Crystallizer technology Forced Circulation Crystallizers

FC Crystallizers in the chemical industry

The forced circulation crystallizer (FC) is the most common type of crystallizer in the industry

FC Crystallizers

Oxon NaCl FC

The average FC crystallizer evaporates solvent, thus increasing the supersaturation in the process liquor, and causing crystallization to occur. Most conventional FC units operate under vacuum, or at slight super atmospheric pressure.
The FC consists of four basic components: the crystallizer vessel, which provides most of the volume dictated by the residence time requirements, the circulating pump, which provides the mixing energy, the heat exchanger, which supplies energy to the crystallizer (in a typical evaporative crystallization operation), and the vacuum equipment, which handles the vapors generated in the crystallizer. Slurry from the crystallizer vessel is circulated, in plug flow fashion, through the heat exchanger, and returned to the crystallizer vessel again, where its supersaturation is relieved by deposition of material on the crystals present in the slurry. The supersaturation is controlled so as to avoid spontaneous nucleation, by sufficient circulation capacity.

The evaporated solvent is conducted to the vacuum system, where it is condensed and removed. 


The FC crystallizer is used for general, simple crystallization operations, where large crystal size is not a requirement. The FC design aims to protect the crystal size from reduction from the crystallizer environment, but has no features to aggressively increase the crystal size.


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