| abstract |
Finely divided coal or coal derivatives, containing pyrite, are reacted with sulfurous acid (the oxidizing agent); if desired, HCl may also be used to improve the reaction efficiency to remove pyritic sulfur from coal as shown by the following equations: Primary: Oxidation - reduction 4 FeS2 (pyrite) +3SO2 + 12 HCl -> 4 FeCl3 + 11S + 6 H2O Secondary: Oxidation - reduction 4 FeCl3 + FeS2 (Pyrite) -> 6 FeCl2 + 4S Overall reaction 6 FeS2 + 3SO2 + 12 HCl -> 6 FeCl2 + 15S + 6 H2O The solution containing ferrous chloride and unreacted sulfurous acid is then filtered from the coal which is then washed and heat dried under low pressure. Most of the free sulfur is volatized from the coal due to the heat drying; additional free sulfur can be removed by additional washing and heat drying and/or solvent extraction techniques. If desired, the ferrous chloride can be oxidized to ferric oxide and hydrochloric acid. The hydrochloric acid may be recycled and the iron oxide used for production of steel or discarded. |