Crystalliser forced-circulation

In forced circulation evaporators the liquid is pumped through the tubes. They are suitable for use with materials which tend to foul the heat transfer surfaces, and where crystallisation can occur in the evaporator. 

The majority of continuously operated crystallisers are of three basic types forced-circulation, fluidised-bed and draft-tube agitated units. 

On the left hand side, it is shown a sketch of a (forced circulated) FC-type crystalliser, a crystalliser with external circulation loop. On the right hand side, one can find a simplified solubility system in which the metastable limit is marked with a dashed line. What happens within one circulation loop is indicated by numbers in the solubility diagram as well as in the FC-crystalliser sketch. 

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