Experimental study on the replacement of oxygen in broken coal by inert gas under the influence of stress and flow rate

When inert gas replaces oxygen in coal, the influence of stress and inert gas flow cannot be ignored. To study the effect of inert gas flow rate on the oxygen replacement efficiency in coal under different stress conditions, through the self-developed inert gas dynamic replacement of loaded broken coal oxygen experimental system, CO2 was used as inert gas and He was used as the control group. The changes of key indicators such as outlet oxygen concentration, replacement volume, average replacement rate, and adsorbed oxygen displacement rate under different stress and flow conditions were analyzed. With the increase in axial compression, the displacement rate of adsorbed O2 by CO2 decreases, however, the outlet oxygen concentration decreases to below the critical minimum oxygen concentration required for coal spontaneous combustion more rapidly. Due to the lack of adsorption characteristics, the average displacement rate of He is significantly higher than that of CO2 under high stress. The degree of displacement of adsorbed oxygen by CO2 and He is more significantly affected by flow conditions than axial pressure conditions. The research provides an important reference for parameter optimization in inert gas fire prevention and extinguishing engineering.