EP0089475B1 - Coated valve metal anode for electrolytical recuperation of metals or metal oxides - Google Patents

Description

The invention relates to an electrode made of coated valve metal for the electrolytic extraction of metals or metal oxides, with a current feeder and / or a current distributor, which consists of a jacket made of valve metal, a jacket arranged in the jacket and having an electrically conductive connection therewith and made of electrically highly conductive metal an electrically conductive element embedded in the core metal.

Coated electrodes, in particular anodes of this type, are intended to replace the anodes of lead or lead alloys or of 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. This energy saving enables the anode voltage to be reduced considerably. The coated metal anodes result in further operational savings in that the cleaning and neutralization of the electrolyte is facilitated, since the coating of the anodes is not destroyed by CI, NOg or free H ₂ SO 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 disadvantages is 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) one has gone a completely different way to avoid the fundamental 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 in a plane at a distance from one another and parallel to one another, which form the effective area, serves 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. Electricity transport in the vertical direction is therefore carried out solely by the bars made of valve metal. Overall, this anode has proven its worth in many electrolytic metal extraction processes due to the large effective area.

The inner one to be adapted to the rising kilowatt hour prices, ie to be lowered Ohmic voltage drop of the titanium anodes meanwhile 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, they 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 diminishes.

In the case of the power line and distribution rails already mentioned, consisting of a core of copper and a sheath 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 requires, however, that in the case of recoating 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 sheath with the core metal in the liquid state, it cannot be ruled out that the core metal shrinks when it solidifies to such an extent that either no diffusion layer is produced between the core metal and the sheath metal or a diffusion layer that has already formed rips again; each with the result that gaps arise at least in regions between the core metal and the cladding metal. Of course, this leads to a high voltage drop when the current transfers 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 electrolysis apparatus for the electrolytic production of chlorine (DE-OS 27 21 958), at least the primary conductor rails consist of tubes, in the interior of which metal rods are arranged, which are embedded in an electrically conductive material that is predominantly liquid at 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 customary 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 result in metal anodes which are as flat as possible

This object is achieved in the case of an electrode of the presupposed type in that the element consists of valve metal, the element has the shape of a contact structure with surfaces oriented in several directions, which is embedded in the core metal and which has a plurality of welds with the inner surface of the Coat is connected.

The inventive design of the electrode, in particular its current-carrying component in such a way that the one in question Contact structure embedded on the one hand in the core metal and on the other hand connected to the inner surface of the sheath via a plurality of welding points, there is an electrically good conductive connection between the core metal and the sheath metal with the consequence of a low voltage drop even at high voltages and high current intensities. 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 from a material that 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.

Triangular, rectangular, trapezoidal and other polygonal profiles, corrugated iron box profiles, pipes or the like are suitable as sheaths for the current-carrying components of the embodiment 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 is composed of two or more profile parts and these profile parts are welded to one another, the weld seams 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 or the like can be used as the contact structure or spatial structure. 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 intimately 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 can be transferred to the active surface of the metal anode. 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 a particularly high electrical load live components. 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. Thus, for example, in zinc electrowinning as a core metal for a current-carrying component of an electrode according to the invention, metallic zinc with its low melting point of 420 ° C and its good electrical conductivity of 156 x 1 ₀₃

proven excellent. In the event of a short circuit, 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 a current-carrying component designed in this way 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, a current-carrying rod is embedded in the cast metal for each core, which is 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 the 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 cannot be compared with the contact structure provided according to the invention, because they do not have a spatial structure oriented in different directions Represent surface areas on which the potting metal is shrunk. 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.

A further embodiment of the invention consists in that the effective surface of the electrode is formed by a plurality of profile bars arranged parallel to one another in one plane and the contact structure is formed by sections of the profile bars which is passed through the core of the current-carrying component.

This embodiment also differs from the known electrode according to US Pat. No. 4,260,470 in that, in the solution according to the invention, the sections of the profiled bars which are passed through the current-carrying component or its core are welded to the jacket of the current-carrying 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 transfer of the current. In addition, the sections of the profile bars, which act as a contact structure, can be designed with respect to their surface or shape so that they meet the requirements imposed on the contact structure according to the invention. Finally, they can have a contact coating.

• Fig. 1 den prinzipiellen Aufbau einer erfindungsgemäßen Elektrode,
• Fig. 2 einen Schnitt durch den Stromzuleiter der Elektrode nach Fig. 1 gemäß der Schnittlinie 11-11,
• 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 erfindungsgemäßen 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 11-11,
• 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,
• 6 shows a horizontal section through the effective area of the electrode according to FIG. 1 according to 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,
• 12 shows a horizontal section through the effective surface of a further exemplary embodiment of an electrode according to the invention, in which a current distributor is likewise integrated into the active part,
• 13 shows a vertical section through a further embodiment of an electrode according to the invention,
• 14 is a view of the electrode of 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,
• 17 shows a section through the electrode according to FIG. 16 along 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 with connected to the active part, generally designated 30, ie the active surface of the electrode. 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 firm mechanical connection and 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 strips 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 51 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. On the lower inner surface of the jacket 50, a strip 60 of expanded metal is arranged, which represents the contact structure and for this purpose is cast around the core metal 70 and is welded to the inner surface of the jacket 50.

FIG. 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 inward, 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.

FIG. 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 e.g. consist of two plates 31 which extend from the power 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 through a suitable core metal 70 poured out. The contact structure consists of pins 62, each of which has one or more thinnings or 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 into 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 welded to the corrugated sheet profile 33 in the area of its bends is.

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 the area 33a of the corrugated sheet profile 33, a strip 60 of expanded metal is placed as a contact structure, which is welded to the corrugated sheet profile 33a 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, the active part 30 is formed by two opposing corrugated sheet 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 welded to the corrugated sheet profiles 35 and 36 at intervals. 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.

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, an unrolled, 30 mm wide titanium expanded metal 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 sealed with a 3 mm thick welded titanium plate. A copper contact head is then attached to this titanium plate Silver braze soldered. 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 ² on the anode side. At a current of 390 A, only an ohmic voltage drop of approx. 50 mV occurs in the anode.

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 DA value (anodic current density) of approx. 235 A / m2 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 with approx. 18 mV at an anode-side current density of 120 A / m2 bring about not only the quality improvements in the electrolyte brown stone but also considerable energy savings per ton of product produced. In addition, there is a considerable saving in the amount of specific work required per ton of electrolyte brownstone produced, thanks to the easy removal 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 profiled sheet, a rolled, 20 mm wide titanium grating strip with the same grating characteristics as 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 to a rectangular profile jacket by means of a 1.5 mm thick sheet of titanium sheet of suitable dimensions. 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 with two 1150 mm long and 60 mm wide, flat areas arranged centrally in the two corrugated sheet 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 metal anode coated thereafter, which also expediently also bores which improve the electrolyte circulation is then sealed to the power supply in the area of the power distribution 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 causes the cell voltage to decrease the anode-side current density from 600 A / m ² to a D _A (anodic current density) of 400 A / m2.

Example 3

The following coated titanium anode has proven its worth in copper extraction electrolysis with a current density of 350 A / m ² on the anode side 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. Hot, molten aluminum was then poured into the open ends of the shells. After it solidified and the pouring holes were 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 (17)

1. Coated valve metal electrode for electrolytical recuperation of metal oxides,having

a) a current supply line and/or a current distributor which consists of a valve metal jacket,

b) a core which is arranged in, and is in electrical contact with said jacket and is made from a metal which is a good electrical conductor, and

c) a current carrying element which is embedded in the core metal,

d) said element (60-63) consisting of valve metal,

e) said element (60-63) having the form of a three-dimensional contact structure having surfaces orientated in several directions

f) which is embedded in the core metal (70), and

g) which is connected with the inner surface of the jacket (50) through a plurality of welds.

2. Electrode according to claim 1, characterized in that the contact structure is formed out of a strip (60) of expanded metal, wire mesh or perforated plate.

3. Electrode according to claim 2, characterized in that the strip (60) is installed in the current supply line and/or current distributor (10; 20) parallel to the direction of flow of the current.

4. Electrode according to claim 3, characterized in that the strip (60) made out of expanded metal extends in a straight line.

5. Electrode according to claim 3, characterized in that the strip (60) runs in a waved form.

6. Electrode according to claim 1, characterized in that the contact structure is formed from at least one wire (61) which is installed in a wave form in the direction of current flow of the current supply line alternatively the current distributor (10; 20) (Fig. 4, 6, 7, 10, 11,).

7. Electrode according to claims 1 and 2, characterized in that the contact structure is represented by a plurality of like bodies (62) with bulges (62b) and/or constrictions (62) (Fig. 8 and 9).

8. Electrode according to one of the preceding claims, characterized in that the contact structure (60 - 63) is provided with a coating which improves the electrical contact.

9. Electrode according to one of the preceding claims, characterized in that the core (70) consists of a metal, whose melting point lies at least 500° lower than the metal of the jacket (50).

10. Electrode according to one of the preceding claims, characterized in that the metal of the core (70) has a considerably higher electrical conductivity than the valve metal of the jacket (50).

11. Electrode according to one of the proceeding claims, characterized in that the component serving as the current distributor (20), is integrated in the active surface of the electrode such that the jacket is at least partly formed by the plate (30) representing the active surface of the electrode, and that a contact structure (60, 61) is arranged in a current carrying element formed in a similar way (Fig. 6, 10, to 12 and 15 to 17).

12. Electrode according to claim 11, characterized in that the contact structure (60) is welded to the area of the electrode plate (30) which at least partly forms the jacket (Fig. 12).

13. Electrode according to claim 11, characterized in that at least the area of the electrode plate (30) partly forming the coating has a U- or wave form and this area is completed by a cover plate (80; 81) to form the closed jacket (Fig. 10 and 12).

14. Electrode according to claim 13, characterized in that the cover plate (80; 81) is welded to the electrode plate.

15. Electrode according to one of the preceding claims, characterized in that the electrode plate is formed as a one piece or multi piece corrugated sheet (31).

16. Electrode according to one of the preceding claims, characterized in that the electrode plate which is formed as corrugated sheet (31) is welded on both sides to the jacket (50) of the current distributor (20).

17. Electrode according to claim 1, characterized in that the active surface of the electrode is represented by a plurality of profiled bars arranged parallel to each other and in one plane and that the contact structure is formed by sections (63) of the profiled bars (34), which run cross-wise through the core (70) of the current distributor (20).

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