Study On The Law Of Spontaneous Combustion Of Residual Coal In The Goaf Of Xie Gou Mine

The development of coal resources in China is accelerating the transfer to the western region.The coal seams in the central and western mining areas are thick and shallow,which makes the problem of oxidative spontaneous combustion serious.The presence of residual coal in the goaf has become a key area for the prevention and control of coal spontaneous combustion disasters.Xiegou Coal Mine is a large-scale mine affiliated to Shanxi Coking Coal Group.The company has not done any research on the natural ignition law of coal in the goaf during the face mining process.This paper takes the inclined ditch mine as an example for 107 and 205 mining of thick coal seams.The law of spontaneous combustion of residual coal in the goaf of the working face was studied.The purpose is to provide some guidance for fire prevention and extinguishing work in goaf of two working faces.Experiments were carried out on the thermogravimetric change of coal samples under different oxygen concentration and heating rate of coal samples of 107 and 205working faces in Xiegou mine.The oxidation kinetic parameters of two coal samples,activation energy E and pre-exponential factor A,were carried out by Starink method.The results show that the kinetic parameters of the two coal samples show a decrease with the increase of the conversion rate in the water evaporation stage,and increase slightly with the increase of the conversion rate in the oxygen absorption and weight gain stage,and the kinetic parameters.The value does not change significantly with the increase of oxygen concentration in the water evaporation stage.In the phase of oxygen absorption and weight gain,when the conversion rate is low,the change with the increase of oxygen concentration is still not obvious,and when the conversion rate is gradually increased,it shows a tendency to decrease with the increase of oxygen concentration.The constant temperature test was carried out on the coal samples of 107 and 205working faces.Combined with the kinetic parameters measurement results,the Frank-Kamenetskii spontaneous combustion model was used to calculate the critical stacking thickness of coal spontaneous combustion at different oxygen concentrations and temperatures of the two working face coal samples.The results show that for the coal samples of 107 and 205 faces,the critical stacking thickness of spontaneous combustion and the concentration of oxygen and the temperature are negatively correlated.The higher the oxygen concentration and the higher the temperature,the smaller its critical packing thickness.This is unfavorable for the prevention and control of spontaneous combustion of residual coal.The on-site observation of the slump and air leakage in the shallow area of the107 and 205 working faces was carried out.Based on the"O"ring theory,a three-dimensional mathematical model of the span porosity distribution in the goaf was established,The SF₆ gas was used to measure the wind leakage velocity in the shallow part of the goaf of the two working faces and comparative analysis.The ANSYS software was used to simulate the diffusion and migration of SF₆ gas in the goaf and compare it with the field measurement.The results show that both the 107and 205 working face goaf have the problem that the suspended roof distance is long and the slump condition is poor,and the air leakage of the 205 working face is more serious than the 107 working face.The gas and temperature changes in the goaf of the working faces of 107 and 205were observed.The combined results of the measured results and numerical simulations showed that the oxygen concentration of the 107 surface gradually decreased with the increase of the goaf depth,while the carbon monoxide concentration and temperature increased first and then decrease,According to the oxygen concentration of 4%to 18%,the range of natural ignition hazard is analyzed.Combined with the statistical thickness of the residual coal and the calculated critical thickness of spontaneous combustion,it is found that when the oxygen concentration is lower than 8%,there is no risk of spontaneous combustion;The oxygen,carbon monoxide and temperature changes in the goaf of the 205 working face are not obvious with the increase of the goaf depth.The analysis shows that although the 205air leakage is more serious,the critical pile thickness solution indicates that the thickness of the coal in the goaf is always lower during the observation period.The critical thickness causes the residual coal to always be in equilibrium with the heat generated by oxidation,which is almost equal to the amount of heat dissipated to the outside,and there is almost no heat accumulation.Therefore,the reaction between coal and oxygen is slow,and the risk of spontaneous combustion is low too.