EP0073735B1 - Electrolytic pot for the production of aluminium by electrolysis in the dry way, and method of inserting the iron bars - Google Patents

Electrolytic pot for the production of aluminium by electrolysis in the dry way, and method of inserting the iron bars Download PDF

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Publication number
EP0073735B1
EP0073735B1 EP82810344A EP82810344A EP0073735B1 EP 0073735 B1 EP0073735 B1 EP 0073735B1 EP 82810344 A EP82810344 A EP 82810344A EP 82810344 A EP82810344 A EP 82810344A EP 0073735 B1 EP0073735 B1 EP 0073735B1
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Prior art keywords
iron bars
iron
cross
bars
carbon
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German (de)
French (fr)
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EP0073735A2 (en
EP0073735A3 (en
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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

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  • the present invention relates to an electrolysis tank for the production of aluminum by means of melt flow electrolysis, consisting of an outer steel tank, a heat-insulating layer and an electrically conductive, resistant to the molten material inner lining made of transverse carbon blocks with longitudinally extending, downwardly open grooves that extend over at least 20% of the length - starting from the two end faces - into which massive iron bars protruding from the bottom surface and on both sides from the end faces of the carbon blocks are inserted.
  • the carbon blocks and the iron bars can be found in conventional electrolysis tanks in various dimensions with respect to length, width and height, as well as groove shapes.
  • the technique of iron casting is widely used today to create the connection between the carbon block and the iron ingot.
  • the iron bars placed in the groove of the carbon block are connected to the carbon by casting with cast iron.
  • Iron ingot and carbon block are preheated together and cooled to ambient temperature after pouring. Since the thermal expansion or contraction of iron is approximately four times greater than that of carbon, a gap is formed between carbon and cast iron when it cools down. If the carbon block provided with an iron bar is installed in an electrolysis cell, this gap only closes during the rise in temperature when the electrolysis cell is started up, which improves the electrical and mechanical contact between iron and carbon.
  • the iron bar which is expanding more rapidly, can act so strongly on the carbon of the cathode elements that cracks can occur in the cathode.
  • the cast iron has the disadvantage that it has a relatively low electrical conductivity. Furthermore, with conventional cast iron bars, the contact pressure in the uppermost area of the bar in the working position is often insufficient, so that it is not sufficient to produce the desired low electrical contact resistance from carbon to iron. In this case, the electric current does not flow the shortest way through the carbon base of the electrolysis tank, but makes a detour by not entering the top surface but the side surfaces of the iron bar. The two factors mentioned can cause a voltage drop, e.g. B. up to 0.1 volts, which has a negative impact on the energy balance of the electrolytic cell. Therefore, some time ago, as in J. Electrochemical Technology, Vol. 5, No. 3-4 (1967), pp.
  • the iron ingot should be fully connected to the carbon at working temperature. In practice, this can hardly be done.
  • the electrical contact resistance from graphite to iron is too high, or cracks occur in the graphite block, which reduce the lifespan of the electrolysis tub to an unacceptable extent.
  • US-H-430 385 discloses an electrolysis trough comprising a steel trough, a heat insulation layer and electrically conductive carbon blocks with solid iron bars inserted therein.
  • the carbon blocks have grooves which are open at the bottom as recesses into which the iron bars are inserted in the electrolysis cell and fastened with a binder made of electrically conductive, carbon-containing cement.
  • the ends of the iron bars extend through openings through the Tub to the outside.
  • the grooves can be dimensioned so that their depth is less than the height of the ingot inserted therein, whereby it protrudes from the bottom surface of the carbon block.
  • the inventor has set himself the task of further reducing the contact resistance from carbon to iron bars and increasing the service life of the electrolysis bath.
  • the grooves in the carbon blocks have cross sections which, at a temperature between 500 and 850 ° C., correspond exactly to the cross section of the iron bars heated to the same temperature.
  • the groove with the usual dimensions of carbon block and iron ingot, can be expanded by about 1 mm at its lower opening before the cracking in the carbon begins or even a carbon flap breaks off.
  • a certain elasticity of the carbon blocks is essential when anchoring the iron bars without pouring them in.
  • the preferred temperature of about 700 ° C At this temperature, the groove and the iron bar used therein have exactly the same cross-section, i.e. H. the iron bar lies full on the carbon along its entire circumference, but without exerting any pressure on it.
  • H the iron bar
  • the iron ingot presses on the carbon. Thanks to the elasticity of the expanding carbon lobes, however, no cracks occur, as would be the case if a hole were formed instead of a groove.
  • the iron bars can extend in a manner known per se over the entire length of the carbon blocks or can be severed in the middle, with a smaller or greater distance. It is known that in the melt flow electrolysis of aluminum most of the electrical current flows in the outer region of the iron bars of the electrolysis tank. It is therefore sufficient if the iron bars are formed from both ends of the carbon blocks up to at least 20% each with respect to the length of the carbon blocks towards the center of the tub. In the center of the carbon blocks, the iron bars can be separated up to 60% of the length of the blocks.
  • the grooves can extend over the entire length of the carbon block or over a part thereof corresponding to the iron ingot, the end walls of the iron ingot and groove being separated by a preferably 0.5-1 cm wide cavity.
  • the iron bars are inserted in an electrolysis trough with correspondingly recessed grooves open downwards in the working position by pushing the iron bars through bar windows in the steel trough at ambient temperature into the interior of the electrolysis trough.
  • These bar windows expediently have the same geometric shape as the cross section of the iron bars.
  • These ingot windows are preferably only slightly, in particular 0.5-2 cm, larger than the linear dimensions of the iron ingot cross sections, i.e. H. the iron bars are led through the bar windows into the interior of the tub with little play. In this case, the joints are easy to seal.
  • iron bars are rectangular at least in the lower region or are tapered towards the top, they can be placed on the insulation layer in accordance with the shaped grooves. The carbon block is then lowered onto them.
  • the invention is explained in more detail with reference to the embodiment shown in the drawing.
  • the single figure shows a schematic vertical section through a carbon block with two iron bars in the working position, but before the complete lowering.
  • the carbon block 10 which is rectangular in cross section, contains the round iron bars 12 which run parallel in the longitudinal direction in correspondingly shaped grooves 14 which are partially open at the bottom.
  • Each tab 16 of the carbon block 10 comprises the iron bars 12 in a U-shape. If the iron bars 12 exert pressure on the carbon block 10 at working temperature, the latter is caught by spreading the tabs 16 apart accordingly.
  • the edges 18 of these tabs 16 are preferably rounded or cut off.
  • the carbon block 10 inserted into the electrolysis trough lies along the surface line 20 of the iron ingot 12 on the insulation layer, not shown.
  • the iron bars 12 are pressed flatly in their upper area onto the corresponding area of the grooves 14, the contact resistance from carbon to iron is thereby minimal.
  • the direct electrical current can flow directly from the top surface of the carbon block 10 and with a low contact resistance in the direction of the arrows to the iron bar 12.

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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 vorliegende Erfindung bezieht sich auf eine Elektrolysewanne zur Herstellung von Aluminium mittels Schmelzflußelektrolyse, bestehend aus einer äußeren Stahlwanne, einer wärmedämmenden Isolationsschicht und einer elektrisch leitenden, gegen das schmelzflüssige Material beständigen Innenauskleidung aus in Querrichtung verlaufenden Kohlenstoffblöcken mit in deren Längsrichtung verlaufenden, nach unten offenen Nuten, die sich über mindestens 20% der Länge - ausgehend von den beiden Stirnseiten - erstrecken, in welche unten aus der Bodenfläche und beidseitig aus den Stirnseiten der Kohlenstoffblöcke herausragende massive Eisenbarren eingesetzt sind.The present invention relates to an electrolysis tank for the production of aluminum by means of melt flow electrolysis, consisting of an outer steel tank, a heat-insulating layer and an electrically conductive, resistant to the molten material inner lining made of transverse carbon blocks with longitudinally extending, downwardly open grooves that extend over at least 20% of the length - starting from the two end faces - into which massive iron bars protruding from the bottom surface and on both sides from the end faces of the carbon blocks are inserted.

Für die Gewinnung von Aluminium durch Elektrolyse von Aluminiumoxid wird dieses in einer Fluoridschmelze gelöst, die zum größten Teil aus Kryolith besteht. Das kathodisch abgeschiedene Aluminium sammelt sich unter der Fluoridschmelze auf dem Kohlenstoffboden der Zelle, wobei die Oberfläche des flüssigen Aluminiums die Kathode bildet. In die Schmelze tauchen von oben Anoden ein, die bei konventionellen Verfahren aus amorphem Kohlenstoff bestehen. Durch die elektrolytische Zersetzung des Aluminiumoxids entsteht Sauerstoff, der sich mit dem Kohlenstoff der Anoden zu C02 und CO verbindet. Die Elektrolyse findet in einem Temperaturbereich von etwa 940 - 9700 C statt.For the production of aluminum by 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 melt. 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 approx. 940 - 9700 C.

Die Innenauskleidung von Elektrolysewannen besteht aus Kohlenstoffblöcken, in welchen mindestens ein durchgehender oder in der Mitte getrennter Eisenbarren angeordnet ist. Um zu einem möglichst geringen Spannungsabfall der Zelle beizutragen, muß der elektrische Übergangswiderstand zwischen Eisenbarren und Kohlenstoffblock möglichst klein sein. Dem Fachmann sind verschiedene Arten zur Verbindung von Kohlenstoffblock und Eisenbarren bekannt, beispielsweise

  • - Einstampfen mit einer Stampfmasse
  • - Eingießen mit Gußeisen
  • - Einkleben.
The inner lining of electrolysis tanks consists of carbon blocks, in which at least one continuous or in the middle separated iron bars is arranged. In order to contribute to the lowest possible voltage drop in the cell, the electrical contact resistance between the iron ingot and the carbon block must be as small as possible. Various ways of connecting carbon block and iron ingot are known to those skilled in the art, for example
  • - Pounding with a pounding compound
  • - Pour in with cast iron
  • - Glue in.

Die Kohlenstoffblöcke und die Eisenbarren finden sich in herkömmlichen Elektrolysewannen in verschiedensten Dimensionen in bezug auf Längs, Breite und Höhe sowie Nutformen.The carbon blocks and the iron bars can be found in conventional electrolysis tanks in various dimensions with respect to length, width and height, as well as groove shapes.

Beim Erstellen der Verbindung zwischen Kohlenstoffblock und Eisenbarren ist heute die Technik des Eisengießens weit verbreitet. Die in die Nut des Kohlenstoffblockes eingelegten Eisenbarren werden durch Umgießen mit Gußeisen mit dem Kohlenstoff verbunden. Eisenbarren und Kohlenstoffblock werden gemeinsam vorgewärmt und nach dem Eingießen auf die Umgebungstemperatur abgekühlt. Da die Wärmedehnung bzw. -kontraktion von Eisen ungefähr viermal größer ist als diejenige von Kohlenstoff, entsteht bei der Abkühlung zwischen Kohlenstoff und Gußeisen ein Spalt. Ist der mit einem Eisenbarren versehene Kohlenstoffblock in eine Elektrolysezelle eingebaut, so schließt sich dieser Spalt erst während des Temperaturanstiegs bei der Inbetriebnahme der Elektrolysezelle, womit der elektrische und mechanische Kontakt zwischen Eisen und Kohlenstoff verbessert wird.The technique of iron casting is widely used today to create the connection between the carbon block and the iron ingot. The iron bars placed in the groove of the carbon block are connected to the carbon by casting with cast iron. Iron ingot and carbon block are preheated together and cooled to ambient temperature after pouring. Since the thermal expansion or contraction of iron is approximately four times greater than that of carbon, a gap is formed between carbon and cast iron when it cools down. If the carbon block provided with an iron bar is installed in an electrolysis cell, this gap only closes during the rise in temperature when the electrolysis cell is started up, which improves the electrical and mechanical contact between iron and carbon.

Wird der durch die Kontraktion gebildete Spalt vor dem Erreichen der Arbeitstemperatur geschlossen, so kann der sich schneller ausdehnende Eisenbarren derart stark auf die Kohle der Kathodenelemente einwirken, daß in der Kathode Risse entstehen können.If the gap formed by the contraction is closed before the working temperature is reached, the iron bar, which is expanding more rapidly, can act so strongly on the carbon of the cathode elements that cracks can occur in the cathode.

Das Gußeisen weist den Nachteil auf, daß es eine verhältnismäßig niedrige elektrische Leitfähigkeit hat. Weiter ist bei üblichen eingegossenen Eisenbarren der Anpreßdruck im in Arbeitsposition obersten Bereich des Barrens oft ungenügend, so daß er nicht ausreicht, den erwünschten niedrigen elektrischen Übergangswiderstand vom Kohlenstoff zum Eisen herzustellen. In diesem Fall fließt der elektrische Strom nicht auf dem kürzesten Weg durch den Kohlenstoffboden der Elektrolysewanne, sondern macht einen Umweg, indem er nicht in die Deckfläche, sondern in die Seitenflächen des Eisenbarrens eintritt. Die beiden erwähnten Faktoren können einen Spannungsabfall, z. B. bis zu 0,1 Volt, bewirken, was sich in der Energiebilanz der Elektrolysezelle negativ niederschlägt. Schon vor einiger Zeit ist deshalb, wie im J. Electrochemical Technology, Vol. 5, No. 3-4 (1967), Seiten 152-154, beschrieben, versucht worden, einen Eisenbarren direkt mit dem Kohlenstoffblock in Verbindung zu bringen. Im Kohlenstoffblock wird ein dem Eisenbarren entsprechendes Loch ausgespart und dieser ohne Stampf-, Guß- oder Klebemasse hineingesteckt. Da aber in der verhältnismäßig langen Zwischenzeit keine Schmelzflußelektrolysezellen zur Herstellung von Aluminium, die nach diesem Prinzip gebaut sind, bekannt geworden sind, hat sich das Verfahren offensichtlich nicht bewährt.The cast iron has the disadvantage that it has a relatively low electrical conductivity. Furthermore, with conventional cast iron bars, the contact pressure in the uppermost area of the bar in the working position is often insufficient, so that it is not sufficient to produce the desired low electrical contact resistance from carbon to iron. In this case, the electric current does not flow the shortest way through the carbon base of the electrolysis tank, but makes a detour by not entering the top surface but the side surfaces of the iron bar. The two factors mentioned can cause a voltage drop, e.g. B. up to 0.1 volts, which has a negative impact on the energy balance of the electrolytic cell. Therefore, some time ago, as in J. Electrochemical Technology, Vol. 5, No. 3-4 (1967), pp. 152-154, attempts have been made to directly connect an iron ingot to the carbon block. A hole corresponding to the iron ingot is cut out in the carbon block and inserted without tamping, casting or adhesive. However, since no melt-flow electrolysis cells for the production of aluminum, which are built according to this principle, have become known in the relatively long meantime, the method has obviously not proven itself.

Nach dieser Publikation müßte der Eisenbarren bei Arbeitstemperatur satt an den Kohlenstoff anschließen. In der Praxis läßt sich dies kaum durchführen. Während des Elektrolyseprozesses ist bei kleinsten Ungenauigkeiten entweder der elektrische Übergangswiderstand vom Graphit zum Eisen zu groß, oder es entstehen im Graphitblock Risse, welche die Lebensdauer der Elektrolysewanne in untragbarem Maße erniedrigen.According to this publication, the iron ingot should be fully connected to the carbon at working temperature. In practice, this can hardly be done. During the electrolysis process, with the smallest inaccuracies, either the electrical contact resistance from graphite to iron is too high, or cracks occur in the graphite block, which reduce the lifespan of the electrolysis tub to an unacceptable extent.

In der US-H-430 385 wird eine Elektrolysewanne offenbart, die eine Stahlwanne, eine Wärmeisolationsschicht und elektrisch leitende Kohlenstoffblöcke mit darin eingesetzten massiven Eisenbarren umfaßt. Dabei haben die Kohlenstoffblöcke nach unten offene Nuten als Aussparungen, in welche die Eisenbarren in der Elektrolysezelle eingesetzt und mit einem Binder aus elektrisch leitendem, kohlenstoffhaltigem Zement befestigt werden. Die Enden der Eisenbarren erstrecken sich über Öffnungen durch die Wanne nach außen. Die Nuten können dabei so dimensioniert sein, daß deren Tiefe kleiner ist als die Höhe des darin eingesetzten Barrens, wodurch dieser aus der Bodenfläche des Kohlenstoffblocks herausragt.US-H-430 385 discloses an electrolysis trough comprising a steel trough, a heat insulation layer and electrically conductive carbon blocks with solid iron bars inserted therein. The carbon blocks have grooves which are open at the bottom as recesses into which the iron bars are inserted in the electrolysis cell and fastened with a binder made of electrically conductive, carbon-containing cement. The ends of the iron bars extend through openings through the Tub to the outside. The grooves can be dimensioned so that their depth is less than the height of the ingot inserted therein, whereby it protrudes from the bottom surface of the carbon block.

Der Erfinder hat sich die Aufgabe gestellt, den Übergangswiderstand vom Kohlenstoff zum Eisenbarren weiter zu verkleinern und die Lebensdauer der Elektrolysewanne zu erhöhen.The inventor has set himself the task of further reducing the contact resistance from carbon to iron bars and increasing the service life of the electrolysis bath.

Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß die Nuten in den Kohlenstoffblöcken Querschnitte haben, welche bei einer Temperatur zwischen 500 und 850°C exakt dem Querschnitt der auf dieselbe Temperatur erwärmten Eisenbarren entsprechen.The object is achieved in that the grooves in the carbon blocks have cross sections which, at a temperature between 500 and 850 ° C., correspond exactly to the cross section of the iron bars heated to the same temperature.

Versuche haben gezeigt, daß sich die Nut, bei üblichen Dimensionen von Kohlenstoffblock und Eisenbarren, an deren unteren Öffnung um ungefähr 1 mm spreizen läßt, bevor die Rißbildung im Kohlenstoff einsetzt oder gar ein Kohlenstofflappen abbricht. Eine gewisse Elastizität der Kohlenstoffblöcke ist beim Verankern der Eisenbarren ohne Eingießen von wesentlicher Bedeutung.Experiments have shown that the groove, with the usual dimensions of carbon block and iron ingot, can be expanded by about 1 mm at its lower opening before the cracking in the carbon begins or even a carbon flap breaks off. A certain elasticity of the carbon blocks is essential when anchoring the iron bars without pouring them in.

Dies soll anhand der bevorzugten Temperatur von etwa 700° C gezeigt werden: Bei dieser Temperatur haben die Nut und der darin eingesetzte Eisenbarren exakt den gleichen Querschnitt, d. h. der Eisenbarren liegt entlang seines ganzen Umfangs satt auf dem Kohlenstoff, jedoch ohne darauf einen Druck auszuüben. Bei höheren Temperaturen, über 700°C, beispielsweise bei der Aluminiumelektrolyse-Temperatur von 940-970°C, drückt der Eisenbarren auf den Kohlenstoff. Dank der Elastizität der sich spreizenden Kohlenstofflappen entstehen jeoch keine Risse, wie dies bei der Ausbildung eines Loches statt einer Nut der Fall wäre.This should be shown by the preferred temperature of about 700 ° C: At this temperature, the groove and the iron bar used therein have exactly the same cross-section, i.e. H. the iron bar lies full on the carbon along its entire circumference, but without exerting any pressure on it. At higher temperatures, above 700 ° C, for example at the aluminum electrolysis temperature of 940-970 ° C, the iron ingot presses on the carbon. Thanks to the elasticity of the expanding carbon lobes, however, no cracks occur, as would be the case if a hole were formed instead of a groove.

Ein Teil des Gewichts der Kohlenstoffauskleidung ist ungefähr gleichmäßig auf die aus den Kohlenstoffblöcken herausragenden Eisenbarren verteilt. Dadurch drücken diese Eisenbarren in Arbeitsposition auf den entsprechend geformten oberen Bereich der Nut, auch wenn der Querschnitt des Eisenbarrens kleiner als derjenige der Nut ist. Dieser Flächendruck hat zur Folge, daß ein möglichst kleiner Übergangswiderstand vom Kohlenstoff zum Eisen in jenem Bereich entsteht, der dem die Kathode der Elektrolysezelle bildenden flüssigen Aluminium am meisten benachbart ist.Part of the weight of the carbon liner is approximately evenly distributed over the iron ingots protruding from the carbon blocks. As a result, these iron bars press into the correspondingly shaped upper area of the groove in the working position, even if the cross section of the iron bar is smaller than that of the groove. The result of this surface pressure is that the contact resistance from carbon to iron is as small as possible in the area which is most adjacent to the liquid aluminum forming the cathode of the electrolytic cell.

Der Spannungsabfall wird also in bezug auf zwei Faktoren minimalisiert:

  • - Übergangswiderstand Kohlenstoff - Eisen
  • - Spannungsabfall in der Kohlenstoffauskleidung der Elektrolysewanne.
The voltage drop is therefore minimized in relation to two factors:
  • - Contact resistance carbon - iron
  • - Voltage drop in the carbon lining of the electrolysis bath.

Die Eisenbarren können sich auf an sich bekannte Weise über die gesamte Länge der Kohlenstoffblöcke erstrecken oder in der Mitte, mit kleinerem oder größerem Abstand, durchtrennt sein. Es ist bekannt, daß bei der Schmelzflußelektrolyse von Aluminium der größte Teil des elektrischen Stromes im äußeren Bereich der Eisenbarren der Elektrolysewanne abfließt. Es genügt deshalb, wenn die Eisenbarren von beiden Stirnseiten der Kohlenstoffblöcke her bis mindestens je 20% in bezug auf die Länge der Kohlenstoffblöcke zur Wannenmitte hin ausgebildet sind. Im Zentrum der Kohlenstoffblöcke können die Eisenbarren folglich bis zu 60% der Länge der Blöcke getrennt sein. Die Nuten können sich über die gesamte Länge des Kohlenstoffblockes oder über einen den Eisenbarren entsprechenden Teil davon erstrecken, wobei die Stirnwände von Eisenbarren und Nut durch einen vorzugsweise 0,5-1 cm breiten Hohlraum getrennt sind.The iron bars can extend in a manner known per se over the entire length of the carbon blocks or can be severed in the middle, with a smaller or greater distance. It is known that in the melt flow electrolysis of aluminum most of the electrical current flows in the outer region of the iron bars of the electrolysis tank. It is therefore sufficient if the iron bars are formed from both ends of the carbon blocks up to at least 20% each with respect to the length of the carbon blocks towards the center of the tub. In the center of the carbon blocks, the iron bars can be separated up to 60% of the length of the blocks. The grooves can extend over the entire length of the carbon block or over a part thereof corresponding to the iron ingot, the end walls of the iron ingot and groove being separated by a preferably 0.5-1 cm wide cavity.

Die vorzugsweise etwa 0,5-1,5 cm aus der Bodenfläche der Kohlenstoffblöcke herausragenden Eisenbarren und die entsprechend ausgesparte Nut können jede zweckmäßige geometrische Form haben. Bevorzugt haben jedoch Eisenbarren und entsprechende Nut, mindestens in ihrem in bezug auf die Arbeitsposition oberen Bereich, abgerundete Querschnitte. Dies bringt den wesentlichen Vorteil, daß beim Spreizen der den Eisenbarren seitlich umgebenden Lappen des Kohlenstoffblocks die Kerbwirkung herabgesetzt wird, d. h. bei im oberen Bereich abgerundeten Nuten setzt die Rißbildung erst bei größerem Druck durch den Eisenbarren ein, als dies bei eckig ausgebildeten Nuten der Fall wäre. Insbesondere Eisenbarren mit kreisrundem Querschnitt und entsprechend geformte Nuten sind vorteilhaft, weil

  • - runde Barren die kleinste Oberfläche bei konstantem Querschnitt haben, was gleiche elektrische Leitfähigkeit bei geringeren Wärmeverlusten bedeutet,
  • - die Festigkeit des Blockes wesentlich erhöht wird, da keine Kerbwirkung vorhanden ist,
  • - wegen des höheren maximalen Anpreßdrucks der elektrische Kontaktwiderstand vom Kohlenstoff zum Eisen verringert werden kann,
  • - aus der Stahlwanne einfache runde Barrenfenster ausgespart werden können, die mit vorfabrizierten Materialien leicht zu verdichten sind, und
  • - die Fertigung der Barren besonders einfach ist.
The iron bars, which preferably protrude about 0.5-1.5 cm from the bottom surface of the carbon blocks, and the correspondingly recessed groove can have any expedient geometric shape. However, iron bars and corresponding groove preferably have rounded cross sections, at least in their upper region with respect to the working position. This has the essential advantage that when the flaps of the carbon block laterally surrounding the iron ingot are spread, the notch effect is reduced, ie in the case of grooves rounded in the upper region, the cracking only begins with greater pressure from the iron ingot than would be the case with angular grooves . In particular, iron bars with a circular cross section and appropriately shaped grooves are advantageous because
  • - round bars have the smallest surface with a constant cross-section, which means the same electrical conductivity with less heat loss,
  • the strength of the block is increased significantly since there is no notch effect,
  • the electrical contact resistance from carbon to iron can be reduced due to the higher maximum contact pressure,
  • - Simple round ingot windows can be left out of the steel tub, which are easy to compress with prefabricated materials, and
  • - The manufacture of the bars is particularly simple.

Das Einsetzen der Eisenbarren in einer Elektrolysewanne mit entsprechend ausgesparten in Arbeitsposition nach unten offenen Nuten erfolgt, indem die Eisenbarren durch Barrenfenster in der Stahlwanne bei Umgebungstemperatur in den Innenraum der Elektrolysewanne geschoben werden.The iron bars are inserted in an electrolysis trough with correspondingly recessed grooves open downwards in the working position by pushing the iron bars through bar windows in the steel trough at ambient temperature into the interior of the electrolysis trough.

Zweckmäßig haben diese Barrenfenster die gleiche geometrische Form wie der Querschnitt der Eisenbarren. Vorzugsweise sind diese Barrenfenster nur wenig, insbesondere 0,5-2 cm, größer als die linearen Dimensionen der Eisenbarrenquerschnitte, d. h. die Eisenbarren werden mit nur wenig Spiel durch die Barrenfenster in das Wanneninnere geführt. In diesem Fall sind die Fugen einfach abdichtbar.These bar windows expediently have the same geometric shape as the cross section of the iron bars. These ingot windows are preferably only slightly, in particular 0.5-2 cm, larger than the linear dimensions of the iron ingot cross sections, i.e. H. the iron bars are led through the bar windows into the interior of the tub with little play. In this case, the joints are easy to seal.

Sind die Eisenbarren mindestens im unteren Bereich rechteckig oder sich nach oben verjüngend ausgebildet, so können sie, entsprechend den ausgeformten Nuten, auf die lsolationsschicht gelegt werden. Anschließend wird der Kohlenstoffblock auf sie abgesenkt.If the iron bars are rectangular at least in the lower region or are tapered towards the top, they can be placed on the insulation layer in accordance with the shaped grooves. The carbon block is then lowered onto them.

Bevorzugt werden jedoch bei allen Barrenquerschnitten, bei im Querschnitt runden Eisenbarren ist dies aus geometrischen Gründen meist notwendig, die Kohlenstoffblöcke bis wenig, beispielsweise etwa 0,5-2,5 cm, über die Isolationsschicht abgesenkt, dann die Eisenbarren in die Nuten geschoben, und schließlich die Kohlenstoffblöcke vollständig abgesenkt. Diese liegen nun auf den Eisenbarren, die aus den Nuten herausragen.However, preference is given to all bar cross-sections, in the case of iron bars that are round in cross section, this is usually necessary for geometric reasons, the carbon blocks are lowered a little, for example about 0.5-2.5 cm, over the insulation layer, then the iron bars are pushed into the grooves, and finally the carbon blocks are completely lowered. These are now on the iron bars that protrude from the grooves.

Die Erfindung wird anhand des in der Zeichnung dargestellten Ausführungsbeispiels näher erläutert. Die einzige Figur zeigt einen schematischen Vertikalschnitt durch einen Kohlenstoffblock mit zwei Eisenbarren in Arbeitsposition, jedoch vor dem vollständigen Absenken.The invention is explained in more detail with reference to the embodiment shown in the drawing. The single figure shows a schematic vertical section through a carbon block with two iron bars in the working position, but before the complete lowering.

Der im Querschnitt rechteckige Kohlenstoffblock 10 enthält die parallel in Längsrichtung verlaufenden runden Eisenbarren 12 in entsprechend ausgeformten, nach unten teilweise offenen Nuten 14. Je zwei Lappen 16 des Kohlenstoffblocks 10 umfassen die Eisenbarren 12 U-förmig. Wenn die Eisenbarren 12 bei Arbeitstemperatur einen Druck auf den Kohlenstoffblock 10 ausüben, wird dieser aufgefangen, indem die Lappen 16 entsprechend auseinander gespreizt werden. Die Kanten 18 dieser Lappen 16 sind bevorzugt abgerundet oder abgeschnitten.The carbon block 10, which is rectangular in cross section, contains the round iron bars 12 which run parallel in the longitudinal direction in correspondingly shaped grooves 14 which are partially open at the bottom. Each tab 16 of the carbon block 10 comprises the iron bars 12 in a U-shape. If the iron bars 12 exert pressure on the carbon block 10 at working temperature, the latter is caught by spreading the tabs 16 apart accordingly. The edges 18 of these tabs 16 are preferably rounded or cut off.

Nach dem vollständigen Absenken liegt der in die Elektrolysewanne eingesetzte Kohlenstoffblock 10 entlang der Mantellinie 20 der Eisenbarren 12 auf der nicht gezeichneten Isolationsschicht. Dadurch werden die Eisenbarren 12 in ihrem oberen Bereich flächenförmig auf den entprechenden Bereich der Nuten 14 gedrückt, der Übergangswiderstand vom Kohlenstoff zum Eisen ist dadurch minimal. Der elektrische Gleichstrom kann auf direktem Weg von der Deckfläche des Kohlenstoffblocks 10 und mit geringem Übergangswiderstand in Richtung der Pfeile zum Eisenbarren 12 fließen.After complete lowering, the carbon block 10 inserted into the electrolysis trough lies along the surface line 20 of the iron ingot 12 on the insulation layer, not shown. As a result, the iron bars 12 are pressed flatly in their upper area onto the corresponding area of the grooves 14, the contact resistance from carbon to iron is thereby minimal. The direct electrical current can flow directly from the top surface of the carbon block 10 and with a low contact resistance in the direction of the arrows to the iron bar 12.

Die wesentlichen Vorteile der Erfindung können wie folgt zusammengefaßt werden:

  • - Die Eisenbarren müssen nicht mehr eingegossen, eingeklebt oder eingestampft werden, sondern können einfach durch Barrenfenster in eine entsprechende, nach unten offene Nut des Kohlenstoffblocks eingeschoben werden. Das bedeutet Ersparnisse in bezug auf Energie, Material, Zeitaufwand, Equipment und Werkstatt.
  • - Der Kohlenstoffblock ist nicht mehr den Gefahren des Eingießens ausgesetzt, die beim Transport, Vorwärmen, Eingießen und Manipulieren auftreten.
  • - Der Spannungsabfall des Elektrolyseprozesses im kathodischen Teil kann bis zu 0,1 Volt vermindert werden.
The main advantages of the invention can be summarized as follows:
  • - The iron bars no longer have to be poured in, glued in or stamped in, but can simply be inserted through bar windows into a corresponding groove of the carbon block which is open at the bottom. That means savings in terms of energy, material, time, equipment and workshop.
  • - The carbon block is no longer exposed to the dangers of pouring that occur during transport, preheating, pouring and manipulation.
  • - The voltage drop of the electrolysis process in the cathodic part can be reduced by up to 0.1 volt.

Claims (7)

1. A reduction pot for the production of aluminium by means of fusion electrolysis, consisting of an outer steel shell, a thermally insulating layer and an electrically conductive inner lining which is resistant to the molten charge and is made up of carbon blocks (10) running in the transverse direction and having running in their longitudinal direction grooves (14) which are open downwards and extend over at least 20% of the length - starting from the two endfaces - and in which are inserted solid iron bars (12) which project downwards out of the bottom face and on both sides out of the endfaces of the carbon blocks, where part of the weight of the carbon blocks (10) is borne approximately uniformly by all of the iron bars (12) projecting out of their bottom faces, characterized in that the grooves (14) in the carbon blocks (10) have cross-sections which at a temperature between 500 and 850° C correspond exactly with the cross-section of the iron bars (12) heated to the same temperature.
2. A reduction pot as in Claim 1, characterized in that the cross-section of the grooves (14) in the carbon blocks (10) heated to about 700° C corresponds exactly with the cross-section of the iron bars (12) heated to the same temperature.
3. A reduction pot as in Claim 1 or 2, characterized in that during the electrolytic process the iron bars (12) project 0.5-1.5 cm out of the bottom face of the carbon blocks (10).
4. A reduction pot as in at least one of the Claims 1-3, characterized in that the grooves (14) in the carbon blocks (10) and the corresponding iron bars (12) have at least in their upper - with respect to the working position - region rounded cross-sections.
5. A reduction pot as in Claim 4, characterized in that the cross-section of the grooves (14) and of the iron bars (12) is circular.
6. A reduction pot as in at least one of the Claims 1-5, characterized in that in the steel shell windows are provided for the bars, which have the same geometric shape as the cross-section of the iron bars (12).
7. A reduction pot as in Claim 6, characterized in that the windows for the bars are only a little, preferably 0.5-2 cm larger than the linear dimensions of the cross-sections of the iron bars.
EP82810344A 1981-08-31 1982-08-18 Electrolytic pot for the production of aluminium by electrolysis in the dry way, and method of inserting the iron bars Expired EP0073735B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82810344T ATE16202T1 (en) 1981-08-31 1982-08-18 ELECTROLYSIS TANK FOR THE PRODUCTION OF ALUMINUM BY MEANS OF MOLTEN FLOW ELECTROLYSIS AND METHOD OF INSERTING THE IRON BAR.

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
CH5567/81A CH657383A5 (en) 1981-08-31 1981-08-31 ELECTROLYSIS PAN FOR PRODUCING ALUMINUM BY MELTFLOW ELECTROLYSIS AND METHOD FOR INSERTING THE IRON BAR.
CH5567/81 1981-08-31
DE3135083A DE3135083C1 (en) 1981-08-31 1981-09-04 Electrolytic pot for producing aluminium by means of molten-salt electrolysis and method for employing the iron bars

Publications (3)

Publication Number Publication Date
EP0073735A2 EP0073735A2 (en) 1983-03-09
EP0073735A3 EP0073735A3 (en) 1983-04-20
EP0073735B1 true EP0073735B1 (en) 1985-10-23

Family

ID=25697998

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Application Number Title Priority Date Filing Date
EP82810344A Expired EP0073735B1 (en) 1981-08-31 1982-08-18 Electrolytic pot for the production of aluminium by electrolysis in the dry way, and method of inserting the iron bars

Country Status (7)

Country Link
EP (1) EP0073735B1 (en)
JP (1) JPS5845390A (en)
AU (1) AU557296B2 (en)
CA (1) CA1190517A (en)
CH (1) CH657383A5 (en)
DE (1) DE3135083C1 (en)
ZA (1) ZA826026B (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO157462C (en) * 1985-10-24 1988-03-23 Hydro Aluminium As LAMINATED CARBON CATHOD FOR CELLS-MELT-ELECTROLYTIC ALUMINUM PREPARATION.
GB2542150A (en) * 2015-09-09 2017-03-15 Dubai Aluminium Pjsc Cathode assembly for electrolytic cell suitable for the Hall-Héroult process
DE102016210693A1 (en) * 2016-06-15 2017-12-21 Sgl Cfl Ce Gmbh Cathode block having a novel groove geometry

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2105247C3 (en) * 1971-02-04 1980-06-12 Schweizerische Aluminium Ag, Zuerich (Schweiz) Furnace for the fused aluminum electrolysis
US3851377A (en) * 1973-03-27 1974-12-03 D Dumas Sealing of metal bars in carbonized blocks
US4001104A (en) * 1974-01-03 1977-01-04 Union Carbide Corporation Cemented collector bar assemblies for aluminum cell carbon bottom block
US4076610A (en) * 1975-07-10 1978-02-28 Elettrocarbonium S.P.A. Cathode in cells for producing aluminium by electrolysis of smelted salts thereof
FR2318244A1 (en) * 1975-07-17 1977-02-11 Savoie Electrodes Refactaires PROCESS FOR JOINING METAL BARS WITH CARBON BLOCKS

Also Published As

Publication number Publication date
JPS5845390A (en) 1983-03-16
DE3135083C1 (en) 1983-03-10
AU8748082A (en) 1983-03-10
CH657383A5 (en) 1986-08-29
EP0073735A2 (en) 1983-03-09
CA1190517A (en) 1985-07-16
AU557296B2 (en) 1986-12-18
EP0073735A3 (en) 1983-04-20
ZA826026B (en) 1983-07-27

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