FI68430B - KATOD FOER ELEKTROLYTISK RENING AV KOPPAR - Google Patents

Description

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C Patent granted on 10 09 1985

Patent applications (51) Kv.ik.4 / int.ci. * c 25 C 7/02 FINLAND —FINLAND (21) Patent application - Patentansöknlng 800337 (22) Application date - Ansökningsdag 04.02.80 <F ») (23) Starting date - Giltighetsdag 04.02.80 (41) Tullut {outside sex - Bllvlt offentlig q £ gg gg

National Board of Patents and Registration / 44) Date of display and publication. - No ος

Patent and registration authorities in the United States of America and the Publications Office> · up · ° 3 (32) (33) (31) Pyydetty etuoikeus - Begird prloritet 05.02.79

Australia-Australien (AU) ** 3909/79 Verified-Styrkt (71) Copper Refineries Pty. Limited, Box 5 ** 84 M.S.O., Townsville,

Queensland 4810, Australia-Australia (AU) (72) lan James Perry, Townsville, Queensland, Australia-Australia (AU) (7 **) Esko Friman (5 **) Cathode for electrolytic copper cleaning -Cathode for electrolytic refining This invention relates to a cathode used in the electrolytic cleaning of copper.

For fifty years to this day, the most commonly used cathode of the type in question has been in the form shown in Figure 1 of the accompanying drawings in a perspective schematic view.

As shown in Fig. 1, the previous type of cathode is formed by a copper support rod 7, a copper seed plate 8 and two copper loops or brackets 9 on which the plate is suspended on the rod. The end portions of the rod 7 extend beyond the width of the plate 8 so that they can rest on the pool sides for support, making normal electrical contact, and the seed plate is between a pair of unrefined copper anode plates both embedded

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Despite their long use in industry, it has been well understood that previous cathodes have remarks in many respects. For example: a) Copper Seed Plates are not reusable. This means that the copper deposited on them cannot be removed and then injected back into the cell to receive a new copper layer. The current and most profitable method is to smelt a pair of seed plates together with copper deposited thereon and make conductor copper, ingots, ingots, ingots and other copper products of fair quality from the copper smelt. Part of the molten product could be used to make new seed sheets, however, experience has shown that it is more economical to make new seed sheets electrolytically; even in this case, the consumption of man-hours is very high because it involves removing the seed plates from the mother plates, smoothing them and fixing the loops, and installing the plate with the loops in the support size.

b) Copper seed plates are not easy to make really flat and although they are substantially flat in the initial stage, they often twist in use and this increases the short circuits between the cathode and the anode. Even where the lack of uniformity is not so bad, deviations from the parallelism between the cathode and the anode cause unevenness in the copper layer, with overlaying at "points" or near each other accelerating short circuits at those points. Short circuits are a serious problem because it is necessary to use a group of men whose sole job is to patrol the electrolysis hall to repair short circuits.

c) Sometimes the loops 9 hardly form anything other than line or even point contact with the support rod 7. This does not impair the copper deposition process itself, but it increases the resistance and thus the power cost increases.

In the copper industry, in-depth studies have been carried out 3,68430 and experiments have been carried out to improve the motherboards with which the Seedboards are made. A few attempts were made with stainless steel, but in general they failed due to inconsistencies in the results, which revealed problems such as passivity, localized corrosion, and varying adhesion of the copper layer.

Titanium cathodes have become quite popular due to the inherent properties of titanium, which provide an oxide film that appears to be well suited to overcome the problem of too little or too much adhesion of the copper layer and has exceptionally good corrosion resistance. The most advanced form of titanium, reusable cathode is a combination comprising a combined support bar consisting primarily of copper and an associated titanium component to which a titanium cathode plate is welded. In one form, the support rod is a copper rod rod enclosed in a titanium shell, and the upper portion of the cathode plate is formed as a gooseneck so that that portion can be welded directly to one side of the suspension rod housing. In another form, the support rod is a copper rod having a titanium core rod inside it longitudinally with respect to it. In this case, the cathode plate is bent into a goose neck as above and welded to the core bar by short pins of titanium, the pins piercing through holes in the copper bar and one end of each pin welded to the core bar and the other end welded to the edge of the cathode plate.

An example of the known "titanium" device described above is disclosed in GB Patent 1,415,793.

However, titanium is not without flaws. It is expensive and practically complicated to manufacture. The original object of the present invention was to overcome or remedy at least some of the above-mentioned drawbacks, and in the best embodiment all these drawbacks in a particularly simple and inexpensive manner using a completely stainless steel cathode must be unrestrictedly reusable, maintain uniformity, provide uninterruptible current and between this rod and the plate, forms a permanent oxide film which acts as an effective separating layer, facilitating the removal of deposited copper from the cathode while providing sufficient adhesion to fix the deposited copper during construction, and is particularly suitable for mechanical processing in its manufacture and use.

The experimental use of the invention has proved to be so successful that it has been considered economical to extend the use of this cathode to the entire copper electrolysis hall of the applicant.

The conventional cleaning method utilizes motherboards in a certain number of cells to produce two thin sheets of refined copper from each sheet each day. These plates are then mounted on the cathodes shown in Figure 1.

A particular seed disc manufacturing operation involving additional inspection, higher power consumption per tonne of product, and significantly labor costs can be eliminated by using this invention in all cells and a longer growth time (a week or more instead of just 24 hours) prior to removal. It thus produces a suitable electrode for mechanical treatment and mechanical removal, the product of which is commercially pure cathode copper.

In addition, the precise dimensions of the cathode, together with the precisely dimensioned anodes, make it possible to operate at a shorter electrode spacing and thus significantly reduce power costs, and most importantly, largely eliminate short circuits and thus reduce additional labor costs and facilitate short circuit computer monitoring. In addition, more efficient operation, made possible at shorter distances, and a higher current density at which the cleaning operation can be performed due to short circuit removal mean that equipment for a given annual production can be housed in a smaller building, providing significant capital investment savings for that building.

By eliminating the Seed Plates and the special 5 5,8430 clearance required by them, the anodes and in particular the tendency to short-circuit are reduced in the process by constantly circulating the amount of copper. While this reduction can be as much as 20¾ let’s say 10,000 tons, the amount of money invested in the copper in the process is greatly reduced. To achieve this, the invention is characterized by the features set out in claim 1.

A preferred embodiment of the invention is illustrated in Figures 2-6.

Figure 2 is a perspective view of a cathode not shown in proper proportions.

Figure 3 is a side view of the same cathode.

Figure 4 is an end view as a projection of Figure 3.

Figure 5 is an enlarged view of the part of Figure 4 indicated by the number 5.

Figure 6 is a section taken along line 6-6 on an even larger scale.

Referring to Figures 2-6, the stainless steel support bar 11 preferably has a so-called cross-section. RSJ beam or I-beam as shown. It could be some other profile but the one shown is the best because it is light in weight and therefore economical steel product. It is structurally advantageous and forms a relatively large surface area for the current to be transported. The rod 11 has a flat lower surface 12 and the end portions 13 are adapted to rest on brackets and electrical wires as is known.

The flat stainless steel cathode plate 14 is welded as shown at 15 in Figure 5, attached at its upper edge to the lower surface 12 so that the plate extends vertically from the lower surface 12. The plate 14 preferably has a pair of openings 16 made therein before welding. These openings facilitate the mass handling of the cathode array when inserting support arms or fork arms through the openings.

A number of stainless steels can effectively serve as cathode plates for this purpose, but to facilitate the removal of copper, it is recommended to use a grade of stainless steel marked "AISI 316 ELCM" with a surface treatment known as Standard 2B. composition: carbon 0.03% by weight nickel 12.0 chromium 17.0 - "- molybdenum 2.25 -" - and the 2B surface treatment is between glossy and opaque, and is silver gray, the semi-gloss surface being made by cold rolling, by softening and pickling, and then by light final rolling with polished rollers.

The steel and surface treatment shown have been considered the best because experiments have shown that they provide sufficient adhesion between the steel plate and the copper deposited thereon to prevent the copper from peeling or detaching from itself; however, this attachment is not such as to prevent the finished copper layer from being detached from the steel plate. Removal can be performed using knife-like blades or knife-blade wedges inserted between a steel plate and layered copper at the top of the copper; however, using the above type of stainless steel and surface treatment, our experiments have shown that effective removal can be accomplished automatically by passing copper-charged cathodes through a hammering station where the deposited copper is tapped tightly near its top on both sides, several air jets into a very small gap between the detached top of the steel and the copper.

The stainless steel from which the support bar is made may be the same as from which the plate is made. However, the rod may be made of some other stainless steel, provided that it is one to which the plate can be welded.

As mentioned earlier herein, stainless steel is not a particularly good conductor, and the use of a support rod, 7 68430 made of steel alone, is not sufficient to carry current between the open rail and the cathode plate. It has been found that this can be simply overcome by coating the support rod and the upper edge of the plate welded to it with copper. This coating can be performed by a known coating technique and a thickness of about 1 mm is considered best to provide sufficient electrical conductivity and the ability to resist corrosion. It should be mentioned that in the past here, the presence of an oxide film on the motherboard has been considered desirable due to the fact that it acts as a separating layer to facilitate the separation of copper from the sheet;

The width of the copper-coated edge at the top of the motherboard is not critically determined, it terminates slightly above the surface of the electrolyte. Obviously, copper need not be allowed to deposit on the coated surface. Likewise, the plate surface on which pure copper is deposited during operation need not extend to the lower edges 17 defining the openings 16. It follows that the copper plating may terminate just before the edges 17 and arranged to cover the (preferably sandblasted) weld metal at 15 .

It is clear that facilitating the separation of the copper requires effective delimitation of the edges of the cathode plate so that the copper layer does not continuously extend around these edges. This is especially true for the vertical side edges of the disc. The bottom edge does not so need cropping and from this edge the cropping can be omitted; however, to improve the reliability of the release, we prefer to cover the bottom edge only by giving it a hot dip to a depth of about 10 mm with a high melting point flexible wax or other coating material.

With respect to the delimitation of the side edges of the cathode, the present invention expresses an important additional advantage over the aforementioned titanium plates.

In cathodes made of titanium, due to the relatively high conductivity of this metal, there is a tendency for the deposited copper particles to flow under the delimiting strip material.

When this occurs, the copper inclusions continue to grow under the trimming strip (usually of plastic material) and thus tend to elevate the strip and thus nullify the purpose of the trimming and thus create the need for re-trimming before further use.

With stainless steel cathode plates, the relatively poor conductivity prevents copper growth under the delimiting means, and such growth is thus reduced to an amount that is quite negligible.

Nevertheless, effective delimitation is still desired, at least on the side edges of the cathode; and we think the best delineation method we use is best shown in Figure 6.

Referring mainly to this figure, the delimiting means comprise a longitudinally notched plastic strip fixed to the plate 14 by plastic pins 19. These pins insert through holes 20 made in the plate 14.

The strip 18 and the pins 19 are preferably made of the same plastic material, and a suitable material is a high quality, heat and impact resistant plastic known as CYCOLOY 800. This is a polymeric blend of acrylonitrile-butadiene-styrene (ABS) and polycarbonate as described in the U.S. patent. 3130177.

The strip 18 and the pins 19 are attached to each other using a suitable binder, such as a 30 L solution of Cycoloy 800 in methylene chloride.

Such a binder solidifies elasticly and, in addition to acting as a binder, serves a useful purpose in the following manner.

During the experiments that led to this invention, it was found that in a few situations, the moldings tended to have a slight bulge between the pin attachments. This was, of course, unpleasant and was attributed to the expansion gap between the steel and the molding. This situation was corrected by making the holes 20 oversized, as shown in Figure 6. When the strips and pins are used, the holes 20 are filled with a solvent 9 68430 which solidifies into an elastic state to act as an expansion joint, allowing sufficient longitudinal movement of the strip relative to the cathode plate.

The strips are preferably first formed by extrusion or injection molding, and at this stage it is desirable that the points 21 defining the opening of the gap 22 are located closer to each other than shown in Fig. 6. This is because when the strip is mounted on the plate, the edges of the slot 22 themselves have a resilient tendency to compress them into contact with the plate.

As an additional precaution, the dots 21 are best sealed with respect to the cathode plate by placing a sealing strip of wax or other material, as indicated by the number 23.

Claims (9)

A cathode for use in electrolytic refining of copper, which cathode comprises a support bar (11) having a planar lower surface (12) and end portions (13) arranged to rest on supports and electrical contacts, and a starter plate (11). 14), which is of stainless steel and fastened by welding with its upper edge, characterized in that the support bar (11) is of stainless steel and the starting plates (14) of stainless steel are fixed by welding at the lower surface (12) of the end portions. (13) and extends vertically downwardly from said lower surface (12) and a copper coating encloses the support bar (11) and at least the upper edge portion of the starter plate and that the starter plates (14) comprise devices for covering at least the vertical side edges. 2. A cathode according to claim 1, characterized in that the support bar (11) corresponds in its cross-sectional shape to an I-beam. A cathode according to claim 1 or 2, characterized in that the starting plates (14) have lift heels formed therein by openings (16) at the edge of the starting plates (14) with which the plates (14) are welded to the support bar (11). ). Cathode according to any of the preceding claims, characterized in that said copper coating is formed by electroplating. Cathode according to any of the preceding claims, characterized in that said covering means comprise plastic strips (18) which have a longitudinally extending latch into which the strip (18) encloses the plates (14) and a number of plastic pins (19). ), which protrude through the shark (20) into the plates (14) and portions thereof are arranged on each side of the latch and connected to the strip. 6. A cathode according to claim 5, characterized in that the strip (18) is formed by extrusion and the pins (19) are mounted in this manner in such a way that the sides of the groove are