CHR to 143.8–160.6 kJ/mol of CHR with K2CO3. K2CO3 catalysts significantly promote the catalytic pyrolysis reaction of the hemicellulose and cellulose of CHR samples at the main devolatilization stage from 425 K to 700 K with over 82.02 % mass loss. The pyrolysis temperature of the raw CHR is higher than traditional lignocellulosic biomass without decoction. By using the generalized master-plots method, it was found that the CHR pyrolysis could be described by a modified Dn-Jader model, but values of n and A tend to change measurably with heating rates for the CHR samples with catalysts due to the remarkably catalytic effect of K2CO3.

Evaluation of reaction mechanisms and emissions of oily sludge and coal co-combustions in O2/CO2 and O2/N2 atmospheres

Oxy-fuel combustion technology presents promising potential for the thermal disposal of hazardous waste to alleviate the global greenhouse effect on the environment and human well-being. In this study, the co-combustion reaction mechanisms and cleaner and efficient performances of oily sludge (OS) and coal in the oxy-fuel (O2/CO2) and air (O2/N2) atmospheres were characterized. With O2 concentration of 21% and at 20 °C/min, the ignition and burnout temperatures of the OS combustion were slightly worse in the oxy-fuel (403 and 531 °C) than air (407 and 535 °C) atmosphere. The rising O2 concentration increased the comprehensive combustion characteristic index from 1.11 × 10−7 to 4.29 × 10−7 in the air atmosphere and 1.02 × 10−7 to 4.10 × 10−7 in the oxy-fuel atmosphere. Based on the master-plots method, the three combustion stages of light oil, heavy oil, and fixed carbon were best described by the three-dimensional diffusion, interfacial reaction, and random nucleation growth models, respectively. The reaction mechanisms were independent of heating rate, O2 concentration, and atmosphere type. The co-combustion interaction between 70% OS and 30% coal reduced NO and SO2 emissions. Our findings can provide new insights into achieving their cleaner and more efficient co-combustion performance and its operational optimization.

Pyrolysis kinetic study of cathode material derived from spent lithium ion batteries (LIBs): Comparison of different models

ABSTRACT Separating cathode material and Al foil from spent lithium-ion batteries (LIBs) is a critical step for LIBs recycling. As compared to chemical dissolving and decomposition, the pyrolysis pretreatment is an alternative and simple method. In this work, the pyrolysis kinetics of cathode material were comparatively studied using various isoconversional methods, including Flynn-Wall-Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose, Starink, Tang, and Boswell. The thermal degradation mechanism was investigated by the Coats-Redfern (CR) and master-plot methods as well. The thermogravimetric analysis revealed that cathode material decomposition could be divided into three stages with mass losses of 1.51%, 0.787%, and 0.449%, respectively. Activation energy (Eα) calculated using the six model-free methods showed a similar trend, gradually increasing as the degree of conversion (α) increased from 0.001 to 0.009, and then significantly elevating. The FWO method gave the best fitting and Eα values first increased from 12.032 to 24.433 kJ·mol−1 with α elevating from 0.001 to 0.009, then increased further to 43.187 kJ·mol−1. Both CR and Criado methods indicated that the degradation of cathode material can be explained by the diffusion models. Implications: The rapid growth in the production and consumption of lithium-ion batteries (LIBs) for portable electronic devices and electric vehicles has resulted in an increasing number of spent LIBs. Thermal treatment offers advantages of high-efficiency and simple operation. Understanding the thermal process of spent LIBs and probing its kinetic are significant for the large-scale treatment. Through this study, it will be significant for the reactor designing and optimizing in practice.

Influencing mechanism of zinc mineral contamination on pyrolysis kinetic and product characteristics of corn biomass

The metal mineral has a complex influence on the thermal decomposition of biomass due to the sophisticated structure of biomass and parallel reactions. Therefore, the influencing mechanisms of metal minerals on biomass decomposition kinetic expressions needed to be thoroughly investigated. In this study, the decomposition of the three major components of biomass was considered separately. The iso-conversional method and integral master-plots method based on thermogravimetry were firstly introduced to explore the kinetic model changes after the introduction of zinc mineral. The thermogravimetric results showed that the presence of zinc mineral had discrepant influences on different biomass components, demoting the fragmentation of hemicellulose while promoting cellulose degradation. In the kinetic analysis, the presence of zinc mineral, the activation energy of three pseudo-components (91.90, 184.64 and 210.91 kJ mol−1) increased to 178.84, 299.05, and 359.45 kJ mol−1, respectively. The kinetic models were altered from 2.0-order reaction (F2.0) for hemicellulose, random nucleation (A1.8) for cellulose, and 2.3-order reaction (F2.3) for lignin to F2.8, F3.0, and F3.2, respectively. This indicated that the zinc mineral was beneficial to the occurrence of multimolecular repolymerization of the primary degradation products. In products analysis, the increment of biochar yields and the C4–C5 products of cellulose (especially furfural) in metal-polluted biomass pyrolysis were detected, which confirmed the simulated reaction mechanisms. The obtained results are expected to provide a mechanism reference to practical applications of metal-contaminated biomass.

Isoconversional analysis of kinetic pyrolysis of virgin polystyrene and its two real-world packaging wastes

In present work, two polystyrene packaging wastes of expanded polystyrene (EPS) foam and Yakult polystyrene milk bottle (YPS) along with pure polystyrene (PS) have been subjected to high-temperature nitrogen pyrolysis experiments under four heating rates of 5, 10, 15 and 20 K min−1. A comparison among these samples in terms of pyrolysis features and specific decomposition temperatures has been made, and EPS tends to be the most readily to undergo pyrolysis while YPS appears to be the most thermally stable. Based on thermogravimetric data, kinetic analysis has been systematically performed using various isoconversional methods. The calculations show that the activation energies calculated over the whole pyrolysis range are slightly different among the six temperature-integral methods, but the temperature-differential Friedman method has given rather distinct activation energies. The activation energies over the whole pyrolysis process are mass conversion-dependent for three samples and the activation energy averaged is the highest for YPS, followed by pure EPS and then EPS. A method combining master-plots method and differential composite method has been attempted to search the most suitable reaction models and chemical reaction order-based F0.58, F0.61 and F1.14 are found to be the most suitable reaction models for describing pyrolysis of PS, EPS and YPS, respectively. With the Coats–Redfern method, the mass-conversion curves along with its differential curves have been simulated, yielding very satisfactory performances for three polystyrene samples. In addition, thermodynamic functions such as the changes of entropy, enthalpy and Gibbs free energy during waste pyrolysis processes are also considered.

Pyrolysis Behaviors and Reaction Mechanisms of Coal Slime: A Study Based on TG-FTIR and PY-GC/MS

With the increase of washing raw coal, the rapid increase of coal slime (CS) production has become an urgent environmental problem. The main purpose of this work is to investigate the pyrolysis behavior and product distribution of CS by using thermogravimetric analyzer coupled to Fourier transform infrared spectroscopy (TG-FTIR) and Pyrolyzer-gas chromatography/mass spectrometry analysis (Py-GC/MS). The results showed that the pyrolysis of CS can be divided into three stages. The maximum weight loss of CS occurred in the main devolatilization stage at 178-680 oC. The pyrolysis kinetic mechanism of CS was predicted to be f(α)=(1-α)5.4 via the master-plots method. The increase of inorganic minerals significantly increased the order of CS pyrolysis reaction, indicating that minerals have a great influence on pyrolysis chemical reaction. Compared to raw coal, the alkene contents decreased significantly, while the contents of CO2 and aromatics increased significantly, illustrating that the minerals in CS promoted polymerization and cyclization reactions of alkene as well as the formation of macrocyclic aromatic hydrocarbons in CS tar. This study provided theoretical and practical guidance on efficient thermochemical conversion and utilization of CS.