Gypsum, in cooling water systems

Thermal Reduction of Gypsum. The initial work involving the thermochemical technique was carried out in Germany and more recently by the U.S. Bureau of Mines (USBM), which did research work on two processes for the recovery of elemental sulfur from gypsum at the Salt Lake City Metallurgy Research Center in the late 1960s (30). Both processes involved reduction roasting of gypsum using coal or reducing gases at 900—950°C to produce calcium sulfide. Process one involved carbonation of a water slurry of calcium sulfide with C02-bearing flue gases from the reduction kiln to precipitate calcium carbonate and to evolve hydrogen sulfide. The latter could be converted to sulfur in a standard Claus unit. Process two made use of a countercurrent ion-exchange system and sodium chloride to produce by-product sodium carbonate and calcium chloride as well as elemental sulfur. Three metric tons each of the by-product were produced per metric ton of sulfur.  [c.120]

The Nalco Guide to Cooling Water System Failure Analysis (1993) -- [ c.73 , c.75 ]