Electrodialysis stack

Patent metadata

Field	Value
Publication number	US-11484839-B2
Application number	US-201716609406-A
Country	US
Kind code	B2
Filing date	May 4, 2017
Priority date	May 4, 2017
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

The present disclosure provides an electrodialysis stack that may be used for the treatment of an electrically conductive solution. The stack includes two electrodes (at least one is a recessed electrode), a plurality of ion-transport membranes and stack spacers. The membranes and spacers are arranged between the electrodes to define electrodialysis cell pairs. The stack includes an electrically insulated zone that extends substantially from a distribution manifold past the recessed edge of the electrode and substantially from the recessed electrode to the opposite electrode for a distance that is about 8% to 100% of the total distance between the electrodes. The overlap distance that the electrically insulated zone extends past the recessed edge of the electrode is calculated as: distance in cm=(0.062 cm −1 )*(exp(−60/total cp)*(area in cm 2 of the manifold ducts of the concentrated stream at the recessed edge) +/−10%.

First claim

What is claimed is:

1. An electrodialysis stack for treatment of an electrically conductive solution, the electrodialysis stack comprising:
two electrodes, ion-exchange membranes, and electrodialysis stack spacers, the membranes and spacers being arranged between the electrodes to define a total number of electrodialysis cell pairs (total cp) that is at least 10 and up to 2000, the electrodialysis cells in the electrodialysis cell pairs providing an electrically conductive fluid connection between the electrodes during electrodialysis;
the membranes and spacers defining apertures therein that, in combination, define a distribution manifold for the electrically conductive solution when the membranes and spacers are arranged to form the electrodialysis cells, wherein at least one of the two electrodes is a recessed electrode has an edge recessed from the distribution manifold, and wherein the distribution manifold defines a duct area for a concentrated stream; and
an electrically insulated zone that overlaps with the electrically conductive fluid connection between the electrodes, the electrically insulated zone:
(i) extending substantially from a distribution manifold past the recessed edge of the electrode for an overlap distance in cm that is about equal to:
(0.062 cm −1 )*(exp(−60/total cp)*(area in cm 2 of the manifold ducts of the concentrated stream at the recessed edge); and

(ii) extending substantially from the recessed electrode to the other electrode for a distance that is about 8% to 100% of the total distance between the two electrodes.

2. The electrodialysis stack according to claim 1 , wherein the electrically insulated zone extends 100% of the distance between the recessed electrode and the other electrode.

3. The electrodialysis stack according to claim 1 , wherein the electrically insulated zone is defined by electrically insulating masks.

4. The electrodialysis stack according to claim 3 , wherein one or more of the electrically insulating masks comprise:
(a) a plastic sheet in an electrodialysis cell;
(b) a plastic sheet between two adjacent electrodialysis cells;
(c) an ion-transport resistant portion of a cation-exchange membrane;
(d) an ion-transport resistant portion of an anion-exchange membrane;
(e) a portion of a spacer that reduces the area on adjacent membranes available for the electrically conductive fluid connection; or
(f) any combination thereof.

5. The electrodialysis stack according to claim 4 , wherein the plastic sheet in an electrodialysis cell is positioned: between a membrane and a spacer, or between a membrane and an adjacent cell.

6. The electrodialysis stack according to claim 4 , wherein the electrically insulated zone is defined by a plurality of plastic sheets that are positioned: between cation-exchange membranes and adjacent spacers; between anion-exchange membranes and adjacent spacers; between cation-exchange membranes and anion-exchange membranes; or any combination thereof.

7. The electrodialysis stack according to claim 4 , wherein the plastic sheets have an areal resistance greater than 100 ohm·cm 2 and a thickness less than 0.05 mm.

8. The electrodialysis stack according to claim 4 , wherein the electrically insulated zone is defined by a plurality of ion-transport resistant portions of the cation-exchange membranes, the anion-exchange membranes, or both.

9. The electrodialysis stack according to claim 8 , wherein the ion-transport resistant portion of the cation-exchange membrane comprises substantially equal molar amounts of both fixed cationic and fixed anionic charges, or comprises substantially no fixed charges.

10. The electrodialysis stack according to claim 8 , wherein the ion-transport resistant portion of the anion-exchange membrane comprises substantially equal molar amounts of both fixed cationic and fixed anionic charges, or comprises substantially no fixed charges.

11. The electrodialysis stack according to claim 4 , wherein the spacer comprises electrically resistant structures that span the spacer to contact the adjacent membranes to reduce the area on the adjacent membranes available for the electrically conductive fluid connection.

12. The electrodialysis stack according to claim 11 , wherein the electrically resistant structures extend substantially along the direction of fluid flow.

13. The electrodialysis stack according to claim 1 , wherein the other electrode is a recessed electrode that has an edge recessed from the distribution manifold, and the electrically insulated zone:
(i) extends substantially from the distribution manifold past the recessed edge of the other electrode for an overlap distance in cm that is about equal to:
(0.062 cm −1 )*(exp(−60/total cp)*(area in cm 2 of the manifold ducts of the concentrated stream at the recessed edge); and

(ii) extends substantially from the other recessed electrode to the first recessed electrode for a distance that is about 8% to 100% of the total distance between the two electrodes.

14. The electrodialysis stack according to claim 1 , wherein the membranes and spacers define a second distribution manifold and the recessed electrode has a second edge recessed from the second distribution manifold, and the electrodialysis stack includes a second electrically insulated zone that:
(i) extends substantially from the second distribution manifold past the second recessed edge of the recessed electrode for an overlap distance in cm that is about equal to:
(0.062 cm −1 )*(exp(−60/total cp)*(area in cm 2 of the manifold ducts of the concentrated stream at the second recessed edge); and

(ii) extends substantially from the recessed electrode to the other electrode for a distance that is about 8% to 100% of the total distance between the two electrodes.

15. The electrodialysis stack according to claim 1 , wherein both electrodes are recessed electrodes that have two opposite recessed edges and the stack includes four electrically insulated zones that (i) overlap with the recessed edges of their respective electrodes, and (ii) extend substantially from their respective electrodes to the opposite electrodes for a distance that is from about 8% to 100% of the total distance between the electrodes; wherein each overlap distance in cm is independently calculated based on the equation:
(0.062 cm −1 )*(exp(−60/total cp)*(area in cm 2 of the manifold ducts of the concentrated stream at the recessed edge).

16. The electrodialysis stack according to claim 1 , wherein the electrically insulated zone extends less than 100% of the distance between the recessed electrode and the other electrode, and the electrodialysis stack further comprises an additional electrically insulated zone that does not extend past the recessed edge of the recessed electrode.

Assignees

• Bl Technologies Inc

Inventors

• Barber John H
• Gutowski Wojciech
• Zheng Yongchang
• Macdonald Russell James

Classifications

• B01D61/50 Primary

  Stacks of the plate-and-frame type · CPC title

• B01D63/085

  specially adapted for two fluids in mass exchange flow · CPC title

• B01D2325/42

  Ion-exchange membranes · CPC title

• B01D2313/14

  Specific spacers · CPC title

• Y02A20/124

  Water desalination · CPC title