Investigation into spontaneous combustion characteristics of some Indian coals and correlation study with their intrinsic properties

Abstract

Mine fires and spontaneous combustion are prime issues in the coal mining industry and have led to huge coal losses and mine disasters. The property of self-oxidation of coal makes it highly vulnerable to degradation after being exposed to favorable conditions of spontaneous heating. For safe storage and use of coal, it is very important to know about its liability to spontaneous heating. It is known that, spontaneous heating is dependent upon intrinsic and extrinsic parameters. In the present work, the spontaneous combustion susceptibility of a number of coal samples belonging to different coalfields have been studies and its correlation with different intrinsic properties have been carried out. In order to carry out the above study, 23 coal samples were collected from different Indian coalfields.Coal samples were collected from Singareni Collieries Company Ltd. (SCCL), Northern Coalfields Ltd.(NCL), Mahanadi Coalfields Ltd. (MCL), South Eastern Coal Fields Ltd. (SECL) and Eastern Coal Fields Ltd. (ECL).. The experiments carried out to determine the intrinsic properties and susceptibility indices wereProximate analysis, Bomb calorimetry, Crossing point temperature, Differential thermal analysis and Wet oxidation potential.From correlation analysis, it was found that average slopes of stage IIA and IIB obtained from DTA thermograms indicated a fairly accurate measure of spontaneous heating susceptibility as they showed high correlation with the intrinsic properties. Moisture and volatile matter content may also be helpful in assessment of liability of coal to spontaneous heating as they showed better correlation than other intrinsic properties viz., ash content and gross calorific values. Differential thermal analysis was found to give better correlation and so may be accepted as a better method for assessment of spontaneous heating susceptibility of coal than crossing point temperature and wet oxidation potential analysis. It is expected that the finding of this work will help the field engineers to accurately assess the spontaneous heating susceptibility of coal seams in their mines and plan the production activities accordingly.