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

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1657 ◽  
Author(s):  
Pietro Bartocci ◽  
Roman Tschentscher ◽  
Ruth Elisabeth Stensrød ◽  
Marco Barbanera ◽  
Francesco Fantozzi
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Single Step ◽  
Conversion Degree ◽  
Pyrolysis Process ◽  
Average Value ◽  
Model Free ◽  
Master Plots Method ◽  
Master Plots ◽  
Parallel Reactions

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.

scholarly journals Kinetic modeling study on the combustion treatment of cathode from spent lithium-ion batteries

2019 ◽  
Vol 38 (1) ◽  
pp. 100-106 ◽  
Author(s):  
Zhitong Yao ◽  
Shaoqi Yu ◽  
Weiping Su ◽  
Daidai Wu ◽  
Weihong Wu ◽  
...  
Keyword(s):  
Lithium Ion Batteries ◽  
Lithium Ion ◽  
Aluminum Foil ◽  
Isoconversional Methods ◽  
Average Value ◽  
Model Free ◽  
Master Plots Method ◽  
Master Plots ◽  
Three Stages ◽  
Fwo Method

Thermal treatment offers an alternative method for the separation of aluminum foil and cathode materials during spent lithium-ion batteries recycling. In this work, the combustion kinetic of cathode was studied based on six model-free (isoconversional) methods, namely Flynn–Wall–Ozawa (FWO), Friedman, Kissinger–Akahira–Sunose, Starink, Tang, and Boswell methods. The possible decomposition mechanism was also probed using a master-plots method (Criado method). Thermogravimetric analysis showed that the whole thermal process could be divided into three stages with temperatures of 37–578°C, 578–849°C, and 849–1000°C. The activation energy ( Eα) derived from these model-free methods displayed the same trend, gradually increasing with a conversion range of 0.002–0.013, and significantly elevating beyond this range. The coefficients from the FWO method were larger, and the resulted Eα fell into the range of 10.992–40.298 kJ/mol with an average value of 20.228 kJ/mol. Comparing the theoretical master plots with an experimental curve, the thermal decomposition of cathode could be better described by the geometric contraction models.

scholarly journals Kinetic analysis of CO2 gasification of biochar and anthracite based on integral isoconversional nonlinear method

2020 ◽  
Vol 39 (1) ◽  
pp. 527-538
Author(s):  
Bing Dai ◽  
Jia-Yong Qiu ◽  
Shan Ren ◽  
Bu-Xin Su ◽  
Xiang Ding ◽  
...  
Keyword(s):  
Activation Energy ◽  
Early Stage ◽  
Model Fitting ◽  
Preexponential Factor ◽  
Single Step ◽  
Conversion Degree ◽  
Nonlinear Method ◽  
Gasification Reactivity ◽  
Model Free ◽  
Gasification Process

AbstractThe nonisothermal thermogravimetric analysis was implemented for gasification of sawdust char (SD-char), wheat straw char (WS-char), rice husk char (RH-char), bamboo char (BB-char) and anthracite coal (AC) in the presence of CO2. The dependence of activation energy upon conversion for different biochars and AC was obtained by the integral isoconversional nonlinear (NL-INT) method which is a model-free method. Based on the activation energy values from the NL-INT method, a model-fitting method called random pore model (RPM) was used to estimate the kinetic parameters including the preexponential factor and pore structure parameter from the experimental data. The results are shown that the gasification reactivity of different samples from high to low can be sorted as that of WS-char, SD-char, BB-char, RH-char and AC. In the early stage of gasification, the activation energy values of biochars increase generally with an increase in the conversion degree, whereas the value of AC decreases. Thereafter, the activation energy values remain almost unchanged when the conversion is up to some extent. When the conversion degree varies between about 0.3 and 0.9, these carbon materials can be sorted in the order of average activation energy from low to high as WS-char, SD-char, AC, RH-char and BB-char, respectively, 134.3, 143.8, 168.5, 184.8 and 193.0 kJ/mol. It is shown that a complex multistep mechanism occurs in the initial stage of gasification, while a single-step gasification mechanism exists in the rest of the gasification process. The RPM is suitable for describing the gasification of biomass chars and AC except the initial gasification. Additionally, it is found that the kinetic compensation effect (KCE) still exists in the gasification reactions of biochars and AC. However, the AC deviates markedly from the KCE curve. This may be caused by the similarity of carbonaceous structure of biochars and the difference in reactivity between biochars and AC.

scholarly journals Advanced Isoconversional Kinetic Analysis for the Elucidation of Complex Reaction Mechanisms: A New Method for the Identification of Rate-Limiting Steps

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1683 ◽  
Author(s):  
Nicolas Sbirrazzuoli
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Single Step ◽  
Thermoanalytical Techniques ◽  
Diffusion Controlled ◽  
Physical Transformation ◽  
Exponential Factors ◽  
Isoconversional Kinetic Analysis ◽  
The Individual ◽  
Rate Limiting

Two complex cure mechanisms were simulated. Isoconversional kinetic analysis was applied to the resulting data. The study highlighted correlations between the reaction rate, activation energy dependency, rate constants for the chemically controlled part of the reaction and the diffusion-controlled part, activation energy and pre-exponential factors of the individual steps and change in rate-limiting steps. It was shown how some parameters computed using Friedman’s method can help to identify change in the rate-limiting steps of the overall polymerization mechanism as measured by thermoanalytical techniques. It was concluded that the assumption of the validity of a single-step equation when restricted to a given α value holds for complex reactions. The method is not limited to chemical reactions, but can be applied to any complex chemical or physical transformation.

Evaluation of Kinetic Parameter Calculation Methods for Non-Isothermal Experiments in Case of Varying Activation Energy in Solid-State Transformations / Neizotermisko Eksperimentu Kinētisko Parametru Noteikšanas Metožu Izvērtēšana Mainīgas Aktivācijas Enerģijas Gadījumā Cietfāžu Pārvērtībām

2012 ◽  
Vol 51 (3) ◽  
pp. 209-227 ◽  
Author(s):  
A. Bērziņš ◽  
A. Actiņš
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Kinetic Model ◽  
Kinetic Models ◽  
Frequency Factor ◽  
Conversion Degree ◽  
Model Free ◽  
Determination Methods ◽  
Model Determination ◽  
Energy Determination

Simulations of solid-state transformation kinetics were carried out calculating temperature and conversion degree for non-isothermal experiments with different heating rates. Simulations were divided in two parts: with constant and with variable activation energy. Simulations were analyzed with widely used model-based and model-free activation energy determination methods, frequency factor and kinetic model determination methods. Much of the attention was devoted to the calculation of kinetic models and frequency factors, as a more difficult and less developed step. For simulations where activation energy did not change all activation energy determination methods were found to give correct results. However, much attention should be devoted to frequency factor determination, because incorrect results would lead to problems in determination of kinetic models. For simulations where activation energy changes, correct activation energy can be determined only by differential methods or integral methods using numerical integration over small intervals. Isokinetic relationship coefficients b and c were more accurately determined with the average linear integral method. Correct kinetic model determination was possible only when coefficients b and c were accurate, and only by analyzing results of all available methods.

Kinetic Studies on the Thermal Synthesis of Fluorapatite: Model Free and Model-Fitting Methods

2018 ◽  
Vol 28 ◽  
pp. 75-89
Author(s):  
Hamid Reza Javadinejad ◽  
Sayed Ahmad Hosseini ◽  
Mohsen Saboktakin Rizi ◽  
Eiman Aghababaei ◽  
Hossein Naseri
Keyword(s):  
Activation Energy ◽  
Model Fitting ◽  
Kinetic Studies ◽  
Isoconversional Methods ◽  
Reaction Model ◽  
Heating Rates ◽  
Thermal Synthesis ◽  
Exponential Factor ◽  
Model Free ◽  
Master Plots

The kinetic study for the synthesis of Fluorapatite has been done using the thermogravimetric technique under non-isothermal conditions and at four heating rates of 5, 10, 15 and 20 °C. Both model free and model-fitting methods were used to investigate kinetic parameters. Calcium oxide, phosphorus pentoxide and calcium fluoride were used as the precursor materials. The activation energy values were calculated through model-fitting and isoconversional methods and were used to predict the reaction model and pre-exponential factor. In this case several techniques were considered such as master plots and compensation effects. The results indicated that the reaction mechanism was chemically controlled with second and third order reaction models in the whole range of conversion which the activation energy varied from 25 to 43 kJ/mol.

scholarly journals Determining Preexponential Factor in Model-Free Kinetic Methods: How and Why?

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3077
Author(s):  
Sergey Vyazovkin
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Rate Constant ◽  
Condensed Phase ◽  
Compensation Effect ◽  
Preexponential Factor ◽  
Isoconversional Methods ◽  
Activation Entropy ◽  
Model Free ◽  
Kinetics Of

The kinetics of thermally stimulated processes in the condensed phase is commonly analyzed by model-free techniques such as isoconversional methods. Oftentimes, this type of analysis is unjustifiably limited to probing the activation energy alone, whereas the preexponential factor remains unexplored. This article calls attention to the importance of determining the preexponential factor as an integral part of model-free kinetic analysis. The use of the compensation effect provides an efficient way of evaluating the preexponential factor for both single- and multi-step kinetics. Many effects observed experimentally as the reaction temperature shifts usually involve changes in both activation energy and preexponential factor and, thus, are better understood by combining both parameters into the rate constant. A technique for establishing the temperature dependence of the rate constant by utilizing the isoconversional values of the activation energy and preexponential factor is explained. It is stressed that that the experimental effects that involve changes in the preexponential factor can be traced to the activation entropy changes that may help in obtaining deeper insights into the process kinetics. The arguments are illustrated by experimental examples.

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

Energy ◽  
2021 ◽  
pp. 121194
Author(s):  
Laipeng Luo ◽  
Zhiyi Zhang ◽  
Chong Li ◽  
Nishu ◽  
Fang He ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Lignocellulosic Biomass ◽  
Biomass Pyrolysis ◽  
Master Plots Method ◽  
Master Plots ◽  
Insight Into
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