WATER DESALINATION PLANT AND SYSTEM FOR THE PRODUCTION OF PURE WATER AND SALT

• US 20100163471A1
• Filed: 12/30/2008
• Published: 07/01/2010
• Est. Priority Date: 12/30/2008
• Status: Abandoned Application

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Weimer, Lanny D., Herbert, John, Elyanow, Irving, Vora, Nishith, Solomon, Robert Lee
• Application Number:
  US12/345,856
• Publication Number:
  US 20100163471A1
• Time in Patent Office: Days
• US Class Current: 210/176
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/06 Specific process operations in the permeate stream
• CPC Class Codes: B01D 2311/08 Specific process operations in the concentrate stream
• CPC Class Codes: B01D 2311/10 Temperature control
• CPC Class Codes: B01D 2311/12 Addition of chemical agents
• CPC Class Codes: B01D 2311/26 Further operations combined with membrane separation processes
• CPC Class Codes: B01D 2311/2649 Filtration
• CPC Class Codes: B01D 2311/2673 Evaporation
• CPC Class Codes: B01D 2311/2676 Centrifugal separation
• CPC Class Codes: B01D 61/026 comprising multiple reverse osmosis steps
• CPC Class Codes: B01D 61/029 Multistep processes comprising different kinds of membrane processes selected from reverse osmosis, hyperfiltration or nanofiltration
• CPC Class Codes: B01D 61/04 Feed pretreatment
• CPC Class Codes: C02F 1/001 Processes for the treatment of water whereby the filtration technique is of importance C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00
• CPC Class Codes: C02F 1/041 by means of vapour compression
• CPC Class Codes: C02F 1/08 Thin film evaporation
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: 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
• CPC Class Codes: C02F 11/121 by mechanical de-watering
• CPC Class Codes: C02F 2101/101 Sulfur compounds
• CPC Class Codes: C02F 2101/108 : Boron compounds
• CPC Class Codes: C02F 2103/08 : Seawater, e.g. for desalination
• CPC Class Codes: C02F 5/08 : Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
• CPC Class Codes: C02F 9/00 : Multistage treatment of water, waste water or sewage
• CPC Class Codes: Y02A 20/124 : Water desalination
• CPC Class Codes: Y02A 20/131 : Reverse-osmosis

Abstract

The present invention discloses a desalination plant that operates with a sea water or brackish water feed and produces a concentrated and selectively improved salt reject stream and a pure water permeate stream from a first treatment section that is arranged to produce primarily water at high recovery using membrane desalination processes. The reject stream from the first treatment line has a component distribution that is substantially reduced in native di- and polyvalent scaling ions, essentially depleted of sulfate, has substantially higher total dissolved solids than a traditional sea water reverse osmosis reject, yet is suitable for thermal treatment processes. The system may be enhanced by monovalent salt components. The unit may be integrated with a second treatment section, in which the first reject stream is further concentrated, purified, and processed to produce a high purity salt product.

Claims

1. A desalination plant for treating a sea water or brackish water feed wherein the desalination plant comprises:

a. a first treatment section to effectively remove scaling species and

b. a reverse osmosis section that operates at high recovery to produce a purified permeate stream and a selectively NaCl salt-enriched reject stream as a saline output.

2. The desalination plant of claim 1 further comprising:

a second treatment section configured to concentrate and refine the reject stream, wherein the second treatment section concentrates the reject stream by a thermal or hybrid section and produces pure water and a purified salt product.

3. The desalination plant of claim 1 wherein the reject stream is concentrated to above about 85,000 ppm total dissolved solids.

4. The desalination plant of claim 1 wherein the desalination plant has an intake stream of saline feed that is less than two times the size of the permeate stream produced from the reverse osmosis section.

5. The desalination plant of claim 1 wherein the first treatment section produces the purified permeate stream via membrane pressure filtration processes at recovery above about 55% and removes a preponderance of species that contaminate salt production.

6. The desalination plant of claim 2 wherein the plant operates above about 62% water recovery.

7. The desalination plant of claim 2 wherein overall recovery is above from about 65% to about 70%

8. The desalination plant of claim 2 wherein the second treatment section:

a. further concentrates the reject stream, and

b. chemically precipitates unwanted impurities from the reject stream and forms a refined concentrate stream, such that salt may be continuously recovered by crystallization at purity above about 99% as a high purity salt product.

9. The desalination plant of claim 2 wherein the second treatment section further comprises a crystallizer for forming a salt solid or slurry from said refined concentrated salt stream.

10. The desalination plant of claim 2 wherein the second treatment section removes residual impurities by chemical precipitation to produce a refined salt concentrate, and pure salt is separated at a temperature or further concentration effective to crystallize salt from a saturated solution.

11. The desalination plant of claim 9 wherein periodic or continuous blowdown from the crystallizer is used to limit the impurities from the crystallized product.

12. The desalination plant of claim 2 wherein the refined salt concentrate from the reject stream forms a moist salt or slurry that is centrifugally extracted from a crystallizer seed loop and a crystal seed stream is returned from a centrifuge to a crystallizer liquor to drive crystallization for continuous take-off of a concentrated salt product.

13. The desalination plant of claim 5 wherein the pressure membrane filtration processes include nanofiltration softening that effectively removes substantially all sulfates.

14. The desalination plant of claim 1 wherein the first treatment section comprises a multistage nanofiltration section where bivalent ions are substantially removed from nanofiltration permeate and operating a recovery level above about 65% to form an monovalent salt enhanced permeate stream for concentration.

15. The desalination plant of claim 2 wherein the second treatment section comprises a mechanical vapor compressor that produces additional pure water and further concentrates the selectively salt-enriched reject stream.

16. A desalination plant for treating a seawater or brackish feed comprised of a nanofiltration unit and a reverse osmosis unit, the nanofiltration unit arranged to form a nanofiltration permeate substantially diminished in scaling and fouling components and the permeate is fed to the reverse osmosis unit.

17. The desalination plant of claim 16 wherein the reverse osmosis unit is operated at high recovery to form a purified water permeate stream and a non-scaling salt reject stream concentrated above about 85,000 ppm TDS.

18. The desalination plant of claim 16 wherein the nanofiltration permeate is fed to the reverse osmosis unit at an elevated pH to form a purified water permeate stream having less than about 0.5 ppm boron.

19. The desalination plant of claim 18 wherein the pH of the nanofiltration permeate is raised before reverse osmosis and operates at a recovery of about 70% while producing a high recovery purified water permeate stream.

20. The desalination plant of claim 18, further wherein the nanofiltration allows scaling control when small dosages of scale inhibitors or anti-scalant is added.

21. The desalination plant of claim 18, wherein the pH elevation is from about 8.3 to about 10.5.

22. A water desalination system comprising:

a. an intake section of a size to supply and pretreat a defined flow of a seawater or brackish feed containing sulfate for a system having a pure water output capacity,

b. a nanofiltration process configured to filter the defined flow to produce nanofiltration permeate at recovery above from about 70% to about 80% and sulfate concentration is reduced at least about 90%; and

c. a reverse osmosis process which receives the nanofiltration permeate as a feed and operates to produce a reverse osmosis permeate stream at a recovery above from about 70% to about 80% and a concentrated reverse osmosis reject stream suitable for enhanced commercial NaCl production, whereby the reverse osmosis permeate amounts to from about 49% to about 64% of the defined flow of the feed and the intake section is sized less than twice the pure water output capacity.

23. The water desalination system of claim 22 wherein the reverse osmosis reject stream is provided to a thermal concentrator to concentrate the stream to saturation and crystallization, and the thermal concentrator recovers one or more additional streams of pure water such that between from about 75% to about 95% of the nanofiltration permeate is recovered as pure water.

24. The water desalination system of claim 22 wherein the nanofiltration removes a substantial portion of bivalent metal ions present in the feed such that the reverse osmosis reject is non-scaling in the concentrator and salt is more economically purified by chemical precipitation of contaminants prior to crystallization.

25. The desalination system claim 22 wherein the system is comprised of multiple nanofiltration stages to achieve recovery above about 70%, the permeate of the nanofiltration being fed to a multi-stage reverse osmosis to achieve high water recovery while producing a selectively salt-enriched reject having a TDS of about 100,000 and suitable for salt manufacture.

26. The desalination system of claim 23 wherein a second treatment section purifies and then crystallizes salt, maintaining low impurities in the crystallizer by periodic purge to remove interfering contaminants not removed by nanofiltration.