Distribution Relationship Between Nitrogen Injection Flow and Spontaneous Combustion “Three Zones” in Goaf of Short-wall Fully Mechanized Caving Face in Near-straight Coal Seam

There is a large amount of residual coal and complicated air leakage in goaf of short-wall fully mechanized caving face near vertical coal seam in Wudong Coal Mine, which is easy to cause spontaneous combustion fire. Therefore, the nitrogen injection fire-fighting technology is taken as the main means of spontaneous combustion prevention and control at the working face of coal mining. Nitrogen injection into goaf will inevitably affect the distribution range of spontaneous combustion “three zones” in goaf. In order to investigate the variation laws of the distribution range of goaf spontaneous combustion “three zones” under different nitrogen injection flow rates, the oxygen concentration at different positions of goaf under three different conditions of non-nitrogen injection, low-flow nitrogen injection and high-flow nitrogen injection was determined by using the method of embedded beam tube. According to the oxygen concentration index of goaf spontaneous combustion “three zones”, the distribution range of “three zones” is divided. Through the comparison and division results, it is clear that with the increase of nitrogen injection flow rate in goaf, the boundaries of the “three zones” all move towards the working face, the width of the heat dissipation zone and the oxidation zone will decrease, and the heat dissipation zone will basically disappear after nitrogen injection at a large flow rate.