Average Value Of Activation Energy Research Articles

The heating–cooling rate effect on thermal properties of high nickel-rich NiTi shape memory alloy

In this study, the effects of heating and cooling rate on the thermal properties of high nickel-rich Ni55Ti45 shape memory alloy were investigated. Transformation temperatures and enthalpies were determined by differential scanning calorimetry. R-phase was observed with two-stage phase transformation during cooling. Transformation finish temperatures were affected, while the transformation start temperatures were not changed by heating–cooling rate. Kissinger, Takhor, and Ozawa methods were applied to find activation energy that is needed for phase transformation. The average activation energy value of 200.5 kJ mol−1 was calculated for Ni55Ti45 alloy. The calculated activation energy was found lower than the ones reported in the literature.

Slow pyrolysis characteristics of bamboo subfamily evaluated through kinetics and evolved gases analysis

The objective of this study is to investigate the pyrolysis and kinetic characteristics of three varieties of the bamboo subfamily via thermogravimetry/Fourier transform infrared spectrometry (TG-FTIR) coupling technologies. The pyrolysis process can be divided into three stages of dehydration, volatilization, and carbonization. TG-FTIR analysis revealed that evolved gas is constituted by CO2, CO, CH4, H2O, NO, NO2, formic acid, HCN, and CO functional groups as major pyrolysis products. The kinetic parameters of pyrolysis were calculated using model-free methods of distributed activation energy (DAEM). With an increase in conversion, the activation energy of each bamboo subfamily exhibited distinct variations. The average values of activation energy for moso bamboo, bambusa multiplex, and black bamboo determined by DAEM were 201.59, 220.49, and 224.47 kJ/mol, respectively. Results of thermodynamic and kinetic analysis indicate that the bamboo subfamily shows great potential as an alternative fuel by pyrolysis.

Pyrolysis Characteristics and Reaction Mechanisms of Pine Needles.

Pyrolysis has been considered as a promising method to utilize biomass by thermal cracking for energy or feedstock. In order to provide guidance for thermochemical process management of pine needle utilization by pyrolysis, the pyrolysis kinetics and reaction mechanism of one typical pine needle are investigated employing thermogravimetric analysis in nitrogen in the present study. Multi kinetics methods including model-free method and model-fitting method are adopted. Results indicate that one peak and three shoulders occur in the reaction rate curves. The maximum reaction rates decrease with the increasing of heating rates, and the average reaction rate of the whole process is 0.0021K-1. The pyrolysis process of pine needles in nitrogen may be divided into four stages in the conversion rate range of 0~0.1, 0.1~0.5, 0.5~0.75, and 0.75~1, which may be mainly resulted by the reaction of the extractives, hemicellulose, cellulose, and lignin, respectively. The reaction mechanisms of stages I, II, and III may be regarded as random nucleation and nuclei growth, but the reaction mechanism of stage IV may be chemical reaction. The average value of activation energy and logarithm of the pre-exponential factor for the whole pyrolysis process is 215.99kJmol-1 and 38.75min-1, respectively.

Influence of waste products from electricity and cement industries on the thermal behaviour of Estonian clay from Kunda deposit

The influence of two different oil shale ashes formed, respectively, at pulverized firing and at circulated fluidized bed combustion of Estonian oil shale (OS) at electricity production, and clinker dust (CD) formed at cement production on the thermal behaviour of Estonian clay from Kunda deposit, and, for comparison, on the illitic clay from Fuzerradvany (Hungary) was studied. Composition of clay with 40% of previously fired at 1050 °C clay (grog) was used as a basement one. In the blends studied the fired clay was partly or totally replaced with OS ash or CD additives. Experiments were carried out under non-isothermal condition up to 1050 °C using a Setaram Setsys 1750 thermoanalyzer coupled with Pfeiffer Omnistar Spectrometer at the heating rates of 1.25, 2.5, 5 and 10 °C min−1 in an oxidizing atmosphere containing 79% of Ar and 21% of O2. The differential isoconversional method of Friedman was applied to calculate the kinetic parameters. Depending on the origin of the additive the thermal behaviour of blends following the two-step route differentiated remarkably from the same characteristics of clays. The value of activation energy along the reaction progress varied for illitic clay and its blends with OS ash and CD additives more than based on Kunda clay, but, contrary, the average activation energy values for blends based on Kunda clay are, as a rule, bigger than based on illitic clay.

Kinetic Analysis of Digestate Slow Pyrolysis with the Application of the Master-Plots Method and Independent Parallel Reactions Scheme.

The solid fraction obtained by mechanical separation of digestate from anaerobic digestion plants is an attractive feedstock for the pyrolysis process. Especially in the case of digestate obtained from biogas plants fed with energy crops, this can be considered a lignin rich residue. The aim of this study is to investigate the pyrolytic kinetic characteristics of solid digestate. The Starink model-free method has been used for the kinetic analysis of the pyrolysis process. The average Activation Energy value is about 204.1 kJ/mol, with a standard deviation of 25 kJ/mol, which corresponds to the 12% of the average value. The activation energy decreased along with the conversion degree. The variation range of the activation energy is about 99 kJ/mol, this means that the average value cannot be used to statistically represent the whole reaction. The Master-plots method was used for the determination of the kinetic model, obtaining that n-order was the most probable one. On the other hand, the process cannot be modeled with a single-step reaction. For this reason it has been used an independent parallel reactions scheme to model the complete process.

Thermal degradation kinetic, electrical and dielectric behavior of brush copolymer with a polystyrene backbone and polyacrylate-amide side chains/ nanographene-filled composites

A brush copolymer having polystyrene backbone and flexible PA-amide (polyacrylate-amide) brushes that exhibit thermoplastic elastomer property was synthesized, and brush copolymer composites with nanographene in various ratios were prepared. The thermal properties of the macroinitiator, brush copolymer and composites were investigated using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The activation energy (Ea) of thermal decomposition of brush copolymer/6 wt% nanographene was estimated by the Flynn-Wall-Ozawa method, and the average activation energy value for the 0.1–0.7 conversion was estimated as being 141.7 kJ/mol. Electrically conducting nanographene-based brush copolymer composites were produced. DC and AC electrical conductivity and dielectric properties of permittivity of nanographene-based brush copolymer composites were investigated. Further, the activation energy profile of different nanographene/brush copolymer composites were determined by measuring DC conductivity of individual composite materials. A heterojunction diode made from the polymer nanographene composites were magnified on a p-type Si substrate using a hydro/solvo thermal method. The polymer composite/p-Si thin film heterojunction diode properties were studied using current-voltage (I-V) and capacitance-voltage (C-V) analysis.

Comparative pyrolysis characteristics of representative commercial thermosetting plastic waste in inert and oxygenous atmosphere

Combustion (pyrolysis with oxygen) and pyrolysis without oxygen are two potential methods to deal with thermosetting plastic waste. To evaluate which is preponderant to recycle thermosetting plastic waste and provide guidance for optimization of product yield by pyrolysis, the pyrolysis characteristics of one representative commercial thermosetting plastic waste (phenolic glass fibre reinforced plastic, phenolic GFRP) in inert and oxygenous atmosphere are comparatively investigated employing thermogravimetric analysis (TGA), in situ Fourier transform infrared (FTIR) and online TGA-FTIR in the present study. The activation energy at different conversion rate is calculated using Tang, Senum-Yang, advanced Vyazovkin and DAEM method. Results indicate that conversion rate decreases with temperature from approximately 460 K to 550 K in oxygenous atmosphere instead of inert atmosphere. The conversion rate in inert atmosphere is larger than that in oxygenous atmosphere from 0 to 0.25, but is less than that in oxygenous atmosphere from 0.25 to 1. The maximum reaction rate in inert atmosphere varies little with heating rate, but decreases with heating rate in oxygenous atmosphere. The pyrolysis process may be divided into two stages with threshold of approximately 600 K and 550 K in inert and oxygenous atmosphere, respectively. The average value of activation energy is 172.92 kJ/mol and 115.04 kJ/mol in inert and oxygenous atmosphere, respectively. Water vapour, alcohols, aromatic compounds, aliphatic compounds, carbon dioxide, carbon monoxide, carboxylic acids and ammonia occur in the volatile products. Alcohols and aliphatic compounds mainly occur in the first stage, while aromatic compounds, carbon dioxide, carbon monoxide and carboxylic acids mainly occur in the second stage. As to water vapour and ammonia, they mainly occur in the first and second stage in inert and oxygenous atmosphere, respectively. More carbon dioxide, carbon monoxide and ammonia are generated in oxygenous atmosphere than those in inert atmosphere. Besides, more amorphous carbon is generated in inert atmosphere than that in oxygenous atmosphere.

Experiment and expectation: Co-combustion behavior of anthracite and biomass char

The combustion behavior of anthracite, biomass (Ficus virens) char and their blends were investigated by thermogravimetry analysis (TGA). The combustion process mainly focused on the volatile combustion and char combustion. The addition of char reduced the initial temperature and final temperature of fuels. The interactions firstly inhibited and then facilitated. When the blending ratio was 70AN30FV, the antagonism was the minimum, and synergism was the strongest at 830 K for the random ratio. The kinetic models of Coats-Redfern (CR), Doyle equation (Doyle), Friedman (FR), Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) were used to calculate the kinetic parameters. The average values of activation energy for CR and Doyle were close and that of KAS, FWO and DAEM were near. Based on these six models, the corresponding expectation equations of activation energy and pre-exponential factor were proposed and the best predicted results was CR model for 60AN40FV.

Thermal effect and kinetic analysis on co-pyrolysis of furnace slag with cellulose from biomass

Abstract Metallurgical industry accounts for 20.40% of the total energy consumption in the industry of China. Energy saving from furnace slag of the steel industry is essential for the clean and green development of China. Thus, in this paper, the thermal effect and kinetic analysis of the biomass mixed with furnace slag at different mass ratios (10 wt%, 30 wt.% and 50 wt.%) was investigated via TGA under different heating rate from ambient temperature to 900 oC. Cellulose was selected as the primary organic compound in biomass, and iso-conversional method was applied for calculating activation energy. The maximum decomposition rate and temperature of maximum decomposition rate get higher as the heating rate increases. Furnace slag shows positive synergistic effects under 30% mass ratio with 6% higher volatile yield than that from theory calculation. The average activation energy values of CE, Slag-CE-10, Slag-CE-30, Slag-CE-50 were 187.54 kJ·mol-1, 260.81 kJ·mol-1, 132.79 kJ·mol-1 and 159.45 kJ·mol-1.

Thermal degradation kinetics of sugarcane leaves (Saccharum officinarum L) using thermo-gravimetric and differential scanning calorimetric studies

Pyrolysis of sugarcane (Saccharum officinarum L) leaves (SCL) has been investigated using DTA/TGA and DSC techniques. Proximate and ultimate analyses and calorific value measurement have been carried out using standard protocols. The sugar cane leaves contain 44% cellulose, 22% hemicellulose and 17% lignin. The pyrolysis have been carried out at six heating rates varying from 5 to 40 °C/min. Analysis of the pyrolysis results has been carried using iso-conversional model free methods as well as multiple linear regression method. For the fractional conversion range of 0.05–0.95, the average apparent activation energy values evaluated from iso-conversional methods have ranged from 214.9 to 239.6 kJ/mol where as in the case of multiple linear regression analysis it has ranged from 25.06 to 57.23 kJ/mol. The multi-step reaction mechanism has been investigated using the Criado method. The results of this study are useful for the design of large scale biomass thermal conversion process.

Oxidative stability and thermal performance of ester based lube oil with lithium salt additives

In the present study, the performance of bis(trifluoromethylsulfonyl)amine lithium (LiTFSI) and lithium tetrafluoroborate (LiBF4) salts as a novel lubricant additive was assessed. The oxidative stability of ester based lube oil (L2) when mixed with LiTFSI and LiBF4 (1.0 and 5.0 mass%) was estimated by calorimetric techniques combined with the thermokinetic model. A significant improvement in the viscosity index by 8.0% was observed when 5.0 mass% LiTFSI was used. Thermogravimetric analysis revealed two major mass loss steps between 98.0 and 336.0 °C and 292.0 to 454.0 °C at different heating rates. The chemical composition of treated samples revealed the formation of octatriacontyl pentafluoropropionate complex, which could be responsible for the increase in thermal stability of L2. The estimated average value of apparent activation energy (Ea) of L2 was 82.5 kJ·mol−1. The 5.0 mass% LiTFSI sample had the highest oxidative stability, and the kinetic models revealed that the Ea was 121.1 kJ·mol−1. The thermal performance of lubricant oil could be improved by increasing the concentration of Li salt additives up to 5.0 mass%.

Kinetic and Thermodynamic Analysis of Thermal Decomposition of Deodar (Cedrus Deodara) Saw Dust and Rice Husk as Potential Feedstock for Pyrolysis

Abstract A comparative study on thermal analysis of two waste biomass materials of Kashmir namely deodar (Cedrus deodara) saw dust (DSD) and rice husk (RH), was carried out at different heating rates of 10, 25, 50 and 100 °C min−1 in air and nitrogen atmospheres. The onset, peak and burnout temperatures and rates of decomposition of components were determined and compared to understand the combustion and pyrolysis kinetics of selected biomass materials using iso-conversional Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) models. The kinetic parameters calculated were in turn used to calculate the changes in thermodynamic parameters, the enthalpy (ΔH), the Gibbs free energy (ΔG) and the entropy (ΔS). The physicochemical characterisation was carried out by elemental analyser and FTIR spectroscopy. The average activation energy values for RH were found to be 107.6 and 101.2 kJ mol−1 in air atmosphere and 85.5 and 92.1 kJ mol−1 in nitrogen atmosphere based on KAS and OFW models, respectively. The activation energy for DSD on the other hand was found to be 89.9 and 95.3 kJ mol−1 in air, 179.2 and 180.6 kJ mol−1 under nitrogen atmosphere based on KAS and OFW models, respectively. The heating values of the two biomasses (~ 10 to16 MJ kg−1) and Gibbs free energy values (between 165 to 176 kJ mol−1) indicate that the selected biomass can not only prove to be potential feedstock for pyrolysis but also can become a useful source of energy and chemicals.

A comparative study on pyrolysis characteristics of bituminous coal and low-rank coal using thermogravimetric analysis (TGA)

ABSTRACT This study aims to compare the pyrolysis characteristics of low-rank coal and bituminous coal with the elemental composition using thermogravimetric analysis (TGA) at the heating rates of 10, 20, 30, and 40 K/min in the temperature range 30–950°C. Friedman’s method was used to find out the kinetic parameters such as activation energy and pre-exponential factor. The average value of activation energy for bituminous coal was found to be between 46.24 and 420.00 kJ/mol and for low-rank coal it was 42.321 kJ/mol. These experimental results may be useful for the utilization of low-rank coal.

Thermal decomposition kinetics of raw and treated olive waste

The pyrolysis characteristic of raw and ultrasound assisted enzyme hydrolysis treated (UAEH) olive waste was investigated using the thermogravimetric analysis at 5, 10, 15, and 20?C per minute in the nitrogen atmosphere. The thermal decomposition was divided into three stages in the thermograph curve, and the thermogravimetric curve showed the same decomposition trend for two samples. The temperature interval and peak temperature were different for two different samples, and moved to higher temperature with the increase in heating rate. Differential thermogravimetric and differential scanning calorimetry curves depicted that the structure and composition of samples were changed by UAEH. Meanwhile, the kinetic parameters were calculated by the Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Coats-Redfern methods. For untreated and treated olive waste, the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods revealed the similar kinetic characteristics for the conversion degree from 0.1 to 0.9, and the average values of activation energy were 201.42 kJ/mol and 162.97 kJ/mol, respectively. The change in activation energy was clearly dependent on the extent of conversion. The Coats-Redfern method suggested the second-order model (F2, f(?) = (1 ? ?)2) could be used to better describe the thermal decomposition mechanism of untreated and treated olive waste. Besides, thermodynamic characteristics of olive waste treated were consistent with that of the untreated sample.

Thermogravimetric analysis of bamboo-tar under different heating rates based on distributed activation energy model

Carbon fiber is a kind of new polymer material with excellent mechanical properties and being applied widely. The process of carbon fiber prepared by bamboo tar, including extraction, condensation, spinning, oxidation and carbonation, is influenced by the pyrolysis kinetics significantly. In this paper, the thermogravimetric analysis (TGA) of bamboo tar produced in the process of pyrolysis and gasification of the bamboo which is known as Phylostachys sulphurea, was analyzed by the distributed activation energy model (DAEM) to understand the kinetic properties and parameters of bamboo tar. The thermogravimetric analysis of bamboo tar which is used as the raw material of carbon fiber was conducted under 5 different heating rates (i.e. 5, 10, 15, 30 and 50 °C/min, etc.) in nitrogen atmosphere. The results show that the activation energy of bamboo tar and the exponential factor increased significantly with the increase of the heating rate, and the low heating rate is advantageous to the extraction of bamboo tar solvent and the thermal polycondensation, which can provide scientific reference for the optimization of carbon fiber technology. The thermal weight results show that the temperature range of bamboo tar being decomposed rapidly is 213°C-410°C. The ranges of the activation energy were calculated by DAEM, which have small difference in comparisons with five heating rates when the conversion rate is at 0.1-0.6 and the average value of the activation energy is 119 kJ/mol. The stability range of the activation energy is enlarged when the conversion rate is greater than 0.6 and heating rate increases. Keywords: bamboo tar, carbon fiber, thermogravimetric analysis (TGA), distributed activation energy model (DAEM) DOI: 10.25165/j.ijabe.20181106.3839 Citation: Zhang H, Yan B B, Lei T Z, Liu T, Hu J J, Li Y M, et al. Thermogravimetric analysis of bamboo-tar under different heating rates based on distributed activation energy model. Int J Agric & Biol Eng, 2018; 11(6): 180–186.

Comparison of differential and integral methods for coal oxidation kinetic analysis

The influence of two different methods of kinetic analysis on obtained values of kinetic constants of coal oxidation process was studied. The oxidation of T-grade bituminous coal of Kuznetskiy deposit and 2B-grade lignite of Borodinskoe deposit was investigated by means of thermogravimetric analysis. All measurements were carried out with heating rates 2,5, 10, 25 and 40 K/min in temperature range 300-1100 K in air medium. The dependences of activation energy and frequency factor on conversion were obtained using two isoconversional methods: differential method of Freidman and integral method of Kissinger-Akahira-Sunose. The average values of activation energy which were obtained by KAS method were higher by 14.5 % for bituminous coal and 23.3 % for lignite in comparison with values obtained by Freidman method. The same relations were observed for frequency factor values.

Effect of pyrolysis temperature on pine sawdust chars and their gasification reactivity mechanism with CO2

AbstractThe mechanism on CO2 gasification reactivity of pine sawdust chars (PS chars) obtained from the different pyrolysis temperatures (873, 973, and 1073 K) is studied on the basis of nonisothermal thermogravimetric method. The order of gasification reactivity is PS char‐873 > PS char‐973 > PS char‐1073. The effect of pyrolysis temperature is depicted by microstructure characterization, and the gasification reactivity is analyzed with nonisothermal kinetic models. The microstructure characterizations of chars are characterized by scanning electron micrograph, Brunauer–Emmett–Teller, Fourier transform infrared, and X‐ray diffraction. Results show that the microcrystalline structure of biomass char is the dominant factor for the effect of gasification reactivity with the pyrolysis temperature rising. The kinetic models of Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose are applied to describe the kinetics of gasification process. The average values of activation energy are in close agreement with the two methods. Both of the methods prove that F2 mechanism is applicable to the gasification of PS chars at lower pyrolysis temperature and F1 mechanism at higher pyrolysis temperature. Besides, there is a compensation effect between activation energy and preexponential factor in the CO2 gasification process.

Co-hydrothermal carbonization of corn stalk and swine manure: Combustion behavior of hydrochar by thermogravimetric analysis

The combustion behavior of the hydrochar from co-hydrothermal carbonization (HTC) of corn stalk (CS) and swine manure (SM) was thermogravimetrically investigated. Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were used for kinetic analysis, and the thermodynamic parameters were determined. Results showed that HTC decreased the combustion property and stability of SM, while co-HTC with CS significantly improved the combustion performance of the hydrochar including the increased ignition temperature and decreased burnout temperature. HTC of SM decreased the average activation energy (Ea) value from 140.40 and 137.31 KJ/mol to 124.40 and 120.17 KJ/mol by FWO and KAS, respectively, and increasing proportion of CS during co-HTC increased the Ea value of the hydrochar to 141.53–171.23 and 138.35–169.66 KJ/mol, respectively. The thermodynamic parameters confirmed the enhanced combustion reactivity of the hydrochar from co-HTC of CS and SM. These findings demonstrated that co-HTC with CS benefited the hydrochar production from SM with improved combustion performance.

Al2O3/chitosan nanocomposite: Preparation, characterization and kinetic study of its thermal degradation

The 10%Al2O3/Chitosan nanocomposite (10%Al2O3/CS) was prepared and characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer, Emmett and Teller method (BET). These techniques showed the formation of 10%Al2O3/CS by the interaction between functional groups of CS such as NH2, OH and CO and Al2O3. The non-isothermal degradation process of 10%Al2O3/CS under an air atmosphere was investigated by Simultaneous ThermoGravimetric and Differential Thermal Analysis (TGA/DTA) and Differential Scanning Calorimetry (DSC) at different heating rates (β = 5, 10, 15 and 20 K/min). The kinetic parameters of thermal degradation were calculated using Kissinger-Akahira-Sunose (KAS) and Kissinger (KIS) methods, and it was found that the average values of activation energies were Ea = (110 ± 5) kJ/mol from Kissinger method, but the KIS method give three conversion domains in which Ea exhibits practically constant values, namely (0.15 – 0.30), (0.35 – 0.50) and (0.60 – 0.68) with average values of (131 ± 3) kJ/mol, (190 ± 10) kJ/mol and (71 ± 7) kJ/mol, respectively. At last, the value of range (0.15 – 0.30) was used to match the experimental and simulated Y(α) and Z(α) master plots. Indeed, it was found that the modified Sestak-Berggren f(α)=c(1−α)nαm does not correctly describe the kinetics of 10%Al2O3/CS degradation process, even if this model allowed reproducing qualitatively the Y(α) curves, giving the same maximums, αm, for each value of β in rang of α (0.15–0.3), which are consistent with the thermal degradation mechanisms of 10%Al2O3/CS. Finally, the estimated temperature of degradation is 565 K with a rate constant of 0.172 min−1.

Pyrolysis kinetics and mechanism of typical industrial non-tyre rubber wastes by peak-differentiating analysis and multi kinetics methods

Pyrolysis is increasingly employed to dispose rubber wastes by thermal cracking into chemicals. Previous studies focus on pyrolysis recycling of tyre rubber wastes. The pyrolysis of non-tyre rubber wastes, which may be different from that of tyre rubber wastes, receives scarce attention. For the purpose of providing guidance for thermo-chemical process management for the pyrolysis recycling of non-tyre rubber wastes, the pyrolysis kinetics and mechanism of representative industrial non-tyre rubber wastes namely the mixture of waste hoses, floor coverings and sealing strips are investigated using thermogravimetry in nitrogen and peak-differentiating analysis with Guassian function. Multi kinetics methods are adopted. Results indicate that three peaks and three shoulders occur in the reaction rate curves. Guassian function is capable to well separate the pyrolysis of non-tyre rubber wastes mixture into six independent one-step sub reactions. The six sub reactions may be characterized by traditional power law model and nucleation mechanism. However, the pyrolysis of non-tyre rubber wastes mixture may be well characterized employing a modified power law model f(α)=1.89×10-5α-1.19 and nucleation mechanism. The average value of activation energy and pre-exponential factor for the whole pyrolysis process of non-tyre rubber wastes mixture is 97.77 kJ/mol and 1.37 × 1010 min−1, respectively.