# US 2019/0169056 A1 · Salt production from wastewater > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0169056 A1 - Document ID: US20190169056A1 - Status: Published application - Kind: A1 - Application number: 16/207,908 - Filed: 2018-12-03 - Published: 2019-06-06 - Earliest claimed: 2017-12-04 - Assignees: Aquatech International Corporation - Applicants: Aquatech International, LLC - Inventors: Daniel P. Bjorklund; Vinod A. Raje; James M. Marlett; Manish Backliwal; Richard Schoen; Gregory Mandigo - Web page: https://patentgrep.com/patent/US20190169056A1 ## CPC - C02F 9/00: Multistage treatment of water, waste water or sewage - C02F 1/048: {Purification of waste water by evaporation} - C02F 1/42: by ion-exchange (ion-exchange in general B01J) - C02F 1/441: {by reverse osmosis} - C02F 1/442: {by nanofiltration} - C02F 1/5236: {using inorganic agents} - C02F 1/66: by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) - C02F 11/121: by mechanical de-watering - C02F 2001/425: {using cation exchangers} - C02F 2001/5218: {Crystallization} - C02F 2101/10: Inorganic compounds - C02F 2103/001: {Runoff or storm water} - C02F 2103/365: {from petrochemical industry (e.g. refineries)} - C02F 2301/08: Multistage treatments, e.g. repetition of the same process step under different conditions - Y02W 10/37: using solar energy - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) - Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT ## Abstract Many processes generate wastewater streams rich in sulfate and chloride. These salt components are traditionally not recovered and are discharged to the environment. The invention recovers pure water for recycle/reuse and simultaneously generates valuable pure salts of NaCl and Na2SO4 for beneficial reuse, eliminating the waste stream. Process consists of the sequential crystallization of salt products with an intermediate purification step in which a chemical reactant is added to elevate levels of purity. The process is configured to simultaneously achieve zero liquid discharge. ## Claims ### Claim 1 A method for salt production from a wastewater stream, comprising: a) providing a wastewater stream comprising sulfate ions and chloride ions; b) pretreating the wastewater stream with at least one unit operation selected from the group consisting of hardness removal, silica reduction, alkalinity reduction, total organic carbon reduction, and pH adjustment; c) feeding the wastewater stream to a first stage crystallizer, thereby precipitating and growing sodium sulfate crystals in a first mother liquor; d) separating the sodium sulfate crystals from the first mother liquor; e) collecting the first mother liquor and sending it to a chemical reaction vessel; f) dosing a reactive chemical to the chemical reaction vessel, thereby removing sulfate ion from solution in the wastewater stream as a precipitated solid and removing the precipitated solid to produce a purified sodium chloride brine; g) sending the purified sodium chloride brine into a second stage crystallizer, thereby precipitating and growing sodium chloride crystals in a second mother liquor; and h) separating the sodium chloride crystals from the second mother liquor. ### Claim 2 (depends on 1) The method of claim 1, wherein the wastewater stream is a coal to gas wastewater stream. ### Claim 3 (depends on 1) The method of claim 1, further comprising concentrating the wastewater stream prior to at least one of the pretreatment step and the step of sending the wastewater stream to a chemical reaction vessel. ### Claim 4 (depends on 3) The method of claim 3, wherein the concentration step includes at least one process selected from the group consisting of membrane concentration and thermal evaporation. ### Claim 5 (depends on 1) The method of claim 1, wherein said separating steps are conducted by dewatering in a centrifuge. ### Claim 6 (depends on 1) The method of claim 1, wherein said reactive chemical is selected from the group consisting of CaCl2, Ca(NO3)2 , and Ca(OH)2. ### Claim 7 (depends on 2) The method of claim 2, further comprising recycling water from the second mother liquor into a coal gasification process. ### Claim 8 (depends on 1) The method of claim 1, further comprising washing and/or drying the sodium sulfate salt, thereby enhancing its purity. ### Claim 9 (depends on 1) The method of claim 1, further comprising washing and/or drying the sodium chloride salt, thereby enhancing its purity. ### Claim 10 (depends on 1) The method of claim 1, comprising removing a purge stream from the second stage crystallizer, thereby enhancing salt purity. ### Claim 11 (depends on 10) The method of claim 10, further comprising processing the purge stream in a processor selected from the group consisting of a mixed-salt crystallizer and a dryer. ### Claim 12 (depends on 7) The method of claim 7, wherein the coal gasification process and method for salt production operate as a zero liquid discharge system with respect to water. ### Claim 13 (depends on 1) The method of claim 1, wherein the pretreatment step is a hardness removal step, and wherein the hardness removal step produces a regeneration waste stream from an ion exchanger. ### Claim 14 (depends on 13) The method of claim 13, wherein the regeneration waste stream comprises CaCl2, and wherein said CaCl2 is recycled as a reactive chemical. ### Claim 15 (depends on 1) The method of claim 1, comprising evaporating water in the crystallizer with at least one of mechanical vapor compression, steam driven, multiple effect evaporation, and thermo-compressor driven evaporation. ### Claim 16 (depends on 4) The method of claim 4, wherein the preconcentrating step is a membrane concentration step, and wherein the membrane concentration step is a nanofiltration that rejects substantially all (more than 90% of the influent) of the sulfate ion from the waste stream. ### Claim 17 A method for salt production from a wastewater stream, comprising: a) providing a wastewater stream comprising sulfate ions and chloride ions; b) pretreating the wastewater stream with at least one unit operation selected from the group consisting of hardness removal, silica reduction, alkalinity reduction, total organic carbon reduction, and pH adjustment; c) sending the wastewater stream to a chemical reaction vessel; d) dosing a reactive chemical to the chemical reaction vessel, thereby removing sulfate ion from solution in the wastewater stream as a precipitated solid and removing the precipitated solid to produce a purified sodium chloride brine; e) sending the purified sodium chloride brine into a second stage crystallizer, thereby precipitating and growing sodium chloride crystals in a second mother liquor; and f) separating the sodium chloride crystals from the second mother liquor. ### Claim 18 (depends on 17) The method of claim 17, wherein the concentration step includes at least one process selected from the group consisting of membrane concentration and thermal evaporation. ### Claim 19 (depends on 18) The method of claim 18, wherein the preconcentrating step is a membrane concentration step, and wherein the membrane concentration step is a nanofiltration that rejects substantially all (more than 90% of the influent) of the sulfate ion from the waste stream. ### Claim 20 (depends on 17) The method of claim 17, comprising evaporating water in the crystallizer with at least one of mechanical vapor compression, steam driven, multiple effect evaporation, and thermo-compressor driven evaporation.