Prevention of calcium deposition from trona-derived sodium carbonate liquors

Claim 2

IN A PROCESS FOR THE PRODUCTION OF SODA ASH FROM NATURAL TRONA WHICH COMPRISES CRUSHING THE TRONA, CALCINING THE CRUSHED TRONA, DISSOLVING THE SODIUM CARBONATE VALUES OF THE CALCINED TRONA IN AQUEOUS MEDIUM IN A DISSOLVING ZONE AT A TEMPERATURE OF FROM ABOUT 83* TO 110*C TO PROVIDE A SUBSTANTIALLY SATURATED SODIUM CARBONATE SOLUTION CONTAINING SOLUBLE CALCIUM IONS AND UNSOLUBLE IMPURITIES, SEPARATING THE INSOLUBLE IMPURITIES FROM SAID SATURATED SODIUM CARBONATE SOLUTION, CRYSTALLIZING SODIUM CARBONATE MONOHYDRATE FROM SAID SEPARATED SATURATED SODIUM CARBONATE SOLUTION, SEPARATING THE SODIUM CARBONATE MONOHYDRATE CRYSTALS AND CALCINING THE SEPARATED MONOHYDRATE CRYSTALS TO PRODUCE SODA ASH, THE IMPROVEMENT WHICH COMPRISES INTRODUCING PIRSSONITE INTO SAID SUBSTANTIALLY SATURATED SODIUM CARBONATE SOLUTION, SAID PIRSSONITE BEING INTRODUCED IN AN AMOUNT OF BETWEEN ABOUT 0.1 AND 5% BY WEIGHT, BASED ON THE WEIGHT OF THE CISSOLVES CALCINED TRONA IN THE SOLUTION.

Claim 3

The process according to claim 1 wherein said pirssonite is introduced into said substantially saturated sodium carbonate solution in an amount of between about 0.2 and 2% by weight, based on the weight of the dissolved calcined trona in the solution.

Claim 4

The process according to claim 1 wherein the pirssonite introduced into said substantially saturated sodium carbonate solution is obtained by recycling to said solution insoluble impurities containing pirssonite.

Claim 5

The process according to claim 3 wherein the amount of insoluble impurities recycled to said solution is between 30 and 70% of the weight of insoluble impurities in the calcined trona.

Claim 6

In a process for the production of soda ash from natural trona which comprises crushing the trona, calcining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80* to 110*C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the improvement which comprises: contacting said substantially saturated sodium carbonate solution with pirssonite-containing insoluble matter for a sufficient time to effect reduction of the soluble calcium ions in said saturated sodium carbonate solution to less than about 15 parts per million.

Claim 7

In a process for the production of soda ash from natural trona which comprises crushing the trona, calcining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80* to 110*C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the improvement which comprises: contacting said substantially saturated sodium carbonate solution with pirssonite-containing insoluble matter for a sufficient time to effect reduction of the soluble calcium ions in said saturated sodium carbonate solution to less than about 15 parts per million.

Claim 8

The process according to claim 5 wherein said pirssonite-containing insoluble matter comprises insoluble impurities produced in the dissolVing of the calcined trona.

Claim 9

The process according to claim 5 wherein said pirssonite-containing insoluble matter is obtained by recycling to said dissolving zone insoluble impurities separated from said saturated sodium carbonate solution.

Claim 10

The process according to claim 5 wherein said substantially saturated sodium carbonate solution is contacted with said pirssonite containing insoluble matter for a period of between 2 and 5 hours.

Claim 11

In a process for the production of soda ash from natural trona which comprises crushing the trona, calcining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80* to 110*C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the improvement which comprises: (a) separating the insoluble impurities from the saturated sodium carbonate solution by transferring a first portion of the saturated sodium carbonate solution from the dissolving zone to a thickening zone wherein said first portion is treated to concentrate the insoluble matter by separating therefrom sodium carbonate solution containing a lesser concentration of insoluble matter; (b) returning the concentrated insoluble matter to the dissolving zone in an amount of between 30 and 70% of the weight of the insoluble impurities in the calcined trona; (c) passing the separated sodium carbonate solution containing the lesser concentration of insoluble matter to a clarification zone; (d) transferring a second portion of the saturated sodium carbonate solution from the dissolving zone to the clarification zone; (e) clarifying the solutions transferred to said clarification zone to obtain a clear sodium carbonate solution containing less than 15 parts per million by weight of solubilized calcium salts; and (f) passing said clear sodium carbonate solution from the clarification zone to the crystallization zone for crystallization of sodium carbonate monohydrate from said solution.

Claim 12

In a process for the production of soda ash from natural trona which comprises crushing the trona, calcining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80* to 110*C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the improvement which comprises: (a) separating the insoluble impurities from the saturated sodium carbonate solution by transferring a first portion of the saturated sodium carbonate solution from the dissolving zone to a thickening zone wherein said first portion is treated to concentrate the insoluble matter by separating therefrom sodium carbonate solution containing a lesser concentration of insoluble matter; (b) returning the concentrated insoluble matter to the dissolving zone in an amount of between 30 and 70% of the weight of the insoluble impurities in the calcined trona; (c) passing the separated sodium carbonate solution containing the lesser concentration of insoluble matter to a clarification zone; (d) transferring a second portion of the saturated sodium carbonate solution from the dissolving zone to the clarification zone; (e) clarifying the solutions transferred to said clarification zone to obtain a clear sodium carbonate solution containing less than 15 parts per million by weight of solubilized calcium salts; and (f) passing said clear sodium carbonate solution from the clarification zone to the crystallization zone for crystallization of sodium carbonate monohydrate from said solution.