Abstract: A method of extracting a substantial proportion of the pyritic, organic, and sulfate sulfur compounds and ash present in a solid carbonaceous fuel of the coal or coke type comprising mixing the fuel with an aqueous alkaline solution containing a sodium, calcium, or ammonium carbonate, hydroxide, sulfide, or hydrosulfide, or a plurality thereof, heating the resulting mixture to at least about 125.degree. C at a pressure of at least about 25 psig to leach out the sulfur compounds and ash, separating the easily removable leached out materials from the remainder of the fuel, and washing said remainder of the fuel. The concentration of alkali in the solution typically is about 1 to 35 percent by weight, and the mixture typically is heated for at least about 5 minutes at about 350.degree. C, about 1 hour at 300.degree. C, about 2 hours at 250.degree. C, about 4 hours at 200.degree. C, about 10 hours at about 125.degree.