Comparative Experimental Analysis on Coal Spontaneous Combustion

Abstract

The goal of this study was to investigate coal quality features and their relationship to coal spontaneous combustion characteristics in multi-seam coal mines to better predict when coal spontaneous combustion is likely to occur. To that end, coal samples of various particle sizes were obtained from five coal seams (Nos. 6, 8, 9, 12 and 20) in the Shuangyashan City Xin’an Coal Mine. The samples were then respectively heated using a temperature programming system to observe and compare similarities and differences in the spontaneous combustion process of different particle sizes in response to rising temperature. The experimental results show, that in all five coal seams, the concentration of CO, C2H4, and C2H6 increased with a certain degree of regularity as a function of rising temperature. However, of these three gasses, only CO and C2H4 can be used as indicators to predict coal mine spontaneous combustion. The critical temperature for samples from all five coal seams ranged from 50–85°C, while the dry cracking temperature of coal seams 8 and 12 (80–100°C) were lower than those of 6, 9, and 20 (100–120°C). Furthermore, the production rate of CO, C2H4, and C2H6 is related to both coal particle size and temperature. The smaller the particle size, the faster the production rate; and the higher the temperature, the more gas that gets produced. All five coal seems are mainly composed of long flame coal. However, they differ in that the No. 12 coal seam contains weak cohesive coal; the No. 8 coal seam contains lean and gas coal; and the Nos. 6, 9, and 20 coal seams contain a certain amount of anthracite. During the programmed coal heating, the CO, C2H4, and C2H6 release trend for the coal seams was No. 12 > No. 8 > Nos. 6, 9, and 20. These results demonstrate that the presence of weak cohesive coal and anthracite highly influence the concentration of CO, C2H4, and C2H6 released during coal spontaneous combustion.