Spiral-wound electrodialysis module

Patent metadata

Field	Value
Publication number	US-10926224-B2
Application number	US-201816161623-A
Country	US
Kind code	B2
Filing date	Oct 16, 2018
Priority date	Oct 16, 2017
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A spiral-wound electrodialysis module includes an inner electrode positioned about a central axis and an outer electrode surrounding the inner electrode. Ion exchange membranes are arranged in a stack, and each membrane extends in a spiral outward from an inner position proximate the inner electrode to an outer position proximate the outer electrode. The spirals expand outward at a greater-than-linear rate as a function of angle along a length of the spiral from the inner positions to the outer positions.

First claim

What is claimed is:

1. A spiral-wound electrodialysis module, comprising:
an inner electrode positioned about a central axis;
an outer electrode surrounding the inner electrode; and
a plurality of ion exchange membranes arranged in a stack, each membrane extending outwardly in a spiral, wherein each spiral extends along an increasing radius, measured from the central axis, from an inner radius proximate the inner electrode to an outer radius proximate the outer electrode, and wherein the radius of each spiral increases at a greater-than-linear rate as a function of an increase of a local spiral angle, β, measured about the central axis along a length of the spiral from a starting angular position at the inner radius toward a final angular position at the outer radius.

2. The spiral-wound electrodialysis module of claim 1 , wherein the spiral has a shape that substantially matches the following function:

r
⁡

(
β
)

=

r
0

1
-

β
⁡

(

1
-
CR

β
f

)

,

where r(β) represents local spiral radius as a function of the angle, β; r 0 represents a radius of the inner electrode; CR represents concentration ratio; and β f represents angle at an outer end of the spiral.

3. The spiral-wound electrodialysis module of claim 1 , wherein the spirals are shaped so as to generate an applied current density that is in a range from 40% of a local limiting current density to the local limiting current density at each location in the stack.

4. The spiral-wound electrodialysis module of claim 1 , wherein the spirals are shaped so as to generate an applied current density that is in a range from 60% of a local limiting current density to the local limiting current density at each location in the stack.

5. The spiral-wound electrodialysis module of claim 1 , wherein the spirals are shaped so as to generate an applied current density that is in a range from 80% of a local limiting current density to the local limiting current density at each location in the stack.

6. The spiral-wound electrodialysis module of claim 1 , wherein the ion exchange membranes comprise a plurality of cation exchange membranes and a plurality of anion exchange membranes, wherein the cation exchange membranes alternate in sequence with the anion exchange membranes.

7. The spiral-wound electrodialysis module of claim 6 , wherein channels configured for fluid flow are defined between adjacent membranes, wherein the channels include diluate channels and concentrate channels that alternate in sequence.

8. The spiral-wound electrodialysis module of claim 7 , including at least one fluid pump configured to pump a diluate stream to flow from the inner electrode to the outer electrode along a spiral pathway.

9. The spiral-wound electrodialysis module of claim 1 , wherein the spirals can be characterized by outward expansion at a greater-than-linear rate as a function of angle, β, along a length of the spiral from the inner positions to the outer positions.

10. The spiral-wound electrodialysis module of claim 1 , wherein the spirals expand over less than five revolutions from the inner to the outer positions.

11. A method for performing electrodialysis using a spiral-wound electrodialysis module, the method comprising:
flowing a feed liquid from a central channel through an inner electrode positioned about a central axis to a plurality of channels, including alternating diluate channels and concentrate channels, defined between ion exchange membranes arranged in a stack, wherein each membrane extends outwardly in a spiral, wherein each spiral extends along an increasing radius, measured from the central axis, from an inner radius proximate the inner electrode to an outer radius proximate an outer electrode, and wherein the radius of each spiral increases at a greater-than-linear rate as a function of an increase of a local spiral angle, β, measured about the central axis along a length of the spiral from a starting angular position at the inner radius toward a final angular position at the outer radius;
applying a voltage potential across the inner and outer electrodes;
drawing ions via the charges of the electrodes to selectively flow through the ion exchange membranes from the diluate channels into the concentrate channels;
extracting a concentrate solution from the concentrate channels; and
extracting a diluate liquid from the diluate channels, wherein the concentrate channel has a greater salinity than the diluate channel.

12. The method of claim 11 , wherein the spiral has a shape that substantially matches the following function:

r
⁡

(
β
)

=

r
0

1
-

β
⁡

(

1
-
CR

β
f

)

,

where r(β) represents local spiral radius as a function of the angle, β; r 0 represents a radius of the inner electrode; CR represents concentration ratio; and β f represents angle at an outer end of the spiral.

13. The method of claim 11 , wherein the electrodes generate an applied current density that is in a range from 40% of a local limiting current density to the local limiting current density at each location in the stack.

14. The method of claim 11 , wherein the electrodes generate an applied current density that is in a range from 60% of a local limiting current density to the local limiting current density at each location in the stack.

15. The method of claim 11 , wherein the electrodes generate an applied current density that is in a range from 80% of a local limiting current density to the local limiting current density at each location in the stack.

16. The method of claim 11 , wherein the ion exchange membranes comprise

Assignees

• Massachusetts Inst Technology

Inventors

• Winter Amos G
• Wright Natasha Catherine

Classifications

• B01D63/101

  Spiral winding · CPC title

• B01D61/463 Primary

  comprising the membrane sequence AC or CA, where C is a cation exchange membrane · CPC title

• C02F2103/06

  Contaminated groundwater or leachate · CPC title

• B01D2313/345

  Electrodes · CPC title

• B01D61/44

  Ion-selective electrodialysis · CPC title