A Numerical Study on the Influence of CO2 Injection Location and Flow Rate on the Oxidation Zone in Goaf

The spontaneous combustion of coal represents a common and serious safety challenge in underground mining. A frequent cause of mine fires is the ignition of residual coal accumulated in goafs. Based on the governing equations of continuity, momentum, and energy conservation, combined with the theory of flow through porous media, a three-dimensional numerical model was developed to simulate CO2 injection for fire prevention in coal goafs. Using COMSOL Multiphysics software, the effects of different CO2 injection parameters (location and flow rate) on oxygen distribution and the range of the oxidation zone within the goaf were investigated. The results indicate that with an injection point 15 m from the working face and a flow rate of 4.41 m3/min, the width of the oxidation zone was most significantly reduced, effectively suppressing the occurrence of coal spontaneous combustion. The location of the injection point was found to have a greater impact on the inerting effect than the injection flow rate. This study provides a theoretical basis and parameter optimization guidelines for CO2 injection in goaf areas for fire prevention and control.