Study on Coal Spontaneous Combustion Dangerous Zone Under Different Air Leakage in the Shallow Buried Coal Seam Fissure

Abstract

ABSTRACT In the western region of China, the coal seam is shallowly buried. Overburden fissures readily develop upwards through the surface, and provide channels for wind to flow into the gob. Here, a model for the coal spontaneous combustion in gob caused by air leakage from fissures in shallow coal seams was established. The accuracy of the model is verified by comparing the oxygen concentration on the inlet and outlet sides of the field monitoring data with the results of numerical simulation. In addition, the distribution of oxygen concentration and wind speed in gob and their influence on spontaneous combustion dangerous zone were studied by numerical simulation when the air leakage volume varied from low to high (36–600 m3/min). The results showed no significant change in the distribution ranges of oxygen concentration and wind speed along the Z-direction when there is no air leakage from the gas conducting fissure in the gob. With the increase of air leakage, the oxidation zone defined by oxygen concentration moves to the depth of the gob, and the oxygen concentration near the fissure increases. In addition, the oxidation zone defined by the wind speed moves significantly deeper into the mining area, and the wind speed is higher at the location corresponding to the fissure close to the working face, and the overall symmetrical distribution of the flow field in the mining area. According to the oxygen concentration and wind speed, the size of dangerous zone initially increased, before decreasing and finally plateauing.