Low-Sulfur Coal Obtained by Chemical Desulfurization Followed by Liquefaction

Abstract

Coal combustion is the largest single source of sulfur oxide air pollution. Two major technologies for the desulfurization of coal prior to combustion, coal liquefaction and the Meyers Process, have been experimentally evaluated. While each process is individually capable of reducing a portion of U.S. coal reserves to an environmentally acceptable sulfur content, neither can meet all U.S. needs. An advantageous combination of the two processes is described which could eliminate a major technical hurdle in the application of liquefaction technology and thus expand the portion of U.S. coal which can be converted to an acceptably low-sulfur fuel. Information regarding the fate of sulfur forms during liquefaction is also presented.The sulfur content of coal, nearly all of which is emitted as sulfur oxide during combustion, is, on the average, about equally distributed between two chemical forms, inorganic (iron pyrites) and organic sulfur.An unconventional approach for near total removal of the pyritic sulfur content of coal has been reported by Meyers et al. (J 972). This new technique involves treatment of coal with a regenerable aqueous ferric solution, as outlined in the following equations (Hamersma et aI., 1973):

Technology for Chemical−Metallurgical Coal Ash Utilization

“…The Meyers process is based on treating coal with reclaimable aqueous ferric solution followed by the separation of sulfur and Fe 2 (SO 4 ) 3 . − The process applies primarily to coals rich in pyrite sulfur rather than to coals with mainly organic sulfur.…”