TH79245A - Method for the salt crystallization of soluble anions from brine. - Google Patents

Abstract

DC60 (01/02/49) The invention relates to the removal of at least some of the soluble alkali metal salts or divalent anions from brine solutions containing the alkali metal or ammonium ions and divalent anions in aqueous solutions, comprising the following steps: - obtaining a brine solution having a sodium chloride concentration between 150 g/L and saturation in the presence or absence of a crystallization inhibitor for sodium chloride, or having a sodium chloride concentration greater than saturation in the presence of a crystallization inhibitor for sodium chloride, said brine solution optionally comprising a crystallization inhibitor for the alkali metal salt or divalent ammonium anion; - acidifying said solution to a pH below 11.5 while maintaining a sodium chloride concentration of at least 150 g/L; - if the concentration of the crystallization inhibitor for the alkali metal salt or - if the concentration of the alkali metal salts or the divalent ammonium anion in the brine solution is less than 20 mg/l, the addition of such a quantity of crystallization inhibitor such that the obtained brine solution contains at least 20 mg/l of the alkali metal salts or the divalent ammonium anion; - subjecting the obtained solution to a membrane filtration step, thereby separating the brine solution into a supersaturated brine stream for salts containing divalent anions (concentrates) and a sub-supersaturated brine stream for salts containing divalent anions (permeables); - if the concentration of the alkali metal salts or the divalent ammonium anion in the concentrate is less than 20 mg/l, the addition of such a quantity of the alkali metal salts or the divalent ammonium anion in the concentrate, such that the concentrated solution contains at least 20 mg/l of the alkali metal salts or the divalent ammonium anion; - subjecting the concentrate to a crystallization process, - removing the alkali metal salt or divalent anion crystallized by the ammonium; and - optionally returning at least part of the mother liquor of the crystallized by the brine solution to subject it to a membrane filtration step. The invention relates to removing at least part of the alkali metal salt or divalent anion soluble by the ammonium from a brine solution containing the alkali metal or ammonium ion and the divalent anion in the aqueous solution, comprising the following steps: - obtaining a brine solution having a sodium chloride concentration between 150 g/L and saturation in the presence or absence of a crystallization inhibitor for sodium chloride, or having a sodium chloride concentration greater than saturation in the presence of a crystallization inhibitor for sodium chloride, said brine solution optionally comprising a crystallization inhibitor for the alkali metal or divalent anion salt; - if necessary, acidifying the solution to a pH below 11.5 while maintaining a sodium chloride concentration of at least 150 g/l; - if the concentration of the alkali metal salts or divalent ammonium anions in the brine solution is less than 20 mg/l, adding an amount of such alkali metal salts such that the obtained brine solution contains at least 20 mg/l of the alkali metal salts or divalent ammonium anions; - subjecting the obtained solution to a membrane filtration step, thereby separating the brine solution into a supersaturated brine stream for salts containing divalent anions (concentrate) and a sub-supersaturated brine stream for salts containing divalent anions (permeate); - if the concentration of the alkali metal salts or - the addition of a quantity of such crystallization inhibitor such that the concentrate contains at least 20 mg/l of alkali metal salt or divalent ammonium anion; - the crystallization of the concentrate, - the removal of the alkali metal salt or divalent ammonium anion; and - optionally, the return of at least part of the mother liquor of the crystallization agent to the brine solution to subject it to a membrane filtration step.

Claims (11)

1. A method for removing at least some soluble alkali metal or ammonium anion salts of divalent anions from a saline solution containing alkali metals or ammonium ions and divalent anions in the aqueous basin, consisting of the following steps: - Exposure to a saline solution with a sodium chloride concentration between 150 g/L and saturation, with or without a crystal expansion inhibitor for sodium chloride, or with a sodium chloride concentration greater than saturation in the presence of a crystal expansion inhibitor for sodium chloride; such a saline solution is selected to contain a crystal expansion inhibitor for alkali metal salts or ammonium divalent anions; - If necessary, acidification of such solution to a pH below 11.5 while maintaining a sodium chloride concentration of at least 150 g/L; - If the concentration of the crystal expansion inhibitor for alkali metal salts or ammonium divalent anions... If the concentration of the crystal expansion inhibitor for alkali metal salts or divalent anion ammonium in the concentrated solution is less than 20 mg/L, the amount of such crystal expansion inhibitor is added, resulting in the obtained saline solution containing at least 20 mg/L of the crystal expansion inhibitor for alkali metal salts or divalent anion ammonium; - The obtained solution is then subjected to membrane filtration, thus separating the saline solution into a supersaturated stream for divalent anion-containing salts (concentrate) and a subsupersaturated stream for divalent anion-containing salts (permeable); - If the concentration of the crystal expansion inhibitor for alkali metal salts or divalent anion ammonium in the concentrated solution is less than 20 mg/L, the amount of such crystal expansion inhibitor is added, resulting in the obtained solution containing at least 20 mg/L of the crystal expansion inhibitor for alkali metal salts or divalent anion ammonium; - Crystallizing the resulting concentrate; - Removing the precipitated alkali metal salts or ammonium divalent anions; and - Optionally, returning at least a portion of the mother liqueur of the crystallized substance to the saline solution for further membrane filtration. 2. The method under claim 1 which makes a saturated saline solution for sodium chloride, or has a sodium chloride concentration between 275 g/L and saturation. 3. Methods under claim 1 or 2 where the divalent anion is sulfate or carbonate. 4. A method pursuant to one of the prior claims in which the alkali metal is sodium. 5. Under one of the preceding claims, the crystal expansion inhibitor for alkali metal salts or divalent ammonium anions is present in a concentration of at least 25 mg/L, and the recommended concentration is between 75-150 mg/L. 6. One of the preceding claims is a method for the expansion of crystals for alkali or ammonium salts of divalent anions selected from groups consisting of humic acid, polymaleic acid, polyacrylic acid, sugar, oligopeptide, polypeptide and polymers containing two or more carboxylic acid or carboxyalkyl groups and with the option of adding additional phosphate, phosphonate, phosphine, sulfate, and/or sulfonate groups. 7. Any method under the prior claim which has performed the acidification step in a scrub that uses at least CO2. 8. One of the preceding claims is met in which the pH of the saline solution introduced to the membrane filtration stage is between 2 and 11.5. 9. Any method under one of the prior claims which has performed the membrane filtration step by nanofiltration. 10. Any method under the preceding claim in which the crystallization step is carried out by adding alkali metal salt or ammonium of divalent anion grains to be crystallized. 11. Any method under the preceding claim that uses a permeable substance as a raw material for the production of sodium chloride or soda.