Multi-Stage Column Distillation (MSCD) Method for Osmotic Solute Recovery

• US 20090297431A1
• Filed: 06/07/2007
• Published: 12/03/2009
• Est. Priority Date: 06/08/2006
• Status: Active Grant

• Current Assignee: Yale University
• Original Assignee: Yale University
• Inventors: Menachem, Elimelech, McGinnis, Robert L.
• Granted Patent: US 8,246,791 B2
• Time in Patent Office: Days
• US Class Current: 423/580.1
• CPC Class Codes: B01D 3/146 Multiple effect distillation
• CPC Class Codes: C02F 1/445 by forward osmosis
• CPC Class Codes: Y02A 20/124 Water desalination
• CPC Class Codes: Y02A 20/131 Reverse-osmosis

Abstract

A method and apparatus for separating draw solution solutes and product solvent from a draw solution using a plurality of distillation columns. In one embodiment, the draw solution is used in a Forward Osmosis (FO) water desalination process. In this embodiment, the draw solution is directed to the plurality of distillation columns in parallel while the energy stream (heat) is directed to the plurality of distillation columns in series such that the efficiency of heat use is improved and in turn the cost of the heat is reduced.

Claims

1. An apparatus for separating draw solution solutes and product solvent from a draw solution, wherein the apparatus comprises:

a first distillation column comprising;

a first inlet coupled to a source of the draw solution for introducing the draw solution into a first end of the first distillation column;

a first heat transfer means coupled to the first distillation column at a second end, said first heat transfer means having an inlet coupled to a source of thermal energy and an outlet coupled to the first distillation column for introducing thermal energy to the first distillation column to cause at least a portion of the draw solution in the first distillation column to vaporize;

a first outlet for removing the vaporized portion of the draw solution from the first distillation column; and

at least a second distillation column comprising;

a first inlet coupled to the source of the draw solution for introducing the draw solution into a first end of the second distillation column;

a second heat transfer means coupled to the second distillation column at a second end, said second heat transfer means having an inlet coupled to the first outlet of the first distillation column for providing a source of thermal energy for the second distillation column and an outlet coupled to the second distillation column for introducing thermal energy to the second distillation column to cause at least a portion of the draw solution in the second distillation chamber to vaporize.

2. The apparatus as claimed in claim 1 wherein the second distillation column comprises:

a first outlet for removing the vaporized portion of the draw solution from the second distillation column solution.

3. The apparatus as claimed in claim 1 wherein the second distillation column comprises:

an outlet for removing product solvent from the second distillation chamber.

4. The apparatus as claimed in claim 2 comprising:

at least a third distillation column comprising;

a first inlet coupled to the source of the draw solution for introducing the draw solution into a first end of the third distillation column;

a third heat transfer means coupled to the third distillation column at a second end, said third heat transfer means having an inlet coupled to the first outlet of the second distillation column for providing a source of thermal energy for the third distillation column and an outlet coupled to the third distillation column for introducing thermal energy to the third distillation column to cause at least a portion of the draw solution in the third distillation chamber to vaporize.

5. The apparatus as claimed in claim 1 wherein the source of thermal energy supplies heat at a temperature of at least about 50°

C.

6. The apparatus as claimed in claim 5 wherein the source of thermal energy supplies heat at a temperature from about 90°

C. to about 250°

C.

7. A method for separating draw solution solutes and product solvent from a draw solution using a plurality of distillation columns, wherein the method comprises the steps of:

introducing draw solution to each of at least a first distillation column and at least a second distillation column;

applying thermal energy from a source of thermal energy to a first heat transfer means of the first distillation column to vaporize at least a portion of the draw solution in the first distillation column;

directing the vaporized portion of the draw solution from the first distillation column to a second heat transfer means of the second distillation column such that the vaporized portion of the draw solution from the first distillation column acts as a source of thermal energy for the second distillation column to vaporize at least a portion of the draw solution in the second distillation column;

whereby the draw solution solutes and product solvent contained in the draw solution in the at least first and second distillation columns are separated.

8. The method as claimed in claim 7 wherein the draw solution is used in a forward osmotic desalination process.

9. The method as claimed in claim 7 wherein the source of thermal energy to the at least first distillation column is steam.

10. The method as claimed in claim 7 wherein the draw solution is introduced to the at least first and second distillation columns at a concentration of at least about 0.5 molar.

11. The method as claimed in claim 8 wherein the draw solution is introduced to the at least first and second distillation columns at a concentration from about 0.5 molar to about 6.0 molar.

12. The method as claimed in claim 7 wherein the draw solution comprises an aqueous solution of ammonium salts formed from a mixture of ammonia and carbon dioxide.

13. The method as claimed in claim 7 wherein the draw solution comprises ethanol.

14. The method as claimed in claim 7 wherein the product solvent is water.

15. The method as claimed in claim 12 wherein the product solvent contains less than 1 ppm ammonia and carbon dioxide.

16. The method as claimed in claim 7 wherein the method comprises:

introducing draw solution to at least a third distillation column;

directing the vaporized portion of the draw solution from the second distillation column to a third heat transfer means of the third distillation column such that the vaporized portion of the draw solution from the second distillation chamber acts as a source of thermal energy for the third distillation chamber to vaporize at least a portion of the draw solution in the third distillation column;

whereby the draw solution solutes and product solvent contained in the draw solution in the third distillation column is separated.

17. The method as claimed in claim 7, wherein the draw solution is parallely introduced into each of at least the first distillation column and the at least the second distillation chamber.

18. The method as claimed in claim 15, wherein the draw solution is parallely introduced into to each of at least the first distillation column, the at least the second distillation column and the at least the third distillation column.

19. Desalinated water produced according to the process of claim 7.

20. Purified water produced according to the process of claim 7.