Calcining Gypsum Patents (Class 423/171)
With steam or at specified temperature (Class 423/172)
  • Process for producing .alpha.-type calcium sulfate hemihydrate
    Patent number: 4069300
    Abstract: A process for producing .alpha.-type hemihydrate calcium sulfate by oxidizing calcium sulfite with an oxidizing agent in a suspension containing at least one anionic, nonionic or amphoteric surface active agent.
    Type: Grant
    Filed: September 24, 1975
    Date of Patent: January 17, 1978
    Assignee: Taki Chemical Co., Ltd.
    Inventors: Hakuichi Akazawa, Kenichi Nishimura
  • Gypsum calcination
    Patent number: 3956456
    Abstract: The calcination of gypsum by continuously feeding fine gypsum spirally downwardly through a cylindrical zone into which heated air is injected almost tangentially forming a spiral air conveyor. The calcined gypsum collected at the bottom is of unusual uniformity and can be readily and controllably varied by controlled variations in the characteristics of the heated air conveyor.
    Type: Grant
    Filed: December 17, 1971
    Date of Patent: May 11, 1976
    Assignee: National Gypsum Company
    Inventors: Joseph A. Keller, Robert T. Spitz