Organic and inorganic sulfur in coal

The forms of sulfur in a broad sampling of coals were analyzed, and sources of analytical errors in repeatability, reproducibility, and representativeness were identified. Maceral encapsulation of pyrite can lead to errors in the determination of the organic sulfur content in some coals. If corrected for, this can reduce the amount of sulfur attributed to being organic sulfur. Also, in a few cases, elemental sulfur is present in coal in amounts of the order of a few tenths weight percent. In the Lower Freeport coal, this form accounts for more than 50% of the sulfur recorded as organic sulfur. Generally, crystalline elemental sulfur is found in a range of zero to a few tens of micrograms/gram. Sulfur K/sub ..cap alpha../ x-ray line shifts and intensities are used in the direct determination of organic sulfur in raw and desulfurized coals. Total sulfur, elemental sulfur, pyritic sulfur, sulfatic sulfur and organic sulfur determinations are provided for a wide variety of coals representing different ranks. Leached residues from analytical procedures are examined for residual pyrite. In a few cases, residual pyrite is found and is present in amounts of the order of a few tenths weight percent. Analytical comparisons for elemental sulfur inmore » crushed coal and leached coal residues show no systematic differences in elemental sulfur content. Thus the chemical leaching treatment of HC1 followed by HNO/sub 3/ has no major effect on the elemental sulfur content determined by analyses subsequent to ASTM leaching procedures (for standard sulfatic and pyritic analyses). 6 tables.« less