Comparative study of single inert gas in confined space inhibiting open flame coal combustion

Abstract Mine fires can often cause tremendous disasters in underground coal mining. Therefore, a comparison of the inhibiting effect of inert gases on open flame coal combustion has significance in reducing the loss of coal to spontaneous combustion. In this study, experiments were performed to suppress open-fire coal combustion using inert gas (N2/CO2) extinguishing agents at different flow rates. The changes in the flame surface area during the experiment were analyzed, and the characteristics and inhibiting efficiency of N2/CO2 were investigated by combining the change in index gas concentration and a CHEMKIN-based numerical simulation. The results showed that N2/CO2 exhibit different flame suppression effects during the coal open fire extinguishing experiments: while N2 linearly reduced the flame surface area, CO2 exhibited an exponentially reducing effect; similarly, the fire extinguishing time taken by CO2 was less than that of N2. Moreover, a comprehensive analysis of the change in the concentration of the marked gas and the CHEMKIN-based simulation calculations showed that N2 mainly extinguishes fire by dilution, while CO2 can also function as a combustion agent that inhibits the forward reaction process of the chain reaction, making the extinguishing effect of CO2 stronger than that of N2. The index gas concentration change and fire extinguishing effect in the numerical simulation and experimental results were highly consistent, confirming the difference between the fire extinguishing principles of the two different fire extinguishing agents, which has certain guiding significance for fire relief in confined space.