Recovering by-products from sea water brines and the like
OwnerDonald E. Garrettinventor
Life of this patent
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Abstract
The improved production of sodium sulfate, potassium sulfate and other valuable salts from salt plant bitterns or the like wherein initial reduction in sulfate ion concentration yields salt cake and greatly facilitates the selective recovery of potassium and other valuable by-product salts. The process includes cooling the bitterns while below a certain concentration to produce glauber salt, followed by successive solar evaporation steps to yield harvestable potash salts. The salts are selectively treated and then refined by flotation. The flotation overflow is converted to potassium sulfate product by decomposition and crystallization steps and the underflow provides a recycle salt mixture for converting the glauber salt to salt cake.
Claims23
A process for recovering commercially valuable by-product salts from the residual brines of a solar salt plant comprising:
- rapidly cooling an initial brine feedstock having a density of less than 29.degree. Be to a metastable condition at a temperature of less than about 0.degree. C. whereby glauber salt is caused to crystallize;
- converting said glauber salt to salt cake by treatment with a salt recycle mixture;
- subjecting mother liquor from the glauber salt crystals to a sequential water evaporation treatment for the selective harvesting of salts from a plurality of at least three solar evaporation ponds connected in series comprising a first pond from which sodium chloride is recovered, a second pond from which sylvinite is recovered, and a third pond from which mixed potash salts are recovered;
- converting the mixed potash salts to schoenite by a crystallization treatment;
- forming a crude mixture of said schoenite and the sylvinite and refining said mixture by flotation treatment whereby reject material from said flotation includes said salt recycle mixture;
- and
- converting the refined mixture to potassium sulfate.
A method of obtaining valuable by-products from sea water or other bitterns comprising:
- imposing a metastable condition upon said bitterns under which glauber salt will precipitate leaving a first liquor having a diminished sulfate ion level;
- removing water from said first liquor until sylvinite precipitates leaving a second liquor;
- removing water from said second liquor until a mixture of potash salts precipitate;
- recovering the precipitates of said sylvinite and said mixture of potash salts from the corresponding first and second liquors;
- converting the mixture of potash salts to schoenite;
- forming a primary mixture with said sylvinite and said schoenite and reacting said primary mixture to form potassium sulfate and a third liquor;
- and,
- recycling said third liquor to the schoenite conversion step.
A process for recovering potassium sulfate and sodium sulfate from salt-rich aqueous liquids comprising:
- A. Producing sodium sulfate by
- 1. maintaining said liquids in a glauber salt metastable crystallization zone;
- 2. forming glauber salt crystals in said liquids;
- 3. contacting said glauber salt crystals with a recycle mixture containing NaCl and MgSO.sub.4 to form sodium sulfate crystals and a first liquor;
- and,
- 4. recovering said sodium sulfate crystals from said first liquor.
- B. Producing potassium sulfate by
- 1. removing water from said first liquor until salts containing potassium precipitate in at least two separate stages to form at least a first sylvinite-rich fraction and a second mixed potash salt fraction;
- 2. forming a mixture with said first fraction and schoenite;
- 3. reacting said mixture to produce potassium sulfate;
- 4. recovering said potassium sulfate from the reaction mixture of B.3.
Dependencies are inferred from the claim text.