US20160060780A1

US20160060780A1 - Reusable anode system for electrorefining processes

Info

Publication number: US20160060780A1
Application number: US14/768,022
Authority: US
Inventors: Pablo Suarez Loira; Daniel Cuchacovich Mikenberg
Original assignee: ASESORIAS Y SERVICIOS INNOVAXXION SpA
Current assignee: ASESORIAS Y SERVICIOS INNOVAXXION SpA
Priority date: 2013-02-14
Filing date: 2013-05-06
Publication date: 2016-03-03
Also published as: WO2014125341A1; CL2013000447A1; JP2016507011A; BR112015019529A2; PE20151440A1; MX2015010451A; CN104995338A; DE112013006672T5

Abstract

A reusable anode system for electrorefining processes allows eliminating the excess or scrap and generating a continuous electrorefining process having an increased contact surface between the anode and the electrolyte which comprises: a container (10) which is made of stainless steel and having the shape of a straight thin rectangular parallelepiped which on its front and rear faces has a plurality of holes (11) allowing the communication between the outside and inside in such a way the electrolyte is able to enter the container (10) wherein the upper portion of the container (10) is projecting higher than the position of the electrical contact bars (12, 13) by means of projections (16) extending the inside (15) of the container (10) to form an unloading and loading zone and (b) a plurality of copper bars (14) coming from an extrusion and wire drawing process is grouped inside (15) of the container.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a national phase application based upon priority International PCT Patent Application No. PCT/IB2013/053635, filed May 6, 2013, International Publication No. WO 2014/125341, published Aug. 21, 2014 which is based upon priority Chile Patent Application No. C1447-2013 filed Feb. 14, 2013.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a reusable anode system for electrorefining processes, constituted by a container which is made of stainless steel and shaped as a straight thin rectangular parallelepiped having on its front and rear faces a plurality of holes communicating the outside and the inside in such a way the electrolyte is able to enter said container. In the upper portion, the container projects higher than the position of the electrical contact bars, by means of projections extending the inside the container to form an unloading and loading zone for a plurality of copper bars. The copper bars coming from an extrusion and wire drawing process are grouped inside the container, thus forming the anode system of the present invention. This system allows eliminating the excess or scrap of traditional processes of the previous art.

BACKGROUND OF THE INVENTION

The production process of high-purity copper involves several stages, starting with the reception and sampling of copper concentrates. It is important to do a sampling thereof by classifying them according to the concentration of copper, iron, sulfur, silica and impurities such as arsenic, antimony and zinc mainly.
Subsequent to the classification stage, the concentrate enters into the drying stage wherein the humidity is reduced from 8% to 0.2%, then the dried concentrate enters into the fusion process, whose objective is to achieve a change of state which allows the concentrate to pass from a solid state to a liquid state so as the copper can be separated from the other elements comprising the concentrate.
The copper concentrate fusion is a product of the instantaneous auto-ignition thereof, which takes place at high temperatures (greater to 1200° C.). In this process the concentrate passes from the solid state to the liquid state, the elements comprising the ores present in the concentrate are separated according to their weight, remaining the lighter ones on the upper part of what has been smelted (molten metal) which is called slag, mainly phases containing high contents iron and silica, while the copper associated to sulfur which is heavier, is concentrated on the lower part of the reactor, which is called Babbitt metal or bearing metal. Thus, it is possible to separate both parts by taking them out from the reactor by means of tapping passages located at different levels.
Fusion reactors and furnaces must be constantly loaded and permanently tapped, the material having high content of copper is carried in liquid form through pots or channels to the conversion process where a high copper phase called blister copper is produced (98.5 Cu). This product is subsequently carried in liquid form through pots or channels to a refining process where are mainly removed impurities such as dissolved sulfur, dissolved oxygen and impurities such as arsenic, antimony, bismuth, lead among others, in such a way that finally it is possible the obtaining of the product called anode copper with an average purity of 99.5% of copper.
The anode copper is molded and solidified with a rectangular geometry, forming an anode plate (1) having ears (2) as showed in FIG. 1. The most used form to cast the anode copper, is by means of a casting wheel, which comprises a determined quantity of copper molds, wherein copper is poured at a temperature lower or equal to 1200° C., once the copper is poured into the casting Wheel, the latter starts to spin and the smelted copper begins to cool off in a first stage at ambient temperature until the upper part of the copper is solid, subsequently the copper passes by a cooling stage which comprises upper water cooling and lower water cooling. In this stage the copper decreases its temperature until reaching a complete solid state, to be carried to the electrolytic refining plant in order to produce a high-purity cathode having copper contents higher or equal to 99.9% Cu.
The anode copper is formed on a mold (7) which comprises a central rectangular-shaped cavity (8) for receiving the liquid copper which forms the anode plate (1). On the upper part of said mold (7) and towards the corners of the central cavity (8) are located two cavities (9) for receiving the liquid copper which comprises the ears (2) as can be seen in FIGS. 6 and 7.
In the refineries, the anode (1) is introduced in an electrolytic cell (3) which has a cathode (4) that can be permanent or of mother sheet according to the technology to be used, having its respective hanging bar (5). The electrolytic cell (3) is filled with an acid solution and current is applied to the contacts (6) in order to produce the electroplating of copper from the anode (1) towards the cathode (4) according to what is shown in FIGS. 2 to 5. In this process, the anode (1) only remains submerged up to the continuous zone of the ears (2) and due to this, the upper part of the anode (1) does not participate in the electrolysis process as shown in greater detail in FIG. 3, thus using the ears (2) only to transport the same and for electrical contact.
When finishing the electrolytic cycle, this part of the anode remains intact and becomes an important part of the rest of the anode, together with the undisolved material, called scrap. This material must be again smelted to form a new anode (1) and continuing with the complete cycle. This product is formed in all the existing refineries and the reprocessing cost is high which is performed by means of different technologies existing in the market.
The present invention proposes completely eliminating the excess of scrap by means of the substitution of the molten and molded copper as an anode (1) with ears (2) by copper shaped as bars coming from an extrusion and wire drawing process which guarantees a surface quality and homogeneity of the copper bar.
In order for these copper bars to be electro-refined, the present invention proposed the utilization of an anode system which comprises a bars container having on its upper portion two projections for the electrical contact in the form of ears and on its front and rear faces having a plurality of holes which allow the communication between the outside and the inside of said container, in such a way the bars are in contact with the electrolyte.
There have been several attempts in the state of the art to minimize the residues or scrap being produced by anodes coming from a casting process and which then pass to an electrorefining stage. Thus, for example, document CL 41874 published on Jul. 25, 2000, discloses a process to recover residues from copper anodes, by reusing them directly on the casting mould to manufacture new anodes by means of casting. In this document, it is indicated that currently the worn-out residues of copper mother anodes, extracted during the electrolytic processes are not reused in the same process and preferably are completely used as raw material in the casting of copper to manufacture new “copper mother anodes” which subsequently return to the process, housing them in the electrolytic cells as new pieces for the production of copper cathodes. This operation generates an additional cost when performing again the remelting, which makes the final product more expensive. A great percentage of these pieces (worn-out copper mother anodes) remain in good condition right on the upper zone, wherein the electrical contact is produced in the electrolytic cells. This fraction of the piece constitutes an important saving as regard to the material, therefore, it has a great impact in the manufacturing cost of new “ copper anodes”. The saving is then generated by recovering and/or reusing the “worn-out copper mother anode” after having completed its working cycle in the electrolytic process, by using all or part thereof, as a whole perforated and/or bent insertion or part thereof, in such a way it is a constituent part of the “new copper mother anode” when placing it on the mold and pouring liquid metal above the insertion by filling it up to complete a new piece, which after being cooled off can be demoulded to be used.
On the other hand, there have been attempts to reduce the excess or scrap by means of the use of hanging bars with anodes being hung from these bars. Thus, for example, document EP 0284128 published on Sep. 28, 1988 discloses a suspension bar for anode or a cathode sheet in the electrolytic refining of metals wherein the core of the suspension bar consists of a material which exhibits a high resistance to bending and a high mechanical resistance, and being surrounded by a sheath of a material with good electrical conducting properties. This material having good electrical conducting properties such as copper, near at least one of the ends of the suspension bar and preferably near both ends, over a length of at least 3 cm and at most 5 cm, the sheath being continuous to the end of the core. In addition, this document, discloses a method for the manufacture of a suspension bar in which a sheath of copper is drawn over a core of steel, starting from copper tube. Copper and steel cores are introduced into the copper tube, subsequently the sheath is drawn with further cores being added, to a total length which essentially corresponds to the change in length of the copper tube occurring as a result of the drawing and, finally, the rod produced is sawn up into the desired rod lengths at the points where the copper cores are located. Towards the center, the bar has two hooks to suspend an anode or cathode as the case may be.
None of the previously mentioned documents discloses an anode system comprising: A bars container; and b) a group or set of copper bars allowing the elimination of the produced excess or scrap.

SUMMARY OF THE INVENTION

The present invention refers to an anode system comprising a bars container and a group or set of bars forming a reusable stainless copper anode manufactured in such a way that its structure is a container for copper bars which are stacked inside thereof. The general shape of this assembly is similar to the format of a smelted copper anode, both in mass and configuration, but when being formed by cylindrical solid bars, the total surface of the set of bars is by a 40% greater than its equivalent in a flat smelted anode.
Since the copper in the electrorefining process must be dissolved in the electrolytic solution by using a great amount of electric energy, the increased surface has an impact in the speed of dissolution which is faster due to the greater surface of copper in contact with the electrolyte and for this reason when being faster, it is necessary to use a smaller amount of energy in order to achieve the same amount of refined copper deposited on the cathode.
Another advantage of this configuration is that as these bars are dissolved, they decrease their diameter, therefore they start compacting and being gathered in groups. As long as the system remains charged with copper bars stacked on the upper part, which due to the weight start tightening and compacting the assembly, a constant dissolution of the bars will take place without the existence of copper excess or scrap. In this way, the electrorefining process can be maintained in a continuous way as the container is reload with copper bars.
Another advantage of the use of bars as anode copper mass lays in that the manufacturing process of bars involves an extrusion and wire drawing process which guarantees a surface quality and homogeneity of the copper bar. This surface quality is not feasible of being achieved by means of the current casting processes of smelted copper on open moulds.
Due to the aforementioned, an object of the present invention is providing a system which allows completely eliminating the excess or scrap from the anodes processed in an electrorefining cell.
Another object of the present invention is providing a system which allows a continuous electrorefining process by means of the reload of the containers of bars with new bars to be processed.
Another object of the present invention is generating a contact surface of the anode with the electrolyte which is increased by a 40% with respect to the anode surfaces of the previous art.
A more detailed description of the invention is provided in the following description and appended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures are included to provide a better understanding of the invention. They are part of this description and serve to explain the principles of this invention.

FIG. 1 shows a perspective view of an anode according to the previous art.

FIG. 2 shows a perspective view, according to the previous art, of an electrolytic cell, having the anode and cathode inserted therein.

FIG. 3 shows a perspective view, according to the previous art, of an electrolytic cell having the anode and cathode risen above the acid solution (electrolyte).

FIGS. 4 and 5 show a perspective view of an electrolytic cell, according to the previous art, having the anodes and cathodes submerged in the acid solution (electrolyte).

FIG. 6 shows a front elevation of a casting mold to form an anode according to the previous art.

FIG. 7 shows a perspective view of a casting mold to form an anode according to the previous art.

FIG. 8 shows an exploded perspective view of the constitutive elements of the system of the present invention formed by a container and copper bars.

FIG. 9 shows a perspective view of the system of the present invention wherein the copper bars are inside the container.

FIG. 10 shows a schematic sectional view of the system of the present invention within an electrolytic cell wherein the bars are inside the container.

FIG. 11 shows a schematic sectional view of the system of the present invention within an electrolytic cell wherein the bars are fed towards the container.

FIG. 12 shows a perspective view of a cell for the copper electrorefining with the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description and explanation of the preferred embodiments and best modes contemplated by the applicant and inventors of carrying out the invention.
The present invention relates to a reusable anode system constituted by a container (10) which is made of stainless steel and shaped as a straight thin rectangular parallelepiped having on its front and rear faces a plurality of holes (11) which allows communicating the outside and the inside in such a way that the electrolyte is able to enter said container (10).
In the upper portion, the container (10) projects higher than the position of the electric contact bars (12, 13) by means of projections (16) extending the inside (15) of the container (10) to form an unloading and loading zone of a plurality of copper bars (14).
The copper bars (14) coming from an extrusion and wire drawing process are grouped inside (15) the container (10), thus forming the anode system of the present invention. These bars (14) are shaped as cylinders having a circular cross section.
With the surfaces (17) of the plurality of copper bars (14) it has a wavy shape being formed by the plurality of semi-cylinders, said surface is greater by a 40% than the surface of the anodes of the previous art.
The anode system comprising a container (10) and the set of bars (14) located inside (15) of said container (10) is submerged in the electrolyte within an electrolytic cell (3).
As the electrorefining process moves forward, the bars (14) start decreasing their diameter and deposit at the bottom of the container (10) thereby causing that the bars (14) being on the upper part of the container (10) are displaced towards the bottom portion of said container (10).
This allows the container (10) to leave an empty space on the upper space where more bars (14) can be loaded in such a way of generating a continuous process without removing the anode system of the present invention from the electrolytic cell (3).
The bars (14) whose diameter has decreased are deposited at the bottom of the container (10) until disappearing which leads to the elimination of the excess or scrap.
Although embodiments and examples of the invention have been shown and described, it is to be understood that various modifications, substitutions, and rearrangements of parts, components, and equipment, can be made by those skilled in the art without departing from the novel spirit and scope of the invention.

Claims

What is claimed is:

1-5. (canceled)

6. A reusable anode system for continuous electrorefining processes comprising:

(a) a container which on its front and rear faces has a plurality of holes; and

(b) a plurality of copper bars;

characterized in that:

said container is made of stainless steel and having the shape of a straight rectangular parallelepiped, which upper portion projects higher than the position of the electrical contact bars by means of projections extending the inside of the container to form an unloading and loading zone, said upper portion of said container having an empty space wherein said plurality of copper bars are loaded; and

said plurality of copper bars coming from an extrusion and wire drawing process, which are grouped inside of said container, wherein said plurality of copper bars forms a surface of wavy shape, and wherein each bar of said plurality of copper bars has a shape of cylinder having a circular cross section and that has a decreased diameter at the bottom of the container.