STUDY ON THE SALTS CRYSTALLIZATION BEHAVIOURS DURING BITTERN BOILING EVAPORATION AT 70°C

摘要

Normally the production process to deal with the bittern includes three steps: KCl production with 2-effect vacuum evaporation of the mixture of bittern and mother liquor after KCl production; Br2 extraction through distillation process, and MgCl2·6H2O production by mono-effect evaporation. For the production of KCl, Most of the salt industry plants will mix the bittern and mother liquor after its production in the first evaporator, and separate the NaCl and MgSO4 solids from the mother liquor in the second evaporator. In the second evaporator, the operation temperature is 65～70°C, but the concentration is controlled by operation experience only, that may lead to the NaCl and MgSO4 solids can not be separated from the liquor completely, then the output is low, meanwhile big quantity of mother liquor is mixed in the solid, so the throughout of KCl product wiill be low also, and the further separation of the NaCl and MgSO4 solids will be not easy. Based on the analysis of Na+、K+、Mg2+//SO42- Cl--H2O phase diagram and the experimentation of the bittern evaporation in the laboratory, this paper studies the salt crystallization behaviours of the bittern evaporation under 70°C, which will supply reliable data for operation of the second evaporator in the production of KCl product.