Study on numerical simulation of CO2 injection fire prevention and extinguishing technique in goaf of Jiudaoling Mine

In order to restrain the coal spontaneous combustion danger occurred in the goaf of Jiudaoling Mine, a carbon dioxide injection method of the goaf was applied to the fire extinguishing. In order to study the location and flow of the rational carbon dioxide injection, a sealed oxygen consumption experiment was conducted on the coal samples from Jiudaoling Mine. An oxygen consumption rate of the coal samples was obtained and the critical oxygen concentration in the suffocated zone was determined. The oxygen consumption coefficients of the coal sample obtained from the sealed oxygen consumption experiment were applied to the numerical simulation experiment of the carbon dioxide injection in the goaf. With the location adjustment of the carbon dioxide injection inlet, the width of the oxygen concentration zone in the goaf was obtained during the carbon dioxide injection with different location. With the injection location steadily entered in the internal part of the goaf, the width of the natural oxidation zone would firstly be reduced and then would be in an increased tendency. Finally，the optimum location of the carbon dioxide injection in Jiudaoling Mine was at the internal part of the air income side in the goaf with a distance of 43 m to the coal mining face. The location to adjust the carbon dioxide injection flow could have the results of a negative index between the carbon dioxide injection flow at the internal air income side of the goaf and the width of the natural oxidation zone. In combination with the spontaneous combustion period and other parameters of the coal samples from Jiudaoling Mine, the optimum injection flow was 158 m3/h finally determined. Under the conditions of the optimum location and the optimum injection flow, the carbon dioxide injection could effectively reduce the width of the natural oxidation zone in the goaf and could restrain the spontaneous combustion danger occurred in the goaf of Jiudaoling Mine.