Study On The Law Of Coal Spontaneous Combustion In Goaf By Long-distance Gas Drainage In Tashan Mine

Coal spontaneous combustion is one of the major disasters that affect the safety production of coal mines.With the increase in coal mining,the safety accidents in the coal industry have become more serious.Aiming at high-concentration gas mines with high coal spontaneous combustion risk during the process of extraction,it is of great significance to carry out research on the distribution law of coal spontaneous combustion danger areas and the prevention and control theory and technology for reducing coal mine safety accidents and ensuring the safety of the people's lives underground.This article takes the goaf of 8204-2 working face of Tashan Mine,a high-concentration gas mine in Tongmei Group as an example.For the topography of some areas above it,the roof drainage roadway cannot be arranged,and the ground vertical drilling can only be arranged at the starting point of the mining for long-distance gas.In the case of drainage,a numerical analysis method is used to construct a porous medium model in the goaf to study the effect of long-distance gas drainage on the coal spontaneous combustion law in the goaf under complex terrain conditions,and the goaf is divided according to the coal spontaneous combustion danger zone division theory,and compared with the three belts obtained from the field measurement data on the working face to prove the accuracy of the simulation results,and then study the adjustment of different propulsion lengths and air volume adjustment under the conditions of long-distance gas extraction to the coal spontaneous combustion danger zone of the goaf.Finally,on this basis,further numerical simulation analysis of the prevention effect of spontaneous combustion of coal in the empty area of different nitrogen injection amounts and positions was carried out to determine the optimal nitrogen injection parameters.the result shows:(1)Compared with gas extraction under normal conditions,long-distance gas extraction under complex terrain conditions will increase the oxygen concentration in the goaf and significantly increase the risk of coal spontaneous combustion.When the working face advancement length is 110 m,on the side of the the inlet air lane,the range of the heat dissipation band is roughly between 0 and 25 m,which is an increase of 25% from the normal range,the range of the self-ignition zone is between 25 and 68 m,which is an increase of 79.2% from the normal range,the suffocation zone range is after 68 m from the working surface;on the side of the return air lane,the range of the heat dissipation zone is roughly between 0 and 20 m,which is an increase of 11.1% compared with the normal range,the range of the self-ignition zone is between 20 and 88 m,which is an increase of 36% from the normal range,the suffocation zone range is after 88 m from the working surface.The measured data of the working face and the FLUENT simulation results are highly consistent,which verifies the accuracy of the simulation results;(2)As the propulsion distance increases,the oxidation zone range of the goaf increases;when the propulsion distance exceeds 55 m,the spontaneous combustion zone increases greatly(taking the propulsion distance between 55 and 65 m as an example),on the side of the inlet air lane,the ratio of the increase in the spontaneous combustion zone to the increase in the propulsion length is 0.7,which is 133% higher than when the propulsion length is between 35 m and 55m;on the side of the return air lane,the ratio of the increase in the spontaneous combustion zone to the increase in the propulsion length is 0.8,which is 167% higher than when the propulsion length is between 35 m and 55 m.The spontaneous combustion zone width reaches 80 m when the advancing distance is 150 m,and the risk of spontaneous combustion of leftover coal increases significantly.Therefore,when the propulsion distance exceeds 55 m,the possibility of spontaneous ignition increases,and it is necessary to combine underground nitrogen injection to ensure safe production;(3)After the air volume of the working face is adjusted to the optimal air volume of 3000m3 / min,the range of the coal spontaneous combustion risk area has been reduced to a certain extent,as the width of the heat dissipation zone is reduced by 5m,the width of the oxidation zone is reduced by 15 m,and the suffocation zone is toward the working face moved by 20m;(4)When the nitrogen injection volume is 2000m3 / h,on the inlet air side,the width of the heat dissipation zone is about 15 m,which is 25% lower than that without nitrogen injection,and the oxidation zone is 8m,which is 71.4% lower than that without nitrogen injection;on the side of the return air lane,the width of the heat dissipation zone is about 4m,which is 33.3% lower than that without nitrogen injection,and the oxidation zone is 11 m,which is 64.5% lower than that without nitrogen injection.It is found that nitrogen injection significantly reduces the oxygen concentration in the goaf,make the dangerous area of coal spontaneous combustion smaller,and the effect of inerting is remarkable.After comprehensively considering the factors such as preventing coal spontaneous combustion in the mined-out area and the safety of the operators in the roadway,the optimal nitrogen injection volume is selected to be 2000m3 / h.Nitrogen injection downwind 35 m away from the working surface in the oxidation zone close to the inlet air side,the best inerting effect.The article has 18 pictures,14 tables,and 79 references.