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

Abstract

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 °C in normal atmospheric conditions. The oxidation characteristics of coal at low temperature were investigated by measuring the temperature of coal and consumption of O2 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 O2 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 °C. It was found, from Fourier Transform Infrared Spectroscopy (FTIR) analysis, that the coal which underwent pre-oxidation processing upto 80 °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.