EP0017085A1 - Process and apparatus for electro-depositing metals, in particular copper - Google Patents

Abstract

Method and apparatus for electrolytically separating metals utilizing cathode sheets and anode sheets mounted in an electrolyte, the distance between the sheets being regulated, and may be variable as separation proceeds. The invention is also directed to an anode-cathode spacing device including improved electrically insulating spacing elements.

Description

The invention relates to a method for the electrolytic deposition of metals, in particular copper, in which cathode sheets, in particular thin starting cathode sheets, are used between anodes in the electrolytes at the beginning of the electrolytic deposition.

In the electrolytic refining and extraction of metals, in particular copper, a large number of anodes and cathodes are used in plate form or plate form in electrolyte baths, so that the metal can be deposited on the cathode plates or plates. To increase the separation efficiency, the anodes and cathodes are arranged as close to each other as possible. As is known, the short distances between anode and cathode lead to short-circuits between anode and cathode from time to time, which reduce the current efficiency and lower the deposition performance.

In order to prevent short circuits, it is known, for example from German Offenlegungsschrift 25 08 094, to guide the cathode sheets at their edges in holders made of non-metallic material. The investment that results from these brackets is, however pregnant. In addition, the marginal zones that are covered do not participate in the deposition.

It is an object of the invention to provide an electrolysis process and a device for carrying out the process, which considerably reduces the outlay required in the known mounting, allows the use of the entire cathode surface and is also particularly suitable for thin cathode sheets, which e.g. can be obtained by using a thin layer, likewise electrolytically deposited on a mother plate, which was subsequently removed from the mother plate, as the cathode plate. The space-time yield and the current yield are to be increased and the energy consumption is to be reduced.

The object is achieved in that the cathode sheets are spatially fixed in the electrolyte. The spatial fixation, in contrast to the known line fixation by clamping the edges, ensures that even a thin cathode cannot move, which would result in parts of the cathode contacting the anode. In this way, the safety of the electrolysis process is increased so significantly that it is possible to dispense with continuous monitoring of the electrolysis process for short circuits. The current yield increases, the residual anode quantity decreases.

In an embodiment of the invention it is provided that the spatial fixation takes place by defining individual points or small areas of the cathode surface. It is hereby advantageously achieved that the effort compared to a complete spatial fixation, e.g. through a grid, can be significantly reduced.

Surprisingly, it has been found that the number of fixation points or areas can be very small without losing the desired effect of sufficient spatial fixation.

In a further embodiment of the method it is provided that the cathode sheets are fixed by indirectly supporting the cathode sheets on the anodes. This configuration advantageously makes it possible to dispense with a system for fixation that is rigid in the horizontal direction, since the support in the direction of warpage, i.e. perpendicular to the cathode surfaces, is made by the stable anodes. It is only necessary to fix the fixing points vertically between the anodes and cathodes. A lateral fixation of the cathode sheets is unnecessary.

In a further embodiment of the method it is provided that the fixing points or areas are unevenly distributed on the two sides of the cathode sheet. In this way, the number of fixation points can advantageously be reduced further. The unequal distribution is possible because it has surprisingly been found that the tendency of the cathode sheets to bulge or move is the same for all cathode sheets which have been produced by the same production method. This is particularly the case if a precise straightening process after the production of the cathode sheets is dispensed with in a cost-saving manner, that is to say they are largely left in the raw state.

It is further provided that the fixing points or areas are distributed asymmetrically on the individual sides of the cathode sheet. This advantageously takes into account the fact that the upper side of the cathode sheets are already sufficiently fixed relative to the anodes by means of ear straps and holding rods. It is sufficient, for example, if the side of a cathode sheet which tends to bulge is provided with one to three fixings in the central region and the opposite side is provided with two fixings approximately at the lower edge. These unequal and asymmetrical fixations, combined with the tendency of the cathode sheets to move in one direction only, result in a surprisingly sufficient, in spite of the simplicity, sufficient, very cost-saving spatial fixation which prevents the cathodes and anodes from touching.

In a further embodiment of the invention it is provided that the position of the fixing points or areas is changed during the deposition process. This advantageously ensures that the fixing elements cannot grow into the deposited layer. A relatively slight change in position is sufficient, in particular when fixation elements which are largely in punctiform contact are used in order to prevent the formation of depressions and to prevent the fixation elements from waxing in even during a longer fixation time. The time interval from one change of position to another can be large.

In a further embodiment of the invention it is provided that the change in the position of the fixing points or

- areas happening according to a predetermined rhythm. With this measure, the change in the position of the fixing points can be adapted particularly favorably to the respective operational requirements. In particular, excessive time intervals are avoided.

In a further embodiment of the invention it is provided that the fixation is released after a predetermined time in accordance with the deposition of a predetermined metal layer thickness. It has been shown that it is possible to remove the fixation of the cathode sheets after a certain time without the cathode sheets being distorted. In this way it is advantageously possible to reduce the number of fixation devices to be used in an electrolysis and thus to reduce the investment costs.

In a further embodiment it is provided that the fixation is terminated on the day after it starts, preferably 24 hours after the start, or after a multiple of 24 hours. Completely surprisingly, it has been found that the cathode sheets already on the day after the start of the electrolysis, especially after a deposition time of 24 hours, have a rigidity which sufficiently prevents warping, although they can still be moved and dented mechanically. The electrodes are already sufficient after 24 hours at normal current intensities, for example at 180-200 A / m ² and normal electrolyte temperature, for example 60 ° C. If you work with lower currents or less favorable temperatures, a separation time of is usually sufficient 2 days to achieve sufficient rigidity of the cathode sheets. The daily rhythm is particularly advantageous since the work involved in the fixation of a particularly suitable layer, for example the morning layer, can be transferred. Removing the fixation after only 24 hours or when a corresponding deposition thickness has been reached has the further advantage that it is possible to dispense with changing the position of the fixation points during this short time relative to the length of the anode travel. Overall, there is a very simple and practical method for electrolytic deposition.

In an embodiment of the method it is provided that the bath surface is covered and the electrolyte temperature is set higher than 60 ^° C. Thus, it can be advantageously used that the spatial fixation according to the invention makes continuous monitoring of the anodes and cathodes for short circuits superfluous.

To carry out the method for the electrolytic deposition of copper, provision is made for a fixing device to be arranged on at least one side of the cathode, said fixation device resting on the cathode surface. This advantageously makes it possible to fix the cathode spatially according to the invention. The natural tendency of the cathode sheets to deform similarly on the basis of the same production method is advantageously taken into account.

In an embodiment of the invention it is provided that the fixation device is designed to rest on both sides of the cathode. As a result, cathodes can also be spatially fixed, which bulge or reject not only uniformly on one side, but also on the other side. It also prevents the cathode from moving to the free side as a whole in response to bulging or warping.

In a further embodiment it is provided that the points at which the fixation device rests on the two cathode surfaces are arranged differently on the two cathode surfaces and are in particular in contact with the lower corners and in the middle of the cathode. This can advantageously counteract the main bulge tendency determined in experiments. The fixation is carried out in such a way that only the areas at risk of bulging are fixed, but the intermediate areas as well as the upper edge of the cathode, which is already adequately fixed by the ear straps and the cathode support rod, remain fixation-free.

- In a further embodiment of the invention it is provided that the fixing device has support elements between the anode and cathode. In this way, the _' anode, which has a stable design both in refining and in extraction electrolysis, is particularly advantageous for supporting and fixing the Cathode used, so that the fixation device itself can be made particularly light and simple. The fixation device is particularly easy to handle and can be easily moved or removed. In addition, if the support elements are dimensioned in the size of the distance between the anode and cathode, the security against contact between the anode and cathode can be further increased.

In a further embodiment of the invention, it is provided that the support elements are preferably designed as balls, cylinders or prisms, which together with holding elements form the fixing device. Spheres, cylinders or prisms have a surface shape that is relatively insensitive to deposits. It is thus easily possible to leave the support elements between the cathode and anode for several days without cleaning them. Bridging is advantageously avoided. The balls, cylinders or prisms are held in their vertical position by holding rods or similar elements, so that they can be easily and easily brought into the desired positions.

In a further embodiment of the invention it is provided that the fixation devices for a plurality of cathodes are combined to form a handling unit by supporting elements. This will introduce, move and Removal of the support elements is particularly facilitated, since simultaneous fixation is achieved for a larger number of cathodes of an electrolytic cell. Moving and moving the fixation elements thus requires only little effort, which is far below the effort required for non-fixed cathodes for permanent temperature monitoring and fault elimination.

In a further embodiment of the invention, it is provided that the support elements and their holding elements are made of material that is not a conductor of electrical current, e.g. Prozellan or hard rubber, but especially made of polyethylene or polypropylene. Furthermore, they are not attacked by the electrolyte liquid and can be used for a long time. The deposition of sludge is particularly difficult on porcelain and smooth plastic surfaces. The use of polyethylene and polypropylene is particularly advantageous. From these relatively light materials, γ ≈ 1.0, spheres, tubes and prism profiles are readily available commercially. The use of these plastics results in a particularly cheap, light and durable design for the fixing device with good usage properties.

In a further embodiment of the invention, it is provided that the support elements and their holding elements of a number of contact points on successive cathodes are combined to form a comb-like insert device. This results in an advantageously rigid structure, whose fixation elements remain completely free of deposits. The comb-like insert device is easy to handle; it is simply inserted into the spaces between the anodes and cathodes at predetermined locations on the cathodes, for example on the sides and in the middle of the cathodes.

In a further embodiment it is provided that the fixation devices can be placed on the electrode holding rods and that they carry a heat-insulating protective cover on their upper side, which preferably leaves the contact points of the busbars free with the anode ears and the cathode holding rods. The handling device can thus be particularly simple and advantageously used. Due to the direct support on the cathode support rods, there is no need for separate support devices and the overall height of the baths increases only insignificantly. At the same time, it is possible to place a heat-insulating protective hood directly on the fixing device. The contact points of the busbars are advantageously not covered so that they continue to be cooled by the indoor air. In this way, the electrolyte temperature can advantageously be increased and the separation efficiency of the electrolyte process can be improved with minimal effort and with the same heating.

• Fig. 1 eine Ausführung mit an Schnüren oder dünnen .Stangen aufgehängten Kugeln
• Fig. 2 eine kammartige Hantierungseinheit
• Fig. 3 zwei Gußanoden und ein Kathodenblech mit einer erfindungsgemäßen Fixierungsvorrichtung.

The invention is explained in more detail with reference to drawings, from which further details can be seen and which show particularly preferred embodiments. They show in detail:

• Fig. 1 shows an embodiment with balls suspended on cords or thin rods
• Fig. 2 is a comb-like handling unit
• Fig. 3 two cast anodes and a cathode plate with a fixation device according to the invention.

In Fig. 1, 1 denotes the support rod for the support elements 2. The individual support elements 2 are connected to the support rod 1 by threads or thin rods 3. Despite the simple attachment to the threads or thin rods 3, the support elements 2 remain in their positions between the anode and cathode, since they do not float in the electrolyte. The support elements 2 can have any shape, e.g. be designed as a double cone or pyramid. However, balls or profile sections that are readily available or that can be produced for retrofitting are particularly advantageous.

The length or the diameter of the support elements 2 is chosen to be smaller than the desired distance between the anode and cathode, advantageously approximately 5 mm smaller. So the differences in the cathode thicknesses etc. are taken into account, so that a flawless and easy insertion, movement and removal of the support elements 2 is possible at any time. The support elements 2 are preferably made of homogeneous plastic material, but they can also have fillers, for example quartz sand, in order to make their production cheaper and / or to increase their specific weight.

FIG. 2 shows a summary of the elements 1, 2 and 3 from FIG. 1 to form a dimensionally stable handling unit 4 which has a comb-like appearance. The support elements 5 are preferably no longer spherical, cylindrical or prismatic, but wedge-shaped with an upward taper. The combination of the elements 1, 2 and 3 into a comb-like device 4 is particularly advantageous for handling and the formation of the supporting elements 5 in a wedge shape is particularly advantageous for preventing the formation of bridges on the supporting elements. The preparation of the comb-like device 4 can be done by simply gluing the corresponding individual parts, e.g. of plate cutouts, but also a production by casting or the like. possible. The total length of the comb-like device 4 is preferably not more than 4 m, since longer devices become too bulky.

FIG. 3 shows two anodes 12 and 13 and a cathode sheet 8 arranged between the anodes 12 and 13, which is supported on the anodes 12 and 13 by means of the support elements 6 and 7. The support elements 6 and 7 are arranged unevenly on the two sides of the cathode sheet 8, once in the middle and once at the lower edge. They are made of threads or thin rods 15 and 16 held. The cathode sheet 8 is held at the top by the ear straps 9, which are pushed onto the cathode support rod 10. The cathode support rod 10 is placed in a manner not shown, like the ears 11 of the anodes, on busbars. The frame 14 drawn in broken lines is in turn placed on the cathode support rods 10. This combines a larger number of support elements 6 and 7 with their threads or thin rods 15 to form a handling unit. The frame 14 can be made of any material that does not conduct electricity, for example PVC. A thermal insulation layer, not shown, is preferably placed on the frame 14, preferably in the form of a mat. Both fiber and foam mats can be used. It is important that their underside is impermeable to air and that their thermal insulation is so large that no H ₂ 0 condenses on their underside. The method according to the invention for the electrolytic deposition of metals proceeds as follows:

First, cathode starting plates are manufactured. This can be done by electrolytic deposition of a layer on a mother plate, from which the deposited layer is removed after the deposition, or for example by cutting rolled thin copper plates. The cathode starting plates are then inserted into the electrolyte in the usual way and the fixing device is then introduced. The electrolyte is then optionally covered. In the subsequent normal separation process, there is no need for the support elements to move. At the latest after The cathode has reached a stiffness that prevents further warping of the cathode after 2-3 days, but usually already after 24 hours. The fixation device is now removed and the deposition continues without the fixation device without problems until the desired final cathode thickness is reached.

In experiments in which cast anodes with a thickness of 40 mm and starting cathodes with a thickness of approximately 0.5 mm are used in refining electrolysis (electrolyte temperature 60 ^° C., anode-cathode distance 30 mm, cathode size 1 m ² , 190 A / m ² ) the current yield could be increased from 94% to 97%. Thereby, the application of thermocolor colors to the cathode holding rods and continuous monitoring were dispensed with, and the cathode holding rod temperatures were only checked every 24 hours by a contact surface measuring device. In addition to increasing the current efficiency to 97%, there was a 9 kg reduction in the residual anode content with an original anode weight of 330 kg.

Overall, the method according to the invention using the device according to the invention results in an increase in the space-time yield, an increase in the current yield and a reduction in the residual amount with improved cathode quality. Furthermore, a reduced amount of work obtained by the elimination of the continuous E _n tstörung the plant and a reduction of the thermal Color color. A cover can also be advantageously made which saves heating steam and results in a better indoor climate.

The method and the device according to the invention were developed for copper refining. However, the invention is in no way limited to copper refining. It can be used wherever metals are electrolytically deposited on cathode sheets, e.g. in nickel or cobalt electrolysis. There are also considerable advantages when using inert cathode sheets, since the expensive titanium or stainless steel cathode sheets are made thinner and considerable investment costs can be saved.

Claims (21)

1. A method for the electrolytic deposition of metals, in particular copper, in which cathode sheets, in particular thin starting cathode sheets, are used between anodes in the electrolyte at the beginning of the electrodeposition, characterized in that the cathode sheets are spatially fixed in the electrolyte 2. The method according to claim 1, characterized in that the spatial fixation is carried out by defining individual points or smaller areas of the cathode surface. 3. The method according to claim 1 or 2, characterized in that the fixing of the cathode sheets is carried out by an indirect support of the cathode sheets on the anodes. 4. The method according to claim 1, 2 or 3, characterized in that the fixing points or areas on the two sides of the cathode sheet are distributed unevenly. 5. The method according to claim 1, 2, 3 or 4, characterized in that the fixing points or areas are distributed asymmetrically on the individual sides of the cathode sheet. 6. The method according to claim 1, 2, 3, 4 or 5, characterized in that the position of the fixing points or areas is changed during the deposition process. 7. The method according to claim 6, characterized in that the change in the position of the fixation points or areas occurs according to a predetermined rhythm. 8. The method according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that the fixing is released after a predetermined time in accordance with the deposition of a predetermined metal layer thickness. 9. The method according to claim 8, characterized in that the fixation on the day after its beginning, preferably 24 hours after the beginning or after a multiple of 24 hours, is ended. 10. The method according to any one of the preceding claims, characterized in that the bath surface is covered and the electrolyte temperature is set higher than 60 ° C. 11. A device for performing the method for electrolytic deposition of metals, in particular copper, according to one of claims 1-10, characterized in that a fixing device is arranged at least on one side of the cathode (8), which rests on the cathode surface. 12. The apparatus according to claim 11, characterized in that the fixing device is formed adjacent to both sides of the cathode (8). 13. The apparatus of claim 11 or 12, characterized in that the points at which the fixing device rests on the two cathode surfaces are arranged differently on the two cathode surfaces. 14. The apparatus of claim 11, 12 or 1 ₃ , characterized in that the fixing device is formed adjacent to the lower corners and in the middle of the cathode (8). 15. The apparatus according to claim 11, 12, 13 or 14, characterized in that the fixing device has support elements (2,5,6,7) between the anode (12,13) and cathode (8). 16. The apparatus according to claim 15, characterized in that the support elements (2,5,6,7) are preferably designed as balls, cylinders or prisms, which together with holding elements (3,15,16) form the fixing device. 17. The apparatus according to claim 11, 12, 13, 14, 15 or 16, characterized in that the fixing devices for a plurality of cathodes (8) are combined by support elements (1, 14) to form a handling unit. 18. Device according to one of claims 15 or 16, characterized in that the support elements (2,5,6,7) and their holding elements (3), made of the non-conductive material, e.g. Porcelain or hard rubber, but in particular made of polypropylene or polyethylene. 19. Device according to one of the preceding claims, characterized in that the support elements (5) and the holding elements of a number of contact points on successive cathodes (8) are combined to form a comb-like insert device (4). 20. Device according to one of the preceding claims, characterized in - that it is designed to be placed on the cathode support rods (10). 21. Device according to one of the preceding claims, characterized in that it carries a heat-insulating protective cover on its upper side, which preferably leaves the contact points of the busbars with the anode ears (11) and the cathode support rods (10) free.

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