The cooling crystallization can be applied when the solubility gradient of the solution increases steeply with falling temperature or when a vaporisation of the solvent has to be avoided.

Depending on the specific task a vacuum cooling or a surface cooling process, which is an atmospheric process, can be applied. At the vacuum cooling crystallization the supersaturation of the solution is caused trough the evaporation of the solvent and through the cooling of the mother liquor as well. The crystallizers are designed as flash units very similar to the evaporators used in the recrystallization process. The vacuum is generated by means of high performance ejectors with condensing system. On the other hand, at the surface cooling crystallization the supersaturation is only a result of the temperature decrease of the liquid. EVATHERM’s surface cooling crystallizers are characterized by proper supersaturation control and limited scaling tendency, even at very low temperature. Installations with operating temperatures of
-10 °C to -20 °C have already been realized successfully. A combination of both technologies shows the figure above. A sophisticated Cooling Energy Recovery makes this process as a valuable and feasible alternative to other processes.

Possible applications can be: