Forced circulation crystallizerare the classical devices to crystallize salts.
As the name implies, the liquor in a forced-circulation evaporator is pumped through the tubes to minimize tube scaling or salting when precipitates are formed during evaporation.
Slurry is pumped from the bottom cone of the vapour body through the tubes of the heat exchanger, where heat is added, and back into the vapour body where evaporation occurs. Sufficient liquor height is maintained above the heat exchanger to suppress boiling in the inlet and prevent surface boiling on the tube surface. A high circulation rate is provided for adequate tube velocity to achieve good heat transfer. A sufficient quantity of salt crystals is suspended in the circulating system to provide seed crystals in the boiling zone for salt growth. Adherence to these basic principles of crystallization results in coarse crystals and minimal wall and tube scaling.