Recovery of alkali values from trona deposits
AssigneeFMC Corporation
InventorsMichael L. Pinsky, John Walden
Life of this patent
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Abstract
A cyclic method for recovering alkali values from subterranean trona deposits. The ore is contacted via solution mining with an aqueous mining solvent containing sodium hydroxide, the resulting Na.sub.2 CO.sub.3 -containing solution is withdrawn and carbonated, and sodium sesquicarbonate and/or sodium bicarbonate is crystallized and separated from the solution. The crystallized solids are calcined in a direct coal-fired calciner, and the resultant anhydrous soda ash is recrystallized in water to form sodium carbonate monohydrate or anhydrous sodium carbonate, which is recovered as a dense alkali product. Aqueous mining solvent is regenerated by causticization of one or more of the various liquor streams, and the recovery cycle is repeated.
Claims16
A method for recovering alkali values from underground trona deposits which comprises
- (i) introducing into the region of the trona deposit an aqueous mining solvent having dissolved therein from about 2 to 7% by weight sodium hydroxide;
- (ii) maintaining the solvent in the region for a period sufficient to solubilize at least a portion of the trona as sodium carbonate;
- (iii) withdrawing from the region at least a portion of the resulting mining solution;
- (iv) carbonating at least a portion of the withdrawn mining solution to convert the major portion of the sodium carbonate contained therein into sodium sesquicarbonate and/or sodium bicarbonate;
- (v) crystallizing the sodium sesquicarbonate and/or sodium bicarbonate;
- (vi) separating the crystallized solids from the mining solution mother liquor;
- (vii) calcining the crystallized solids in a direct coal fired calciner to form anhydrous sodium carbonate contaminated with impurities;
- (viii) recrystallizing the contaminated anhydrous sodium carbonate in water to form sodium carbonate-containing crystals while the contaminants remain in the aqueous liquor;
- (ix) separating purified sodium carbonate-containing crystals from the aqueous liquor containing contaminants;
- (x) maintaining an aqueous purge of liquor containing said contaminants;
- (xi) adding sodium hydroxide and water to at least one of said liquors, the amounts of sodium hydroxide and water being adjusted so as to form an aqueous mining solvent containing from about 2 to 7% by weight sodium hydroxide;
- and
- (xii) reintroducing the resulting aqueous mining solvent into the region of the trona deposit and repeating the cycle of recovery.
Dependencies are inferred from the claim text.