ANTISOLVENT PROCESS FOR TREATING LIQUIDS THAT INCLUDE HIGH TOTAL DISSOLVED SOLIDS

• US 20130140234A1
• Filed: 12/06/2012
• Published: 06/06/2013
• Est. Priority Date: 12/06/2011
• Status: Active Grant

• Current Assignee: Drake Water Technologies, Inc.
• Original Assignee: Drake Water Technologies, Inc.
• Inventors: Drake, Ronald N.
• Granted Patent: US 9,416,033 B2
• Time in Patent Office: Days
• US Class Current: 210/639
• CPC Class Codes: C02F 1/02 by heating methods of steam generation F22B; preheating boiler feed-water or accumulating preheated boiler feed-water F22D
• CPC Class Codes: C02F 1/16 using waste heat from other processes
• CPC Class Codes: C02F 1/38 by centrifugal separation
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/5272 using specific organic precipitants
• CPC Class Codes: C02F 2001/007 Processes including a sedimentation step
• CPC Class Codes: C02F 2001/5218 Crystallization
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage

Abstract

The present invention provides a low energy alternative to conventional thermal/evaporation processes for “zero liquid discharge” treatment of strong saline brines. The products of the process include a salt-free liquid and solid salt. In particular, an antisolvent can be mixed with liquids containing high total dissolved solids. The mixture can be chilled, whereby solid salt is precipitated and separated from the mixture at near ambient temperature leaving a mixed liquor. The antisolvent can be selected from a class of organic compounds that form solutions with salt brines that exhibit a critical solution temperature lower than a critical solution temperature of the salt brines alone. The mixed liquor can be heated to a temperature above its lower critical solution temperature to produce an antisolvent liquid phase for recycle to the process. Finally, a reduced salinity aqueous phase can be polished by reverse osmosis or other conventional technology to produce clean water for discharge or beneficial use.

Claims

1. A method for treating liquids containing high total dissolved solids, to produce substantially salt-free liquid and solid salt, said process comprising:

mixing a first high total dissolved solids (TDS) liquid with an antisolvent to form a mixture, the mixture having a lower critical solution temperature, the mixture existing at a first temperature below the lower critical solution temperature thus resulting in precipitation of salt from the mixture to form a salt slurry;

separating the salt slurry into a damp salt cake and a mixed liquor;

heating the damp salt cake to produce dry salt and a mixed vapor;

heating the mixed liquor to raise a temperature of the mixed liquor above a lower critical solution temperature of the mixed liquor thus producing an antisolvent phase and an aqueous phase; and

returning the antisolvent phase to the mixing step.

2. The method of claim 1, further comprising polishing the aqueous phase to remove residual dissolved solids thus producing a clean liquid and a polisher reject stream that is returned to the mixing operation.

3. The method of claim 2, wherein the polishing includes reverse osmosis.

4. The method of claim 3, wherein heat is removed from the aqueous phase, via a cooler, before the polishing.

5. The method of claim 1, wherein heating the mixed liquor includes indirectly transferring heat from the antisolvent phase to the mixed liquor.

6. The method of claim 5, wherein heating the mixed liquor further involves direct heating of the mixed liquor.

7. The method of claim 6, wherein heating the mixed liquor further involves bringing the mixed vapor into contact with the mixed liquor.

8. The method of claim 7, wherein heating the mixed liquor includes transferring heat from the mixed vapor to the mixed liquor.

9. The method of claim 1, further comprising chilling the mixture to a temperature below the lower critical solution temperature.

10. The method of claim 1, wherein the mixed vapor comprises a mixture of aqueous vapor and antisolvent vapor.

11. A system for treating a high total dissolved solids liquid, the system comprising:

a temperature-reduction vessel that receives a high TDS liquid and an antisolvent such that a mixture is formed inside the temperature-reduction vessel at a temperature below a critical solution temperature of the mixture, thereby causing precipitation of salt and production of a salt slurry;

a separator receiving the salt slurry and separating the salt slurry into a mixed liquor and a salt cake;

a heating vessel receiving the salt cake and applying heat to the salt cake to produce dry salt and a mixed vapor;

a phase separator receiving a recuperated mixed liquor, a temperature of the recuperated mixed liquor in the phase separator being greater than a lower critical solution temperature of the recuperated mixed liquor, and thus causing the recuperated mixed liquor to separate into an antisolvent phase and an aqueous phase;

a recuperator receiving the antisolvent phase and the mixed liquor and indirectly transferring heat from the antisolvent phase to the mixed liquor thus turning the mixed liquor into the recuperated mixed liquor; and

a heater that applies heat to the recuperated mixed liquor such that the temperature of the recuperated mixed liquor in the phase separator is greater than the lower critical solution temperature of the recuperated mixed liquor.

12. The system of claim 11, further comprising a polisher that polishes the aqueous phase producing clean water and returning any solution having a concentration of salt to the temperature-reduction vessel.

13. The system of claim 12, wherein the antisolvent is at a lower temperature than the solution having a concentration of salt therein.

14. The system of claim 12, wherein the mixed vapor is added to the phase separator and thereby transfers heat to the recuperated mixed liquor.

15. The system of claim 12, wherein the antisolvent is a liquid.

16. The system of claim 12, wherein the separator is a settling tank.

17. The system of claim 12, wherein the separator is a clarifier.

18. The system of claim 12, wherein the separator is a hydrocyclone.