Study On Control Technology For Spontaneous Combustion In Goaf Of Simultaneous Production In Close Distance Coal Seams

The close distance coal seams widely occur in China. While the close distance coalseams are simultaneously mined, a lots of slit channels will be formed between thegoafs of close coal seams and air leakage also take place in goafs. There are manydifferences in gas delivery law between multi-seam coal and single coal seam mined. Itis so difficult to accurately confirm the dangerous area of spontaneous combustion ingoaf, and it result in the difficulty to prevent and control the spontaneous combustion ingoaf. In this paper, aiming at the close collaborative mining of3#and4#close coalseam in Nanyangpo coal mine，a stress distribution test was conducted on the scene. Atthe same time, the reasonable malposition was confirmed by applying the numericalcalculation software to resolve. There were a large number of communicative cracksbetween the upper and lower seams and leakage between the coal seams，and thedistribution rule of coal spontaneous combustion danger zone was also more complex. According to the practical condition, the permeability experiment was carried out. Thegas flow mathematical model of goaf was presented based on a reasonable assumption.Based on the index system of upper limit of the wind speed and the lower limit ofoxygen concentration，the determination mechanism of dangerous area in goaf wasestablished. The flow field in the gob was calculated by using the numerical calculationsoftware COMSOL Multiphysics. The flow fields of the upper and lower seams in thegob were numerically simulated for different malposition，and the relationship functionwas obtained between malposition and the danger area in the gob. Based on the law ofunderground pressure and combining the width of spontaneous combustion zone in goaf,the technology of nitrogen injection was applied to prevent the spontaneous combustionof goaf. Through calculation and field monitoring, the reasonable quantity of nitrogeninjection was confirmed based on the spontaneous combustion period and mining speedof working face. According to the nitrogen injection capacity of field apparatus, thedetermined reasonable malposition was89m to ensure the safety mining and mineproduction, and to prevent the occurrence of spontaneous combustion of goaf. The goodeconomic and social benefits were obtained simultaneously.