Method of producing soda ash

Claim 1

The method of producing dense soda ash comprising, calcining crude sodium sesquicarbonate to convert it to sodium carbonate, then mixing the calcined ore with water and dissolving the sodium carbonate and other soluble salts therein, then removing the undissolved solids and coloring material from the aqueous sodium carbonate, then evaporating water from the sodium carbonate solution while maintaining the solution under pressure and at a temperature at which the stable solid phase field of the solution is anhydrous sodium carbonate to crystallize anhydrous sodium carbonate, then adding a co-solute of sodium hydroxide to said solution in sufficient amount to maintain the stable solid phase field of the solution as anhydrous sodium carbonate at not more than atmospheric pressure and reducing the pressure on said solution to not more than atmospheric to crystallize additional sodium carbonate, separating said crystals from the mother liquor, drying said crystals, evaporating at least a portion of the mother liquor to as high a concentration of sodium hydroxide as is possible wherein the only stable solid phase is anhydrous sodium carbonate, separating the anhydrous sodium carbonate crystals thus formed from the mother liquor, further evaporating water from the mother liquor to raise the sodium hydroxide concentration to a value at which substantially all of the undesirable sodium sulfate has crystallized as the triple salt sodium hydroxide-sodium chloride-sodium sulfate and crystals of sodium chloride and sodium carbonAte are formed, separating the said triple salt and sodium chloride and sodium carbonate solid phases from the mother liquor, cooling the said mother liquor to form additional solid phase sodium chloride, separating the solid phase sodium chloride from said mother liquor and recycling said mother liquor to the co-solute addition step, decomposing said separated triple salt in the presence of solid sodium carbonate by adding sufficient water to form solid phases of sodium chloride and sodium sulfate, separating said solid phases from resulting mother liquor, and returning said mother liquor to the triple salt crystallization step.

Claim 2

The method of removing sodium carbonate, sodium chloride and sodium sulfate from a liquor containing sodium hydroxide comprising, evaporating water from said solution to increase the concentration of sodium hydroxide therein to crystallize solid phase sodium carbonate, said evaporation being controlled to maintain the level of sodium hydroxide below that at which co-crystallization of chloride and sulfate containing solids is encountered, separating the solid phase sodium carbonate thus formed from the mother liquor, then evaporating water from said solution to raise the sodium hydroxide concentration to a level greater than 30 percent to crystallize the triple salt sodium hydroxide-sodium chloride-sodium sulfate, sodium chloride and sodium carbonate, separating the said triple salt, sodium chloride and sodium carbonate solids from the mother liquor, then cooling the mother liquor to further crystallize solid phase sodium chloride and obtain a relatively pure sodium hydroxide liquor, and separating the solid phase sodium chloride thus formed from the mother liquor.

Claim 3

The method of removing sodium carbonate, sodium chloride and sodium sulfate from a liquor containing sodium hydroxide comprising, evaporating water from said solution to increase the concentration of sodium hydroxide therein to crystallize solid phase sodium carbonate, said evaporation being controlled to maintain the level of sodium hydroxide below that at which co-crystallization of chloride and sulfate containing solids is encountered, separating the solid phase sodium carbonate thus formed from the mother liquor, then evaporating water from said solution to raise the sodium hydroxide concentration to a level greater than 30 percent to crystallize the triple salt sodium hydroxide-sodium chloride-sodium sulfate, sodium chloride and sodium carbonate, separating the said triple salt, sodium chloride and sodium carbonate solids from the mother liquor, then cooling the mother liquor to further crystallize solid phase sodium chloride and obtain a relatively pure sodium hydroxide liquor, separating the solid phase sodium chloride thus formed from the mother liquor, decomposing said triple salt by adding water thereto to form solid phase sodium chloride and sodium sulfate, separating the solids from the mother liquor and returning the mother liquor to the triple salt crystallization step.

Claim 4

The method of producing dense soda ash comprising, calcining crude sodium sesquicarbonate to convert it to sodium carbonate, then mixing the calcined ore with water and dissolving the sodium carbonate and other soluble salts therein, then removing the undissolved solids and coloring material from the aqueous sodium carbonate, then evaporating water from the sodium carbonate solution while maintaining the solution under pressure and at a temperature at which the stable solid phase field of the solution is anhydrous sodium carbonate to crystallize anhydrous sodium carbonate, then adding a co-solute selected from the group consisting of sodium hydroxide and sodium chloride to said solution in sufficient amount to maintain the stable solid phase field of the solution as anhydrous sodium carbonate at not more than atmospheric pressure and reducing the pressure on said solUtion to not more than atmospheric to crystallize additional anhydrous sodium carbonate, separating said crystals from the mother liquor, drying said crystals, further evaporating water from the mother liquor to crystallize anhydrous sodium carbonate, and separating said last formed crystals from the mother liquor and returning said last formed crystals to the co-solute addition step.

Claim 5

The method of removing sodium carbonate, sodium chloride and sodium sulfate from a liquor containing sodium hydroxide comprising, evaporating water from said solution to increase the concentration of sodium hydroxide therein to crystallize solid phase sodium carbonate, said evaporation being controlled to maintain the level of sodium hydroxide below that at which co-crystallization of chloride and sulfate containing solids is encountered, separating the solid phase sodium carbonate thus formed from the mother liquor, then evaporating water from said solution to raise the sodium hydroxide concentration to a level greater than 30 percent to crystallize the triple salt sodium hydroxide-sodium chloride-sodium sulfate, sodium chloride and sodium carbonate, separating the said triple salt, sodium chloride and sodium carbonate solids from the mother liquor, decomposing said triple salt by adding water thereto to form solid phase sodium chloride and sodium sulfate, separating the solids from the mother liquor and returning a portion of the mother liquor to the triple salt crystallization step.