scholarly journals Study on the Microscopic Mechanism of Spontaneous Combustion and Oxidation Kinetics of Water-Leached Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Naifu Cao ◽  
Gang Wang ◽  
Yuntao Liang
Keyword(s):  
Kinetic Model ◽  
Moisture Content ◽  
Spontaneous Combustion ◽  
Water Immersion ◽  
Combustion Process ◽  
Oxidation Kinetic ◽  
Oxidation Mechanism ◽  
Temperature Oxidation ◽  
Before And After ◽  
Spontaneous Combustion Of Coal

In this article, a series of experiments have been carried out to study the spontaneous combustion and oxidation mechanism of coal after water immersion and investigate its tendency to spontaneous combustion, analyze the difficulty of spontaneous combustion of coal samples under different water immersion conditions, and establish a kinetic model of water immersion coal oxidation (taking the Bulianta 12# coal as a case study). They rely on physical oxidation adsorption, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry, and oil bath heating. SEM has been used to analyze the characteristics of coal pore structure under different water immersion conditions (water-saturated coal samples under different water loss conditions until the coal samples are completely dried); FTIR served to investigate the characteristics of the molecular chemical structure of the coal surface before and after the coal is immersed in water. Through programmed temperature oxidation experiments combined with FTIR analyses and gas chromatographic (GC) analysis of gaseous products, it has been possible to study the changes of molecular structure and gas products on the surface of coal samples at different temperatures and water immersion conditions. The oxidation reaction rate of the 12# coal samples of Shendong Mine’s Bulianta Mine under different water content conditions during the spontaneous combustion process has been quantitatively studied. The difficulty of spontaneous combustion of coal samples has been correspondingly addressed. A kinetic model from the perspective of oxygen consumption has been proposed. Thermogravimetry-differential scanning calorimetry (TG-DSC) has been used to analyze and study the exothermal oxidation process before and after coal immersion. From the perspective of the exothermic intensity of the coal-oxygen reaction, an oxidation kinetic model for immersed coal samples has been developed to qualitatively determine its spontaneous combustion tendency. Results have shown that the increase in the specific surface area increases the risk of spontaneous combustion, and coal samples after soaking and drying have a stronger tendency to spontaneous combustion than raw coal. The moisture content of the coal sample leading to the easiest ignition conditions is 16.05%. Regardless of the moisture content, the critical temperature is maintained at 65–75°C, and the temperature of the left coal in the goaf should be prevented from exceeding this critical value.

scholarly journals Effects of organic sulfur on oxidation spontaneous combustion characteristics of coking coal

2021 ◽  
pp. 014459872110490
Author(s):  
Fei Gao ◽  
Zhe Jia ◽  
Mei-ling Qin ◽  
Xiao-gang Mu ◽  
Yi-fei Teng ◽  
...  
Keyword(s):  
Sulfur Content ◽  
Photoelectron Spectroscopy ◽  
Spontaneous Combustion ◽  
Characteristic Temperature ◽  
Combustion Process ◽  
Oxidation Products ◽  
Organic Sulfur ◽  
Scanning Calorimetry ◽  
Clean Coal ◽  
Spontaneous Combustion Of Coal

Research on the spontaneous combustion of coal caused by sulfur has always been focused on pyrite in coal but has rarely considered the influence of organic sulfur. In this paper, coal samples, rather than model compounds, were used to study the influence of organic sulfur content in coal on its spontaneous combustion process. The results of X-ray photoelectron spectroscopy and thermogravimetry, differential scanning calorimetry, and mass spectrometry indicate that organic sulfur in Shuiyu clean coal exists in forms of mercaptan, thioether, sulfone (sulfoxide), and thiophene. With the decrease of organic sulfur content, the characteristic temperature points and the peak values of the exothermic curves in the process of coal oxidation spontaneous combustion all shifted toward higher temperatures. The ignition activation energy of coal also increased, and the initial and peak gas evolution temperatures of the oxidation products shifted toward higher temperatures. These findings suggest that the reduction of organic sulfur content can inhibit the oxidation process and spontaneous combustion tendency of coal. This effectively reveals the mechanism of the spontaneous combustion of coal and is of great significance to future studies in this field.

Kinetics of Wet In-Situ Combustion: A Review of Kinetic Models

2014 ◽  
Author(s):  
E. A. Cavanzo ◽  
S. F. Muñoz ◽  
A.. Ordoñez ◽  
H.. Bottia
Keyword(s):  
Kinetic Model ◽  
Crude Oil ◽  
Kinetic Models ◽  
Combustion Front ◽  
Chemical Interaction ◽  
Combustion Process ◽  
Oxidation Reactions ◽  
In Situ Combustion ◽  
Temperature Oxidation

Abstract In Situ Combustion is an enhanced oil recovery method which consists on injecting air to the reservoir, generating a series of oxidation reactions at different temperature ranges by chemical interaction between oil and oxygen, the high temperature oxidation reactions are highly exothermic; the oxygen reacts with a coke like material formed by thermal cracking, they are responsible of generating the heat necessary to sustain and propagate the combustion front, sweeping the heavy oil and upgrading it due to the high temperatures. Wet in situ combustion is variant of the process, in which water is injected simultaneously or alternated with air, taking advantage of its high heat capacity, so the steam can transport heat more efficiently forward the combustion front due to the latent heat of vaporization. A representative model of the in situ combustion process is constituted by a static model, a dynamic model and a kinetic model. The kinetic model represents the oxidative behavior and the compositional changes of the crude oil; it is integrated by the most representative reactions of the process and the corresponding kinetic parameters of each reaction. Frequently, the kinetic model for a dry combustion process has Low Temperature Oxidation reactions (LTO), thermal cracking reactions and the combustion reaction. For the case of wet combustion, additional aquathermolysis reactions take place. This article presents a full review of the kinetic models of the wet in situ combustion process taking into account aquathermolysis reactions. These are hydrogen addition reactions due to the chemical interaction between crude oil and steam. The mechanism begins with desulphurization reactions and subsequent decarboxylation reactions, which are responsible of carbon monoxide production, which reacts with steam producing carbon dioxide and hydrogen; this is the water and gas shift reaction. Finally, during hydrocracking and hydrodesulphurization reactions, hydrogen sulfide is generated and the crude oil is upgraded. An additional upgrading mechanism during the wet in situ combustion process can be explained by the aquathermolysis theory, also hydrogen sulphide and hydrogen production can be estimated by a suitable kinetic model that takes into account the most representative reactions involved during the combustion process.

scholarly journals EXAMINATION OF THE ROLE OF MOISTURE CONTENT ON THE SPONTANEOUS COMBUSTION OF COAL (SCC)

2019 ◽  
Vol 34 (3) ◽  
pp. 61-71
Author(s):  
Amir Saffari ◽  
◽  
Mohammad Ataei ◽  
Farhang Sereshki ◽  
◽  
...  
Keyword(s):  
Moisture Content ◽  
Spontaneous Combustion ◽  
Spontaneous Combustion Of Coal

Experiment Research of Coal’s Spontaneous Combustion Characters

2014 ◽  
Vol 1077 ◽  
pp. 66-70
Author(s):  
Yan Min Zheng ◽  
Jin Feng Zhang
Keyword(s):  
Low Temperature ◽  
Spontaneous Combustion ◽  
Control Measures ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
Spontaneous Combustion Of Coal ◽  
Prevention And Control Measures ◽  
And Control ◽  
Dsc Curves ◽  
Heat Released

On the basis of physical oxygen uptake, use the instrument to identify the spontaneous combustion of Yang quan coal, and combination the insulation oxide of coal as well as the TG-DSC experiment to analysis of low-temperature oxidation of coal, though the DSC curves, combined with the insulation oxide experimental to analysis the size of the heat. In the end, we can come to the conclusion about the law and the different temperature parameters of the low-temperature oxidation. At the same time, the temperature when a large number of heat released by coals oxidation were also known ,and laid a theoretical foundation to develop prevention and control measures for the spontaneous combustion of coal mines.

scholarly journals Experimental study on thermal effect and gas release laws of coal-polyurethane cooperative spontaneous combustion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Haiyan Wang ◽  
Yao Tian ◽  
Jinglei Li ◽  
Xiao Chen
Keyword(s):  
Binary System ◽  
Mass Fraction ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Great Influence ◽  
Oxygen Absorption ◽  
Gas Release ◽  
Initial Release ◽  
Combustion Simulation ◽  
Spontaneous Combustion Of Coal

AbstractThis paper presents a research on the kinetics and gas release laws of the cooperative spontaneous combustion of coal-polyurethane binary system by means of thermogravimetric analysis and spontaneous combustion simulation experiments. The coal-polyurethane binary system is more prone than individual samples to combustion. The polyurethane mass fraction has a great influence on the cooperative spontaneous combustion process. As the polyurethane mass fraction rises, the activation energies of oxygen absorption stage and pyrolysis stage decrease. The combustion residues of coal-polyurethane binary system scorches into lumps and the surfaces of the particles become rougher. During spontaneous combustion, the initial release temperatures of the four gases CO2, CO, C2H6 and C2H4 drop as the polyurethane mass fraction increases. The gas release amount of them increases with increasing polyurethane mass fraction. And the amount of CH4 decreases as the polyurethane mass fraction increases. The CO/CO2 ratio with temperature for different polyurethane mass fraction have the same trends. The results of this study have implications concerning polyurethane materials application and fire protection in coal mine.

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 Study on the Effect of Extraneous Moisture on the Spontaneous Combustion of Coal and Its Mechanism of Action

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1969 ◽  
Author(s):  
Yuguo Wu ◽  
Yulong Zhang ◽  
Jie Wang ◽  
Xiaoyu Zhang ◽  
Junfeng Wang ◽  
...  
Keyword(s):  
Technological Process ◽  
Optimization Design ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Mining Industry ◽  
Delayed Effect ◽  
Coal Spontaneous Combustion ◽  
Temperature Programmed Oxidation ◽  
Oxidation Stage ◽  
Spontaneous Combustion Of Coal

It is imperative to have an in-depth understanding of the effect of extraneous moisture on the spontaneous combustion of coal not only for the control and prevention of coal spontaneous combustion in the coal mining industry, but also for the optimization design and application of the technological process. In this study, the type of moisture in a coal body has been redefined for the first time from the perspective of disaster prevention and control, i.e., original occurrence of moisture in the coal matrix and the extraneous moisture from the technological process. A suit of coal bodies with different extraneous moisture was prepared by soaking long-flame coal with a low water content. Using a temperature-programmed oxidation test, the effects of extraneous moisture on the temperature increase rate of coal bodies and the emission characteristics of gaseous products during coal spontaneous combustion were studied. Moreover, combined with the characterization of thermal analysis and of pore structure test, the action the mechanism of extraneous moisture on the coal spontaneous combustion process was also explored. The experimental results indicated that the effect of the extraneous moisture content varied with the development of coal spontaneous combustion. In the slow oxidation stage, extraneous moisture played a physical inhibition role in the coal oxidation. In the accelerated oxidation stage, extraneous moisture exhibited a catalytic effect on the coal–oxygen reaction or directly participated in the reaction. After entering the rapid oxidation stage, a delayed effect appeared. When the coal temperature exceeded 180 °C, the spontaneous combustion characteristics of coals with different initial moisture contents gradually tended to achieved balance.

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