Process for the spontaneous precipitation of sulfates dissolved in water as calcium aluminium sulfate and the application of this process for the preparation of low-chloride gypsum-anhydrite containing aluminium oxide

摘要

The invention relates to a process for the spontaneous chemical precipitation of sulphates dissolved in water as calcium aluminium sulphate, using a hydrated lime (calcium hydroxide) suspension and a sodium hydroxoaluminate solution as precipitants, and the application of this process for preparing calcium aluminium sulphates which can be processed on an industrial scale into low-chloride anhydrous gypsum (anhydrite) containing alumium oxide using a thermal process known per se.