Method for producing potassium sulfate and sodium chloride from wastewater

10773,969

16/468436

November 22, 2017

A method of producing potassium sulfate by employing sodium sulfate and potassium chloride sources is disclosed. The method includes a crystallization process that yields a mother liquor containing sulfate, sodium and chloride. The mother liquor is directed to an anion segregation unit that produces a reject or retentate rich in sulfate which is recycled and employed in the production of the potassium sulfate. Further, the anion segregation unit produces a permeate that is depleted in sulfate but includes sodium and chloride and is directed to a sodium chloride crystallizer for producing sodium chloride.

Veolia Water Technologies, Inc. (Moon Township, IL, US)

Veolia Water Technologies, Inc. (Moon Township, PA, US)

1. A method of producing potassium sulfate comprising: directing a sodium sulfate source to a glaserite crystallizer; directing a liquor containing potassium sulfate from a downstream potassium sulfate reactor to the glaserite crystallizer and mixing the liquor containing the potassium sulfate with the sodium sulfate source; crystallizing glaserite in the glaserite crystallizer to form glaserite crystals and a mother liquor; separating the glaserite crystals from the mother liquor; directing the glaserite crystals to the downstream potassium sulfate reactor; directing a potassium chloride source to the potassium sulfate reactor and mixing the potassium chloride source with the glaserite crystals and precipitating potassium sulfate crystals; separating the potassium sulfate crystals from the liquor containing potassium sulfate; directing the mother liquor from the glaserite crystallizer to a nanofiltration unit and producing a reject or retentate stream rich in sulfate and a filtrate or permeate stream depleted in sulfate; recycling the reject or retentate stream to the glaserite crystallizer and combining the reject or retentate stream with the sodium sulfate source and the liquor containing the potassium sulfate in the glaserite crystallizer; and directing the filtrate or permeate stream to a sodium chloride crystallizer and producing sodium chloride crystals.

2. The method of claim 1 wherein potassium sulfate is produced in the absence of a mirabilite crystallization process upstream of the glaserite crystallizer.

3. The method of claim 1 including subjecting the mother liquor produced by the glaserite crystallizer to a treatment process prior to the mother liquor reaching the anion segregation unit wherein the treatment process reduces the tendency of the mother liquor to scale or clog the anion segregation unit.

4. The method of claim 1 wherein the sodium sulfate source comprises sodium sulfate crystals or a sodium sulfate brine or a sodium sulfate slurry; and wherein the potassium chloride source comprises potassium chloride crystals or a potassium chloride brine or a potassium chloride slurry.

5. The method of claim 1 wherein the sodium sulfate source is Glauber's salt and the method includes melting the Glauber's salt and directing the melted Glauber's salt to the glaserite crystallizer.

6. The method of claim 1 wherein the potassium chloride is mixed with a mixture of water and one or more liquors produced by the process and wherein the method includes subjecting the mixture to a softening process where hardness in the mixture is reduced.

7. The method of claim 1 wherein the sodium chloride crystallizer comprises a solar evaporation pond, basin or other facility and the method includes directing the permeate stream from the anion segregation unit to the solar evaporation pond, basin or facility.

8. A method for producing potassium sulfate from a waste stream, comprising: concentrating the waste stream to form a brine or a slurry; crystallizing mirabilite from the brine or slurry in a mirabilite crystallizer to form mirabilite crystals and a mirabilite crystallizer liquor; separating the mirabilite crystals from the mirabilite crystallizer liquor; mixing the mirabilite crystals with a potassium liquor; producing or forming glaserite crystals from the mirabilite crystals and potassium liquor in a glaserite reactor or a glaserite crystallizer; separating the glaserite crystals from the potassium liquor; directing the glaserite crystals to a potassium sulfate reactor; mixing a potassium source with the glaserite crystals in the potassium sulfate reactor to form potassium sulfate crystals and the potassium liquor; recycling the potassium liquor from the potassium sulfate reactor to the glaserite reactor or glaserite crystallizer; filtering the mirabilite crystallizer liquor to form a filtrate or permeate depleted in sulfate and a retentate or reject rich in sulfate; recycling the retentate or reject stream to the mirabilite crystallizer; directing the filtrate or permeate stream to a sodium chloride crystallizer and crystallizing sodium chloride crystals; and separating the sodium chloride crystals.

9. The method of claim 8 wherein the glaserite crystals are formed in the glaserite reactor and the method includes directing the potassium liquor from the glaserite reactor to the sodium chloride crystallizer.

10. The method of claim 9 wherein the sodium chloride crystallizer produces a concentrate that includes potassium and wherein the method includes directing at least a portion of the concentrate from the sodium chloride crystallizer to the glaserite reactor and mixing the concentrate with the mirabilite crystals.

11. The method of claim 8 wherein the potassium source is potassium chloride and wherein potassium chloride is added to the potassium sulfate reactor in the form of a slurry or a brine.

12. The method of claim 8 wherein the glaserite crystals are produced in the glaserite crystallizer; and wherein the method includes directing the potassium liquor from the glaserite crystallizer to a nanofiltration unit and producing a second reject stream and a second permeate stream; recycling the second reject stream to the glaserite crystallizer; and directing the second permeate stream to the sodium chloride crystallizer.

13. A method for producing potassium sulfate from a wastewater stream containing sodium and sulfate, comprising: directing the wastewater stream to a membrane separation unit and producing a reject stream and a permeate stream; concentrating the reject stream to form a first brine solution or a slurry; directing the first brine solution or slurry to a glaserite reactor; mixing potassium liquor with the first brine solution or slurry in the glaserite reactor and producing glaserite crystals; separating the glaserite crystals and directing the glaserite crystals to a potassium sulfate reactor; mixing a potassium source with the glaserite crystals to form potassium sulfate crystals; separating the potassium sulfate crystals; wherein the potassium source mixed with the glaserite crystals in the potassium sulfate reactor forms the potassium liquor that is mixed with the first brine stream or slurry in the glaserite reactor; concentrating the permeate stream to form a second brine stream or a second slurry; directing the second brine stream or second slurry to a sodium chloride crystallizer and crystallizing sodium chloride crystals; and separating the sodium chloride crystals.

14. The method of claim 13 wherein in the process of producing glaserite crystals in the glaserite reactor a sodium chloride liquor is formed and the method includes directing the sodium chloride liquor from the glaserite reactor to the sodium chloride crystallizer.

15. The method of claim 13 wherein the potassium source is in the form of a slurry or a brine and wherein the slurry or brine is mixed with the glaserite crystals in the potassium sulfate reactor.

16. The method of claim 13 wherein the sodium chloride crystallizer produces a concentrate that includes potassium and wherein the method includes directing at least a portion of the concentrate from the sodium chloride crystallizer to the glaserite reactor and mixing the concentrate with the first brine stream.

17. The method of claim 13 wherein in the process of producing sodium chloride crystals, the sodium chloride crystallizer forms a potassium liquor and wherein the potassium liquor is directed from the sodium chloride crystallizer to the glaserite reactor.

18. A method of producing potassium sulfate from a wastewater stream containing sodium and sulfate comprising: directing the wastewater stream to a membrane separation unit and producing a first reject stream and a first permeate stream; concentrating the first reject stream to form a first brine solution or a slurry; mixing the first brine solution or the slurry with a potassium liquor to form a mixture; crystallizing the mixture in a glaserite crystallizer and producing glaserite crystals; separating the glaserite crystals from the potassium liquor and directing the glaserite crystals to a potassium sulfate reactor; mixing a potassium source with the glaserite crystals to form potassium sulfate crystals; separating the potassium sulfate crystals; wherein the potassium source mixed with the glaserite crystals in the potassium sulfate reactor forms the potassium liquor that is mixed with the first brine stream or slurry in the glaserite crystallizer; directing the potassium liquor from the glaserite crystallizer to a nanofiltration unit and producing a second reject stream and a second permeate stream; recycling the second reject stream from the nanofiltration unit to the glaserite crystallizer; and directing the second permeate stream from the nanofiltration unit to a sodium chloride crystallizer and producing sodium chloride crystals.

19. The method of claim 18 wherein the first permeate stream is directed to a second sodium chloride crystallizer that forms sodium chloride crystals.

20. The method of claim 19 wherein the first permeate stream is subjected to a concentration process before reaching the second sodium chloride crystallizer.

21. A method of recovering potassium sulfate from wastewater produced in a coal-to-chemical or a coal-to-liquid process, the method comprising: converting coal-to-chemical or coal-to-liquid and in the course of converting coal-to-chemical or liquid producing the wastewater; concentrating the wastewater to form a brine that includes sodium and sulfate; directing the brine to a mirabilite crystallizer and forming mirabilite crystals and producing a mirabilite liquor; separating the mirabilite crystals from the mirabilite liquor; directing the mirabilite crystals to a glaserite reactor or glaserite crystallizer; mixing a potassium liquor with the mirabilite crystals; producing or forming glaserite crystals from the mirabilite crystals and the potassium liquor in a glaserite reactor or a glaserite crystallizer; separating the glaserite crystals from the potassium liquor; directing the glaserite crystals to a potassium sulfate reactor; mixing a potassium source with the glaserite crystals in the potassium sulfate reactor to form potassium sulfate crystals; separating the potassium sulfate crystals; and wherein the potassium source mixed with the glaserite crystals in the potassium sulfate reactor forms the potassium liquor that is mixed with the glaserite crystals in the glaserite reactor.

22. The method of claim 21 including filtering the mirabilite crystallizer liquor with a nanofiltration unit to produce a permeate and directing the permeate to a sodium chloride crystallizer; and wherein the glaserite crystals are formed in the glaserite crystallizer and the method includes directing the potassium liquor from the glaserite crystallizer to a second nanofiltration unit and producing a second reject stream and a second permeate stream; recycling the second reject stream from the second nanofiltration unit to the glaserite crystallizer; and directing the second permeate stream from the second nanofiltration unit to the sodium chloride crystallizer.

23. The method of claim 21 wherein the glaserite crystals are produced in the glaserite reactor and wherein the potassium liquor includes sodium chloride and the method includes reducing the concentration of sodium chloride in the potassium liquor by cycling the potassium liquor back and forth between the glaserite reactor and a sodium chloride crystallizer that forms sodium chloride crystals from the potassium liquor.

24. The method of claim 21 further including directing the mirabilite liquor to a nanofiltration unit and producing a permeate and directing the permeate to the sodium chloride crystallizer that forms sodium chloride crystallizers from the mirabilite liquor.

25. The method of claim 21 wherein the glaserite crystals are formed in the glaserite crystallizer and the method includes directing the potassium liquor from the glaserite crystallizer to a nanofiltration unit and producing a reject stream and a permeate stream; recycling the reject stream from the nanofiltration unit to the glaserite crystallizer; and directing the permeate stream to a sodium chloride crystallizer and producing sodium chloride crystals.

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