This GEA Messo PT Standard Salt Wash consists of a stirred tank washer/dissolver, a separation station combined with an optional washing-thickener and a centrifuge. The salt wash is countercurrent as follows:
Roller mill in a salt wash factory
The crude salt is first milled (not shown in the sketch above) to a certain particle size distribution necessary for its subsequent processing, and also to destroy inclusions of mother liquor in and remove foreign particles from the salt crystals. Such is the case with Gypsum which can be separated with greater ease from the salt after the size reduction step.
The milled salt is then slurried in an agitated wash tank with wash liquor, which is undersaturated with respect to respect of the soluble impurities (MgCl2, MgSO4 and KCl). These impurities are dissolved by the wash liquor, thus reducing the amount by which they are present on the crystal surfaces.
Read more