Influence of goaf inerting on the “three zones” and study on fire prevention and extinguishing technology in ultra-width working face of extra-thick coal seam

Due to the thickness of the coal and the width of the working face in the extra-thick coal seam and ultra-width working face, the distribution of the oxidation zone in the goaf during mining is different from that of the conventional working face, which brings difficulties to the prevention and control of coal spontaneous combustion in the goaf. Once spontaneous combustion occurs, it will seriously threaten the safety of the mine and cause huge losses. In response to this problem, By taking a coal mine in Shanxi as an example, the paper analyze the influence of nitrogen injection inertization on the oxidation zone in the goaf through theoretical analysis, on-site measurement, numerical simulation and other methods. The width of the "three zones" in the goaf area of the working face was measured, and numerical simulation was used to analyze the impact of different nitrogen injection inerting positions and nitrogen injection volume on the width of the oxidation zone. Based on this, an "Isolation-Leakage Coupled Multi-source Inertization Technology" was proposed. The results show that the width of the oxidation zone on the intake side of the ultra-width working face is 105.8m, and the width on the return air side is 102.1m, which is larger than that of the conventional working face. Nitrogen injection inerting can significantly reduce the width of the oxidation zone. The optimal nitrogen injection inerting position is 50m, and the optimal nitrogen injection volume is 2,700m 3 /h; through simulation and field measurement data analysis, the proposed "Isolation-Leakage Coupled Multi-source Inertization Technology " was implemented on the 22202 extra-thick coal seam and ultra-width working face, and the inertization of the goaf and prevention of coal spontaneous combustion were significant. The research results have scientific guiding significance for controlling coal spontaneous combustion in extra-thick coal seams and ultra-width working faces.