Numerical simulation on the spontaneous combustion of loose coal in the top-coal caving region of coal drift

The spontaneous combustion hazard of loose coal in the top-coal region not only affect the normal production of working face, but also threat the safety of the coal miners. Based on the analysis of characteristics of the top-coal caving region of the roadway and factors of coal spontaneous combustion, the 3-D mathematical model of spontaneous combustion of loose coal in the top-coal region was proposed using the theories of fluid dynamics in porous medium, heat transfer and mass transfer. By using the finite element method, the velocity field of air leakage, the temperature field and the oxygen concentration field were obtained during the combustion process of loose coal in the top-coal caving region in Qishan Coal Mine. The most possible area where spontaneous combustion might take place was specified and the mechanism of coal spontaneous combustion in the top-coal region was analyzed. The results show that the air leakage rates increase with the increasing of the porosity of loose coal and there exits the most possible combust area which is the key place to prevent the fire in the fields. The validity of the numerical simulation results is verified by the measured data.