Study on the Optimization of CO₂ inerting parameters in easily permeable compound goaf

The gas flow pattern in narrow coal pillar composite goaf is very complex. It is difficult for us to choose the appropriate injection parameters for inert gas injection technology. Inert gas is prone to influx into the workspace. To address the above issues. We adopted a combination of theoretical analysis and numerical simulation method and Established a mathematical model for gas transportation in narrow coal pillar composite goaf. We studied the gas flow characteristics of the composite goaf. Based on the above operations we had the results that the overall oxidation zone moved towards the working face 7271. Oxidation zone reduced width from 29 meters to 15 meters. CO₂ moved towards the deep part of the goaf and the direction of the return air roadway. As the gas injection rate increased, the maximum width of the oxidation zone inside the coal pillar decreased from 3.77 m to 1.76 m, indicating that the coal pillar enhanced the effect of isolating O₂. CO₂ has a larger diffusion range in the direction of strike and a smaller diffusion range in the direction of inclination in adjacent goaf 7269. CO₂ has a more significant effect on inhibiting O₂ diffusion after increasing the injection volume. The optimal CO₂ injection rate of 750 m³/h was determined by using math ematical models.