Desulfurization and conversion of coal under supercritical conditions

The supercritical desulfurization process is based on the observation that, in the presence of alcohol under temperature and pressure conditions above the critical point of the alcohol being used for the extraction/reaction process, organic sulfur is selectively removed from the coal matrix. Over 50% reduction in total sulfur concentration was attained in batch reactor experiments when a high organic sulfur content coal (organic sulfur comprising 73% of the total sulfur) was processed using pretreatment with a potassium hydroxide solution, followed by a supercritical extraction with methyl alcohol. A continuous reactor process development unit has been constructed at the Coal Technology Laboratory and preliminary test results and unit design are discussed. The combination of a physical coal cleaning process for removal of pyritic sulfur, followed by supercritical extraction with alcohol to reduce organic sulfur, would combine the advantages of both processes.