Equipment for Stirring the Electrolyte in Electrolytic Production Cells

Abstract

The current systems for stirring electrolyte in the cells for the electrolytic production of metals consists of introducing into the production cells, air or compressed neutral gases at low pressure in ventilators, and distribute them in the cell by means of perforated pipes to stir the electrolyte. These pipes are firmly attached to the structure of the cell or to a supporting structure of insulating material, in the case of the newly designed cells. With use, the crystallization of salts dissolved in the electrolyte, the depositing of solids and of anodic sludge will obstruct the perforations of the pipes, limiting the circulation of the electrolyte stirring air. During the operation of the cell, breakdowns or failures occur in the ventilators, distribution ducts and perforated pipes of this system for different reasons whose reparation or cleaning implies losing production time.

Description

DESCRIPTION OF WHAT IS KNOWN IN THE FIELD

Normally the depositing of metals by electrolysis from a solution is executed in masonry cells, coated with insulating materials, resistant to acids or alkalis and to temperature, in which the electrolyte is normally fed through one end of the cell, while the spent electrolyte is discharged by the opposite lower end, if the feeding has been via the upper border, or vice versa.

Occasionally transversal circulation of the electrolyte has been used, that is, parallel to the faces of anodes and cathodes, by means of the introduction of perforated piping, in which the feed is carried out through a longitudinal perforated pipe, located at the bottom on one side of the cell, while the discharge is executed by overflow or through another perforated pipe located on the opposite upper side of the cell.

In both situations, the position of the pipes, once in place, remains inalterable, as these become part of the structure of the cell.

To improve current efficiency, air is sometimes injected to stir the electrolyte and obtain a uniform concentration, which helps avoiding the crystallization of the electrolyte and diminishes the effect of the boundary layer. This is executed introducing perforated pipes through which air or neutral gases are injected, which requires the supplying of ventilators, air supply ducts and the perforated distribution pipes. The fact of having pipes filled with air submerged in the electrolyte causes them to have a tendency to float; therefore the systems with which the pipes are attached to the cells is complex.

During the normal operation, the crystallization of salts dissolved in the electrolyte, the falling of lead due to the wear of the anodes that contain it, as well as other solids, causes sediment to accumulate in the bottom of the cell, and it also settles on the perforated air distribution pipes, obstructing the flow. This makes stopping the operation necessary in order to clean the pipes, which implies losing production time.

Other motives for executing maintenance of the air distributors originate in the physical breaking of the pipes, either due to material failure or knocks.

Recently, to improve efficiency and, among other things, avoid production losses due to the maintenance of the cells, removable insulating structures are used, such as that indicated in Chilean patent application N° 1020-04, in which the anodes, cathodes, electrolyte circulation piping and air distribution pipes are mounted, all of which can be removed from the cell at the end of the production cycle for maintenance purposes, thus drastically reducing production losses due to this cause.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of the supporting structure of insulating material, which can be introduced and withdrawn from the cell, in which the vertical and horizontal guides can be seen on which the anodes and cathodes are mounted, to which the circuits of piping for electrolyte distribution and the electrical conductors for the generation of the electrolyte stirring gases can be attached.

FIG. 2 shows a perspective view of the support structure of insulating material, in which an assembly of electrical conductors mounted on the structure can be seen.

FIG. 3 shows a perspective view of the electrical conductors, mounted on the lower crosspieces of the support structure of insulating material.

FIG. 4 shows a perspective view of the electricity supply conductor, connected to three electric conductor circuits, producers of bubbling gas.

FIG. 4A shows a perspective view of the electricity supply conductor, connected to three electric conductor circuits, producers of bubbling gas, in which the supports for their mounting and attaching to the supporting structure of insulating material are shown.

FIG. 4B shows a perspective view of the electricity supply conductor, connected to three electric conductor circuits, producers of bubbling gas, in which the insulated and uninsulated sectors of those conductors are shown.

FIG. 5 shows a perspective view of the electricity supply conductor connected to two electric conductor circuits, producers of bubbling gas.

FIG. 6 shows a perspective view of the electricity supply conductor connected to a circuit of electrical conductors, producer of bubbling gas.

FIG. 7 shows a perspective view of the electricity feed conductor for the circuits of the electrical conductors, producers of bubbling gas.

The numbers indicated in the figures have the following meaning:

• 1. Connection for the feeding of fresh electrolyte.
• 2. Upper end of the vertical guide of anodes and cathodes.
• 3. Cradle for connection to the crane with which the electrolytic cell is installed or removed from the supporting structure of insulating material.
• 4. Inferior guide to fix the position of the bottom of the anode.
• 5. Inferior guide to fix the position of the bottom of the cathode.
• 6. Upper frame of the support structure of insulating material.
• 7. Lower frame of the support structure of insulating material.
• 8. Insulated conductor for feeding electricity to the circuits that produce gases by electrolysis.
• 9. Anterior circuit of electrical uninsulated conductors for the production of bubbling gas.
• 10. Intermediate circuit of electrical uninsulated conductors for the production of bubbling gas.
• 11. Rear circuit of electrical uninsulated conductors for the production of bubbling gas.
• 12. Electrical connector for feeding the anterior circuit of electrical uninsulated conductors, for the production of bubbling gas.
• 13. Electrical connector for feeding the intermediate circuit of electrical uninsulated conductors, for the production of bubbling gas.
• 14. Electrical connector for feeding the rear circuit of electrical uninsulated conductors, for the production of bubbling gas.
• 15. Bracket to the frame of the supporting structure of insulating material.
• 16. Insulated section of the electrical conductor that produces bubbling gas.
• 17. Uninsulated section of the electrical conductor that produces bubbling gas.

DESCRIPTION OF THE INVENTION

This invention consists of fixing one or more circuits that supply electricity to one or more circuits of electrical uninsulated conductors, or with localized sections of insulation, which are located in the inferior zone of the electrolytic production cell, or to a support structure of anodes and cathodes of insulating material, independent of the production cell, which can be removed and installed in it, with or without the anodes and cathodes already placed in the guides of the support structure.

In one of its embodiments, and without this meaning the limiting of the generality of the invention, a circuit of insulated electricity supplying conductors (8) has been attached on the outside and on one side of a support structure of anodes and cathodes, built of electrically insulating material, inside which a plurality of anodes and cathodes are placed, while underneath the inferior frame (7) of the support structure, one or more circuits of electrical uninsulated conductors or with localized sections of insulation (16) have been attached, that link the electricity supplier (8), by means of connectors (12, 13 and 14) to the circuits of uninsulated conductors or with localized sections of insulation (9, 10 and 11).

In another of its embodiments, in a traditional cell for the electrolytic production of metals, the insulated conductor(s) that supply electricity are fixed to the vertical walls of the cell, while the electrical circuit(s), uninsulated or with localized sections of insulation, are fixed directly to the floor of the cell.

The circuit(s) of electrical uninsulated conductors or with localized sections of insulation can be built of either single thread solid wire or multiple thread wire, of metal covered with a mixture of metal oxides (known in the English language as MMO, short for “Mixed Metal Oxide”).

The application of electrical pressure between cathodes and the circuits of uninsulated conductors or with localized sections of insulation (9, 10 and 11), in such a way that these circuits remain at a positive pressure with regard to the cathodes, causing an electrolysis of the water of the electrolyte, generating oxygen in the periphery of the conductors that are uninsulated or have sections of insulation. The oxygen becomes detached in the form of very small bubbles, which ascend between anodes and cathodes or only underneath the cathodes if conductors are employed that have localized sections of insulation underneath the anodes, producing a more global or more localized stirring of the electrolyte, respectively.

The number of bubbles can be controlled by modifying the voltage or the current applied between cathodes and the circuits (9, 10 and 11) of conductors that are not insulated or that have localized sections of insulation (16).

It becomes evident that the cleaning of the insulated feed conductors as well as that of the uninsulated conductors or those with localized sections of insulation (16), if it should be necessary, can be executed very simply, at the end of the production cycle, decreasing losses in production time in this respect.

EXAMPLE OF APPLICATION

As an example, and without this limiting the generality of the invention, in a traditional cell for electrodepositing copper, measuring six and a half meters in length by 1.2 meters wide and 1.5 meters deep, a support structure of insulating material will be introduced built of plastic reinforced with fiberglass, with guides for anodes and cathodes of insulating material, loaded with 61 insoluble anodes measuring 1200 millimeters high by 800 millimeters wide, with support flaps to the conductor bar and 60 stainless steel cathodes measuring 1140 millimeters high and 880 millimeters wide, spaced at 95 millimeters between centers.

Once the supporting structure of insulating material of the cell is introduced, with the anodes and cathodes mounted; with the insulated conductor for feeding electricity (8) and the circuits of uninsulated conductors or with conductors with localized sections of insulation (9, 10 and 11), fixed to the bottom frame of the supporting structure by means of the respective supports (15), the pipe for the circulation of electrolyte is connected to the connection (1) and the electric power is connected to start production operation.

The uninsulated electrical conductors or the conductor with localized sections of insulation, are made of titanium coated with a mixture of metal oxides 3 mm in diameter.

The electrolyte is circulated at a flow between 10 and 30 cubic meters per hour and the electric power is supplied at a potential of 1.7 to 2 volts between the circuits of uninsulated conductors or with conductors with localized sections of insulation (9, 10 and 11) with regard to the potential of the cathodes. This difference of potential produces the liberation of oxygen on the surface of the uninsulated conductors or in the conductors of localized insulation (16).

The ascension of the gas from below the anodes and cathodes, or only from below the cathodes for the conductors with sections of insulation located underneath the anodes, stirs the electrolyte, improving the uniformity of its concentration, reducing the boundary layer and thus improving current quality and efficiency of the metal deposition.

When the deposit on each side of the cathode reaches about three millimeters, the operation will be detained, the cathodes removed, clean cathodes loaded and the operation will be restarted.

These cycles will be repeated until the bottom of the cell has to be stripped, on which occasion the complete support structure of anodes and cathodes will be removed and replaced by another equivalent one, prepared beforehand, restarting a new cycle of production.

With this procedure, the ventilators and the feed and distribution circuits of stirring air are replaced only by the electrical conductors as the electric power to energize the circuits of uninsulated conductors or conductors with localized sections of insulation can be obtained from the same source that is used for the production of metal.

Maintenance time is reduced, in relation to the maintenance of the ventilators and pipes for supplying and distributing air. At the same time, the chemical and physical quality of the cathodes is improved, their dimensional uniformity and therefore, their weight dispersion are reduced and the energy efficiency improves.

Claims

1. Equipment for stirring electrolyte in cells for the electrolytic production of traditional metals, or that use removable supporting structures of anodes and cathodes, CHARACTERIZED in that they have one or more insulated conductors for supplying electricity, fixed to one side of the cell or of a removable supporting structure of anodes and cathodes, and connected to one or more circuits of uninsulated electrical conductors or with localized sections of insulation, located underneath the anodes and cathodes of the cell and fixed to the removable supporting structure of anodes and cathodes, or to the bottom of the traditional cell for electrolytic production of metals.

2. Equipment for stirring electrolyte in cells for the electrolytic production of traditional metals, or that use removable supporting structure of anodes and cathodes, according to claim 1, CHARACTERIZED in that uninsulated electrical conductors or with localized sections of insulation are manufactured of titanium or another similar metal, covered with mixed metal oxides.