Comparative Elemental Associations in Lignites Having Significant within-Mine Variability of Sodium Content

摘要

The inorganic constituents of lignites from the Fort Union Region are distributed within the coal matrix as cations, coordinated species and minerals. The quantities of inorganics present in these lignites have significant within-mine, or intramine, variability. Studies have indicated that high-sodium coals from this region cause severe ash fouling of heat exchange surfaces in utility boilers. From each of two mines, two samples were selected having significant differences in sodium content and different fouling characteristics in utility boilers. The distribution of inorganics constituents within the Gascoyne and Beulah coals was determined by non-quantitative identification of mineral matter and by chemical fractionation to ascertain any significant differences in the association of elements within the coals. In addition, the amounts of ion exchangeable cations related to the carboxylate content of the coals were determined. A comparison of the elemental associations between the high-sodium coals and their intramine low-sodium counterparts shows: No significant differences in the modes of occurrence of the inorganic constituents exist, only differences in the amounts of inorganic species; a higher percentage of aluminum is extracted from the high-sodium coals indicating different types of predominant micaceous clay minerals; and a higher percentage of barium is associated with ion exchange sites in the high-sodium coals. 12 references, 1 figure, 4 tables. (ERA citation 09:035071)