Solution mining of trona or nahcolite ore with electrodialytically-produced aqueous sodium hydroxide
AssigneeIntermountain Research and Development Corporation
InventorsWilliam C. Copenhafer, Henry A. Pfeffer, III
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Abstract
A cyclic solution mining method that uses aqueous sodium hydroxide for recovering valuable alkali values, preferably as soda ash, from subterranean deposits of trona or nahcolite, even when such deposits are NaCl-contaminated. The aqueous sodium hydroxide mining solvent is generated via electrodialysis of a recirculating sodium chloride brine stream. Hydrogen chloride that is also generated in the cell's operation is neutralized with aqueous sodium carbonate, to regenerate sodium chloride brine that is recirculated to the electrodialysis cell as brine feed.
Claims15
A cyclic method for solution mining subterranean ore deposits of trona or nahcolite, which comprises
- (i) contacting a subterranean trona or nahcolite ore deposit with aqueous sodium hydroxide solvent, prepared from electrodialysis of a brine, to form aqueous sodium carbonate;
- (ii) withdrawing aqueous sodium carbonate mining solution from the region of the ore deposit, whereby soda ash may be recovered from the withdrawn mining solution;
- (iii) preparing aqueous sodium hydroxide solvent by electrodialyzing a recirculating aqueous sodium chloride brine stream in an electrodialysis cell to yield aqueous cell effluents containing sodium hydroxide, hydrogen chloride and depleted sodium chloride brine, said electrodialysis cell consisting of one or more electrodialysis unit cells containing an acid zone, a salt zone, and a base zone;
- (iv) employing the aqueous sodium hydroxide cell effluent as aqueous sodium hydroxide solvent for solution mining of the subterranean ore deposit;
- (v) neutralizing the aqueous hydrogen chloride cell effluent with aqueous sodium carbonate;
- and
- (vi) introducing the neutralized aqueous hydrogen chloride, along with the depleted aqueous sodium chloride cell effluent brine, into the electrodialysis cell, thereby providing for substantially complete recycle of the aqueous chloride in the operation of the electrodialysis cell.
An integrated cyclic method for solution mining subterranean trona ore deposits, which comprises
- (i) contacting a subterranean trona ore deposit with aqueous sodium hydroxide solvent, prepared from electrodialysis of a brine, to form aqueous sodium carbonate;
- (ii) withdrawing aqueous sodium carbonate mining solution from the region of the ore deposit;
- (iii) recovering soda ash from the withdrawn mining solution by evaporative crystallization of sodium carbonate monohydrate;
- (iv) preparing aqueous sodium hydroxide solvent by electrodialyzing a recirculating aqueous brine stream in an electrodialysis cell having three zones per cell unit, to yield, as cell effluents, aqueous sodium hydroxide, aqueous hydrogen chloride, and an aqueous brine stream depleted in sodium chloride;
- (v) employing the aqueous sodium hydroxide cell effluent as aqueous sodium hydroxide solvent for solution mining of the subterranean ore deposit;
- (vi) neutralizing the aqueous hydrogen chloride cell effluent with aqueous sodium carbonate liquor diverted from the crystallization operation of the soda ash recovery;
- and
- (vii) discarding a portion of neutralized hydrogen chloride or depleted sodium chloride brine as purge, prior to their reintroduction into the electrodialysis cell, in an amount sufficient to maintain the concentrations of sodium chloride and anionic impurities in the recirculating brine stream at relatively constant levels.
Dependencies are inferred from the claim text.