Microchemistry of Illinois coals - impact for sulfur removal. Final report, 1 July 1983-30 June 1984

Abstract

The distribution of elements (C, N, O, S, Na, Mg, Al, Si, Ca, and Fe) has been determined by point-to-point microanalysis of several maceral components of three samples of Illinois coal. The point-to-point variations for C, Si, Fe, and pyritic S were much greater in the exinites than in the vitrinites. The carbon content of exinites ranged from 40 to 70 weight percent and averaged 52 to 57%. The carbon content of vitrinites was higher, averaging 68 to 82%. The organic sulfur content of vitrinites was nearly the same as that of exinites, but the pyritic sulfur was much higher in the exinites. Both iron and silicon were higher in exinites than in vitrinites. In vitrinites, silicon ranged from 0.01 to 0.30% while iron was generally less than 0.1%. Nitrogen, sodium, and magnesium contents of these coals were near the limit of detectability, and no significant variations were noted. The organic sulfur content of the No. 5 coal and one of the No. 6 coals was in the range of 0.2 to 0.6%, while the other No. 6 coal had organic sulfur above 1% and total sulfur of 3.84%. The organic sulfur was easily distinguished from the pyritic or sulphatic sulfur forms by the local iron content and the variation in the sample current. The solvent-reacted samples showed only small changes in average composition. The differential thermal analysis curves for all three of the coals are remarkably alike, from room temperature to 850/sup 0/C. The microanalyzed residues showed large reductions of organic sulfur content but only small changes in carbon content after heating. Coal samples heated in a microwave oven to 200/sup 0/C for up to thirty minutes did not show significant changes in composition. 6 references, 4 figures, 5 tables.