Abstract
Rank evaluation of south Brazilian Gondwana coals according to the American (American Society for Testing and Material - ASTM) and German (Deutsche Industrie Normen - DIN) standard specifications or on the basis of Alpern's Universal Classification has too often led to conflicting results. When any attempt is made to determine the rank of Brazilian coals by using methods established for the Northern Hemisphere coals, two sorts of difficulties arise; namely, (1) the reflectance measurements do not indicate the real degree of coalification of the organic matter because of the liptinitic impregnations of the vitrinites, and (2) random reflectance values ( R ran), moisture, volatile matter, and carbon contents as well as the calorific value do not correlate when plotted on the ASTM and DIN classifications schemes. In addition, when rank determinations are carried out by using fluorescence measurements and geochemical analyses, the results are at variance in relation to those determined by the conventional physical and chemical parameters. It is suggested that the rank evaluation of south Brazilian coals is far more meaningful if carried out by reflectance measurements on vitrinites along with fluorescence measurements on sporinites, alginites, and coal extracts.
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