Judgment And Prevention Method Of Coal Spontaneous Combustion Dangerous Area In High Ground Temperature Goaf

With the exploitation of a large amount of coal resources in the shallow part of the coal seam in China,the mining depth is increasing year by year,causing high ground temperature and high ground stress in the mined coal seam.As the mining area is in a high temperature and high humidity environment,the risk of coal spontaneous combustion(CSC)in the goaf is enhanced.In this paper,we take the prevention and control of coal spontaneous combustion in the goaf of 1303 working face as the research object,and use the combination of laboratory measurement,field observation and numerical simulation to carry out the research on the determination of CSC danger area and prevention and control methods.By simulating the characteristics of different humidity environmental conditions on CSC and the process of CSC samples at different initial temperatures through programmed temperature rise,the results showed that the effects of different humidity on CSC and oxidation process at the same temperature are different.In 30-50℃,the CO and CO2 production,production rate and exothermic intensity of 4#coal samples were larger compared with other conditions,indicating that 4#conditions were more favorable to CSC compared with other humidity in this stage;between 50～140℃,2#coal samples showed the most obvious CO and CO2 production rate;in 150～180℃,3#coal samples showed the highest CO and CO2 production rate.By studying the oxidation process of coal samples with different initial temperatures,it was found that the higher the temperature,the stronger the oxygen consumption rate of coal samples.The CSC risk of high ground temperature is studied.By analyzing the influence of coal thickness distribution,coal void distribution,air leakage intensity,coal particle size,air humidity and other factors on the process of CSC,the risk area of CSC in the goaf under high temperature surrounding will expand and develop to the deep part of the goaf and the middle of the goaf.Meanwhile,through field observation and numerical simulation,we analyzed the distribution of oxygen concentration and air leakage pattern of the goaf and obtained that the air leakage rate is 15.87%,and the range of the oxidation zone of the goaf is 58～164 m with a width of 102 m on the inlet side and 23～82 m with a width of 59 m on the return side.In view of the strong risk of CSC in high ground temperature goaf,the method of preventing and controlling CSC in high ground temperature mining areas is proposed.After the application of fire prevention measures on the 1303 working face,the changes of O2 and CO gas in the 1303 working face during the recovery period were analyzed,and the distance of the CSC oxidation zone in the inlet and return side of the high ground temperature mining area was shortened by 59 m and 29 m,respectively.the CO concentration in the return corner and return flow was less than 24 ppm.the field practice proved that this prevention and control method can effectively prevent the CSC in the high ground temperature goaf and its effect is obvious.