Electrochemical system with bed sections having variable gradient

• US 3,915,822 A
• Filed: 05/22/1974
• Issued: 10/28/1975
• Est. Priority Date: 05/22/1974
• Status: Expired due to Term

• Current Assignee: W.R. Grace & Co.-Conn. (WR Grace & Company)
• Original Assignee: Preston Leonard Veltman
• Inventors: Veltman, Preston Leonard
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Prescott, A. C.
• Application Number:
  US05/472,426
• Time in Patent Office: 524 Days
• Field of Search: 204/149,152,151,130,268,254,255,257,301
• US Class Current: 210/665
• CPC Class Codes: C02F 1/001 Processes for the treatment of water whereby the filtration technique is of importance C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00
• CPC Class Codes: C02F 1/46 by electrochemical methods
• CPC Class Codes: C02F 1/46114 Electrodes in particulate form or with conductive and/or non conductive particles between them
• CPC Class Codes: C02F 1/76 with halogens or compounds of halogens C02F1/4674 takes precedence
• CPC Class Codes: C02F 1/78 with ozone C02F1/4672 takes precedence
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: C25C 7/00 Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells for the production of aluminium C25C3/06 - C25C3/22
• CPC Class Codes: C25C 7/002 of cells comprising at least an electrode made of particles C25C7/005, C25C7/02 - C25C7/06 take precedence

Abstract

Processes and apparatus for electrochemical reactions including an electrochemical system in which an electrolyte is treated in a reaction zone containing at least one bed of electrically conductive particles, the improvement includes a reactor for contacting electrolyte with plural transverse electrodes in the reaction zone. The electrodes define separate adjacent electrochemical sections in the reaction zone. Each of the electrodes is biased anodically or cathodically to provide an electrochemical potential between alternating electrodes, and the system establishes different voltage gradients across adjacent sections of the reaction zone. Electrolyte can be circulated through the sections serially in a direction parallel to the voltage gradients of each section to obtain homogeneous treatment. One or more foraminous insulating diaphragms may be disposed in the reaction zone between anodic and cathodic electrodes. The system is useful for pollution control, electrochemical synthesis and metal recovery.

Claims

1. IN AN ELECTROCHEMICAL CELL WHEREIN AN ELECTROLYTE IS TREATED IN A REACTION ZONE CONTAINING AT LEAST ONE BEB OF ELECTRICALLY CONDUCTIVE PARTICLES, THE IMPROVEMENT WHICH COMPRISES:

A PLURALITY OF ELECTRODES FOR CONTACTING ELECTROLYTE IN THE REACTION ZONE, SAID ELECTRODES DEFINING ADJACENT ELECTROCHEMICAL SECTIONS IN SAID REACTION ZONE, MEANS FOR BIASING EACH OF THE ELECTRODES ANODICALLY OR CATHODICALLY TO PROVIDE ELECTROCHEMICAL POTENTIAL BETWEEN ALTERNATING ELECTRODES, MEANS FOR ESTABLISHING DIFFERENT VOLTAGE GRADIENTS ACROSS ADJACENT SECTIONS OF THE REACTION ZONE, AND

2. The cell of claim 1 comprising at least one foraminous insulating diaphragm disposed in the cell between anodic and cathodic electrodes.

3. The cell of claim 2 comprising at least one diaphragm means disposed closely adjacent to at least one electrode for separating the electrically conductive particles from said electrode.

4. The cell of claim 1 wherein the sections of the reaction zone are contained in an integral reaction vessel having opposite electrolyte inlet and outlet means disposed at bottom at top portions of said vessel, and wherein foraminous electrodes are mounted transverse to the direction of electrolyte flow to permit passage of electrolyte therethrough.

5. The cell of claim 4 including means for disposing foraminous electrodes to support the particles in substantially fixed position as a packed bed;

and means for flowing electrolyte upwardly.

6. The cell of claim 1 wherein the electrically conductive particles consist essentially of graphite pellets having an average particle size of at least about one-half mm.

7. The cell of claim 1 including means for maintaining a first voltage gradient in a first discrete reaction section;

means for maintaining a second voltage gradient different from said first voltage gradient in a second discrete reaction section; and

means for insulating the bed particles from at least one major surface of each of said electrodes to prevent ohmic contact with said major surface.

8. The cell of claim 1 including means for maintaining a continuous liquid phase of electrolyte in contact with the electrodes and means for passing electrolyte through the cell serially and treating electrolyte homogeneously in each of the different voltage gradient sections of the reaction zone.

9. The cell of claim 1 wherein said sections are substantially uniform in thickness and wherein substantially different voltages are impressed across adjacent sections.

10. The cell of claim 1 wherein adjacent sections have substantially different thicknesses between electrodes, and wherein the electrodes are formed, in a spiral or toroidal configuration.

11. The cell of claim 10 including means for applying substantially equal voltages across adjacent sections.

12. The cell of claim 1 wherein the electrically conductive particles consist essentially of carbon pellets.

13. The cell of claim 1 wherein the electrically conductive particles consist essentially of Si.

14. The cell of claim 1 wherein the electrically conductive particles consist essentially of SiC.

15. The cell of claim 1 wherein the electrically conductive particles comprise elongated particles having magnetic orientation, and wherein the cell includes means for aligning said magnetic particles in a magnetic field.

16. The cell of claim 1 wherein the electrically conductive particles consist essentially of an electrochemically active metal core having a continuous coating of hydrophilic ion-permeable resin.

17. The cell of claim 1 wherein the electrically conductive particles consist essentially of carbon pellets having mercury deposited thereon.

18. An electrochemical cell comprising:

at least three primary electrodes spaced apart in alternating positions to form a plurality of separate electrochemical reaction zone sections;

means for containing electrically conductive discrete particles said reaction zone sections;

means for maintaining electrolyte in the reaction zone sections;

means for applying electrical potential between electrodes and maintaining at least two different voltage gradients in said cell.

19. The electrochemical cell of claim 18 wherein the particles comprise carbon particles having an average size of at least one-half mm.

20. The electrochemical cell of claim 18 wherein the electrically conductive particles are selected from the group consisting of metals, metal compounds, semiconductive elements and mixtures thereof.

21. The electrochemical cell of claim 18 wherein said electrodes are foraminous to permit flow of electrolyte through said electrodes and said reaction zone sections and means for flowing through both anodic and cathodic areas in said cell.

22. A stacked electrochemical cell of substantially uniform cross-sectional area comprising:

a stack of separate porous bed sections, each of said bed sections containing discrete electrically conductive particles;

primary electrodes at opposite ends of said stack;

at least one auxiliary electrode disposed between bed sections;

means for applying a first voltage gradient between one of said primary electrodes and said auxiliary electrode;

means for applying a second voltage gradient substantially different from the first gradient between another of said primary electrodes and said auxiliary electrode; and

means for flowing electrolyte through said stack in contact with said electrodes.

23. The cell of claim 22 comprising:

foraminous electrodes having means for supporting said particles and means for flowing electrolyte through said electrodes.

24. The cell of claim 22 wherein adjacent bed sections have substantially different thicknesses between electrodes and further comprising means for applying substantially equal voltage across adjacent bed sections, thereby establishing different voltage gradients.

25. The cell of claim 22 wherein adjacent cell sections are separated by a common intermediate electrode of a first polarity and wherein adjacent sections are bounded by major electrodes of a second opposite polarity.

26. The cell of claim 22 comprising:

means for directing electrolyte upwardly at a flow rate sufficient to fluidize the bed sections.

27. The cell of claim 26 comprising:

at least one foraminous insulating means for separating the electrically conductive particles from at least one primary electrode.

28. The cell of claim 27 including means for contacting the particles with the auxiliary electrode to bias the bed sections electrically.

29. The cell of claim 22 including means for introducing a gaseous reactant into at least one of the bed sections and means for venting the cell.

30. In an electrochemical process wherein an electrolyte is treated in a reaction zone containing at least one bed of electrically conductive particles, the improvement which comprises the steps of:

contacting electrolyte with a plurality of electrodes in the reaction zone, said electrodes defining discrete adjacent electrochemical sections in said reaction zone;

biasing each of said electrodes anodically or cathodically to provide electrochemical potential between alternating electrodes;

establishing different voltage gradients across adjacent sections of the reaction zone; and

circulating electrolyte through said sections serially in a flow path through at least one intermediate foraminous electrode.

31. The process of claim 30 wherein at least one foraminous insulating diaphragm is disposed in the reaction zone between anodic and cathodic electrodes.

32. The process of claim 30 wherein at least one diaphragm is located in contact with at least one electrode to separate the electrically conductive particles from the electrode, wherein the sections of thE reaction zone are contained in a integral reaction vessel having electrolyte inlet and outlet disposed at bottom at top portions of said vessel, and wherein foraminous electrodes are mounted transverse to the direction of electrolyte flow to permit passage of electrolyte therethrough.

33. The process of claim 30 which includes providing planar foraminous electrodes to support the particles in substantially fixed position as a packed bed;

and continuously flowing electrolyte upwardly through said foraminous electrodes.

34. The process of claim 30 comprising the step of electrolyzing a dilute aqueous solution containing metal ions to deposit said metal cathodically.

35. The process of claim 30 including the step of contacting electrolyte with ion exchange material.

36. The process of claim 30 including the step of contacting the electrochemically treated electrolyte with activated carbon to remove impurities non-electrolytically.

37. The process of claim 30 wherein the electrolyte contains metal cyanide and including the step of depositing said metal cathodically in a first electrochemical section.

38. The process of claim 37 including the step of oxidizing cyanide ion in a second section down stream from the first section.

39. The process of claim 38 including the step of contacting cyanide ion with an ozone containing gas in said second section.

40. The process of claim 30 including the step of contacting electrolyte with a reactant gas introduced to at least one of said sections.

41. The process of claim 30 wherein the electrolyte contains a dye having organic functional group.

42. The process of claim 30 wherein the electrolyte contains an amalgam-forming metal and wherein the electrically conductive particles have mercury deposited thereon and including the step of forming an amalgam simultaneously with electrodeposition.

43. The process of claim 30 wherein pathogenic microorganisms in the electrolyte are treated with an ozone containing gas in an anodic section.

44. The process of claim 30 including the step of contacting the electrolyte said reaction zone with a mixture of ozone and a diluent gas.

45. The process of claim 30 wherein the electrolyte contains water-borne pathogenic microorganisms which are inactived by electrochemical treatment.

46. The process of claim 30 including the step of fluidizing the electrically conducting particles in the reaction zone by flowing electrolyte upwardly at sufficient velocity to maintain an expanded particle bed.

47. The process of claim 41 including the step of biasing the fluidized particles by contact with an intermediate electrode.

48. In an electrochemical process wherein a porous bed of electrically conductive particles is maintained in a reaction zone between first and second electrodes electrolyte is passed through the bed parallel to electrical current, the improvement which comprises the steps of:

providing at least one foraminous auxiliary electrode disposed in the porous bed transverse to the direction of flow to provide continuous ionically-conducting fluid paths; and

maintaining substantially different voltage gradients between said auxiliary electrode and said first and second electrodes, whereby homogeneous treatment of the electrolyte is obtained.