Optimization Study of Nitrogen Injection Fire Prevention and Extinguishing Technology for Coal Spontaneous Combustion in Goaf

The spontaneous combustion of residual coal in goafs poses a serious threat to mine safety. To examine this problem, taking a coal mine in Henan Province as an example, this study analyzes the air leakage laws and areas prone to coal spontaneous combustion (CSC) in the goaf through field observations and numerical simulations, employing the nitrogen injection to inert goaf method to prevent and control CSC. The results indicate that as the nitrogen injection location advances deeper into the goaf, the width of the oxidation zone initially decreases and then increases. With increased nitrogen injection volume, both the area and maximum width of the oxidation zone gradually decrease. The optimal nitrogen injection location is 30 m from the working face, with an injection flow rate of 800 m³/h. After implementing a comprehensive fire prevention and control technology in the goaf of the fully mechanized caving face, the goaf's air leakage significantly decreased. The O₂ concentrations on both the intake and return sides of the goaf initially dropped rapidly, then slowed down gradually. The CO concentration in the upper corner dropped from 0.0045% to 0.00036%. The research results are of scientific guiding significance for the control of air leakage in goafs and the prevention of coal seam fires.