Study Of Coal Spontaneous Combustion Prediction On Condition Of Gas Extraction In Xiashijie Coalmine

Many coalmines in China are high-methane spontaneous combustion ones, where spontaneous combustion are quite serious. Due to gas extraction, air leakage in the gob of high-methane mines is different from those in low-methane mines , which caused spontaneous combustion in the high-methane mine very complicated and difficult to predict. In the present study, spontaneous combustion modeling experiment is carried out to model the whole process of Xiashijie coal spontaneous combustion from room temperature to over 380 degree centigrade. Character temperature including index gases, critic loose coal depth, critic air leakage intensity and critic oxygen concentration of coal spontaneous combustion are tested with the experiment.A couped numeric model of flow, diffusion, absorption and desorption as well as chemical reaction is set up to to simulate the field of air concentration and flux. The spontaneous combustion danger zone and possible time is determined with the simulation result and the theory of spontaneous combustion patition. It proved that in the 215 workface of Xiashijie coalmine, (1) the largest air leakage spot is near the gas extraction port, and air leakage intensity in thr air outlet side of the workface is larger than air inlet one, the farther it is from the workface, the smaller the oxygen concentration is except that near gas extraction port where oxygen concentration is lower; (2) self-heating zone near the air inlet side of the gob is of the widest, where the boundary of choking zone is 85m away from the workface, of the heat dissipation zone is 15m away, and the width of self-heating zone is 70m; (3) the critic workface movement velocity of spontaneous combustion is 1.6m/d, which means when the velocity is larger than 1.6m/d, there is no danger of coal spontaneous combustion in the gob; nevertheless, spontaneous combustion may take place when the velocity of workface movement is smaller than 1.6m/d for 45d continuously. The study is very important for theoretical instruction of prevention and fathering spontaneous combustion in high-methane coalmine on comdition of gas extraction.