Process and apparatus for treatment of fluids, particularly desalinization of aqueous solutions

• US 4,636,296 A
• Filed: 01/23/1985
• Issued: 01/13/1987
• Est. Priority Date: 08/18/1983
• Status: Expired due to Term

• Current Assignee: USFilter
• Original Assignee: Gerhard Kunz
• Inventors: Kunz, Gerhard
• Primary Examiner(s): Demers, Arthur P.
• Application Number:
  US06/693,948
• Time in Patent Office: 720 Days
• Field of Search: 204/182.5, 204/301
• US Class Current: 204/524
• CPC Class Codes: B01D 61/48 having one or more compartments filled with ion-exchange material , e.g. electrodeionisation
• CPC Class Codes: B01J 47/08 subjected to a direct electric current
• CPC Class Codes: C02F 1/42 by ion-exchange ion-exchange in general B01J
• CPC Class Codes: C02F 1/4604 for desalination of seawater or brackish water
• CPC Class Codes: C02F 1/469 by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
• CPC Class Codes: C02F 2201/46115 Electrolytic cell with membranes or diaphragms
• CPC Class Codes: C02F 2301/08 Multistage treatments, e.g. repetition of the same process step under different conditions
• CPC Class Codes: Y02A 20/124 Water desalination

Abstract

The invention refers to a process and a device for the performance of a process for the treatment of liquids, particularly for the demineralization of aqueous solutions, whereby the liquid being treated is conducted through successive chambers of treatment, wherein in a first stage of the treatment demineralization takes place by means of ion displacement and in a second stage of post-treatment by means of ion desorption the salts that are removed from the treated liquids are led into so-called brine chambers, and are washed out of these chambers into a channel or other receiver by means of a transporting liquid.

Claims

1. A process for demineralizing an aqueous liquid containing salts, comprising:

successively passing the liquid through alternating separate layers of at least one means for exchanging cations and at least one means for exchanging anions to obtain a substantially demineralized liquid, said means for exchanging cations containing labile hydrogen ions and said means for exchanging anions containing labile hydroxyl ions;

applying electric energy between an anode and a cathode across the direction of the flow of the liquid and through said layered means, whereby cations and anions disassociated from the salts are transferred in opposite directions out of said layers and toward the cathode and anode, respectively; and

flushing said cations and said anions.

2. The process of claim 1 wherein said liquid passes successively and alternatingly first through one cationexchange means and then through one anion-exchange means.

3. The process of claim 1, wherein the applied electric energy is effective to attain a constant ionic current through said anode and cathode.

4. The process of claim 1 wherein the anions disassociated from the salts are transferred out of said layers into a flushing solution towards the anode.

5. The process of claim 4 further comprising:

passing the flushing solution containing the flushed anions adjacent to the cathode; and

flushing said cations and said anions adjacent to said cathode.

6. The process of claim 1, wherein the starting aqueous liquid containing salts is a partially demineralized liquid.

7. The process of claim 4 wherein said anions are flushed with a portion of the substantially demineralized liquid as the flushing solution.

8. The process of claim 1 wherein said means for exchanging cations and said means for exchanging anions are cation-exchange and anion-exchange resins.

9. A process for demineralizing an aqueous liquid containing salts, comprising a displacement stage and a desorption stage;

said displacement stage comprising;

alternatingly passing the liquid through at least one means for exchanging cations and at least one means for exchanging anions to obtain a partially demineralized liquid, said cation-exchange means containing labile hydrogen ions and said anion-exchange means containing labile hydroxyl ions, whereby cations and anions disassociated from the salts are exchanged for the labile hydrogen ions and the labile hydroxyl ions;

applying electric energy between an anode and a cathode across the direction of flow of the liquid, whereby hydrogen ions and hydroxyl ions migrating in opposite directions are exchanged for the cations and anions in the means for exchanging ions, thereby restoring said labile hydrogen and hydroxyl ions to said ion-exchange means and allowing for the displaced cations and anions to migrate in opposite directions; and

passing at least one first flushing solution across the direction of the electric current capable of receiving the cations migrating from said means for exchanging cations and the anions migrating from said means for exchanging anions, whereby salts are formed and discharged with said first flushing solution; and

said desorption stage comprising;

successively passing the partially demineralized liquid from said displacement stage through alternating separate layers of at least one cation-exchange means and at least one anion-exchange means to obtain a substantially demineralized liquid;

applying electric energy between an anode and a cathode across the direction of flow of the liquid and through said layered means, whereby residual cations and anions disassociated from the salts are transferred in opposite directions out of said layers and toward the cathode and the anode, respectively; and

flushing said cations and said anions.

10. The process of claim 9 wherein said liquid passes successively and alternatingly first through one cationexchange means and then through one anion-exchange means of said desorption stage.

11. The process of claim 9 wherein

the anions disassociated from the salts are transferred out of said layers and into a second flushing solution towards the second anode of said desorption stage;

and

said anions are flushed.

12. The process of claim 11, further comprising:

passing the second flushing solution containing the flushed anions adjacent to said second cathode of said desorption stage; and

flushing said cations and said anions adjacent to said second cathode.

13. The process of claim 11, further comprising:

flushing said anions of said desorption stage with a portion of the substantially demineralized liquid of said desorption stage as the second flushing solution.

14. The process of claim 9, wherein the first flushing solution is brine.

15. The process of the claim 9 wherein the cationexchange means and the anion-exchange means are cation-exchange resins and anion-exchange resins.

16. The process of claim 9, wherein the migration of anions into said means for exchanging cations towards said anode means, and the migration of said cations into said means for exchanging anions towards said first cathode of said displacement stage is blocked.

17. The process of claim 9, wherein the electric energy applied between said cathode and said anode of said displacement stage, and between said cathode and said anode of said desorption stage is effective to attain a constant current through said displacement stage and said desorption stage.

18. The process of claim 9, wherein said aqueous liquid containing salts is successively passed first through one means for exchanging cations and then through one means for exchanging anions of said displacement stage.

19. The process of claim 12, further comprising passing said aqueous liquid through a second means for exchanging cations of said displacement stage.

20. The process of claim 9, wherein said first anode of said displacement stage and said anode of said desorption stage are one and the same or separate anodes.

21. The process of claim 9, wherein the cations displaced from said cation-exchange means and the anions displaced from said anion-exchange means are transferred to the first flushing solution of said displacement stage at about the same time.

22. The process of claim 9, wherein said first flushing solution of said displacement stage is the flushing solution flowing out of said second cathode of said desorption stage.

23. The process of claim 9, wherein the aqueous liquid containing salts is passed

first through a first cation-exchange means of said displacement stage;

then through a first anion-exchange means of said displacement stage;

then through a second cation-exchange means of said displacement stage; and

then successively through said alternating separate layers of said cation-exchange and said anion-exchange means of said desorption stage.

24. An apparatus for demineralizing an aqueous liquid containing salts, comprising:

at least one anode compartment with an anode therein;

at least one cathode compartment with a cathode therein;

at least one desorption compartment positioned between said anode and said cathode compartments;

said desorption compartment containing alternating separate layers of at least one cation-exchange means and at least one anion-exchange means, each said ion-exchange means being adjacent to both said cathode and said anode compartments;

means for introducing and removing said aqueous liquid from said layered desorption compartment, wherein the liquid being removed is substantially demineralized;

means for selectively permeating anions separating from said layered desorption compartment toward said anode compartment and means for selectively permeating cations separating said desorption compartment toward said cathode compartment;

means for applying an electric potential between said anode and said cathode and across said layered desorption compartment, whereby cations and anions disassociated from the salts in said layered desorption compartment are transferred in opposite directions out of said layered desorption compartment and toward the cathode and the anode, respectively; and

means for flushing said cations and said anions.

25. The apparatus of claim 24, further comprising:

an anion flushing compartment positioned between said desorption compartment and said anode compartment;

means for introducing and removing a flushing liquid from said flushing compartment; and

means for selectively blocking anions separating from said layered desorption compartment from entering said anode compartment.

26. The apparatus of claim 24, wherein the means for selectively permeating ions is a membrane.

27. The apparatus of claim 25, wherein the means for selectively blocking anions is a cation permeable membrane.

28. The apparatus of claim 24, wherein the applied electric potential applied between said anode and said cathode is effective to attain a constant circulating current.

29. The apparatus of claim 24 further comprising means for transferring the flushing liquid from said anion flushing compartment into said cathode compartment.

30. The apparatus of claim 25 further comprising:

means for transferring a portion of the substantially demineralized liquid discharged from said desorption compartment into said anion flushing compartment.

31. An apparatus for demineralizing an aqueous liquid containing salts which includes a displacement stage and a desorption stage;

said displacement stage comprising;

at least one anode compartment with an anode therein;

at least one cathode compartment with a cathode therein;

at least one cation-exchange compartment containing a cation-exchange means therein;

at least one anion-exchange compartment containing an anion-exchange means therein;

at least one first flushing compartment positioned between said cation-exchange compartment and said anion-exchange compartment, all of said foregoing compartments separated from each other by means for selectively permeating ions;

means for introducing and removing the aqueous liquid from each of said cation-exchange and anion-exchange compartments, wherein said liquid is partially demineralized;

means for flushing said cations and said anions from said flushing compartment; and

means for applying an electric potential between said anode and said cathode and across said cation-exchange means, said anion-exchange means, and said flushing compartment, whereby cations and anions disassociated from the salts migrate in opposite directions toward said cathode and said anode, respectively; and

said desorption stage comprising;

at least one anode desorption compartment with an anode therein;

at least one cathode desorption compartment with a cathode therein;

at least one ion desorption compartment positioned between said anode and said cathode desorption compartments;

said ion desorption compartment containing alternating separate layers of at least one cation-exchange means and at least one anion-exchange means, each said means being adjacent to said cathode and said anode desorption compartments;

means for introducing said partially demineralized liquid from said displacement stage into said layered desorption compartment and means for removing said liquid from said layered desorption compartment, said outflowing liquid being substantially demineralized;

means for selectively permeating anions separating said layered desorption compartment toward said anode desorption compartment and for selectively permeating cations separating said layered desorption compartment toward said cathode desorption compartment;

means for applying an electric potential between said second anode and said second cathode across said layered desorption compartment, whereby residual cations and anions disassociated from the salts in said layered desorption compartment are transferred in opposite directions out of said layered compartment and toward said second anode and said second cathode, respectively; and

means for flushing said cations and said anions from said desorption stage.

32. The apparatus of claim 31, wherein said cationexchange means is a cation-exchange resin;

and

said anion-exchange means is an anion-exchange resin.

33. The apparatus of claim 31 wherein the desorption stage further comprises:

an anion flushing compartment positioned between said layered desorption compartment and said second anode compartment;

means for introducing and removing a second flushing liquid from said anion flushing compartment; and

means for selectively permeating anions separating said flushing compartment from said layered desorption compartment and said second anode compartment.--

34. The apparatus of claim 31 wherein said means for permeating ions is a membrane.

35. The apparatus of claim 33 wherein the means for selectively permeating anions separating said flushing compartment from said second anode of said desorption stage is a double anion-permeable membrane.

36. The apparatus of claim 31 wherein the electric potentials applied between said anode and said cathode of said displacement stage, and between said anode and said cathode of said desorption stage are effective to attain a constant current through said displacement stage and said desorption stage.

37. The apparatus of claim 33 wherein the desorption stage further comprises means for transferring said second flushing liquid from said anion flushing compartment of said desorption stage into said second cathode compartment of said desorption stage.

38. The apparatus of claim 33, wherein said desorption stage further comprises means for transferring a portion of the substantially demineralized liquid discharged from said layered desorption compartment into said flushing compartment of said desorption stage.

39. The apparatus of claim 31, wherein said first anode of said displacement stage and said second anode of said desorption stage are one and the same.

40. The apparatus of claim 33, further comprising:

means for transferring aqueous liquid from said cation-exchange compartment of said displacement stage into said anion-exchange compartment of said displacement stage; and

means for transferring the partially demineralized aqueous liquid flowing out of said anion-exchange compartment of said displacement stage into said layered desorption compartment of said desorption stage.

41. The apparatus of claim 33, further comprising:

means for transferring the partially demineralized liquid from said displacement stage into said second anode of said desorption stage.

42. The apparatus of claim 31, wherein the aqueous liquid being demineralized is successively passed:

first through said cation-exchange means of said displacement stage, and then through said anion-exchange means of said displacement stage; and

thereafter through said layered desorption compartment of said desorption stage.

43. The apparatus of claim 31, wherein said means for selectively permeating ions which separate said anion-exchange means from said first flushing chamber and said first cathode of said displacement stage are anion-permeable membranes;

and

said means for selectively permeating ions separating said first cation-exchange means from said first flushing chamber and said first anode of said displacement stage are cation-permeable membranes.

44. The apparatus of claim 31, wherein the anionexchange membranes separating said anion-exchange compartment from said first flushing chamber and said first cathode of said displacement stage are double anion-exchange membranes.

45. The apparatus of claim 31, wherein

said displacement stage contains first and second cation-exchange compartments and one anion-exchange compartment;

and further comprises;

a means for attaining about the same displacement time for the cations and anions migrating from the electrodes into the first flushing chamber of said displacement stage.

46. The apparatus of claim 33 further comprising:

means for transferring a flushing liquid flowing out of said second cathode of said desorption stage into said first flushing compartment of said displacement stage.