THE DISTRIBUTION OF TRACE ELEMENTS IN MINERALS FOUND IN COAL

The determination of minor and trace elements in coal and coal products utilizing size and density separates of low-temperature ash is described. The size distributions of the major minerals were determined and correlations of trace elements with major minerals were made. The role of minor minerals in the modes of occurrence of trace elements is also discussed. Neutron activation and inductively coupled plasma analyses were used to determine elemental concentrations. X-ray diffraction and scanning electron microscopy were used for mineral identification.; This procedure was applied to a mineral-rich solvent refined coal product (Vacuum Bottoms) and its feed coal (Powhatan #6 coal) to obtain information on transformations of minerals and mobilization of trace elements in coal liquefaction procedures. The major mineralogical change in this process is the transformation of pyrite to pyrrhotite. This transformation significantly alters the size distribution of the Fe species of the product. Other changes and the mobilization of trace elements are confined to a few volatile elements--As, Se, Sb and Hg--which are associated with pyrite in the feed coal. The trace element associations with the silicates and phosphates are similar to those of the feed coal.; This procedure was applied to bench channel samples of the Upper Freeport coal bed from three different facies of the coal representing significantly different mineral assemblages and geochemical environments of formation. The results show As, Hg and Se generally associated with pyrite; Rb, K, Al, Cs, Na associated with clay minerals; Ca and Mn associated with calcite (also Zn in one of the facies); and Ti, Hf, Ta, Th, U, La and the rare earth elements associated with heavy accessory minerals especially in the smaller size fractions. Because many of these relationships are found in the Powhatan #6 coal as well they may reflect geochemical conditions required for the formation of bituminous coals.; Excellent reproducibility of data and mass balances near 100% account for the distribution of trace elements throughout the separation procedure.