EP0089475A1 - Coated valve metal anode for electrolytical recuperation of metals or metal oxides - Google Patents

Abstract

It is a coated valve metal anode for the electrolytic extraction of metals or metal oxides with a current-carrying structure, e.g. a current feeder and / or a current distributor (20), which consists of a jacket (50) made of valve metal and a core (70) arranged therein made of an electrically highly conductive metal. In order to minimize the internal ohmic voltage drop in such an electrode as much as possible, a contact structure (60) is embedded in the core metal (70) of the current-carrying component (20), which consists of valve metal and has a plurality of welds with the inner surface of the Jacket (50) is connected.

Description

The invention relates to an electrode, in particular anode made of coated valve metal for the electrolytic extraction of metals or metal oxides, with a current-carrying component, e.g. a current feeder and / or a current distributor, which consists of a jacket made of valve metal and a core arranged therein made of electrically highly conductive metal, which is in electrically conductive connection with the jacket.

Coated metal anodes of this type are intended to replace the anodes of lead or lead alloys or graphite originally used for this purpose in the field of the electrolytic extraction of metals, in particular non-ferrous metals, from the acid solutions containing metal to be obtained. The working surface of these coated metal anodes consists of a supporting core made of a valve metal, such as titanium, zirconium, niobium or tantalum, to which a coating of an anodically active material, for example metals of the platinum group or the platinum metal oxides, is applied. The main advantage of metal anodes is the saving of electrical energy compared to conventional lead or graphite anodes. The energy savings result from the larger surface area that can be achieved with coated metal anodes, the high activity of the coating and the dimensional stability. These Energy saving enables the anode voltage to be reduced considerably. The coated metal anodes provide further operational savings in that the cleaning and neutralization of the electrolyte is facilitated, since the coating of the anodes is not destroyed by Cl-, NO ₃ ^- or free H ₂ S0 ₄ . An additional cost saving results from the fact that when using coated metal anodes, the electrolyte does not have to be mixed with expensive additives, for example cobalt or strontium carbonate, as is required when using lead anodes. Furthermore, the contamination of the electrolyte and the metal obtained by lead, which cannot be prevented with lead anodes, is eliminated. Finally, the coated metal anodes allow an increase in current density and thus productivity.

Very different approaches have been taken in the design of these coated metal anodes.

In a known metal anode of the type in question (DE-OS 24 04 167), the essential design criterion is seen in that the anode surface facing the cathode is 1.5 to 20 times smaller than the cathode surface and the anode is accordingly operated at a current density which is 1.5 to 20 times larger than the cathode current density. These measures are said to economically maintain a relatively pure metal deposition of the desired crystalline structure and purity on the cathodes. The economic viability of the known anode should obviously consist in the fact that, due to the reduced area of the anode compared to the cathode, the material consumption for producing the anode is reduced and thus expensive valve metal material is saved. The cost reduction in the production of this anode is, however, paid for by not inconsiderable disadvantages. One of the drawbacks is there in that the anodic part of the cell voltage is high because the anode works with a high current density. As a major disadvantage, this entails a high energy requirement for the cells equipped with such an anode. The large current density and the reduced conductor cross section of the known anode due to the reduced effective area and thus the small material volume necessitate a large internal ohmic voltage drop, with the result that the necessary electrical energy is increased further. In order to eliminate the disadvantage of the large internal ohmic voltage drop, the profiled bars, which are arranged in a plane parallel to one another and form the effective surface, consist of a titanium sheath which is provided with a copper core. The power supply and distribution rails also have a comparable structure. These are complicated in order to largely shorten the current paths in the small effective area of the anode. The complicated structure of the profile bars forming the effective area and the long power supply and distribution rails required make the known construction considerably more expensive.

In a further known coated metal anode (DE-OS 30 05 795), a completely different approach has been taken to avoid the basic disadvantages of the above-described coated metal anode, which consists in the fact that the effective area of this anode is very large in that the bars arranged in a plane at a distance from one another and parallel to one another, which form the effective area, satisfy the relationship, according to which the total surface area of the bars F _A and the area Fp occupied by the overall arrangement of the bars have the relationship 6> F _A: Fp> 2 enough. This anode construction, which is preferably made of pure titanium, has no further current supply lines and distributors apart from the main current supply line made of copper. The current trans port in the vertical direction is therefore carried out solely by the rods made of valve metal. Overall, this anode has proven its worth in many electrolytic metal extraction processes due to the large effective area.

The one to be adjusted to the rising kilowatt hour prices, i.e. The internal ohmic voltage drop of the titanium anodes to be reduced now requires the use of large conductor cross-sections for the current-carrying components made of this expensive metal. When the active surface is formed from titanium rods arranged parallel to one another in a plane, these must be designed with a correspondingly large cross section in order to keep pace with the internal ohmic voltage drop occurring in the thick, massive lead anodes, which in turn has the technical and cost advantages of Valve metal anodes narrow.

In the case of the power line and distribution rails already mentioned, consisting of a core made of copper and a sheath made of titanium surrounding this copper core, the aim is to achieve a "metallurgical bond" between the metal of the core and the metal of the sheath. The reduction in the internal voltage drop, which is to be achieved by forming the core from a metal with good electrical conductivity, is actually only achieved if the current transfer to the coated active part by a large-area, perfect metallurgical bond between the material of the jacket and the Material of the copper is guaranteed. However, this prerequisite is at least somewhat achieved with a 'very expensive production. Nevertheless, these current feeders for anodes have proven their worth in chloralkali analysis using the diaphragm method. The temperature sensitivity of the metallurgical bond between copper and titanium assumes that in the case the re-coating of these DIA anodes, the titanium-coated copper rod is separated from the active part to be coated.

In connection with an anode for chlor-alkali electrolysis (GB-PS 1 267 985), current feeders and current distributors have also become known in which the titanium sheath is filled with a core made of aluminum or an aluminum alloy. The electrically conductive connection between the metal of the core and the metal of the sheath is to be achieved by a diffusion layer made of an alloy which is produced between the core metal and the sheath metal surrounding it. Although great importance is attached to the exact pouring of the titanium shell with the core metal in the liquid state, it cannot be ruled out that the core metal will shrink when it solidifies to such an extent that either no diffusion layer is generated between the core metal and the shell metal or an already formed one Diffusion layer tears again, with the result that gaps between the core metal and the cladding metal arise at least in some areas. This naturally leads to a high voltage drop when the current is transferred from the core metal to the cladding metal.

This problem has long been recognized in current-carrying components, such as current feeders and current distributors, in graphite anodes.

A graphite electrode with a metallic power supply for chlor-alkali electrolysis has become known (DE-OS 15 71 735), in which the metal-graphite current transfer is mediated by mercury or an amalgam which is liquid at outside temperature. This should ensure good electrical contact between the metal and graphite, since shrinkage cracks do not occur. This development has also been followed up on metal electrodes. In a known metal electrode for _E lektro- lyseapparate for electrolytic manufacture of chlorine _(DE -OS 27 21 958) are namely at least the primary conductor rails made of pipes, metal rods are arranged in their interiors, which current-conducting material are embedded in a liquid primarily under operating temperature. This current-conducting material, which is predominantly liquid at operating temperature, can be made from low-melting metals or alloys, such as Wood's metal, Roses metal or Lipowitz metal, sodium, potassium or their alloys, or another current-conducting material, such as metal oxides or graphite, which can be impregnated with metal alloys. consist.

These solutions have the disadvantage that the electrical conductivity of these materials is relatively low and at least some of these materials are not in the liquid state at low operating temperatures of the metal extraction processes. In addition _, the contact metals become encrusted during the long-term use that is common for the electrodes.

However, this development makes it clear that it is a considerable problem to bring about an electrically highly conductive connection between the core metal and the cladding metal of current-carrying components.

It is an object of the invention to provide an electrode with current-carrying components which result in the smallest possible internal voltage drop in long-term operation, which, moreover, can be produced inexpensively and economically, are distinguished by a high level of operational reliability and fit well into the active parts of the coated valve metal anodes, so that to give possible _'flat construction metal anodes.

This object is achieved with an electrode of the presupposed type with a current-carrying component which consists of a jacket made of valve metal and a core of electrically good conductive metal arranged therein, in that a contact structure is embedded in the core metal of the current-carrying component, which consists of valve metal exists and is connected to the inner surface of the jacket via a plurality of welds.

The inventive design of the electrode, in particular its current-carrying component in such a way that the contact structure in question is embedded on the one hand in the core metal and on the other hand connected to the inner surface of the jacket via a plurality of welds, results in an electrically highly conductive connection between the core metal and with the cladding metal. the consequence of a low voltage drop even at high voltages and large currents. The intimate contact achieved between the contact structure and the core metal is maintained over a long operating time, even with large temperature differences. In addition, the contact structure improves the mechanical strength of the correspondingly designed current-carrying component and thus the metal electrode as a whole. The electrode according to the invention is inexpensive and economical to manufacture because the difficulties associated with the known arrangements of metallurgical connection of the core metal with the cladding metal or the introduction of a suitable intermediate layer, for example of a material which is liquid at operating temperatures, are eliminated. In the manufacture of the electrode according to the invention, the core metal in the liquid state can simply be poured into the interior of the jacket. Due to the corresponding design of the contact structure, the core metal flows intimately around the contact structure and shrinks onto it with prestress. This results in the desired intimate contact between the core metal and the contact structure. This, in turn, is welded to the inner surface of the jacket with good electrical conductivity.

Triangle, rectangle, trapezoidal and other polygonal profiles, corrugated iron box profiles, pipes or the like are suitable as a jacket for the current-carrying components of the configuration according to the invention. The wall thickness of the jacket of the current-carrying components according to the invention expediently moves between 0.5 mm and a few millimeters. The jacket consists of one of the valve metals already mentioned. If the jacket of the current-carrying components according to the invention consists of two or more profile parts. is assembled and these profile parts are welded together, the welds must be gas and liquid tight.

The contact structure provided in the current-carrying components according to the invention can be a spatial structure with surfaces oriented in several directions, which is surrounded by the core metal from several directions. When the liquid core metal is poured in, such a spatial structure is surrounded or surrounded by it from several directions, so that the core metal shrinks intimately onto the spatial structure from several sides during the solidification process.

In this way, a large-area and flawless bond between the core metal and the contact structure is guaranteed. The problem of a metallurgical bond between the core metal and the cladding metal is then completely avoided.

With a large surface area, the contact structure has a small volume, measured by the volume of the core metal.

Strips made of expanded metal, wire mesh, perforated sheet metal or the like are used as the contact structure or spatial structure Chen in question. At least one strip is laid inside the jacket of the current-carrying component essentially parallel to the direction of current flow and welded to the inside surface of the jacket with a plurality of welding spots. It is possible to have the strip run straight or wavy. In the latter case, there is a particularly varied orientation of the surfaces of the strip, with the result that the contact structure is particularly integrated into the core metal.

However, the contact structure can also be formed from at least one wire which is laid in a corrugated manner in the component essentially in the current flow direction and is preferably welded to the inner surface of the jacket several times on one side. With this type of arrangement, a wire also forms a spatial structure with a surface or surface portions oriented in several directions, which can be flowed around by the core metal when pouring in from several sides, so that the core metal can shrink intimately and firmly onto this contact structure. Instead of a wire, wire sections in the form of wire loops can also be used, which are welded to the inner surface of the jacket.

The same effect results when the contact structure is made up of a plurality of bodies, such as bolts with thickened portions and / or thinned portions. The bolts can run perpendicular to the direction of current flow in the component, but can also take any other angle to it and to one another. The only thing that is decisive is that these bodies have a sufficient volume or a sufficient cross-section in order to produce an electrically highly conductive connection with the lowest possible voltage drop to the core metal on the one hand and to the jacket metal on the other hand, so that even high currents with a low voltage drop from the core metal the jacket metal and further on the active surface of the metal anode can be transferred. The number and the cross section of the welding points between the contact structure and the jacket are determined on the basis of a predetermined, permissible voltage drop.

To further reduce the electrical contact resistance between the core metal and the contact structure, the latter can be provided with a suitable contact coating. This lends itself to a relatively small-area contact structure or to electrically conductive components that are particularly highly stressed. The materials usually used for this purpose in electrical engineering can be used as contact coatings insofar as they are compatible with the respective metal of the core. Noble metals or the oxides and / or base metals and their electrically conductive substoichiometric or doped oxides can be used as materials.

ausgezeichnet bewährt. Im Kurzschlußfall hat metallisches Zink noch den Vorteil, daß seine Korrosionsprodukte weder die Wasserstoffüberspannung der Kathode noch die Reinheit des abgeschiedenen Kathodenzinks beeinflussen.Metals with a melting point which is at least 500 ° C. lower than that of the metal of the jacket of the current-carrying component are suitable as casting metal for producing the core of a current-carrying component of an electrode according to the invention. The core metal should also have a significantly higher electrical conductivity than the valve metal of the jacket, for example titanium. Taking these requirements into account, zinc, aluminum, magnesium, tin, antimony, lead, calcium, copper or silver and corresponding alloys thereof can be used as core metals. Of course, the selection of the metal for the core must also take into account the special requirements of the respective metal extraction process. For example, in zinc extraction electrolysis, metallic zinc with its low melting point of 420 ° C. and its good specific electrical conductivity of 156 × 10 ³ has become the core metal for a current-carrying component of an electrode according to the invention

proven excellent. In short In the final case, metallic zinc has the advantage that its corrosion products do not affect the hydrogen overvoltage of the cathode or the purity of the deposited cathode zinc.

Zinc has also proven to be suitable as a core metal for the current-carrying components for the production of copper by means of the electrodes according to the invention. However, aluminum, magnesium or lead and the corresponding alloys can also be used.

The known electrodes do not yet take into account the proposed solution that the metal of the core of a current-carrying component of an electrode according to the invention should be selected in accordance with the special requirements of the respective metal extraction process. The connection of titanium-coated copper as an active part or current feeder and distributor, as is the case with the known solutions, is in fact not feasible in most metal extraction processes, since short circuits occur during electrolysis due to the formation of dendrites in the cathodically deposited metal, which form the titanium jacket can destroy. As is known, the copper and alloy contact metal exposed by short circuit dissolves anodically. The metal ions that are formed are deposited on the cathode, contaminate the cathode product and also have an influence on the hydrogen overvoltage and thus on the current efficiency of the metal extraction process. This results in an unsalable, because contaminated cathode metal, which is also produced at high cost due to reduced current efficiency. It should not go unmentioned that a single short circuit e.g. in electrolytic zinc extraction, can negatively affect a variety of cathodes. Titanium-plated copper with a metallurgical composite appears to be economically unsuitable even in the electrolytic copper extraction because of the high short-circuit rate and the high rod prices.

A particularly advantageous development of the invention is that the component serving as a current distributor is integrated into the active surface of the electrode in that the jacket is at least partially formed by an electrode plate representing the active surface of the electrode and a contact structure in such a current-carrying component is arranged.

This measure according to the invention ensures that a particularly compact electrode is obtained, which is particularly characterized by a small thickness. As a result, not only can a particularly space-saving cell be constructed, but the insertion and removal of the electrodes in or from such a cell is particularly easy.

An electrode for metal extraction is already known (US Pat. No. 4,260,470), in which the active surface is formed by vertically arranged plates which are arranged to overlap one another, in each case in the overlapping areas a cavity running parallel to the plate extension, e.g. by U-bending an overlapping area of a plate. A metal is poured into these cavities.

In addition, current-carrying rods are embedded in the cast metal, which are connected to a horizontally running current guide rail. The potting metal primarily serves to stiffen the effective surface of the electrode consisting of flat plates. Only in second place is the potting metal used for the electrical connection of the rods embedded therein to the effective surface of the electrode. These rods are not comparable with the contact structure provided according to the invention because they do not represent a spatial structure with surface portions oriented in different directions, onto which the potting metal 11 has been shrunk. Dementspre Accordingly, the current-carrying rods are not, like the contact structure according to the invention, directly connected to the jacket of the current-carrying component or the corresponding region of the electrode plate itself by welding.

Finally, there are the problems that have been discussed in connection with the shrinking of potting metal.

In the integrated electrode according to the invention, it is recommended that the contact structure be welded to the region of the electrode sheet which at least partially forms the jacket, since this results in a direct transfer of the current from the core metal of the current-carrying component to the effective electrode surface.

To form a cavity to be filled with the core metal for the current-carrying component according to the invention integrated into the active surface, it is expedient that at least the region of the electrode plate which partially forms the jacket is U-shaped or undulating and this area is covered by a cover plate to form the closed jacket is added. The cavity formed in this way within the jacket can be poured out in the manner already described with a suitable core metal which intimately connects to the contact structure.

The cover plate mentioned, which can have any shape, is expediently welded to the electrode plate in a gastight and liquid-tight manner.

Another embodiment of the invention is that the effective area of the electrode and formed by a plurality of parallel to each other in a plane arranged profile bars which _K ontaktstruktur by Ab sections of the profile bars is formed, which is passed through the core of the current-carrying component.

This embodiment also differs from the prior art electrode of US-PS 4,260,470 characterized ,, that in the inventive solution the portions of the _P ro- filstäbe which are passed through the current-carrying component or the core, with the shell of the current-carrying Are welded component. In this way, the solution according to the invention results in a direct connection of the sections of the profiled bars serving as the contact structure with the effective electrode surface, with the result of a good conduction of the current. Beyond. may be formed from with respect to its surface or its shape so the portions of the profiled bars which act as _K on- clock structure, that these meet the requirements that are placed on the contact structure according to the invention. Finally, they can have a Rontact coating.

• Fig. 1 den prinzipiellen Aufbau einer erfindungsgemäßen Elektrode,
• Fig. 2 einen Schnitt durch den Stromzuleiter der Elektrode nach Fig. 1 gemäß der Schnittlinie II-II,
• Fig. 3 einen Schnitt durch eine andere Ausführungsform eines Stromzuleiters,
• Fig. 4 einen Längsschnitt durch den Stromzuleiter der Elektrode nach Fig. 1 gemäß der Schnittlinie IV-IV,
• Fig. 5 eine weitere Ausführungsform eines Stromzuleiters,
• Fig. 6 einen horizontalen Schnitt durch die wirksame Fläche der Elektrode nach Fig. 1 gemäß der Schnittlinie VI-VI mit separatem Stromverteiler,
• Fig. 7 einen Schnitt durch den Stromverteiler der Elektrode nach Fig. 6 gemäß der Schnittlinie VII-VII,
• Fig. 8 einen horizontalen Schnitt durch eine weitere Ausführungsform einer erfindungsgemäßen Elektrode,
• Fig. 9 ebenfalls einen horizontalen Schnitt durch eine weitere Ausführungsform der erfindungsgemäßen Elektrode,
• Fig. 10 einen horizontalen Schnitt durch die wirksame Fläche einer weiteren Ausführungsform der erfindungsgemäßen Elektrode, bei der ein Stromverteiler in das Aktivteil integriert ist,
• Fig. 11 einen Schnitt durch die Elektrode nach Fig. 10 gemäß der Schnittlinie IX-IX,
• Fig. 12 einen horizontalen Schnitt durch die wirksame Fläche eines weiteren Ausführungsbeispiels einer erfin-. dungsgemäßen Elektrode, bei der ebenfalls ein Stromverteiler in das Aktivteil integriert ist,
• Fig. 13 einen Vertikalschnitt durch eine weitere Ausführungsform einer erfindungsgemäßen Elektrode,
• Fig'. 14 eine Ansicht der Elektrode gemäß der Fig. 13 nach der Linie XIV-XIV,
• Fig. 15 einen Schnitt durch eine weitere Ausführungsform einer erfindungsgemäßen Elektrode,
• Fig. 16 einen Schnitt durch eine weitere Ausführungsform der erfindungsgemäßen Elektrode,
• Fig. 17 einen Schnitt durch die Elektrode nach
• Fig. 16 gemäß der Schnittlinie-XVII-XVII,
• Fig. 18 eine perspektivische Ansicht einer erfindungsgemäßen Elektrode, und
• Fig. 19 ebenfalls eine perspektivische Ansicht einer erfindungsgemäßen Elektrode.

Exemplary embodiments of the electrode according to the invention are shown in the attached drawings. It shows:

• 1 shows the basic structure of an electrode according to the invention,
• 2 shows a section through the current feeder of the electrode according to FIG. 1 according to section line II-II,
• 3 shows a section through another embodiment of a current feeder,
• 4 shows a longitudinal section through the current feeder of the electrode according to FIG. 1 according to section line IV-IV,
• 5 shows a further embodiment of a current feeder,
• Fig. 6 shows a horizontal section through the effective 1 according to the section line VI-VI with a separate current distributor,
• 7 shows a section through the current distributor of the electrode according to FIG. 6 according to section line VII-VII,
• 8 shows a horizontal section through a further embodiment of an electrode according to the invention,
• 9 likewise a horizontal section through a further embodiment of the electrode according to the invention,
• 10 shows a horizontal section through the effective surface of a further embodiment of the electrode according to the invention, in which a current distributor is integrated in the active part,
• 11 shows a section through the electrode according to FIG. 10 along the section line IX-IX,
• Fig. 12 is a horizontal section through the effective area of another embodiment of an invent. inventive electrode, in which a current distributor is also integrated in the active part,
• 13 shows a vertical section through a further embodiment of an electrode according to the invention,
• Fig '. 14 is a view of the electrode according to FIG. 13 along the line XIV-XIV,
• 15 shows a section through a further embodiment of an electrode according to the invention,
• 16 shows a section through a further embodiment of the electrode according to the invention,
• Fig. 17 shows a section through the electrode
• 16 according to the section line-XVII-XVII,
• 18 is a perspective view of an electrode according to the invention, and
• 19 also shows a perspective view of an electrode according to the invention.

1 shows the basic structure of a coated metal anode according to the invention. Thereafter, this electrode consists of a horizontal current feeder, which is designated by 10 in total. A vertically running power distributor 20 is connected to the underside of this power supply approximately in the middle. This power distributor 20 is connected to the active part, designated as a whole by 30, i.e. the active area, the electrode connected. To stiffen in particular the vertical edge regions of the active part 30, these are connected to the current feeder 10 via stiffening struts 40.

Fig. 2 shows a vertical section through the current feeder 10 according to Fig. 1. Then, the current feeder 10 consists of a jacket designated overall by 50, which is composed of two U-profiles 51 and 52, which partially overlap with their free legs and are connected to one another in these areas by weld seams 53. The jacket 50 consists of a valve metal, preferably titanium. A strip 60 of expanded metal made of the same valve metal as the cover, namely titanium, is welded to a plurality of welding spots 61 on two opposite inner surfaces of the cover 50. This results in both a fixed mechanical connection as well as a good electrically conductive connection between the respective strip 60 of expanded metal and the jacket 50. A core 70 made of a suitable, electrically highly conductive non-valve metal is cast into the cavity of the jacket. When the core metal 70 is poured in, it flows around the strips 60 of expanded metal from all sides and, when it solidifies, shrinks intimately onto the surface of the strips 60 made of expanded metal. This also results in an intimate-mechanical and good electrical connection between the core metal 70 and the _S trei- fen 60 of expanded metal. The strips 60 made of expanded metal therefore represent the contact structures desired according to the invention.

The strips 60 of expanded metal run parallel to the current profile in the current feeder 10, specifically from a connection head 11 of the current feeder 10 to at least the point at which the current distributor 20 branches off. If it is desired that part of the current should also run over the stiffening strip 40 on the right in FIG. 1, it is advisable to let the strips 60 of expanded metal run approximately into the region of the branching point of this reinforcing strip 40.

3 shows in cross section a somewhat modified embodiment of the current lead 10 of the electrode according to FIG. 1. In this case, the jacket 50 of the current lead 10 consists of a U-shaped profile 51a and a flat end strip 54. The two parts 53 and 54 of the jacket 50 are connected to one another at their joints by welds 53. Is on the lower inner surface of the jacket 50 A strip 60 is arranged made of expanded metal, which is the _K ontaktstruktur and cast in for this purpose by the core metal 70 and is welded to the inner surface of the shell 50 is.

5 shows a current feeder 10 with a one-piece jacket 50. For the purpose of producing this embodiment, a U-profile 55 is assumed, on the lower inner surface of which a strip 60 of expanded metal is welded. Thereafter, the core metal 70 is poured in to a height that corresponds to the height of the inner cross section of the final shape of the jacket of the power supply 10. The free legs 55a of the U-profile 55 are then bent inwards, as indicated in FIG. 5, and sealed gas and liquid-tight by applying a weld 53.

FIG. 4 shows a longitudinal section of the current feeder 10 of the electrode according to FIG. 1. However, in this case a somewhat different contact structure is provided. This is because the contact structure consists of two wires 61 which are laid approximately in the direction of the current flow, but in wave form in the interior of the jacket 50. The wires 61 touch the inner surfaces of the jacket 50 at intervals and are welded to it here. One of the wires 61 can be welded with its end facing the connection head 11 to an intermediate plate 12, in order in this way to achieve a direct transmission of the current from the connection head 11 via the intermediate plate 12 to one of the wires 61 of the contact structure formed thereby.

_F ig. 6 shows a horizontal section through the current distributor 20 of the electrode according to FIG. 1 according to the section line VI-VI. 6 that the current feeder 20 is integrated in the active part 30. The active part 30 can consist, for example, of two plates 31 which extend from the current distributor 20 on both sides and which are designed in the form of a corrugated sheet to increase the surface area and the rigidity. The power distributor 20 itself consists of a jacket 50, which is composed of two U-profiles 56 and 57, the longitudinal flanges 56a and 57a are welded together by welds 53. The two plates 31 of the active part 30 are also welded to the flanges 57a.

In the cavity formed by the jacket 50, wires 61 which are laid in a wave-shaped manner in the current flow direction and which represent the contact structure. The cavity is poured out by a corresponding core metal 70.

As can be seen from FIG. 7, the corrugated wires 61 touch the inner surface of the jacket 50 of the current distributor 20 at intervals and are welded to the jacket 50 at these points, preferably only at one point.

Fig. 8 shows in horizontal section a so-called box electrode, in which the active part 30 is formed by two expanded metal sheets 32, which complement each other to form a hollow profile, in the interior of which the current distributor 20 runs. This power distributor has a jacket 50 which, according to FIG. 2, is composed of two U-profiles 51 and 52 and to which the metal sheets 32 are welded. The cavity of the jacket 50 is poured out by a suitable core metal 70. The contact structure consists of pins 62, each one or more dilutions. Have constrictions 62a.

FIG. 9 shows an electrode arrangement that is essentially comparable to FIG. 8. However, in the construction according to FIG. 9, the pins 62 which represent the contact structure have thickenings 62b at the end.

10 and 11 show an electrode with a current distributor integrated in the active part. In this electrode, the active part 30 or the effective surface consists of a corrugated sheet profile 33. To form the current distributor 20, a wire 61 in wave form, which form the contact structure, is preferably inserted in two adjacent wave troughs. The core metal 70 is also cast into these two wave troughs. This area of the corrugated sheet profile 33 of the active part 30 then forms part of the jacket of the power distributor 20. The jacket is closed by a cover plate 80 covering the two troughs, which is angled according to the wave shape of the corrugated sheet profile 33 and in the area of its _A b angled with the Corrugated sheet profile 33 is welded.

A similar design of an active part 30 with an integrated current distributor 20 is shown in FIG. 12. In this case, the corrugated sheet profile 33 has a U-shaped region 33a which is wider than the other shafts and serves as part of the jacket of the current distributor 20. On the inner surface of area 33a of corrugated sheet profile 33, a strip 60 of expanded metal is placed as a contact structure, which is welded to corrugated sheet profile 33 at a plurality of locations. The U-shaped area 33a of the corrugated sheet profile 33 forms, together with a cover plate 81, which is welded to the corrugated sheet profile 33 in a suitable manner, a cavity into which the core metal 70 is cast.

FIGS. 13 and 14 show a fundamentally different embodiment of an electrode. Thereafter, the active part 30 of the electrode consists of profiled bars 34 which are spaced apart and parallel to one another. The profile of these bars 34 is arbitrary. In the case shown, these are round bars. The current distributor 20 comprises a tubular jacket 50 with two rows of opposing radial bores through which the profile bars 34 are inserted. The profile bars 34 are mechanically and electrically conductively connected by welds 53 to the tubular jacket 50 of the power distributor 20. A suitable core metal 70 is cast into the tubular jacket 50. The sections 63 of the profile bars 34 which lie within the tubular jacket 50 of the current distributor 20 represent the contact structure. For this purpose, these sections 63 can have a corresponding shape or surface design or a contact coating in order to achieve an intimate shrinking of the core metal 70 onto these sections 63 of the profile bars 34 to achieve.

15 to 17 show a further basic embodiment of a relevant metal electrode. In this case, the active part 30 is formed by two opposing corrugated iron profiles 35 and 36, which enclose a cavity. 15 has a zigzag shape, the corrugated sheet profile 36 according to FIG. 16 is composed of U-shaped areas. In the cavity between the two corrugated sheet profiles 35 and 36, wires 61 are inserted as a contact structure, which are spaced at intervals with the corrugated sheet profiles 35 _and . 36 are welded. The remaining cavity between the two corrugated sheet profiles 35 and 36 is filled with a suitable contact metal 70. This also results in the current-carrying component 20.

_F ig. 18 shows an electrode in which two current distributors 20 are integrated in the active part 30 in accordance with the training options described above. The active part 30 is brought up to the underside of the power supply line 10 and connected to it. In this case, it is recommended in any case that the contact structure in the interior of the power supply line 10 extends essentially over the entire length of the active part 30.

19 shows a perspective view of an expanded mesh box electrode corresponding to FIGS. 8 and 9 with two current distributors 20 and one stiffening strut 40 at each end.

The type and manufacture of the electrodes according to the invention are explained in more detail with reference to the following examples.

example 1

To produce a power supply, a non-rolled, 30 mm wide expanded iron strip is used on a 985 mm long, 50 mm wide, 15 mm high and 1.5 mm thick U-shaped titanium profile sheet on the inside for a length of 500 mm corresponding to the extension length of the active part Contact structure with a mesh length of 10 mm, a mesh width of 5 mm, a web thickness of 1 mm and a web width of 1 mm fastened by spot welding. The distance between the 10 mm welding spots is 30 mm. The U-shaped titanium profile sheet prepared in this way is overlapped with a second titanium profile sheet of the same dimensions, but without a welded-in titanium expanded metal strip, to form a rectangular profile jacket with a total thickness of 25 mm, and welded together in a gas and liquid-tight manner. One end of the rectangular profile jacket is 3 mm thick welded titanium plate tightly closed. A copper contact head with silver hard solder is then soldered onto this titanium plate. The power supply is now ready to be cast with core metal.

A power distributor with a 1150 mm long, 80 wide and 12 mm thick jacket made of titanium, but in which two titanium stretcher strips as a contact structure, i.e. on each of the two U-profiles, is prepared in the same way.

Power feeders and power distributors are heated in an oven to approx. 500 ° C in an inert atmosphere. Hot, molten zinc is then poured into its open ends. After filling, void-free solidification and cooling, the filling ends of the coats are freed of excess zinc and cleaned. Now the still open ends of the sheaths are closed by welding titanium plates on.

Along the two narrow sides of the power distributor, two coated active parts measuring 990 x 242 mm made of 1 mm thick titanium corrugated sheet with a wavelength of approx. 24 mm, an amplitude of approx. 6 mm and an area factor of total surface: projected surface of approx. 3 are welded on.

The upper end of the power distributor protruding 160 mm from the corrugated sheet area is welded to the middle of the lower narrow side of the power supply line. The anode construction can be further fixed and stiffened by titanium connections between the current feeder and the upper edge of the corrugated iron (likewise FIG. 1).

The anode described is designed for a current of 390 A corresponding to a current density of 350 A / m 'on the anode side. At a current of 390 A occurs in the Anode only has an ohmic voltage drop of approx. 50 mV.

The anode construction is stiff and robust. This results from the corrugated sheet structure and the current distributor designed as described.

The anode is simple in construction, inexpensive to produce due to the small amount of titanium and the inexpensive power supply and distribution with zinc core and has a very large geometric surface. It weighs 20 kg without a copper contact head, of which only 6 kg is accounted for by the expensive material titanium.

Thanks to the favorable area factor 3, the anode-side current density of 350 A / m ^{2 is} reduced to a D _A value (anodic current density) of approximately 235 A / m ² in this anode.

In the case of electrolytic zinc extraction, for which this anode is intended, a particularly low oxygen overvoltage and cell voltage results from the above and from the catalytic effectiveness of the active components of the coating over a long operating time.

This anode has also proven to be very advantageous for the electrolytic extraction of manganese dioxide. The large surface area of the anode according to the invention with the area factor 3 available for the deposition and its extremely low internal voltage drop of approx. 18 mV with an anode-side current density of 120 A / m ² result in not only the quality improvements in the electrolytic manganese dioxide but also considerable energy savings per ton of product produced . Come in addition a considerable saving in specific workload per ton of electrolytic brownstone produced thanks to the easy removability of the Mn0 ₂ deposits from this anode.

Example 2

A modification of the anode construction according to the invention with a current feeder and distributor, which is particularly suitable for use in the electrolytic extraction of zinc at high current loads with an anode-side current density of 600 A / m ² , is produced in the following manner.

On a 985 mm long, 25 mm wide, 60 mm high and 1.5 mm thick U-shaped titanium profile sheet, a rolled, 20 mm wide titanium grating strip with the same grating characteristics as described in Example 1 is described on the inside on the floor for a length of approx. 800 mm fixed by spot welding. The distance between the 10 mm welding spots is 25 mm. The U-shaped titanium profile is welded gas-tight and liquid-tight using a 1.5 mm thick sheet of titanium sheet of suitable dimensions to form a rectangular profile jacket. The front side of the rectangular profile cladding, which is close to the titanium contact structure, is sealed with a 3 mm thick titanium plate of suitable dimensions, which also has a titanium expanded mesh structure on the inside. The copper contact head must be attached to it. The casting of this conductor with zinc and the closing of the pouring opening is carried out as described in Example 1.

An 1150 mm long, 565 mm wide and 1 mm thick corrugated titanium sheet serves as the active part for this anode and has the same characteristics as described in Example 1, but provided with two 1150 mm long and 60 mm wide, flat areas arranged in the middle of the two corrugated metal halves. In these flat areas, unwrought titanium expanded metal strips with a contact coating are welded on in the manner already described. Covering 1 mm thick titanium sheet strips, which are welded tightly to the wave crests bordering the flat areas on both sides, create two power distribution jackets integrated in the active part. After casting with zinc and sealing, these result in very functional power distributors.

The corrugated sheet metal anode coated thereafter, which expediently also has some bores which improve the electrolyte circulation, is then sealed to the current supply conductor in the region of the current distributor ends and spot-welded in the other zones.

The ohmic voltage drop of this anode loaded with 670 A is only 50 mV. The two power distributors integrated in the active part together with the welded power supply and the wave-shaped active part result in a very stiff, robust and durable construction with a very small amount of titanium of approx.6.5 kg per anode. The total weight of the anode is approximately 23.5 kg. The area factor 3 of the active part brings about a reduction in the cell voltage which reduces the anode-side current density from 600 A / m ² to a D _A (anodic current density) of 400 _{A /} m ² .

Example 3

The following coated titanium anode has proven its worth in copper extraction electrolysis with an anode-side current density of 350 A / m ² and a current load of 590 A / anode.

The 1220 mm long titanium current supply jacket and the two 1170 mm long, 60 mm wide and 12 mm thick titanium current distribution jackets required for this anode are designed according to example 1.

The jackets of the power supply line and the two power distributors were heated to about 750 ° C. in an oven in an inert atmosphere. 750 ° C hot molten aluminum was then poured into the open ends of the coats. After it solidified and the pouring openings had been cleaned, they were sealed with 3 mm thick titanium plates.

The two power distributors were in a 990 mm high, 852 mm wide and 14 mm thick, coated titanium expanded mesh box open at the top and bottom with the mesh characteristics mesh length 31.75 mm, mesh width 12.7 mm, web width 2.46 mm, web thickness 1.0 mm in the middle of the respective box halves, welded to the entire height of the box. The narrow side of the power feeder was welded to the top 180 mm long power distribution ends protruding from the box. The anode construction was additionally fixed and stiffened by titanium connecting strips between the power supply jacket and the upper box corners.

The titanium weight of this anode is 6 kg, its total weight is 13.2 kg. Despite this low titanium requirement, the ohmic voltage drop of this anode is only 35 mV.

Claims (18)

1. electrode, particularly the anode of coated _V ene tilmetall for the electrowinning of metals or metal oxides, with a current-carrying component, such as a current feed and / or a current distributor which consists of a sheath of valve metal and disposed therein core of electrically highly conductive metal , which is in electrically conductive connection with the jacket, characterized in that in the core metal (70) of the current-carrying component (10; 20) a contact structure (60-63) is embedded, which consists of valve metal and a plurality of Welds is connected to the inner surface of the jacket (50). 2. Electrode according to claim 1, characterized in that the contact structure (60-63) is a spatial structure with surfaces oriented in several directions, which is surrounded by the core metal (70) from several directions. 3. Electrode according to claim 1 and 2, characterized in that the contact structure is formed from a strip (60) made of expanded metal, wire mesh, perforated plate or the like (e.g. Fig.2). 4. Electrode according to claim 3, characterized in that the strip (60) made of expanded metal or the like is laid parallel to the current flow direction in the component (10; 20). 5. Electrode according to claim 4, characterized in that the strip (60) made of expanded metal or the like extends in a straight line. 6. Electrode according to claim 4, characterized in that the strip (60) made of expanded metal or the like is corrugated. 7. Electrode according to claim 1 and 2, characterized in that the contact structure is formed from at least one wire (61) which is laid in a corrugated manner in the current flow direction in the component (10; 20) (Fig. 4 and 7). 8. Electrode according to claim and 2, characterized in that the contact structure of a plurality of bodies such as bolts (62) with thickenings (62b) and / or thinners (62) is shown (Fig. 8 and 9). 9. Electrode according to one of the preceding claims, characterized in that the contact structure (60-63) is provided with a contact coating. 10. Electrode according to one of the preceding claims, characterized in that the core (70) of the current-carrying component (10; 20) consists of a metal whose melting point is at least 500 ° C lower than that of the metal of the jacket (50). 11. Electrode according to one of the preceding claims, characterized in that the metal of the core (70) of the current-carrying component (10; 20) has a substantially higher electrical conductivity than the valve metal of the jacket (50). 12. Electrode according to one of the preceding claims, characterized in that the component serving as a current distributor (20) is integrated into the active surface (30) of the electrode in that the jacket is at least partially by an electrode sheet (30 ) is formed and a contact structure (60, 61) is arranged in such a current-carrying component (FIGS. 6, 10 to 12 and 15 to 17). 13. Electrode according to claim 12, characterized in that the contact structure (60) is welded to the region of the electrode sheet (30) which at least partially forms the jacket (e.g. Fig. 12). 14. Electrode according to claim 12, characterized in that at least the area of the electrode sheet (30) partially forming the jacket is _U -shaped or undulating and this area is supplemented by a cover plate (80; 81) to form the closed jacket (Fig. 10 and, 12). 15. Electrode according to claim 14, characterized in that the cover plate (80; 81) is welded to the electrode plate. 16. Electrode according to one of the preceding claims, characterized in that the electrode sheet is designed as a one-piece or multi-piece corrugated sheet (31). 17. Electrode according to one of the preceding claims, characterized in that the electrode sheet, which is preferably designed as a corrugated sheet (31), is welded on both sides to the jacket (50) of the power distributor (20). 18. Electrode according to claim 1 and 2, characterized in that the effective surface (30) of the electrode is formed by a plurality of profile bars (34) arranged parallel to one another in one plane and the contact structure by sections (63) of the profile bars (34) is formed, which are passed through the core (70) of the current-carrying component (20) (FIGS. 13, 14).

Images