Experimental investigation on spontaneous combustion of coal affected by exothermic reaction of polyurethane in underground coal mines

Organic elastomers such as polyurethane are widely used as a filling material in underground coal mines. However, the risk of fire hazard in coal seams is increased due to the flammability of polyurethane. Laboratory tests illustrate that in a thermostatic reactor with initial temperature of 25 °C, the temperature during the production of polyurethane increases up to > 140 °C. Adiabatic oxidation experiments and TG–DTG analysis showed that the heating rate of the mixed samples of polyurethane and coal was higher than that of any single component in the initial oxidation stage. From the initial temperature to 100 °C, increasing the proportion of polyurethane was conducive to the acceleration of temperature rise. From 0.180 to 0.850 mm, the self-heating rate was inversely proportional to the particle size. At the initial stage, the low ventilation rate promoted the spontaneous combustion of mixed samples, but when the temperature is > 70 °C, an opposite trend was seen. Kinetic parameters suggested that the activation energy decreases with the introduction of polyurethane. According to the mathematical model, the variation of the spontaneous combustion period of coal and polyurethane was predicted.