A PROCESS FOR THE CONTINUOUS PREPARATION OF ALPHA-CALCIUM SULPHATE HEMIHYDRATE AND AN APPARATUS

There is described a process for the continuous production of alpha-calcium sulphate hemihydrate, the process comprising the steps of: mixing particulate gypsum, a habit modifier and water to form a gypsum slurry. The process further comprises calcining the gypsum slurry to provide an alpha-calcium sulphate hemihydrate slurry and filtering the alpha-calcium sulphate hemihydrate slurry to separate at least one fluid stream from the slurry, measuring a first control parameter of the at least one fluid stream or the alpha-calcium sulphate hemihydrate slurry; and combining the at least one fluid stream with further gypsum, further water and further habit modifier to form a further gypsum slurry wherein the process further comprises varying the amount of further habit modifier depending on a measured value of the first control parameter. An apparatus for performing the described process is also provided.