WO1997022736A1

WO1997022736A1 - Container for corrosive material

Info

Publication number: WO1997022736A1
Application number: PCT/US1996/019707
Authority: WO
Inventors: John O. Harry
Original assignee: Corrosion Ip Corporation
Priority date: 1995-12-18
Filing date: 1996-12-11
Publication date: 1997-06-26
Also published as: AU1414797A

Abstract

An apparatus for recovering a metal from a toxic solution is disclosed. The apparatus includes a plurality of vessels (10, 10a, 10b) for containing the solution, each vessel (10) including an upper portion above the solution, electrode (50) extending into the solution in each vessel (10) for passing an electric current therethrough wherein toxic mist occurs in the upper portions of the vessels (10, 10a, 10b) above the surfaces of the solution, at least one pair of said vessels (10-10a and 10-10b) being disposed in a side-by-side relation to define spaces (44, 46) therebetween, and creating an airflow in the upper portion of the adjacent vessels from the space (44) between one pair of vessels (10-10a) to the space (46) between another pair of vessels (10-10b) for evacuating the toxic mist from above the solution in said vessels (10, 10a, 10b).

Description

CONTAINER FOR CORROSIVE MATERIAL

BACKGROUND OF THE INVENTION

This invention relates to a pollution control system and more particularly to a system for removing noxious mists from electrowinning cells.

Electrowinning of copper involves a process of recovering copper from a sulfuric acid solution by the passage of electric current between an anode which may be formed of a material such as lead and a copper cathode upon which the copper is harvested.

The process is normally carried out in an electrolytic cell in which a plurality of alternate anodes and cathodes are suspended from cell top furniture which extends along the sides of the vessel. This process results in the formation of oxygen bubbles which rise to the surface of the electrolyte and burst thereby forming a mist of an acid such as sulfuric acid. This acid mist is hazardous to workers and must be removed, or suppressed.

Attempts to solve the acid mist problem in copper electrowinning facilities include the use of large ventilation fans which can effectively reduce the mist, but involve high capital costs. Another solution is to cover the bath with foam strips located between the electrodes, or with layers of plastic beads or balls. These solutions are also not satisfactory because the foam strips require the use of reagents which contaminant the solvent extraction process. Plastic balls have not been wholly satisfactory because they may affect cathode quality and beads are difficult to contain within the cells.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a new and improved method and apparatus for controlling acid mists in copper electrowinning cells. This and other objects and advantages of the invention will become more detailed from the detailed description thereof taken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a side elevational view in section showing a cell according to the present invention;

FIGURE 2 is a view taken along lines 2-2 of Figure 1;

FIGURE 3 is a partial plan view of the cell illustrated in Figure 1; and

FIGURE 4 is an enlarged fragmentary cross section showing a portion of the cell illustrated in Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Cell 10 according to the preferred embodiment of the invention is shown in the drawings to include a bottom 12, side walls 13 and 14, and end walls 15 and 16. The cell may be formed of any suitable material such as the polymer concrete disclosed in U.S. Patent No. 4,885,072 which is incorporated by reference herein. The inner and outer surfaces of the cell may be coated with a corrosion-resistant lining as disclosed in U.S. Patent No. 5,079,050, which is incorporated by reference herein. A matrix of reinforcing bars (not shown), of a non-conductive material, such as FRP fiberglass, is disposed in the bottom 12 and extends at least up the side and end walls 13, 14, 15 and 16 as reinforcement against damage. An overflow box 18 is provided in a generally semi-circular formation 19 integrally molded on the outer surface of the end wall 16 and adjacent the side wall 14. The overflow box 18 includes a recess 20 formed in the inner portion of formation 19 and opening into the interior of cell 10. An overflow pipe 21 is cast in the formation 19 and extends vertically from the recess 20 downwardly for connection to a sump for collection of the overflow electrolyte.

A longitudinal groove 24 formed on its inner surface 25 of side wall 14 and adjacent the upper end thereof. An adjustable weir 26 is fixed to the inner surface 25 of wall 14 and adjacent the lower portion of groove 24 in any suitable manner such as by means of screws 30 which extend through slots 31 formed in the weir 26 and which are receivable within threaded inserts 32 disposed in the wall 14 below groove 24. The weir is formed of a suitable non-corrosive material and its upper edge includes a plurality of notches 34. Fresh electrolyte is introduced into the cell by means of manifolds 36 (Figure 2) which extend longitudinally along the bottom 12 and adjacent the side walls 13 and 14 and each has apertures 36 through which electrolyte flows into the cell 10. Overflow electrolyte flows through the notches 34 in weir 26, one end of which communicates with the overflow box 18. From the overflow box 18, the electrolyte flows downwardly through the overflow pipe 21. The upper end of each of the side walls 13 and 14 has a plurality of spaced notches 40 and 42, respectively, which are distributed uniformly from end to end. The cells 10 in a copper electrowinning plant are arranged in a side-by-side and end-to-end relation as illustrated in Figure 2 where cell 10 is flanked by cells 10a and 10b in an alternating orientation such that the wall 13a of cell 10a is adjacent wall 13 of cell 10 and wall 14b of cell 10b is adjacent the wall 14 of cell 10. This defines a first space 44 between cells 10 and 10a and a second space 46 between cells 10 and 10b. The upper ends of the spaces 44 and 46 are closed by capping boards 48 which are supported on the upper edges of the side walls 13 and 13a and the adjacent side walls 14 and 14b. As seen in Figure 2, the cell top furniture provides support for the electrodes 50 and extend from one end of the cells 10, 10a and 10b to the other. The cell top furniture rests on the upper edges of the side walls 13, 13a, 14 and 14b so that a first series of gaps 52 are defined by the notches 40 and 40a in side walls 13 and 13a and a second series of gaps 54 and 54a are defined by the notches 42 and 42b in side walls 14 and 14b. This communicates the interior of cells 10, 10a and 10b with the spaces 44 and 46.

The lower ends of the spaces 44 and 46 are closed by longitudinal flanges 52 and 54 extending respectively from the lower ends of the side walls 14 of cell 10 and flange 52a extending from the lower end of side wall 13a of cell 10a and flange 54b which extends from the lower end of side wall 14b of cell 10b. In a similar manner, the ends of space 44 are closed by flanges 56 and 58 extending from each of the end walls 15 and 16 of cell 10 and mating flanges 56a extending from the end walls of cell 10a and 58b extending from the end walls of 10b.

An air delivery system 60 is connected by a conduit 62 to an opening 64 formed in the flanges 52 and 52a for providing air under pressure to the space 44. An exhaust system 66 is connected by a conduit 68 to an opening 70 formed in the flanges 54 and 54b so that the exhaust system 66 communicates with the space In operation, air under pressure is delivered from the air system to the gap 44 and flows upwardly to the upper end thereof and out between the openings 52 and 52a. As seen in Figure 3, the notches 40 are wider at their inner ends than the outer ends so that as the air flows through the gaps 52, it fans outwardly over the upper surface of the electrolyte. This forms an air curtain which entrains the acid mists and carries it across the upper end of the cell where it is drawn into the space 46, downwardly between the walls 14 and 14b and to the exhaust system 66. As a result, the acid mists can be captured and removed without the need for coverings such as foam pads, plastic balls or beads on the upper surface of the electrolyte. It will be appreciated that because both the inner and outer surfaces of the side walls 13 and 14 are exposed to the corrosive material, it is preferable that both the inner and outer surfaces of the cell 10 be coated with a corrosion resistant material.

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Claims

I CLAIM :

1. An apparatus for recovering a metal from a toxic solution and including a plurality of vessels for containing the solution, each vessel including an upper portion above the solution, electrode means extending into the solution in each vessel for passing an electric current therethrough wherein toxic mist occurs in the upper portions of the vessels above the surfaces of the solution, at least one pair of said vessels being disposed in a side-by-side relation to define a space therebetween, and means for creating an airflow in the upper portions of the adjacent vessels and over the surfaces of the solution in said adjacent vessels and outwardly from said vessels and into said space for evacuating the toxic mist from above the solution in said vessels.

2. The apparatus set forth in claim 1 and including means for enclosing said space.

3. The apparatus set forth in claim 2 wherein said pair of vessels each has a side wall adjacent that of the other, said side walls having upper and lower ends for defining upper and lower portions of said space, suction producing means coupled to the lower end of the space for drawing the toxic mist downwardly along the sides of the vessels.

4. The apparatus set forth in claim 3 wherein the means for enclosing said space includes a first member extending across the gap between the upper ends of the adjacent side walls and a second member extending between lower ends of said side walls.

5. The apparatus set forth in claim 4 wherein said vessels have means extending along the upper end of the side walls for supporting said electrodes, and openings formed beneath the electrode supporting means for communicating the vessels with the space.

6. An apparatus for recovering a metal from a toxic solution and including a plurality of vessels for containing the solution, each vessel including an upper portion above the solution, electrode means extending into the solution in each vessel for passing an electric current therebetween wherein a toxic mist occurs in the upper portions of the vessels and above the surfaces of the solution, said vessels being disposed in a side-by-side relation and each having first and second sides for defining a first space between the first side of a first vessel and the second side of a second vessel adjacent the first side of the first vessel and a second space between the second side of the first vessel and the first side of a third vessel adjacent the second side of the first vessel, means for enclosing said first and second spaces, means for communicating the upper portions of the first and second vessels with the firεt space and the upper portions of the first and third vessels with said second space, means for creating a positive pressure in the first space and means for creating a suction in the second space whereby currents are created in the upper portions of the vessels causing the toxic mist to flow out of said firεt and third vessels and into said second space.

7. The apparatus set forth in claim 6 wherein said suction producing means is coupled to the lower end of the second space for drawing the toxic mist downwardly along the sides of the vessel.

8. The apparatus set forth in claim 7 wherein the means for creating pressure in the first space is coupled to the lower end thereof for introducing air under pressure into the lower end of the first space, said air flowing over the upper portion of the vessels for entraining the toxic mist and carrying said mist into the second space.

9. The apparatus set forth in claim 8 wherein each of said vessels have an upper end, the means for enclosing said spaces includes a first member extending across the gap between the upper ends of the vessels and a second member extending between adjacent walls of said vessels.

10. The apparatus set forth in claim 8 wherein the vessels have means extending along the upper end of the side walls for supporting said electrodes, and openings formed beneath the electrode supporting means for communicating the vessels with the first and second spaces.

11. The apparatus set forth in claim 6 wherein the means for creating pressure in the first space is coupled to the lower end thereof for introducing air under pressure into the lower end of the first space, said air flowing over the upper portion of the vessels for entraining the toxic mist and carrying said mist into the second space.

12. The apparatus set forth in claim 6 wherein each of said vessels have an upper end, the means for enclosing said spaces includes a first member extending across the gap between the upper ends of the vessels and a second member extending between adjacent walls of said vessels.

13. The apparatus set forth in claim 6 wherein the vessels have means extending along the upper end of the side walls for supporting said electrodes, and openings beneath the electrode supporting means for communicating the vessels with the first and second spaces.

14. A method of electrowinning copper comprising the steps of disposing in a vessel a solution containing copper ions and sulfuric acid, suspending a plurality of electrodes in the solution, passing an electric current between said electrodes, wherein copper is harvested on one of the electrodes and wherein a mist of sulfuric acid is generated and collects above the surface of the solution, passing an air current from one side of the vessel to the other and across the surface of the solution for entraining the sulfuric acid mist, collecting the entrained sulfuric acid mist and air in a space formed between adjacent vessels and drawing the air and entrained acid mist downwardly between the adjacent vessels and collecting said acid mist adjacent the lower end of the vessels.

15. An apparatus for recovering a metal from a toxic solution and including a vessel for containing the solution, said vessel including an upper portion above the solution, electrode means extending into the solution for passing an electric current therebetween wherein toxic mist occurs in the upper portion of the vessel above the surface of the solution, means defining an evacaution space adjacent one side of the vessel, means for creating an air flow in the upper portion of the vessel and over the surface of the solution and outwardly from said vessel and into said space for evacuating the toxic mist from above the solution in said vessel.

16. The apparatus set forth in claim 15 wherein said vessel includes a side wall having upper and lower ends, said side wall forming a part of the evacuation space, and suction producing means coupled to the lower end of the space for drawing the toxic mist downwardly along the side of the vessel.

17. The apparatus set forth in claim 16 wherein said vessel has a second side wall, means including said second side wall for defining a second space which communicates with the upper end of the vessel, means coupled to said second space for creating pressure therein for producing an air flow across the upper end of said vessel and into said evacuation space for entraining the toxic mist and carry said mist into the evacuation space.