Simulation Studies on Transformation of Mercury during Combustion Process

2015 ◽  
Vol 1092-1093 ◽  
pp. 912-916
Author(s):  
Jian Yi Lu ◽  
Jie Gao ◽  
Cheng Long Meng
Keyword(s):  
Combustion Process ◽  
Reaction Rate Constant ◽  
Transformation Mechanism ◽  
Exponential Factor ◽  
Homogeneous Oxidation ◽  
Constant Change ◽  
Different Temperatures ◽  
Oxidation Model ◽  
Reaction Activation Energy ◽  
Kinetics Of

Mercury is one of important trace heavy metal elements and about 1/3 of mercury in the air comes from emissions of coal-fired flue gas. In this study, we simulated mercury’s 4 important reactions of the oxidation kinetics mechanism and got every reactions’ rate variations; meanwhile we studied the kinetics of four reactions and got the reacting paths, five pre-exponential factor in different temperatures, reaction activation energy change and reaction rate constant change, a relatively comprehensive homogeneous oxidation model established. Through the above simulation study, the kinetics and thermodynamics parameters of 4 primitive reactions are obtained, having a great benefit for understanding the transformation mechanism of mercury in the process of coal combustion.

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

scholarly journals Reaction Kinetics of Iron Oxides in Ok Tedi Magnetite Skarn Ore

2020 ◽  
pp. 1-13
Author(s):  
Mary Kama ◽  
Kaul Gena ◽  
Tindi Seje Nuru
Keyword(s):  
Reaction Kinetics ◽  
Papua New Guinea ◽  
Iron Reduction ◽  
New Guinea ◽  
Reaction Rate Constant ◽  
Close Monitoring ◽  
Significant Difference ◽  
Different Temperatures ◽  
C 30 ◽  
Kinetics Of

Magnetic skarn ore (MSO) is one of the major copper bearing ore extracted by the Ok Tedi Copper Mine in Papua New Guinea (PNG). Copper minerals are recovered by flotation while the iron not associated with copper are discarded as tailings. The objective of this investigation was to determine the iron ore reduction kinetics for the Ok Tedi MSO and ascertain if it can be processed to produce sponge iron for a mini steel plant in Papua New Guinea. SEM-EDAX analyses of the Ok Tedi MSO indicated 10.1% C, 30% O, 0.6% Mg, 1.1% Si, 21.1% S, 0.8% Ca and 36.2 % Fe. Most of the iron is in sulfide form. Both naturally occurring and roasted sinters of Ok Tedi MSO samples of different particle sizes were reduced by charcoal carbon at three different temperatures and seven different reduction times. Analyses of the reduced products indicated a metallic iron content of more than 65 wt. % on average. Results showed that there was no significant difference in reduction between fluxed and control materials. Only a slight increase in kinetics with reduced particle size, hence the reaction rate constant (K) did not vary much within the temperatures investigated. Reaction kinetics increases with increasing reduction time at 900°C. Therefore, more iron reduction is observed with particles of 106 µm size. In addition, the results also confirmed that the reduction energy used was higher at 800°C and lower at 1000°C. In conclusion, iron reduction can be improved but close monitoring of temperature and reduction times are essential to determine the reaction kinetics of the Ok Tedi MSO.

Kinetics Analysis of Direct Nitridation of Silicon Powders at Atmospheric Pressure

2012 ◽  
Vol 562-564 ◽  
pp. 167-170 ◽  
Author(s):  
Shao Wu Yin ◽  
Li Wang ◽  
Li Ge Tong ◽  
Fu Ming Yang ◽  
Yan Hui Li
Keyword(s):  
Atmospheric Pressure ◽  
Conversion Rate ◽  
Effective Diffusion ◽  
Silicon Powder ◽  
Reaction Rate Constant ◽  
Kinetics Parameters ◽  
Exponential Factor ◽  
Different Temperatures ◽  
Shrinking Core ◽  
Direct Nitridation

Silicon nitride powders were prepared via direct nitridation of silicon powders diluted with -Si3N4at atmospheric pressure. The nitridation temperature and time were ranged from1623K to 1823K and from 0 minute to 20 minutes respectively. Based on the relations between the conversion rate of silicon and the time at different temperatures, and using shrinking core model, a simple model for the reaction between silicon and nitrogen was derived. The model showed that the relations between the conversion rate of silicon and the time displayed asymptotic exponential conversion trend. Using this model, the kinetics parameters of nitridation of silicon powder at atmospheric pressure were calculated, including pre-exponential factor in Arrhenius equation, activation energy, effective diffusion coefficient, and the formula of the reaction rate constant.

scholarly journals Thermodynamics of copper desorption from soils as affected by citrate and succinate

2008 ◽  
Vol 2 (No. 4) ◽  
pp. 135-140 ◽  
Author(s):  
E.A. Elkhatib ◽  
A.M. Mahdy ◽  
N.H. Barakat
Keyword(s):  
Contaminated Soils ◽  
Reaction Rate Constant ◽  
Organic Ligands ◽  
Order Kinetic ◽  
First Order ◽  
Dissolved Organics ◽  
Different Temperatures ◽  
Energy Consuming ◽  
Delta G ◽  
Kinetics Of

Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behaviour be understood. In this paper, the effect of organic ligands citrate and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at three different temperatures. The results showed that the first order equation adequately described the kinetics of Cu desorption from clay and sandy soils under isothermal conditions. The reaction rate constant (k<sub>d</sub>) values of the first order kinetic equation for Cu desorption increased consistently with temperature, indicating faster release of Cu at higher temperatures. The Cu desorption rate from the studied soils at all three temperatures was as follows: citric &gt; succinic. The E<sub>a</sub>values indicates that Cu desorption from the studied soils in the presence of two organic ligands is a diffusion controlled reaction. The negative values of &Delta;H* suggest that the desorption reactions are not energy consuming process. The higher negative values of (&Delta;H*) for Cu desorption from the studied soils in the presence of succinic ligand indicate that the heat energy required to overcome the Cu desorption barrier was greater than that for Cu desorption in the presence of citric ligand. Computation of the free energy of activation (&Delta;G*) yielded values ranging for 87 to 87.9 kJ/mol. The largest value represents &Delta;G* for Cu desorption for clay soil in the presence of succinic acid while the lowest value represents &Delta;G* for Cu desorption for sandy soil in the presence of citric acid. The information in this study is quite necessary to construct full functioning models that will help scientists to better understand mobility and bioavailability of metals in soils.

scholarly journals Kinetics of Thermal Degradation of Recycled Polyvinyl Chloride Resin

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
I. M. Alwaan
Keyword(s):  
Thermal Degradation ◽  
Polyvinyl Chloride ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Zero Order Reaction ◽  
Enthalpy And Entropy ◽  
Kinetics Of ◽  
Entropy Of Reaction

The goal of this study is to find the effect of time and temperature on the thermal degradation of recycled polyvinyl chloride (PVC) resin. The isothermal rate of reaction(r)of recycled PVC resin was investigated at the following temperatures to: 100, 110, 120, 130, and 140°C at period of times ranging from 10 to 50 min. The result shows that the rate of reaction(r)of recycled PVC increases with increasing temperatures. The reaction rate constant(K)for temperatures ranging from 100 to 140°C was doubled from 0.028–0.056 mol·L−1·S−1. The process was found to be zero order reaction at all range of temperatures 100–140°C. The activation energy of the thermal weight loss was calculated at different temperatures(E/R = 2739.5°K). The average enthalpy and entropy of reaction at temperature of 298°K were determined.

scholarly journals Thermolysis and Kinetics of Scrap Tyre and Bagasse for Energy Utilization

2013 ◽  
Vol 34 (2) ◽  
pp. 94-101
Author(s):  
Petro Ndalila ◽  
Cuthbet F. Mhilu ◽  
Geoffrey R. John
Keyword(s):  
Activation Energy ◽  
Energy Demand ◽  
Energy Production ◽  
Energy Content ◽  
Combustion Process ◽  
High Energy ◽  
Energy Utilization ◽  
Exponential Factor ◽  
Gasification Process ◽  
Kinetics Of

The increase of energy demand has brought concern to find alternative fuel that will at least sustain the requirement. Bagasse and scrap tyre are waste generated in our industrial activities, which can be used in energy production to subsidize the demand. This paper, aim to study the decomposition behaviour and kinetics of biomass (bagasse) and scrap tyre as preliminary stage of fuel sample analysis to be considered for energy production in gasification/combustion or pyrolysis facilities. The behaviour demonstrated with thermogravimetric analyzer (TGA), shows that all samples have high volatile amount release, 84.21% for bagasse and 85.08% for scrap tyre, which means all are suitable for pyrolysis. However, scrap tyre is most suitable for gasification or combustion due to its high energy content, high ash content and low moisture than bagasse. The determined kinetic parameter were activation energy (E) and pre-exponential factor (A) for hemicellulose/oil as first release composite and cellulose/elastomer as second composite of the analyzed bagasse/scrap tyre samples. The hemicelluloses of bagasse exhibited highest value of activation energy and pre-exponential factor (E=178.191 kJ/mol, and A=1.74×10 16 ) than oil of scrap tyre (E=41.113 kJ/mol, and A= 495.5), which means bagasse is suitable candidate for gasification process due to high operating temperature. With this respect of the study, all candidates may be suitable for pyrolysis or gasification/combustion process. However, for environmental consideration scrap tyre is not suitable due to high sulphur (S) and nitrogen (N) content resulting to high emission ofSOX and NOX .

Study on the Kinetics of Immersion of Photocatalyst in Bamboo

2012 ◽  
Vol 271-272 ◽  
pp. 218-221
Author(s):  
Xu Zhang ◽  
Zhong Feng Zhang ◽  
Kai Huang
Keyword(s):  
Reaction Rate ◽  
Reaction Order ◽  
Reaction Rate Constant ◽  
Exponential Factor ◽  
First Order ◽  
Higher Temperature ◽  
Three Stages ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Stable Stage

In order to improve the anti-mildew property of modified bamboo with photocatalyst, it used TiO2 which is one of the typical photocatalyst as the main study object to discussed the kinetics of immersion of photocatalyst in bamboo. The results show that immersion of TiO2 in bamboo can be divided into three stages, starting with the rapid immersion, the slow immersion in the middle stage, and the stable immersion in the later stage. In the stable stage, only little TiO2 immerse bamboo. The immersion rate is faster at higher temperature to take less time to reach equilibrium. By establishing the kinetic models, the reaction of immersion of photocatalyst can be regarded as the first order reaction with reaction order of 0.97, the reaction rate constant increases with increasing temperature, the activation energy is 5663.133J/mol, and the pre-exponential factor is 20.47h-1.

scholarly journals Methodology for calculating the pre-exponential factor using the isoconversional principle for the numerical simulation of the air injection process

2019 ◽  
Vol 9 (1) ◽  
pp. 37-46
Author(s):  
Jorge Mario Padilla- Reyes ◽  
Marta Liliana Trujillo -Portillo ◽  
Eider Niz- Vel´asquez
Keyword(s):  
Kinetic Model ◽  
Oxidation Process ◽  
Combustion Process ◽  
Operating Conditions ◽  
Air Injection ◽  
Oil Oxidation ◽  
Temperature Oxidation ◽  
Exponential Factor ◽  
Injection Process ◽  
Kinetics Of

The main challenge to predict at Field scale the performance of an air injection process is to understand the oil oxidation process and to have a kinetic model of reactions enabling the prediction of process behavior in a reservoir numerical simulator, under different operating conditions.   Recently, the Isoconversional Principle has been implemented for studying the kinetics of reactions associated with oil oxidation during air injection, based on Ramped Temperature Oxidation tests (RTO). In different published papers, the isoconversional analysis has been used to study the oxidation characteristics of different rock-fluid systems, identify groups of dominant reactions during the crude oil oxidation process, and estimate the effective activation energy for each of the identified reactions.   However, in none of them has a procedure been established for estimating the pre-exponential factor, as this is not a direct measure of isoconversional methods. In this article, a mathematical procedure is proposed for estimating the pre-exponential factor based on the application of Friedman's isoconversional method, inteded for characterizing the kinetics of the reactions associated with the In Situ Combustion process.  This procedure was validated with experimental information and a kinetic model proposed in the literature to model the oxidation behavior of heavy crude.

scholarly journals Kinetics of Starch Degradation during Extrusion Cooking of Steady State Flow Konjac (Amorphophallus oncophyllus) Tuber Flour in a Single Screw Extruder

2020 ◽  
Vol 15 (2) ◽  
pp. 591-602
Author(s):  
Andri Cahyo Kumoro ◽  
Diah Susetyo Retnowati ◽  
Ratnawati Ratnawati
Keyword(s):  
Reaction Rate Constant ◽  
Starch Degradation ◽  
Extrusion Cooking ◽  
Screw Extruder ◽  
High Quality ◽  
Exponential Factor ◽  
Single Screw ◽  
Single Screw Extruder ◽  
Refining Method ◽  
Kinetics Of

The presence of glucomannan in Konjac (Amorphophallus oncophyllus) tuber flour has promoted its various applications, especially in the food, drink, drug delivery and cosmetics. Starch is the main impurity of Konjac tuber flour. Although the common wet refining method may result in a high purity Konjac tuber flour, it is very tedious, time consuming and costly. This research aimed to study the kinetics of starch degradation in the extrusion cooking process of dry refining method to produce high quality Konjac tuber flour. In this research, Konjac tuber flour with 20% (w/w) moisture was extruded in a single screw extruder by varying screw speeds (50, 75, 100, 125, 150 and 175 rpm) and barrel temperatures (353, 373, 393, 413 and 433 K). The results showed that the starch extrusion cooking obeys the first reaction order. The reaction rate constant could be satisfactorily fitted by Arrhenius correlation with total activation energy of 6191 J.mol−1 and pre-exponential factor of 2.8728×10−1 s−1. Accordingly, thermal degradation was found to be the primary cause of starch degradation, which shared more than 99% of the energy used for starch degradation. Based on mass Biot number and Thiele modulus evaluations, chemical reaction was the controlling mechanism of the process. The results of this research offer potential application in Konjac tuber flour refining process to obtain high quality flour product. Copyright © 2020 BCREC Group. All rights reserved 

scholarly journals Study on Kinetics of Transesterification of Biodiesel in Zanthoxylum bungeanum seed Oil Ethyl Ester

2020 ◽  
Vol 194 ◽  
pp. 01004
Author(s):  
Jian Zhang ◽  
Bo Zhang ◽  
Lu Han ◽  
Tao Fan ◽  
Xuanjun Wang
Keyword(s):  
Ethyl Ester ◽  
Seed Oil ◽  
Sodium Ethoxide ◽  
Biodiesel Production ◽  
Dynamics Model ◽  
Alkaline Catalyst ◽  
Exponential Factor ◽  
Zanthoxylum Bungeanum ◽  
Reaction Activation Energy ◽  
Kinetics Of

Zanthoxylum bungeanum seed oil (ZSO) was the by-product of the zanthoxylum industry, and was a kind of cheap and abundant source in china, which can be great potential of use as a feedstock for biodiesel production in terms of reducing the producing cost. Kinetics of Transesterification of Biodiesel from Zanthoxylum bungeanum seed Oil Ethyl Ester using Sodium ethoxide as an alkaline catalyst was studied in this paper. The results showed that the progression of transesterification was grade 1.5, the reaction activation energy was 17.876kJ•mol-1 and the pre-exponential factor was 0.8521L/(mol•min). The contrast between experimental value and predicted value displayed the dynamics model had a good veracity, and can be applied for predicting reaction rate of progress.

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