The U.S. Bureau of Mines mine fire diagnostic methodology to locate and monitor fires in abandoned mines and waste banks is based on controlled sampling of the mine atmosphere to determine changes in the concentration of hydrocarbons desorbed from heated coal. To provide background data for this methodology, a laboratory study was conducted in which samples of coal and coal waste were heated under controlled conditions. Gas samples from the combustion furnace were analyzed for standard gases co2 and CO and for the c1 to c5 hydrocarbons. In all tests, the concentration of desorbed hydrocarbons increased during heating and decreased during cooling. A dimensionless hydrocarbon ratio, r1, was developed as the signature for heated coal. For bituminous coals, the value of r1 increases during heating of coal samples and decreases during cooling of the same samples. Generally, r1 values of 100 or more indicate coal sample temperatures of at least 100 deg c. The emission of higher molecular weight hydrocarbons from anthracite samples was very low, resulting in relatively low r1 values at all temperatues. Data from field projects confirmed these results.
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