| Spontaneous combustion of leftover coal in the goaf is one of the common thermodynamic disasters in coal mines,which seriously threatens the life and safety of underground workers.my country has basically entered the stage of deep mining in coal mines,and the impact of high ground temperature and high ground stress on coal spontaneous combustion is becoming more and more significant.The spontaneous combustion of coal in the goaf is the result of stress-temperature-atmosphere multi-field coupling.This paper uses a combination of experiment and numerical simulation to study the spontaneous and spatial evolution mechanism of the oxidation and temperature rise of the crushed coal under pressure.Provide theoretical basis for detection of spontaneous ignition source location and prevention and control.The research is based on the self-developed stress-temperature-atmosphere coupling experiment platform of crushed coal under pressure.According to the actual conditions of the mine and similar simulation criteria,the experimental parameter conditions for the oxidation and temperature rise of the pressure-bearing crushed coal were determined,which made up for the lack of sufficient consideration of the influence of axial stress on the spontaneous combustion of coal in the current study of coal spontaneous combustion.According to the temperature programmed oxidation characteristic experiment of crushed coal under 0,3,6,9,12,15 MPa axial compression conditions,the output law of various iconic gases at the outlet was obtained.Analyzing the experimental results through the theories of mass and heat transfer,porous media seepage,and secondary crushing,it is found that the production laws of carbon monoxide and carbon dioxide are similar,and their concentrations increase with the increase of coal temperature,and first increase with the increase of axial pressure.After falling.The entire experimental process was accompanied by the production of methane gas.After the critical temperature(343K),as the axial pressure increased,the methane concentration first increased and then decreased,and at the same time caused the initial temperature point of ethane and ethylene production to advance.Studies have shown that with the continuous increase of the axial pressure,the coal-oxygen recombination reaction presents the effect of first promoting and then inhibiting,and the coal-oxygen recombination reaction is the most intense under the condition of 12 MPa axial pressure.Based on the experimental platform for the oxidation and temperature rise of the crushed coal under pressure,the physical and mathematical models corresponding to the coal sample chamber are established and meshed.Based on the actual oxygen concentration value,the oxygen consumption rate function under 12 MPa axial pressure,the carbon monoxide and carbon dioxide generation rate function and the heat release intensity function were corrected.Using COMSOL simulation,the distribution and change of temperature field and concentration field inside the coal sample chamber are studied.The study found that with the increase of coal temperature,there is always a high temperature accumulation area.The distance and range between this area and the air inlet first increase and then decrease with the increase of coal temperature,and finally stabilize at 21.16 mm from the air inlet.Place.The oxygen concentration at each point in the furnace shows an overall downward trend with the increase of coal temperature,and the overall concentration of carbon monoxide and carbon dioxide shows an upward trend.The gas flow and the differences in the internal heat storage conditions and chemical reaction rates together cause the oxygen,carbon monoxide,and carbon dioxide to fall above and below.Layered form is distributed in the furnace.Due to the existence of the critical high temperature accumulation area,when the maximum coal temperature reaches 524 K,a low oxygen concentration,high carbon monoxide concentration and high carbon dioxide concentration area will be formed at 22.03 mm,22.17 mm and 22.91 mm from the air inlet.Each gas in this area The concentration forms a clear contrast with the surrounding area.The results of this study show that the location of the high temperature point of coal spontaneous combustion in the goaf is concealed and easy to move,which is the focus and difficulty of the prevention and control of coal spontaneous combustion in mines.The research on the characteristics of coal spontaneous combustion oxidation and temperature rise based on the stress-temperature-atmosphere coupling is more suitable for the actual environmental conditions in the goaf,and has important theoretical guiding significance for the prevention and control of coal spontaneous combustion. |
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