In this type of crystallizer the crystallization is effected by cooling a solution or melt by the adiabatic evaporation of the solvent by pressure decrease. Hence no surfaces to serve the heat exchange are needed which are susceptible to incrustation in case of the use of salt-deposing solutions. Hereby the performance of the plant decreases. Consequently the demand for an operation with large cleaning intervals is met.
Vacuum crystallization plants may be designed single-stage and multi-stage.
Due to energy costs coolking an be achieved by:
- application of steam ejectors
- application of refrigerating agents (refrigerating machines)
- use of sulfuric acid of soda lye as condensation agent
Specific fields of application:
Salts with adherent water molecules such as:
- CuSO4x 5H2O
- FeSO4 x 7H2O
- Na2SO4 x 10H2O
- MgSO4 x 7H2O