Fuel Processing Technology, 35 (1993) 233-257 233 Elsevier Science Publishers B.V., Amsterdam Investigation of sulfur forms extracted from coal by perchloroethylene Frank E. Huggins*, Shreeniwas V. Vaidya, Naresh Shah and Gerald P. Huffman Institute for Mining and Minerals Research, 233 Mining and Mineral Resources Building, University of Kentucky, Lexington, KY 40506-0107 (USA) (Received November 25, 1992; accepted in revised form March 2, 1993) Abstract The forms of sulfur present in a number of coals before and after extraction with perchloroethy- lene (PCE) at its boiling point (121 ° C) for up to an hour have been examined by a combination of sulfur XAFS and MSssbauer spectroscopies and standard chemical methods. A hybrid forms- of-sulfur analysis was devised that included determinations of pyritic sulfur, elemental sulfur, organic sulfide, thiophene, oxidized organic sulfur forms, and sulfate. Of these forms of sulfur, only elemental sulfur was shown to be significantly extracted by PCE in the coals examined. Except for complications involving pyrite segregation during the extraction process in certain experiments, changes in all other sulfur forms with respect to the extraction were less than experimental uncertainties in the hybrid forms-of-sulfur analyses. MSssbauer and CCSEM data shewed that pyrite and all other minerals in the examined coals are not significantly affected by the PCE extraction. I. INTRODUCTION The specific gravity of the chlorinated hydrocarbon, perchloroethylene (PCE, C2C14), is 1.62, which is close to an optimum value for conventional float/sink cleaning of most coals. Consequently, PCE has been proposed as a heavy liquid medium for separating coal maceral and mineral components by flotation into a clean, ash-poor fraction and an ash-rich waste fraction. In addition, PCE and other chlorinated hydrocarbon solvents will readily dis- solve many simple organic sulfur compounds, including sulfides and thiophenes, which are believed to be the major organic sulfur functional forms present in coals of bituminous rank. Hence, such solvents appear to have the potential for removing both inorganic sulfur and organic sulfur forms from coal by float/sink and chemical extraction processes, respectively. Both of these processes are included in a PCE-based pilot-scale coal cleaning facility built by Midwest Ore Processing Company, Inc., and are present in a design for a PCE-based demonstration-scale coal-cleaning plant, proposed by the same * To whom correspondence to be addressed. 0378-3820/93/$06.00 © 1993 Elsevier Science Publishers B.V.