Recrystallization of rock- or solar salt is a process which renders very high purity salt using comparably little thermal energy. EVATHERM has special knowledge for all related technological systems such as dissolution of rock salt, sedimentation and filtration of sludge as well as chemicals additions.
In opposite to the 2 above described processes the Recrystallization Process requires rock- or solar salt as feed input. Principally cold dissolving and hot dissolving of the solid salt as well is possible, hereunder the hot dissolving process is described
The Recrystallization Process is very similar to the flash evaporation process for seawater desalination respectively to a multiflash evaporation plant. The undersaturated recirculation brine is getting saturated with solid salt at about 108 °C and it will be led downstream into the several flash crystallizers working on different pressures. Due to the pressure drop in each crystallizer water evaporates and subsequently the oversaturation will start the crystallization. The purge from the last crystallizer will be pumped to preheater columns (mixing condensers), where the cold saturated brine will be mixed with the hot vapors coming from the evaporators. Finally the output from the columns is an undersaturated brine on nearly 108 °C which goes into the saturators. Process heat losses are compensated by means of booster heaters built in one crystallizer loop or in the hot recirculation brine pipeline. Especially advantageous is the application of an additional cogeneration unit in form of a diesel generator, where the waste heat can be used for the heat compensation. The following figure is illustrating the process:
The specific advantages of this process are evident:
- very high product purity
- low specific steam consumption
- almost neutral water balance (only a few make-up water needed)
The realized capacities are relative small (max.200’000 MT/year) compared to the largest multieffect- and MVR plants. Normally the number of flash evaporator effects is between 3 and 5, 7 seems to be the maximum.
