Importance

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Abstract

Disclosed is an improved method of concentrating an aqueous solution containing a first salt and a second salt, the solubility of the first salt increasing more greatly with increasing temperatures than the solubility of the second salt, by multiple effect evaporation, wherein the first evaporator effect is the hottest, mother liquor effluent overflow from cooler evaporator effects is forwarded to hotter evaporator effects, mother liquid effluent overflow from the first evaporator effect is forwarded to a zone maintained at atmospheric pressure and mother liquor effluent from the zone maintained at atmospheric pressure is forwarded to a first salt recovery step. In the improved method, the first evaporator effect is operated at super atmospheric pressure and at least 4.degree. C. above the atmospheric boiling point temperature of the mother liquor therein and flashing of mother liquor effluent overflow therefrom is reduced by mixing therewith sufficient mother liquor effluent overflow from a cooler evaporator effect to provide a resultant solution which is reduced more than 2.degree. C. in temperature, preferably to its atmospheric boiling point temperature, and is substantially at its invariant composition at that temperature.

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First Claim