Study On Flue Gas Change Law Of Goaf Coal Spontaneous Combustion Area Before And After Closure

Coal is the basic energy for China's economic development and occupies an important position in China's energy system.In recent years,coal spontaneous combustion accidents often occur in goaf,even lead to gas explosion and other major accidents,resulting in casualties,waste of resources and environmental pollution.Therefore,this paper focuses on the variation law of spontaneous combustion smoke in the process of coal temperature rise and coal temperature drop after closed fire area under the condition of coal spontaneous combustion fire area in goaf.In order to study the distribution and change of coal spontaneous combustion smoke before and after the closure of the goaf fire area,a similar simulation experiment platform for the goaf was established based on a working face of Hegang Xing'an Coal Mine in Heilongjiang,and the height of the caving zone and fissure zone of the goaf was calculated.Gas sampling pipelines are arranged on the planes with heights of 1cm,10cm,and 40cm as experimental measurement points,and coal sample combustion chambers are arranged on the air inlet side of the working face to simulate the spontaneous combustion of coal in the goaf.In the experiment,the pipeline fan was used to control the wind speed of the working face to be stable.The heating plate was used to heat 100g of pulverized coal in the combustion chamber,and the temperature of the pulverized coal was monitored by a thermometer.Collect gas samples and perform gas chromatographic analysis on the gas samples to study the distribution and change of flue gas during the process of spontaneous combustion of coal in the goaf.When the coal temperature is 400?,the inlet and return air tunnels are closed,and the coal temperature continues to rise to 450?enters the cooling stage.When the coal temperature drops to 400?,325?,250?,175?,100?,gas samples are collected for chromatographic analysis,and the distribution and change of coal spontaneous combustion smoke after the closed fire area is studied and the gray correlation degree is used.The analysis method analyzes the correlation between flue gas and coal temperature changes,and the research results are as follows:During the heating process of coal spontaneous combustion in the goaf,with the increase of coal temperature,the concentration of coal spontaneous combustion flue gas has an overall upward trend,which has a good correlation with temperature.The flue gas concentration distribution at different heights of the goaf(z=1cm,10cm,40cm)is affected by the leakage air flow and the thermal buoyancy generated by the spontaneous combustion of coal,showing different distribution results.The lower part of the goaf(z=1cm)is affected by the goaf.The air leakage in the area has a greater impact.The air leakage flow moves the flue gas to the deep part of the goaf,and the other part migrates to the return air side,forming a higher concentration area;the middle part of the goaf(z=10cm)is caused by the heat generated by the high temperature of coal spontaneous combustion.The buoyancy and the air leakage flow together to form a vortex around the fire area,causing smoke to accumulate between the spontaneous ignition point and the working surface,forming a high-concentration smoke area;the upper part of the goaf(z=40cm)is less affected by the air leakage flow,and the heat The effect of buoyancy is greater,and smoke accumulation is formed in the upper part of the fire zone.The simulation results show that the temperature of the coal in the goaf increases after spontaneous combustion,which reduces the density of the gas at the spontaneous combustion point and forms a density difference with the surrounding gas.Under the action of gravity,thermal buoyancy appears.The updraft generated by the buoyancy interacts with the air leakage in the goaf.The formation of smoke vortex motion,resulting in the migration and accumulation of smoke.After the fire zone is closed in the goaf,the change of the smoke concentration in the goaf is divided into two stages.In the first stage,the coal temperature drops,but there is still a large amount of smoke generated,resulting in an increase in the smoke concentration in the fire zone.Further down,the amount of coal smoke emission is lower than the amount of flue gas output,the flue gas concentration enters the descending stage,and finally the flue gas concentration at each layer is evenly distributed.The location of the bottom of the closed goaf(z=1cm)is due to the gap between the air inlet lane and the combustion chamber and the outflow of flue gas,which makes the fire zone and the inlet side of the flue gas concentration lower;the central measuring point(z=10cm)is affected by the outflow of gas The combined effect of thermal buoyancy changes greatly with temperature.When the coal temperature is higher,the buoyancy effect obviously forms the accumulation of flue gas.As the coal temperature decreases,the effect of flue gas outflow becomes more obvious,and finally forms a low flue gas concentration area at the inlet corner.The concentration distribution becomes more balanced with the decrease of coal temperature;the upper measuring point(z=40cm)is heated and buoyant when the coal is high temperature,and a high smoke concentration area is formed above the spontaneous combustion area of coal.As the temperature decreases,the outflow and buoyancy of the smoke are not affected.Obviously,the flue gas diffuses freely and the concentration distribution is uniform.Compared with the middle measuring point,the equilibrium temperature at the upper measuring point appears earlier.The gray correlation analysis of the flue gas concentration and temperature change at each measurement point during the cooling process found that the C₂H₄ concentration has the best correlation with the temperature change during the spontaneous combustion extinguishing process of coal,which can better characterize the cooling process of coal.This dissertation includes 39 figures,7 tables and 80 references.