Study on the thermal reaction characteristics and kinetics of coal and coal gangue coexisting spontaneous combustion

In the hope of exploring the effect of coal gangue left in goaf on coal spontaneous combustion, the variations of thermal effects and free radical parameters during coexisting spontaneous combustion of coal and coal gangue were tested, and kinetic at different heating stages were calculated. The following beneficial findings were obtained. For the mixed samples, the heat flow curve, ignition temperature, and free radical concentration all decline with the increase of coal gangue content, and the free radical parameters exhibit periodic changes with increasing temperature. Both the experimental value of thermal effect and free radical concentration with coal and coal gangue mixture during the spontaneous combustion process are higher than the calculated value. The calculation results of kinetic show that at the endothermic stage, the activation energies of the mixed samples decline with the increase of coal gangue, and the experimental value of activation energy is greater than the calculate value; at the exothermic stage, the case is exactly the opposite. Furthermore, due to the higher reactivity of coal gangue groups and stronger thermal conductivity, the coexistence of coal and coal gangue spontaneous combustion reaction is promoted. Resultantly, coal spontaneous combustion is normally more threatening in gangue-containing goafs.