DECOMPOSITION OF CALCIUM SULFATE BY ZONED REDUCTION AND OXIDATION IN A FLUIDIZED BED

摘要

Calcium sulfate is decomposed to CaO and SO2 by high temperature reduction in a fluidized bed, using air as the principal fluidizing gas. A highly reducing gas is formed in the lower portion of the bed from partial combustion of the fuel in admixture with the fluidizing air. The quantity of the primary fluidizing air is limited to 40 to 90% of the stoichiometric O2 quivalent for complete combustion of the fuel to CO2 and H2O. Secondary air is introduced at a higher level in the bed to create an oxidizing zone in the upper portion of the bed above the reducing zone. The concurrent use of such reducing and oxidizing zones permits reducing conditions to be maintained which favor a high rate of decomposition even though these conditions favor the formation of CaS as well as CaO. The undesirable CaS, which would otherwise be discharged with the CaO product is eliminated by circulation of the fluidized particles through the oxidizing zone. Further, the heat of the exothermic oxidation reactions is conserved and utilized for promoting the reduction reactions.