Cyclic process for oxidation of calcium sulfide

Abstract

An improved process for converting particles containing calcium sulfide into calcium oxide by subjecting the particles to repeated cycles of oxidation and reduction. The impenetrable layer of calcium sulfate which forms during the oxidation phase of each cycle is destroyed by the subsequent reducing phase. By repeating the cycle many times, the particles are converted completely into calcium oxide at a reasonable temperature of about 1000.degree. C. The process can be carried out in either fixed bed, moving bed, or fluidized bed reactors by varying the composition of the gas supplied to the reactors in a periodic manner. Alternatively, the process can be conducted in fluidized bed reactors which have separate oxidizing and reducing zones located one above the other. In one design air is supplied through a gas distributor at the bottom of the fluidized bed to create an oxidizing zone in the lower part of the bed. A reducing gas is introduced through a second distribution grid located in the mid-region of the bed to create a reducing zone in the upper part of the bed. In another design, the zones are reversed by introducing a reducing gas through the lower gas distributor and an oxidizing gas through the upper distributor. The upper gas distributor is in the form of an open grid of tubing which does not interfere with particle circulation in the fluidized bed. As the particles circulate freely within the bed, they pass through the different zones many times to be repeatedly oxidized and reduced.