Oxydesulfurization of Coal by Acidic Iron Sulfate Solutions

摘要

To facilitate by-product recovery and eliminate elemental sulfur formation in coal oxydesulfurization, high-sulfur bituminous coal has been treated with aqueous ferric sulfate/sulfuric acid and oxygen at 100 to 150 exp 0 C. The rate of pyrite oxidation increases with oxygen partial pressure, temperature, and fineness of grinding. This reaction rate is relatively insensitive to sulfuric acid and ferric sulfate concentrations, so that pyrite removal may be satisfactorily performed in solutions containing 25% H sub 2 SO sub 4 and 12% Fe sub 2 (SO sub 4 ) sub 3 (weight percentages relative to total H sub 2 O plus H sub 2 SO sub 4 ); preliminary data suggest that such a leaching solution is only mildly corrosive to T316 stainless steel, at 150 exp 0 C or below, in the presence of oxygen. To provide an accurate assessment of coal oxydesulfurization stoichiometry, an analytical technique based on uv spectrophotometry has been developed for the determination of elemental sulfur in coal. Prepared coal samples are extracted for 24 hours with cyclohexane. Other exploratory oxydesulfurization runs have shown that vanadium oxides are not effective catalysts at 100 exp 0 C, with oxygen. Nor are lauryl sulfate or sulfates of zinc, copper, or manganese effective additives in the ferric sulfate/sulfuric acid/oxygen system at 150 exp 0 C. Elemental chlorine has been shown to be capable of removing significant amounts of organic sulfur from coal, at 74 exp 0 C, but suffers the drawback of chlorinating the coal's orgaic matrix. Hydrogen peroxide in aqueous sulfuric acid is an effective reagent for pyrite removal at 100 exp 0 C, but is unduly expensive. (ERA citation 06:034215)