DETERMINATION OF ELEMENTAL SULFUR IN COAL BY SUPERCRITICAL FLUID EXTRACTION AND GAS-CHROMATOGRAPHY WITH ATOMIC EMISSION DETECTION

A rapid and reproducible method to quantify elemental sulphur in coal has been developed using supercritical fluid extraction (s.f.e.) and gas chromatography with atomic emission detection (g.c./a.e.d.). Quantitative spike recoveries of elemental sulphur were obtained from both sand (97 +/- 6%) and pre-extracted coal (96 +/- 3 %). The total amount of elemental sulphur removed was found to be independent of the coal particle size, which indicates that elemental sulphur in coal is located at the surface of the coal particles. North Dakota (Beulah) lignite, Alaska (Beluga) subbituminous coal, and Illinois Basin bituminous coal samples contained elemental sulphur in the range of 2-3500 mug S8 g-1 coal. As much as 35.7% of the 'organic' sulphur in coal (as determined in accordance with ASTM guidelines) is, in fact, elemental sulphur rather than true organic sulphur. In addition, the elemental sulphur values for the coals used in this study correlate well with the inorganic sulphur fractions of coal but not with ASTM-defined 'organic' sulphur.