Osmotic desalination methods and associated systems

Patent metadata

Field	Value
Publication number	US-10518221-B2
Application number	US-201615747907-A
Country	US
Kind code	B2
Filing date	Jul 29, 2016
Priority date	Jul 29, 2015
Publication date	Dec 31, 2019
Grant date	Dec 31, 2019

Abstract

Provided herein are osmotic desalination methods and associated systems. According to certain embodiments, multiple osmotic membranes may be used to perform a series of osmosis steps, such that an output stream having a relatively high water purity—compared to a water purity of an aqueous feed stream—is produced. In some embodiments, multiple draw streams can be used to produce aqueous product streams having sequentially higher purities of water. Certain embodiments are related to osmotic desalination systems and methods in which forward osmosis is used to produce a first product stream having a relatively high water purity relative to an aqueous feed stream, and reverse osmosis is used to perform a second step (and/or additional steps) on the first product stream. In some embodiments, multiple reverse osmosis steps can be used in series to perform a net desalination process.

First claim

What is claimed is:

1. A method, comprising:
transporting an aqueous feed stream containing a suspended and/or emulsified immiscible phase and solubilized ions at a concentration of at least about 60,000 ppm across a first side of a first osmotic membrane;
transporting a first draw inlet stream across a second side of the first osmotic membrane, the first draw inlet stream having a higher osmotic pressure than an osmotic pressure of the aqueous feed stream such that water is transported from the aqueous feed stream through the first osmotic membrane to the first draw inlet stream to produce a first draw product stream having a lower osmotic pressure than the first draw inlet stream and a concentrated aqueous stream having a higher concentration of solubilized ions than the aqueous feed stream;
directing the transport of the aqueous feed stream across the first osmotic membrane and/or the first draw inlet stream across the first osmotic membrane such that the transmembrane net driving force at the entrance of the aqueous feed stream to the first osmotic membrane and the transmembrane net driving force at the entrance of the first draw inlet stream to the first osmotic membrane are within about 10% of each other;
transporting at least a portion of the first draw product stream from the second side of the first osmotic membrane across a first side of a second osmotic membrane;
transporting a second draw inlet stream across a second side of the second osmotic membrane;
applying a hydraulic pressure to the first side of the second osmotic membrane such that water is transported from the first draw product stream through the second osmotic membrane to the second draw inlet stream to produce a second draw product stream having a lower osmotic pressure than the second draw inlet stream and a second concentrated aqueous stream having a higher osmotic pressure than the first draw product stream; and
directing the transport of the first draw product stream across the second osmotic membrane and/or the second draw inlet stream across the second osmotic membrane such that the transmembrane net driving force at the entrance of the first draw product stream to the second osmotic membrane and the transmembrane net driving force at the entrance of the second draw inlet stream across the second osmotic membrane are within about 10% of the each other.

2. The method of claim 1 , wherein, over at least about 90% of a facial area of the first osmotic membrane, a transmembrane net driving force across the first osmotic membrane is uniform to within about 10%.

3. The method of claim 1 , wherein, at at least one location on the first osmotic membrane, a difference between an osmotic pressure on the first side of the first osmotic membrane and an osmotic pressure on the second side of the first osmotic membrane is less than about 45 bar.

4. The method of claim 1 , wherein the aqueous feed stream and the first draw inlet stream are transported across the first osmotic membrane in a counter-current configuration.

5. The method of claim 1 , wherein the aqueous feed stream comprises Nat, Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Cl − , carbonate anions, bicarbonate anions, sulfate anions, bisulfate anions, and/or dissolved silica.

6. The method of claim 1 , wherein the first draw inlet stream comprises Nat, Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and/or Cl − .

7. A method, comprising:
transporting an aqueous feed stream across a first side of an osmotic membrane;
transporting a draw inlet stream across a second side of the osmotic membrane such that water is transported from the aqueous feed stream through the osmotic membrane to the draw inlet stream to produce a draw product stream having a lower osmotic pressure than the draw inlet stream and a concentrated aqueous stream having a higher osmotic pressure than the aqueous feed stream;
wherein the osmotic membrane is operated such that:

m

D
,
i

m

F
,
i

=

C
1

⁢

π

F
,
i

-

(

P
F

-

P
D

)

π

D
,
i

+

(

P
F

-

P
D

)

wherein P F is a hydraulic pressure at an inlet of the aqueous feed stream to the osmotic membrane; m F,i is a mass flow rate of the aqueous feed stream at the inlet of the aqueous feed stream to the osmotic membrane; π F,i is an osmotic pressure of the aqueous feed stream at the inlet of the aqueous feed stream to the osmotic membrane; P D is a hydraulic pressure at an inlet of the draw inlet stream to the osmotic membrane; m D,i is a mass flow rate of the draw inlet stream at the inlet of the draw inlet stream to the osmotic membrane; π D,i is an osmotic pressure of the draw inlet stream at the inlet of the draw inlet stream to the osmotic membrane; and C 1 is from about 0.8 to about 1.2.

8. The method of claim 7 , wherein the aqueous feed stream contains a suspended and/or emulsified immiscible phase and solubilized ions at a concentration of at least about 60,000 ppm.

9. The method of claim 7 , wherein the concentrated aqueous stream has a higher concentration of solubilized ions than the aqueous feed stream.

10. The method of claim 7 , wherein the draw inlet stream has a higher osmotic pressure than an osmotic pressure of the aqueous feed stream.

Assignees

• Gradiant Corp

Inventors

• Choong Looh Tchuin
• Govindan Prakash Narayan
• St John Maximus G
• Lam Steven
• Andrews Jonn-Ross
• Chehayeb Karim M

Classifications

• C02F1/44

  by dialysis, osmosis or reverse osmosis {(general membrane separation processes B01D61/00, membrane modules B01D63/00, electrodialysis C02F1/4693, combination of membrane modules and bioreactors C02F3/1268)} · CPC title

• Y02A20/131

  Reverse-osmosis · CPC title

• C02F2301/08

  Multistage treatments, e.g. repetition of the same process step under different conditions · CPC title

• C02F1/441

  by reverse osmosis · CPC title

• B01D2311/14

  Pressure control · CPC title