Patent ID: 7951352

Claim:
A process for the production of alpha-calcium sulfate hemihydrate from calcium dihydrate, said process comprising the following features: a) an agitated autoclave ( 1 ) is charged with calcium sulfate dihydrate, b) the agitated autoclave ( 1 ) is heated indirectly, c) water is added and mixed in in a controlled manner, d) material is prevented from adhering to surfaces of the reaction chamber by moving chains ( 3 ) fitted to the paddles and/or the drive shaft ( 16 ) of the agitated autoclave ( 1 ), e) the pressure in the reaction chamber is regulated at intervals or continuously by discharging steam when a specific pressure has been reached in the interior, the steam being guided via a cyclone separator ( 17 ) and an actuating valve ( 18 ), f) cold air is fed in for residual drying, and g) the process material is removed.