Reactant Consumption and Thermal Decomposition Analysis in a Two-Step Combustible Slab

2019 ◽  
Vol 393 ◽  
pp. 59-72 ◽  
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Radley Kebarapetse Mahlobo ◽  
Samuel Olumide Adesanya
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Combustion Process ◽  
Decomposition Analysis ◽  
O2 Consumption ◽  
O2 Concentration ◽  
Rate Of Reaction ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab ◽  
The One

The significance of this paper is to analyse thermal decomposition and reactant consumption in a stockpile of reactive materials, such as that of coal, hay or wood, for example. The study is modelled in a rectangular slab and a two-step combustion process like the one taking place in fuel combustion of an automobile is assumed. The coupling of Runge-Kutta-Fehlberg (RKF) method and Shooting technique is applied to solve the differential equations governing the problem. The combustion process that is so complicated is investigated by consideration of effects of some embedded kinetic parameters, such as the activation energy, on the temperature and the reactant (O2) consumption. It was discovered that parameters such as the activation energy, tend to lower the temperature of the system and correspondingly reduce the O2 consumption rate, whereas parameters like the rate of reaction, increase the temperature during the combustion process, to reduce the O2 concentration of the system. The results also indicate that parameters like the rate of reaction, which increase the temperature profiles, fast-track the exothermic chemical reaction to deplete the reactant faster. However, those that reduce the temperature of the system preserve the reactant concentration.

scholarly journals Heat loss analysis in a radiating slab of variable thermal conductivity

2018 ◽  
Vol 7 (2.23) ◽  
pp. 228 ◽  
Author(s):  
Ramoshweu S. Lebelo ◽  
Kholeka C. Moloi
Keyword(s):  
Differential Equation ◽  
Thermal Conductivity ◽  
Chemical Reaction ◽  
Combustion Process ◽  
Variable Thermal Conductivity ◽  
Temperature Profiles ◽  
Reactive Material ◽  
Loss Analysis ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab

This article investigates the transfer of heat in a stockpile of reactive materials, that is assumed to lose heat to the environment by radiation. The study is modeled in a rectangular slab whose materials are of variable thermal conductivity. The stockpile’s reactive material in this context is one that readily reacts with the oxygen trapped within the stockpile due to exothermic chemical reaction. The study of the combustion process in this case is conducted theoretically by using the Mathematical approach. The differential equation governing the problem is tackled numerically by applying the Runge-Kutta Fehlberg (RKF45) method coupled with the Shooting technique. To investigate the heat transfer phenomena, some kinetic parameters embedded in the governing differential equation, are varied to observe the behavior of the temperature profiles during the combustion process. The results obtained from the temperature profiles, are depicted graphically and discussed accordingly. It was discovered that kinetic phenomena such as the reaction rate parameter, accelerates the exothermic chemical reaction. However, the radiation parameter decelerates the exothermic chemical reaction by lowering the temperature profiles.  

scholarly journals Analysis of Thermal Decomposition of Solid Rocket Propellants

2019 ◽  
Vol 10 (2) ◽  
pp. 43-54 ◽  
Author(s):  
Marcin CEGŁA ◽  
Janusz ZMYWACZYK ◽  
Piotr KONIORCZYK
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Energetic Materials ◽  
Decomposition Analysis ◽  
Simultaneous Thermal Analysis ◽  
Analytical Techniques ◽  
Heating Rates ◽  
Rocket Propellants ◽  
Solid Rocket ◽  
Solid Rocket Propellants

The paper presents results of thermal decomposition analysis of selected solid rocket propellants. Homogeneous propellant PAC and heterogeneous propellant H2 were subjected to simultaneous thermal analysis with the use of NETZSCH STA 2500 Regulus device with five heating rates of 2.5, 5, 7.5, 10 and 15 K/min. The method combines TG, DTG and DTA analytical techniques in a single measurement. The aim of the conducted experiments was to study thermal decomposition of these energetic materials as well as to determine activation energy of the decomposition process and the preconditioning factor from the TG curves. The tested materials properties and chemical composition along with a brief description of the experimental procedure are described. The inverse procedure of calculating the activation energy, based on the Ozawa-Flynn-Wall model is described. Finally, the results of thermal decomposition of two tested solid rocket propellants are presented along with maximum decomposition rates and percentage of mass loss.

scholarly journals Thermal decomposition analysis in a sphere of combustible materials

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401769251 ◽  
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Oluwole Daniel Makinde ◽  
T Chinyoka
Keyword(s):  
Thermal Decomposition ◽  
Chemical Reaction ◽  
Spontaneous Combustion ◽  
Decomposition Analysis ◽  
Combustible Material ◽  
Balance Equations ◽  
One Dimensional ◽  
Spherical Domain ◽  
Exothermic Chemical Reaction ◽  
Implicit Finite Difference

In this article, we look at spontaneous combustion due to exothermic chemical reaction taking place within a stockpile of combustible material. The model includes mass and energy balance equations in a spherical domain. The complicated chemical reaction is simplified by considering a one-dimensional process. The differential equations governing the problem are solved using semi-implicit finite difference method. The effects of kinetic parameters embedded within the system are analyzed and the results are expressed graphically and discussed accordingly.

scholarly journals Kinetic Study of Thermal De-Chlorination of PVC-Containing Waste

2012 ◽  
Vol 730-732 ◽  
pp. 611-616 ◽  
Author(s):  
Alexandra Castro ◽  
Cândida Vilarinho ◽  
Delfim Soares ◽  
Fernando Castro
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Thermal Treatment ◽  
Kinetic Model ◽  
Energy Recovery ◽  
Order Reaction ◽  
Pyrolysis Process ◽  
First Order ◽  
Different Temperatures ◽  
The One

The presence of organic compounds on wastes, especially plastics, is considered an important source of energy. However, most of these plastics contain polyvinyl chloride (PVC), causing recycling problems when it is considered a thermal valorization process for its treatment [1], preventing the use of those residues on these processes, which main goal is the energy recovery [2,3]. A possible solution is to remove the chlorine from PVC containing waste through a pyrolysis process before being subjected to a thermal treatment, for energetic valorization. In this work, it was developed a kinetic model for the thermal decomposition of PVC, in view of its de-chlorination. DTA/TGA testing were performed at different temperatures (between the range of decomposition temperatures of the PVC molecule) indicated a first order reaction and an activation energy of 133800 J/mol, value very close to the one obtained in others works reported [4]. A factorial plan was carried out with different temperatures, performed in lab scale, in which best results were obtained at the temperature of 340 °C, proving the kinetic model obtained.

Study on Thermal Decomposition Kinetics of Nano-Cr(OH)3 Powder

2014 ◽  
Vol 692 ◽  
pp. 377-380 ◽  
Author(s):  
Feng Pan ◽  
Zai Yuan Li ◽  
Chun Ji Li
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Shape Factor ◽  
Decomposition Analysis ◽  
Decomposition Kinetics ◽  
Peak Shape ◽  
Exponential Factor ◽  
Mechanism Function ◽  
Kinetics Of ◽  
Tga Analysis

Abstract. This paper studies on the thermal decomposition analysis kinetics of nanometer powders. The DTA-TG-DTG curves obtain by SDT 2960 Simultaneous DSC-TGA analysis apparatus. Under the condition of N2atmosphere operation and rise temperature velocity was 10°C·min-1. The mechanism function dα/dt=κ(1-α)nis used to calculate the kinetics factors. Reaction progressionnwas obtained by calculation of the kissinger peak shape factor method. The results showed that the apparent activation energy of nano-Ni(OH)2was 254.027 KJ·mol-1, the pre-exponential factor was 3.062×1036, the reaction progression was obtained as 1.560, the kinetic equation is dα/dt=3.062×1036exp(-30554.166/T)(1-α)1.560

Radiation and Thermal Decomposition Analysis in a Reactive Slab of Variable Thermal Conductivity.

2018 ◽  
Vol 7 (3.19) ◽  
pp. 27
Author(s):  
RS Lebelo ◽  
KS Moloi ◽  
CC Chitumwa ◽  
SO Adesanya
Keyword(s):  
Thermal Conductivity ◽  
Heat Loss ◽  
Chemical Reaction ◽  
Co2 Emission ◽  
Combustion Process ◽  
Decomposition Analysis ◽  
Variable Thermal Conductivity ◽  
Radiative Heat Loss ◽  
Exothermic Chemical Reaction ◽  
The Impact

In this article, the impact of radiative heat loss in a stockpile of combustible material is investigated. The heat loss is attributed to the exothermic chemical reaction when the carbon containing material of the stockpile reacts automatically with the oxygen trapped within the stockpile. The study is modelled in a rectangular slab of thermal conductivity that varies with the temperature and loses heat to the surrounding environment by radiation. The differential equations governing the problem are solved numerically using the Runge-Kutta-Fehlberg (RKF) method coupled with the Shooting technique. The effect of each embedded kinetic parameter on the temperature, oxygen (O2) depletion and carbon dioxide (CO2) emission, is analyzed and the results are graphically expressed and discussed accordingly. The results show that the kinetic parameters which enhance the exothermic chemical reaction correspondingly increase the temperature and the CO2 emission during the combustion process, and in turn, these parameters also increase the depletion of O2.  

scholarly journals Thermogravimetric Analysis of Coal Semi-Char Co-Firing with Straw in O2/CO2 Mixtures

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1421
Author(s):  
Debo Li ◽  
Ning Zhao ◽  
Yongxin Feng ◽  
Zhiwen Xie
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Ignition Temperature ◽  
Combustion Process ◽  
Stage I ◽  
Stage Iii ◽  
Combustion Behavior ◽  
O2 Concentration ◽  
Three Stages ◽  
The Individual

For coal semi-char as a by-produced of low-temperature pyrolysis, combustion for power generation is one of the effective utilization methods to realize its clean and efficient utilization. However, the coal semi-char combustion process has a difficult ignition, unstable combustion and low burnout rate. The co-firing of the semi-char with biomass under oxy-fuel conditions can improve the combustion behavior and reduce fossil CO2 emissions. In this paper, the combustion behavior of Shenhua coal semi-char (SHC) co-firing with straw (ST) in O2/CO2 mixture is investigated using thermogravimetric analysis. The results show that each curve lays between those of the individual fuels and presents three peaks (i.e., three stages). The thermogravimetric curves of SHC co-firing with ST can be divided into three stages: the volatile combustion of ST, the co-combustion of SHC and ST fixed-carbons and the SHC fixed-carbon combustion and the decomposition of the difficult pyrolytic material of ST. Blending ST into the SHC can significantly decrease the ignition temperature and improve the comprehensive combustion behavior of blended samples. In increasing the proportion of ST from 25 to 100%, the change of the blended ignition temperature is slight, but the burnout temperature decreases greatly. Kinetic parameters of combustion are calculated by using the Coats–Redfern integral method. Compared to that of stage I and stage III, the activation energy of stage II is significantly lower. As increasing blending ratio from 25% to 100%, the activation energy increases at stage I and decreases at stage III. Furthermore, the O2 concentration obviously affects stage III of 50% SHC + 50% ST, and the thermogravimetric curves at this stage are obviously shifted to the lower temperature zone as the O2 concentration increases. The activation energy of 50% SHC + 50% ST increases as the oxygen concentration increases. Besides, the activation energy shows that the combustion characteristics cannot be determined only by the activation energy obtained by the Coats–Redfern method. These findings can provide useful information for semi-char co-firing with biomass.

On Thermal Stability Analysis of a Convective and Radiative Slab of Variable Thermal Conductivity with Reactant Consumption

2018 ◽  
Vol 389 ◽  
pp. 195-204
Author(s):  
Ramoshweu Solomon Lebelo ◽  
K.C. Moloi ◽  
C.C. Chitumwa ◽  
M.W.R. Sadiki ◽  
P. Baloyi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Kinetic Parameters ◽  
Nonlinear Differential Equations ◽  
Combustion Process ◽  
Variable Thermal Conductivity ◽  
Nonlinear Interactions ◽  
O2 Consumption ◽  
Shooting Technique ◽  
Surrounding Environment ◽  
Rectangular Slab

Thermal stability in a stockpile of reactive materials that are assumed to lose heat to the surrounding environment by convection and radiation is studied in this article. The reactant (O2) consumption is also considered and the investigation is modeled in a rectangular slab. The complicated combustion process results with nonlinear interactions and therefore, the nonlinear differential equations governing the problem are solved numerically with the Runge-Kutta Fehlberg Method (RKF45) that is coupled with the Shooting Technique. The behaviors of the temperature and the reactant, due to effects of some embedded kinetic parameters, are depicted graphically and discussed accordingly. The results show that kinetic parameters that increase the temperature of the system, correspondingly increase the reactant consumption.

scholarly journals Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alberto Palma ◽  
Javier Mauricio Loaiza ◽  
Manuel J. Díaz ◽  
Juan Carlos García ◽  
Inmaculada Giráldez ◽  
...  
Keyword(s):  
Activation Energy ◽  
Acid Hydrolysis ◽  
Energy Production ◽  
Combustion Process ◽  
Operating Conditions ◽  
Raw Material ◽  
Energy Of Combustion ◽  
Increasing Temperature ◽  
Hydrolysis Of ◽  
Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

scholarly journals Co-Combustion Studies of Low-Rank Coal and Refuse-Derived Fuel: Performance and Reaction Kinetics

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3796
Author(s):  
Mudassar Azam ◽  
Asma Ashraf ◽  
Saman Setoodeh Setoodeh Jahromy ◽  
Sajjad Miran ◽  
Nadeem Raza ◽  
...  
Keyword(s):  
Activation Energy ◽  
Waste Management ◽  
Energy Demand ◽  
Power Plants ◽  
Combustion Process ◽  
Isoconversional Methods ◽  
Low Rank ◽  
Heating Rates ◽  
Average Activation Energy ◽  
Refuse Derived Fuel

In connection to present energy demand and waste management crisis in Pakistan, refuse-derived fuel (RDF) is gaining importance as a potential co-fuel for existing coal fired power plants. This research focuses on the co-combustion of low-quality local coal with RDF as a mean to reduce environmental issues in terms of waste management strategy. The combustion characteristics and kinetics of coal, RDF, and their blends were experimentally investigated in a micro-thermal gravimetric analyzer at four heating rates of 10, 20, 30, and 40 °C/min to ramp the temperature from 25 to 1000 °C. The mass percentages of RDF in the coal blends were 10%, 20%, 30%, and 40%, respectively. The results show that as the RDF in blends increases, the reactivity of the blends increases, resulting in lower ignition temperatures and a shift in peak and burnout temperatures to a lower temperature zone. This indicates that there was certain interaction during the combustion process of coal and RDF. The activation energies of the samples were calculated using kinetic analysis based on Kissinger–Akahira–Sunnose (KAS) and Flynn–Wall–Ozawa (FWO), isoconversional methods. Both of the methods have produced closer results with average activation energy between 95–121 kJ/mol. With a 30% refuse-derived fuel proportion, the average activation energy of blends hit a minimum value of 95 kJ/mol by KAS method and 103 kJ/mol by FWO method.

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