Method and apparatus for acid mist reduction

• US 4,668,353 A
• Filed: 03/21/1986
• Issued: 05/26/1987
• Est. Priority Date: 10/10/1984
• Status: Expired due to Term

• Current Assignee: Desom Engineered Systems Limited
• Original Assignee: Desom Engineered Systems Limited
• Inventors: Davis, John, Smith, James W.
• Primary Examiner(s): Andrews, R. L.
• Application Number:
  US06/842,199
• Time in Patent Office: 431 Days
• Field of Search: 204/278, 204/129, 204/297 R, 204/297 W, 204/270, 204/289
• US Class Current: 205/628
• CPC Class Codes: C25C 1/12 of copper
• CPC Class Codes: C25C 1/16 of zinc, cadmium or mercury
• 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

Abstract

Bubbles produced at an electrode in an electrolytic process are coalesced by providing a surface-limiting, electrically inert masking device of which at least a bottom portion is submerged in the electrolyte. The masking device reduces the free surface of the electrolyte between the electrodes and this urges the gas bubbles together so that they coalesce, resulting in larger bubbles and less acid mist generation.

Claims

1. A method of coalescing bubbles produced at an electrode in an electrolytic process in which electrodes consisting of at least one anode and at least one cathode are adjacent but spaced from one another, and are substantially immersed in the electrolyte, the method comprising:

affixing to at least one electrode a surface-limiting electrically inert masking means of which at least the bottom portion is submerged in the electrolyte, the masking means extending over the whole upper portion of said one electrode and projecting above the surface of said electrolyte, thus reducing the free surface of the electrolyte between the electrodes, the masking means having a substantially constant cross-section throughout its length, the cross-section including a first upright portion for securing against the electrode in a substantially vertical orientation, the upright portion having an upper end and a lower end, a second portion connected to the first portion at the lower end thereof and projecting outwardly and upwardly away from the first portion and from the electrode so as to define an acute angle with the upright portion, the second portion having an extremity remote from said first portion, aperture means in the second portion adjacent said extremity through which the gas bubbles trapped beneath the second portion can pass upwardly, and a hood portion above the first portion attached to the second portion at said extremity on the side of the aperture means remote from the first portion, the hood portion extending generally upwardly and back toward the first portion, thereby to further coalesce any bubbles passing through said aperture means,

and passing current between the electrodes, thus generating gas bubbles at at least one electrode, the gas bubbles being urged together by the masking means and coalescing.

2. The method claimed in claim 1, in which the cross-section of the masking means further includes a third portion projecting from the bottom of the hood member away from the first portion, the third portion being adapted to flexibly contact an adjacent electrode.

3. The method claimed in claim 1, in which the hood member has affixed to it a flexible member spanning between the hood member and the first upright portion, thereby to permit collection of gaseous materials passing through the aperture means.

4. The method claimed in claim 1, in which the second portion is flexibly attached to the first upright portion.

5. The method claimed in claim 4, in which the said aperture means consists of a plurality of holes along an edge of the second portion remote from the first upright portion, the second portion having, for each hole, a groove in its underside which begins adjacent the first upright portion and terminates at its respective hole.

6. The method claimed in claim 5, in which the cross-section of the masking means further includes a third portion projecting outwardly and obliquely downwardly from the bottom of the hood member in the direction away from the first upright portion, the third portion being flexible with respect to the hood member.

7. The method claimed in claim 6, in which the hood member has affixed to it a flexible member spanning between the hood member and the first upright portion, thereby to permit collection of gaseous materials passing through the aperture means.

8. The method claimed in claim 3, in which the masking means defines under the hood member an elongated chamber for the collection of gaseous materials, the method including the further step of withdrawing collected gaseous materials out of the chamber and disposing of them safely.

9. The method claimed in claim 7, in which the masking means defines under the hood member an elongated chamber for the collection of gaseous materials, the method including the further step of withdrawing collected gaseous materials out of the chamber and disposing of them safely.

10. An electrolysis apparatus in which bubbles of gas produced at an electrode immersed in an electrolyte may be coalesced in order to reduce acid mist generation, the apparatus including electrodes consisting of at least one anode and at least one cathode which are adjacent but spaced from one another, and are substantially immersed in the electrolyte, at least one electrode having affixed thereto a surface-limiting, electrically inert masking means of which at least the bottom portion is submerged in the electrolyte, the masking means extending over the whole upper portion of said one electrode and projecting above the surface of said electrolyte, thus reducing the free surface of the electrolyte between the electrodes, thus urging gas bubbles generated at one of the electrodes to coalesce together, the masking means having a substantially uniform cross-section along its length, the cross-section comprising:

a first upright portion adapted to be affixed against an electrode in a substantially vertical orientation, the first upright portion having a top and a bottom,

a second portion attached to the first upright portion adjacent the bottom thereof, and extending outwardly and upwardly away therefrom so as to define an acute angle with the first upright portion, the second portion having an extremity remote from said first portion,

aperture means in the second portion adjacent said extremity through which the gas bubbles trapped beneath the second portion can pass, and a hood member above the first portion attached to the second portion at said extremity remotely from the first upright portion and on the side of the aperture means remote from the first portion, the hood member extending generally upwardly and back toward the first portion, thereby to further coalesce any bubbles passing upwardly through said aperture means.

11. The apparatus claimed in claim 10, in which the cross-section of the masking means further includes a third portion projecting from the bottom of the hood member away from the first upright portion.

12. The apparatus claimed in claim 10, in which the hood member has affixed to it a flexible member spanning between the hood member and the first upright portion, thereby to permit collection of gaseous materials passing upwardly through the aperture means.

13. The apparatus claimed in claim 10, in which the second portion is flexibly attached to the first upright portion.

14. The apparatus claimed in claim 13, in which the said aperture means consists of a plurality of holes along an edge of the second portion remote from the first upright portion, the second portion having for each hole a groove in its underside which begins adjacent the first upright portion and terminates at its respective hole.

15. The apparatus claimed in claim 14, in which the cross-section of the masking means further comprises a third portion projecting outwardly and obliquely downwardly from the bottom of the hood member in the direction away from the first upright portion, the third portion being flexible with respect to the hood member.

16. The apparatus claimed in claim 15, in which the hood member has affixed to it a flexible member spanning between the hood member and the first upright portion, thereby to permit collection of gaseous materials passing through the aperture means.

17. The apparatus claimed in claim 10, in which the hood member defines beneath it an elongated chamber, means for capping the chamber at both ends, and conduit means for ducting collected gaseous materials out of said chamber.

18. The apparatus claimed in claim 16, in which the hood member defines beneath it an elongated chamber, means for capping the chamber at both ends, and conduit means for ducting collected gaseous materials out of said chamber.

19. A method of coalescing bubbles produced at an electrode in an electrolytic process in which electrodes consisting of at least one anode and at least one cathode are adjacent but spaced from one another, and are substantially immersed in the electrolyte, the method comprising:

affixing to at least one electrode a surface-limiting electrically inert masking means of which at least the bottom portion is submerged in the electrolyte, the masking means extending over the whole upper portion of said one electrode and projecting above the surface of said electrolyte, thus reducing the free surface of the electrolyte between the electrodes, the said masking means having a substantially constant cross-section along its length, the cross-section including an upright member adapted to be affixed against a surface of a first one of said electrodes in a substantially vertical orientation,

covering means extending away from the upright member with a portion located such that it can contact the surface of a second one of said electrodes, said portion being of a flexible material in order to effect a good seal against the surface of said second electrode, whereby any aerosol generated by the electrolyte beneath the covering member will be trapped under the covering member,

and a trough member forming part of the masking means and defining an upwardly open trough having a bottom region and two side regions, one of the side regions serving to define one wall of a passageway along which aerosol generated by electrolysis can reach the interior of the trough, and

passing current between the electrodes, thus generating gas bubbles at at least one electrode, the gas bubbles being urged together by the masking means and coalescing.

20. The method claimed in claim 19, in which the covering means extends first perpendicularly away from the upright member, then curves downwardly to define the other wall of said passageway, the said portion extending from the downwardly directed part of said covering means, the trough member incorporating a lower part of said upright member constituting the other side region of the trough, and a member defining the bottom region of said trough projecting laterally from said lower part of said upright member, and an upright panel forming said one of the side regions of the trough.

21. The method claimed in claim 20, in which the masking means further includes a baffle extending downwardly from said covering means above said trough.

22. The method claimed in claim 19, in which the covering means extends first perpendicularly away from the upright member, then curves downwardly, the said portion extending from the downwardly directed part of said covering means, the trough member incorporating said downwardly directed part of the covering means as the other of the two side regions, and a member defining the bottom region of said trough projecting laterally toward the first electrode from said downwardly directed part of the covering means, thence projecting upwardly adjacent but spaced from the first electrode to define said one of the side regions of the trough, whereby the passageway is defined between the first electrode surface and said one of the side regions of the trough.

23. The method claimed in claim 22, in which the masking means further includes a baffle extending from the bottom of the upright member at the top of said passageway, to provide a surface for the coalescence of aerosol generated by the electrolyte process.

24. An electrolysis apparatus in which bubbles of gas produced at an electrode immersed in an electrolyte may be coalesced in order to reduce acid mist generation, the.apparatus including electrodes consisting of at least one anode and at least one cathode which are adjacent but spaced from one another, and are substantially immersed in the electrolyte, at least one electrode having affixed thereto a surface-limiting, electrically inert masking means of which at least the bottom portion is submerged in the electrolyte, the masking means extending over the whole upper portion of said one electrode and projecting above the surface of said electrolyte, thus reducing the free surface of the electrolyte between the electrodes, thus urging gas bubbles generated at one of the electrodes to coalesce together, the masking means having a substantially uniform cross-section throught its length, and comprising:

an upright member adapted to be affixed against a surface of a first one of said electrodes in a substantially vertical orientation,

covering means extending away from the upright member with a portion located such that it can contact the surface of a second one of said electrodes, said portion being of a flexible material in order to effect a good seal against the surface of said second electrode, whereby any aerosol generated by the electrolyte beneath the covering member will be trapped under the covering member,

and a trough member forming part of the masking means and defining an upwardly open trough having a bottom region and two side regions, one of the side regions serving to define one wall of a passageway along which aerosol generated by electrolysis can reach the interior of the trough.

25. The apparatus claimed in claim 24, in which the covering means extends first perpendicularly away from the upright member, then curves downwardly to define the other wall of said passageway, the said portion extending from the downwardly directed part of said covering means, the trough member incorporating a lower part of said upright member constituting the other side region of the trough, and a member defining the bottom region of said trough projecting laterally from said lower part of said upright member, and an upright panel forming said one of the side regions of the trough.

26. The apparatus claimed in claim 25, in which the masking means further includes a baffle extending downwardly from said covering means above said trough.

27. The apparatus claimed in claim 24, in which the covering means extends first perpendicularly away from the upright member, then curves downwardly, the said portion extending from the downwardly directed part of said covering means, the trough member incorporating said downwardly directed part of the covering means as the other of the two side regions, and a member defining the bottom region of said trough projecting laterally toward the first electrode from said downwardly directed part of the covering means, thence projecting upwardly adjacent but spaced from the first electrode to define said one of the side regions of the trough, whereby the passageway is defined between the first electrode surface and said one of the side regions of the trough.

28. The apparatus claimed in claim 27, in which the masking means further includes a baffle extending from the bottom of the upright member at the top of said passageway, to provide a surface for the coalescence of aerosol generated by the electrolyte process.