Control of spontaneous combustion of coal in goaf at high geotemperatureby injecting liquid carbon dioxide: inertand cooling characteristics of coal

Abstract

The spontaneous combustion of coal in goaf at high geo temperatures is threatening safety production in coalmine. The TG-DSC is employed to study the variation of mass and energy at 4 atmospheres (mixed gases of N2, O2 and CO2) and heating rates (10°C/min) during oxidation of coal samples. The apparent activation energy and pre-exponential factor of coal oxidation decrease rapidly with increasing theCO2 concentration. Furthermore, its reaction rate is slow, its heat released reduces. Based on the conditions of 1301 face in the Longgucoalmine, a three-dimensional geometry model is developed to simulate the distributions stream field and temperature field and the variation characteristics ofCO2 concentration field after injecting liquidCO2. The results indicate that oxygen reached to depths of˜120m in goaf, 100m in the side of inlet air, and 10m in the side of outlet air before injecting liquidCO2. After injecting liquidCO2for 28.8min, the width of oxidation and heat accumulation zone is shortened by 20m, and the distance is 80m in the side of working face and 40˜60m in goafin the direction of dip affected by temperature.