Experimental study on the effect of slow reaction process of the latent period on coal spontaneous combustion

Inhibiting coal–oxygen reactions during the heating of coal is an effective means to prevent spontaneous coal combustion. Therefore, it is necessary to investigate the influence of the latent-period slow reaction on the temperature rise of coal oxidation and the microscopic reaction mechanism. Experiments were conducted to simulate the slow oxidation and pyrolysis reactions of coal in the latent period, and characteristic parameters of the spontaneous combustion after the constant-temperature reaction were analyzed. The results showed that the latent period process promotes the oxidation and heat release of coal and reduce the energy barrier of the coal–oxygen reaction. In situ FTIR and EPR experiments were performed to analyze the changes in the active structure. The results indicated that the self-reaction of active groups during pyrolysis at 50 °C and 60 °C is crucial to the oxidation of coal, providing adsorption sites of free radicals centered on a carbon atom for oxygen adsorption. The Pearson correlation analysis showed that the continuous formation and participation of the hydroxyl structure during the oxidation at 70 °C is an important step affecting the coal–oxygen chain reaction, and it is a key group for making the coal–oxygen reaction inert.