Non-isothermal Thermogravimetric Analysis Research Articles

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.

Organic and Inorganic Modified Montmorillonite as a Scavenger of Formaldehyde in Modified Urea-Formaldehyde Composites

This research used montmorillonite (K10) modified with Hexadecyltrimethylammonium bromide (HDTMABr), and sulfuric acid (H2SO4). The samples are marked with MMT, OMMT for organic-modified montmorillonite, and AMMT for inorganic-modified montmorillonite. UF resin with a molar ratio FA/U = 0.8 was synthesized in situ with modified and unmodified MMT. X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), non-isothermal thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the MMT samples. The degree of activation was determined based on the measurement of specific surface area, which was determined by the Sears method. The sulfite method was used to determine free and released formaldehyde from synthesized urea-formaldehyde/montmorillonite (UF/MMT) composites. SEM analysis showed changes in the OMMT morphology and the formation of a hollow network, affecting the clay's absorption capacity. Measurement of the specific surface area shows that higher values were obtained for AMMT (183 m2/g) compared to OMMT (13.5 m2/g). Despite that, the free and released formaldehyde amount was 0.06% and 4.6% for UF/AMMT and 0.1% and 1.0% for UF/OMMT. The larger interlayer spacing and hydrophobic nature of OMMT make it an effective barrier within the UF resin matrix.

Kinetic study on the thermal decomposition of iron (II) sulfate using a global optimization approach

The thermal decomposition of sulfates is a major intermediate reaction in oxidizing roasting processes associated with metal sulfides. The optimization of iron (II) sulfate could contribute to lowering processes’ temperatures in complex systems. The present work presents the experimental and modeling results of the thermal decomposition of iron (II) sulfate heptahydrate. The investigation was first based on thermodynamic simulations followed by non-isothermal thermogravimetric analysis. The modeling technique consisted of differential equations formulated to describe each decomposition step individually, with the kinetic parameters estimated using particle swarm optimization (PSO). Using this modeling methodology over a graphical method is advantageous as it can simulate reactions that may occur simultaneously. The modeling succeeded in dehydration and desulfation steps, with an overall R2 value of 0.99. The activation energies and apparent reaction order associated with the dehydration steps were 53.3kJ.mol−1/n=1.65, 88.8kJ.mol−1/n=1.12, and 124kJ.mol−1/n=2.0 for FeSO4.7H2O, FeSO4.4H2O, and FeSO4.H2O, respectively. The desulfation steps were associated with higher activation energy values. In that case, 184kJ.mol−1 and 264kJ.mol−1 for FeSO4 and Fe2(SO4)3, respectively. Regarding the apparent reaction order, both desulfation steps showed to be first-order reactions.

Thermokinetic study of tannery sludge using combustion and pyrolysis process through non-isothermal thermogravimetric analysis

Sludge from the tannery is produced in enormous amount. This work has investigated the thermal analysis behaviour of the tannery sludge by use of the thermogravimetric analysis (TGA). The TGA experiments is carried out in both air and nitrogen environment at the varied heating rates of 5, 10, 20 and 40 °C/min from the temperature range of 30–900 °C. In the assessment of kinetic parameters, the model fitting (Combined kinetics) method was employed. It was investigated that thermal degradation of the tannery sludge sample occurred in three stages. Majorly the conversions were observed in stage II for both in air and nitrogen environment. The activation energy (Ea) value for the combustion is 165.9 kJ/mol while for the pyrolysis the Ea value is obtained as 65.2 kJ/mol from the conversion range between 0.2 and 0.8 which is a promising approximation supported by a strong R2 value of 0.9719 and 0.93 for combustion and pyrolysis respectively. It is estimated from the master plots that six ideal models A1/2, A1/3, A1/4, F3, F4 and D5 were probably in approximation with the linear fitted data for both air and nitrogen. Various thermodynamic parameters which include the ΔH, ΔG and ΔS are also complimented that indicates the formation of activated complex and non-spontaneity of the reaction. The detailed thermokinetic study of the tannery sludge in combustion and pyrolysis offers a novel approach to understanding how this waste material decomposes under different temperature conditions. This holistic perspective contributes valuable insights into waste management practices, environmental impacts, resource recovery, and process optimization within the leather industry. Furthermore, the optimization of leather production processes on a large scale can minimize waste generation and enhance energy efficiency, strengthening the competitiveness and sustainability of the leather industry.

Study of effect of dibenzoylmethane on thermal stability of PVC films stabilized with magnesium and zinc pentaerythritates

Static and dynamic thermal analysis of the destruction of PVC fi lms, as well as isothermal and non-isothermal thermogravimetric analysis (TGA) of PVC films stabilized with magnesium and zinc pentaerythritates with the addition of dibenzoylmethane as a synergistic additive were carried out.

Pyrolysis of high-density polyethylene: Degradation behaviors, kinetics, and product characteristics

Pyrolysis is a promising technology for converting plastic waste into valuable raw materials while offering a potential solution to the global plastic pollution crisis. In this study, the thermal pyrolysis of high-density polyethylene (HDPE) is investigated in a drop tube reactor under nearly isothermal conditions. The impact of reaction temperature and gas/volatile residence time on carbon conversion and product distribution is examined across a range of 500–900 °C and 3.6–32.2 s, respectively. Non-condensable gas products detected by online mass spectrometry are H2, CH4, C2H4, C2H6, C3H6, and C3H8. At elevated temperatures and prolonged residence time, H2 yield reaches as high as 8.6 wt% of the initial HDPE mass due to intensified cracking reactions of C2–C3 hydrocarbons and long-chain aliphatic compounds. Consequently, pyrolysis tars consist mainly of polycyclic aromatic hydrocarbons (PAHs) with 5–7 rings, accompanied by visible coke deposition within the reactor. HDPE decomposition to volatiles is an endothermic process and it is complete at a temperature between 492 °C and 525 °C, depending on the heating rate employed, from non-isothermal thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) measurements. The thermal degradation of HDPE pellets follows the two-dimensional nucleation growth model for conversion levels up to 0.8 with an apparent activation energy of 259–270 kJ/mol and a pre-exponential factor of 4.83 × 1017–1.37 × 1019 min−1, determined from various isoconversional methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink, along with Criado's master plots. These findings provide valuable insights into optimizing process parameters and refining reactor design for pyrolysis, which can be integrated with gasification and reforming processes to enhance hydrogen production on a larger scale.

Co-pyrolysis of poly (lactic acid) and sugar cane bagasse: Kinetic and thermodynamic studies

For the purpose of investigating the effect of biomass on pyrolysis degradation of plastic wastes, poly (lactic acid) (PLA) has thus been attempted in present work to study the influence of sugar cane bagasse (SCB) on its pyrolysis behaviors and kinetic paramerizations. PLA/SCB samples after prepared by using a suspension blending method have been co-pyrolyzed in nitrogen by non-isothermal thermogravimetric analysis. After adding SCB biomass, the initial pyrolysis degradation temperatures and melting point of PLA are found to have declined substantially. Using pyrolysis results, activation energies of Ea are isoconversionally calculated by applying differential Friedman, integral Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Starink and Vyazovkin-Dollimore methods, resulting in 113.7 ∼ 141.7, 101.3 ∼ 140.4 and 79.8 ∼ 210.1 kJ/mol for the PLA blends with 10, 20 and 30 mass% of SCB, respectively. Two approaches based on the Friedman differential equation along with integral methods are attempted for determining pre-exponential factor lnA and pyrolysis reaction model f(α). With these modeled results, the experimental curves are matched successfully. Moreover, thermodynamic parameters including ΔH, ΔG, and ΔS values were calculated for the entire pyrolysis process of three blends. The findings acquired from present study are of significance for advancing the design of any relevant pyrolysis reactor for PLA/biomass wastes.

Effect of copper content on the pyrolysis process of organic components in waste printed circuit boards: Based on experimental and quantum chemical DFT simulations

In recent years, scientists have become increasingly concerned in recycling electronic trash, particularly waste printed circuit boards (WPCBs). Previous research has indicated that the presence of Cu impacts the pyrolysis of WPCBs. However, there may be errors in the experimental results, as printed circuit boards (PCBs) with copper and those without copper are produced differently. For this experiment, we blended copper powder with PCB nonmetallic resin powder in various ratios to create the samples. The apparent kinetics and pyrolysis properties of four resin powders with varying copper concentrations were compared using nonisothermal thermogravimetric analysis (TG) and thermal pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). From the perspective of kinetics, the apparent activation energy of the resin powder in the pyrolysis reaction shows a rise (0.1＜α＜0.2)-stable (0.2＜α＜0.4)-accelerated increase (0.4＜α＜0.8)- decrease (0.8＜α＜0.9) process. After adding copper powder, the apparent activation energy changes more obviously when (0.2＜α＜0.4). In the early stage of the pyrolysis reaction (0.1＜α＜0.6), the apparent activation energy is reduced, but when α=0.8, it is much higher than that of the resin sample without copper. Additionally, it is discovered using thermogravimetric analysis and Py-GC/MS that copper shortens the temperature range of the primary pyrolysis reaction and prevents the creation of compounds containing bromine. This inhibition will raise the temperature at which compounds containing bromine first form, and it will keep rising as the copper level rises. The majority of the circuit board molecules have lower bond energies when copper is present, according to calculations performed using the gaussian09 software, which promotes the pyrolysis reaction.

Investigation of Combustion and NO/SO2 Emission Characteristics during the Co-Combustion Process of Torrefied Biomass and Lignite.

This paper investigates the combustion characteristics and pollutant emission patterns of the mixed combustion of lignite (L) and torrefied pine wood (TPW) under different blending ratios. Isothermal combustion experiments were conducted in a fixed bed reaction system at 800 °C, and pollutant emission concentrations were measured using a flue gas analyzer. Using scanning electron microscopy (SEM) and BET (nitrogen adsorption) experiments, it was found that torrefied pine wood (TPW) has a larger specific surface area and a more developed pore structure, which can facilitate more complete combustion of the sample. The results of the non-isothermal thermogravimetric analysis show that with the TPW blending ratio increase, the entire combustion process advances, and the ignition temperature, maximum peak temperature, and burnout temperature all show a decreasing trend. The kinetic equations of the combustion reaction process of mixed gas were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic equations. The results show that the blending of TPW reduces the activation energy of the combustion reaction of the mixed fuel. When the TPW blending ratio is 80%, the activation energy values of the mixed fuel are the lowest at 111.32 kJ/mol and 104.87 kJ/mol. The abundant alkali metal ions and porous structure in TPW reduce the conversion rates of N and S elements in the fuel to NO and SO2, thus reducing the pollutant emissions from the mixed fuel.

Thermal Decomposition and Combustion Analysis of Malaysian Peat Soil Samples Using Coats Redfern Model-free Method

This research investigates the thermal decomposition behaviour of Malaysian peat soil through thermogravimetric analysis at varying heating rates. The study aims to analyse the thermal kinetics of decomposition for distinct peat soil types under inert and oxidative atmospheres while considering the role of available oxygen. The investigation encompasses virgin and agricultural peat, employing a non-isothermal thermogravimetric analysis technique to evaluate thermal decomposition characteristics and compute kinetic parameters using the Coats Redfern model-free approach. The pyrolysis profiles reveal three primary stages: moisture evaporation (30–180°C), organic component decomposition (200–500°C), and mineral decomposition (600–800°C). Virgin peat experiences a 43% mass loss during pyrolysis, while agricultural peat shows a 46% mass loss, emphasising insights into thermal behaviour and consistent decomposition patterns across peat types. Combustion profiles exhibit three main stages: dehydration (30–180°C), oxidative pyrolysis transforming organic matter into volatiles and char (200–300°C), and subsequent char oxidation (300–500°C). The study determines average activation energy trends, measuring 14.87 kJ/mol for virgin peat and 5.37 kJ/mol for agricultural peat under an inert atmosphere, and 28.89 kJ/mol for virgin peat and 36.66 kJ/mol for agricultural peat under an oxidative atmosphere. The research introduces an innovative two-step reaction model elucidating peat thermal decomposition kinetics (excluding dehydration), including a discussion on the impact of oxygen availability on kinetic parameters. These findings essential peat fire smouldering modelling, contributing to peat combustion behaviour for effective strategies to reduce peat fire risks.

Thermal Degradation Analysis of Mamoncillo (<i>Melicoccus bijugatus</i>) Waste: Thermal Behaviors, Kinetics, and Thermodynamics

This research studied the thermal conversion characteristics, kinetics, and thermodynamics of mamoncillo peels and seeds using non-isothermal thermogravimetric analysis. Kinetic analysis was performed using the Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Starink, and Friedman methods. The reaction kinetic models were obtained by means of the master-plots method for 18 different empirical reaction models, calculating the enthalpy, Gibbs free energy, and entropy as thermodynamics parameters. It was found that the average activation energy for mamoncillo peels and seeds was 238,71 and 197,60 kJ/mol, respectively. The frequency factor was found to be between 109 and 1031 s-1 for mamoncillo peels and between 109 and 1034 s-1 for mamoncillo seeds. The average values of DH and DG were also found to be 233,83 and 192,81 kJ/mol and 164,84 and 162,10 kJ/mol for mamoncillo peels and seeds, respectively. The reaction kinetic models regarding the thermal decomposition of mamoncillo peels were found to be described by the contracting cylinder (R2) and third-order (F3) models, while those for mamoncillo seeds can be described by the second-order (F2) and contracting sphere (R3) models. It was concluded that the pyrolysis process of mamoncillo waste can be described by a complex reaction mechanism, and that these wastes have thermal properties with the potential to produce bioenergy.

Thermal Decomposition Kinetics of Clinochlore at High Temperature and Its Implications

Abstract The dehydration kinetics of clinochlore were performed using a non-isothermal thermogravimetric analysis under a dynamic nitrogen atmosphere at ambient pressure. Clinochlore, with a grain size of 5–10 μm, was analyzed using heating rates of 2, 5, 10, 20, and 40 K/min at temperatures of up to 1260 K. Thermogravimetric data of clinochlore at different heating rates were modeled using the Kissinger method, Flynn-Wall-Ozawa method, and Coats-Redfern method. The dehydration of clinochlore is ascribed to the decomposition of brucite and talc layers. The dehydration temperature of the brucite layer is 730–920 K, which corresponds to a two-dimensional phase boundary model (R2) with an activation energy of 214.94 ± 7.79 kJ/mol and a pre-exponential factor of 12.52 ± 0.62 min−1. The dehydration temperature of the talc-like layer is 960–1140 K, which follows a two-dimensional diffusion model with an apparent activation energy of 419.49 ± 23.62 kJ/mol and a pre-exponential factor of 19.97 ± 1.76 min−1. Combined with the parameters obtained in this study, the fast dehydration of clinochlore can trigger earthquakes in the subduction zone.

The Structure-Function Relationship of Branched Polyethylenimine Impregnated over Mesoporous Carbon Aerogels: An In-Depth Thermogravimetric Insight.

We present a comprehensive thermogravimetric analysis (TGA) of polyethylenimine (PEI)-impregnated resorcinol-formaldehyde (RF) aerogels. While numerous studies focus on PEI-impregnated SBA, RF materials have been less examined, despite their interest and specificities. As most articles on PEI-impregnated porous materials follow typical experimental methods defined for SBA, particularities of RF-PEI materials could remain unheeded. The design of nonisothermal TGA protocols, completed with nitrogen isotherms, based on the systematic filling of the matrix delivers a fundamental understanding of the relationship between the structure and function. This study demonstrates (i) the competition between the matrix and PEI for CO2-physisorption (φ) and CO2-chemisorption (χ), (ii) the hysteresis ([Formula: see text]) of CO2 capture at low temperature attributed to the kinetic (K) hindrance of CO2 diffusion (D) through PEI film/plugs limiting the chemisorption, and (iii) the thermodynamic (θ) equilibrium limiting the capture at high temperature. At variance with SBA-PEI materials, the first layers of PEI in RF are readily available for CO2 capture given that this matrix does not covalently bind PEI as SBA. A facile method allows the discrimination between physi- and chemisorption, exhibiting how the former decreases with PEI coverage. The CO2 capture hysteresis, while seldom introduced or discussed, underlines that the commonly accepted operating temperature of the "maximum capture" is based on an incomplete experiment. Through isotherm adsorption analysis, we correlate the evolution of this maximum to the morphological distribution of PEI. This contribution highlights the specificities of RF-PEI and the advantages of our TGA protocol in understanding the structure/function relationship of this kind of material by avoiding the typical direct applications of SBA-specific protocols. The method is straightforward, does not need large-scale facilities, and is applicable to other materials. Its easiness and rapidness are suited to high-volume studies, befitting for the comprehensive evaluation of interacting factors such as the matrix's nature, pore size, and PEI weight.

Thermo-kinetic Study of Genetically Different Carbon-Source Materials.

A nonisothermal thermogravimetric analysis (TGA) technique was applied to determine the devolatilization kinetic parameters of completely different genesis samples of four groups: coal, biomass, lignite, and petcoke. The physical and chemical characteristics were determined using the proximate and ultimate analysis and the ash composition profile using the X-ray fluorescence method. Heating rates of 10, 15, and 20 °C/min were used in the temperature range of 25-1000 °C during the slow pyrolysis under an inert gas atmosphere. A widely used and proposed first-order Coats-Redfern kinetic model was applied, which showed the highest values of activation energies (Ea) for the petcoke sample from 57.17 to 67.58 kJ/mol at three different heating rates, while the lignite sample represented the lowest Ea values between 12.84 and 16.03 kJ/mol. The thermo-kinetic behavior was explained based on the catalytic effect of the ash composition profile, morphology, and structure of the substances determined using different analytical techniques. For the TGA process, the application of scanning electron microscopy, Fourier-transform infrared spectroscopy, etc., for the physiochemical analysis of the four genetically different carbon-source materials represented the novelty of the present work.

Interphase in polymer-based nanocomposites: Polyoctenamer – Single-walled carbon nanotubes

A detailed and critical analysis of the non-isothermal thermogravimetric analysis of polyoctenamer-single wall carbon nanotube, is presented. The thermogravimetric data were obtained under an inert atmosphere (nitrogen) on polyoctenamer- single wall carbon nanotube nanocomposites loaded by different amounts of nanofiller (up to 10 % wt. single wall carbon nanotube), at various heating rates ranging from 5 to 40 °C/minute.The research focuses on the identification of the polymer-nanofiller interphase, including the detailed dissemination between the interface and interphase. The manuscript aims at the information that can be extracted from the recorded thermograms as well as from the derivatives of the thermograms with respect to the temperature. The detailed analysis of the temperature at which x% of the mass is volatilized, TX%, and of the residual mass fraction at high temperatures (850 °C and 950 °C) provide qualitative support for the presence of interphase.The research demonstrated that the derivatives of the thermograms versus temperature have a better resolution than “standard” thermograms. The derivative of the thermograms provides qualitative information about the formation of an interphase. A model for the degradation of the nanocomposites is proposed by assuming that the dependence of the inflection temperature on the composition of the nanocomposite obeys a Fox-like dependence, where the bulk polymer and the polymer trapped within the interphase are considered as a blend of two miscible polymers.

Kinetics of maize cob and bean straw pyrolysis and combustion

Kinetic studies are important for the design and optimisation of thermochemical processes. This study involved analysis of the pyrolysis and combustion behaviour of the agricultural residues (bean straw and maize cob) by non-isothermal thermogravimetric analysis. Increasing the heating rate from 10 to 40 K min−1 during both combustion and pyrolysis increased the degradation rate of both feedstocks and the gaseous yields of H2O, CO and CO2. The activation energies determined by the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods varied which reveals that the pyrolysis and combustion of these agricultural residues are complex processes involving multiple reactions. The average activation energy of maize cob and bean straw were 214.15 and 252.09 kJ mol−1 for pyrolysis and 202.26 and 165.64 kJ mol−1 for combustion, respectively. The order of reaction ranged between 9.0-10.3 and 6.3–13.3 for both feedstocks in combustion and inert environments, respectively. Modelled data is important to enable the optimisation of reactor design for pyrolysis and combustion for energy generation from agricultural residues.

Assessment of the Influence of Saffron Pollen and Saffron Pollen/Rutin Microcapsules on Thermal and Oxidative Stability of Edible Oil: Thermogravimetric Study

Nowadays, the demand to find natural systems as antioxidants or additives applicable in the food industry without any manipulation or surface engineering is increasing. Accordingly, this study aimed to find a potential natural, eco-friendly, low-cost, and safe antioxidant. Therefore, saffron pollen (SP) and rutin (Ru) were chosen as two potential antioxidants, and their antioxidant activity in sunflower oil (SO) was evaluated by nonisothermal thermogravimetric analysis (TGA/DTA). tert-Butylhydroquinone (TBHQ) was used as an already-proven antioxidant and positive control. The antioxidant activity of rutin-loaded saffron pollen microcapsules was also evaluated. According to the TGA results, SP enhanced the oxidative stability of SO compared to TBHQ. In contrast, its thermal stability was significantly lower than that of TBHQ and Ru. Based on the results of the mass increase in TGA, the antioxidant effect of SP was significantly higher than Ru. These prove that SP can function as a natural antioxidant system in edible oil.

Physicochemical Characterization and Chemical Reactivity of Biochar from Pyrolysis of Dried Distiller’s Grains with Solubles (DDGs)

ABSTRACT Biomass utilization has attracted great attention for decades, and the dried distiller’s grains with solubles (DDGs) is an important source which is the by-product of brewing industries, as fermented from raw biomass such as rice, wheat and sorghum. Currently, there are a few studies on the kinetics and thermodynamics of distiller’s grains biomass. Therefore, the physicochemical characterization, kinetic and thermodynamic analyses of DDGs and DDGs-biochar were studied. The characterization results confirmed that DDGs had high volatile matter (81.6%) and higher heating value (21.3 MJ kg−1). The pyrolysis kinetics of DDGs and DDGs-biochar at four heating rates of 5, 10, 20 and 40 K min−1 were investigated by non-isothermal thermogravimetric analysis. The isoconversional method such as Kissinger-Akahira-Sunose (KAS), analysis showed that the effective activation energy varied with the change in the conversion rates. For DDGs, it was 122–159 kJ mol−1 (α: 0.1–0.2), 160 ± 6.20 kJ mol−1 (α: 0.20–0.75) and 179–194 kJ mol−1 (α > 0.75), corresponded to thermal decomposition of hemicellulose, cellulose and part of lignin, and remaining lignin respectively; as to combustion of DDGs-biochar, it was 152 to 60.1 kJ mol−1 (α: 0.1–0.9) indicated that some of the more complicated structures in DDGs had been carbonized, making as-obtained biochar easier to burn owing to the lower activation energy. The changes in enthalpy, Gibbs free energy and entropy of DDGs and DDGs-biochar were calculated, and the results were helpful to evaluate the conversion efficiency and technical feasibility of DDGs pyrolysis and DDGs-biochar combustion processes.

Kinetics of combustion of lignocellulosic biomass: recent research and critical issues

Predicting biomass combustion at temperatures of practical interest requires kinetic expression robust and reliable over a large temperature range.The present work examines experimental works on combustion kinetics of lignocellulosic biomass published since 2015 and reports the experimental methods used and the kinetic parameters obtained therein. The most common experimental strategy, used in 39 referenced works, was non-isothermal thermogravimetric analysis, yet the kinetic parameters obtained varied by order of magnitude.The large variability of the kinetic parameters found in literature cannot be only explained by the feedstock heterogeneity or the different data analysis methods. One possible and apparently neglected source of error lies in the fact lignocellulosic biomasses are complex materials, constituted by different components, thus thermogravimetric curves are the resultant of multiple and partly overlapping stages of mass loss. Kinetic analysis in this case easily generates errors. Another criticality that the work wants to emphasize is the fact that biomass pyrolyses, burns and even thermally anneals throughout a TGA experiment. These progressive structural changes are a further problem for application of conventional kinetic analysis methods.Altogether, it can be concluded that it is difficult to obtain from conventional TGA analysis reliable kinetic expressions of biomass combustion to be used for boilers modelling. For complex materials like biomass, it is recommended to adopt expert-case sensitive approaches. As an example, the case of walnut shells combustion is presented. For this material, four components with different combustion reactivity have been identified and simplified single rate kinetics are proposed according to the temperature interval of interest.

Mechanistic investigation of pyrolysis kinetics of water hyacinth for biofuel employing isoconversional method

The current study employs non-isothermal thermogravimetric analysis to analyze the thermal degradation behavior of water hyacinth (WH), with the primary goal of determining the kinetic triplet. The pyrolysis of water hyacinth achieved approximately 80% thermal degradation during three phases of breakdown at temperatures ranging from 30 to 900 °C. The activation energy of feedstock breakdown was calculated using four different model-free approaches i.e., Flynn-Wall- Ozawa (FWO), Starink, Friedman, and Kissinger- Akahira-Sunose (KAS), with mean values ranging from 251.33 to 298.48 kJ/mol inside the conversion band of 0.15–0.75. The Master plot results depicted that for conversion (α) ≤ 0.5, the biomass degradation followed a two-dimensional process of diffusion. For α ≥ 0.5, the response, however, is adequately described by growth processes and nucleation. The values of excitation energy estimated using isoconversional techniques were also utilized to determine various thermodynamic parameters. From the thermodynamic study, the mean value of ΔH was 293.66 kJ/mol, suggesting that the generation of activated complex is simpler since the potential energy barrier is lower. A high ΔS value indicates increased reactivity and less time required to synthesize the activated compound. In conclusion, the characterization and kinetic analyses of biomass reveal their potential as pyrolysis feedstock.