EP0220557B1 - Inert composite electrode, particularly an anode for molten salt electrolysis - Google Patents

Inert composite electrode, particularly an anode for molten salt electrolysis Download PDF

Info

Publication number
EP0220557B1
EP0220557B1 EP86113930A EP86113930A EP0220557B1 EP 0220557 B1 EP0220557 B1 EP 0220557B1 EP 86113930 A EP86113930 A EP 86113930A EP 86113930 A EP86113930 A EP 86113930A EP 0220557 B1 EP0220557 B1 EP 0220557B1
Authority
EP
European Patent Office
Prior art keywords
active elements
composite electrode
elements
plate
electrode according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP86113930A
Other languages
German (de)
French (fr)
Other versions
EP0220557A1 (en
Inventor
Christine Dr. Zöllner
Herbert Hahn
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
C Conradty Nuernberg GmbH and Co KG
Original Assignee
C Conradty Nuernberg GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by C Conradty Nuernberg GmbH and Co KG filed Critical C Conradty Nuernberg GmbH and Co KG
Priority to AT86113930T priority Critical patent/ATE43366T1/en
Publication of EP0220557A1 publication Critical patent/EP0220557A1/en
Application granted granted Critical
Publication of EP0220557B1 publication Critical patent/EP0220557B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
    • C25C3/12—Anodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof
    • C25C7/025—Electrodes; Connections thereof used in cells for the electrolysis of melts

Definitions

  • the invention relates to an inert composite electrode, in particular anode for melt flow electrolysis, e.g. for the extraction of aluminum, magnesium, sodium, lithium, etc.
  • melt flow electrolysis e.g. In aluminum production, intensive development is underway to use so-called inert anodes, which consist in particular of oxide ceramics, for the electrolysis instead of the consumable carbon anodes.
  • the inert electrodes must, on the one hand, take into account the requirements of the existing cells that are still equipped with carbon anodes. This applies in particular with regard to the power supply line and the arrangement and / or the dimensioning of the active parts of the anodes. On the other hand, of course, the requirements made of the material from which the active parts of the inert anodes are made must also be taken into account. This applies in particular with regard to the physical parameters and the manufacturing technology.
  • An inert composite electrode of the type defined in the introduction is known from DE-PS 30 03 922. This essentially consists of an active part, an electrode holder and an arrangement for connecting the two first-mentioned assemblies.
  • the active part is formed by a plurality of rod-shaped active elements. These are arranged with their longitudinal axes parallel to one another and in groups aligned with one another. The total cross section perpendicular to the longitudinal axes of the active elements corresponds approximately to the corresponding cross section of a conventional carbon anode for a melt flow electrolysis cell.
  • the individual active elements consist of an oxide ceramic material.
  • a tubular support is provided to hold the active elements and to supply current to them.
  • a further tube is arranged concentrically in the latter, the lower end of which is provided with a base plate.
  • This base plate has a central bore through which a rod-shaped current feeder is passed, the lower end of which, below the base plate, is provided with a current-conducting pressure plate. With this pressure plate, the upper end faces of the active elements are brought into mechanical and electrical contact in a non-positive manner.
  • the active elements aligned in groups with one another each have a bore in their upper section, which are also aligned with one another with respect to a group.
  • a suspension rod the ends of which rest on a support plate, is passed through the mutually aligned bores of a group.
  • This support plate and the base plate mentioned are to be clamped using screw bolts, as a result of which the upper end faces of the active elements are brought into contact with the current-carrying pressure plate. If appropriate, an electrically highly conductive intermediate layer can be introduced between the end faces of the active elements and the pressure plate.
  • This known electrode construction has several serious disadvantages.
  • the production of the bores in the head sections of the active elements requires a greater production outlay. They can only be generated when the oxide ceramic active elements are green.
  • bores, in particular with regard to the alignment of the active elements arranged in groups are subject to greater tolerances, since such tolerances are already in the green state during the production of the active elements and further dimensional deviations are inevitable when the active elements are sintered.
  • the bores of a group of active elements are not exactly aligned, so that some of the active elements which are arranged one below the other on a suspension rod do not come into contact with their end faces, or do not come into sufficient contact with the current-carrying plate of the electrode holder.
  • the aforementioned weakening of the cross section of the active elements of the known anode also reduces the mechanical strength of the active elements, specifically in an area in which on the one hand the respective suspension rod exerts an increased compressive stress on the material of the active elements due to its prestressing and on the other hand also the highest tensile stresses due to the Weight of the active elements occur. Because of this, the greatest mechanical stresses act precisely in the area of the weakened cross section of the active elements, so that there is an increased risk of the electrode elements breaking at the point mentioned.
  • the active elements each have a head section on the plate side, which is essentially wedge-shaped in its cross section lying perpendicular to the line of alignment of a group and in the direction of the plate-side end face, and with each of the two opposing wedge surfaces of the head section of the respective active element, a tensioning element is brought into contact with a wedge surface whose wedge angle essentially corresponds to that of the respective wedge surface of the head section, so that a dovetail connection results.
  • the active part of the anode according to the invention is thus broken down into a plurality of rod-shaped active elements, as is known per se.
  • the active elements have a favorable design in terms of production technology, because the wedge-shaped head section complies with the design in ceramic technology, whereas the holes provided in the head section of the active elements of the known anode already cause a number of problems in terms of production technology, as has been explained above.
  • the active elements in the area of the wedge bracing are only subjected to pressure, which can be easily accommodated by the oxide ceramic material due to its high pressure resistance, especially since the cross section in the area of the active elements under pressure is enlarged due to the wedge shape of the head sections.
  • the tensile stresses due to the weight of the active elements can also be absorbed. Overall, this results in a mechanically very stable anode construction.
  • the wedge or dovetail bracing of the active elements by means of the clamping elements described also results in a self-adjusting effect, with the result that all of the active elements come with their end faces in intimate contact with the current-carrying plate, with bridging or due to compensation for any existing manufacturing tolerances. Due to the self-adjusting wedge tension between the active elements on the one hand and the tensioning elements or the plate on the other hand, any movements of the assemblies towards one another are compensated for due to the different thermal expansion coefficients of the materials, so that the end faces of the active elements also have intimate contact with the tensioning elements during operation of the anode and the current-carrying plate is preserved. In this way, a permanent and both electrically and mechanically optimal connection between the metallic power supply and the ceramic active elements is guaranteed.
  • the current transfer area between the current-carrying plate and the active elements is increased in that the tensioning elements are also in electrical connection with both the plate and the wedge surfaces of the electrode elements, so that the latter relate to the total contact area of the active elements enlarge the power supply accordingly. Due to the increased total contact area, the voltage drop is also reduced accordingly.
  • the current flow at this critical point is significantly improved.
  • the area utilization of the anode according to the invention is therefore very good, since the streamlines have a certain lateral wrap and the effective anode area is approximately equal to the projected anode area.
  • the anode elements consist of a material with thermistor properties
  • the special design of the material of the anode elements to increase the conductivity and the enlarged current transmission area is crucial for increasing the electrical efficiency.
  • the anode arrangement according to the invention therefore has a very good electrochemical efficiency.
  • Channels between the active elements are formed between the active elements arranged in groups, at least where the tensioning elements are provided.
  • the melt and the electrolyte can circulate in these channels in the region of the lower section of the active elements immersed in the melt or in the electrolyte, as a result of which an otherwise possible depletion of the electrolyte is effectively counteracted.
  • these channels provide enough space for the gas discharge so that the developed gas is quickly removed. Both contribute to an increase in the electrochemical efficiency of the process carried out with the electrodes according to the invention.
  • the active elements of a group can be in line with each other in their escape line.
  • only channels are formed between the active elements where there are clamping elements between the active elements.
  • the wedge-shaped widening of the head sections of the active elements has already largely reduced the voltage drop in the cold region. Nevertheless, it can still be advisable to design the electrical conductivity of the material of the active elements in the area of the head section higher than in the rest of the area, since these materials have thermistor properties. This is e.g. possible in that the material of the active elements in the region of the head section is a cermet, which is preferably tin oxide containing silver. The current conductivity in the critical head section of the active elements in the electrode according to the invention is thus further improved.
  • a contact layer in order to reduce the contact resistance between the current-carrying plate and the active elements even further, it can be advantageous for a contact layer to be introduced between the relevant main surface of the plate and the corresponding end faces of the active elements.
  • This can be formed by a network of highly conductive metal, in particular copper.
  • a continuous clamping element or separate clamping elements can be provided on both sides for each aligned group of active elements.
  • the tensioning element is designed for fastening two opposite active elements of two adjacent groups and for this purpose has two opposite wedge surfaces with an essentially mirror-image arrangement. This further reduces the effort in manufacturing and assembly
  • the mentioned clamping element can expediently be trapezoidal in cross section perpendicular to the line of alignment of the groups of active elements.
  • clamping elements are assigned to each active element and the length of a clamping element essentially corresponds to the length of an active element.
  • the plate is expediently cooled by water cooling, for which the plate is designed as a hollow body, within which channels for the cooling water are arranged.
  • the respective current feeder to the plate is guided through the interior of the hollow body and is electrically connected to the inside of the main surface with which the active elements are in contact.
  • the inert electrode according to the invention in particular anode for the melt flow electrolysis, essentially consists of three assemblies, namely an active part, generally designated 10, an electrode holder, generally designated 30, and an arrangement, generally designated 40, for connecting the two first-mentioned assemblies.
  • the active part consists of a plurality of rod-shaped active elements, which are generally designated 20. These are arranged with their longitudinal axes vertically aligned in the cell in the assembly position parallel to one another and in groups 11, 12, 13 etc. aligned with one another along the alignment line 25 (FIG. 3). They are essentially square or rectangular in their cross section perpendicular to their longitudinal axis. They consist of an electrically conductive and electrochemically active oxide ceramic material that can be described in more detail.
  • the active elements 20 each have a head section 21, which is widened by wedge surfaces 23 in its cross section lying perpendicular to the alignment line of a group and in the direction of the corresponding end face 22.
  • the essentially plate-shaped electrode holder 30 has a main surface 31, as seen in the electrolysis cell in the assembly position, on which the active elements 20 are mechanically and electrically kept in contact with their end surfaces 22. This is done with the aid of the connecting arrangement 40 representing tensioning elements 41. These tensioning elements are so trapezoidal in their cross section parallel to the longitudinal axis of the active elements 20 and perpendicular to the alignment line of a group that the two opposite wedge surfaces 42 with the wedge surfaces 23 lying at the same angle are two in two neighboring groups, e.g. 12, 13, opposite active elements 20 with appropriate bias are in contact.
  • the clamping elements 41 are screwed to the plate-shaped electrode holder 30 by means of screws.
  • two adjacent groups 11, 12, 13, etc. of active elements are spaced apart such that channels 50 are formed which, in the manner described, circulate the electrolyte or the melt between the lower ones, into the melt or into the electrolyte immersed sections 26 of the active elements 20 is made possible and, on the other hand, ensure rapid removal of the gas developed in the electrolysis process between the groups of active elements 20 arranged upwards.
  • the plate-shaped electrode holder 30 is designed as a hollow body, consisting of a lower horizontal plate 32, an upper plate 33 arranged parallel to the first and side walls 34 perpendicular thereto.
  • the cavity serves for the circulation of cooling water in the interior 35 of the electrode holder 30.
  • This is a cooling water Inlet pipe 36 is provided which opens into the interior 35 on the edge.
  • the cooling water circulates along spiral-shaped guide walls 37 through the interior 35 of the plate-shaped electrode holder 30 up to its central area and from there again into the peripheral area, from where the correspondingly heated cooling water is drawn off through a cooling water drain pipe 38.
  • the plate-shaped electrode holder 30 is further equipped with a plurality of current supply bolts 60, via which the electrical current is fed to the plate-shaped electrode holder 30 and is transmitted from there to the electrode elements 20.
  • a plurality of current supply bolts 60 via which the electrical current is fed to the plate-shaped electrode holder 30 and is transmitted from there to the electrode elements 20.
  • sleeves 61 are welded to the inner surface of the lower plate 33, which have an internal thread with which the lower and externally threaded section of the corresponding power supply bolt 60 is screwed.
  • protective sleeves 62 made of corrosion-resistant material.
  • a network 39 e.g. made of copper.
  • the plate-shaped electrode holder 30 and the clamping elements 41 and their clamping screws 43 are expediently made of steel. They can also consist of nickel or of steel or nickel alloys.
  • Cover elements are provided to protect these components against corrosion.
  • the cover elements 44 arranged on the underside of the tensioning elements are e.g. secured to the tensioning elements 41 by means of a dovetail guide.
  • the side cover elements 45 can be screwed to the front ends of the clamping elements 41 by screws 46.
  • the active elements 20 expediently consist of doped oxide ceramic, e.g. Tin oxide, nickel ferrite or yttrium oxide.
  • the side length of the upper cross section can expediently be between approximately 2 and 6 cm.
  • the length of the active elements can be between approx. 15 cm and approx. 40 cm.
  • the mentioned distance between Two groups of active elements can be between approx. 1 cm and approx. 2 cm.
  • the wedge angle of the head section of the respective active elements can be between approximately 5 ° and approximately 25 ° .

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Resistance Heating (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)

Abstract

An inert composite electrode, such as an anode, for molten salt electrolysis consists of an active part in the form of a plurality of bar-shaped active elements, in particular of ceramic oxide, which are arranged with their longitudinal axes mutually parallel and in mutually aligned groups, an electrode holder which comprises a current-conducting plate, with one main surface of which the active elements are in firm contact with their end surfaces, and a joining arrangement which joins the active elements together in groups and holds them in contact with the plate. This composite electrode is characterized in that the active elements each have a head section adjacent to the plate which is widened in the direction of the end surfaces adjacent to the plate substantially in a wedge shape considered in cross-sections lying perpendicular to the line of alignment of a group, and in that a clamping element has a wedging surface which is brought into contact with each of the two oppositely-lying wedging surfaces of the head section of the respective active element, the wedging angle of the clamping element substantially corresponding to that of the respective wedging surface of the head section.

Description

Die Erfindung betrifft eine inerte Verbundelektrode, insbesondere Anode für die Schmelzflußelektrolyse, z.B. für die Gewinnung von Aluminium, Magnesium, Natrium, Lithium, u.a. bestehend aus einem Aktivteil in Form einer Mehrzahl von stabförmigen Aktivelementen, insbesondere aus Oxidkeramik, die mit ihren Längsachsen parallel nebeneinander und in zueinander fluchtenden Gruppen angeordnet sind, einem Elektrodenhalter, der eine stromleitende Platte umfaßt, mit deren einen Hauptfläche die Elektrodenelemente mit ihren Stirnflächen kraftschlüssig in Kontakt stehen, und einer Verbindungsanordnung, die die Aktivelemente gruppenweise untereinander verbindet und mit der Platte in Kontakt hält.The invention relates to an inert composite electrode, in particular anode for melt flow electrolysis, e.g. for the extraction of aluminum, magnesium, sodium, lithium, etc. Consisting of an active part in the form of a plurality of rod-shaped active elements, in particular made of oxide ceramics, which are arranged with their longitudinal axes parallel to one another and in groups aligned with one another, an electrode holder which comprises a current-conducting plate, with one main surface of which the electrode elements with their end faces in a force-fitting manner Stand contact, and a connection arrangement that connects the active elements in groups to each other and keeps in contact with the plate.

In der Schmelzflußelektrolyse, z.B. bei der Aluminiumerzeugung, ist eine intensive Entwicklung im Gange, für die Elektrolyse anstelle der sich verzehrenden Anoden aus Kohlenstoff sogenannte inerte Anoden, die insbesondere aus Oxidkeramik bestehen, einzusetzen.In melt flow electrolysis, e.g. In aluminum production, intensive development is underway to use so-called inert anodes, which consist in particular of oxide ceramics, for the electrolysis instead of the consumable carbon anodes.

Für diese Entwicklung bilden eine Reihe von Vorteilen den Anreiz:

  • - Bei Herstellung und bei Betrieb der inerten Anoden ergibt sich eine erhebliche Energieeinsparung.
  • - Zugleich wird Rohstoff eingespart. Bei der Herstellung muß nicht auf fossilen Rohstoff Erdöl, aus dem dann Petrol, Koks und Pech gewonnen wird, zurückgegriffen werden. Beim Betrieb der inerten Anoden ergibt sich kein oder nur ein sehr geringer Verbrauch an Anodenmaterial. Damit fallen des weiteren Investitionen und Betriebskosten für die Anodenfabrikation weg.
  • - Da der sich bei verzehrenden Anoden turnusgemäß notwendige Anodenwechsel entbehrlich wird, können die Zellen geschlossener gefahren werden. Dadurch verbessern sich die Arbeitsbedingungen.
  • - Die Abluft aus den Zellen enthält weder Schwefeldioxid noch polyaromatische Kohlenwasserstoffe. Aus dem geschlossenen Abluftsystem können die Fluoride leichter zurückgewonnen werden.
  • - Schließlich können inerte Anoden mit höheren Stromdichten als Kohlenstoffanoden gefahren werden. Dadurch erhöht sich die Produktionskapazität auf weniger Fläche und/oder in weniger Zeit.
There are a number of advantages to this development:
  • - Considerable energy savings result from the manufacture and operation of the inert anodes.
  • - At the same time, raw material is saved. It is not necessary to make use of fossil fuels such as petroleum, from which petroleum, coke and pitch are extracted. The operation of the inert anodes results in little or no consumption of anode material. This also eliminates investments and operating costs for anode production.
  • - Since the anode change, which is required as part of the rotation when the anodes are consumed, can be dispensed with, the cells can be driven more closed. This improves working conditions.
  • - The exhaust air from the cells contains neither sulfur dioxide nor polyaromatic hydrocarbons. The fluorides can be recovered more easily from the closed exhaust system.
  • - Finally, inert anodes with higher current densities than carbon anodes can be used. This increases the production capacity in less space and / or in less time.

Konstruktiv müssen die inerten Elektroden einerseits den Vorgaben der bereits vorhandenen, noch mit Kohlenstoffanoden ausgerüsteten Zellen Rechnung tragen. Dies gilt insbesondere in bezug auf die Stromzuleitung und die Anordnung und/oder die Dimensionierung der Aktivteile der Anoden. Andererseits müssen aber natürlich auch die Erfordernisse, die aus dem Werkstoff, aus dem die Aktivteile der inerten Anoden bestehen, Berücksichtigung finden. Dies gilt insbesondere in bezug auf die physikalischen Parameter und die Herstellungstechnologie.In terms of construction, the inert electrodes must, on the one hand, take into account the requirements of the existing cells that are still equipped with carbon anodes. This applies in particular with regard to the power supply line and the arrangement and / or the dimensioning of the active parts of the anodes. On the other hand, of course, the requirements made of the material from which the active parts of the inert anodes are made must also be taken into account. This applies in particular with regard to the physical parameters and the manufacturing technology.

Eine inerte Verbundelektrode der eingangs definierten Art ist aus der DE-PS 30 03 922 bekannt. Diese besteht im wesentlichen aus einem Aktivteil, einem Elektrodenhalter und einer Anordnung zum Verbinden der zwei erstgenannten Baugruppen.An inert composite electrode of the type defined in the introduction is known from DE-PS 30 03 922. This essentially consists of an active part, an electrode holder and an arrangement for connecting the two first-mentioned assemblies.

Der Aktivteil ist durch eine Mehrzahl von stabförmigen Aktivelementen gebildet. Diese sind mit ihren Längsachsen parallel nebeneinander und in zueinander fluchtenden Gruppen angeordnet. Der zu den Längsachsen der Aktivelemente senkrechte Gesamtquerschnitt entspricht in etwa dem entsprechenden Querschnitt einer herkömmlichen Kohlenstoffanode für eine Schmelzflußelektrolysezelle. Die einzelnen Aktivelemente bestehen aus einem oxidkeramischen Werkstoff.The active part is formed by a plurality of rod-shaped active elements. These are arranged with their longitudinal axes parallel to one another and in groups aligned with one another. The total cross section perpendicular to the longitudinal axes of the active elements corresponds approximately to the corresponding cross section of a conventional carbon anode for a melt flow electrolysis cell. The individual active elements consist of an oxide ceramic material.

Zur Halterung der Aktivelemente und zur Stromzuführung zu diesen ist ein rohrförmiger Träger vorgesehen. In diesen ist konzentrisch ein weiteres Rohr angeordnet, dessen unteres Ende mit einer Bodenplatte versehen ist. Diese Bodenplatte weist eine zentrische Bohrung auf, durch die ein stabförmiger Stromzuleiter hindurchgeführt ist, dessen unteres, unterhalb der Bodenplatte endendes Ende mit einer stromleitenden Anpreßplatte versehen ist. Mit dieser Anpreßplatte werden die oberen Stirnflächen der Aktivelemente auf kraftschlüssige Weise in mechanischen und elektrischen Kontakt gebracht. Hierzu weisen die gruppenweise untereinander fluchtenden Aktivelemente in ihrem oberen Abschnitt je eine Bohrung auf, die in bezug auf eine Gruppen ebenfalls zueinander fluchten. Durch die zueinander fluchtenden Bohrungen einer Gruppe ist jeweils ein Aufhängestab hindurchgeführt, dessen Enden auf einer Auflageplatte aufliegen. Diese Auflageplatte und die genannte Bodenplatte sind über Schraubbolzen zu verspannen, wodurch die oberen Stirnflächen der Aktivelemente in Kontakt mit der stromführenden Anpreßplatte gebracht werden. Gegebenenfalls kann zwischen den Stirnflächen der Aktivelemente und der Anpreßplatte eine elektrisch gut leitende Zwischenschicht eingebracht sein.A tubular support is provided to hold the active elements and to supply current to them. A further tube is arranged concentrically in the latter, the lower end of which is provided with a base plate. This base plate has a central bore through which a rod-shaped current feeder is passed, the lower end of which, below the base plate, is provided with a current-conducting pressure plate. With this pressure plate, the upper end faces of the active elements are brought into mechanical and electrical contact in a non-positive manner. For this purpose, the active elements aligned in groups with one another each have a bore in their upper section, which are also aligned with one another with respect to a group. A suspension rod, the ends of which rest on a support plate, is passed through the mutually aligned bores of a group. This support plate and the base plate mentioned are to be clamped using screw bolts, as a result of which the upper end faces of the active elements are brought into contact with the current-carrying pressure plate. If appropriate, an electrically highly conductive intermediate layer can be introduced between the end faces of the active elements and the pressure plate.

Diese bekannte Elektrodenkonstruktion weist mehrere gravierende Nachteile auf.This known electrode construction has several serious disadvantages.

Zum einen ist ihr Aufbau insgesamt relativ kompliziert, insbesondere in bezug auf die Aufhängestäbe, die durch die Bohrungen im Kopfabschnitt der Aktivelemente hindurchgeführt sind und entsprechend gelagert und gespannt werden müssen.On the one hand, their overall structure is relatively complicated, in particular with regard to the suspension rods, which are passed through the bores in the head section of the active elements and must be appropriately stored and tensioned.

Des weiteren erfordert die Herstellung der Bohrungen in den Kopfabschnitten der Aktivelemente einen größeren Herstellungsaufwand. Sie sind nur im Grünzustand der oxidkeramischen Aktivelemente zu erzeugen. Des weiteren sind Bohrungen, insbesondere in bezug auf die Fluchtung der in Gruppen angeordneten Aktivelemente, mit größeren Toleranzen behaftet, da derartige Toleranzen schon bei der Herstellung der Aktivelemente im Grünzustand eingehen und des weiteren beim Sintern der Aktivelemente weitere Maßabweichungen unvermeidlich sind. Dies hat zur Folge, daß die Bohrungen einer Gruppe von Aktivelementen nicht genau fluchten, so daß einige der Aktivelemente, die an einem Aufhängestab untereinander gereiht sind, nicht oder nicht genügend mit ihren Stirnflächen in Kontakt mit der stromführenden Platte des Elektrodenhalters gelangen. Dies gilt dann umso mehr im Betrieb, wo sich die unterschiedlichen Ausdehnungskoeffizienten der Werkstoff der Aktivelemente einerseits und der stromzuführenden Platte andererseits verstärkt negativ in bezug auf die Kontaktierung zwischen den Stirnflächen der Aktivelemente und der Platte auswirken. Dadurch ergibt sich ein erhöhter Spannungsabfall mit der Folge, daß der elektrische Wirkungsgrad sinkt.Furthermore, the production of the bores in the head sections of the active elements requires a greater production outlay. They can only be generated when the oxide ceramic active elements are green. Furthermore, bores, in particular with regard to the alignment of the active elements arranged in groups, are subject to greater tolerances, since such tolerances are already in the green state during the production of the active elements and further dimensional deviations are inevitable when the active elements are sintered. As a result, the bores of a group of active elements are not exactly aligned, so that some of the active elements which are arranged one below the other on a suspension rod do not come into contact with their end faces, or do not come into sufficient contact with the current-carrying plate of the electrode holder. This is all the more true in operation, where the different coefficients of expansion of the material of the active elements on the one hand and the current-carrying plate on the other hand ver strengthens negatively in relation to the contact between the end faces of the active elements and the plate. This results in an increased voltage drop, with the result that the electrical efficiency drops.

Dieser Nachteil wird noch dadurch verschärft, daß die Bohrungen die Querschnittsfläche parallel zur Längsachse der Aktivelemente verkleinern, und zwar gerade im kalten Bereich der Aktivelemente. Dadurch werden gerade dort die Strombahnen eingeschnürt.This disadvantage is exacerbated by the fact that the bores reduce the cross-sectional area parallel to the longitudinal axis of the active elements, specifically in the cold region of the active elements. As a result, the current paths are constricted there.

Die genannte Schwächung des Querschnittes der Aktivelemente der bekannten Anode vermindert auch die mechanische Festigkeit der Aktivelemente, und zwar in einem Bereich, in dem einerseits der jeweilige Aufhängestab aufgrund dessen Vorspannung einer erhöhte Druckspannung auf den Werkstoff der Aktivelemente ausübt und andererseits auch die höchsten Zugspannungen aufgrund des Gewichtes der Aktivelemente auftreten. Aufgrund dessen wirken die größten mechanischen Spannungen gerade im Bereich des geschwächten Querschnitts der Aktivelemente, so daß eine erhöhte Gefahr des Bruches der Elektrodenelemente an der genannten Stelle gegeben ist.The aforementioned weakening of the cross section of the active elements of the known anode also reduces the mechanical strength of the active elements, specifically in an area in which on the one hand the respective suspension rod exerts an increased compressive stress on the material of the active elements due to its prestressing and on the other hand also the highest tensile stresses due to the Weight of the active elements occur. Because of this, the greatest mechanical stresses act precisely in the area of the weakened cross section of the active elements, so that there is an increased risk of the electrode elements breaking at the point mentioned.

Schließlich ist bei der bekannten Anodenkonstruktion kein bzw. wenig Augenmerk gerichtet auf die notwendige Elektrolytbewegung im Bereich der in die Schmelze eintauchenden unteren Abschnitte der Elektrodenelemente sowie auf die Gasabfuhr im Bereich der Elektrodenelemente.Finally, in the known anode construction, little or no attention is paid to the necessary electrolyte movement in the region of the lower sections of the electrode elements immersed in the melt and to the gas removal in the region of the electrode elements.

Es ist Aufgabe der Erfindung, eine inerte Verbundelektrode der vorausgesetzten Art zu schaffen, bei der die oxidkeramischen Aktivelemente unter Berücksichtigung der Werkstoff- und Herstellungstechnologie für Oxidkeramik gestaltet sind, die einen einfachen Aufbau besitzt und leicht montierbar ist sowie einen guten elektrochemischen Wirkungsgrad aufweist.It is an object of the invention to provide an inert composite electrode of the presupposed type in which the oxide ceramic active elements are designed taking into account the material and manufacturing technology for oxide ceramics, which has a simple structure and is easy to assemble and has a good electrochemical efficiency.

Diese Aufgabe wird bei einer inerten Verbundelektrode mit den eingangs genannten Merkmalen dadurch gelöst, daß die Aktivelemente jeweils plattenseitig einen Kopfabschnitt aufweisen, der in seinem senkrecht zur Fluchtlinie einer Gruppe liegenden Querschnitt und in Richtung der plattenseitigen Stirnfläche im wesentlichen keilförmig verbreitert ist, und mit jeder der zwei gegenüberliegenden Keilflächen des Kopfabschnitts des jeweiligen Aktivelements ein Spannelement mit einer Keilfläche in Anlage gebracht ist, deren Keilwinkel dem der jeweiligen Keilfäche des Kopfabschnittes im wesentlichen entspricht, so daß sich eine Schwalbenschwanz-Verbindung ergibt.This object is achieved in the case of an inert composite electrode with the features mentioned at the outset in that the active elements each have a head section on the plate side, which is essentially wedge-shaped in its cross section lying perpendicular to the line of alignment of a group and in the direction of the plate-side end face, and with each of the two opposing wedge surfaces of the head section of the respective active element, a tensioning element is brought into contact with a wedge surface whose wedge angle essentially corresponds to that of the respective wedge surface of the head section, so that a dovetail connection results.

Der Aktivteil der erfindungsgemäßen Anode ist also aufgelöst in eine Mehrzahl von stabförmigen Aktivelementen, wie dies an sich bekannt ist. Die Aktivelemente sind herstellungstechnologisch günstig gestaltet, weil der keilförmige Kopfabschnitt der Gestaltung in der Keramik-Technologie entgegenkommt, wohingegen die im Kopfabschnitt der Aktivelemente der bekannten Anode vorgesehenen Bohrungen schon herstellungstechnisch eine Reihe von Problemen verursachen, wie oben dargelegt wurde.The active part of the anode according to the invention is thus broken down into a plurality of rod-shaped active elements, as is known per se. The active elements have a favorable design in terms of production technology, because the wedge-shaped head section complies with the design in ceramic technology, whereas the holes provided in the head section of the active elements of the known anode already cause a number of problems in terms of production technology, as has been explained above.

Im montierten Zustand sind die Aktivelemente im Bereich der Keilverspannung ausschließlich auf Druck beansprucht, was durch den oxidkeramischen Werkstoff aufgrund dessen hoher Druckfestigkeit ohne weiteres aufgenommen werden kann, zumal der Querschnitt im druckbeaufschlagten Bereich der Aktivelemente aufgrund der Keilform der Kopfabschnitte vergrößert ist. Als Folge der Querschnittsvergrößerung im Einspannbereich der Aktivelemente können auch die Zugspannungen aufgrund des Gewichtes der Aktivelemente gut aufgenommen werden. Insgesamt ergibt sich also eine mechanisch sehr stabile Anodenkonstruktion.In the assembled state, the active elements in the area of the wedge bracing are only subjected to pressure, which can be easily accommodated by the oxide ceramic material due to its high pressure resistance, especially since the cross section in the area of the active elements under pressure is enlarged due to the wedge shape of the head sections. As a result of the increase in cross section in the clamping area of the active elements, the tensile stresses due to the weight of the active elements can also be absorbed. Overall, this results in a mechanically very stable anode construction.

Die Keil- bzw. Schwalbenschwanzverspannung der Aktivelemente mittels der beschriebenen Spannelemente ergibt zugleich einen selbstjustierenden Effekt mit der Folge, daß sämtliche der Aktivelemente mit ihren Stirnflächen in innigen Kontakt mit der stromführenden Platte gelangen, und zwar unter Überbrückung bzw. aufgrund Ausgleichs eventuell bestehender Fertigungstoleranzen. Aufgrund der selbstjustierenden Keilverspannung zwischen den Aktivelementen einerseits und den Spannelementen bzw. der Platte andererseits werden des weiteren eventuelle Bewegungen der Baugruppen zueinander aufgrund der unterschiedlichen thermischen Ausdehnungskoeffizienten der Werkstoffe ausgeglichen, so daß auch im Betrieb der Anode ein inniger Kontakt der Stirnflächen der Aktivelemente mit den Spannelementen und der stromzuführenden Platte erhalten bleibt. Auf diese Weise ist eine dauerhafte und sowohl elektrisch als auch mechanisch optimale Verbindung zwischen der metallischen Stromzuführung und den keramischen Aktivelementen gewährleistet.The wedge or dovetail bracing of the active elements by means of the clamping elements described also results in a self-adjusting effect, with the result that all of the active elements come with their end faces in intimate contact with the current-carrying plate, with bridging or due to compensation for any existing manufacturing tolerances. Due to the self-adjusting wedge tension between the active elements on the one hand and the tensioning elements or the plate on the other hand, any movements of the assemblies towards one another are compensated for due to the different thermal expansion coefficients of the materials, so that the end faces of the active elements also have intimate contact with the tensioning elements during operation of the anode and the current-carrying plate is preserved. In this way, a permanent and both electrically and mechanically optimal connection between the metallic power supply and the ceramic active elements is guaranteed.

Dadurch wird der Spannungsabfall zwischen der stromzuleitenden Platte und den Stirnflächen der Aktivelemente minimiert.This minimizes the voltage drop between the current-carrying plate and the end faces of the active elements.

Darüber hinaus ist bei der erfindungsgemäßen Anode die Stromübertragungsfläche zwischen der stromführenden Platte und den Aktivelementen dadurch vergrößert, daß die Spannelemente ebenfalls in elektrischer Verbindung sowohl zur Platte als auch zu den Keilflächen der Elektrodenelemente stehen, so daß letztere die Gesamt-Kontaktfläche der Aktivelemente in bezug auf das stromzuführende Bauteil entsprechend vergrößern. Aufgrund der vergrößerten Gesamt-Kontaktfläche wird auch dementsprechend der Spannungsabfall verkleinert.In addition, in the anode according to the invention, the current transfer area between the current-carrying plate and the active elements is increased in that the tensioning elements are also in electrical connection with both the plate and the wedge surfaces of the electrode elements, so that the latter relate to the total contact area of the active elements enlarge the power supply accordingly. Due to the increased total contact area, the voltage drop is also reduced accordingly.

Aufgrund der schon angesprochenen Querschnittsvergrößerung im Kopfabschnitt der Aktivelemente, d.h. gerade im kalten Bereich derselben, ist die Stromführung an dieser kritischen Stelle entscheidend verbessert. Die Flächennutzung der erfindungsgemäßen Anode ist also sehr gut, da die Stromlinien einen gewissen seitlichen Umgriff haben und die wirksame Anodenfläche in etwa gleich der projizierten Anodenfläche ist.Due to the already mentioned cross-sectional enlargement in the head section of the active elements, i.e. Especially in the cold area, the current flow at this critical point is significantly improved. The area utilization of the anode according to the invention is therefore very good, since the streamlines have a certain lateral wrap and the effective anode area is approximately equal to the projected anode area.

Nachdem die Anodenelemente aus einem Werkstoff mit Heißleiter-Eigenschaften bestehen, sind die im kalten, d.h. nicht gutleitenden Bereich der Anodenelemente getroffenen Maßnahmen zur Erhöhung der Leitfähigkeit, nämlich die Querschnittsvergrößerung im Kopfabschnitt der Anodenelemente, die spezielle Ausbildung des Werkstoffes der Anodenelemente zur Erhöhung der Leitfähigkeit und die vergrößerte Stromübertragungsfläche entscheidend zur Erhöhung des elektrischen Wirkungsgrads. Insgesamt weist also die erfindungsgemäße Anodenanordnung einen sehr guten elektrochemischen Wirkungsgrad auf.After the anode elements consist of a material with thermistor properties, the measures taken to increase the conductivity in the cold, i.e. non-conductive area of the anode elements, namely the cross-sectional enlargement in the head section of the anode elements, the special design of the material of the anode elements to increase the conductivity and the enlarged current transmission area is crucial for increasing the electrical efficiency. Overall, the anode arrangement according to the invention therefore has a very good electrochemical efficiency.

Zwischen den gruppenweise angeordneten Aktivelementen sind mindestens dort, wo die Spannelemente vorgesehen sind, Kanäle zwischen den Aktivelementen ausgebildet. Einerseits kann im Bereich der in die Schmelze bzw. in den Elektrolyt eintauchenden unteren Abschnitt der Aktivelemente in diesen Kanälen die Schmelze und der Elektrolyt zirkulieren, wodurch einer sonst möglichen Verarmung des Elektrolyts effektiv entgegengewirkt wird. Andererseits stellen diese Kanäle für die Gasabfuhr genug Raum zur Verfügung, so daß das entwickelte Gas schnell abgeführt wird. Beides trägt zu einer Erhöhung des elektrochemischen Wirkungsgrads des mit den erfindungsgemäßen Elektroden durchgeführten Prozesses bei.Channels between the active elements are formed between the active elements arranged in groups, at least where the tensioning elements are provided. On the one hand, the melt and the electrolyte can circulate in these channels in the region of the lower section of the active elements immersed in the melt or in the electrolyte, as a result of which an otherwise possible depletion of the electrolyte is effectively counteracted. On the other hand, these channels provide enough space for the gas discharge so that the developed gas is quickly removed. Both contribute to an increase in the electrochemical efficiency of the process carried out with the electrodes according to the invention.

Zweckmäßige Ausbildungen der erfindungsgemäßen Verbundelektrode ergeben sich aus den übrigen Ansprüchen.Appropriate designs of the composite electrode according to the invention result from the remaining claims.

So können beispielsweise die Aktivelemente einer Gruppe in deren Fluchtlinie untereinander in Anlage stehen. Es sind also nur Kanäle zwischen den Aktivelementen dort gebildet, wo Spannelemente zwischen den Aktivelementen liegen. Dadurch ergibt sich einerseits ein sehr kompakter Aufbau des Aktivteils der erfindungsgemäßen Anode, andererseits ist aber auch ausreichend einer entsprechenden Bewegung der Schmelze und des Elektrolyts sowie der Gasabfuhr Rechnung getragen.For example, the active elements of a group can be in line with each other in their escape line. Thus, only channels are formed between the active elements where there are clamping elements between the active elements. This results on the one hand in a very compact structure of the active part of the anode according to the invention, but on the other hand sufficient consideration is also given to a corresponding movement of the melt and of the electrolyte and of the gas removal.

Zwar ist durch die keilförmige Verbreiterung der Kopfabschnitte der Aktivelemente bereits der Spannungsabfall im kalten Bereich weitgehend reduziert. Trotzdem kann es sich noch empfehlen, die elektrische Leitfähigkeit des Werkstoffes der Aktivelemente im Bereich des Kopfabschnittes höher auszulegen als im übrigen Bereich, nachdem diese Werkstoffe Heißleiter eigenschaften besitzen. Dies ist z.B. dadurch möglich, daß der Werkstoff der Aktivelemente im Bereich des Kopfabschnittes ein Cermet ist, das vorzugsweise Silber enthaltendes Zinnoxid ist. Damit ist die Stromleitfähigkeit im kritischen Kopfabschnitt der Aktivelemente bei der erfindungsgemäßen Elektrode noch weiter verbessert.The wedge-shaped widening of the head sections of the active elements has already largely reduced the voltage drop in the cold region. Nevertheless, it can still be advisable to design the electrical conductivity of the material of the active elements in the area of the head section higher than in the rest of the area, since these materials have thermistor properties. This is e.g. possible in that the material of the active elements in the region of the head section is a cermet, which is preferably tin oxide containing silver. The current conductivity in the critical head section of the active elements in the electrode according to the invention is thus further improved.

Um den Übergangswiderstand zwischen der stromzuleitenden Platte und den Aktivelementen noch weiter zu verkleinern, kann es von Vorteil sein, daß zwischen der betreffenden Hauptfläche der Platte und den entsprechenden Stirnflächen der Aktivelemente eine Kontaktschicht eingebracht ist. Diese kann durch ein Netz aus gut leitendem Metal, insbesondere Kupfer, gebildet sein.In order to reduce the contact resistance between the current-carrying plate and the active elements even further, it can be advantageous for a contact layer to be introduced between the relevant main surface of the plate and the corresponding end faces of the active elements. This can be formed by a network of highly conductive metal, in particular copper.

Es kann für jede fluchtende Gruppe von Aktivelementen beidseitig je ein durchgehendes Spannelement oder aber separate Spannelemente vorgesehen sein. Es ist aber auch möglich, daß das Spannelement zur Befestigung von zwei gegenüberliegenden Aktivelementen zweier benachbarter Gruppen ausgebildet ist und hierzu zwei gegenüberliegende Keilflächen mit im wesentlichen spiegelbildlicher Anordnung aufweist. Dadurch erniedrigt sich der Aufwand in der Fertigung und in der Montage weiterA continuous clamping element or separate clamping elements can be provided on both sides for each aligned group of active elements. However, it is also possible that the tensioning element is designed for fastening two opposite active elements of two adjacent groups and for this purpose has two opposite wedge surfaces with an essentially mirror-image arrangement. This further reduces the effort in manufacturing and assembly

Das angesprochene Spannelement kann zweckmäßigerweise im Querschnitt senkrecht zur Fluchtlinie der Gruppen der Aktivelemente trapezförmig ausgebildet sein.The mentioned clamping element can expediently be trapezoidal in cross section perpendicular to the line of alignment of the groups of active elements.

Des weiteren sind jedem Aktivelement je zwei separate Spannelemente zugeordnet und die Länge eines Spannelements entspricht im wesentlichen der Länge eines Aktivelements.Furthermore, two separate clamping elements are assigned to each active element and the length of a clamping element essentially corresponds to the length of an active element.

Es ist aber auch möglich, daß für jeweils eine Gruppe von Aktivelementen je zwei durchgehende Spannelemente vorgesehen sind und die Länge eines Spannelementes der Länge einer Gruppe von Aktivelementen im wesentlichen entspricht.However, it is also possible that two continuous tensioning elements are provided for each group of active elements and the length of a tensioning element essentially corresponds to the length of a group of active elements.

Für eine schnelle Montage und Demontage empfiehlt es sich, daß die Spannelemente mittels Schrauben an der Platte befestigt sind.For quick assembly and disassembly, it is recommended that the clamping elements are attached to the plate using screws.

Zur Vermeidung von Korrosion aufgrung der in der Zelle vorhandenen aggressiven Gase und der hohen Temperaturen ist es natürlich zweckmäßig, nicht nur die dem Zelleninneren zugekehrten Bereiche der stromführenden Platte, sondern auch die Spannelemente einschließlich ihrer Befestigungselemente durch Abdeckelemente aus korrosionsbeständigem Werkstoff zu schützen. Es bieten sich Keramik-Grafit-Verbundmaterialien an, z.B. Tongrafit.To avoid corrosion due to the aggressive gases present in the cell and the high temperatures, it is of course expedient not only to protect the areas of the current-carrying plate which face the interior of the cell, but also the clamping elements, including their fastening elements, by means of cover elements made of corrosion-resistant material. Ceramic-graphite composite materials are available, e.g. Tongraphite.

Schließlich ist es von erheblichem Vorteil, die stromzuführende Platte zu kühlen. Dadurch ist es möglich, den Elektrodenhalter so dicht wie möglich an die Schmelze heranzuführen und trotzdem die Kontakttemperatur zwischen Platte und Aktivelemente unter 250°C zu halten. Dies ist insbesondere dann erforderlich, wenn die Anode mit höherer Strombelastung ge fahren wird, da bekanntlich die Temperatur der Elektroden quadratisch mit der Strombelastung steigt. Bevorzugt sollte die Kühlung so ausgelegt sein, daß ca. 30 bis 35 % der Gesamtwärme über die Anodenoberfläche abgeführt werden. Der Vorteil des möglichst nahen Heranführens des Elektrodenhalters ist natürlich darin zu sehen, daß die Aktivelemente dadurch kurz ausgebildet werden können, wodurch einerseits teurer Werkstoff eingespart werden kann und andererseits der Spannungsabfall in den Aktivelementen weiter erniedrigt wird.Finally, it is of considerable advantage to cool the current supply plate. This makes it possible to bring the electrode holder as close as possible to the melt and still keep the contact temperature between the plate and active elements below 250 ° C. This is particularly necessary if the anode will drive with a higher current load, since it is known that the temperature of the electrodes increases quadratically with the current load. The cooling should preferably be designed such that approximately 30 to 35% of the total heat is dissipated via the anode surface. The advantage of moving the electrode holder as close as possible is of course to be seen in the fact that the active elements can be made short as a result, which on the one hand saves expensive material and on the other hand further reduces the voltage drop in the active elements.

Zweckmäßigerweise wird die Kühlung der Platte durch eine Wasserkühlung verwirklicht, wofür die Platte als Hohlkörper ausgebildet ist, innerhalb dem Kanäle für das Kühlwasser angeordnet sind. In diesem Fall ist es schließlich zweckmäßig, daß der jeweilige Stromzuleiter zur Platte durch das Innere des Hohlkörpers hindurchgeführt und mit der Innenseite der Hauptfläche, mit der die Aktivelemente in Kontakt stehen, elektrisch verbunden ist.The plate is expediently cooled by water cooling, for which the plate is designed as a hollow body, within which channels for the cooling water are arranged. In this case, it is finally expedient that the respective current feeder to the plate is guided through the interior of the hollow body and is electrically connected to the inside of the main surface with which the active elements are in contact.

Weitere Vorteile und Einzelheiten der erfindungsgemäßen Verbundelektrode ergeben sich anhand der Beschreibung der Zeichnung und der Erläuterung eines speziellen Ausführungsbeispiels.Further advantages and details of the composite electrode according to the invention result from the description of the drawing and the explanation of a special exemplary embodiment.

In den Zeichnungen zeigt:

  • Fig. 1 eine perspektivische Darstellung eines Ausführungsbeispiels der erfindungsgemäßen Verbundelektrode,
  • Fig. 2 eine teilweise geschnittene Seitenansicht der erfindungsgemäßen Verbundelektrode, und
  • Fig. 3 die Ansicht A und den Schnitt B-B entsprechend der Fig. 2.
In the drawings:
  • 1 is a perspective view of an embodiment of the composite electrode according to the invention,
  • Fig. 2 is a partially sectioned side view of the composite electrode according to the invention, and
  • 3 shows the view A and the section BB corresponding to FIG. 2nd

Die erfindungsgemäße inerte Elektrode, insbesondere Anode für die Schmelzflußelektrolyse, besteht im wesentlichen aus drei Baugruppen, nämlich einem insgesamt mit 10 bezeichneten Aktivteil, einem insgesamt mit 30 bezeichneten Elektrodenhalter und einer insgesamt mit 40 bezeichneten Anordnung zum Verbinden der zwei erstgenannten Baugruppen.The inert electrode according to the invention, in particular anode for the melt flow electrolysis, essentially consists of three assemblies, namely an active part, generally designated 10, an electrode holder, generally designated 30, and an arrangement, generally designated 40, for connecting the two first-mentioned assemblies.

Der Aktivteil besteht aus einer Mehrzahl von stabförmigen Aktivelementen, die allgemein mit 20 bezeichnet sind. Diese sind mit ihren in der Montagestellung in der Zelle vertikal ausgerichteten Längsachsen parallel nebeneinander und in zueinander längs der Fluchtlinie 25 (Fig. 3) fluchtenden Gruppen 11, 12, 13 usw. angeordnet. Sie sind in ihrem zu ihrer Längsachse senkrechten Querschnitt im wesentlichen quadratisch bzw. rechteckförmig. Sie bestehen aus einem noch näher zu bezeichnenden, elektrisch leitenden und elektrochemisch aktiven oxidkeramischen Werkstoff. Die Aktivelemente 20 weisen jeweils einen Kopfabschnitt 21 auf, der in seinem senkrecht zur Fluchtlinie einer Gruppe liegenden Querschnitt und in Richtung der entsprechenden Stirnfläche 22 durch Keilflächen 23 verbreitert ist.The active part consists of a plurality of rod-shaped active elements, which are generally designated 20. These are arranged with their longitudinal axes vertically aligned in the cell in the assembly position parallel to one another and in groups 11, 12, 13 etc. aligned with one another along the alignment line 25 (FIG. 3). They are essentially square or rectangular in their cross section perpendicular to their longitudinal axis. They consist of an electrically conductive and electrochemically active oxide ceramic material that can be described in more detail. The active elements 20 each have a head section 21, which is widened by wedge surfaces 23 in its cross section lying perpendicular to the alignment line of a group and in the direction of the corresponding end face 22.

Der im wesentlichen plattenförmig ausgebildete Elektrodenhalter 30 besitzt eine - in der Montagestellung in der Elektrolysezelle gesehen - nach unten gerichtete Hauptfläche 31, an der die Aktivelemente 20 mit ihren Stirnflächen 22 mechanisch und elektrisch in Kontakt gehalten sind. Dies erfolgt mit Hilfe von die Verbindungsanordnung 40 darstellenden Spannelementen 41. Diese Spannelemente sind in ihrem parallel zur Längsachse der Aktivelemente 20 und senkrecht zur Fluchtlinie einer Gruppe verlaufenden Querschnitt so trapezförmig ausgebildet, daß die zwei gegenüberliegenden Keilflächen 42 mit den gleichwinklig liegenden Keilflächen 23 zweier in zwei benachbarten Gruppen, z.B. 12, 13, gegenüberliegenden Aktivelementen 20 mit entsprechender Vorspannung in Anlage stehen. Hierzu sind die Spannelemente 41 mittels Schrauben mit dem plattenförmigen Elektrodenhalter 30 verschraubt.The essentially plate-shaped electrode holder 30 has a main surface 31, as seen in the electrolysis cell in the assembly position, on which the active elements 20 are mechanically and electrically kept in contact with their end surfaces 22. This is done with the aid of the connecting arrangement 40 representing tensioning elements 41.These tensioning elements are so trapezoidal in their cross section parallel to the longitudinal axis of the active elements 20 and perpendicular to the alignment line of a group that the two opposite wedge surfaces 42 with the wedge surfaces 23 lying at the same angle are two in two neighboring groups, e.g. 12, 13, opposite active elements 20 with appropriate bias are in contact. For this purpose, the clamping elements 41 are screwed to the plate-shaped electrode holder 30 by means of screws.

Durch die Spannelemente 41 sind zwei benachbarte Gruppen 11, 12, 13 usw. von Aktivelementen so beabstandet, daß Kanäle 50 ausgebildet sind, die in beschriebener Weise eine Zirkulation des Elektrolyts bzw. der Schmelze zwischen den unteren, in die Schmelze bzw. in den Elektrolyt eintauchenden Abschnitten 26 der Aktivelemente 20 ermöglicht wird und die andererseits eine rasche Abfuhr des bei dem Elektrolyseprozeß entwickelten Gases zwischen den Gruppen angeordenten Aktivelementen 20 nach oben hin gewährleisten.By the clamping elements 41, two adjacent groups 11, 12, 13, etc. of active elements are spaced apart such that channels 50 are formed which, in the manner described, circulate the electrolyte or the melt between the lower ones, into the melt or into the electrolyte immersed sections 26 of the active elements 20 is made possible and, on the other hand, ensure rapid removal of the gas developed in the electrolysis process between the groups of active elements 20 arranged upwards.

Der plattenförmige Elektrodenhalter 30 ist als Hohlkörper ausgebildet, bestehend aus einer unteren horizontalen Platte 32, einer oberen, zur ersten parallel angeordneten Platte 33 und dazu senkrechten Seitenwänden 34. Der Hohlraum dient zur Zirkulation von Kühlwasser im Innenraum 35 des Elektrodenhalters 30. Hierzu ist ein Kühlwasser-Zulaufrohr 36 vorgesehen, das randseitig in den Innenraum 35 mündet. Entlang spiralförmig verlaufenden Leitwänden 37 zirkuliert das Kühlwasser durch den Innenraum 35 des plattenförmigen Elektrodenhalters 30 bis zu dessen Zentrumsbereich und von dort wieder in den peripheren Bereich, von wo das entsprechend erwärmte Kühlwasser durch ein Kühlwasserableitrohr 38 abgezogen wird.The plate-shaped electrode holder 30 is designed as a hollow body, consisting of a lower horizontal plate 32, an upper plate 33 arranged parallel to the first and side walls 34 perpendicular thereto. The cavity serves for the circulation of cooling water in the interior 35 of the electrode holder 30. This is a cooling water Inlet pipe 36 is provided which opens into the interior 35 on the edge. The cooling water circulates along spiral-shaped guide walls 37 through the interior 35 of the plate-shaped electrode holder 30 up to its central area and from there again into the peripheral area, from where the correspondingly heated cooling water is drawn off through a cooling water drain pipe 38.

Der plattenförmige Elektrodenhalter 30 ist des weiteren mit mehreren Stromzuführungs-Bolzen 60 ausgerüstet, über die der elektrische Strom dem plattenförmigen Elektrodenhalter 30 zugeleitet und von dort auf die Elektrodenelemente 20 übertragen wird. Zur Verbindung der Stromzuführungsbolzen 60 mit der unteren Platte 33 des Elektrodenhalters 30 sind an der Innenfläche der unteren Platte 33 jeweils Muffen 61 verschweißt, die ein Innengewinde besitzen, mit dem der untere und mit einem Außengewinde versehene Abschnitt des entsprechenden Stromzuführungsbolzens 60 verschraubt ist. Um den Stromzuführungsbolzen 60 im Bereich des Innenraums der Zelle vor Korrosion zu schützen, ist dieser mit Schutzhülsen 62 aus korrosionsbeständigem Material umgeben.The plate-shaped electrode holder 30 is further equipped with a plurality of current supply bolts 60, via which the electrical current is fed to the plate-shaped electrode holder 30 and is transmitted from there to the electrode elements 20. To connect the power supply bolts 60 to the lower plate 33 of the electrode holder 30, sleeves 61 are welded to the inner surface of the lower plate 33, which have an internal thread with which the lower and externally threaded section of the corresponding power supply bolt 60 is screwed. In order to protect the power supply pin 60 from corrosion in the area of the interior of the cell, it is surrounded by protective sleeves 62 made of corrosion-resistant material.

Um den elektrischen Kontakt zwischen den Stirnflächen 22 der Aktivelemente 20 und der Fläche 31 des plattenförmigen Elektrodenhalters noch weiter zu verbessern, ist zwischen diesen Flächen ein Netz 39, z.B. aus Kupfer, eingebracht.In order to further improve the electrical contact between the end faces 22 of the active elements 20 and the face 31 of the plate-shaped electrode holder, a network 39, e.g. made of copper.

Der plattenförmige Elektrodenhalter 30 und die Spannelemente 41 sowie deren Spannschrauben 43 bestehen zweckmäßigerweise aus Stahl. Sie können auch aus Nickel oder aus Stahl- bzw. Nickellegierungen bestehen.The plate-shaped electrode holder 30 and the clamping elements 41 and their clamping screws 43 are expediently made of steel. They can also consist of nickel or of steel or nickel alloys.

Zum Schutz dieser Bauteile gegen Korrosion sind Abdeckelemente vorgesehen. Die an der Unterseite der Spannelemente angeordneten Abdeckelemente 44 sind z.B. mittels einer Schwalbenschwanzführung an den Spannelementen 41 gesichert. Die seitlichen Abdeckelemente 45 können mit den stirnseitigen Enden der Spannelemente 41 durch Schrauben 46 verschraubt sein.Cover elements are provided to protect these components against corrosion. The cover elements 44 arranged on the underside of the tensioning elements are e.g. secured to the tensioning elements 41 by means of a dovetail guide. The side cover elements 45 can be screwed to the front ends of the clamping elements 41 by screws 46.

Die Aktivelemente 20 bestehen zweckmäßigerweise aus dotierter Oxid-Keramik, z.B. Zinnoxid, Nickelferrit oder Yttriumoxid.The active elements 20 expediently consist of doped oxide ceramic, e.g. Tin oxide, nickel ferrite or yttrium oxide.

Beispielsweise kann die Zusammensetzung wie folgt sein:

  • 94,1 Atom-% Zinnoxid
  • 3,8 Atom-% Kupfer
  • 2,1 Atom-% Antimon
For example, the composition can be as follows:
  • 94.1 atomic percent tin oxide
  • 3.8 atomic% copper
  • 2.1 atomic% antimony

Bei einem speziellen Ausführungsbeispiel der erfindungsgemäßen Anode hat sich folgende Dimensionierung der stabförmigen Aktivelemente als zweckentsprechend erwiesen:

  • Querschnitt der oberen Stirnfläche: 3 x 3 cm
  • Querschnitt der unteren Stirnfläche: 2 x 2 cm
  • Länge: 25 cm
  • Keilwinkel: 20°
In a special embodiment of the anode according to the invention, the following dimensioning of the rod-shaped active elements has proven to be appropriate:
  • Cross section of the upper face: 3 x 3 cm
  • Cross section of the lower face: 2 x 2 cm
  • Length: 25 cm
  • Wedge angle: 20 °

Abstand zwischen zwei benachbarten Gruppen von Elektrodenelementen: 1,5 cmDistance between two adjacent groups of electrode elements: 1.5 cm

Die Seitenlänge des oberen Querschnitts kann zweckmä ßigerweise zwischen ca. 2 und 6 cm liegen. Die Länge der Aktivelemente kann zwischen ca. 15 cm und ca. 40 cm liegen. Der erwähnte Abstand zwischen zwei Gruppen von Aktivelementen kann zwischen ca. 1 cm und ca. 2 cm liegen. Der Keilwinkel des Kopfabschnittes der jeweiligen Aktivelemente kann zwischen ca. 5° und ca. 25° betragen.The side length of the upper cross section can expediently be between approximately 2 and 6 cm. The length of the active elements can be between approx. 15 cm and approx. 40 cm. The mentioned distance between Two groups of active elements can be between approx. 1 cm and approx. 2 cm. The wedge angle of the head section of the respective active elements can be between approximately 5 ° and approximately 25 ° .

Das beschriebene Ausfühungsbeispiel der erfindungsgemäßen Anode wurde in einer Elektrolysetestzelle mit folgenden Betriebsdaten betrieben:

  • Badzusammensetzung: Kryolith 84 Gew.-%
  • Al F3 5 Gew.-%
  • A1203 10 Gew.-%
  • CaF2 1 Gew.-%
  • Temperatur: 980-1000 C
  • Klemmspannung: 4-5 Volt
  • Stromstärke: 30 A
  • Stromdichte an der Anode: 2 A/cm2
  • Stromdichte an der Kathode:0,14 A/cm2
  • Elektrodenabstand: 3 cm
  • Tauchtiefe der Anoden: 2cm
The described exemplary embodiment of the anode according to the invention was operated in an electrolysis test cell with the following operating data:
  • Bath composition: cryolite 84% by weight
  • Al F3 5% by weight
  • A1203 10% by weight
  • CaF2 1% by weight
  • Temperature: 980-1000 C.
  • Clamp voltage: 4-5 volts
  • Current: 30 A.
  • Current density at the anode: 2 A / cm2
  • Current density at the cathode: 0.14 A / cm2
  • Electrode distance: 3 cm
  • Immersion depth of the anodes: 2cm

Claims (16)

1. Inert composite electrode, in particular an anode for fusion electrolysis, consisting of
- an active portion in the form of a plurality of rod-shaped active elements, in particular made of oxide ceramics, which are arranged with their longitudinal axes parallel and adjacent to each other and in groups aligned with each other,
- an electrode support which includes an electrically conductive plate with one main surface of which the active elements are in contact with their end faces in force-locking relationship, and
- a connecting assembly which joins the active elements together in groups and holds them in contact with the plate, characterised in that
- the active elements (20) each comprise on the plate side a head section (21) which, in its cross-section perpendicular to the alignment (25) of a group (e.g. 11, 12, etc.) and in the direction of the end face (22) on the plate side, widens essentially in a wedge shape (23), and
- with each of the two opposed wedge surfaces (23) of the head section (21) of the respective active element (20) is brought into abutment a clamping element (41) with a wedge surface (42), the wedge angle of which essentially corresponds to that of the respective wedge surface of the head section.
2. Composite electrode according to claim 1, characterised in that the active elements (20) of a group (e.g. 11) are in abutment with each other in their alignment (25).
3. Composite electrode according to claim 1 or 2, characterised in that the electrical conductivity of the material of the active elements (20) is higher in the region of the head section (21) than in the remaining region.
4. Composite electrode according to claim 3, characterised in that the material of the active elements (20) in the region of the head section (21) is a cermet, which preferably contains silver.
5. Composite electrode according to any of the preceding claims, characterised in that a contact layer (39) is introduced between the respective main surface (31) of the plate (30) and the corresponding end faces (22) of the active elements (20).
6. Composite electrode according to claim 5, characterised in that the contact layer consists of a network (39) of highly conductive metal, in particular copper.
7. Composite electrode according to any of the preceding claims, characterised in that the clamping element (41) is designed to fix two opposed active elements (20) of two adjacent groups (e.g. 11, 12) and for this comprises two opposed wedge surfaces (42) with an essentially symmetrical arrangement.
8. Composite electrode according to claim 7, characterised in that the clamping element (41) has a trapezoidal cross-section perpendicularly to the alignment of the groups of active elements.
9. Composite electrode according to any of the preceding claims, characterised in that two separate clamping elements (41) are associated with each active element (20), and the length of a clamping element (41) essentially corresponds to the length of an active element (20).
10. Composite electrode according to any of the preceding claims 1 to 8, characterised in that two continuous clamping elements (41) are provided for each group (e.g. 11) of active elements (20), and the length of a clamping element (41) essentially corresponds to the length of a group (e.g. 11) of active elements (20).
11. Composite electrode according to any of the preceding claims, characterised in that the clamping elements (41) are attached to the plate (30) by bolts (43).
12. Composite electrode according to any of the preceding claims, characterised in that the clamping elements (41), preferably including their fixing means (43), are protected against the interior of the cell by covering elements (44, 45) made of corrosion-resistant material.
13. Composite electrode according to any of the preceding claims, characterised in that the plate (30) is cooled.
14. Composite electrode according to claim 13, characterised in that water cooling is provided.
15. Composite electrode according to claim 14, characterised in that the plate (30) is designed as a hollow body inside which are disposed channels for the cooling water.
16. Composite electrode according to any of the preceding claims 13 to 15, characterised in that at least one current supply (60) to the plate is provided, which extends through the interior of the hollow body and is electrically connected to the inside of the main surface (31) with which the electrode elements (20) are in contact.
EP86113930A 1985-10-22 1986-10-08 Inert composite electrode, particularly an anode for molten salt electrolysis Expired EP0220557B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86113930T ATE43366T1 (en) 1985-10-22 1986-10-08 INERT COMPOUND ELECTRODE, IN PARTICULAR ANODE FOR MOLTEN ELECTROLYSIS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19853537575 DE3537575A1 (en) 1985-10-22 1985-10-22 INERT COMPOSITE ELECTRODE, ESPECIALLY ANODE FOR MELTFLOW ELECTROLYSIS
DE3537575 1985-10-22

Publications (2)

Publication Number Publication Date
EP0220557A1 EP0220557A1 (en) 1987-05-06
EP0220557B1 true EP0220557B1 (en) 1989-05-24

Family

ID=6284182

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86113930A Expired EP0220557B1 (en) 1985-10-22 1986-10-08 Inert composite electrode, particularly an anode for molten salt electrolysis

Country Status (10)

Country Link
US (1) US4840718A (en)
EP (1) EP0220557B1 (en)
AT (1) ATE43366T1 (en)
BR (1) BR8604998A (en)
CA (1) CA1299138C (en)
DE (2) DE3537575A1 (en)
ES (1) ES2003380A6 (en)
HU (1) HU203133B (en)
NO (1) NO168314C (en)
ZA (1) ZA867953B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2860247B1 (en) 2003-09-30 2005-11-11 Pechiney Aluminium DEVICE AND METHOD FOR CONNECTING INDEED ANODES FOR THE PRODUCTION OF ALUMINUM BY IGNEE ELECTROLYSIS
WO2018092103A1 (en) * 2016-11-19 2018-05-24 Jan Petrus Human Electrodes for use in the electro-extraction of metals

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH340346A (en) * 1956-01-23 1959-08-15 Aluminium Ind Ag Electrode for cathodic power supply in aluminum refining cells that work according to the three-layer process
US3607713A (en) * 1969-05-07 1971-09-21 Quaker Oats Co Anode for production of aluminum metal
US3761385A (en) * 1971-06-30 1973-09-25 Hooker Chemical Corp Electrode structure
US3984304A (en) * 1974-11-11 1976-10-05 Ppg Industries, Inc. Electrode unit
EP0022921B1 (en) * 1979-07-20 1983-10-26 C. CONRADTY NÜRNBERG GmbH & Co. KG Regenerable, shape-stable electrode for use at high temperatures
CH642402A5 (en) * 1979-12-18 1984-04-13 Alusuisse ANODE OF DIMENSIONAL STABLE OXIDE CERAMIC INDIVIDUAL ELEMENTS.
US4357226A (en) * 1979-12-18 1982-11-02 Swiss Aluminium Ltd. Anode of dimensionally stable oxide-ceramic individual elements
EP0050681B1 (en) * 1980-10-27 1985-09-11 C. CONRADTY NÜRNBERG GmbH & Co. KG Electrode for igneous electrolysis
US4462088A (en) * 1981-11-03 1984-07-24 International Business Machines Corporation Array design using a four state cell for double density

Also Published As

Publication number Publication date
HU203133B (en) 1991-05-28
NO168314B (en) 1991-10-28
ZA867953B (en) 1987-06-24
BR8604998A (en) 1987-07-14
EP0220557A1 (en) 1987-05-06
NO864210L (en) 1987-04-23
DE3537575A1 (en) 1987-04-23
ATE43366T1 (en) 1989-06-15
CA1299138C (en) 1992-04-21
US4840718A (en) 1989-06-20
NO864210D0 (en) 1986-10-21
DE3537575C2 (en) 1988-09-15
HUT44087A (en) 1988-01-28
DE3663537D1 (en) 1989-06-29
ES2003380A6 (en) 1988-11-01
NO168314C (en) 1992-02-05

Similar Documents

Publication Publication Date Title
DE2838965C2 (en) Wettable cathode for a molten electrolysis furnace
CH629056A5 (en) ELECTRODE FOR ARC FURNACE.
DE2448187A1 (en) ELECTROLYSIS CELL
EP0220557B1 (en) Inert composite electrode, particularly an anode for molten salt electrolysis
DE10022592B4 (en) Bipolar multipurpose electrolysis cell for high current loads
DE1202988B (en) Aluminum electrolytic furnace
DE102004008813B3 (en) Process and installation for the electrochemical deposition of copper
DD144174A1 (en) ELECTROLYSIS CELL AND METHOD FOR THE MANUFACTURE THEREOF
EP2619353A1 (en) Cathode for electrolysis cells
DE3406777C2 (en) Coated valve metal anode for the electrolytic extraction of metals or metal oxides
DE2823589A1 (en) ELECTRICAL CONNECTOR FOR ELECTROLYSIS CELLS
DE898817C (en) Furnace for direct fused aluminum electrolysis
WO2014174108A1 (en) Cathode block having a slot with a varying depth and a filled intermediate space
DE10003012A1 (en) Cathode arrangement
DE2833381A1 (en) Electrolysis cell for winning aluminium - where carbon cathode hearth is connected to bus=bars via spaced graphite pegs increasing the efficiency of aluminium prodn.
DE10164013C1 (en) Longitudinal graphitization of cathode blocks for electrolytic production of aluminum comprises arranging blocks with gap between their ends, conductive moldings being placed between blocks
DE2809146A1 (en) MAGNETIC FIELD LINE ABSORPTION IN ELECTROLYSIS CELLS
DE2721958A1 (en) Metal electrode for electrolytic mfr. of chlorine - has metal bars with high conductivity embedded in tubes with low conductivity
EP1901586A1 (en) Electrode supporting arm
DE19940698C2 (en) Electrolysis plant for metal extraction
DD283845A5 (en) ELECTROLYTIC CELL OF DIAPHRAGMATYP
DE2114231A1 (en) Composite wall for MHD devices
CH670658A5 (en) Cathode bars for aluminium prodn. cell - have cross=section reductions near active part of carbon hearth
DE1421367C (en) Electrolytic cell
DE2821687A1 (en) POWER TUBE WITH MAGNETIC BEAM GUIDANCE

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT CH DE FR GB IT LI NL

17P Request for examination filed

Effective date: 19870622

17Q First examination report despatched

Effective date: 19880919

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT CH DE FR GB IT LI NL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT

Effective date: 19890524

REF Corresponds to:

Ref document number: 43366

Country of ref document: AT

Date of ref document: 19890615

Kind code of ref document: T

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)
REF Corresponds to:

Ref document number: 3663537

Country of ref document: DE

Date of ref document: 19890629

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19911008

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19911009

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19911010

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19911022

Year of fee payment: 6

ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19911031

Year of fee payment: 6

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19921008

Ref country code: AT

Effective date: 19921008

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: CH

Effective date: 19921031

Ref country code: LI

Effective date: 19921031

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19930408

Year of fee payment: 7

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19930501

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19921008

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930630

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19940701