scholarly journals Numerical Simulation of Coal Spontaneous Combustion around a Borehole Induced by Negative Pressure Gas Drainage

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Youxin Zhao ◽  
Qingjie Qi ◽  
Xinlei Jia ◽  
Yingjie Liu ◽  
Jingwen Zhang
Keyword(s):  
Oxygen Concentration ◽  
Negative Pressure ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Extraction Process ◽  
Gas Extraction ◽  
Growth Trend ◽  
Gas Drainage ◽  
Gas Seepage ◽  
Spontaneous Combustion Of Coal

The suction negative pressure is an important factor affecting the spontaneous combustion of coal around a borehole. Because the mechanism of suction negative pressure in the gas extraction process remains unclear, a constant suction negative pressure is often used in coal mines, leading to a low efficiency of gas extraction in deep coal seams. Moreover, the coal body easily undergoes spontaneous combustion during the extraction process, which is not conducive to safe mining. To study the effect of the suction negative pressure near the end sealing section, a numerical model of the combustion process around a borehole under the influence of suction negative pressure was established using COMSOL. The variation laws of the gas seepage velocity, oxygen concentration, and coal temperature in the borehole cycle were analyzed, and the gas suction negative pressure under different sealing parameters was optimized to ensure efficient gas extraction and prevent the spontaneous combustion of coal. The results showed that the negative pressure of extraction provides the power required for gas seepage into the borehole, and the gas flow rate increases with increasing negative pressure of extraction, exhibiting a linear growth trend. The range of the coal suffocation zone around the sealing section decreases with the increase in the negative pressure. With the extension of the gas extraction time, the oxygen concentration decreases rapidly, and the inflection point advances with the increase in the negative pressure. When the negative pressure of gas extraction is <40 kPa, the range of the high-temperature area around the block increases with the negative pressure of gas extraction. Based on the present situation of the spontaneous combustion induced by gas drainage in the Pingdingshan No. 10 Coal Mine, different sealing parameters should be set with different negative pressures of extraction, and the negative pressure of extraction should not exceed −18 kPa when the sealing depth is 20 m and the sealing length is 8 m in the 24130 working face. These parameter settings can help effectively prevent spontaneous combustion during the extraction process.

scholarly journals Prediction Model for Spontaneous Combustion of Coal around Boreholes Using Bedding Gas Drainage

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Youxin Zhao ◽  
Qingjie Qi ◽  
Xinlei Jia
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Negative Pressure ◽  
Spontaneous Combustion ◽  
Orthogonal Test ◽  
Gas Drainage ◽  
Positive Linear Correlation ◽  
Drainage Hole ◽  
Spontaneous Combustion Of Coal ◽  
Fractured Coal

To accurately and reliably predict the time of spontaneous combustion of fractured coal around a borehole induced by gas drainage along the seam, this study performed an orthogonal test taking the No. 10 Coal Mine of Pingdingshan as the research object, in terms of the suction negative pressure and coal seam buried depth. COMSOL Multiphysics was used to model the orthogonal test results, and a multielement statistical analysis of four factors and their relationships with the spontaneous combustion of coal around the borehole and a single-factor analysis in line with the site conditions were performed on the modeling results through multiple regression. The results showed a nonlinear regression relationship between the sealing hole length, sealing hole depth, negative pressure, and coal seam depth and the spontaneous combustion of the coal around the gas drainage borehole; the prediction regression model is significant. Taking the field gas drainage in the No. 10 Coal Mine of Pingdingshan as an example, the relationship between the time of spontaneous combustion of gas drainage and the drainage pressure follows a power of two. When the drainage negative pressure is less than 45 kPa, the coal around the borehole is more likely to undergo spontaneous combustion with increasing pressure, and the sealing hole length has a positive linear correlation with the time of spontaneous combustion of the coal around the borehole. When the sealing hole length is 23 m, the time of spontaneous combustion of the coal around the gas drainage hole is >500 days, and the coal around the borehole does not easily undergo spontaneous combustion. When the sealing depth is 15 m, the time of spontaneous combustion of the coal around the gas drainage hole is 76 days, which is most likely to cause spontaneous combustion.

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.

scholarly journals Research on determining reasonable negative pressure based on the control of the goaf

2021 ◽  
Vol 69 (4) ◽  
pp. 121
Author(s):  
Wang Yue-hong ◽  
Wu Yi ◽  
Zhang Jiu-ling ◽  
Li Zhi
Keyword(s):  
Negative Pressure ◽  
Combustion Zone ◽  
Heat Dissipation ◽  
Spontaneous Combustion ◽  
Three Dimensional ◽  
Gas Extraction ◽  
Deep Part ◽  
Contour Map ◽  
Beam Tube ◽  
Dimensional Distribution

In order to study the law of spontaneous combustion in goaf under the condition of gas extraction, the method of beam tube monitoring and numerical analysis is adopted to obtain three dimensional distribution of oxygen concentration and contour map under the condition of different negative pressure. Based on the way of regression analysis, reasonable negative pressure are determined. The results show that with the increase of negative pressure, the spontaneous combustion “three-zone” in goaf: the heat dissipation zone and the spontaneous combustion zone become wider and the suffocation zone narrows. At the same time, the trend of spontaneous combustion zone presents to the deep part of the goaf; the amount of gas extraction increases first and then decreases with the increase of negative pressure. Combined with the trend of spontaneous combustion zone and the amount of gas extraction in goaf, and the reasonable negative pressure value is 32kpa and verified.

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.

Study on Parameters of Gas Extraction in Spontaneous Combustion in Goaf and Comprehensive Prevention Process of Gas in Hongmiao Mine

2014 ◽  
Vol 962-965 ◽  
pp. 973-979
Author(s):  
Xiang Li
Keyword(s):  
Spontaneous Combustion ◽  
Break Line ◽  
Gas Extraction ◽  
Gas Explosion ◽  
Gas Drainage ◽  
Comprehensive Management ◽  
Working Face ◽  
The Face ◽  
Extraction Parameters ◽  
Selection Of

Aimed at the comprehensive management of gas and spontaneous combustion in goaf of 5-2S fully mechanized caving face in five district of Hongmiao coal mine. The impacts on the air flow field and concentration distribution of the goaf are analyzed, that the changes of gas drainage value, and the location of drainage outlet as well as injection capacity of nitrogen. The results show that, the larger of the volume of gas drainage, the greater risk of gas explosion and spontaneous combustion. Appropriate increasing gas drainage volume is used to ensure the safety of the working face, with injecting nitrogen or accelerating the speed of face promote. The drainage outlet location should also be in an appropriate range (5~25 m) after the break line of the face. The result has important guiding significance in goaf of inflammable thick seam of gas mine, on the selection of gas extraction parameters, which is reasonable to prevent both gas explosion accident and spontaneous combustion caused by drainage excessive.

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.

scholarly journals Research on the Damping Performance of Mining Highly Efficient Water-Retaining Colloidal Material Against the Spontaneous Combustion of Coal

2021 ◽  
Vol 45 (4) ◽  
pp. 317-327
Author(s):  
Yongfei Jin ◽  
Li Yan ◽  
Yin Liu ◽  
Chuansheng Li
Keyword(s):  
Water Retention ◽  
Spontaneous Combustion ◽  
Characteristic Temperature ◽  
Combustion Process ◽  
Resistance Mechanism ◽  
Base Material ◽  
Coal Oxidation ◽  
Colloidal Material ◽  
Highly Efficient ◽  
Spontaneous Combustion Of Coal

In order to solve the shortcomings of the traditional mining anti-extinguishing gel material such as low strength and poor water retention, a high hydrocolloid anti-extinguishing material was developed with sodium alginate and light calcium carbonate as the base material and gluconolactone as the retarder, which was mixed and reacted. The base material ratio of highly efficient water-retaining colloidal material for coal void filling was determined as 2% SA + 0.5% PCC + 1% GDL with a moulding time of 4.5 min, while the base material ratio of highly efficient water-retaining colloidal material for extinguishing high temperature fires was 2.5% SA + 1% PCC + 1% GDL with a moulding time of 2.5 min. The highly efficient water-retaining colloidal material was found to reduce the concentration of signature gas and delay the characteristic temperature point and increase the activation energy of coal oxidation, which indicates that the highly efficient water-retaining colloidal material can effectively inhibit the spontaneous combustion process of coal at low temperature stage. Infrared spectroscopy experiments were conducted to investigate the microscopic resistance mechanism of the highly efficient water-retaining colloidal material, and the results showed that the highly efficient water-retaining colloidal material mainly reduce the activity of Ar-C-O-, -COO-, -CH3, -CH2 and -OH in coal to inhibit the spontaneous combustion of coal.

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