Hygroscopic cooling tower for waste water disposal

1. A method of waste water disposal, the method comprising:

contacting a hygroscopic working fluid with a heat exchanger having a heated process fluid, wherein the hygroscopic working fluid comprises a desiccant and water;

transferring thermal energy from the heated process fluid to the hygroscopic working fluid and flowing the hygroscopic working fluid from the heat exchanger to a fluid-air contactor having an air stream;

contacting the hygroscopic working fluid with the air stream of the fluid-air contactor;

transferring water from the hygroscopic working fluid to the air stream, collecting the resulting hygroscopic working fluid and circulating it to the process heat exchanger;

directing a controlled amount of the hygroscopic working fluid to form a mixture with a waste water having dissolved impurities in a makeup mix tank at a mass concentration of desiccant of at least about 5% in the mixture, to induce precipitation of the dissolved impurities in the makeup mix tank prior to transfer to a filter; and

filtering the precipitate from the mixture to form a filtrate and directing the filtrate to combine with the circulating hygroscopic working fluid.

2. The method of claim 1 , wherein the waste water comprises a reverse osmosis concentrate, a concentrated salt stream, a scrubbing liquor from an industrial process, a blowdown from a cooling tower, or a mixture thereof.

3. The method of claim 1 , wherein the waste water comprises a concentrated effluent from a water treatment system, a desalination system or a reverse osmosis system.

4. The method of claim 1 , wherein the mass concentration of desiccant in the makeup mix tank is at least about 15%.

5. The method of claim 1 , wherein the fluid-air contactor is a hygroscopic cooling tower.

6. The method of claim 1 , wherein the fluid-air contactor and air stream are configured to transfer an amount of water from the hygroscopic working fluid to the air stream about equal to an amount of waste water that is added to the hygroscopic working fluid.

7. The method of claim 1 , wherein the hygroscopic working fluid comprises an aqueous solution comprising at least one of sodium chloride (NaCl), calcium chloride (CaCl 2 ), magnesium chloride (MgCl 2 ), lithium chloride (LiCl), lithium bromide (LiBr), zinc chloride (ZnCl 2 ), sulfuric acid (H 2 SO 4 ), sodium hydroxide (NaOH), sodium sulfate (Na 2 SO 4 ), potassium chloride (KCl), calcium nitrate (Ca[NO 3 ]2), potassium carbonate (K 2 CO 3 ), ammonium nitrate (NH 4 NO 3 ), ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol and dipropylene glycol.

8. A hygroscopic cooling system, the system comprising:

a hygroscopic working fluid comprising a desiccant and water;

a heat exchanger to transfer thermal energy from a heated process fluid to the hygroscopic working fluid;

a fluid-air contactor having an air stream, wherein the fluid-air contactor and air-stream are configured to transfer water from the hygroscopic working fluid to the air stream;

wherein the heat exchanger and the fluid-air contactor are configured so the hygroscopic working fluid is circulated through the heat exchanger and the fluid-air contactor;

a settling chamber configured to receive waste water and a controlled amount of at least some of the circulated hygroscopic working fluid so that mass concentration of desiccant in the settling chamber is at least about 5%, wherein the settling chamber is at conditions which permit the waste water and the hygroscopic working fluid to mix and to induce precipitation of dissolved impurities from the resulting mixture; and

a filter unit configured to remove precipitated impurities from the settling chamber and direct the resulting filtrate to combine with the circulated hygroscopic working fluid.

9. The hygroscopic cooling system of claim 8 , wherein the waste water comprises a reverse osmosis concentrate, a concentrated salt stream, a scrubbing liquor from an industrial process, a blowdown from a cooling tower, or a mixture thereof.

10. The hygroscopic cooling system of claim 8 , wherein the waste water comprises a concentrated effluent from a water treatment system, a desalination system or a reverse osmosis system.

11. The hygroscopic cooling system of claim 8 , wherein the mass concentration of desiccant in the settling chamber is at least about 15%.

12. The hygroscopic cooling system of claim 8 , wherein the fluid-air contactor is a hygroscopic cooling tower.

13. The hygroscopic cooling system of claim 8 , wherein the fluid-air contactor and air stream are configured to transfer an amount of water from the hygroscopic working fluid to the air stream about equal to an amount of waste water that is added to the hygroscopic working fluid.

14. The hygroscopic cooling system of claim 8 , wherein the hygroscopic working fluid comprises an aqueous solution comprising at least one of sodium chloride (NaCl), calcium chloride (CaCl 2 ), magnesium chloride (MgCl 2 ), lithium chloride (LiCl), lithium bromide (LiBr), zinc chloride (ZnCl 2 ), sulfuric acid (H 2 SO 4 ), sodium hydroxide (NaOH), sodium sulfate (Na 2 SO 4 ), potassium chloride (KCl), calcium nitrate (Ca[NO 3 ]2), potassium carbonate (K 2 CO 3 ), ammonium nitrate (NH 4 NO 3 ), ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, and dipropylene glycol.

15. The hygroscopic cooling system of claim 8 , further comprising:

a reverse osmosis system which accepts untreated water and produces a treated water effluent and a reverse osmosis concentrate,

wherein the reverse osmosis concentrate is directed to the settling chamber via a conduit to provide the waste water.

16. The hygroscopic cooling system of claim 8 , further comprising:

a desalination system which accepts brackish water and produces a treated water effluent and a concentrated salt stream,

wherein the concentrated salt stream is directed to the settling chamber via a conduit to provide the waste water.

17. The hygroscopic cooling system of claim 8 , further comprising:

a second heat exchanger to transfer thermal energy from a second heated process fluid to the heated process fluid;

a second fluid-air contactor having a second air stream configured to transfer thermal energy, water, or a combination thereof, from the heated process fluid to the second air stream, wherein the second fluid-air contactor produces a blowdown stream which is collected and directed to the makeup mix tank via a conduit to provide the waste water; and

wherein the heated process fluid is a non-hygroscopic working fluid circulated between the second heat exchanger and the second fluid-air contactor.

18. The method of claim 1 , wherein the waste water has higher TDS than the hygroscopic working fluid.

19. The method of claim 1 , wherein the waste water provided to the makeup mix tank has a calcium content of about 718 or greater, a TDS of about 6652 or greater, or both.

20. The method of claim 1 , wherein the makeup mix tank is a settling chamber.