Calcium sulfate is subjected to gaseous reduction at a high temperature to obtain an SO2 containing gas product and a CaO solid product. The reduction is carried out in a fluidized reaction bed by flowing proportioned air and natural gas into and through the bed to fluidize the finely divided calcium sulfate and to heat to reaction temperatures. The natural gas is only partially burned within the bed, thereby also producing reducing quantities of CO and H2. In a preferred embodiment, the calcium sulfate feed is preheated by direct contact with the gas product to recover part of the heat therefrom, and the gas product of reduced heat content is then subjected to indirect countercurrent heat exchange with the air being supplied to the reaction bed.
Iowa State University Research Foundation, Inc.
Wheelock, Thomas D. and Boyland, David R., "Process for high temperature gaseous reduction of calcium sulfate" (1971). Iowa State University Patents. 320.