# US 2009/0260993 A1 · Method for obtaining sodium carbonate crystals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260993 A1 - Document ID: US20090260993A1 - Status: Published application - Kind: A1 - Application number: 12/440,486 - Filed: 2007-09-12 - Published: 2009-10-22 - Earliest claimed: 2006-09-14 - Assignees: Solvay (Societe Anonyme) - Inventors: Francis M. Coustry; Michel Hanse - Web page: https://patentgrep.com/patent/US20090260993A1 ## CPC - C01D 7/07: Preparation from the hydroxides - C01D 7/24: Crystallisation - C25B 1/34: Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis - C25B 15/08: Supplying or removing reactants or electrolytes; Regeneration of electrolytes - C25B 15/083: {Separating products} - C25B 15/085: {Removing impurities} - C01D: COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides C01B17/22; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia and cyanogen, containing nitrogen and other non-metals C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; phosphides C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20) - C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B) ## Abstract Method for producing sodium carbonate, according to which an aqueous sodium chloride solution (5) is electrolyzed in a membrane-type cell (1) from which an aqueous sodium hydroxide solution (9) is collected, and carbonated by direct contact with carbon dioxide (15) to form a slurry of crystals of anhydrous sodium carbonate (16). ## Claims ### Claim 1 A method for producing sodium carbonate, comprising electrolyzing an aqueous sodium chloride solution in a membrane-type cell (1) with an ion permselective membrane in order to produce hydrogen (8), chlorine (7) and an aqueous solution (9) comprising sodium hydroxide, and submitting the aqueous solution (9) comprising sodium hydroxide to a carbonation (2) wherein the carbonation (2) is carried out by directly contacting carbon dioxide (15) with the aqueous solution (9) comprising sodium hydroxide in a gas liquid contactor under conditions such as to cause the conversion of the aqueous solution (9) into an aqueous slurry (16) of anhydrous sodium carbonate crystals. ### Claim 2 (depends on 1) The method according to claim 1, wherein the temperature inside the gas-liquid contactor is above 100° C. ### Claim 3 (depends on 1) The method according to claim 1, wherein the direct contacting of the carbon dioxide (15) with the aqueous sodium hydroxide solution (9) in the gas liquid contactor is carried out by circulating said solution (9) in countercurrent to a gas containing the carbon dioxide in a carbonation tower consisting of a stack of at least two superimposed segments separated by a partition perforated with at least two openings, the segments comprising at least one transverse wall for causing circulation of the solution in said segment. ### Claim 4 (depends on 1) The method according to claim 1, wherein the aqueous solution (9) comprising sodium hydroxide is essentially free of carbonate ions, bicarbonate ions or both, when directly contacted with the carbon dioxide. ### Claim 5 (depends on 1) The method according to claim 1, wherein a chlorine derivative (39) is produced in a chlorine derivative production unit (13) from the chlorine (7) and wherein the carbonation (2) is effected at least partly using carbon dioxide (15) produced in the chlorine derivative production unit (13). ### Claim 6 (depends on 1) The method according to claim 1, wherein the slurry (16) is evaporated in order to produce sodium carbonate crystals, which are separated, and a mother liquor. ### Claim 7 (depends on 6) The method according to claim 6, wherein, to evaporate the slurry (16), said slurry (16) is treated in an evaporator-crystallizer (3). ### Claim 8 (depends on 7) The method according to claim 7, wherein the evaporator-crystallizer (3) comprises a multistage evaporator or a mechanical vapour recompression evaporator. ### Claim 9 (depends on 1) The method according to claim 1, wherein the electrolysis in the cell (1) is regulated so that the aqueous sodium hydroxide solution (9) comprises about 32% by weight of sodium hydroxide. ### Claim 10 (depends on 7) The method according to claim 7, wherein the operating conditions in the evaporator-crystallizer (3) are regulated so that the sodium carbonate crystals resulting from the evaporation of the slurry (16) are crystals of sodium carbonate monohydrate. ### Claim 11 (depends on 1) The method according to claim 1, wherein at least part of the carbon dioxide (15) used is obtained by attacking limestone (14) with an aqueous hydrochloric acid solution (12) obtained by absorbing, in water (11), hydrogen chloride obtained by reacting (10) chlorine (7) with hydrogen (8) produced in the membrane-type cell (1). ### Claim 12 (depends on 1) The method according to claim 1, wherein at least part of the chlorine (7) is utilized in a vinyl chloride monomer production plant producing hydrochloric acid, at least a part of the produced hydrochloric acid being reacted with limestone (14) to produce at least a part of the carbon dioxide (15) used. ### Claim 13 (depends on 1) The method according to claim 1, wherein at least part of the carbon dioxide (15 used is a flue gas from a thermal installation for cogeneration of heat and power. ### Claim 14 (depends on 1) The method according to claim 1, wherein the membrane-type cell (1) comprises at least one anode chamber, and wherein a dilute brine (29) is collected from the membrane-type cell (1) and recycled in the anode chamber of the cell (1), after having purified and concentrated it with sodium chloride. ### Claim 15 (depends on 14) The method according to claim 14, wherein the dilute brine (29) is concentrated by circulating it in a rock salt deposit (22).