Claims
- 1. A process for preparing dendritic salt of high purity and low calcium sulfate content which process consists of continuously feeding raw sodium chloride brine containing dissolved calcium sulfate in an amount of from about 0.5 to about 5.5 grams per liter and considerable quantities of calcium bicarbonate into an evaporating and crystallizing chamber, concentrating and evaporating said brine at an elevated temperature below about 220.degree. F. and at a reduced pressure in the presence of no more than from about 5 to 500 parts per million on a saturated brine basis of an alkali metal polyphosphate, adding to said brine an alkali metal ferrocyanide at a rate sufficient to produce a crystalline dendritic salt having a bulk density not exceeding about 59 pounds per cubic foot and containing less than about 13 parts per million of said alkali metal ferrocyanide, concomitantly bleeding brine from said evaporating chamber at a rate such that the maximum calcium sulfate content the brine reachs in the evaporating chamber is from about 11/2 to about 2 times that of its concentration in the raw brine, the rate of feed of raw brine to said evaporating chamber and the concomitant rate of bleed of brine therefrom being adjusted to maintain calcium sulfate in solution, and concomitantly withdrawing solid dendritic sodium chloride crystals from said evaporating chamber, said sodium chloride containing not more than about 30 parts per million of calcium and magnesium combined, expressed as calcium.
- 2. The process of claim 1 wherein the alkali metal ferrocyanide is sodium ferrocyanide.
- 3. The process of claim 1 wherein said concomitantly bleeding brine from said evaporating chamber is at a rate equal to from 40 percent to 70 percent of the brine feed rate.
- 4. The process of claim 1 wherein the concentrating and evaporating are at a temperature below about 165.degree. F. at reduced pressure and in the presence of from about 5 to 100 parts per million on a saturated brine basis of sodium hexametaphosphate.
- 5. The process of claim 1 wherein the alkali metal polyphosphate is sodium hexametaphosphate and is present in a concentration of from about 5 to about 100 parts per million on a saturated brine basis, and the alkali metal ferrocyanide is sodium ferrocyanide.
- 6. The process of claim 1 wherein said concomitantly withdrawing solid sodium chloride in dendritic form from said evaporating chamber is as a slurry in saturated brine, filtering and washing said sodium chloride with brine and water, and recovering and drying the sodium chloride from said process.
Parent Case Info
This is a division of Ser. No. 554,649, filed Mar. 3, l975 now U.S. Pat. No. 3,925,027; which is a division of Ser. No. 480,615, filed June 19, 1974, now U.S. Pat. No. 3,891,397 which is a continuation-in-part of Ser. No. 439,289, filed Feb. 4, 1974, now abandoned.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
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224,032 |
Sep 1959 |
AU |
Divisions (2)
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Number |
Date |
Country |
Parent |
554649 |
Mar 1975 |
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Parent |
480615 |
Jun 1974 |
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Continuation in Parts (1)
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Number |
Date |
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Parent |
439289 |
Feb 1974 |
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