EP0099331B1 - Aluminium electrolysis cell pot - Google Patents

Aluminium electrolysis cell pot Download PDF

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Publication number
EP0099331B1
EP0099331B1 EP83810282A EP83810282A EP0099331B1 EP 0099331 B1 EP0099331 B1 EP 0099331B1 EP 83810282 A EP83810282 A EP 83810282A EP 83810282 A EP83810282 A EP 83810282A EP 0099331 B1 EP0099331 B1 EP 0099331B1
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Prior art keywords
carbon
layer
shear strength
lining
tank according
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EP83810282A
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German (de)
French (fr)
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EP0099331A1 (en
Inventor
Max Zollinger
Raoul Jemec
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Alcan Holdings Switzerland AG
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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

Definitions

  • the invention relates to a cathode tub of a melt flow electrolysis cell for the production of aluminum, consisting of an outer steel tub supported or supported by metal components, a heat-insulating layer and an electrically conductive inner lining made of carbon which is resistant to the molten aluminum and the electrolytes.
  • the carbon lining experiences a significant increase in volume over the course of its operating life. This is caused by the penetration of components that come from the electrolyte.
  • Components are understood to mean, for example, sodium or salts from which the fluoride melt is composed, and chemical compounds which have arisen from the fluoride melt by reactions which are not known in more detail.
  • the swelling carbon lining presses on the thermal insulation and thus indirectly on the steel tub. This can cause irreversible deformations that can strain them into the plastic area of the steel and cause them to tear.
  • DE-AS 2633055 proposes to form a bulge in the steel trough. This includes a storage space which is completely filled with a first, easily deformable material and a second material which can only be deformed with greater forces, in order to accommodate the bottom of the carbon lining, which expands in the horizontal direction during operation.
  • the second material has such mechanical properties that the forces are transmitted to the bulged steel jacket without permanent deformation and / or cracking. The opposing forces acting on the bottom of the carbon lining reduce its bulging and cracking.
  • an electrolysis cell for the production of aluminum in which the insulation and the cathode blocks made of carbon or the side walls made of anthracite and the carbon-containing ramming masses are separated by a shell-shaped intermediate layer.
  • This intermediate layer consists of powder or granular silicon carbide, which represents an insurmountable barrier for the molten metal.
  • the inventors have set themselves the task of creating a new concept for a cathode trough of a melt flow electrolysis cell for the production of aluminum, which can prevent uncontrolled deformations in cells of all sizes without causing damage to the cell in the form of cracking.
  • the concept should continue to make do with low investment costs and be flexible to use.
  • the object is achieved according to the invention by a layer which is arranged horizontally and exclusively in the area of the electrolyte and separates the carbon lining into a lower and an upper part from a material which is resistant to the electrolyte and which is resistant to temperatures up to 1000 ° C. Lich lower shear strength than that of the carbon lining.
  • the side wall of the carbon lining is divided.
  • the electric field between the cathode bars and the anodes passes through the bottom and lower part of the side wall of the carbon liner.
  • practically no electrical current flows through the part of the side wall of the carbon lining that lies above the layer with low shear strength. Therefore, the lower part of the carbon lining swells much more than the upper part.
  • the resulting tensions are absorbed by the layer with low shear strength tearing. Since it must lie completely in the area of the molten electrolyte, no liquid aluminum can enter the cracks formed.
  • the crack in the layer with low shear strength is self-healing; the molten electrolyte penetrating the crack cools so much in the outer area of the wall that it solidifies and thus prevents the electrolyte from flowing out.
  • the self-healing of the predetermined breaking point can be improved by arranging a collecting zone made of very good heat-conducting material that extends in the direction of the side wall of the outer steel trough directly outside the layer with low shear strength and the area of the carbon lining adjoining it below. This means that the heat given off by the electrolytes entering the crack can be dissipated more quickly, and self-healing through solidification takes place more quickly.
  • the upper limit of this collecting zone is expediently at approximately the same level as the upper limit of the layer with low shear strength. However, the collecting zone is thicker than this layer, it is advantageously two to three times as thick as the layer with low shear strength.
  • Metallic materials, such as steel wool or aluminum chips, are particularly well suited for the rapid dissipation of heat in the collecting zone.
  • the shear strength of the layer which separates the carbon lining into a lower and an upper part, is preferably at least five times less than that of carbon.
  • this layer with low shear strength is expediently between 2 and 15 cm, preferably between 5 and 10 cm.
  • the layer separating the carbon lining into two parts is expediently built up from prefabricated blocks.
  • the materials for these blocks must meet the three requirements of temperature resistance, resistance to the electrolyte and low shear strength.
  • foamed carbon, foamed ceramic materials and compressed carbon fiber layers can be used for the production of the blocks.
  • the layer with low shear strength is expediently glued to the carbon lining at the top with a known adhesive and placed on the carbon lining at the bottom via a carbon felt.
  • the compressed carbon felt is preferably between 5 and 15 mm thick and in turn glued to the lower part of the carbon lining.
  • this lower part can be graphitized more.
  • a melt flow electrolysis cell for the production of aluminum has an outer steel trough 10.
  • the lower insulation 12 and the lateral insulation 14 are embedded therein.
  • the lower insulation 12, which forms the substructure, is the lower one Part 16 of the carbon lining with cast or embedded, iron cathode bars 18 arranged.
  • the approximately 8 cm thick layer 20 with low shear strength is arranged on the horizontally delimited edge region of the lower part 16 of the carbon lining. Between this layer 20 and the lower part 16 of the carbon lining there is a base (not visible) made of carbon felt, which is glued to the lower part 16 of the carbon lining.
  • the upper part 22 of the carbon lining is glued to the layer 20 with low shear strength, it projects beyond the lower part laterally.
  • the uppermost area is formed by stone blocks 24, which ensures an insulating tub shelf that protects against the effects of oxygen.
  • Prestressed «crunch elements» 26 are arranged within the steel trough 10, at the level of the upper region of the bottom of the carbon lining, and are supported by a bulge in the steel trough 10.
  • the “crunch elements” 26 oppose the expanding lower part 16 of the carbon lining with a constant, path-independent resistance.
  • a very good heat-conducting layer is designed as a collecting zone 30. It extends in the vertical direction, downward, beyond the layer 20 with low shear strength and extends partially along the lower part 16 of the carbon lining.
  • a flexible wall 32 part of the side region of the steel tub 10 is replaced by a flexible wall 32.
  • fabrics made of carbon fibers, which are combined in a layered construction with metal foils, can be used.
  • the prestressed “crunch elements” 26 arranged outside the flexible wall 32 consist, as in FIG. 1, of packages of plastically deformable, vertically arranged tubes. Towards the outside, the “crunch elements” 26 are supported by a fixed abutment 28.
  • a sliding layer can be arranged between the flexible wall 32 and the lateral insulation.
  • Fig. 3 shows a block of carbon foam 20 lying on a carbon felt 34 with low shear strength. Because of the different expansion of the lower part 16 and the upper part 22 of the carbon lining, the layer 20 with low shear strength has cracked for the first time, liquid electrolyte has penetrated and partially solidified.
  • the layer 20 with low shear strength has been torn once, according to FIG. 4 several times.
  • the carbon felt 34 has partially dissolved after the repeated tearing and the solidified electrolyte 36 has penetrated further outwards.
  • 3 to 5 show - based on electrolysis cells with different dimensions of the individual components - the self-healing effect of the predetermined breaking point:
  • the trough containing the melt flow electrolyte and the separated liquid aluminum can tear only at one point, the layer 20 with low shear strength. There is only molten electrolyte in this area, no metal.
  • the electrolyte escaping through cracks in this layer 20 solidifies and although it continues to extend outwards, it always has a self-healing effect in that the solidified material prevents the flowing material from escaping further.

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  • 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)
  • Micro-Organisms Or Cultivation Processes Thereof (AREA)
  • Immobilizing And Processing Of Enzymes And Microorganisms (AREA)
  • Secondary Cells (AREA)

Description

Die Erfindung bezieht sich auf eine Kathodenwanne einer Schmelzflusselektrolysezelle zur Herstellung von Aluminium, bestehend aus einer von Metallbauteilen getragenen bzw. gestützten äusseren Stahlwanne, einer wärmedämmenden Isolationsschicht und einer elektrisch leitenden, gegen das schmelzflüssige Aluminium und den Elektrolyten beständigen Innenauskleidung aus Kohlenstoff.The invention relates to a cathode tub of a melt flow electrolysis cell for the production of aluminum, consisting of an outer steel tub supported or supported by metal components, a heat-insulating layer and an electrically conductive inner lining made of carbon which is resistant to the molten aluminum and the electrolytes.

Für die Gewinnung von Aluminium durch Schmelzflusselektrolyse 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. In den Elektrolyten tauchen von oben Anoden ein, die bei konventionellen Verfahren aus amorphem Kohlenstoff bestehen. 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 in einem Temperaturbereich von etwa 940 bis 970°C statt.For the production of aluminum by melt flow electrolysis of aluminum oxide, this is dissolved in a fluoride melt, which consists largely 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, which consist of amorphous carbon in conventional processes, are immersed in the electrolyte. 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 takes place in a temperature range of approximately 940 to 970 ° C.

Die Kohlenstoffauskleidung erfährt im Verlaufe der Betriebsdauer eine bedeutsame Volumenzunahme. Diese wird durch das Eindringen von Komponenten, die aus dem Elektrolyten stammen, verursacht. Unter Komponenten werden beispielsweise Natrium oder Salze, aus denen die Fluoridschmelze zusammengesetzt ist, sowie chemische Verbindungen, die durch nicht näher bekannte Reaktionen aus der Fluoridschmelze entstanden sind, verstanden.The carbon lining experiences a significant increase in volume over the course of its operating life. This is caused by the penetration of components that come from the electrolyte. Components are understood to mean, for example, sodium or salts from which the fluoride melt is composed, and chemical compounds which have arisen from the fluoride melt by reactions which are not known in more detail.

Weiter sind insbesondere zwei wesentliche Einflussfaktoren, welche das Aufquellen der Kathodenkohle im Betrieb steuern, bekannt:

  • - Die angelegte Stromdichte: Je grösser die Stromdichte, umso grösser ist die Volumenzunahme.
  • - Die Qualität des Kohlenstoffs: Je höher der Graphitisierungsgrad, desto kleiner ist die Volumenzunahme.
In addition, two main influencing factors that control the swelling of the cathode carbon during operation are known in particular:
  • - The current density applied: the greater the current density, the greater the volume increase.
  • - The quality of carbon: the higher the degree of graphitization, the smaller the volume increase.

Die aufquellende Kohlenstoffauskleidung drückt auf die thermische Isolation und damit indirekt auf die Stahlwanne. Diese kann dadurch nichtreversible Verformungen erleiden, die sie bis in den plastischen Bereich des Stahles beanspruchen und zum Reissen bringen können.The swelling carbon lining presses on the thermal insulation and thus indirectly on the steel tub. This can cause irreversible deformations that can strain them into the plastic area of the steel and cause them to tear.

Die Neigung zur Aufwölbung des Kohlenstoffbodens steigt mit zunehmendem Zellenalter; bei der Aufwölbung entstehen Risse. Das flüssige Aluminium kann dann durch diese Risse eindringen und die eisernen Kathodenbarren, welche den elektrischen Gleichstrom abführen, angreifen. Die Zerstörung der Auskleidung der Zelle kann soweit fortschreiten, dass das flüssige Aluminium aus der Zelle ausfliesst. In diesem Fall muss die Zelle im allgemeinen vorzeitig ausser Betrieb gesetzt werden. Dies führt zu teuren Reparaturen; ausserdem erleidet man durch den Stillstand derZelle einen Produktionsverlust.The tendency for the carbon base to bulge increases with increasing cell age; cracks appear during the bulging. The liquid aluminum can then penetrate through these cracks and attack the iron cathode bars, which dissipate the electrical direct current. The destruction of the lining of the cell can progress so far that the liquid aluminum flows out of the cell. In this case, the cell must generally be taken out of service prematurely. This leads to expensive repairs; in addition, the cell is at a standstill and there is a loss of production.

Es sind zahlreiche Versuche unternommen worden, durch das Anbringen von Versteifungen auf der Stahlwanne Verformungen und Risse im Kohlenstoffboden zu vermeiden. Diese konnten jedoch üblicherweise nicht verhindert, sondern lediglich vermindert werden. Weiter stellen Versteifungen einen wesentlichen wirtschaftlichen Nachteil dar, die Zelle wird verteuert und das Gesamtgewicht der Kathodenwanne erheblich erhöht.Numerous attempts have been made to prevent deformations and cracks in the carbon floor by applying stiffeners to the steel trough. However, these could usually not be prevented, but only reduced. Furthermore, stiffeners represent a significant economic disadvantage, the cell becomes more expensive and the total weight of the cathode tub is increased considerably.

Andere Anstrengungen hatten das Ziel, die Tränkung der Kohlenstoffauskleidung mit Elektrolytkomponenten und die daraus resultierenden Volumenvergrösserungen zu beseitigen. Es hat sich jedoch gezeigt, dass sich diese Volumenvergrösserung nicht vermeiden lässt und als unabdingbare Voraussetzung hingenommen werden muss. In der DE-AS 2633055 wird vorgeschlagen, in der Stahlwanne eine Ausbuchtung auszuformen. Diese umfasst einen mit einem ersten, leicht verformbaren Material und einem zweiten, erst bei grösseren Kräften verformbaren Material vollständig gefüllten Stauraum zur Aufnahme des Bodens der Kohlenstoffauskleidung, welcher sich während des Betriebes in horizontaler Richtung ausdehnt. Das zweite Material weist solche mechanische Eigenschaften auf, dass die Kräfte ohne dauernde Verformung und/oder Rissbildung auf den ausgebuchteten Stahlmantel übertragen werden. Die auf den Boden der Kohlenstoffauskleidung einwirkenden Gegenkräfte vermindern dessen Aufwölbung und Durchsetzen mit Rissen.Other efforts were aimed at eliminating the impregnation of the carbon lining with electrolyte components and the resulting increase in volume. However, it has been shown that this increase in volume cannot be avoided and must be accepted as an indispensable prerequisite. DE-AS 2633055 proposes to form a bulge in the steel trough. This includes a storage space which is completely filled with a first, easily deformable material and a second material which can only be deformed with greater forces, in order to accommodate the bottom of the carbon lining, which expands in the horizontal direction during operation. The second material has such mechanical properties that the forces are transmitted to the bulged steel jacket without permanent deformation and / or cracking. The opposing forces acting on the bottom of the carbon lining reduce its bulging and cracking.

Obwohl die nach dem Stand der Technik vorgeschlagenen Lösungen, insbesondere diejenige der oben genannten DE-AS 2633055, teilweise Abhilfe bringen, bestehen für Elektrolysezellen mit extrem hohen Stromstärken noch erhebliche Probleme.Although the solutions proposed according to the prior art, in particular those of the above-mentioned DE-AS 2633055, partially remedy the situation, there are still considerable problems for electrolytic cells with extremely high currents.

Weiter ist aus der GB-A 1 209 541 eine Elektrolysezelle zur Herstellung von Aluminium bekannt, bei welcher die Isolation und die Kathodenblöcke aus Kohlenstoff bzw. die Seitenwände aus Anthrazit und die kohlenstoffhaltigen Stampfmassen durch eine schalenförmig ausgebildete Zwischenschicht getrennt sind. Diese Zwischenschicht besteht aus pulver- oder granulatförmigem Siliziumkarbid, welches für das geschmolzene Metall eine unüberwindliche Barriere darstellt.Furthermore, from GB-A 1 209 541 an electrolysis cell for the production of aluminum is known, in which the insulation and the cathode blocks made of carbon or the side walls made of anthracite and the carbon-containing ramming masses are separated by a shell-shaped intermediate layer. This intermediate layer consists of powder or granular silicon carbide, which represents an insurmountable barrier for the molten metal.

Die Erfinder haben sich die Aufgabe gestellt, ein neues Konzept für eine Kathodenwanne einer Schmelzflusselektrolysezelle zur Herstellung von Aluminium zu schaffen, das in Zellen aller Grössenordnungen unkontrollierte Deformationen verhindern kann, ohne dass der Zelle Schaden in Form von Rissbildung zugefügt wird. Das Konzept soll weiter mit geringen Investitionskostenauskommen und flexibel anwendbar sein.The inventors have set themselves the task of creating a new concept for a cathode trough of a melt flow electrolysis cell for the production of aluminum, which can prevent uncontrolled deformations in cells of all sizes without causing damage to the cell in the form of cracking. The concept should continue to make do with low investment costs and be flexible to use.

Die Aufgabe wird erfindungsgemäss gelöst durch eine ausschliesslich im Bereich des Elektrolyten horizontal umlaufend angeordnete, die Kohlenstoffauskleidung in einen untern und einen obern Teil trennende Schicht aus einem bei Temperaturen bis zu 1000°C beständigen, gegen den Elektrolyten resistenten Material von wesentlich geringerer Scherfestigkeit als diejenige der Kohlenstoffauskleidung.The object is achieved according to the invention by a layer which is arranged horizontally and exclusively in the area of the electrolyte and separates the carbon lining into a lower and an upper part from a material which is resistant to the electrolyte and which is resistant to temperatures up to 1000 ° C. Lich lower shear strength than that of the carbon lining.

Nach diesem Konzept ist die Seitenwand der Kohlenstoffauskleidung geteilt. Das elektrische Feld zwischen den Kathodenbarren und den Anoden verläuft durch den Boden und den unteren Teil der Seitenwand der Kohlenstoffauskleidung. Durch den oberhalb der Schicht mit geringer Scherfestigkeit liegenden Teil der Seitenwand der Kohlenstoffauskleidung dagegen fliesst praktisch kein elektrischer Strom. Deshalb quillt der untere Teil der Kohlenstoffauskleidung wesentlich stärker auf als der obere Teil. Die dadurch entstehenden Spannungen werden aufgefangen, indem die Schicht mit geringer Scherfestigkeit reisst. Da sie vollständig im Bereich des schmelzflüssigen Elektrolyten liegen muss, kann kein flüssiges Aluminium in die gebildeten Risse eintreten.According to this concept, the side wall of the carbon lining is divided. The electric field between the cathode bars and the anodes passes through the bottom and lower part of the side wall of the carbon liner. By contrast, practically no electrical current flows through the part of the side wall of the carbon lining that lies above the layer with low shear strength. Therefore, the lower part of the carbon lining swells much more than the upper part. The resulting tensions are absorbed by the layer with low shear strength tearing. Since it must lie completely in the area of the molten electrolyte, no liquid aluminum can enter the cracks formed.

Die als Sollbruchstelle bezeichnete Rissstelle in der Schicht mit geringer Scherfestigkeit ist selbstheilend, der in den Riss eindringende schmelzflüssige Elektrolyt kühlt sich im äusseren Bereich der Wandung so stark ab, dass er erstarrt und so das Ausfliessen des Elektrolyten verhindert.The crack in the layer with low shear strength, known as the predetermined breaking point, is self-healing; the molten electrolyte penetrating the crack cools so much in the outer area of the wall that it solidifies and thus prevents the electrolyte from flowing out.

Die Selbstheilung der Sollbruchstelle kann verbessert werden, indem unmittelbar ausserhalb der Schicht mit geringer Scherfestigkeit und dem Bereich der unten anschliessenden Kohlenstoffauskleidung eine sich in Richtung der Seitenwand der äusseren Stahlwanne erstreckende Auffangzone aus sehr gut wärmeleitendem Material angeordnet ist. Damit kann die von in den Riss eintretenden Elektrolyten abgegebene Wärme rascher abgeführt werden, die Selbstheilung durch Erstarren erfolgt rascher. Zweckmässig ist die obere Begrenzung dieser Auffangzone auf ungefähr gleichem Niveau wie die obere Begrenzung der Schicht mit geringer Scherfestigkeit. Die Auffangzone ist jedoch dicker als diese Schicht, sie ist vorteilhaft zwei bis dreimal so dick wie die Schicht mit geringer Scherfestigkeit. Für die rasche Abfuhr der Wärme in der Auffangzone sind insbesondere metallische Werkstoffe sehr gut geeignet, beispielsweise Stahlwolle oder Aluminiumspäne.The self-healing of the predetermined breaking point can be improved by arranging a collecting zone made of very good heat-conducting material that extends in the direction of the side wall of the outer steel trough directly outside the layer with low shear strength and the area of the carbon lining adjoining it below. This means that the heat given off by the electrolytes entering the crack can be dissipated more quickly, and self-healing through solidification takes place more quickly. The upper limit of this collecting zone is expediently at approximately the same level as the upper limit of the layer with low shear strength. However, the collecting zone is thicker than this layer, it is advantageously two to three times as thick as the layer with low shear strength. Metallic materials, such as steel wool or aluminum chips, are particularly well suited for the rapid dissipation of heat in the collecting zone.

Damit die Rissbildung stets im erwünschten Bereich erfolgt, ist die Scherfestigkeit der Schicht, welche die Kohlenstoffauskleidung in einen unteren und oberen Teil trennt, vorzugsweise mindestens fünfmal kleiner als diejenige von Kohlenstoff.So that the cracking always occurs in the desired area, the shear strength of the layer, which separates the carbon lining into a lower and an upper part, is preferably at least five times less than that of carbon.

Die Dicke dieser Schicht mit geringer Scherfestigkeit liegt in der Praxis zweckmässig zwischen 2 und 15 cm, vorzugsweise zwischen 5 und 10 cm.In practice, the thickness of this layer with low shear strength is expediently between 2 and 15 cm, preferably between 5 and 10 cm.

Die die Kohlenstoffauskleidung in zwei Teile trennende Schicht wird zweckmässig aus vorfabrizierten Blöcken aufgebaut. Die Materialien für diese Blöcke müssen die drei Anforderungen der Temperaturbeständigkeit, der Resistenz gegenüber dem Elektrolyten und der geringen Scherfestigkeit erfüllen. In der Praxis können für die Herstellung der Blöcke geschäumter Kohlenstoff, geschäumte keramische Materialien und komprimierte Kohlefaserschichten eingesetzt werden.The layer separating the carbon lining into two parts is expediently built up from prefabricated blocks. The materials for these blocks must meet the three requirements of temperature resistance, resistance to the electrolyte and low shear strength. In practice, foamed carbon, foamed ceramic materials and compressed carbon fiber layers can be used for the production of the blocks.

Die Schicht mit geringer Scherfestigkeit wird oben zweckmässig mit einem bekannten Kleber an die Kohlenstoffauskleidung geklebt und unten über einen Kohlenstoffilz auf die Kohlenstoffauskleidung gelegt. Der komprimierte Kohlenstoffilz ist vorzugsweise zwischen 5 und 15 mm dick und seinerseits an den unteren Teil der Kohlenstoffauskleidung geklebt.The layer with low shear strength is expediently glued to the carbon lining at the top with a known adhesive and placed on the carbon lining at the bottom via a carbon felt. The compressed carbon felt is preferably between 5 and 15 mm thick and in turn glued to the lower part of the carbon lining.

Soll der untere Teil der Kohlenstoffauskleidung weniger rasch aufquellen, so kann dieser untere Teil stärker graphitisiert werden.If the lower part of the carbon lining swells less quickly, this lower part can be graphitized more.

Weiter hat es sich als vorteilhaft erwiesen, im Bereich des Bodens der Kohlenstoffauskleidung plastisch verformbare Metallteile oder spröde poröse Materialien anzuordnen, welche bei einer Ausdehnung dieses Bodens einen nahezu konstanten Widerstand erzeugen. Die Angriffsfläche dieser sogenannten «Crunchelemente» liegt vorzugsweise oberhalb der Kernzone des Bodens der Kohlenstoffauskleidung. Damit wird die Ausbildung von Rissen und unzulässigen Deformationen verhindert. Der negative Einfluss von allfällig im Bereich des Bodens der Kohlenstoffauskleidung vorhandenen Rissen wird zweckmässig dadurch vermindert bzw. verhindert, dass die eingesetzten «Crunchelemente» mit bekannten Mitteln vorgespannt werden.Furthermore, it has proven to be advantageous to arrange plastically deformable metal parts or brittle porous materials in the region of the bottom of the carbon lining, which produce an almost constant resistance when this bottom is expanded. The attack surface of these so-called "crunch elements" is preferably above the core zone of the bottom of the carbon lining. This prevents the formation of cracks and impermissible deformations. The negative influence of any cracks present in the area of the bottom of the carbon lining is expediently reduced or prevented by the “crunch elements” used being prestressed using known means.

Als plastisch verformbare Metallteile werden zweckmässig hochgestellte Rohre bzw. Rohrpakete verwendet. Anstelle der hochgradig plastischen Metalle ist auch die Verwendung von relativ spröden Materialien mit unzähligen kleinsten Hohlräumen eine vorzugsweise Ausführungsform der «Crunchelemente». Beim Zermalmen eines solchen Materials brechen die von Auge kaum sichtbaren Materialbrücken eine nach der anderen ein, während die restlichen, noch intakten Zonen einen nahezu konstanten Widerstand gegen den sich ausdehnenden unteren Teil der Kohlenstoffauskleidung bieten.As a plastically deformable metal part, it is advisable to use superscript pipes or pipe packages. Instead of the highly plastic metals, the use of relatively brittle materials with innumerable smallest cavities is a preferred embodiment of the "crunch elements". When crushing such a material, the material bridges, which are barely visible to the eye, collapse one after the other, while the remaining, intact zones offer almost constant resistance to the expanding lower part of the carbon lining.

Die Erfindung wird anhand der Zeichnung näher erläutert. Es zeigen schematisch:

  • Fig. 1 eine aufgeschnittene perspektivische Darstellung des Seitenbereichs einer Schmelzflusselektrolysezelle zur Herstellung von Aluminium,
  • Fig. 2 einen Vertikalschnitt durch den Seitenbereich einer Schmelzflusselektrolysezelle zur Herstellung von Aluminium,
  • Fig. 3 einen teilweisen Vertikalschnitt im Bereich einer Schicht mit geringer Scherfestigkeit, nach dem ersten Reissen,
  • Fig. 4 einen Ausschnitt wie Fig. 3 nach dem x-ten Reissen, und
  • Fig. 5 einen Ausschnitt wie Fig. 3 und 4 nach dem Durchriss der Schicht mit geringer Scherfestigkeit.
The invention is explained in more detail with reference to the drawing. They show schematically:
  • 1 is a cutaway perspective view of the side area of a melt flow electrolysis cell for the production of aluminum,
  • 2 shows a vertical section through the side region of a melt flow electrolysis cell for producing aluminum,
  • 3 shows a partial vertical section in the region of a layer with low shear strength after the first cracking,
  • Fig. 4 shows a detail like Fig. 3 after the xth tear, and
  • Fig. 5 shows a detail like Fig. 3 and 4 after the tear of the layer with low shear strength.

Eine Schmelzflusselektrolysezelle zur Herstellung von Aluminium hat eine äussere Stahlwanne 10. Darin eingebettet ist die untere Isolation 12 und die seitliche Isolation 14. Auf der den Unterbau bildenden unteren Isolation 12 ist der untere Teil 16 der Kohlenstoffauskleidung mit eingegossenen bzw. eingebetteten, eisernen Kathodenbarren 18 angeordnet. Auf dem horizontal begrenzten Randbereich des unteren Teils 16 der Kohlenstoffauskleidung ist die etwa 8 cm dicke Schicht 20 mit geringer Scherfestigkeit angeordnet. Zwischen dieser Schicht 20 und dem unteren Teil 16 der Kohlenstoffauskleidung liegt - nicht sichtbar-eine Unterlage aus Kohlenstoffilz, welcher am unteren Teil 16 der Kohlenstoffauskleidung angeklebt ist.A melt flow electrolysis cell for the production of aluminum has an outer steel trough 10. The lower insulation 12 and the lateral insulation 14 are embedded therein. The lower insulation 12, which forms the substructure, is the lower one Part 16 of the carbon lining with cast or embedded, iron cathode bars 18 arranged. The approximately 8 cm thick layer 20 with low shear strength is arranged on the horizontally delimited edge region of the lower part 16 of the carbon lining. Between this layer 20 and the lower part 16 of the carbon lining there is a base (not visible) made of carbon felt, which is glued to the lower part 16 of the carbon lining.

Auf der Schicht 20 mit geringer Scherfestigkeit ist der obere Teil 22 der Kohlenstoffauskleidung angeklebt, er überragt den unteren Teil seitlich. Den obersten Bereich bilden Steinblöcke 24, womit ein isolierendes, gegen Sauerstoffeinwirkung schützendes Wannenbord gewährleistet ist.The upper part 22 of the carbon lining is glued to the layer 20 with low shear strength, it projects beyond the lower part laterally. The uppermost area is formed by stone blocks 24, which ensures an insulating tub shelf that protects against the effects of oxygen.

Innerhalb der Stahlwanne 10, auf der Höhe des oberen Bereichs des Bodens der Kohlenstoffauskleidung sind vorgespannte «Crunchelemente» 26 angeordnet, die von einer Ausbuchtung der Stahlwanne 10 gestütztwerden.Prestressed «crunch elements» 26 are arranged within the steel trough 10, at the level of the upper region of the bottom of the carbon lining, and are supported by a bulge in the steel trough 10.

Die «Crunchelemente» 26 setzen dem sich ausdehnenden unteren Teil 16 der Kohlenstoffauskleidung einen konstanten, wegunabhängigen Widerstand entgegen.The “crunch elements” 26 oppose the expanding lower part 16 of the carbon lining with a constant, path-independent resistance.

Zwischen der seitlichen Isolation 14 und dem oberen Teil 22 der Kohlenstoffauskleidung ist eine als Auffangzone 30 ausgestaltete, sehr gut wärmeleitende Schicht ausgebildet. Sie geht in vertikaler Richtung, nach unten, über die Schicht 20 mit geringer Scherfestigkeit hinaus und erstreckt sich teilweise entlang des unteren Teils 16 der Kohlenstoffauskleidung.Between the lateral insulation 14 and the upper part 22 of the carbon lining, a very good heat-conducting layer is designed as a collecting zone 30. It extends in the vertical direction, downward, beyond the layer 20 with low shear strength and extends partially along the lower part 16 of the carbon lining.

In Fig. 2 ist ein Teil des Seitenbereichs der Stahlwanne 10 durch eine flexible Wand 32 ersetzt. Dazu können beispielsweise Gewebe aus Kohlefasern, die in Schichtbauweise mit Metallfolien kombiniert sind, eingesetzt werden. Die ausserhalb der flexiblen Wand 32 angeordneten, vorgespannten «Crunchelemente» 26 bestehen, wie in Fig. 1, aus Paketen von plastisch verformbaren, vertikal angeordneten Rohren. Gegen aussen werden die «Crunchelemente» 26 von einem festen Widerlager 28 gestützt. Zwischen der flexiblen Wand 32 und der seitlichen Isolation kann eine Gleitschicht angeordnet werden.2, part of the side region of the steel tub 10 is replaced by a flexible wall 32. For example, fabrics made of carbon fibers, which are combined in a layered construction with metal foils, can be used. The prestressed “crunch elements” 26 arranged outside the flexible wall 32 consist, as in FIG. 1, of packages of plastically deformable, vertically arranged tubes. Towards the outside, the “crunch elements” 26 are supported by a fixed abutment 28. A sliding layer can be arranged between the flexible wall 32 and the lateral insulation.

Fig. 3 zeigt einen auf einem Kohlestoffilz 34 liegenden Kohleschaumblock 20 mit geringer Scherfestigkeit. Wegen unterschiedlicher Ausdehnung des unteren Teils 16 und des oberen Teils 22 der Kohlenstoffauskleidung ist die Schicht 20 mit geringer Scherfestigkeit ein erstes Mal gerissen, flüssiger Elektrolyt ist eingedrungen und teilweise erstarrt.Fig. 3 shows a block of carbon foam 20 lying on a carbon felt 34 with low shear strength. Because of the different expansion of the lower part 16 and the upper part 22 of the carbon lining, the layer 20 with low shear strength has cracked for the first time, liquid electrolyte has penetrated and partially solidified.

In der Darstellung nach Fig. 3 ist die Schicht 20 mit geringer Scherfestigkeit einmal, nach Fig. 4 bereits mehrmals gerissen. Der Kohlefilz 34 hat sich nach dem mehrmaligen Reissen teilweise aufgelöst und der erstarrte Elektrolyt 36 ist weiter nach aussen vorgedrungen.In the illustration according to FIG. 3, the layer 20 with low shear strength has been torn once, according to FIG. 4 several times. The carbon felt 34 has partially dissolved after the repeated tearing and the solidified electrolyte 36 has penetrated further outwards.

In Fig. 5 schliesslich ist der erstarrte Elektrolyt vollständig durch die Schicht 20 mit geringer Scherfestigkeit nach aussen durchgedrungen und in der Auffangzone 30 erstarrt.Finally, in FIG. 5, the solidified electrolyte has completely penetrated through the layer 20 with low shear strength and solidified in the collecting zone 30.

Der Fig. 3 bis 5 zeigen - anhand von Elektrolysezellen mit unterschiedlichen Dimensionierungen der einzelnen Bauteile - deutlich den selbstheilenden Effekt der Sollbruchstelle: Die den Schmelzflusselektrolyten und das abgeschiedene flüssige Aluminium enthaltende Wanne kann nur an einer Stelle, der Schicht 20 mit geringer Scherfestigkeit, reissen. In diesem Bereich befindet sich nur schmelzflüssiger Elektrolyt, kein Metall. Der durch Risse in dieser Schicht 20 austretende Elektrolyt erstarrt und obwohl er sich zunehmend nach aussen fortsetzt, wirkt er immer selbstheilend, indem das erstarrte Material das nachfliessende am weiteren Austreten hindert.3 to 5 show - based on electrolysis cells with different dimensions of the individual components - the self-healing effect of the predetermined breaking point: The trough containing the melt flow electrolyte and the separated liquid aluminum can tear only at one point, the layer 20 with low shear strength. There is only molten electrolyte in this area, no metal. The electrolyte escaping through cracks in this layer 20 solidifies and although it continues to extend outwards, it always has a self-healing effect in that the solidified material prevents the flowing material from escaping further.

Claims (10)

1. Cathode tank of a fusion electrolysis cell for the production of aluminium, consisting of an outer steel tank carried or supported by metal components, a thermal insulation coating and an electrically conductive internal lining of carbon which is stable to the molten aluminium and the electrolyte, characterised by a layer (20) of a material which is stable at temperatures up to 1,000°C, resistant to the electrolyte and of substantially lower shear strength than that of the carbon lining, which layer is arranged extending horizontally around exclusively in the region of the electrolyte and divides the carbon lining into a lower part (16) and an upper part (22).
2. Cathode tank according to Claim 1, characterised in that the shear strength of the layer (20) dividing the carbon linining is at least five times less than that of the carbon lining.
3. Cathode tank according to Claim 1 or 2, characterised in that the thickness of the layer (20) with low shear strength amounts to 2-15 cm, preferably 5-10 cm.
4. Cathode tank according to at least one of Claims 1-3, characterised in that the layer (20) with low shear strength consists of foamed carbon, carbon fibre layers or foamed ceramic material.
5. Cathode tank according to at least one of Claims 1-4, characterised in that the layer (20) with low shear strength is stuck with a known adhesive to the upper part (22) of the carbon lining and lies through a carbon felt (34) on the lower part (16) of the carbon lining.
6. Cathode tank according to Claim 5, characterised in that the compressed carbon felt (34) is 5-15 mm thick and is stuck with a known adhesive on to the lower part (16) of the carbon lining.
7. Cathode tank according to at least one of Claims 1-6, characterised in that immediately outside the layer (20) with low shear strength and partially the downwardly adjoining part (16) of the carbon lining there is arranged a collector zone (30) of material of very good thermal conductivity extending in the direction of the side wall of the outer steel tank (10), the height of this collector zone (30) preferably amounting to two to three times the thickness of the layer (20) with low shear strength.
8. Cathode tank according to Claim 7, characterised in that the collector zone (30) consists of steel wool or aluminium shavings.
9. Cathode tank according to at least one of Claims 1-8, characterised in that the lower part (16) of the carbon lining is more graphitized than its upper part (22).
10. Cathode tank according to at least one of Claims 1-9, characterised in that preferably initially stressed «crunch elements» (26) in the form of plastically deformable metal tubes or brittle porous materials which generate a nearly constant, distance-independent resistance are arranged in the region of the bottom of the lower part (16) of the carbon lining, preferably above its core zone.
EP83810282A 1982-07-12 1983-06-24 Aluminium electrolysis cell pot Expired EP0099331B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH4249/82A CH660030A5 (en) 1982-07-12 1982-07-12 CATHODE PAN OF AN ALUMINUM ELECTROLYSIS CELL.
CH4249/82 1982-07-12

Publications (2)

Publication Number Publication Date
EP0099331A1 EP0099331A1 (en) 1984-01-25
EP0099331B1 true EP0099331B1 (en) 1986-12-10

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EP83810282A Expired EP0099331B1 (en) 1982-07-12 1983-06-24 Aluminium electrolysis cell pot

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US (1) US4537671A (en)
EP (1) EP0099331B1 (en)
JP (1) JPS5923891A (en)
AU (1) AU1660983A (en)
CA (1) CA1215941A (en)
CH (1) CH660030A5 (en)
DE (1) DE3368292D1 (en)
NO (1) NO832497L (en)
NZ (1) NZ204762A (en)
SU (1) SU1308201A3 (en)
ZA (1) ZA834667B (en)

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Publication number Priority date Publication date Assignee Title
US4687566A (en) * 1985-03-06 1987-08-18 Swiss Aluminium Ltd. Protective collar for anode spade pin
NO157462C (en) * 1985-10-24 1988-03-23 Hydro Aluminium As LAMINATED CARBON CATHOD FOR CELLS-MELT-ELECTROLYTIC ALUMINUM PREPARATION.
US4900249A (en) * 1987-01-12 1990-02-13 Dresser Industries, Inc. Aluminum reverberatory furnace lining
JP2011508173A (en) * 2007-12-22 2011-03-10 ユンガー・プルス・グレーター・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツング・フォイアーフェストバウ Industrial furnace wall lining
DE102010041082A1 (en) * 2010-09-20 2012-03-22 Sgl Carbon Se Cathode for electrolysis cells
DE102010041081B4 (en) * 2010-09-20 2015-10-29 Sgl Carbon Se Cathode for electrolysis cells
ITVE20110026A1 (en) * 2011-05-05 2012-11-06 Tito Monticelli LATENT CANALIZATION FOR ELECTROLYTIC OVEN FOR THE PRODUCTION OF AL. FROM AL2O3 + NA3ALF3. THE INVENTION CONCERNS THE REALIZATION IN THE CATHODIC PART OF A STANDARD BATH / OVEN DEFENSE FROM THE DAMAGE CAUSED BY FIRST CORROSION, AND BY INFILT

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Publication number Priority date Publication date Assignee Title
DE1608030A1 (en) * 1967-02-01 1970-10-29 Montedison Spa Lining for electrolysis, remelting and similar furnaces that contain molten metals alone or together with molten salts
GB1209541A (en) * 1967-02-01 1970-10-21 Montedison Spa Electrolytic furnaces for the production of aluminium
CH606496A5 (en) * 1976-06-16 1978-10-31 Alusuisse
CH643602A5 (en) * 1979-10-17 1984-06-15 Alusuisse ELECTROLYSIS PAN.
US4339316A (en) * 1980-09-22 1982-07-13 Aluminum Company Of America Intermediate layer for seating RHM tubes in cathode blocks

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AU1660983A (en) 1984-01-19
EP0099331A1 (en) 1984-01-25
US4537671A (en) 1985-08-27
DE3368292D1 (en) 1987-01-22
JPS5923891A (en) 1984-02-07
NZ204762A (en) 1986-05-09
SU1308201A3 (en) 1987-04-30
ZA834667B (en) 1984-03-28
NO832497L (en) 1984-01-13
CH660030A5 (en) 1987-03-13
CA1215941A (en) 1986-12-30

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