Changes in spontaneous combustion characteristics of low-rank coal through pre-oxidation at low temperatures

This study investigated the changes in spontaneous combustion susceptibility of low-rank coal through preoxidation processing at low temperatures. The pre-oxidation processing on low-rank coal was conducted for a certain time at 60-150 A degrees C in normal atmospheric conditions. The oxidation characteristics of coal at low temperature were investigated by measuring the temperature of coal and consumption of O-2 gas during the pre-oxidation processing. Physical properties of coal and changes in crossing-point temperature (CPT) caused by the pre-oxidation processing were also analyzed. Higher the temperature for pre-oxidation, the more consumption of O-2 gas in coal, and larger increase in temperature of the coal was observed. There were no significant changes in the weight of coal samples and calorific value in pre-oxidation processing upto 130 A degrees C. It was found, from Fourier Transform Infrared Spectroscopy (FTIR) analysis, that the coal which underwent pre-oxidation processing upto 80 A degrees C showed no significant difference from raw coal in terms of content. However, higher the temperature for preoxidation, larger decrease in aliphatic hydrocarbon and ether in the coal. As a result of CPT measurement, higher the temperature for pre-oxidation, greater the increase in CTP value of the coal. Therefore, it is expected to reduce the risk of spontaneous combustion susceptibility through the pre-oxidation method. From these results, it was confirmed that the spontaneous combustion susceptibility of the coal can be suppressed without a significant reduction in weight and calories through the preoxidation processing of low-rank coal under the proper conditions.