scholarly journals Kinetic Study and Thermal Decomposition Behavior of Lignite Coal

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Mehran Heydari ◽  
Moshfiqur Rahman ◽  
Rajender Gupta
Keyword(s):  
Solid State ◽  
Thermal Behavior ◽  
Kinetic Parameters ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Solid State Reactions ◽  
Process Conditions ◽  
Coal Pyrolysis ◽  
Model Free ◽  
Lignite Coal

A thermogravimetric analyzer was employed to investigate the thermal behavior and extract the kinetic parameters of Canadian lignite coal. The pyrolysis experiments were conducted in temperatures ranging from 298 K to 1173 K under inert atmosphere utilizing six different heating rates of 1, 6, 9, 12, 15, and 18 K min−1, respectively. There are different techniques for analyzing the kinetics of solid-state reactions that can generally be classified into two categories: model-fitting and model-free methods. Historically, model-fitting methods are broadly used in solid-state kinetics and show an excellent fit to the experimental data but produce uncertain kinetic parameters especially for nonisothermal conditions. In this work, different model-free techniques such as the Kissinger method and the isoconversional methods of Ozawa, Kissinger-Akahira-Sunose, and Friedman are employed and compared in order to analyze nonisothermal kinetic data and investigate thermal behavior of a lignite coal. Experimental results showed that the activation energy values obtained by the isoconversional methods were in good agreement, but Friedman method was considered to be the best among the model-free methods to evaluate kinetic parameters for solid-state reactions. These results can provide useful information to predict kinetic model of coal pyrolysis and optimization of the process conditions.

scholarly journals Kinetic Analysis of the Thermal Decomposition of Polymer-Bonded Explosive Based on PETN: Model-Fitting Method and Isoconversional Method

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Trung Toan Nguyen ◽  
Duc Nhan Phan ◽  
Van Thom Do ◽  
Hoang Nam Nguyen
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Parameters ◽  
Model Fitting ◽  
Isoconversional Method ◽  
Isothermal Tg ◽  
Decomposition Reactions ◽  
Model Free ◽  
Negative Effect ◽  
Adverse Influence ◽  
Vacuum Stability Test

This work investigates kinetics and thermal decomposition behaviors of pentaerythritol tetranitrate (PETN) and two polymer-bonded explosive (PBX) samples created from PETN (named as PBX-PN-85 and PBX-PP-85) using the vacuum stability test (VST) and thermogravimetry (TG/DTG) techniques. Both model-free (isoconversional) and model-fitting methods were applied to determine the kinetic parameters of the thermal decomposition. It was found that kinetic parameters obtained by the modified Kissinger–Akahira–Sunose method (using non-isothermal TG/DTG data) were close to those obtained by the isoconversional and model-fitting methods that use isothermal VST data. The activation energy values of thermal decomposition reactions were 125.6–137.1, 137.3–144.9, and 143.9–152.4 kJ·mol−1 for PBX-PN-85, PETN, and PBX-PP-85, respectively. The results demonstrate the negative effect of the nitrocellulose-based binder in reducing the thermal stability of single PETN, while the polystyrene-based binder seemingly shows no adverse influence on the thermal decomposition of PETN in our presented PBX compositions.

scholarly journals Extraction and Physicochemical Characterization of Chitin Derived from the Asian Hornet, Vespa velutina Lepeletier 1836 (Hym.: Vespidae)

2019 ◽  
Author(s):  
Xesús Feás ◽  
M. Pilar Vázquez-Tato ◽  
Julio A. Seijas Vázquez ◽  
Francisco Fraga-López
Keyword(s):  
Solid State ◽  
Model Fitting ◽  
Physicochemical Characterization ◽  
Frequency Factor ◽  
Alternative Source ◽  
Promising Alternative ◽  
Vespa Velutina ◽  
Model Free ◽  
Isolation And Characterization

The isolation and characterization of chitin (CHI) obtained from Vespa velutina (CHIVV) is described. Moreover, a trapping procedure is presented to selectively catch the invasive species. The chitin contents of dry Vespa velutina was observed to be 11.7 %. The physicochemical properties of CHIVV was characterized by Fourier transform infrared spectroscopy (FTIR), solid-state NMR (ssNMR), elemental analysis (EA), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). Obtained CHIVV is close to pure (43, 47% C, 6.94% H, and 6.85% N) and full acetylated with a value of 95.44%. Also, lifetime and kinetic parameters such as activation E and the frequency factor A using model-free and model-fitting methods, were determined. For CHIVV the solid state mechanism that follows the thermodegradation is of type F2 (Random nucleation around two nuclei). Vespa velutina chitin should not be used at temperatures above 60ºC, since its half-life would be only one year, and from an industrial point of view it would not be profitable. Based on certain factors such as the current and probable continued abundance of Vespa velutina and the quality of the product obtained, the invasive Asian hornet is a promising alternative source of chitin.

scholarly journals COMF: Comprehensive Model-Fitting Method for Simulating Isothermal and Single-Step Solid-State Reactions

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 139
Author(s):  
Yannis Vasilopoulos ◽  
Eliška Skořepová ◽  
Miroslav Šoóš
Keyword(s):  
Solid State ◽  
Model Fitting ◽  
Single Step ◽  
Solid State Reactions ◽  
Comprehensive Model ◽  
Ranking Criterion ◽  
Fitting Method ◽  
Reaction Speed ◽  
Selection Of

It is well known that the implementation of the conventional model-fitting (CMF) method leads to several indistinguishable ‘best’ candidate models (BCMs) for a single-step isothermal solid-state reaction (ISSR), meaning that subjective selection becomes unavoidable. Here, we developed a more robust comprehensive model-fitting method (COMF) which, while maintaining the mathematical simplicity of CMF, utilizes a ranking criterion that enables automatic and unambiguous determination of the BCM. For each model evaluated, COMF, like CMF, fits the integral reaction rate, but, unlike CMF, it also fits the experimental conversion fraction and reaction speed. From this, three different determination coefficients are calculated and combined to rank the considered models. To validate COMF, we used two sets of experimental kinetic data from the literature regarding the isothermal desolvation of pharmaceutical solvates: (i) tetrahydrofuran solvates of sulfameter, and (ii) methanol solvates of ciclesonide. Our results suggest that from an algorithmic perspective, COMF could become the model-fitting method of choice for ISSRs making the selection of BCM easier and more reliable.

Kinetic analysis of cellulose pyrolysis: a short review

2014 ◽  
Vol 68 (7) ◽  
Author(s):  
Cristina Şerbănescu
Keyword(s):  
Major Part ◽  
Reaction Rate ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Short Review ◽  
Physicochemical Process ◽  
Cellulose Pyrolysis ◽  
Model Free ◽  
Proper Design ◽  
The Subject

AbstractSince the 1950s, cellulose pyrolysis has been the subject of intense study, with kinetic analyses forming a major part of these studies. They represent useful tools for a better understanding of the physicochemical process and for the proper design of industrial pyrolysis units. Until recently, the methods most frequently used in these analyses were based on model-fitting, i.e. the fitting of the experimental data to a number of mathematical models. Nowadays, other methods, so-called “model-free” methods, are considered to be more suited. These are based on the principle that, at constant conversion, the reaction rate depends only on temperature. In its first part, this short review presents the particularities and drawbacks of the traditional model-fitting models. Subsequently, several main contributions in this field are listed and discussed. Finally, the more suited “model-free” (isoconversional) methods are explained and several main studies presented, as well as a comparison of this method with the model-fitting ones.

Application of non-linear heating regime for the determination of activation energy and kinetic parameters of solid-state reactions

1998 ◽  
Vol 323 (1-2) ◽  
pp. 101-107 ◽  
Author(s):  
K.V Tomashevitch ◽  
S.V Kalinin ◽  
A.A Vertegel ◽  
N.N Oleinikov ◽  
V.A Ketsko ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Kinetic Parameters ◽  
Solid State Reactions ◽  
Heating Regime ◽  
Linear Heating ◽  
Non Linear
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