SULFUR CHARACTERIZATION OF POLISH COALS, THEIR LITHOTYPES AND MACERALS

Three coals of different rank (R(0) = 0.58-1.01%), and the lithotypes and macerals separated from these coals, were analysed in this study. The wet chemical technique was used to determine the distribution of sulfate, pyritic and organic sulfur forms in the coals and lithotypes. The morphology, size and mode of occurrence of pyrite were examined by optical microscopy and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis. An oxidative technique was developed to study the organically bound sulfur in the maceral microsamples. Pyritic and organic sulfur accounted for nearly all the sulfur in the coals examined and their lithotypes. In comparison with the coals, the lithotypes had a higher proportion of very fine pyrite. Pyrite was most abundant in fusain. The organic sulfur content in the lithotypes decreased in the order: clarain > vitrain > durain > fusain. An analysis of the SO2 evolution profile from temperature programmed oxidation (TPO) of the maceral concentrates indicated that exinite showed the most distinct changes in the chemical structure of sulfur compounds with coal rank. Based on the TPO study a new parameter describing the reactivity of organic sulfur of macerals is proposed.