Ppg Industries Canada Ltd.

Donald H Geesen

Disclosed is a method of increasing and maintaining high concentrations of potassium chloride in a refinery process stream of brine containing potassium chloride, sodium chloride and a minor amount of salt impurities by mixing with a first process stream potassium chloride crystallized from a pond wherein a brine from a second process stream is concentrated by solar evaporation and/or cooled by low ambient air temperatures.

Production of potassium chloride using pond crystallization

Disclosed is an improved method of producing potassium chloride by concentrating a brine thereof with respect to potassium chloride by multiple stage evaporation conducted at progressively higher temperatures, thereby precipitating other salts and thereafter cooling the brine in multiple stage crystallizers operated at progressively lower temperatures, thereby precipitating potassium chloride crystals. The improvement comprises cooling the brine in hotter crystallizer utilizing streams to or between cooler evaporators whereby in addition heat is provided to the evaporator stream.

Process of treating potassium chloride brine by evaporation and

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.

Method of concentrating an aqueous solution by multiple effect

Disclosed is an improved method of recovering a salt having a solubility which increases with increasing temperatures from a multiple salt aqueous solution also containing a salt having a solubility which increases less with increasing temperatures than the solubility of the salt to be recovered. The solution is subjected to multiple effect evaporation having a plurality of evaporator effects operating at progressively higher temperatures. In the improved method, a means is provided whereby the mother liquor effluent overflow from the hottest evaporator effect is saturated with the salt to be recovered. Additionally, solution being concentrated in other effects having at least one preceding cooler evaporator effect may be allowed to become saturated with respect to the salt to be recovered. A slurry of the salt having a solubility increasing less with temperature is withdrawn from all effects. This slurry is recycled from effects operated at saturation with respect to the salt to be produced and fed to at least one cooler effect. The solution in at least one cooler effect is concentrated to less than saturation with respect to the salt to be recovered. Thus, the solids of the slurry withdrawn from the cooler effect is not introduced back into the evaporation system thereby purging in a heat efficient manner the salt having a solubility increasing less with temperature.

Method for operating multiple effect evaporators

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.

Method of concentrating salt solutions

Disclosed is an improved method of separating a first salt and a second salt from an aqueous solution containing both salts and salt impurities, where the solubility of the first salt increases more with increasing temperatures than the solubility of the second salt, and at least a portion of the salt impurities precipitates as slower settling rate crystals than the settling rate of precipitated second salt. The solution is passed through a series of evaporators in which second salt and salt impurities are precipitated. The bottom of each evaporator communicates with an elutriation leg into which precipitated salts settle, and into which a fluidizing liquid is introduced to carry precipitated salt impurities back to the evaporators and from which second salt slurry is withdrawn. In the improved method, evaporator mother liquor effluent overflow having a temperature and salt composition near the temperature and salt composition of the solution in the evaporator communicating with the elutriation leg into which the fluidizing liquid is introduced is utilized as a fluidizing liquid (elutriant) in the potassium chloride recovery step.

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Wilcox, Canada

Donald H Geesen