At crystallization a number of salts which precipitate contain crystal water, i.e. water molecules are included in their crystal system. These molecules have to be removed in order to allow a further utilization of the salt.
A typical example is glauber’s salt (Na2SO4 x 10H2O). Under normal pressure it melts already at low temperature in its own crystal water.
This led to the idea of developing the melting crystallization (also called calcining). In this case the glauber’s salt is fed into a melting tank and is dissolved in its own crystal water. By doing this a part of the anhydrous crystals precipitate. The water is evaporated in evaporation crystallizers which are equipped with exterior heaters. These crystallizers may be designed single-stage of multi-stage, with vapour compression or without (mechanical or thermal).
In addition to the conventional single-stage or multi-stage plants EBNER developed another type of plant to meet the economic requirements. This plant works in overpressure. By this development Ebner succeeded in minimizing the problem of incrustation in the heater tubes.