The heat of wetting and its effect on coal spontaneous combustion.

• As the temperature increases, the heat of wetting continues to decrease. • The heat of wetting increases as the coal sample size decreases. • The heat of wetting accelerates the occurrence of coal spontaneous combustion. • Coal wetting is exothermic due to the formation of hydrogen bonds. In this study, the effect of the heat of wetting (H w) of coal on its spontaneous combustion was investigated. Specifically, the effects of the amount of water used in the wetting (W), temperature (T), and particle size (PS) on the wettability and exothermic behavior of a coal sample were examined using a C600 high-precision calorimeter. The trends of the Q curves under various conditions (W, T, and PS) were analyzed. The results show that the amount of H w decreased as T increased. The smaller the PS of a coal specimen was, the higher the amount of H w was. Additionally, a decrease in PS led to an increase in the H w release rate (HRR). Due to the generation and accumulation of H w , the oxidative heat storage system of coal is promoted, which accelerates the oxidative spontaneous combustion of coal at low temperature. [ABSTRACT FROM AUTHOR]