EP1499757A2 - Method for the production of cathode blocks - Google Patents

Method for the production of cathode blocks

Info

Publication number
EP1499757A2
EP1499757A2 EP02787958A EP02787958A EP1499757A2 EP 1499757 A2 EP1499757 A2 EP 1499757A2 EP 02787958 A EP02787958 A EP 02787958A EP 02787958 A EP02787958 A EP 02787958A EP 1499757 A2 EP1499757 A2 EP 1499757A2
Authority
EP
European Patent Office
Prior art keywords
cathode
block
cross
graphitization
graphitized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP02787958A
Other languages
German (de)
French (fr)
Other versions
EP1499757B1 (en
Inventor
Johann Daimer
Frank Hiltmann
Jörg MITTAG
Philippe Beghein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SGL Carbon SE
Original Assignee
SGL Carbon SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SGL Carbon SE filed Critical SGL Carbon SE
Publication of EP1499757A2 publication Critical patent/EP1499757A2/en
Application granted granted Critical
Publication of EP1499757B1 publication Critical patent/EP1499757B1/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes

Definitions

  • the invention relates to a method for producing cathode blocks, in particular for the electrolytic production of aluminum.
  • electrolysis cells which comprise a base composed of a plurality of blocks, which acts as a cathode.
  • the electrolyte is a melt, essentially a solution of aluminum oxide in K-t-yolite.
  • the working temperature is around 1000 ° C, for example.
  • the electrolytically deposited molten aluminum collects on the bottom of the cell under a layer of the electrolyte.
  • Around the cells is a metallic housing (preferably steel) with a lining made of high temperature resistant material.
  • the material of the cathode blocks is preferably carbon because of the required chemical and thermal resistance, which can be partially or completely graphitized by thermal treatment.
  • mixtures of pitches, cokes, anthracite and / or graphite in selected particle sizes or particle size distributions for the solids are mixed, shaped and fired and optionally (partially) graphitized.
  • the firing (carbonization) usually takes place at temperatures of approx. 1200 ° C, the graphitization usually at temperatures of approx. 2400 ° C.
  • While graphitized cathodes are preferred because of their higher electrical conductivity, they show greater wear during operation, corresponding to an average annual decrease in their thickness of up to 80 mm. This wear is not evenly distributed over the length of the cathode blocks (corresponding to the width of the cell), but changes the surface of the cathode blocks into a W-shaped profile. Due to the uneven removal, the service life of the cathode blocks is limited by the places with the greatest removal.
  • One way to equalize the removal over the length of the cathode block and thus to extend the service life is to design the cathode blocks so that their electrical resistance varies over the length such that the current density (and thus the Wear) is uniform over its length or at least exhibits the smallest possible deviation over the length from its mean value.
  • a solution is described in DE 20 61 263, in which composite cathodes are formed either from several carbon blocks with different electrical conductivity, which are arranged in such a way that a uniform or approximately uniform current distribution results, or from carbon blocks, the electrical resistances of which are in the direction of the cathodic Derivatives increase continuously.
  • the number of carbon blocks and their electrical resistance depend on the cell size and cell p, they must be recalculated for each case.
  • Cathode blocks made of a large number of individual carbon blocks require a great deal of effort in the construction; the joints must also be properly sealed to prevent the liquid aluminum from flowing out at the joints.
  • WO 00/46426 describes a graphite cathode which consists of a single block which has an electrical conductivity which is variable over its length, the conductivity at the ends of the block being lower than in the middle.
  • This uneven distribution of electrical conductivity is achieved by bringing the end zones to a temperature of 2200 to 2500 ° C. during the graphitization, while exposing the middle zone to a temperature of 2700 to 3000 ° C.
  • This different heat treatment can be achieved according to this teaching in two ways: first, the heat dissipation in the graphitization furnace can be limited differently, or heat sinks can be introduced in the vicinity of the end zones, which increase the heat loss.
  • the density of the heat-insulating bed is changed so that the heat loss becomes uneven over the length of the cathodes and the desired temperatures are thus set.
  • the heat loss in the vicinity of the ends can be increased by different designs of the heat-insulating bed, or for this purpose heat-dissipating bodies made of graphite are preferably introduced in their vicinity, which cause a greater heat flow to the outside of the furnace wall.
  • the difference in the heat treatment can take place by locally changing the current density, with the result of different heat development.
  • this change in the current density can take place through different resistances of the conductive bed between two cathodes in an Acheson furnace (cross-graphitization). No solution of this type is specified for a longitudinal graphing method.
  • this object has been achieved by increasing the temperature during the graphitization in the central zone compared to the temperature in the end zones by generating a greater Joule heat in the central zone.
  • the invention therefore relates to a method for producing graphitized cathode blocks which can be used for the electrolytic extraction of aluminum, characterized in that a carbonized cathode block is used in a longitudinal graphitization process, the cross section of which is larger at the ends of the block than in the middle, and in that at least part of the graphitized material is removed at the ends after the graphitization.
  • Fig. 1 is a side view of a cathode block which is tapered in the middle
  • Fig. 2 shows a cathode block with a stepped profile.
  • the cathode block 4 has a cross section which corresponds to two symmetrical trapezoids lying one against the other with an additional rectangle on each of the base sides.
  • the corresponding spatial embodiment can correspond to two truncated pyramids with rectangular base plates or preferably two truncated cones with circular disk-shaped base plates lying one on top of the other with the smaller top surface. The latter form can be produced, for example, simply by twisting off a cylindrical blank.
  • FIG. 2 shows a cathode block with a step-shaped profile, the cross section of the volume elements (circular disks or cuboids) 4 1 to 4 6 lying on top of one another steadily decreasing towards the center.
  • the current required to generate the Joule heat for the graphitization is supplied via lines 1.
  • the electrical resistance is inversely proportional to the cross-sectional area of the individual volume elements.
  • the graphitized material at the ends can easily be removed after removal of the finished graphitized cathodes from the furnace and cooling by mechanical processing, in particular milling.
  • the cathode block consists of at least three zones, the two outer zones preferably having the same cross section.
  • the course of the electrical conductivity after the graphitization essentially follows this profile, with a maximum in the middle.
  • the cross section of the carbonized cathode block increases continuously from the center to the ends of the carhode block, and thus the electrical conductivity also has a continuous course.
  • An embodiment is particularly preferred in which the cross section at the ends of the cathode block is at least 10% larger than that in the middle.
  • the graphitized cathode blocks can be used in the production of aluminum by electrolytic reduction of aluminum oxide in a bath of molten cryolite, and in this way result in an extended service life in comparison with the cathode blocks with homogeneous conductivity.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)

Abstract

Disclosed is a method for producing graphitized cathode blocks. A carbonized cathode block is used in a longitudinal graphitization method, the cross section of said block being larger at the ends of the block than in the middle thereof. At least part of the graphitized material is removed from the ends upon graphitization. Also disclosed are cathode blocks produced according to the inventive method and the use thereof for the electrolytic production of aluminum.

Description

Nerfahten zur Herstellung von KathodenblöckenNerfahten for the production of cathode blocks
Die Erfindung betrifft ein Verfahren zur Herstellung von Kathodenblöcken insbesondere für die elektrolytische Herstellung von Aluminium.The invention relates to a method for producing cathode blocks, in particular for the electrolytic production of aluminum.
Bei der elektrolytischen Herstellung von Alum-i-t-ύum nach dem Hall-Heroult-Nerfahren werden Elektrolysezellen eingesetzt, die einen aus einer Vielzahl von Blöcken zusammengesetzten Boden umfassen, der als Kathode wirkt. Der Elektrolyt ist eine Schmelze, im wesentlichen eine Lösung von Aluminiumoxid in K-t-yolith. Die Arbeitstemperatur liegt beispielsweise bei ca. 1000 °C. Das elektrolytisch abgeschiedene geschmolzene Aluminium sammelt sich auf dem Boden der Zelle unter einer Schicht des Elektrolyten. Um die Zellen ist ein metallisches Gehäuse (bevorzugt Stahl) mit einer Auskleidung aus hochtemperaturbeständigem Material.In the electrolytic production of alum-i-t-um according to the Hall-Heroult-Ner method, electrolysis cells are used which comprise a base composed of a plurality of blocks, which acts as a cathode. The electrolyte is a melt, essentially a solution of aluminum oxide in K-t-yolite. The working temperature is around 1000 ° C, for example. The electrolytically deposited molten aluminum collects on the bottom of the cell under a layer of the electrolyte. Around the cells is a metallic housing (preferably steel) with a lining made of high temperature resistant material.
Das Material der Kathodenblöcke ist wegen der erforderlichen chemischen und thermischen Beständigkeit bevorzugt Kohlenstoff, der durch thermische Behandlung teilweise oder vollständig graphitiert sein kann. Zur Herstellung solcher Kathodenblöcke werden Mischungen von Pechen, Koksen, Anthrazit und/oder Graphit in ausgewählten Teilchengrößen bzw. Teilchengrößenverteilungen für die Feststoffe gemischt, geformt und gebrannt und gegebenenfalls (teilweise) graphitiert. Das Brennen (Carbonisierung) erfolgt üblicherweise bei Temperaturen von ca. 1200 °C, die Graphitierung üblicherweise bei Temperaturen von über ca. 2400 °C.The material of the cathode blocks is preferably carbon because of the required chemical and thermal resistance, which can be partially or completely graphitized by thermal treatment. To produce such cathode blocks, mixtures of pitches, cokes, anthracite and / or graphite in selected particle sizes or particle size distributions for the solids are mixed, shaped and fired and optionally (partially) graphitized. The firing (carbonization) usually takes place at temperatures of approx. 1200 ° C, the graphitization usually at temperatures of approx. 2400 ° C.
Während graphitierte Kathoden wegen ihrer höheren elektrischen Leitfähigkeit bevorzugt werden, zeigen sie eine stärkere Abnutzung während des Betriebs, entsprechend einer mittleren jährlichen Abnahme ihrer Dicke von bis zu 80 mm. Diese Abnutzung ist nicht gleichmäßig über die Länge der Kathodenblöcke (entsprechend der Breite der Zelle) verteilt, sondern verändert die Oberfläche der Kathodenblöcke zu einem W-förmigen Profil. Durch den ungleichmäßigen Abtrag wird die Nutzungsdauer der Kathodenblöcke begrenzt durch die Stellen mit dem größten Abtrag.While graphitized cathodes are preferred because of their higher electrical conductivity, they show greater wear during operation, corresponding to an average annual decrease in their thickness of up to 80 mm. This wear is not evenly distributed over the length of the cathode blocks (corresponding to the width of the cell), but changes the surface of the cathode blocks into a W-shaped profile. Due to the uneven removal, the service life of the cathode blocks is limited by the places with the greatest removal.
Eine Möglichkeit, den Abtrag über die Länge des Kathodenblocks zu vergleichmäßigen und damit die Nutzungsdauer zu verlängern, besteht darin, die Kathodenblöcke so auszuführen, daß ihr elektrischer Widerstand über die Länge variiert, derart daß die Stromdichte (und damit die Abnutzung) über ihre Länge gleichmäßig ist oder zumindest eine möglichst geringe Abweichung über die Länge von ihrem Mittelwert aufweist.One way to equalize the removal over the length of the cathode block and thus to extend the service life is to design the cathode blocks so that their electrical resistance varies over the length such that the current density (and thus the Wear) is uniform over its length or at least exhibits the smallest possible deviation over the length from its mean value.
Eine Lösung ist in DE 20 61 263 beschrieben, wobei zusammengesetzte Kathoden gebildet werden entweder aus mehreren Kohlenstoffblöcken mit unterschiedlicher elektrischer Leitfähigkeit, die so angeordnet werden, daß sich eine gleichmäßige oder annähernd gleichmäßige Stromverteilung ergibt, oder aus Kohlenstoffblöcken, deren elektrische Widerstände in Richtung der kathodischen Ableitungen kontinuierlich zunehmen. Die Anzahl der Kohlenstoffblöcke und deren elektrischer Widerstand richten sich jeweils nach Zellengröße und Zellent p, sie müssen für jeden Fall neu errechnet werden. Kathodenblöcke aus einer Vielzahl von einzelnen Kohlenstoff-Blöcken erfordern einen hohen Aufwand bei der Konstruktion; auch müssen die Stoßstellen jeweils gut abgedichtet werden, um ein Ausfließen des flüssigen Aluminiums an den Stoßstellen zu vermeiden.A solution is described in DE 20 61 263, in which composite cathodes are formed either from several carbon blocks with different electrical conductivity, which are arranged in such a way that a uniform or approximately uniform current distribution results, or from carbon blocks, the electrical resistances of which are in the direction of the cathodic Derivatives increase continuously. The number of carbon blocks and their electrical resistance depend on the cell size and cell p, they must be recalculated for each case. Cathode blocks made of a large number of individual carbon blocks require a great deal of effort in the construction; the joints must also be properly sealed to prevent the liquid aluminum from flowing out at the joints.
In der WO 00/46426 ist eine Graphitkathode beschrieben worden, die aus einem einzelnen Block besteht, der eine über seine Länge veränderliche elektrische Leitfähigkeit aufweist, wobei die Leitfähigkeit an den Enden des Blocks niedriger ist als in der Mitte. Diese ungleichmäßige Verteilung der elektrischen Leitfähigkeit wird erreicht, indem während der Graphitierung die Endzonen auf eine Temperatur von 2200 bis 2500 °C gebracht werden, während die mittlere Zone einer Temperatur von 2700 bis 3000 °C ausgesetzt wird. Diese unterschiedliche Wärmebehandlung kann gemäß dieser Lehre durch zwei Weisen erreicht werden: einmal kann die Wärmeableitung im Graphitierungsofen unterschiedlich begrenzt werden, oder es können Wärmesenken in der Nachbarschaft der Endzonen eingebracht werden, die den Wärmeverlust erhöhen. Bei einer Quergraphitierung wird dabei die Dichte der wärmeisolierenden Schüttung so verändert, daß der Wärmeverlust über die Länge der Kathoden ungleichmäßig wird und damit die gewünschten Temperaturen eingestellt werden. Auch bei der Längsgraphitierung kann durch unterschiedliche Ausführung der wärmeisolierenden Schüttung der Wärmeverlust in der Nähe der Enden vergrößert werden, oder es werden zu diesem Zweck wärmeableitende Körper bevorzugt aus Graphit in deren Nähe eingebracht, die einen stärkeren Wärmeabfluß nach außen zur Ofenwand hin bewirken.WO 00/46426 describes a graphite cathode which consists of a single block which has an electrical conductivity which is variable over its length, the conductivity at the ends of the block being lower than in the middle. This uneven distribution of electrical conductivity is achieved by bringing the end zones to a temperature of 2200 to 2500 ° C. during the graphitization, while exposing the middle zone to a temperature of 2700 to 3000 ° C. This different heat treatment can be achieved according to this teaching in two ways: first, the heat dissipation in the graphitization furnace can be limited differently, or heat sinks can be introduced in the vicinity of the end zones, which increase the heat loss. In the case of cross-graphitization, the density of the heat-insulating bed is changed so that the heat loss becomes uneven over the length of the cathodes and the desired temperatures are thus set. Also in longitudinal graphitization, the heat loss in the vicinity of the ends can be increased by different designs of the heat-insulating bed, or for this purpose heat-dissipating bodies made of graphite are preferably introduced in their vicinity, which cause a greater heat flow to the outside of the furnace wall.
Gemäß einer anderen Methode kann der Unterschied der Wärmebehandlung durch lokale Veränderung der Stromdichte erfolgen, mit der Folge unterschiedlicher- Wärmeentwicklung. Diese Veränderung der Stromdichte kann gemäß der Lehre durch unterschiedliche Widerstände der leitenden Schüt ung zwischen zwei Kathoden in einem Acheson-Ofen (Quergraphitierung) erfolgen, für ein Längsgraphiüerungsverfahren ist kein derartige Lösung angegeben.According to another method, the difference in the heat treatment can take place by locally changing the current density, with the result of different heat development. According to the teaching, this change in the current density can take place through different resistances of the conductive bed between two cathodes in an Acheson furnace (cross-graphitization). No solution of this type is specified for a longitudinal graphing method.
Diese bekannten Methoden weisen für die Praxis erhebliche Nachteile auf. Ein Unterschied von 500 °C für die gewünschten Graphitierungstemperaturen in der Mitte und an den Enden der Kathoden ist durch Wärmesenken allein nicht erreichbar. Unterschiedliche Wärmeableitung nach außen in dem erforderlichen Maße bringt einen erheblichen Energieverlust, der die Fertigung wesentlich verteuert. Der höhere Wärmeverlust nach der Seite des Ofens bedeutet auch eine höhere thermische Beanspruchung, die die Konstruktion des Ofens verteuert oder seine Lebensdauer vermindert. Schließlich ist eine Inhomogenität der wärmeisolierenden bzw. der leitenden Schüttung wenig praktikabel, da das Schüttungsmaterial zur Bef llung in mehreren Schritten eingebracht werden müßte und nach dem Abschluß des Ofenzyklus und dem Entfernen der Kathoden wieder entsprechend seiner Wärmeleitung bzw. elektrischen Leitfähigkeit Massiert werden müßte.These known methods have considerable disadvantages in practice. A difference of 500 ° C for the desired graphitization temperatures in the middle and at the ends of the cathodes cannot be achieved by heat sinks alone. Different heat dissipation to the outside to the required extent results in a considerable loss of energy, which makes production much more expensive. The higher heat loss to the side of the furnace also means a higher thermal stress, which makes the construction of the furnace more expensive or reduces its service life. Finally, an inhomogeneity of the heat-insulating or the conductive fill is not very practical, since the fill material would have to be introduced in several steps for filling and after the furnace cycle had been completed and the cathodes had been removed, it would have to be massaged again in accordance with its heat conduction or electrical conductivity.
Es ist daher die Aufgabe der vorliegenden Erfindung, ein praktikables Verfahren zur Verfügung zu stellen, um Kathoden herzustellen, die über ihre Länge eine unterschiedliche elektrische Leitfähigkeit aufweisen.It is therefore the object of the present invention to provide a practicable method for producing cathodes which have a different electrical conductivity over their length.
Erfindungsgemäß wurde diese Aufgabe gelöst, indem die Temperatur bei der Graphitierung in der mittleren Zone gegenüber der Temperatur in den Endzonen dadurch erhöht wurde, daß in der mitderen Zone eine größere Joule'sche Wärme erzeugt wurde.According to the invention, this object has been achieved by increasing the temperature during the graphitization in the central zone compared to the temperature in the end zones by generating a greater Joule heat in the central zone.
Bei den Arbeiten, die zu der vorliegenden Erfindung geführt haben, wurde nämlich gefunden, daß durch die Einführung ■ einer Wärmesenke der spezifische Energieverbrauch erhöht, also schlechter wird. Es ist jedoch anzustreben, ohne Erhöhung des Energieverbrauchs Kathoden mit den gewünschten Eigenschaften herzustellen. Die Joule'sche Wärme, die in einem durch einen elektrischen Strom durchflossenen Körper erzeugt wird, ist zu dessen elektrischem Widerstand und dem Quadrat der Stromstärke proportional. Bei der Längsgraphiüerung fließt durch jeweils eine Kathode ein konstanter Strom. In einer Zone mit höherem Widerstand wird daher bei vorgegebener Stromstärke mehr Wärme erzeugt. Die Erfindung betrifft daher ein Verfahren zur Herstellung von graphitierten Kathodenblöcken, die zur elektrolytischen Gewinnung von Aluminium einsetzbar sind, dadurch gekennzeichnet, daß in einem Längsgraphitierungsverfahren ein carbonisierter Kathodenblock eingesetzt wird, dessen Querschnitt an den Enden des Blocks größer ist als in der Mitte, und daß zumindest ein Teil des graphitierten Materials an den Enden nach der Graphitierung entfernt wird.In the work that led to the present invention, it was found that the introduction of a heat sink increases the specific energy consumption, that is to say it worsens. However, it is desirable to produce cathodes with the desired properties without increasing the energy consumption. The Joule heat generated in a body through which an electric current flows is proportional to its electrical resistance and the square of the current. In longitudinal graphing, a constant current flows through one cathode. In a zone with higher resistance, more heat is therefore generated at a given current. The invention therefore relates to a method for producing graphitized cathode blocks which can be used for the electrolytic extraction of aluminum, characterized in that a carbonized cathode block is used in a longitudinal graphitization process, the cross section of which is larger at the ends of the block than in the middle, and in that at least part of the graphitized material is removed at the ends after the graphitization.
Die Erfindung wird durch die Zeichnungen weiter erläutert. Dabei zeigenThe invention is further illustrated by the drawings. Show
Fig. 1 eine Seitenansicht eines Kathodenblocks, der in der Mitte verjüngt ist, undFig. 1 is a side view of a cathode block which is tapered in the middle, and
Fig. 2 ein Kathodenblock mit einem stufenförmigen Profil.Fig. 2 shows a cathode block with a stepped profile.
In der Fig. 1 ist ein Kathodenblock 4 dargestellt, der im Sinne einer Längsgraphitierung durch einen Gleichstrom elektrisch beheizt wird. Der Strom wird aus der Stromquelle durch die Leitungen 1 zugeführt. Der Einfachheit halber ist lediglich ein einziger Block in der Seitenansicht dargestellt, wobei andere Details weggelassen wurden. Der Kathodenblock 4 hat einen Querschnitt, der zwei mit den Schmalseiten aneinanderliegenden symmetrischen Trapezen entspricht, mit einem zusätzlichen Rechteck an jeder der Grundseiten. Die entsprechende räumliche Ausführungsform kann zwei Pyramidenstümpfen mit quaderförmigen Grundplatten oder bevorzugt zwei mit der kleineren Deckfläche aufeinanderliegenden Kegelstümpfen mit Kreisscheiben-förmigen Grundplatten entsprechen. Die letztere Form ist beispielsweise einfach durch Abdrehen eines zylinderförmigen Rohlings herzustellen.1 shows a cathode block 4 which is electrically heated in the sense of longitudinal graphitization by a direct current. The current is supplied from the current source through lines 1. For the sake of simplicity, only a single block is shown in side view, with other details omitted. The cathode block 4 has a cross section which corresponds to two symmetrical trapezoids lying one against the other with an additional rectangle on each of the base sides. The corresponding spatial embodiment can correspond to two truncated pyramids with rectangular base plates or preferably two truncated cones with circular disk-shaped base plates lying one on top of the other with the smaller top surface. The latter form can be produced, for example, simply by twisting off a cylindrical blank.
In der Fig. 2 ist ein Kathodenblock mit einen stufenförmigen Profil dargestellt, wobei der Querschnitt der aufeinanderliegenden Volumenelemente (Kreisscheiben oder Quader) 41 bis 46 zur Mitte hin stetig abn-Lmmt. Der zur Erzeugung der Joule'schen Wärme für die Graphitierung benötigte Strom wird über die Leitungen 1 zugeführt.2 shows a cathode block with a step-shaped profile, the cross section of the volume elements (circular disks or cuboids) 4 1 to 4 6 lying on top of one another steadily decreasing towards the center. The current required to generate the Joule heat for the graphitization is supplied via lines 1.
Bei homogener Materialzusammensetzung der carbonisierten Kathoden ist der elektrische Widerstand umgekehrt proportional zu der Querschnittsfläche der einzelnen Volumenelemente. Durch geeignete Wahl der Anzahl, der Länge und Querschnitte der aufeinanderfolgenden Volumenelemente kann die in diesem Volumenelementen entwickelte Joule'sche Wärme und damit die Temperatur bei der Graphitierung dem gewünschten Verlauf der elektrischen Leitfähigkeit in der Kathode genau angepaßt werden.With a homogeneous material composition of the carbonized cathodes, the electrical resistance is inversely proportional to the cross-sectional area of the individual volume elements. By suitable selection of the number, the length and the cross sections of the successive volume elements, the Joule heat and so that the temperature during the graphitization can be precisely adapted to the desired profile of the electrical conductivity in the cathode.
Das graphitierte Material an den Enden kann ohne weiteres nach Entnahme der fertigen graphitierten Kathoden aus dem Ofen und Abkühlen durch mechanische Bearbeitung, insbesondere Abfräsen, entfernt werden.The graphitized material at the ends can easily be removed after removal of the finished graphitized cathodes from the furnace and cooling by mechanical processing, in particular milling.
Gemäß der Erfindung ist es möglich, den carbonisierten Kathodenblock stufenweise entsprechend der in Fig. 2 dargestellten Form auszuführen. Dabei besteht der Kathodenblock aus mindestens drei Zonen, wobei die beiden äußeren Zonen bevorzugt denselben Querschnitt aufweisen. Der Verlauf der elektrischen Leitfähigkeit nach der Graphitierung folgt im wesentlichen diesem Profil, mit einem Maximum in der Mitte. Es ist jedoch bevorzugt, daß der Querschnitt des carbonisierten Kathodenblocks von der Mitte zu den Enden des Karhodenblocks hin kontinuierlich zunim-mt, und damit die elektrische Leitfähigkeit ebenfalls einen kontinuierlichen Verlauf aufweist.According to the invention, it is possible to carry out the carbonized cathode block stepwise according to the shape shown in FIG. 2. The cathode block consists of at least three zones, the two outer zones preferably having the same cross section. The course of the electrical conductivity after the graphitization essentially follows this profile, with a maximum in the middle. However, it is preferred that the cross section of the carbonized cathode block increases continuously from the center to the ends of the carhode block, and thus the electrical conductivity also has a continuous course.
Besonders bevorzugt ist dabei eine Ausführungsform, bei der der Querschnitt an den Enden des Kathodenblocks um mindestens 10 % größer als der in der Mitte ist.An embodiment is particularly preferred in which the cross section at the ends of the cathode block is at least 10% larger than that in the middle.
Die graphitierten Kathodenblöcke lassen sich bei der Herstellung von Aluminium durch elektrolytische Reduktion von Alu iniumoxid in einem Bad von geschmolzenem Kryolith einsetzen und ergeben dabei im Vergleich zu den Kathodenblöcken mit homogener Leitfähigkeit eine verlängerte Lebensdauer. The graphitized cathode blocks can be used in the production of aluminum by electrolytic reduction of aluminum oxide in a bath of molten cryolite, and in this way result in an extended service life in comparison with the cathode blocks with homogeneous conductivity.

Claims

Patentansprüche claims
1. Verfahren zur Herstellung von graphitierten Kathodenblöcken, die zur elektrolytischen Gewinnung von Aluminium einsetzbar sind, dadurch gekennzeichnet, daß in einem Längs- graphitierungsverfahren ein carbonisierter Kathodenblock eingesetzt wird, dessen Querschnitt an den Enden des Blocks größer ist als in der Mitte, und daß zumindest ein Teil des graphitierten Materials an den Enden nach der Graphitierung entfernt wird.1. A method for producing graphitized cathode blocks which can be used for the electrolytic extraction of aluminum, characterized in that a carbonized cathode block is used in a longitudinal graphitization process, the cross section of which is larger at the ends of the block than in the middle, and that at least part of the graphitized material is removed at the ends after graphitization.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Querschnitt des carbonisierten Kathodenblocks stufenweise in mindestens je einer Stufe zum Ende des Kathodenblocks hin zunimmt.2. The method according to claim 1, characterized in that the cross section of the carbonized cathode block gradually increases in at least one step towards the end of the cathode block.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Querschnitt des carbonisierten Kathodenblocks zu den Enden des Kathodenblocks hin kontinuierlich zunimmt. -3. The method according to claim 1, characterized in that the cross section of the carbonized cathode block increases continuously towards the ends of the cathode block. -
4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Querschnitt an den Enden des Kathodenblocks um mindestens 10 % größer als der in der Mitte ist.4. The method according to claim 1, characterized in that the cross section at the ends of the cathode block is at least 10% larger than that in the middle.
5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das graphitierte Material an den Enden durch mechanische Bearbeitung entfernt wird.5. The method according to claim 1, characterized in that the graphitized material is removed at the ends by mechanical processing.
6. Graphitierte Kathodenblöcke zur Herstellung von Aluminium durch elektrolytische Reduktion von Aluminiumoxid in einem Bad von geschmolzenem Kryolith, hergestellt nach dem Verfahren eines oder mehrerer der vorangehenden Ansprüche. 6. Graphitized cathode blocks for the production of aluminum by electrolytic reduction of aluminum oxide in a bath of molten cryolite, produced by the method of one or more of the preceding claims.
EP02787958A 2001-12-28 2002-12-19 Method for the production of cathode blocks Expired - Fee Related EP1499757B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2001164009 DE10164009B4 (en) 2001-12-28 2001-12-28 Process for the preparation of cathode blocks
DE10164009 2001-12-28
PCT/EP2002/014547 WO2003056067A2 (en) 2001-12-28 2002-12-19 Method for the production of cathode blocks

Publications (2)

Publication Number Publication Date
EP1499757A2 true EP1499757A2 (en) 2005-01-26
EP1499757B1 EP1499757B1 (en) 2008-10-15

Family

ID=7710903

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02787958A Expired - Fee Related EP1499757B1 (en) 2001-12-28 2002-12-19 Method for the production of cathode blocks

Country Status (8)

Country Link
EP (1) EP1499757B1 (en)
AR (1) AR037913A1 (en)
AU (1) AU2002352257A1 (en)
BR (1) BR0215325A (en)
CA (1) CA2470742A1 (en)
DE (2) DE10164009B4 (en)
PL (1) PL201883B1 (en)
WO (1) WO2003056067A2 (en)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2789091B1 (en) * 1999-02-02 2001-03-09 Carbone Savoie GRAPHITE CATHODE FOR ALUMINUM ELECTROLYSIS
US20020000373A1 (en) * 2000-05-22 2002-01-03 Hirofumi Ninomiya Graphitized cathode block for aluminum smelting
JP2002266091A (en) * 2001-03-09 2002-09-18 Sec Corp Graphit cathode block for smelting aluminum

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03056067A3 *

Also Published As

Publication number Publication date
DE50212919D1 (en) 2008-11-27
AU2002352257A1 (en) 2003-07-15
BR0215325A (en) 2005-08-30
WO2003056067A3 (en) 2004-11-11
AR037913A1 (en) 2004-12-22
AU2002352257A8 (en) 2003-07-15
PL373314A1 (en) 2005-08-22
WO2003056067A2 (en) 2003-07-10
DE10164009B4 (en) 2005-04-07
PL201883B1 (en) 2009-05-29
DE10164009A1 (en) 2003-08-07
CA2470742A1 (en) 2003-07-10
EP1499757B1 (en) 2008-10-15

Similar Documents

Publication Publication Date Title
DE2838965C2 (en) Wettable cathode for a molten electrolysis furnace
WO2004059039A1 (en) Cathode systems for electrolytically obtaining aluminium
DE60010861T2 (en) GRAPHITE CATHODE FOR ALUMINUM ELECTROLYSIS
DE3601014C2 (en) Method and device for the continuous strand graphitization of shaped carbon bodies
DE2850469A1 (en) ELECTROLYSIS REDUCTION CELL
EP1499757B1 (en) Method for the production of cathode blocks
EP3472373A1 (en) Cathode block having a slot geometry
DE10164013C1 (en) Longitudinal graphitization of cathode blocks for electrolytic production of aluminum comprises arranging blocks with gap between their ends, conductive moldings being placed between blocks
EP1463692B1 (en) Method for the production of cathode blocks
EP1461298B1 (en) Method for continuous graphitization
DE2032112A1 (en) Multi-cell furnace for the production of aluminum by electrolysis
EP1461477B1 (en) Method for graphitizing cathode blocks
EP1481115B1 (en) Graphitized cathode blocks
DE10164011C1 (en) Process, for graphitizing cathode blocks, involves arranging the blocks in a longitudinal graphitizing furnace, maintaining the a lowest possible distance between the surfaces of the blocks, and passing a current between the blocks
DE3003922C2 (en) Anode made of dimensionally stable oxide-ceramic individual elements
DE898817C (en) Furnace for direct fused aluminum electrolysis
EP0073735B1 (en) Electrolytic pot for the production of aluminium by electrolysis in the dry way, and method of inserting the iron bars
DE2833381A1 (en) Electrolysis cell for winning aluminium - where carbon cathode hearth is connected to bus=bars via spaced graphite pegs increasing the efficiency of aluminium prodn.
WO2012107403A1 (en) Cathode assembly comprising a surface-profiled cathode block having variable groove depth
CH663624A5 (en) Cathode element of a cathode vessel for producing aluminium
DE102016226122A1 (en) Novel cathode block
DE1172433B (en) Electrolysis cell for the production of aluminum
CH557885A (en) Electrolytic furnace for aluminium prodn
DE102011078002A1 (en) Annular electrolytic cell and annular cathode with magnetic field compensation
CH670658A5 (en) Cathode bars for aluminium prodn. cell - have cross=section reductions near active part of carbon hearth

Legal Events

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

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR IE IT LI LU MC NL PT SE SI SK TR

17P Request for examination filed

Effective date: 20050511

17Q First examination report despatched

Effective date: 20071109

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

Free format text: NOT ENGLISH

REF Corresponds to:

Ref document number: 50212919

Country of ref document: DE

Date of ref document: 20081127

Kind code of ref document: P

RAP2 Party data changed (patent owner data changed or rights of a patent transferred)

Owner name: SGL CARBON SE

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

Ref country code: DE

Payment date: 20090223

Year of fee payment: 7

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

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

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

26N No opposition filed

Effective date: 20090716

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

Effective date: 20090115

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

Ref country code: FR

Payment date: 20090312

Year of fee payment: 7

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

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20090115

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

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20091231

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20100831

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

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20100701