EP0041045A1 - Cathode for molten-salt electrolysis cell - Google Patents

Cathode for molten-salt electrolysis cell Download PDF

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Publication number
EP0041045A1
EP0041045A1 EP81810185A EP81810185A EP0041045A1 EP 0041045 A1 EP0041045 A1 EP 0041045A1 EP 81810185 A EP81810185 A EP 81810185A EP 81810185 A EP81810185 A EP 81810185A EP 0041045 A1 EP0041045 A1 EP 0041045A1
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EP
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Prior art keywords
aluminum
cathode
elements
cathode according
plates
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EP81810185A
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German (de)
French (fr)
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EP0041045B1 (en
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Tibor Kugler
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Alcan Holdings Switzerland AG
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Alusuisse Holdings AG
Schweizerische Aluminium AG
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    • 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

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  • the invention relates to a cathode made of individually replaceable elements for a melt flow electrolysis cell, in particular for the production of aluminum.
  • cathodes made of titanium diboride, titanium carbide, pyrolytic graphite, boron carbide and other substances are proposed for electrolytic cells belonging to the prior art, mixtures of these substances which can be sintered together also being used.
  • cathodes that are wettable with aluminum and not or only slightly soluble in aluminum offer decisive advantages.
  • the cathodically deposited aluminum already flows when a very thin layer is formed on the cathode surface facing the active anode surface. It is therefore possible to remove the deposited liquid aluminum from the gap between the anode and cathode and to feed it to a sump located outside the gap.
  • the irregularities with respect to the thickness of the aluminum layer which are well known from conventional electrolysis, do not form - under the influence of electromagnetic and convectional forces. Therefore, the interpolar distance can be reduced without loss of current efficiency, i.e. a significantly lower energy consumption per unit of reduced metal is achieved.
  • the sump In order not to let the scooping intervals become uneconomically small, the sump must therefore be deep, which in turn requires increased insulation of the cell floor. It should also be noted that the connection between the carbon base and the wettable cathode plates places difficult demands on the connection mass and increases the electrical resistance of the cell base. As with conventional electrolysis cells, the cell bottom is made of electrically conductive, ie weakly heat-insulating carbon material.
  • Wettable cathodes are also used according to the process of DE-OS 26 56 579.
  • the circulation of the cryolite melt is improved in that the cathode elements are anchored in the electrically conductive cell bottom and protrude in the area below the anodes from the aluminum sump collected on the entire remaining cell bottom surface.
  • the cathode elements consist of tubes, closed at the bottom, made of aluminum-wettable material, the tubes being completely filled with aluminum.
  • gaps between the cathode elements facilitate the circulation of the electrolyte.
  • the height of these gaps or tubes is chosen so that there is no significant current transfer between the anode and the aluminum sump.
  • the power supply lines to the cathode elements shown in the examples of the above-mentioned DE-OS all have the disadvantages of power supply through the carbon base.
  • the flow of the electrolyte is a vortex flow around the cathode element and takes place without a preferred direction, so the distribution of the alumina concentration is not optimal.
  • a major disadvantage of all of these previously discussed embodiments with wettable cathodes is that they are firmly anchored in the carbon bottom of the cell.
  • a material must therefore be selected for the wettable cathodes whose lifespan is at least the same or better than the operating life of the cell lining.
  • the use of a cheaper material with a shorter operating time or the use of simpler manufacturing technology would have the consequence that failure of only a small part of the cathode elements, for example due to operating or manufacturing errors, would result in the failure of the entire electrolytic cell.
  • the carbon floor with the cast-in cathode bars is in itself extremely sensitive to manufacturing defects.
  • the inventor has set himself the task of creating a cathode from individually interchangeable elements for a melt flow electrolysis cell for the production of aluminum, which can be produced more economically, in particular with regard to shaping and processing.
  • the upper parts of the elements consist of materials described in the relevant literature for wettable cathode plates which meet the requirements. Examples include titanium diboride, titanium carbide, titanium nitride, zirconium diboride, zirconium carbide, zirconium nitride, and mixtures of two or more materials, which may optionally contain a small amount of boron nitride blended.
  • the electrically conductive, preferably plate-shaped upper parts of the elements protrude into the liquid aluminum, but they do not touch the carbon bottom of the cell.
  • the lower parts of the elements or their coating need not be wettable by aluminum or have electrical conductivity. They only have to be compatible with molten aluminum, have sufficient mechanical strength and high thermal shock resistance. Materials that meet these conditions sufficiently are much cheaper than the aluminum-wettable and electrically conductive materials used for the upper parts or their coating.
  • molded parts made of insulator material used for the lower part of the elements are much easier to produce, which - together with the lower production costs for the materials - is expressed in the fact that mass production of lower parts is 10 to 20 times cheaper than that of upper parts.
  • insulator materials which never come into contact with the molten electrolyte include highly sintered aluminum oxide, aluminum oxide-containing ceramics, silicon carbide or silicon nitride-bonded silicon carbide. These materials have a higher specific weight than aluminum and are erosion-resistant, which is important because of the sludge present in the circulating aluminum.
  • Both the lower and the upper part of a cathode element can - instead of being designed as a homogeneous solid body - a core made of a less expensive, mechanically stable material, such as e.g. Steel, titanium or graphite, which is coated with at least one of the corresponding materials by a known method. If graphite is used as the core material, the composite body can be produced using a sintering process.
  • the cathode elements preferably consist of several sub-elements.
  • the electrically conductive sub-elements forming the upper part are expediently of the simplest possible geometric shape, e.g. 1 - 2 cm thick, vertically arranged plates, the distance between the plates being greater than their thickness.
  • the easily formable and editable sub-elements made of insulating material forming the lower part form a support or a support structure for the upper sub-elements.
  • the horizontal surface dimensions of the cathode elements are expediently designed such that an integer multiple, between 1 and 7, corresponds to the horizontal surface dimensions of the anode located above.
  • the horizontal geometric dimensions of a cathode element and the corresponding anode of the same order of magnitude are preferred.
  • the type of power supply from the power source to the cathode surface is of crucial importance for the furnace operation: the electrolyte located between the anode and the cathode element is exposed to a magnetohydrodynamic pumping action under the influence of the electrolysis current and the magnetic field.
  • FIGS. 1-3 A cathode element 10 with an upper part made of the electrically conductive aluminum-wettable plates 12 and a lower part made of aluminum-compatible shaped plates 14, 16 is shown in FIGS. 1-3.
  • the wettable cathode plates 12 by means of a round bolt 18 with the same dimensions insulator plates 14 mechanically n ic stably connected.
  • the bolts 18 are preferably made of the more easily machinable and cheaper insulator material; they do not come into contact with the molten electrolyte.
  • the support plates 14 made of insulator material have recesses 20 on their underside, which in turn fit in a form-fitting manner in recesses 22 of the support plates 16 likewise made of insulator material.
  • intermediate pieces e.g. B. in the form of wedges and / or cements resistant to liquid aluminum.
  • the elements can customize c based thermal expansions also subsequently obtain reasonable.
  • the electrically conductive cathode plates 12 have the interpolar distance d from the burning carbon anode 28. During the electrolysis process, the electrolyte is quickly used up in a narrow gap between the cathode plates and the anode.
  • the cathode plates 12 are relatively narrow; therefore the bath flow can rapidly renew the electrolyte depleted of aluminum oxide in the interpolar gap, even if the value is greatly reduced compared to the normal value of 6 - 6.5 cm for d.
  • the deposited metal forms an uninterrupted film on the wettable cathode plates 12 and flows down to the metal sump 26.
  • the surface 32 of the liquid aluminum 26 must always lie in the area of the wettable cathode plates 12, in particular when scooping, this metal level must never sink into the area of the insulator plates 14, 16. This would mean both a power cut and corrosive destruction of the insulator plates.
  • the direct electrolysis current flows from the anodes 28 via the electrolytes 30 in the interpolar gap to the cathode plates 12, then passes into the liquid aluminum 26 and finally flows via the carbon bottom 34 into the iron cathode bars 36.
  • wettable cathodes could also be formed which, for example, have tubes known from the prior art.
  • corresponding recesses would form in the working surface of the anodes, which would result in the formation of gas bags which reduce the current efficiency during the electrolysis process.
  • Guide grooves 35 can be formed in the carbon base 34 of the electrolytic cell, which prevent the cathode elements 10 from slipping sideways.
  • the plate 12 has a dovetail 40 which can be inserted into a corresponding recess in the carrier plate 14.
  • the support structure made of insulator material is then designed so that the plates cannot be moved laterally.
  • FIG. 5 Another variant of wettable cathode plates 12 is shown in FIG. 5. Both the formation of a window 38 and the bevelled underside are intended on the one hand to save wettable cathode material and on the other hand to optimize the flow conditions in the bath.
  • the cathode plate 12 is fastened in a support plate 14 by means of an extension 42 directed downwards in the center.
  • a support structure 14, 16 per se is not the subject of the invention; any suitable variant used in other fields of technology can be used for this purpose.
  • the cathode elements 10 according to the invention can also be used for converting existing electrolysis cells by simply placing units adapted to the anode dimensions and the metal level on the carbon floor. As a result, the interpolar distance can be reduced at low additional costs, and the current yield can thereby be increased. In particular, it should be noted that the retrofitting can be carried out without decommissioning the electrolytic cell and that subsequent replacement of defective cathode elements does not pose any problems.

Abstract

A solid cathode in a fused salt electrolytic cell for the production of aluminum is made up of individually exchangeable elements (10). These cathode elements are made up of two parts which are rigidly joined together and which are resistant to thermal shock. The upper part (12) which projects from the molten electrolyte (30) into the precipitated aluminum (26), or the coating on this part (12), is made of a material which, at working temperature, is a good electrical conductor, is chemically resistant and is wet by aluminum. The lower part (14,16), which is exclusively in the liquid aluminum (26), or the coating on this part (14,16) is on the other hand made of an insulating material which can withstand molten aluminum.

Description

Die Erfindung bezieht sich auf eine Kathode aus einzeln auswechselbaren Elementen für eine Schmelzflusselektrolysezelle, insbesondere zur Herstellung von Aluminium.The invention relates to a cathode made of individually replaceable elements for a melt flow electrolysis cell, in particular for the production of aluminum.

Für die Gewinnung von Aluminium durch Elektrolyse von Aluminiumoxid wird dieses in einer Fluoridschmelze gelöst, die zum grössten Teil aus Kryolith besteht. Das kathodisch abgeschiedene Aluminium sammelt sich unter der Fluoridschmelze auf dem Kohleboden der Zelle, wobei die Oberfläche des flüssigen Aluminiums die Kathode bildet. An Anodenbalken befestigte, bei konventionellen Verfahren aus amorphem Kohlenstoff bestehende Anoden tauchen von oben in die Schmelze ein. An den Kohleanoden entsteht durch die elektrolytische Zersetzung des Aluminiumoxids Sauerstoff der sich mit dem Kohlenstoff der Anoden zu C02 und CO verbindet. Die Elektrolyse findet im allgemeinen in einem Temperaturbereich von etwa 940-970 C statt. Im Laufe der Elektrolyse verarmt der Elektrolyt an Aluminiumoxid. Bei einer unteren Konzentration von ca. 1 - 2 Gew.-% Aluminiumoxid im Elektrolyten kommt es zum Anodeneffekt, der sich in einer Spannungserhöhung von beispielsweise 4 - 4,5 V auf 30 V und darüber auswirkt. Spätestens dann muss die aus erstarrtem Elektrolytmaterial gebildete Kruste eingeschlagen, und die Aluminiumoxidkonzentration durch Zugabe von neuem Aluminiumoxid (Tonerde) angehoben werden.For the production of aluminum by electrolysis of aluminum oxide, this is dissolved in a fluoride melt, which largely consists of cryolite. The cathodically deposited aluminum collects under the fluoride melt on the carbon bottom of the cell, the surface of the liquid aluminum forming the cathode. Anodes attached to anode bars and made of amorphous carbon in conventional processes are immersed in the melt from above. At the carbon anodes, the electrolytic decomposition of the aluminum oxide produces oxygen which combines with the carbon of the anodes to form CO 2 and CO. The electrolysis generally takes place in a temperature range of approximately 940-970 ° C. In the course of electrolysis, the electrolyte becomes poor in aluminum oxide. At a lower concentration of approx. 1 - 2% by weight aluminum oxide in the electrolyte, there is an anode effect, which results in a voltage increase from 4 - 4.5 V to 30 V and above, for example. Then, at the latest, the crust formed from solidified electrolyte material must be hammered in and the aluminum oxide concentration increased by adding new aluminum oxide (alumina).

Es ist bekannt, bei der Schmelzflusselektrolyse zur Herstellung von Aluminium benetzbare Kathoden einzusetzen. Bei der Abscheidung von Aluminium werden für zum Stand der Technik gehörende Elektrolysezellen Kathoden aus Titandiborid, Titankarbid, pyrolytischem Graphit, Borkarbid und weiteren Substanzen vorgeschlagen, wobei auch Gemische dieser Substanzen, die zusammengesintert sein können, eingesetzt werden. Gegenüber konventionellen Elektrolysezellen mit einer Interpolardistanz von ca. 6 - 6,5 cm bieten mit Aluminium benetzbare und in Aluminium nicht oder nur wenig lösliche Kathoden entscheidende Vorteile. Das kathodisch abgeschiedene Aluminium fliesst schon bei Ausbildung einer sehr dünnen Schicht auf der der aktiven Anodenfläche zugewandten Kathodenoberfläche. Es ist deshalb möglich, das abgeschiedene flüssige Aluminium aus dem Spalt zwischen Anode und Kathode abzuleiten und einem ausserhalb des Spaltes angeordneten Sumpf zuzuführen.It is known to use wettable cathodes in the melt flow electrolysis for the production of aluminum. In the deposition of aluminum, cathodes made of titanium diboride, titanium carbide, pyrolytic graphite, boron carbide and other substances are proposed for electrolytic cells belonging to the prior art, mixtures of these substances which can be sintered together also being used. Compared to conventional electrolysis cells with an interpolar distance of approx. 6 - 6.5 cm, cathodes that are wettable with aluminum and not or only slightly soluble in aluminum offer decisive advantages. The cathodically deposited aluminum already flows when a very thin layer is formed on the cathode surface facing the active anode surface. It is therefore possible to remove the deposited liquid aluminum from the gap between the anode and cathode and to feed it to a sump located outside the gap.

Dank der dünnen Aluminiumschicht der Kathodenoberfläche bilden sich die aus der konventionellen Elektrolyse sattsam bekannten Ungleichmässigkeiten in bezug auf die Dicke der Aluminiumschicht - unter dem Einfluss elektromagnetischer und konvektioneller Kräfte - nicht. Deshalb kann die Interpolardistanz ohne Einbusse an Stromausbeute reduziert werden, d.h. es wird ein wesentlich kleinerer Energieverbrauch pro Einheit reduziertes Metall erreicht.Thanks to the thin aluminum layer on the cathode surface, the irregularities with respect to the thickness of the aluminum layer, which are well known from conventional electrolysis, do not form - under the influence of electromagnetic and convectional forces. Therefore, the interpolar distance can be reduced without loss of current efficiency, i.e. a significantly lower energy consumption per unit of reduced metal is achieved.

In der US-PS 3 400 061 wird eine Elektrolysezelle vorgeschlagen, bei welcher am Zellenboden aus Kohlenstoff benetzbare Kathoden befestigt sind. Die Kathodenplatten sind in bezug auf die Horizontale, gegen die Zellenmitte, leicht geneigt. Die lichte Weite des Spaltes zwischen Anode und Kathode, d.h. die Interpolardistanz, ist wesentlich kleiner als bei konventionellen Zellen. Dadurch wird jedoch die Zirkulation des Elektrolyten zwischen Anode und Kathode erschwert. Bei der Abscheidung von Aluminium verarmt die Kryolithschmelze stark an Tonerde, wodurch die Zelle anfällig für Anodeneffekte wird. Für das Sammeln des flüssigen Metalls steht nur ein kleiner Teil der gesamten Bodenfläche der Zelle zur Verfügung. Um die Schöpfintervalle nicht unwirtschaftlich klein werden zu lassen, muss deshalb der Sumpf tief ausgebildet sein, was wiederum eine verstärkte Isolation des Zellenbodens bedingt. Ausserdem ist zu beachten, dass die Verbindung zwischen dem Kohlenstoffboden und den benetzbaren Kathodenplatten schwer erreichbare Forderungen an die Verbindungsmasse stellt und den elektrischen Widerstand des Zellenbodens vergrössert. Wie bei üblichen Elektrolysezellen besteht der Zellenboden aus elektrisch leitendem, also schwach wärmeisolierendem Kohlematerial.An electrolysis cell is proposed in US Pat. No. 3,400,061, in which cathodes which are wettable from carbon are attached to the cell bottom. The cathode plates are slightly inclined with respect to the horizontal, towards the center of the cell. The clear width of the gap between the anode and cathode, ie the interpolar distance, is considerably smaller than with conventional cells. However, this makes the circulation of the electrolyte between the anode and cathode difficult. When aluminum is deposited, the cryolite melt becomes very poor in alumina, making the cell susceptible to anode effects. Only a small part of the total floor area of the cell is available for collecting the liquid metal. In order not to let the scooping intervals become uneconomically small, the sump must therefore be deep, which in turn requires increased insulation of the cell floor. It should also be noted that the connection between the carbon base and the wettable cathode plates places difficult demands on the connection mass and increases the electrical resistance of the cell base. As with conventional electrolysis cells, the cell bottom is made of electrically conductive, ie weakly heat-insulating carbon material.

Auch nach dem Verfahren der DE-OS 26 56 579 werden benetzbare Kathoden eingesetzt. In dieser Vorveröffentlichung wird die Zirkulation der Kryolithschmelze dadurch verbessert, dass die Kathodenelemente im elektrisch leitenden Zellenboden verankert sind und im Bereich unterhalb der Anoden aus dem auf der gesamten übrigbleibenden Zellenbodenfläche gesammelten Aluminiumsumpf herausragen. Die Kathodenelemente bestehen im vorliegenden Fall aus unten geschlossenen Rohren aus mit Aluminium benetzbarem Material, wobei die Rohre vollständig mit Aluminium gefüllt sind.Wettable cathodes are also used according to the process of DE-OS 26 56 579. In this prior publication, the circulation of the cryolite melt is improved in that the cathode elements are anchored in the electrically conductive cell bottom and protrude in the area below the anodes from the aluminum sump collected on the entire remaining cell bottom surface. In the present case, the cathode elements consist of tubes, closed at the bottom, made of aluminum-wettable material, the tubes being completely filled with aluminum.

Oberhalb des Aluminiumsumpfs, d.h. zwischen den Rohren, erleichtern Spalten zwischen den Kathodenelementen die Zirkulation des Elektrolyten. Die Höhe dieser Spalten bzw. der Rohre wird so gewählt, dass es zu keinem bedeutenden Stromübergang zwischen der Anode und dem Aluminiumsumpf kommt. Die in den Beispielen der oben erwähnten DE-OS dargestellten Stromzuführungen zu den Kathodenelementen sind alle mit den Nachteilen der Stromzuführung durch den Kohleboden behaftet. Die Strömung des Elektrolyten ist eine Wirbelströmung um das Kathodenelement und erfolgt ohne bevorzugte Richtung, dadurch ist die Verteilung der Tonerdekonzentration nicht optimal.Above the aluminum sump, i.e. between the tubes, gaps between the cathode elements facilitate the circulation of the electrolyte. The height of these gaps or tubes is chosen so that there is no significant current transfer between the anode and the aluminum sump. The power supply lines to the cathode elements shown in the examples of the above-mentioned DE-OS all have the disadvantages of power supply through the carbon base. The flow of the electrolyte is a vortex flow around the cathode element and takes place without a preferred direction, so the distribution of the alumina concentration is not optimal.

Eine Weiterausbildung der oben stehenden DE-OS findet sich in der US-PS 4 177 128. Die wahlweise aus elektrisch leitendem oder elektrisch nicht leitendem Material bestehenden Rohre werden mit einem genau angepassten Deckel aus elektrisch leitendem Material versehen, welcher über einen abwärts gerichteten Fortsatz mit dem flüssigen Aluminium im Rohr verbunden ist. Nach dieser Ausführungsform wird jedoch bei elektrisch leitfähigen Rohren mehr Titandiborid als nach der oben erwähnten DE-OS gebraucht, während elektrisch isolierende Rohre gegen den schmelzflüssigen Kryolith kaum genügend resistent sind. Ausserdem wird in nicht hermetisch abgedichteten Rohren Schlamm gebildet, der sich schlecht wieder auflöst und praktisch nicht entfernt werden kann.A further development of the above DE-OS can be found in US Pat. No. 4,177,128. The tubes, which are optionally made of electrically conductive or electrically non-conductive material, are provided with a precisely adapted cover made of electrically conductive material, which extends downwards via a ge directed extension is connected to the liquid aluminum in the tube. According to this embodiment, however, more titanium diboride is used in electrically conductive pipes than in the above-mentioned DE-OS, while electrically insulating pipes are hardly sufficiently resistant to the molten cryolite. In addition, sludge is formed in non-hermetically sealed pipes, which dissolves poorly and can practically not be removed.

Ein wesentlicher Nachteil aller dieser bisher diskutierten Ausführungsformen mit benetzbaren Kathoden besteht darin,dass diese im Kohleboden der Zelle fest verankert sind. Aus wirtschaftlichen Gründen muss deshalb für die benetzbaren Kathoden ein Material gewählt werden, dessen Lebensdauer mindestens gleich gross oder besser grösser ist als die Betriebsdauer der Zellenauskleidung. Das Einsetzen eines billigeren Materials mit kürzerer Betriebsdauer oder das Anwenden einer einfacheren Herstellungstechnologie hätte zur Folge, dass ein Ausfall nur eines kleinen Teiles der Kathodenelemente, beispielsweise durch Bedienungs- oder Herstellungsfehler, den Ausfall der ganzen Elektrolysezelle nach sich ziehen würde. Der Kohleboden mit den eingegossenen Kathodenbarren ist an sich ausserordentlich empfindlich gegen Herstellungsfehler.A major disadvantage of all of these previously discussed embodiments with wettable cathodes is that they are firmly anchored in the carbon bottom of the cell. For economic reasons, a material must therefore be selected for the wettable cathodes whose lifespan is at least the same or better than the operating life of the cell lining. The use of a cheaper material with a shorter operating time or the use of simpler manufacturing technology would have the consequence that failure of only a small part of the cathode elements, for example due to operating or manufacturing errors, would result in the failure of the entire electrolytic cell. The carbon floor with the cast-in cathode bars is in itself extremely sensitive to manufacturing defects.

Die Anmelderin hat deshalb in der DE-OS 28 38 965 eine benetzbare Kathode für einen Schmelzflusselektrolyseofen, insbesondere zur Herstellung von Aluminium, vorgeschlagen, welche aus einzeln auswechselbaren Elementen mit je mindestens einer Stromzuführung besteht. Mit dieser Ausführungsform von problemlos auswechselbaren Kathodenelementen sind wohl die schwerwiegendsten, der oben erwähnten Nachteile behoben, es bleiben jedoch einige Unannehmlichkeiten. Die elektrisch leitenden benetzbaren Elemente bestehen aus verhältnismässig teurem Material, welches schwer bearbeitbar ist. Bezüglich der Grösse und geometrischen Form der Elemente sind Grenzen gesetzt.The applicant has therefore proposed in DE-OS 28 38 965 a wettable cathode for a melt flow electrolysis furnace, in particular for the production of aluminum, which consists of individually interchangeable elements, each with at least one power supply. With this embodiment of easily replaceable cathode elements, the most serious, the above-mentioned disadvantages have been eliminated, but some inconveniences remain. The electrically conductive wettable elements consist of relatively expensive material that is difficult to machine. There are limits to the size and geometric shape of the elements.

Der Erfinder hat sich die Aufgabe gestellt, eine Kathode aus einzeln auswechselbaren Elementen für eine Schmelzflusselektrolysezelle zur Herstellung von Aluminium zu schaffen, welche - insbesondere in bezug auf Formgebung und Bearbeitung - wirtschaftlicher hergestellt werden können.The inventor has set himself the task of creating a cathode from individually interchangeable elements for a melt flow electrolysis cell for the production of aluminum, which can be produced more economically, in particular with regard to shaping and processing.

Die Aufgabe wird erfindungsgemäss dadurch gelöst, dass die Elemente aus zwei mechanisch starr miteinander verbundenen, gegen Wärmeschocks widerstandsfähigen Teilen - einem vom schmelzflüssigen Elektrolyten in das abgeschiedene Aluminium hineinragenden oberen und einem ausschliesslich im flüssigen Aluminium angeordneten unteren Teil - aus verschiedenen Materialien gebildet sind, wobei

  • - der obere Teil bzw. dessen Beschichtung aus einem bei Arbeitstemperatur elektrisch gut leitenden, chemisch beständigen und von Aluminium benetzbaren Material, und
  • - der untere Teil bzw. dessen Beschichtung aus einem gegen das flüssige Aluminium beständigen Isolatormaterial besteht.
The object is achieved according to the invention in that the elements are formed from different materials from two mechanically rigidly interconnected parts that are resistant to thermal shocks - an upper part protruding from the molten electrolyte into the separated aluminum and a lower part arranged exclusively in the liquid aluminum
  • - The upper part or its coating made of a material which is highly electrically conductive at work temperature, chemically resistant and wettable by aluminum, and
  • - The lower part or its coating consists of an insulator material resistant to the liquid aluminum.

Die oberen Teile der Elemente bestehen aus in der einschlägigen Literatur beschriebenen Materialien für benetzbare Kathodenplatten, welche die gestellten Anforderungen erfüllen. Als Beispiele seien Titandiborid, Titankarbid, Titannitrid, Zirkondiborid, Zirkonkarbid, Zirkonnitrid und Mischungen von zwei oder mehr Materialien genannt, welche gegebenenfallseine geringe Menge zugemischten Bornitrids enthalten können.The upper parts of the elements consist of materials described in the relevant literature for wettable cathode plates which meet the requirements. Examples include titanium diboride, titanium carbide, titanium nitride, zirconium diboride, zirconium carbide, zirconium nitride, and mixtures of two or more materials, which may optionally contain a small amount of boron nitride blended.

Die elektrisch leitfähigen, vorzugweise plattenförmig ausgebildeten oberen Teile der Elemente ragen wohl in das flüssige Aluminium hinein, sie berühren jedoch den Kohleboden der Zelle nicht.The electrically conductive, preferably plate-shaped upper parts of the elements protrude into the liquid aluminum, but they do not touch the carbon bottom of the cell.

Die unteren Teile der Elemente bzw. deren Beschichtung dagegen müssen weder von Aluminium benetzbar sein noch eine elektrische Leitfähigkeit besitzen. Sie müssen lediglich mit geschmolzenem Aluminium kompatibel sein, eine ausreichende mechanische Festigkeit aufweisen und einen hohen Wärmeschockwiderstand besitzen. Materialien, welche diesen Bedingungen genügend entsprechen, sind wesentlich preisgünstiger als die für die oberen Teile bzw. deren Beschichtung eingesetzten, durch Aluminium benetzbaren und elektrisch leitenden Materialien.The lower parts of the elements or their coating, on the other hand, need not be wettable by aluminum or have electrical conductivity. They only have to be compatible with molten aluminum, have sufficient mechanical strength and high thermal shock resistance. Materials that meet these conditions sufficiently are much cheaper than the aluminum-wettable and electrically conductive materials used for the upper parts or their coating.

Weiter sind für den unteren Teil der Elemente verwendete Formteile aus Isolatormaterial wesentlich leichter herzustellen, was sich - zusammen mit den günstigeren Gestehungskosten für die Materialien darin ausdrückt, dass eine Massenproduktion von unteren Teilen 10- bis 20-mal billiger ist als diejenige von oberen Teilen. Als Beispiele für solche Isolatormaterialien, welche nie in Kontakt mit dem schmelzflüssigen Elektrolyten kommen, seien hochgesintertes Aluminiumoxid, aluminiumoxidhaltige Keramiken, Siliziumkarbid oder siliziumnitridgebundenes Siliziumkarbid genannt. Diese Materialien weisen ein höheres spezifisches Gewicht als Aluminium auf und sind erosionsfest, was wegen des im zirkulierenden Aluminium vorhandenen Schlammes von Bedeutung ist.Furthermore, molded parts made of insulator material used for the lower part of the elements are much easier to produce, which - together with the lower production costs for the materials - is expressed in the fact that mass production of lower parts is 10 to 20 times cheaper than that of upper parts. Examples of such insulator materials which never come into contact with the molten electrolyte include highly sintered aluminum oxide, aluminum oxide-containing ceramics, silicon carbide or silicon nitride-bonded silicon carbide. These materials have a higher specific weight than aluminum and are erosion-resistant, which is important because of the sludge present in the circulating aluminum.

Sowohl der untere als auch der obere Teil eines Kathodenelementes kann - statt als homogener Vollkörper ausgebildet zu sein - einen Kern aus einem weniger kostspieligen, mechanisch stabilen Material, wie z.B. Stahl, Titan oder Graphit, haben, welcher nach einem bekannten Verfahren mit mindestens einem der entsprechenden Materialien beschichtet wird. Falls als Kernmaterial Graphit verwendet wird, kann der Verbundkörper mit Hilfe eines Sinterverfahrens hergestellt werden.Both the lower and the upper part of a cathode element can - instead of being designed as a homogeneous solid body - a core made of a less expensive, mechanically stable material, such as e.g. Steel, titanium or graphite, which is coated with at least one of the corresponding materials by a known method. If graphite is used as the core material, the composite body can be produced using a sintering process.

Die Kathodenelemente bestehen vorzugsweise aus mehreren Unterelementen. Dabei sind die den oberen Teil bildenden, elektrisch leitenden Unterelemente zweckmässig von möglichst einfacher geometrischer Form, z.B. 1 - 2 cm dicken, vertikal angeordneten Platten, wobei der Abstand zwischen den Platten grösser ist als deren Dicke. Die den unteren Teil bildenden, leicht form- und bearbeitbaren Unterelemente aus Isoliermaterial bilden einen Träger bzw. eine Stützkonstruktion für die oberen Unterelemente.The cathode elements preferably consist of several sub-elements. The electrically conductive sub-elements forming the upper part are expediently of the simplest possible geometric shape, e.g. 1 - 2 cm thick, vertically arranged plates, the distance between the plates being greater than their thickness. The easily formable and editable sub-elements made of insulating material forming the lower part form a support or a support structure for the upper sub-elements.

Mit Kombinationen von Unterlementen ist es möglich, einfache elektrisch leitende Hartmetallteile ohne mechanische oder andere Nachbearbeitung nach dem Sintern, also mit möglicherweise grossen Abweichungen der Ist-Masse, zu einer genügend formstabilen Baugruppe zu vereinigen, welche eine Beanspruchung durch Hebewerkzeuge beim Einlegen oder Herausnehmen aus der Elektrolysezelle ohne Zerstörung der verhältnismässig empfindlichen oberen Teile in Folge von Schlägen, Biegebeanspruchungen usw. erlauben. Auch während des Betriebs der Elektrolysezelle auftretende mechanische Einwirkungen sind weniger gefährlich.With combinations of sub-elements, it is possible to combine simple, electrically conductive hard metal parts without mechanical or other post-processing after sintering, i.e. with possibly large deviations in the actual mass, to form a sufficiently dimensionally stable assembly, which is stressed by lifting tools when inserting or removing them from the Allow electrolysis cell without destroying the relatively sensitive upper parts as a result of impacts, bending stresses, etc. Mechanical influences occurring during the operation of the electrolytic cell are also less dangerous.

Die Abmessungen und damit das Gewicht der eingesetzten elektrisch leitenden Teile, welche die weitaus grösste wirtschaftliche Belastung bringen, sind bedeutend geringer als in allen bekannten Zellen mit Festkörperkathoden.The dimensions and thus the weight of the electrically conductive parts used, which bring the greatest economic burden by far, are significantly smaller than in all known cells with solid-state cathodes.

Die horizontalen Flächenabmessungen der Kathodenelemente sind zweckmässig derart ausgestaltet, dass ein ganzzahliges, zwischen;l und 7 liegendes Vielfaches den horizontalen Flächenabmessungen der darüberliegenden Anode entspricht. Bevorzugt sind jedoch die horizontalen geometrischen Abmessungen von einem Kathodenelement und der entsprechenden Anode von gleicher Grössenordnung.The horizontal surface dimensions of the cathode elements are expediently designed such that an integer multiple, between 1 and 7, corresponds to the horizontal surface dimensions of the anode located above. However, the horizontal geometric dimensions of a cathode element and the corresponding anode of the same order of magnitude are preferred.

Beim Einsetzen oder Auswechseln eines Kathodenelementes kann die darüber liegende Anode kurzfristig entfernt werden. Dies ist aus folgenden Gründen ein entscheidender Vorteil:

  • - Defekte Kathodenelemente können ohne Betriebsunterbruch ersetzt werden.
  • - Bei in bezug auf den Ofengang oder Wirkungsgrad unbefriedigenden Elektrolysezellen können anders gestaltete Kathodenelemente eingesetzt werden.
When inserting or replacing a cathode element, the anode above it can be removed for a short time. This is a key benefit for the following reasons:
  • - Defective cathode elements can be replaced without interrupting operation.
  • - If the electrolysis cells are unsatisfactory in terms of furnace operation or efficiency, differently designed cathode elements can be used.

Wie bereits in der DE-OS 28 38 965 beschrieben, ist die Art der Stromzuführung von der Stromquelle zur Kathodenoberfläche von ausschlaggebender Bedeutung für den Ofengang: Der zwischen Anode und Kathodenelement befindliche Elektrolyt wird unter dem Einfluss des Elektrolysestromes und des Magnetfeldes einer magnetohydrodynamischen Pumpwirkung ausgesetzt.As already described in DE-OS 28 38 965, the type of power supply from the power source to the cathode surface is of crucial importance for the furnace operation: the electrolyte located between the anode and the cathode element is exposed to a magnetohydrodynamic pumping action under the influence of the electrolysis current and the magnetic field.

Die Erfindung wird anhand von in der Zeichnung schematisch dargestellten Ausführungsbeispielen näher erläutert. Es zeigen:

  • - Fig. 1 einen teilweisen Vertikalschnitt durch den aktiven Bereich einer Elektrolysezelle, in Längsrichtung der von Aluminium benetzbaren Kathodenplatten
  • - Fig. 2 einen Vertikalschnitt an der Stelle II - II von Fig. l, in Querrichtung der Kathodenplatten
  • - Fig. 3 einen Horizontalschnitt durch III - III von Fig. 2
  • - Fig. 4 einen vertikalen Längsschnitt durch eine Variante von Kathodenplatten
  • - Fig. 5 einen vertikalen Längsschnitt durch eine weitere Variante von Kathodenplatten.
The invention is explained in more detail with reference to exemplary embodiments schematically shown in the drawing. Show it:
  • 1 shows a partial vertical section through the active area of an electrolysis cell, in the longitudinal direction of the cathode plates which can be wetted by aluminum
  • - Fig. 2 is a vertical section at point II - II of Fig. 1, in the transverse direction of the cathode plates
  • 3 shows a horizontal section through III-III of FIG. 2
  • 4 shows a vertical longitudinal section through a variant of cathode plates
  • 5 shows a vertical longitudinal section through a further variant of cathode plates.

Ein Kathodenelement 10 mit einem oberen Teil aus den elektrisch leitfähigen, von Aluminium benetzbaren Platten 12 und einem unteren Teil aus mit Aluminium kompatiblen Formplatten 14, 16 ist in den Fig. 1 - 3 dargestellt. Im vorliegenden Beispiel sind die benetzbaren Kathodenplatten 12 mittels runder Bolzen 18 mit Isolatorplatten 14 gleicher Dimensionen mecha- nisch stabil verbunden. Die Bolzen 18 bestehen vorzugsweise aus dem besser bearbeitbaren und billigeren Isolatormaterial; sie kommen nicht in Kontakt mit dam schmelflüssigen Elektrolyten.A cathode element 10 with an upper part made of the electrically conductive aluminum-wettable plates 12 and a lower part made of aluminum-compatible shaped plates 14, 16 is shown in FIGS. 1-3. In the present example, the wettable cathode plates 12 by means of a round bolt 18 with the same dimensions insulator plates 14 mechanically n ic stably connected. The bolts 18 are preferably made of the more easily machinable and cheaper insulator material; they do not come into contact with the molten electrolyte.

Die Auflageplatten 14 aus Isolatormaterial weisen auf ihrer Unterseite Ausnehmungen 20 auf, die ihrerseits formschlüssig in Ausnehmungen 22 der ebenfalls aus Isolatormaterial bestehenden Stützplatten 16 passen.The support plates 14 made of insulator material have recesses 20 on their underside, which in turn fit in a form-fitting manner in recesses 22 of the support plates 16 likewise made of insulator material.

Dadurch wird mit einfachen Mitteln ein mechanisch stabiles Kathodenelement 10 gebildet, bei welchem eine Gruppe von durch Aluminium benetzbaren Kathodenplaten 12 mittels einer Stützkonstruktion aus wesentlich billigerem Material zu einer Einheit zusammengefügt wird. Die Masse dieses Kathodenelemen- tes 10 ist gross genug, um von den Badströmungen nicht verschoben oder weggetragen zu werden.Thereby a mechanically stable K is formed athodenelement 10 with simple means, in which a group is joined by aluminum-wettable cathode Platen 12 by means of a support structure from significantly cheaper material to form a unit. The mass of this K athodenelemen- tes 10 is large enough to not be moved or carried away by the Badströmungen.

Falls eine weitere Erhöhung der mechanischen Stabilität erwünscht ist, können Zwischenstücke, z. B. in Form von Keilen, und/oder gegen flüssiges Aluminium beständige Zemente verwendet werden. Die Elemente können sich auch nachher hinrei- chend thermischen Dehnungen anpassen.If a further increase in mechanical stability is desired, intermediate pieces, e.g. B. in the form of wedges and / or cements resistant to liquid aluminum. The elements can customize c based thermal expansions also subsequently obtain reasonable.

Die Stützplatten 16 weisen auf ihrer Unterseite Aussparungen 24 auf, welche im wesentlichen aus drei Gründen vorgesehen sind:

  • - Das flüssige Aluminium 26 kann frei zirkulieren, dadurch wird die Ausbildung eines Bodenschlammes verhindert
  • - Es werden Materialkosten eingespart
  • - Das Kathodenelement 10 kann besser in die Zelle eingesetzt bzw. daraus entfernt werden.
The support plates 16 have cutouts 2 4 on their underside, which are provided essentially for three reasons:
  • - The liquid aluminum 26 can circulate freely, thereby preventing the formation of a soil sludge
  • - Material costs are saved
  • - The cathode element 10 can be better inserted into or removed from the cell.

Die elektrisch leitenden Kathodenplatten 12 haben von der abbrennenden Kohleanode 28 die Interpolardistanz d. Während des Elektrolyseprozesses verbraucht sich der Elektrolyt in einem engen Spalt zwischen Kathodenplatten und Anode rasch. Die Kathodenplatten 12 sind verhältnismässig schmal; deshalb kann die Badströmung auch bei gegenüber dem Normalwert von 6 - 6,5 cm für d stark herabgesetztem Wert den an Aluminiumoxid verarmten Elektrolyten im Interpolarspalt rasch erneuern. Das abgeschiedene Metall bildet auf den benetzbaren Kathodenplatten 12 einen ununterbrochenen Film und fliesst zum Metallsumpf 26 hinunter.The electrically conductive cathode plates 12 have the interpolar distance d from the burning carbon anode 28. During the electrolysis process, the electrolyte is quickly used up in a narrow gap between the cathode plates and the anode. The cathode plates 12 are relatively narrow; therefore the bath flow can rapidly renew the electrolyte depleted of aluminum oxide in the interpolar gap, even if the value is greatly reduced compared to the normal value of 6 - 6.5 cm for d. The deposited metal forms an uninterrupted film on the wettable cathode plates 12 and flows down to the metal sump 26.

Die Oberfläche 32 des flüssigen Aluminiums 26 muss stets im Bereich der benetzbaren Kathodenplatten 12 liegen, insbesondere beim Schöpfen darf dieser Metallstand nie in den Bereich der Isolatorplatten 14, 16 absinken. Dies würde sowohl einen Stromunterbruch als auch korrosive Zerstörung der Isolatorplatten bedeuten.The surface 32 of the liquid aluminum 26 must always lie in the area of the wettable cathode plates 12, in particular when scooping, this metal level must never sink into the area of the insulator plates 14, 16. This would mean both a power cut and corrosive destruction of the insulator plates.

Der Elektrolysegleichstrom fliesst von den Anoden 28 über den im Interpolarspalt befindlichen Elektrolyten 30 zu den Kathodenplatten 12, tritt dann in das flüssige Aluminium 26 über und fliesst schliesslich via Kohleboden 34 in die eisernen Kathodenbarren 36.The direct electrolysis current flows from the anodes 28 via the electrolytes 30 in the interpolar gap to the cathode plates 12, then passes into the liquid aluminum 26 and finally flows via the carbon bottom 34 into the iron cathode bars 36.

Aus Fig. 2 ist ersichtlich, dass die Arbeitsfläche der Anode 28 die Form der Kathoden kopiert. Aus diesem Grunde werden erfindungsgemäss bevorzugt sich über die ganze Breite der Anodenarbeitsflächen erstreckende Platten eingesetzt.It can be seen from FIG. 2 that the working surface of the anode 28 copies the shape of the cathodes. For this reason, according to the invention, preference is given to the entire width of the Anode work surfaces extending plates used.

Es könnten im Prinzip auch benetzbare Kathoden ausgebildet werden, welche beispielsweise nach dem Stand der Technik bekannte Rohre aufweisen. Dadurch würden sich aber in der Arbeitsfläche der Anoden entsprechende Aussparungen ausformen, die während des Elektrolyseprozesses die Bildung von die Stromausbeute vermindernden Gassäcken zur Folge hätten.In principle, wettable cathodes could also be formed which, for example, have tubes known from the prior art. As a result, however, corresponding recesses would form in the working surface of the anodes, which would result in the formation of gas bags which reduce the current efficiency during the electrolysis process.

Im Kohleboden 34 der Elektrolysezelle können Führungsnuten 35 ausgebildet sein, welche ein seitliches Abrutschen der Kathodenelemente 10 verunmöglichen.Guide grooves 35 can be formed in the carbon base 34 of the electrolytic cell, which prevent the cathode elements 10 from slipping sideways.

In Fig. 4 wird eine Variante einer Kathodenplatte 12 dargestellt. Die Ausbildung eines Fensters 38 erlaubt die Einsparung von Material und verbessert die Strömungsbedingungen im Elektrolyten. Auf der Unterseite weist die Platte 12 einen Schwalbenschwanz 40 auf, der in eine entsprechende Aussparung der Trägerplatte 14 eingeführt werden kann. Die Stützkonstruktion aus Isolatormaterial ist dann so ausgestaltet, dass die Platten nicht seitlich verschoben werden können.4 shows a variant of a cathode plate 12. The formation of a window 38 allows material to be saved and improves the flow conditions in the electrolyte. On the underside, the plate 12 has a dovetail 40 which can be inserted into a corresponding recess in the carrier plate 14. The support structure made of insulator material is then designed so that the plates cannot be moved laterally.

Eine weitere Variante von benetzbaren Kathodenplatten 12 wird in Fig. 5 dargestellt. Sowohl die Ausbildung eines Fensters 38 als auch die abgeschrägte Unterseite sind einerseits dazu bestimmt, benetzbares Kathodenmaterial einzusparen, und andererseits die Strömungsverhältnisse im Bad zu optimalisieren. Die Kathodenplatte 12 ist mittels eines im Zentrum nach unten gerichteten Fortsatzes 42 in einer Stützplatte 14 befestigt.Another variant of wettable cathode plates 12 is shown in FIG. 5. Both the formation of a window 38 and the bevelled underside are intended on the one hand to save wettable cathode material and on the other hand to optimize the flow conditions in the bath. The cathode plate 12 is fastened in a support plate 14 by means of an extension 42 directed downwards in the center.

Mit dem in der Beschreibung verwendeten Begriff "Isolatormaterial" werden auch elektrisch schlecht leitende Materialien erfasst. Dagegen werden für die Stützkonstruktion nie elektrisch gut leitende Materialien eingesetzt, weil .

  • - sie teurer und schwieriger herstellbar sind, und
  • - sich an den Uebergangsstellen zu den gut leitenden Kathodenplatten 12 Kontakterscheinungen und -erosion ausbilden würden.
The term "insulator material" used in the description also covers poorly conductive materials. In contrast, electrically good conductive materials are never used for the support structure because.
  • - they are more expensive and more difficult to manufacture, and
  • - 12 contact phenomena and erosion would form at the transition points to the highly conductive cathode plates.

Eine Stützkonstruktion 14, 16 an sich ist nicht Gegenstand der Erfindung, es kann dazu jede geeignete, in anderen Gebieten der Technik verwendete Variante eingesetzt werden.A support structure 14, 16 per se is not the subject of the invention; any suitable variant used in other fields of technology can be used for this purpose.

Die erfindungsgemässen Kathodenelemente 10 können auch zur Umrüstung von bestehenden Elektrolysezellen eingestzt werden, indem einfach den Anodendimensionen und dem Metallstand angepasste Einheiten auf den Kohleboden gestellt werden. Dadurch kann mit geringen Mehrkosten die Interpolardistanz vermindert, und dadurch die Stromausbeute erhöht werden. Insbesondere ist zu beachten, dass die Umrüstung ohne Ausserbetriebsetzen der Elektrolysezelle erfolgen kann und das allfällige spätere Auswechseln von defekten Kathodenelementen keine Probleme bietet.The cathode elements 10 according to the invention can also be used for converting existing electrolysis cells by simply placing units adapted to the anode dimensions and the metal level on the carbon floor. As a result, the interpolar distance can be reduced at low additional costs, and the current yield can thereby be increased. In particular, it should be noted that the retrofitting can be carried out without decommissioning the electrolytic cell and that subsequent replacement of defective cathode elements does not pose any problems.

Claims (10)

1. Kathode aus einzeln auswechselbaren Elementen für eine Schmelzflusselektrolysezelle zur Herstellung von Aluminium,
dadurch gekennzeichnet, dass
die Elemente (10) aus zwei mechanisch starr miteinander verbundenen, gegen Wärmeschocks widerstandsfähigen Teilen - einem vom schmelzflüssigen Elektrolyten (30) in das abgeschiedene Aluminium (26) hineinragenden oberen (12) und einem ausschliesslich im flüssigen Aluminium (26) angeordneten unteren Teil (14, 16) - aus verschiedenen Materialien gebildet sind,
wobei - der obere Teil (12) bzw. dessen Beschichtung aus einem bei Arbeitstemperatur elektrisch gut leitenden, chemisch beständigen und von Aluminium benetzbaren Material, und - der untere Teil (14, 16) bzw. dessen Beschichtung aus einem gegen das flüssige Aluminium beständige Isolatormaterial besteht. 1. cathode made of individually replaceable elements for a melt flow electrolysis cell for the production of aluminum,
characterized in that
the elements (10) consist of two mechanically rigidly connected parts that are resistant to thermal shocks - an upper part (12) projecting from the molten electrolyte (30) into the deposited aluminum (26) and a lower part (14 arranged exclusively in the liquid aluminum (26) , 16) - are made of different materials,
in which - The upper part (12) or its coating made of a material that is highly electrically conductive at work temperature, chemically resistant and wettable by aluminum, and - The lower part (14, 16) or its coating consists of an insulator material resistant to the liquid aluminum. 2. Kathode nach Anspruch 1, dadurch gekennzeichnet, dass der obere Teil der Elemente (10) aus vertikal angeordneten Platten (12), die sich mit horizontaler Oberfläche vorzugsweise über den ganzen Bereich der Arbeitsfläche der entsprechenden Anode (28) erstrecken, bestehen.2. Cathode according to claim 1, characterized in that the upper part of the elements (10) from vertically arranged plates (12), which preferably extend over the entire area of the working surface of the corresponding anode (28) with a horizontal surface. 3. Kathode nach Anspruch 2, dadurch gekennzeichnet, dass der Abstand zwischen den Platten (12) grösser ist als deren Dicke.3. Cathode according to claim 2, characterized in that the distance between the plates (12) is greater than their thickness. 4. Kathode nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Elemente (10) durch Zwischenstücke und/oder gegen flüssiges Aluminium beständige Zemente weiter stabilisiert sind.4. Cathode according to one of claims 1 to 3, characterized in that the elements (10) are further stabilized by spacers and / or cements resistant to liquid aluminum. 5. Kathode nach mindestens einem der Ansprüche 1 - 4, dadurch gekennzeichnet, dass ein zwischen 1 und 7 liegendes ganzzahliges Vielfaches der horizontalen Flächenabmessungen eines Elementes (10) den horizontalen Flächenabmessungen der darüberliegenden Anode (28) entspricht.5. Cathode according to at least one of claims 1-4, characterized in that an integer multiple of 1 to 7 of the horizontal surface dimensions of an element (10) corresponds to the horizontal surface dimensions of the overlying anode (28). 6. Kathode nach mindestens einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass in den elektrisch leitenden Kathodenplatten (12) Fenster (38) ausgespart sind.6. Cathode according to at least one of claims 1 to 5, characterized in that in the electrically conductive cathode plates (12) windows (38) are recessed. 7. Kathode nach mindestens einem der Ansprüche 1 - 6, dadurch gekennzeichnet, dass die oberen (12) und/oder unteren Teile (14, 16) einen Kern aus Stahl, Titan oder Graphit haben, welcher mit mindestens einem entsprechenden Material beschichtet ist.7. Cathode according to at least one of claims 1-6, characterized in that the upper (12) and / or lower parts (14, 16) have a core made of steel, titanium or graphite, which is coated with at least one corresponding material. 8. Kathode nach mindestens einem der Ansprüche 1 - 7, dadurch gekennzeichnet, dass der obere Teil (12) bzw. dessen Beschichtung aus Titandiborid, Titankarbid, Titannitrid, Zirkondiborid, Zirkonkarbid, Zirkonnitrid oder Mischungen davon besteht.8. Cathode according to at least one of claims 1-7, characterized in that the upper part (12) or its coating consists of titanium diboride, titanium carbide, titanium nitride, zirconium diboride, zirconium carbide, zirconium nitride or mixtures thereof. 9. Kathode nach Anspruch 8, dadurch gekennzeichnet, dass das Material des oberen Teils (12) bzw. dessen Beschichtung eine geringe Menge zugemischten Bornitrids enthält.9. Cathode according to claim 8, characterized in that the material of the upper part (12) or its coating contains a small amount of admixed boron nitride. 10. Kathode nach mindestens einem der Ansprüche 1 - 9, dadurch gekennzeichnet, dass der untere Teil (14, 16) bzw. dessen Beschichtung aus hochgesintertem Aluminiumoxid, aluminiumoxidhaltigen Keramiken, Siliziumkarbid oder siliziumnitridgebundenem Siliziumkarbid besteht.10. Cathode according to at least one of claims 1-9, characterized in that the lower part (14, 16) or its coating consists of highly sintered aluminum oxide, aluminum oxide-containing ceramics, silicon carbide or silicon nitride-bonded silicon carbide.
EP81810185A 1980-05-23 1981-05-15 Cathode for molten-salt electrolysis cell Expired EP0041045B1 (en)

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US5413689A (en) * 1992-06-12 1995-05-09 Moltech Invent S.A. Carbon containing body or mass useful as cell component
AU674718B2 (en) * 1993-04-19 1997-01-09 Moltech Invent S.A. Treated carbon or carbon-based cathodic components of aluminium production cells
US5679224A (en) * 1993-11-23 1997-10-21 Moltech Invent S.A. Treated carbon or carbon-based cathodic components of aluminum production cells
US5409593A (en) * 1993-12-03 1995-04-25 Sifco Industries, Inc. Method and apparatus for selective electroplating using soluble anodes
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US6719890B2 (en) * 2002-04-22 2004-04-13 Northwest Aluminum Technologies Cathode for a hall-heroult type electrolytic cell for producing aluminum
AUPS212802A0 (en) * 2002-05-03 2002-06-06 Mount Isa Mines Limited Reducing power consumption in electro-refining or electro- winning of metal
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FR2508496A2 (en) * 1981-02-24 1982-12-31 Pechiney Aluminium Aluminium production in a Hall-Heroult cell - with removable refractory cathode elements
AU571246B2 (en) * 1983-07-27 1988-04-14 Swiss Aluminium Ltd. Electrolytic purification of aluminium

Also Published As

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ES502372A0 (en) 1982-04-01
US4376690A (en) 1983-03-15
CA1163601A (en) 1984-03-13
NZ197038A (en) 1984-04-27
AU7029981A (en) 1981-11-26
ATE3884T1 (en) 1983-07-15
IS1170B6 (en) 1984-12-28
AU543106B2 (en) 1985-04-04
DE3160478D1 (en) 1983-07-28
NO155104C (en) 1987-02-11
IS2641A7 (en) 1981-11-24
NO811711L (en) 1981-11-24
YU132181A (en) 1983-06-30
BR8103210A (en) 1982-02-16
ZA813338B (en) 1982-05-26
NO155104B (en) 1986-11-03
EP0041045B1 (en) 1983-06-22
ES8203989A1 (en) 1982-04-01
JPS5719391A (en) 1982-02-01

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