Drying process of concentrated mother liquor from high salt wastewater

High salt wastewater refers to wastewater with a total dissolved solids greater than 3.5% and a mass fraction of at least 1% expressed as sodium chloride, containing inorganic salts such as chloride ions, sodium ions, and sulfate ions. It mainly comes from the zero discharge, salt precipitation, distillation, and membrane separation sections of fine chemical industries such as pharmaceuticals, pesticides, and coal chemicals. Its composition is complex, the water quality is variable, and the treatment difficulty is high.

At present, most domestic enterprises use mechanical vapor recompression technology (MVR) and multi effect evaporation to concentrate and reduce waste liquid. However, high salt wastewater contains a large amount of high boiling point organic matter, which cannot evaporate with water vapor during the evaporation and concentration process, nor can it enter the solid salt crystallized after concentration. Therefore, these organic compounds remain in the crystallization mother liquor, and impurity ions gradually increase during the mother liquor enrichment process, resulting in a decrease in the quality of the obtained salt. Therefore, it is necessary to periodically discharge the mother liquor to reduce the interference of impurity ions on the quality of the salt.