ADVANCES IN COAL CHARACTERIZATION BY PROGRAMMED-TEMPERATURE OXIDATION

This paper describes the current status of an analytical procedure for the characterization of coal by programmed-temperature oxidation. Coal is mixed with a diluent to control the reaction and subjected simultaneously to oxidation and a linear increase in temperature up to 1000-degrees-C. The evolved gases (CO2, H2O, SO2 and NO2) are monitored as functions of time and temperature. Distinctive evolution patterns are oberved among coals of different rank and between raw and treated coals. The SO2 evolution peaks obtained from oxidation of coal pyrite and decomposition of sulfate are resolved and appear at temperatures distinct from those observed from combustion of the organic structures in coal. Two major SO2 evolution maxima resulting from organic structures are observed. Each of the organic peaks has CO2 and H2O associated with it, implying that the organic matrix is oxidized in stages. Using model systems for comparison, these two major evolution maxima have been related to the probable structural types producing the evolutions. Analyses obtained with the oxidation procedure compare satisfactorily with ASTM values. Recent improvements in the oxidation conditions and detection system are discussed. The results obtained using the oxidation procedure to analyse model systems and numerous coals, including several treated coals, are discussed.