Crystalizer

1 - Mixed-suspension, mixed product removal (MSMPR) crystallizers. Also sometimes called circulating magna crystallizers, this type of equipment circulates the growing crystals through the zone of the crystallizer where the super saturation conditions are generated. This may be accompanied by mixed- or classified-product removal, and with or without destruction of fines.

2 - Circulating liquor/classified- suspension crystallizers. In this type, only the liquor or a weak slurry is circulated, while the bulk of the growing crystals is not circulated. Super saturation is imparted to the liquor in one part of the equipment, whereupon this liquor is circulated to another area where it relieves the super saturation on growing crystals. This type of crystallizer is also available with or without fines destruction capabilities. The units are usually identified as Krystal- or Oslo-type crystallizers.

3 - Scraped-surface crystallizers. Crystallization is induced by indirect heat exchange with a cooling medium at the heat-transfer surface, which is continuously scraped and agitated to minimize fouling. This type of equipment employs vertical tanks with scrapers or horizontal pipes.

4 - Tank crystallizers. Crystallization is produced by cooling the feed solution in either static or agitated tanks by natural convection and radiation, by surface cooling through coils or a jacket, programmed evaporative cooling, reaction, or anti-solvent methods.