EP1481115B1 - Graphitized cathode blocks - Google Patents
Graphitized cathode blocks Download PDFInfo
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- EP1481115B1 EP1481115B1 EP02796687A EP02796687A EP1481115B1 EP 1481115 B1 EP1481115 B1 EP 1481115B1 EP 02796687 A EP02796687 A EP 02796687A EP 02796687 A EP02796687 A EP 02796687A EP 1481115 B1 EP1481115 B1 EP 1481115B1
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- European Patent Office
- Prior art keywords
- cathode
- joined
- cathode blocks
- parts
- blocks
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- 238000000034 method Methods 0.000 claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 6
- 229910001610 cryolite Inorganic materials 0.000 claims description 4
- 238000005868 electrolysis reaction Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims 2
- 238000007906 compression Methods 0.000 claims 2
- 239000004411 aluminium Substances 0.000 claims 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 238000005087 graphitization Methods 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 7
- 238000009826 distribution Methods 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 4
- 230000001070 adhesive effect Effects 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 2
- 239000003830 anthracite Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000009626 Hall-Héroult process Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 210000000689 upper leg Anatomy 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
Definitions
- the invention relates to graphitized cathode blocks, a process for their preparation and their Use in particular for the electrolytic production of aluminum.
- electrolytic cells which is composed of a plurality of blocks Soil, which acts as a cathode.
- the electrolyte is a melt, essentially one Solution of alumina in cryolite.
- the working temperature is for example at approx. 1000 ° C.
- the electrolytically deposited molten aluminum collects on the Bottom of the cell under a layer of the electrolyte.
- Around the cells is a metallic one Housing (preferably steel) with a lining of high temperature resistant material.
- the material of the cathode blocks is because of the required chemical and thermal Resistance prefers carbon partially or partially by thermal treatment can be completely graphitized.
- For the preparation of such cathode blocks are 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 burning (carbonation) is usually at Temperatures of about 1200 ° C, the graphitization usually at temperatures of over 2400 ° C.
- While graphitized cathodes are preferred because of their higher electrical conductivity they show a greater erosion during operation, according to a medium annual decrease in their thickness of up to 80 mm. This wear is not uniform across the length of the cathode blocks (corresponding to the width of the cell) distributed, but changed the surface of the cathode blocks to a W-shaped profile. By the uneven Ablating the service life of the cathode blocks is limited by the points with the largest removal.
- One way to equalize the removal over the length of the cathode block and To extend the useful life is to make the cathode blocks so that their electrical resistance varies over the length, so that the current density (and thus the Wear) is uniform over its length or at least the smallest possible deviation over the length of its mean.
- composite cathodes formed are either made of several carbon blocks with different electrical Conductivity, which are arranged so that a uniform or approximate uniform current distribution results, or from carbon blocks whose electrical Resistances in the direction of the cathodic leads continuously increase.
- the number The carbon blocks and their electrical resistance depend on cell size and cell type, they have to be recalculated for each case.
- Cathode blocks from one Variety of single carbon blocks require a lot of effort in the Construction; Also, the joints must each be well sealed to an outflow to avoid the liquid aluminum at the joints.
- a graphite cathode which consists of a single Block consists, which has a variable over its length electrical conductivity, wherein the conductivity at the ends of the block is lower than in the middle.
- This uneven Distribution of the electrical conductivity is achieved by the during graphitization End zones are brought to a temperature of 2200 to 2500 ° C, while the middle Zone is exposed to a temperature of 2700 to 3000 ° C.
- These different Heat treatment can be achieved according to this teaching by two ways: once can the heat dissipation in the graphitizing furnace are limited differently, or it can Heat sinks are introduced in the neighborhood of the end zones, which reduces the heat loss increase.
- a transverse graphitization is the density of the heat-insulating bed changed so that the heat loss over the length of the cathode is uneven and to set the desired temperatures.
- Even with the longitudinal graphitization can by different execution of the heat-insulating bed of heat loss in the Be increased near the ends, or it will be for this purpose heat dissipating body preferably made of graphite introduced in their vicinity, which has a greater heat flow to the outside effect towards the furnace wall.
- the difference of the heat treatment may be due to local change the current density, with the result of different heat development.
- Change in the current density can, according to the teaching by different resistances of the conductive bed between two cathodes in an Acheson furnace (cross graphitization) For a longitudinal graphitization process no such solution is given.
- cathode blocks are graphitized by the longitudinal grafting method, the result is at the joints of the individual cathode blocks with each other or between them arranged electrically conductive connecting elements an electrical transition with a against the resistance inside the individual cathode blocks or the Connecting element increased resistance.
- This increased resistance leads to increased Heat development and thus to higher temperature, ie an acceleration of the Graphit michsre redesign. Therefore, the electrical resistance in longitudinal graphitization at the Ends of the cathode blocks usually lower than that in the middle of the cathode blocks. This distribution of the resistance or the electrical conductivity over the length of Cathode blocks is just the opposite of the desired course.
- cathode blocks with the desired course to simple Make way by placing the above-described cathode blocks in the middle cuts apart and reassembles in the opposite direction. This results in a Profile of the electrical resistance in the form of a rounded V at the thighs.
- the present invention therefore provides graphitized cathode blocks for the production of aluminum by electrolytic reduction of alumina in a bath of molten cryolite, characterized in that the cathode blocks consist of two parts are assembled and along their length a V-shaped profile of their electrical resistance wherein the resistor in the middle of the cathode blocks has a point of discontinuity and steadily increasing towards the ends, such that the resistance at the ends of the Parts in the middle in the ratio of at least 1.05: 1 stands.
- the cathode blocks are composed of two parts whose electrical Resistance increases steadily over its length, so that the resistance at the ends of the parts to in the middle in the ratio of at least 1.15: 1. This is particularly preferred Ratio 1.3: 1.
- FIG. 1 shows the course of the specific electrical resistance ⁇ , shown in the interior of the side view of a cathode block 4, calculated as ( R a / l), where R is the electrical resistance of a parallelepiped specimen, a its cross-sectional area, and l its length , over the length of the cathode block.
- the ends of the block, as obtained in longitudinal graphitization, are designated A.
- the cathode block is cut apart along the line BB, the end faces at A are denoted as 4-1 , and the parting line along the line BB in the side cut is called 4-2 .
- the separated cathode block is then assembled as shown in Figs. 2 to 4, that the ends A and the end faces 4-1 are located in the center of the assembled cathode block.
- Fig. 2 shows an embodiment, wherein between the two ends now located in the middle A with the end faces 4-1 is a layer of ramming mass 5 , which otherwise also to seal the contact surfaces between the individual cathode blocks at the bottom of the tub of the electrolysis cell is used.
- a further preferred embodiment is shown, in which case the two half-blocks are joined together in each case with the ends A by a layer of an adhesive 6 with the required temperature resistance.
- Suitable adhesives are cold-curing resins such as BVK6 from SGL Carbon AG.
- FIG. 4 shows an embodiment in which an adhesive or intermediate layer was dispensed with, and the two half-blocks were joined together only with their ends A.
- the required surface pressure is applied in this case by the thermal expansion of the half-blocks, which are pressed together after flush installation in the electrolysis cells during heating. It has been found that the pressing force is greater enough to ensure a secure and tight connection of the two half-blocks, if the end surfaces were sufficiently flat prior to the division.
- the graphitized cathode blocks according to the invention show in the production of Aluminum by electrolytic reduction of alumina in a bath of molten cryolite over the conventional homogeneous distribution of electrical conductivity a more uniform wear over the length of the cathode and therefore a significantly increased service life.
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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)
Description
Die Erfindung betrifft graphitierte Kathodenblöcke, ein Verfahren zu ihrer Herstellung und ihre Verwendung insbesondere für die elektrolytische Herstellung von Aluminium.The invention relates to graphitized cathode blocks, a process for their preparation and their Use in particular for the electrolytic production of aluminum.
Bei der elektrolytischen Herstellung von Aluminium nach dem Hall-Héroult-Verfahren 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 Kryolith. 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 aluminum by the Hall-Héroult process be Used electrolytic cells, which is composed of a plurality of blocks Soil, which acts as a cathode. The electrolyte is a melt, essentially one Solution of alumina in cryolite. The working temperature is for example at approx. 1000 ° C. The electrolytically deposited molten aluminum collects on the Bottom of the cell under a layer of the electrolyte. Around the cells is a metallic one Housing (preferably steel) with a lining 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 2400 °C.The material of the cathode blocks is because of the required chemical and thermal Resistance prefers carbon partially or partially by thermal treatment can be completely graphitized. For the preparation of such cathode blocks are 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 burning (carbonation) is usually at Temperatures of about 1200 ° C, the graphitization usually at temperatures of over 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 a greater erosion during operation, according to a medium annual decrease in their thickness of up to 80 mm. This wear is not uniform across the length of the cathode blocks (corresponding to the width of the cell) distributed, but changed the surface of the cathode blocks to a W-shaped profile. By the uneven Ablating the service life of the cathode blocks is limited by the points with the largest 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 To extend the useful life is to make the cathode blocks so that their electrical resistance varies over the length, so that the current density (and thus the Wear) is uniform over its length or at least the smallest possible deviation over the length of its mean.
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 Zellentyp, 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, wherein composite cathodes formed are either made of several carbon blocks with different electrical Conductivity, which are arranged so that a uniform or approximate uniform current distribution results, or from carbon blocks whose electrical Resistances in the direction of the cathodic leads continuously increase. The number The carbon blocks and their electrical resistance depend on cell size and cell type, they have to be recalculated for each case. Cathode blocks from one Variety of single carbon blocks require a lot of effort in the Construction; Also, the joints must each be well sealed to an outflow to avoid the liquid aluminum 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.In WO 00/46426 a graphite cathode has been described, which consists of a single Block consists, which has a variable over its length electrical conductivity, wherein the conductivity at the ends of the block is lower than in the middle. This uneven Distribution of the electrical conductivity is achieved by the during graphitization End zones are brought to a temperature of 2200 to 2500 ° C, while the middle Zone is exposed to a temperature of 2700 to 3000 ° C. These different Heat treatment can be achieved according to this teaching by two ways: once can the heat dissipation in the graphitizing furnace are limited differently, or it can Heat sinks are introduced in the neighborhood of the end zones, which reduces the heat loss increase. In a transverse graphitization is the density of the heat-insulating bed changed so that the heat loss over the length of the cathode is uneven and to set the desired temperatures. Even with the longitudinal graphitization can by different execution of the heat-insulating bed of heat loss in the Be increased near the ends, or it will be for this purpose heat dissipating body preferably made of graphite introduced in their vicinity, which has a greater heat flow to the outside effect towards 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 Schüttung zwischen zwei Kathoden in einem Acheson-Ofen (Quergraphitierung) erfolgen, für ein Längsgraphitierungsverfahren ist kein derartige Lösung angegeben.According to another method, the difference of the heat treatment may be due to local change the current density, with the result of different heat development. These Change in the current density can, according to the teaching by different resistances of the conductive bed between two cathodes in an Acheson furnace (cross graphitization) For a longitudinal graphitization process no such solution is given.
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 Befüllung in mehreren Schritten eingebracht werden müßte und nach dem Abschluß des Ofenzyklus und dem Entfernen der Kathoden wieder entsprechend seiner Wärmeleitung bzw. elektrischen Leitfähigkeit klassiert werden müßte.These known methods have considerable disadvantages in practice. A difference from 500 ° C for the desired graphitization temperatures in the middle and at the ends of the Cathodes can not be reached by heat sinks alone. Different heat dissipation To the outside to the required extent brings a significant loss of energy, which the Manufacturing much more expensive. The higher heat loss to the side of the furnace means also a higher thermal stress, which makes the construction of the furnace more expensive or its life reduced. Finally, an inhomogeneity of the heat-insulating or the conductive bed is impractical, since the bulk material for filling in several Steps should be introduced and after the completion of the kiln cycle and the Remove the cathodes again according to its heat conduction or electrical Conductivity should be classified.
Es ist daher die Aufgabe der vorliegenden Erfindung, graphitierte Kathodenblöcke bereitzustellen, die über ihre Länge eine unterschiedliche elektrische Leitfähigkeit aufweisen.It is therefore the object of the present invention, graphitized cathode blocks to provide that have a different electrical conductivity over their length.
Werden Kathodenblöcke nach dem Verfahren der Längsgtaphitierung graphitiert, so ergibt sich an den Stoßstellen der einzelnen Kathodenblöcke untereinander oder mit zwischen diesen angeordneten elektrisch leitenden Verbindungselementen ein elektrischer Übergang mit einem gegenüber dem Widerstand im Inneren der einzelnen Kathodenblöcke oder des Verbindungselements erhöhtem Widerstand. Dieser erhöhte Widerstand führt zu erhöhter Wärmeentwicklung und damit zu höherer Temperatur, also einer Beschleunigung der Graphitierungsreaktion. Daher ist der elektrische Widerstand bei Längsgraphitierung an den Enden der Kathodenblöcke üblicherweise geringer als der in der Mitte der Kathodenblöcke. Diese Verteilung des Widerstandes bzw. der elektrischen Leitfähigkeit über die Länge des Kathodenblocks ist gerade das Gegenteil des gewünschten Verlaufs.If cathode blocks are graphitized by the longitudinal grafting method, the result is at the joints of the individual cathode blocks with each other or between them arranged electrically conductive connecting elements an electrical transition with a against the resistance inside the individual cathode blocks or the Connecting element increased resistance. This increased resistance leads to increased Heat development and thus to higher temperature, ie an acceleration of the Graphitierungsreaktion. Therefore, the electrical resistance in longitudinal graphitization at the Ends of the cathode blocks usually lower than that in the middle of the cathode blocks. This distribution of the resistance or the electrical conductivity over the length of Cathode blocks is just the opposite of the desired course.
Es wurde nun gefunden, daß sich Kathodenblöcke mit dem gewünschten Verlauf auf einfache Weise herstellen lassen, indem man die oben beschriebenen Kathodenblöcke in der Mitte auseinanderschneidet und in umgekehrter Richtung wieder zusammenfügt. Dabei ergibt sich ein Profil des elektrischen Widerstandes in Form eines an den Schenkeln gerundeten V.It has now been found that cathode blocks with the desired course to simple Make way by placing the above-described cathode blocks in the middle cuts apart and reassembles in the opposite direction. This results in a Profile of the electrical resistance in the form of a rounded V at the thighs.
Gegenstand der vorliegenden Erfindung sind daher graphitierte Kathodenblöcke zur Herstellung von Aluminium durch elektrolytische Reduktion von Aluminiumoxid in einem Bad von geschmolzenem Kryolith, dadurch gekennzeichnet, daß die Kathodenblöcke aus zwei Teilen zusammengesetzt sind und über ihre Länge ein V-förmiges Profil ihres elektrischen Widerstandes aufweisen, wobei der Widerstand in der Mitte der Kathodenblöcke eine Unstetigkeitsstelle aufweist und zu den Enden hin stetig zunimmt, derart daß der Widerstand an den Enden der Teile zu dem in der Mitte im Verhältnis von mindestens 1,05 : 1 steht.The present invention therefore provides graphitized cathode blocks for the production of aluminum by electrolytic reduction of alumina in a bath of molten cryolite, characterized in that the cathode blocks consist of two parts are assembled and along their length a V-shaped profile of their electrical resistance wherein the resistor in the middle of the cathode blocks has a point of discontinuity and steadily increasing towards the ends, such that the resistance at the ends of the Parts in the middle in the ratio of at least 1.05: 1 stands.
Bevorzugt sind die Kathodenblöcke aus zwei Teilen zusammengesetzt, deren elektrischer Widerstand über ihre Länge stetig ansteigt, derart daß der Widerstand an den Enden der Teile zu dem in der Mitte im Verhältnis von mindestens 1,15 : 1 steht. Besonders bevorzugt beträgt dies Verhältnis 1,3 : 1.Preferably, the cathode blocks are composed of two parts whose electrical Resistance increases steadily over its length, so that the resistance at the ends of the parts to in the middle in the ratio of at least 1.15: 1. This is particularly preferred Ratio 1.3: 1.
Die Erfindung wird durch die Zeichnungen näher erläutert. Dabei zeigen
- Fig. 1
- den Verlauf des spezifischen elektrischen Widerstandes ρ über die Länge des Kathodenblocks, wie er sich bei der Längsgraphitierung mit hohem Übergangswiderstand zwischen den einzelnen Kathodenblöcken ergibt, in die Seitenansicht eines Kathodenblocks eingezeichnet,
- Fig. 2
- eine Seitenansicht eines in der Mitte auseinandergetrennten und umgekehrt zusammengesetzten Kathodenblocks, wobei in der Mitte eine Verbindungsschicht aus Stampfmasse eingebracht ist,
- Fig. 3
- eine Seitenansicht eines in der Mitte auseinandergetrenmen und umgekehrt zusammengesetzten Kathodenblocks, wobei in der Mitte eine Klebefuge die beiden Teile verbindet, und
- Fig. 4
- eine Seitenansicht eines in der Mitte auseinandergetrennten und umgekehrt zusammengesetzten Kathodenblocks, wobei die beiden Teile lediglich bündig aneinandergesetzt sind.
- Fig. 1
- the course of the specific electrical resistance ρ over the length of the cathode block, as it results in the longitudinal graphitization with high contact resistance between the individual cathode blocks, drawn in the side view of a cathode block,
- Fig. 2
- a side view of a disassembled in the middle and vice versa assembled cathode block, wherein in the middle of a compound layer of ramming mass is introduced,
- Fig. 3
- a side view of a disassembled in the middle and vice versa assembled cathode block, wherein in the middle of an adhesive joint connects the two parts, and
- Fig. 4
- a side view of a disassembled in the middle and vice versa assembled cathode block, wherein the two parts are just juxtaposed.
Im einzelnen zeigt die Fig. 1 den im Inneren der Seitenansicht eines Kathodenblocks 4
dargestellten Verlauf des spezifischen elektrischen Widerstandes ρ, berechnet als ( R a /ℓ), wobei
R der elektrische Widerstand eines quaderförmigen Probekörpers ist, a dessen Querschnittsfläche,
und ℓ seine Länge, über die Länge des Kathodenblocks. Die Enden des Blocks,
wie er bei der Längsgraphitierung anfallt, sind mit A bezeichnet. Der Kathodenblock wird längs
der Linie BB auseinandergeschnitten, dabei sind die Endflächen bei A als 4-1 bezeichnet, und die
Trennfläche längs der Linie BB im Seitenschnitt heißt 4-2. Der getrennte Kathodenblock wird
nun so zusammengefügt wie in den Fig. 2 bis 4 dargestellt, daß die Enden A bzw. die
Endflächen 4-1 sich in der Mitte des zusammengesetzten Kathodenblocks befinden.1 shows the course of the specific electrical resistance ρ, shown in the interior of the side view of a
Die Fig. 2 zeigt eine Ausführungsform, wobei sich zwischen den beiden nunmehr in der Mitte befindlichen Enden A mit den Endflächen 4-1eine Lage der Stampfmasse 5 befindet, die ansonsten auch zur Abdichtung der Kontaktflächen zwischen den einzelnen Kathodenblöcken am Boden der Wanne der Elektrolysezelle verwendet wird. Geeignet sind hierzu Stampfmassen auf Basis von Anthrazit und Graphit mit einer Dichte von ca. 1700 kg/m3, wie BST 17/1 der SGL Carbon AG.Fig. 2 shows an embodiment, wherein between the two ends now located in the middle A with the end faces 4-1 is a layer of ramming mass 5 , which otherwise also to seal the contact surfaces between the individual cathode blocks at the bottom of the tub of the electrolysis cell is used. Suitable for this purpose are ramming compositions based on anthracite and graphite having a density of about 1700 kg / m 3 , such as BST 17/1 from SGL Carbon AG.
Die vorher innen liegenden Flächen 4-2 sind nun zu Außenflächen geworden. Der Verlauf des spezifischen elektrischen Widerstandes ρ ist nun derart, daß in der Mitte des Kathodenblocks der niedrigste Wert liegt, und der spezifische elektrische Widerstand nun symmetrisch zum Mittelpunkt zu den Enden hin ansteigt. In umgekehrter Weise ist dann der Verlauf der elektrischen Leitfähigkeit, nämlich von einem Gipfel in der Mitte des Kathodenblocks aus zu den Enden hin absteigend.The previously internal surfaces 4-2 have now become outer surfaces. The course of the electrical resistivity ρ is now such that in the middle of the cathode block is the lowest value, and the electrical resistivity now increases symmetrically to the center towards the ends. Conversely, then the course of the electrical conductivity, namely from a peak in the middle of the cathode block to the ends descending.
In der Fig. 3 ist eine weitere bevorzugte Ausführungsform dargestellt, wobei in diesem Fall die beiden Halbblöcke jeweils mit den Enden A durch eine Schicht eines Klebstoffs 6 mit der erforderlichen Temperaturbeständigkeit zusammengefügt sind.In Fig. 3, a further preferred embodiment is shown, in which case the two half-blocks are joined together in each case with the ends A by a layer of an adhesive 6 with the required temperature resistance.
Geeignete Klebstoffe sind kalthärtende Harze wie beispielsweise BVK6 der SGL Carbon AG. Suitable adhesives are cold-curing resins such as BVK6 from SGL Carbon AG.
Die Fig. 4 schließlich zeigt eine Ausführungsform, bei der auf eine Klebung oder Zwischenschicht verzichtet wurde, und die beiden Halbblöcke lediglich mit ihren Enden A aneinandergefügt wurden. Die erforderliche Flächenpressung wird in diesem Fall durch die thermische Ausdehnung der Halbblöcke aufgebracht, die nach bündigem Einbau in die Elektrolysezellen beim Aufheizen aufeinandergepreßt werden. Es hat sich gezeigt, daß die Preßkraft größ genug ist, um eine sichere und dichte Verbindung beider Halbblöcke sicherzustellen, wenn die Endflächen vor der Teilung ausreichend eben waren.Finally, FIG. 4 shows an embodiment in which an adhesive or intermediate layer was dispensed with, and the two half-blocks were joined together only with their ends A. The required surface pressure is applied in this case by the thermal expansion of the half-blocks, which are pressed together after flush installation in the electrolysis cells during heating. It has been found that the pressing force is greater enough to ensure a secure and tight connection of the two half-blocks, if the end surfaces were sufficiently flat prior to the division.
Die erfindungsgemäßen graphitierten Kathodenblöcke zeigen bei der Herstellung von Aluminium durch elektrolytische Reduktion von Aluminiumoxid in einem Bad von geschmolzenem Kryolith gegenüber den herkömmlichen mit homogener Verteilung der elektrischen Leitfähigkeit eine gleichmäßigere Abnutzung über die Länge der Kathode und daher eine deutlich erhöhte Standzeit.The graphitized cathode blocks according to the invention show in the production of Aluminum by electrolytic reduction of alumina in a bath of molten cryolite over the conventional homogeneous distribution of electrical conductivity a more uniform wear over the length of the cathode and therefore a significantly increased service life.
Claims (9)
- Graphitised cathode blocks for the production of aluminium by electrolytic reduction of aluminium oxide in a bath of molten cryolite, characterised in that the cathode blocks are composed of two parts and exhibit over their length a V-shaped profile of their specific electrical resistance, wherein the resistance comprises a discontinuity point in the middle of the cathode blocks and continuously increases towards the ends in such a manner that the ratio of the resistance at the ends of the parts to that in the middle is at least 1.05:1.
- Graphitised cathode blocks according to claim 1, characterised in that the cathode blocks are composed of two parts, the contact surfaces of the parts being joined by mechanical compression.
- Graphitised cathode blocks according to claim 1, characterised in that the cathode blocks are composed of two parts, the contact surfaces of the parts being joined by a tamping composition.
- Graphitised cathode blocks according to claim 1, characterised in that the cathode blocks are composed of two parts, the contact surfaces of the parts being adhesively bonded.
- A process for the production of graphitised cathode blocks according to claim 1, characterised in that a graphitised cathode block, the electrical conductivity of which corresponds to a flat U over the length of the profile, is divided in the middle and joined back together with the original outer sides directed inwards.
- A process according to claim 5, characterised in that the joined-together cathode block is joined in the electrolysis cell by mechanical compression.
- A process according to claim 5, characterised in that the joined-together cathode block is joined in the electrolysis cell by thermal expansion.
- A process according to claim 5, characterised in that the joined-together cathode block is joined in the middle by tamping composition.
- A process according to claim 5, characterised in that the joined-together cathode block is adhesively bonded in the middle.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10164008 | 2001-12-28 | ||
| DE2001164008 DE10164008C1 (en) | 2001-12-28 | 2001-12-28 | Graphitized cathode block, used for producing aluminum by electrolytically reducing aluminum oxide in a bath of molten cryolite, is composed of two parts and has a V-shaped profile of its electrical resistance over its length |
| PCT/EP2002/014548 WO2003056068A2 (en) | 2001-12-28 | 2002-12-19 | Graphitized cathode blocks |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1481115A2 EP1481115A2 (en) | 2004-12-01 |
| EP1481115B1 true EP1481115B1 (en) | 2005-12-07 |
Family
ID=7710902
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP02796687A Expired - Lifetime EP1481115B1 (en) | 2001-12-28 | 2002-12-19 | Graphitized cathode blocks |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP1481115B1 (en) |
| AR (1) | AR037912A1 (en) |
| AU (1) | AU2002361174A1 (en) |
| BR (1) | BR0215323A (en) |
| CA (1) | CA2470753A1 (en) |
| DE (2) | DE10164008C1 (en) |
| PL (1) | PL201672B1 (en) |
| WO (1) | WO2003056068A2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102011076302A1 (en) | 2011-05-23 | 2013-01-03 | Sgl Carbon Se | Electrolysis cell and cathode with irregular surface profiling |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2728109A (en) * | 1952-06-06 | 1955-12-27 | Savoie Electrodes Refract | Method of making cathodic electrodes for electrolysis furnaces |
| US4194959A (en) * | 1977-11-23 | 1980-03-25 | Alcan Research And Development Limited | Electrolytic reduction cells |
| NO157462C (en) * | 1985-10-24 | 1988-03-23 | Hydro Aluminium As | LAMINATED CARBON CATHOD FOR CELLS-MELT-ELECTROLYTIC ALUMINUM PREPARATION. |
| US4795540A (en) * | 1987-05-19 | 1989-01-03 | Comalco Aluminum, Ltd. | Slotted cathode collector bar for electrolyte reduction cell |
| FR2789091B1 (en) * | 1999-02-02 | 2001-03-09 | Carbone Savoie | GRAPHITE CATHODE FOR ALUMINUM ELECTROLYSIS |
| EP1233083A1 (en) * | 2001-02-14 | 2002-08-21 | Alcan Technology & Management AG | Carbon bottom of electrolysis cell used in the production of aluminum |
-
2001
- 2001-12-28 DE DE2001164008 patent/DE10164008C1/en not_active Expired - Fee Related
-
2002
- 2002-12-18 AR ARP020104963 patent/AR037912A1/en unknown
- 2002-12-19 AU AU2002361174A patent/AU2002361174A1/en not_active Abandoned
- 2002-12-19 EP EP02796687A patent/EP1481115B1/en not_active Expired - Lifetime
- 2002-12-19 WO PCT/EP2002/014548 patent/WO2003056068A2/en active IP Right Grant
- 2002-12-19 PL PL369969A patent/PL201672B1/en not_active IP Right Cessation
- 2002-12-19 CA CA002470753A patent/CA2470753A1/en not_active Abandoned
- 2002-12-19 DE DE50205232T patent/DE50205232D1/en not_active Expired - Fee Related
- 2002-12-19 BR BR0215323-8A patent/BR0215323A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| WO2003056068A2 (en) | 2003-07-10 |
| BR0215323A (en) | 2004-10-19 |
| DE10164008C1 (en) | 2003-04-30 |
| AR037912A1 (en) | 2004-12-22 |
| WO2003056068A3 (en) | 2004-09-30 |
| CA2470753A1 (en) | 2003-07-10 |
| DE50205232D1 (en) | 2006-01-12 |
| PL369969A1 (en) | 2005-05-02 |
| AU2002361174A1 (en) | 2003-07-15 |
| PL201672B1 (en) | 2009-04-30 |
| EP1481115A2 (en) | 2004-12-01 |
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