Spontaneous Combustion Characteristics of Wetting Coal under Different Prepyrolysis Temperatures

[Image: see text] The influence of prepyrolysis temperatures on the spontaneous combustion of wetting coal remains unclear from a macroscopic perspective. To this end, a low-ash and high-volatile wetting coal sample from Western China was pretreated by a programmed heating experimental system at isothermal pyrolysis temperatures of 50, 80, 110, 140, and 170 °C under nitrogen atmosphere and then cooled to room temperature; after that, the oxidation heating experiment was carried out within the range of 30–170 °C. The results indicated that, when the wetting coal samples were subjected to isothermal pyrolysis experiments, the concentrations of CO and CO(2) gradually decreased with the prepyrolysis time, during which the cumulative value of CO increased with the prepyrolysis temperatures, while the change trend of CO(2) is first increased, then decreased, and then increased. In terms of the oxidative heating experiment, the CO concentration of prepyrolyzed coal samples was higher than that of raw coal before 70 °C and then gradually lower than that of the raw coal with the increasing temperature. The CO(2) concentration of coal samples with prepyrolysis temperature of 170 °C is significantly lower than that of other coal samples. According to the characteristic parameters of CO and CO(2) concentrations, oxygen consumption rate, and exothermic intensity, it is inferred that the coal sample with a prepyrolysis temperature of 140 °C exhibited the highest spontaneous combustibility. The experimental results have a certain guiding role for the safe mining of coal seam and the prevention and control on spontaneous combustion.