Electrodialytic water splitting process for gaseous products

• US 4,592,817 A
• Filed: 12/03/1984
• Issued: 06/03/1986
• Est. Priority Date: 12/03/1984
• Status: Expired due to Fees

• Current Assignee: The Graver Company (Berkshire Hathaway Incorporated)
• Original Assignee: Allied Corp. (Honeywell International Inc.)
• Inventors: Mani, Krishnamurthy N., Chlanda, Frederick P.
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Boggs, Jr., B. J.
• Application Number:
  US06/676,609
• Time in Patent Office: 547 Days
• Field of Search: 204/182.4, 204/301
• US Class Current: 204/534
• CPC Class Codes: B01D 53/501 by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• CPC Class Codes: B01D 61/445 with bipolar membranes; Water splitting
• CPC Class Codes: C01D 1/04 Hydroxides

Abstract

The present invention provides an improved electrodialytic water splitting process that may be operated in two- or three-compartment cells to recover valuable metal or ammonium values from materials comprising a salt of a first acid while avoiding formation of gas bubbles in the two- or three-compartment electrodialytic water splitting cells. The process comprises contacting a material comprising a salt of a first acid e.g. Na₂ SO₃, Na₂ CO₃ /NaHCO₃, wherein the first acid is capable of generating a gas upon acidification of the salt of the first acid with a hydrogen ion-enriched aqueous solution comprising a second acid, e.g. Na₂ SO₄ /H₂ SO₄ which is generated and withdrawn from a two- or three-compartment electrodialytic water splitter. The gas generated e.g. CO₂, SO₂ is released external to the water splitter where it can be easily removed by conventional techniques such as application of vacuum. The aqueous hydrogen ion-enriched solution selected must be capable of transferring hydrogen ions to the salt of the first acid in an amount sufficient to produce the first acid and a salt of the second acid; the second acid is then regenerated from the salt of the second acid.

Claims

1. A process which comprises the steps of:

contacting a material comprising a salt of a first acid with a hydrogen ion-enriched aqueous solution comprising a second acid to produce a product solution comprising the first acid and a salt of the second acid, and being substantially free of the salt of the first acid;

feeding at least a portion of the product solution to an electrodialytic water splitter and generating therein the hydrogen ion-enriched aqueous solution comprising the second acid;

withdrawing the hydrogen ion-enriched aqueous solution comprising the second acid from the electrodialytic water splitter; and

,

supplying at least portion thereof for contact with material comprising the salt of the first acid.

2. The process of claim 1 wherein the electrodialytic water splitter comprises a unit cell, the unit cell comprising a base compartment and an acid compartment.

3. The process of claim 2 wherein the unit cell further comprises a salt compartment.

4. The process of claim 3 further comprising the step of feeding a portion of the product solution to the salt compartment.

5. The process of claim 4 further comprising the step withdrawing an aqueous solution from the salt compartment and forwarding a portion thereof for contact with material comprising the salt of the first acid.

6. The process of claim 3 wherein the base compartment, acid compartment and salt compartment of the unit cell are defined by cation membranes, means for splitting water into hydroxyl ions and hydrogen ions, and anion membranes.

7. The process of claim 6 wherein said means for splitting water into hydroxyl ions and hydrogen ions is a bipolar membrane.

8. The process of claim 2 wherein at least a portion of the product solution is fed to the acid compartment of the unit cell.

9. The process of claim 8 wherein salt of the first acid is fed to the base compartment.

10. The process of claim 9 further comprising the step of feeding water to the acid compartment.

11. The process of claim 10 further comprising the step of feeding a portion of the product solution to the salt compartment.

12. The process of claim 10 further comprising the step of feeding product solution to the acid compartment.

13. The process of claim 2 wherein a solution comprising water is fed to the base compartment of the unit cell.

14. The process of claim 2 wherein the acid and base compartment of said unit cell are defined by cation membranes and means for splitting water into hydrogen ions and hydroxyl ions.

15. The process of claim 14 wherein said means for splitting water into hydrogen ions and hydroxyl ions is a bipolar membrane.

16. The process of claim 1 wherein the material comprising a salt of a first acid comprises at least one of;

solids recovered from dry scrubbing a SO₂ -containing gas with a basic sodium-containing material;

solids recovered from spray-dry absorption of a SO₂ -containing gas with a basic sodium containing material;

ore containing NaHCO₃, Na₂ CO₃ or mixtures thereof; and

an aqueous solution recovered from wet scrubbing of a SO₂ -containing gas with a basic sodium-containing material.

17. The process of claim 1 wherein contact of the material with the salt of the first acid occurs under conditions of time, temperature, and pressure sufficient to remove substantially all of the gas capable of being liberated from the the salt of the first acid.

18. The process of claim 1 wherein the salt of the first acid is selected from the group consisting of salts of at least one member of Group Ia, IIa, and NH₄⁺, with at least one member of HCO₃^-, CO₃^-, HS^-, S^-, NO₂^-, HSO₃^- and HSO₃^-.

19. The process of claim 18 wherein the salt is an alkali metal salt.

20. The process of claim 1 wherein the second acid of said aqueous hydrogen ion-enriched solution is selected from a group consisting of H₂ SO₄, HSO₄^-, H₃ PO₄^-, H₂ PO₄^-, HPO₄.sup.═

, HCl, H₂ F₂, HF₂^-, HO₂ CCH═

CHCO₂ H, HO₂ CH═

CHCO₂^-, (CO₂ H)₂, (CO₂^-)CO₂ H, CH₂ (CO₂ H)₂, HOC(CH₂ CO₂ H)₂ CO₂ H, HOC(CH₂ CO₂ H)₂ CO₂^-, HOC(CH₂ CO₂ H) (CH₂ CO₂) (CO₂^-), (HOCHCO₂ H)₂, HO₂ CCH(OH)CO₂^-, and HO₂ CR wherein R is H, CH₃, C₂ H₅, CCl₂ H, CCl₃, CH(OH)CH₃, CF₂ H or CF₃.