Effect of Water-immersion and Air-drying Period on Spontaneous Combustion Characteristics for Long-flame Coal

Abstract

ABSTRACT During the mining of coal seam groups, the physical and chemical properties of the residual coal in goaf will be changed after undergoing water leaching and air-drying, affecting the oxidation characteristics of the coal. To examine the effect of the water immersion and air-drying times on the oxidative combustion characteristics of long-flame coal, this paper uses thermal gravimetric (TG) analysis and infrared spectral analysis to analyze coal samples with different immersion and air-drying times. The change in activation energy (AE), which is associated with the change in the functional groups, was analyzed for the coal-oxygen chain reaction process under coal immersion and air-drying conditions. The results show that coal samples soaked in air-dried for 10 days after water for 20 days have a lower AE (39.14 kJ/mol) than coal samples that underwent other treatment times and have a higher oxygen absorption rate and a higher tendency to undergo spontaneous combustion. According to the TG-DSC test, a range of weight loss and exothermic strengths are observed during the longest immersion and air-drying times. Additionally, during the longest immersion and air-drying times, the variations in the different functional groups are more obvious, the aliphatic hydrocarbon chain breaks and the coal rank is lower. The period of immersion and air-drying can change the spontaneous combustion oxidation characteristics of coal. After being soaked in water for 20 days and air-dried for 10 days, the coal sample was looser and the chain reaction process was accelerated, which promoted the oxidation and spontaneous combustion of coal.