Factors Affecting Hot Spot Development in Bulk Coal andAssociated Gas Evolution

摘要

There are many physical factors that can affect the self-heating rate ofrncoal. The presence of seam gas has often been referred to as inhibitingrncoal self-heating due to the limited access of oxidation sites created byrnthe presence of the gas adsorbed on the coal pores. Similarly, thernpresence of bed moisture in the coal also acts as an inhibitor of oxidationrnby blocking access of air into the pores. Gas drainage of a coal seam priorrnto mining removes both gas and moisture from the seam. Bulk coalrnself-heating tests in a two-metre column on both gassy, as-mined andrngas-drained, dried high volatile bituminous coal show that removal of gasrnand moisture from the coal accelerates the rate of self-heating to thermalrnrunaway from 8.5 days to 4.25 days, from a start temperature of 30°C,rnwith an airflow of 0.25 L/min. The corresponding gas evolution patternrnfor each of these situations is different. Therefore, it is necessary to takernthis change in coal condition into consideration when developing arnspontaneous combustion management plan.