Fires in abandoned coal mines and waste banks present serious safety and environmental hazards. Often, spontaneous combustion is assumed to be the source of these fires, although some coals have an apparently low susceptibility to self-heating. It has also been noted that in abandoned mines evidence of heating is found in the roof coal and shale. Spontaneous ignition is also a factor in coal waste bank fires. Although the spontaneous combustion of coal has been studied extensively, there is very little information about the self-heating tendency of roof coals and carbonaceous shales. This U.S. Bureau of Mines study of self-heating tendencies utilized a modified version of a differential thermal analyzer. In this study, a combustion furnace served as the reference temperature against which the sample temperature was measured. A crossing-point temperature index was used to relate self-heating tendencies of various samples. Analysis of the effluent gas for co2, CO, o2 depletion, and desorbed hydrocarbons was also used to evaluate the degree of self-heating and the heat-generating process. Ten samples, including Pittsburgh coal, roof slate, carbonaceous shales, and western coals, were tested. The crossing point index was compared to known self-heating behavior, reaction rates, btu values, and compositional differences.
Proc. 1990 Mining & Reclamation Conf. & Exhibition. West Virginia Univ. Pub. Svc, V. 2, 1990, PP. 535-542