Isoconversional Models Research Articles

Non-isothermal crystallization kinetics investigation of different zones at the joining area of a bulk metallic glass welded by friction stir spot welding (FSSW)

The connection cross section of a Ti-based bulk metallic glass welded with friction stir spot welding method, was investigated using Vickers micro-hardness and SEM. Regarding the results, four zones were detected at the connection site. The crystallization kinetics of the four zones identified at the joining area, was studied using the DSC at heating rates of 10–50 K min−1. Apparent activation energy (Ec), frequency factor (A) at characteristic temperatures (Tg, Tx1, Tp1) and local activation energy (Ec(α)) variations of different zones during the first crystallization transformation were calculated by isokinetics and isoconversional models. The crystallization conversion function for each zone was determined using the Sestak-Berggren equation. Sub-tool tip stir zone (TSZ) showed the highest thermal stability. The thermo-mechanically affected zone (TMAZ) with the highest onset crystallization temperature (Tx1) has a higher thermal stability in comparison to sub-tool shoulder stir zone (SSZ) with the lowest thermal stability and base metal (BM).

Kinetic Modeling of Citrullus Lanatus (Watermelon) Peel Using Thermo Gravimetric Analysis

AbstractThis work aims at the kinetic studies of the hydrochar produced from hydrothermal carbonization of citrulluslanatus(watermelon) peel. The hydrochar was prepared at optimized conditions regarding Carbon content, High Heating Value and Yield at experimental conditions of 210 °C and 1 h operation. The Watermelon peel hydrocharkineticswereinvestigated at heating rates of 5 °C${\text{mi}}{{\text{n}}^{ - 1}}$, 10 °C${\text{mi}}{{\text{n}}^{ - 1}}$, 15 °C${\text{mi}}{{\text{n}}^{ - 1}}$, & 20 °C${\text{mi}}{{\text{n}}^{ - 1}}$, through thermogravimetric analysis. Two iso-conversional models were applied to compute the kinetic parameters and pyrolysis behavior of hydrochar. The kinetic study using Kissinger-Akahira-Sunose (KAS) model revealed that for a conversion range of 0.1 to 0.8,the activation energy was observed to be in the range of 146 to 220 kJ/mol. Similarly, the activation energies estimated through Flynn-Wall-Ozawa (FWO) model also gave a similar range of kinetic energies from 147 to 219 kJ/mol. Moreover, higher pre-exponential factor values explained the convoluted structure of biomass. The regression coefficient (${R^{2\,}}$) for both the models is high and they have shown similar activation energies which confirms that the best reaction mechanism is predicted. This research helps in establishing an economical and efficient technology for producing clean bioenergy and useful chemicals.

Thermogravimetric kinetics of catalytic and non-catalytic pyrolytic conversion of palm kernel shell with acid treated coal bottom ash

The catalytic and non-catalytic pyrolytic conversion kinetics of palm kernel shell with untreated (as received) and H2SO4 treated coal bottom ash as catalyst were investigated in this study. The activation energy was determined using Flynn-Wall-Ozawa (FWO) kinetic model and distributed activation energy model (DEAM) isoconversional kinetic models. The study was conducted using thermogravimetric analysis at 10, 20, 30 and 50 °C/min heating rates. The activation energy (Ea) ranged from 145.7-228.3 kJ/mol and 142.1-274.2 kJ/mol for FWO and DEAM, respectively. The use of acid treated ash reduced the activation energy compared to the non-catalytic process while the untreated ash increased the activation energy.

Kinetic and Thermodynamic Evaluation of Pyrolysis of Plant Biomass using TGA

Abstract The kinetic and thermodynamic analysis of the plant biomass waste of Banyan tree (Ficus Benghalensis) was carried out using thermo gravimetric analysis (TGA) at different heating rates of 10, 25 and 50°C min-1 under an inert atmosphere of nitrogen. Using iso-conversional models of Kissenger-Akahira-Sunrose (KAS) and Ozawa-Flynn-Wall (OFW), the average activation energy values were found to be of the range of 73.03 kJmol-1 and 79.74 kJmol-1, respectively. The application of Coats-Redfern method predicted that most appropriate mechanisms followed by thermal degradation of Banyan tree biomass are D5 and F3, based on diffusion and chemical reaction respectively, involving both exothermic and endothermic reactions for the temperature range under study. A kinetic compensation effect was found to follow the equation: lnA0=-4.1575+0.2042E. The Gibbs free energy value of ∼176.24 kJmol-1 and a difference of about ∼5 kJmol-1 between activation energy and enthalpy of the reaction indicate favorable product formation with considerable bio energy potential of Banyan tree biomass waste

KINETIC PARAMETERS STUDY FOR THE SLOW PYROLYSIS OF COFFEE RESIDUES BASED ON THERMOGRAVIMETRIC ANALYSIS

Thermal decomposition of coffee husks was investigated by thermogravimetric analyses. The proximate, ultimate and composition analyses were performed. Thermogravimetric tests were realized, the material was heated to 1173 K using five heating rates: 5, 10, 15, 20, 25 K min-1. The kinetic parameters were estimated using the methods of Kissinger-Akahira-Sunose and Friedman, the distributed activation energy model and the independent parallel reactions model. The isoconversional models of Kissinger-Akahira-Sunose and Friedman showed the dependence between determined values of activation energy and mass conversion, the activation energy values varied from 1437.39 to 199.22 kJ mol-1 for Kissinger-Akahira-Sunose and from 127.81 to 230.35 kJ mol-1 for Friedman model. The values of activation energy were determined for Miura-Maki method; varying from 137.39 to 199.22 kJ mol-1. The model of parallel and independent reactions showed the presence of six different reactions (with activation energy values varying from 42.0 to 214.2 kJ mol-1) occurring during coffee husks pyrolysis, indicating a complex reaction. Currently, works regarding the determination of kinetic parameters for coffee husks pyrolysis are not common. The present work is the first report using the model of parallel and independent reactions to estimate kinetic parameters for pyrolysis of coffee husks, a residue widely generated worldwide.

Influence of Cellulose Characteristics on Pyrolysis Suitability

Cellulose is the component that is in higher proportion in the biomass. It is also the component that requires the most activation energy for pyrolysis. Values in the range of 180-391 kJ mol -1 have been found in the literature. The dependence of the Activation Energy on the intrinsic cellulose characteristics (polymerization degree, crystallinity, crystal size) has been studied in different samples ( Eucalyptus globulus, Ulmus minor, Linun usitatissimun, Olea europaea, Robinia pseudoacacia, Populus alba ) and cellulose isolation methods. To describe the pyrolytic degradation of cellulose, Ozawa-Flynn-Wall kinetic method, among isoconversional models studied, seems to be the most appropriate. An acceptable quadratic relationship (R 2 >0.9) between the Ea values of the different cellulose samples with their corresponding degree of polymerization, crystallinity index and crystal size values has been found. Therefore, low crystallinity ( 2300) and low crystal size values (<10-10.5nm) are desired to obtain lower Ea values for cellulose pyrolysis.

Pyrolysis and combustion kinetics of Sida cordifolia L. using thermogravimetric analysis

Sida cordifolia L. (Sida) is an annual invasive plant that remains underutilized in Niger. The goal of this study was to characterize the thermal decomposition of Sida for its valorisation as a source of energy through thermogravimetric analysis (TGA). TGA was carried out under nitrogen and air atmospheres. Thus, five different heating rates were used as 10, 20, 30, 40, 50 °C min−1. Kinetic and thermodynamic parameters were determined by isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The results showed that the average activation energy (Ea) of Sida calculated by KAS and FWO in pyrolysis was found to be 74.74 and 80.74 kJ mol−1 respectively, while it was 51.08 and 58.91 kJ mol−1 in combustion respectively. Kinetic and thermodynamic parameters such as Ea, ΔH, ΔS, and ΔG obtained by KAS and FWO show that Sida is a remarkable feedstock for bioenergy.

Physicochemical characterizations, antimicrobial activity and non-isothermal decomposition kinetics of Cinnamomum cassia essential oils

ABSTRACTThe extraction of essential oils from Cinnamomum cassia bark and leaf was carried out by hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD). Chemical compositions of volatile compounds were determined by GC/MS, 1H-NMR and infrared spectroscopy analysis. The dominant constituents found in the essential oils were aromatic compounds (> 90%) including (E)-cinnamaldehyde (CAL) and (E)-cinnamyl acetate (CAC) as the major components. The thermogravimetry (TG) method was used to study thermal stability and volatilization of the oils at room temperature. The bark essential oils exhibited inhibitory effects against a bacterial strain, S. aureus and a yeast strain, S. cerevisiae at MIC value 200 µg/mL. The decomposition kinetic of the essential oils was studied via the isoconversional kinetic models using the TG data. Two the isoconversional models, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) were used to determine activation energies (Ea) for decomposition of the essential oils.

Slow pyrolysis of coffee husk briquettes: Characterization of the solid and liquid fractions

The objective of this study was to investigate the kinetics of the biomass and to determine the influence of temperature on the distribution and quality of the products of slow pyrolysis. Coffee husk briquettes were produced by densification and subsequently subjected to slow pyrolysis at different final temperatures of 623 K, 673 K and 723 K at a heating rate of 0.5 °C/min. The results of the TGA showed that the pyrolysis of coffee husks occurred mainly at temperatures between 400 K and 700 K. The activation energy values ranged from 104.90 kJ/mol to 345.2 kJ/mol for the Friedman model and from 70.4 kJ/mol to 288.8 kJ/mol for the FWO model. In the composition of the bio-oil, at higher pyrolysis temperatures, there was a greater production of phenolic compounds and nitrogen compounds. Lower temperatures promoted the greater formation of hydrocarbons and acetic acid. The energy content of the biochar did not differ with the increasing temperature, but the fixed carbon was slightly higher at 723 K. It was concluded that the TGA provided information on the kinetics of the coffee husk pyrolysis, making it possible to improve the conversion process of this waste into products. Both isoconversional models were effective in estimating the Ea of the pyrolysis process with good accuracy. High final pyrolysis temperatures improve the quality of bio-oil, producing bio-oil with smaller amounts of acidic compounds, and this bio-oil is desirable for use as fuels. In addition, the bio-oil contains numerous chemical compounds that can be extracted and used in value-added chemical products.

Intrinsic kinetics, thermodynamic parameters and reaction mechanism of non-isothermal degradation of torrefied Acacia nilotica using isoconversional methods

The objective of this work is to examine the suitability of torrefied biomass for bio-energy generation by investigating its physicochemical characteristics, kinetic and thermodynamic parameters as well as reaction mechanism during pyrolysis. Thus, torrefaction of Acacia nilotica was performed in a fixed bed reactor at 220, 250 and 280 °C, with constant residence time (40 min) and heating rate (15 °C/min). Pyrolysis of torrefied biomass obtained at 220 °C (T-220), 250 °C (T-250) and 280 °C (T-280) was performed using thermogravimetric analyzer at three different heating rate viz. 5, 10 and 15 K/min. Further, isoconversional models namely, Kissinger-Akahira-Sunose (KAS), Ozawa-Wall-Flynn (OWF), Friedman and Starink were employed to calculate the kinetic parameters (activation energy and pre-exponential factor) of raw and torrefied biomass. Using kinetic parameters obtained from KAS method, thermodynamic parameters (enthalpy, Gibbs free energy, and entropy) were calculated at a heating rate of 10 K/min. The activation energy for raw and T-220, T-250, and T-280 using KAS method were found to be 221.49, 241.58, 185.06, and 121.83 kJ/mol, respectively. The increase in activation energy of T-220 might be due to a higher percentage of cellulose content in it than raw biomass. Reaction mechanism during pyrolysis of raw and torrefied biomass was predicted using Criado method (Z-master plot). For raw biomass and T-220, diffusion models were followed; however, for T-250 and T-280, random nucleation models were dominant. Overall, results provide a deep understanding of kinetics and improved characteristics of torrefied biomass as good quality solid fuel.

Pyrolysis and kinetic behaviour of black gram straw using thermogravimetric analysis

ABSTRACT The present study aims to investigating the thermal behavior and pyrolysis kinetics of Black Gram Straw (BGS) degradation using thermogravimetric analyzer at three heating rates (20, 30 and 40°C/min). TGA results showed maximum decomposition took place in the temperature range of 180 to 380°C. Three different iso-conversional models Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink methods were applied on TGA results to calculate the kinetic and thermodynamic parameters. Average activation energies from FWO, KAS, and Starink methods were 172.96, 172.81, and 172.54 kJ/mol and pre-exponential factors ranged from 1010 to 1017 s−1 respectively. Differences between Eα and ∆H*values (~5 kJ/mol) showed the formation of the activation complex is being favored. The values of ∆G* and ΔS*varied from 166.99 to 167.01kJ/mol and −66.61 to 70.13J/mol, respectively. The above kinetics, thermodynamic data can be of massive benefit to modeling, designing and developing a suitable thermochemical conversion system of black gram stalk to energy carrier.

A kinetic study of roadside grass pyrolysis and digestate from anaerobic mono-digestion

The aim of this research is to evaluate the thermogravimetric behaviour of roadside grass and its digestate obtained from mesophilic anaerobic mono-digestion by quantifying its impacts on biomass composition and properties. Thermogravimetric measurements were conducted in a laboratory furnace under nitrogen flowrate of 100 mL/min in the temperature range from 35 to 800 °C at five different heating rates of 2.5, 5, 10, 15 and 20 °C/min. Friedman and Kissinger-Akahira-Sunose differential and integral isoconversional models were applied to determine the distributions of activation energies and modified pre-exponential factors per reacted mass (degree of conversion). The investigation demonstrated that anaerobic digestion of roadside grass can be used to generate biochar-richer material (with significantly greater yield of final residues after pyrolysis) with less energy required for subsequent pyrolysis in comparison with raw roadside grass.

Curing kinetics of chemically recyclable thermoset and their nanocomposites

In this work the role of the addition of barium titanate (BaTiO3) or multi-walled carbon nanotubes (MWCNT) on curing kinetics of the polyhexahydro-s-triazine (PHT) was investigated. The estimation of kinetic parameters triplet (activation energy, pre-exponential factor, and the reaction model) of PHT and its nanocomposites were made by isoconversional models. It is possible to state the conversion of the polyhemiaminal (PHA) into PHT polymer and all nanocomposites studied in this work is dominated by a single step according to the Vyazovkin method. The activation energy calculated by studying the cure kinetics for the chemical rearrangement of PHT polymer was 143 kJ/mol. Besides, the addition of BaTiO3 nanoparticles greater than 1.5 wt% and 0.86 wt% of MWCNT showed a catalytic effect on the cure reaction with respect to the neat polymer. Finally, the Avrami-Erofeev’s model proved to be the most suitable that represents the cure kinetics of PHT polymer and their nanocomposites.

Pyrolysis and Thermogravimetric Study to Elucidate the Bioenergy Potential of Novel Feedstock Produced on Poor Soils While Keeping the Environmental Sustainability Intact

This work focused on exploring the bioenergy potential of biomass produced on salt-affected soils by growing two types of grasses, namely Parthenium hysterophorus (carrot grass) and Pennesetum benthiumo (mott grass), without using fertilizers or pesticides. The whole plant biomass of both grasses was pyrolyzed at three heating rates (10, 30, and 50 °C min−1) in a joined Thermogravimetry–Differential Scanning Calorimetry (TGA–DSC) analyzer under an inert (nitrogen) environment. The pyrolysis of both grasses was shown to occur in a three-stage process, while most of the thermal transformation occurred at the temperature range of 240–400 °C. The pyrolytic behavior was assessed by estimating the kinetic parameters, using the isoconversional models of Kissenger–Akahira–Sunose and Ozawa–Flynn–Wall. The average values of the activation energy of carrot and mott grasses were shown to be 267 kJ mol−1 (R2 ≥ 0.98) and 188 kJ mol−1 (R2 ≥ 0.98), indicating the suitability of both grasses for co-pyrolysis. Whereas, the difference in the values of enthalpy change and the activation energy was shown to be &lt;~5 kJ mol−1 at each fractional point, which indicated that the product formation was being favored. Moreover, the high heating values of carrot grass (18.25 MJ kg−1) and mott grass (18.63 MJ kg−1) have shown a remarkable bioenergy potential and suitability of co-pyrolysis for both grasses. This study will lead to establishing an energy-efficient and cost-effective process for the thermal transformation of biomass to bioenergy.

Investigation on thermally induced crystallization processes in glassy (As2Se3)100−x(SbSI)x system

This paper presents the results of non-isothermal kinetics of crystallization processes in complex amorphous chalcogenide glassy system (As2Se3)100−x(SbSI)x (x = 20, 30, 50, 70 and 80 at.%). The results were obtained using differential scanning calorimetry in non-isothermal regime of work at different heating rates. The crystal growth kinetics was determined by application of several isokinetic and isoconversional theoretical models on experimental data. Kinetic parameters, such as activation energy of crystallization E and the Avrami exponent n have also been determined. It was established that parameter E depends on degree of conversion. The values of Avrami exponent indicated that crystallization mechanism is one-dimensional and nucleation takes place at the surface in the samples with lower SbSI content. For the compositions with higher SbSI amount crystallization process is realized as a volume nucleation. Also, there is an increase in devitrification affinity with the greater presence of structural units of the type Sb2S3 and SbSI, instead of Sb2Se3 and As2Se3. The decrease in thermal stability for the samples with x = 70 and 80 at.% was also noted and confirmed with several parameters using different criteria.

Pyrolysis kinetics and synergistic effect in co-pyrolysis of Samanea saman seeds and polyethylene terephthalate using thermogravimetric analyser

This work deals with co-pyrolysis of polyethylene terephthalate (PET) with Samanea saman seeds (SS) to understand the kinetics and synergistic effects between two different feedstocks. SS and PET were blended in different ratios (1:1, 3:1 and 5:1) and iso-conversional models such as Kissinger-Akahira-Sunose (KAS), Friedman method (FM), Starink (ST), Ozawa-Flynn-Wall method (OFW), and Coats-Redfern method (CR) were used to calculate the kinetic parameters. Results substantiate assumed hypothesis that blending of SS and PET at 3:1 provided higher synergistic effect and RMS value, which in turn indicated maximum formation of hot volatiles during pyrolysis. Kinetic analysis confirmed that individual SS and PET required higher activation energy while blended SS and PET at 3:1 ratio required lower activation energy to start the reaction. The thermodynamic and kinetic analysis confirmed that biomass had complex reaction kinetics which depends on reaction rate as well as its order.

Pyrolysis characteristics and kinetic analysis of rice husk

In this work, the thermo-gravimetric and differential thermo-gravimetric curves of rice husk at different heating rates (20, 40, 60, 80 and 100 °C min−1) were obtained using a thermo-gravimetric analyzer under nitrogen atmosphere. The pyrolysis characteristics of rice husk were analyzed. The fitted Gaussian function peaks showed that the pyrolysis mass loss of rice husk can be characterized by three independent reactions. The devolatilization index D was calculated, and the effect of different experimental statuses on the pyrolysis of rice husk was discussed. The kinetic parameters of rice husk were calculated using iso-conversional models and distributed activation energy models (DAEMs). The kinetic parameters obtained by differential Friedman method and integral Ozawa method were found to be 224.85 kJ mol−1 and 220.06 kJ mol−1, respectively. The apparent activation energies for pyrolysis were not fixed value and continuously fluctuated with the increase in conversion rate. The kinetic parameters, obtained using the Kissinger method, were relatively simple and could not represent the variation trends of variables. Six different probability density functions for DAEMs were used to compute the pyrolysis kinetic parameters. The energy compensation effect existed between the activation energy and the frequency factors. It can be concluded from a comprehensive F test and the amount criterion test (Akaike information criterion test) that the Weibull model is more appropriate to study the pyrolysis of rice husk. Finally, the apparent activation energy, calculated using the Weibull model, was calculated to be 131.97 kJ mol−1, whereas the reaction order was 3.2.

Non-isothermal kinetics of pseudo-components of waste biomass

Non-isothermal kinetics involved during the slow pyrolysis of waste biomass (sawdust) was investigated. The slow pyrolysis profile of sawdust was distinguished into three reactions corresponding to each pseudo component (hemicellulose, cellulose & lignin) through the deconvolution process. Kinetic triplets (activation energy, reaction mechanism & pre-exponential factor) were estimated for each pseudo component. The Straink (SR) and Friedman (FR) iso-conversional kinetic models were used to calculate the activation energy of pseudo-cellulose (SR = 162.90 kJ/mol, FR = 165.67 kJ/mol), pseudo-hemicellulose (SR = 156.25 kJ/mol, FR = 158.47 kJ/mol) and pseudo-lignin (SR = 301.62 kJ/mol, FR = 316.72 kJ/mol). The reaction mechanism involved during the slow pyrolysis of waste sawdust was identified through integral master plot method. The results revealed that the two-dimensional contract area (R2) and second order reaction (F2) reaction mechanism dominates slow pyrolysis of pseudo-cellulose and pseudo-hemicellulose, respectively. However, no exact reaction mechanism was observed for pseudo-lignin. The pre-exponential factor was determined with the help of the activation energy and reaction mechanism. Thermodynamic parameters i.e. change in enthalpy (ΔH), entropy (ΔS) and Gibb’s free energy (ΔG) were also determined for pseudo-cellulose (ΔH=157.54kJ/mol, ΔS=-17.615 J/mol and ΔG=168.64 kJ/mol) and pseudo-hemicellulose (ΔH=151.28kJ/mol, ΔS=6.61 J/mol and ΔG=147.12 kJ/mol).

Combustion behaviors of pileus and stipe parts of Lentinus edodes using thermogravimetric-mass spectrometry and Fourier transform infrared spectroscopy analyses: Thermal conversion, kinetic, thermodynamic, gas emission and optimization analyses

The combustion behaviors of both Lentinula edodes pileus (LEP) and stipe (LES) were characterized in response to four heating rates in the air atmosphere using thermogravimetric (TG)-mass spectrometry and TG-Fourier transform infrared spectroscopy analyses. There were two and three main peaks of the derivative TG curves for LEP and LES, respectively, with their main combustion stage occurring between 130 and 620 °C. Four iso-conversional models were compared to estimate activation energy values of their combustions. The main emission peaks of most gases ranged from 200 to 350 °C and from 500 to 600 °C for LEP and LES. Their comprehensive combustion parameters at 20 K/min (1.53 and 2.40 × 10−6 %2/(min2·K3) for LEP and LES, respectively) as well as joint optimizations confirmed their great potential for bioenergy generation. The waste stream of LEP and LES could be well disposed through their combustions with a low level of air pollution.

Investigation of pyrolysis kinetics and thermal behavior of Invasive Reed Canary (Phalaris arundinacea) for bioenergy potential

The present study investigates the pyrolysis kinetic and thermal behavior of Invasive Reed Canary (Phalaris arundinacea) and evaluate the potential of the biomass as a bioenergy feedstock. The biomass sample was collected from wild areas of Ontario, Canada. Thermal degradation analysis were conducted by exposing the dried and powdered biomass to four heating rates (10, 20, 30 and 40 K min-1) using a Thermogravimetric Analyzer in an inert environment. Thermal data was utilized to explain the reaction chemistry using iso-conversional models of Kissenger-Akahira-Sunose (KSA), Starink and Flynn–Wall–Ozawa (FWO). Evaluation of the kinetic parameters such as the activation energy and the pre-exponential factor illustrates the promising bioenergy potential of the biomass. Fourier-transform infrared spectroscopy and Gas chromatography techniques indicate existence of valuable pyrolysis products such as aliphatic hydrocarbons. Low cost in addition to the abundance of the biomass may facilitates the consumption of the biomass for bioenergy application in cost efficient and environmental friendly manners.