Experimental study on the displacement effect and inerting differences of inert gas in loose broken coal

The pre-injection of inert gas before coal self-ignition is a common key measure for preventing and controlling spontaneous coal combustion in a goaf. Previous studies have mainly considered inerting to reduce the concentration of ambient gas components and explored the influence of oxygen or inert gas concentration on the inerting effect of loosely broken coal, but seldom considered the replacement of oxygen by an inert gas, especially the replacement of adsorbed oxygen. Here, we quantitatively investigated the difference in room-temperature inerting of loosely broken coal by N2 and CO2 by conducting one-factor experiments on replacing oxygen in coal with an inert gas at room temperature and pressure. The results reveal that the replacement process can be divided into three stages and that the different adsorption capacities of coal for N2 and CO2 are the main reasons for the asynchrony of each replacement stage. The stronger the adsorption capacity, the stronger the displacement of adsorbed oxygen in the adsorbed state by the inert gas. CO2 exhibits an inerting strength 2.3–2.6 times higher than N2 and 5.7–8.8 times higher than He. The experiments also revealed that optimizing the key parameters of inert fire protection technology should consider the adsorption effect.