Process for enriching crude salt, in which the crude salt is ground and then cooled in a saturated aqueous sodium chloride solution, to a temperature below the anhydrous sodium chloride to sodium chloride dihydrate transition temperature, a stock of a powder comprising sodium chloride crystals is collected from the cooling step and the powder is subjected to particle-size fractionation from which a fine particle-size fraction and a coarse particle-size fraction comprising the enriched salt are collected.

A cooling technique whereby a hot, concentrated, diaphragm cell sodium hydroxide solution coming from an evaporator is cooled and sodium chloride removed therefrom. The sodium hydroxide solution is contacted with a liquid refrigerant to cool the solution and precipitate the salt. The salt is separated from the cooled solution. The liquid refrigerant can be recovered and recycled. Such method avoids the use of conventional tube heat exchangers which are periodically plugged by the salt precipitate. Also, the direct contact cooling method provides conditions for salt crystal growth thus making subsequent separation easier to accomplish.

A process for recovering silver present in cuprous chloride solutions as a soluble silver chloride which comprises saturating the cuprous chloride solution with sodium chloride, subjecting the saturated solution to evaporation to co-crystallize the sodium chloride and silver chloride, separating the solid chlorides from the liquid, recovering silver from the sodium chloride-silver chloride crystals and reclaiming the sodium chloride, adding water to the liquid and cooling it to crystallize cuprous chloride. The procedure is adaptable to processes for recovering copper from its ores in which copper is reduced to cuprous chloride in a leach slurry followed by cooling the leach slurry to crystallize out the cuprous chloride from which copper is recovered by conventional techniques.

This invention relates to methods, systems and apparatus for producing primary treated brine, i.e. <20 ppm calcium, magnesium, strontium and barium ions at the wellhead of underground salt caverns formed by depletion of their salt content by previous solution mining operations. The purified brine produced is maintained in an anerobic state and transported to chlor-alkali plant installations for use in electrolysis cells for the production of chlorine, sodium hydroxide and hydrogen. Raw brine produced at an operating brine wellhead is injected into a depleted salt cavern along with the treatment chemicals required to purify the raw brine. A novel installation including a producing well or wells, a depleted well cavern or caverns, and support facilities for producing primary treated brine is provided. Also, special wellhead injection tubing, a mixer and radial distributor for injecting the fluids into the cavern are employed which allows for the chemical reaction, precipitation, settling and clarification operations to take place in a pre-selected reaction zone in the cavern. The cavern acts as the reactor for precipitation, settler and clarifier and deposition site for storage of the precipitates which are innocuous solid by-products of the purification process. The methods, systems, installations and apparatus of this invention provide environmental, investment cost and operating advantages, as compared to surface brine treating facilities and operations at the chlor alkali plant installation, or, as compared to other subterranean attempts to purify brine.

This invention relates to methods, systems and apparatus for producing primary treated brine, i.e. <20 ppm calcium, magnesium, strontium and barium ions at the wellhead of underground salt caverns formed by depletion of their salt content by previous solution mining operations. The purified brine produced is maintained in an anerobic state and transported to chlor-alkali plant installations for use in electrolysis cells for the production of chlorine, sodium hydroxide and hydrogen. Raw brine produced at an operating brine wellhead is injected into a depleted salt cavern along with the treatment chemicals required to purify the raw brine. A novel installation including a producing well or wells, a depleted well cavern or caverns, and support facilities for producing primary treated brine is provided. Also, special wellhead injection tubing, a mixer and radial distributor for injecting the fluids into the cavern are employed which allows for the chemical reaction, precipitation, settling and clarification operations to take place in a pre-selected reaction zone in the cavern. The cavern acts as the reactor for precipitation, settler and clarifier and deposition site for storage of the precipitates which are innocuous solid by-products of the purification process. The methods, systems, installations and apparatus of this invention provide environmental, investment cost and operating advantages, as compared to surface brine treating facilities and operations at the chlor alkali plant installation, or, as compared to other subterranean attempts to purify brine.