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 with increasing temperature than the solubility of the second salt, by multiple effect evaporation, wherein the multiple effect evaporators are backward fed, wherein the first evaporator effect is the hottest, wherein second salt is precipitated during evaporation, wherein the concentrated mother liquor is forwarded to a zone operated at atmospheric pressure, and wherein mother liquor effluent from the zone operated at atmospheric pressure is forwarded to a zone wherein the first salt is recovered. In the improved method the first evaporator effect is operated at super atmospheric pressure, one evaporator effect is operated at atmospheric pressure and at least one evaporator effect is cooler than the evaporator effect operated at atmospheric pressure, one portion of the overflow from the evaporator effect cooler than the evaporator effect operated at atmospheric pressure is fed to the first evaporator effect and the other portion is fed to the evaporator effect operated at atmospheric pressure and the overflow from the first evaporator effect is fed to the evaporator effect operated at atmospheric pressure.

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First Claim