EP0132647B1 - Lining for an electrolytic cell for the production of aluminium - Google Patents
Lining for an electrolytic cell for the production of aluminium Download PDFInfo
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- EP0132647B1 EP0132647B1 EP84107810A EP84107810A EP0132647B1 EP 0132647 B1 EP0132647 B1 EP 0132647B1 EP 84107810 A EP84107810 A EP 84107810A EP 84107810 A EP84107810 A EP 84107810A EP 0132647 B1 EP0132647 B1 EP 0132647B1
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- lining
- graphite blocks
- graphite
- blocks
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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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- 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
- C25C3/085—Cell construction, e.g. bottoms, walls, cathodes characterised by its non electrically conducting heat insulating parts
Definitions
- the invention relates to a tub for the melt flow electrolytic production of aluminum, which consists of a steel tub lined with graphite blocks, a heat-insulating layer between the tub and the lining, and cathodic power supply lines let into the lining.
- Cells for the production of aluminum by electrolysis of aluminum oxide, which is dissolved in a fluoride melt, consist of a trough-shaped cathodic part which receives the molten electrolyte and the cathodically separated molten aluminum.
- Metallic materials have only limited resistance to the electrolyte and the electrolysis products at the electrolyte temperature of 940 to 980 ° C and must therefore be protected against the attack of electrolyte and electrolysis products.
- the cathodic part of the electrolytic cell therefore usually consists of a trough or a trough made of steel, which is lined with a temperature and corrosion-resistant material.
- the lining also connects the actual molten aluminum cathode with the cathodic power supply, so that the material must also be a good electrical conductor. Therefore, almost exclusively carbon and graphite blocks are used for the lining of the tub, which are connected to one another by carbon-containing tamping and cementing compounds and form a layer impermeable to molten metal and electrolyte.
- the functionality of the lining is essentially determined by its chemical and thermal resistance and its electrical resistance.
- Joulesche heat is developed in the lining, which is partly necessary for setting the electrolysis temperature. Because of the temperature difference between the electrolyte and the tub, greater energy losses due to heat conduction can only be avoided if the thermal resistance of the lining is very high.
- a heat-insulating layer of ceramic insulating materials is usually arranged between the lining made of carbon or graphite blocks and the tub.
- carbon-bonded graphite blocks are also used, without the geometry and type of heat insulation being adapted to the changed material properties.
- blocks consisting essentially of petroleum coke and heated to a high temperature, preferably at least 2000 ° C., have a particularly favorable resistance to the electrolyte (DE-OS 2 112 287).
- the properties of these blocks are approximately: bulk density - 1.57 g / cm 3 , porosity - 27%, spec. electrical resistance - 14 ⁇ m.
- the heat-insulating layer usually consists of refractory stones or powders with a thickness between 50 and 250 mm (US Pat. No. 3,434,957) and it is also known to assemble the heat-insulating layer from several individual layers (US Pat. No. 3,723,286). Finally, it is known to change the temperature gradients between the bottom and the side part of the lining by means of special insulating elements between these parts (US Pat. No. 4,118,304). These measures are not tailored to the material quality of the lining and their effects are limited accordingly.
- the invention is therefore based on the object of extending the life of electrolysis cells for producing aluminum and reducing the energy requirement by coordinating the heat-insulating layer and a lining of graphite stones.
- the accessible porosity of the graphite blocks is at most 18% and according to another embodiment, the thermal conductivity is 100 to 120 W / m - K and the spec. electrical resistance 6 to 10 ⁇ m.
- graphite blocks which have been impregnated with a carbonizable impregnating agent and impregnated for pyrolysis of the impregnating agent and have been heated to about 700 to 1,000 ° C. for pyrolysis of the impregnating agent.
- Coal tar pitch and petroleum pitch are particularly suitable as impregnating agents.
- the heat-insulating layer advantageously consists of chamotte, the compressive strength of which is more than 10 MPa.
- graphite is understood to mean carbon bodies which have been subjected to a graphitization treatment and have been heated to a temperature above about 2500 ° C.
- the result of this treatment depends essentially on the starting products, e.g. B. type of coke used, and the manufacturing parameters, e.g. B. the molding process, so that the products referred to as graphite are only able to a small extent to meet the requirements in a cell for the melt flow electrolytic production of aluminum. It has been found that the useful for this purpose part 'of the material group graphite can be sorted out with the help of its material properties.
- the mixture is formed into blocks and the blocks in a first stage for carbonizing the binder to about 1,000 ° C. and heated to 2600 to 3000 ° C in a second stage.
- the use of raw materials with upstream structural elements and the use of higher temperatures result in graphite blocks with a comparatively high thermal conductivity and a low specific electrical resistance.
- the thermal conductivity of the blocks is 80 to 120 W / m-K and the specific electrical resistance is 6 to 13 ⁇ m.
- the comparatively low resistance brings about a substantial reduction in the voltage drop in the lining, in which less Joule heat is generated accordingly.
- the open pore volume of the graphite blocks accessible to the melt must also be reduced.
- the accessible pore volume should be at most 22% and, according to a preferred embodiment of the invention, at most 18%.
- the graphite blocks forming the lining of the trough are expediently glued to one another without any joints, the term “seamless joints being understood to have a width of at most 1 mm.
- the plastic compounds described in EP 0 027 534 are particularly suitable as joint cement.
- the usual joints with a width of 20 mm and more are weak points in the lining, which are easily destroyed by thermal stress or by diffusing melt.
- the steel trough is designated 1.
- the heat-insulating layer consists of the sub-layers 2 and 3, the thermal conductivity of which is 0.1 to 0.2 W / m - K and 0.8 to 1.2 W / m - K.
- the ratio of the thermal resistance of the layers is about 0.05.
- Current bars or rails 5 are embedded in the graphite blocks 4 resting on the layer 3.
- the thermal conductivity of the graphite blocks is 80 to 120 W / m - K, the specific electrical resistance 6 to 13 ⁇ m and the accessible pore volume is at most 22%.
- the thickness ratio of the graphite layer 4 to the sum of the layers 2 and 3 is 1.5 to 1.6.
- the graphite blocks 4 completely line the tub floor, the tub side surfaces are shielded by the block 6, which consists of graphite or carbon.
- the actual cathode is the aluminum layer 7.
- the anodes 9 with the anodic power supply 10 are immersed in the molten electrolyte 8 and are protected against the attack of atmospheric oxygen by the crust 11, which mainly consists of alumina.
- the voltage drop measured when commissioning a cell to extract aluminum is essentially a function of the lining.
- the voltage drop of a lining made of carbon blocks is about 400 mV
- a lining made of carbon-bonded graphite blocks is about 300 mV
- a lining made of graphite blocks according to the invention is only about 200 mV.
- the temperature of the tub for these linings and a heat-insulating layer, formed from two sub-layers A and B with the thermal conductivity 1.0 and 0.1 W / m - K, is approximately 150 to 50 ° C (Table 1).
- the low energy losses of the lining according to the invention can of course only be realized if the parameters measured when the electrolysis cell is started up do not change or change only slightly during the operation of the cell.
- 2 shows the increase in the voltage drop as a function of the operating time; A is a liner made of carbon blocks, B is a liner made of carbon-bonded graphite and C is one made of graphite blocks.
- the increase in the voltage drop with the operating time is essentially caused by the increasing decomposition and destruction of the lining.
- the original advantage of linings according to the invention not only remains when the electrolysis cell is in operation, but also increases as the operating time progresses.
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- Electrolytic Production Of Metals (AREA)
Description
Die Erfindung betrifft eine Wanne für die schmelzflußelektrolytische Herstellung von Aluminium, die aus einer mit-Graphitblöcken ausgekleideten Stahlwanne, einer wärmedämmenden Isolationsschicht zwischen Wanne und Auskleidung und in die Auskleidung eingelassene kathodische Stromzuführungen besteht.The invention relates to a tub for the melt flow electrolytic production of aluminum, which consists of a steel tub lined with graphite blocks, a heat-insulating layer between the tub and the lining, and cathodic power supply lines let into the lining.
Zellen für die Gewinnung von Aluminium durch Elektrolyse von Aluminiumoxid, das in einer Fluorid-Schmelze gelöst ist, bestehen aus einem wannenförmigen kathodischen Teil, der den schmelzflüssigen Elektrolyten und das kathodisch abgeschiedene schmelzflüssige Aluminium aufnimmt. Metallische Werkstoffe sind unter der Elektrolyttemperatur von 940 bis 980 °C gegen den Elektrolyten und die Elektrolyseprodukte nur begrenzt beständig und müssen daher gegen den Angriff von Elektrolyt und Elektrolyseprodukten geschützt werden. Der kathodische Teil der Elektrolysezelle besteht daher üblicherweise aus einer Wanne oder einem Trog aus Stahl, der mit einem temperatur- und korrosionsbeständigen Werkstoff ausgekleidet ist. Die Auskleidung verbindet zugleich die eigentliche, aus schmelzflüssigem Aluminium bestehende Kathode mit den kathodischen Stromzuführungen, so daß der Werkstoff auch ein guter elektrischer Leiter sein muß. Man verwendet daher für die Auskleidung der Wanne fast ausschließlich Kohlenstoff- und Graphitblöcke, die durch kohlenstoffhaltige Stampf- und Kittmassen miteinander verbunden sind und eine gegen schmelzflüssiges Metall und Elektrolyt undurchlässige Schicht bilden.Cells for the production of aluminum by electrolysis of aluminum oxide, which is dissolved in a fluoride melt, consist of a trough-shaped cathodic part which receives the molten electrolyte and the cathodically separated molten aluminum. Metallic materials have only limited resistance to the electrolyte and the electrolysis products at the electrolyte temperature of 940 to 980 ° C and must therefore be protected against the attack of electrolyte and electrolysis products. The cathodic part of the electrolytic cell therefore usually consists of a trough or a trough made of steel, which is lined with a temperature and corrosion-resistant material. The lining also connects the actual molten aluminum cathode with the cathodic power supply, so that the material must also be a good electrical conductor. Therefore, almost exclusively carbon and graphite blocks are used for the lining of the tub, which are connected to one another by carbon-containing tamping and cementing compounds and form a layer impermeable to molten metal and electrolyte.
Die Funktionstüchtigkeit der Auskleidung wird im wesentlichen durch ihre chemische und thermische Beständigkeit und ihren elektrischen Widerstand bestimmt. Beim Betrieb der Elektrolysezelle wird in der Auskleidung Joulesche Wärme entwickelt, die zu einem Teil für die Einstellung der Elektrolysetemperatur nötig ist. Wegen der Temperaturdifferenz zwischen Elektrolyt und Wanne sind größere Energieverluste durch Wärmeleitung nur vermeidbar, wenn der Wärmewiderstand der Auskleidung sehr groß ist. Zur Verringerung der Verluste ordnet man üblicherweise zwischen der Auskleidung aus Kohlenstoff- oder Graphitblöcken und der Wanne eine wärmedämmende Schicht aus keramischen Isolierstoffen an. Obgleich Auskleidung und wärmedämmende Schicht eine funktionelle Einheit sind, hat man bisher nicht erkannt, daß Auskleidung und wärmedämmende Isolierschicht nur dann eine für den Elektrolysebetrieb vorteilhafte Einheit bilden, wenn die Stoffeigenschaften und die geometrische Auslegung aufeinander abgestimmt sind. Der Austausch von Kohlenstoffblöcken durch Graphitblöcke ohne gleichzeitige Änderung der Wärmeisolation hat aus diesem Grund keine größere Wirkung, obwohl Graphit einen vergleichsweise kleineren elektrischen Widerstand hat und gegen den Elektrolyten beständiger als Kohlenstoff ist. So ist es beispielsweise durch die US-PS 3 369 986 bekannt, die Wanne alternativ mit Kohlenstoffblöcken und Graphitblöcken ohne Änderung der Wärmeisolation auszukleiden, obwohl der elektrische Widerstand der Auskleidung sich etwa wie 4 : 1 und der gemessene Spannungsabfall in der Auskleidung etwa wie 2,5:1 1 verhält. Nach der DE-PS2105247, wird die kathodische Stromdichte durch eine Auskleidung verbessert, die Kohlenstoffblöcke und Graphitblöcke enthält. Statt der Graphitblöcke verwendet man auch kohlenstoffgebundene Graphitblöcke (Semigraphit, Hartgraphit), ohne daß Geometrie und Art der Wärmeisolierung an die geänderten Stoffeigenschaften angepaßt sind. Es ist auch bekannt, daß im wesentlichen aus Petrolkoks bestehende und auf eine hohe Temperatur, bevorzugt wenigstens 2000°C, erhitzte Blöcke eine besonders günstige Beständigkeit gegen den Elektrolyten haben (DE-OS 2 112 287). Die Eigenschaften dieser Blöcke sind etwa : Rohdichte - 1,57 g/cm3, Porosität - 27 %, spez. elektrischer Widerstand - 14 µΩm. Über die Beschaffenheit der wärmedämmenden Schicht ist nichts bekannt geworden.The functionality of the lining is essentially determined by its chemical and thermal resistance and its electrical resistance. When operating the electrolysis cell, Joulesche heat is developed in the lining, which is partly necessary for setting the electrolysis temperature. Because of the temperature difference between the electrolyte and the tub, greater energy losses due to heat conduction can only be avoided if the thermal resistance of the lining is very high. In order to reduce the losses, a heat-insulating layer of ceramic insulating materials is usually arranged between the lining made of carbon or graphite blocks and the tub. Although the lining and the heat-insulating layer are a functional unit, it has not hitherto been recognized that the lining and the heat-insulating layer only form an advantageous unit for the electrolysis operation if the material properties and the geometric design are coordinated. For this reason, replacing carbon blocks with graphite blocks without simultaneously changing the thermal insulation has no greater effect, although graphite has a comparatively lower electrical resistance and is more resistant to the electrolyte than carbon. For example, it is known from US Pat. No. 3,369,986 to alternatively line the tub with carbon blocks and graphite blocks without changing the heat insulation, although the electrical resistance of the lining is approximately 4: 1 and the measured voltage drop in the lining approximately as 2. 5: 1 1 behaves. According to DE-PS2105247, the cathodic current density is improved by a lining that contains carbon blocks and graphite blocks. Instead of the graphite blocks, carbon-bonded graphite blocks (semigraphite, hard graphite) are also used, without the geometry and type of heat insulation being adapted to the changed material properties. It is also known that blocks consisting essentially of petroleum coke and heated to a high temperature, preferably at least 2000 ° C., have a particularly favorable resistance to the electrolyte (DE-OS 2 112 287). The properties of these blocks are approximately: bulk density - 1.57 g / cm 3 , porosity - 27%, spec. electrical resistance - 14 µΩm. Nothing is known about the nature of the insulating layer.
Die wärmedämmende Schicht besteht üblicherweise aus feuerfesten Steinen oder Pulvern in einer Dicke zwischen 50 und 250 mm (US-PS 3 434 957) und es ist auch bekannt, die wärmedämmende Schicht aus mehreren Einzelschichten zusammenzusetzen (US-PS 3 723 286). Schließlich ist es bekannt, die Temperaturgradienten zwischen Boden und Seitenteil der Auskleidung durch besondere Isolierelemente zwischen diesen Teilen zu ändern (US-PS 4118 304). Diese Maßnahmen sind nicht auf die stoffliche Qualität der Auskleidung abgestimmt und ihre Wirkungen entsprechend begrenzt.The heat-insulating layer usually consists of refractory stones or powders with a thickness between 50 and 250 mm (US Pat. No. 3,434,957) and it is also known to assemble the heat-insulating layer from several individual layers (US Pat. No. 3,723,286). Finally, it is known to change the temperature gradients between the bottom and the side part of the lining by means of special insulating elements between these parts (US Pat. No. 4,118,304). These measures are not tailored to the material quality of the lining and their effects are limited accordingly.
Der Erfindung liegt daher die Aufgabe zugrunde, durch die Abstimmung von wärmedämmender Schicht und einer Auskleidung aus Graphitsteinen die Lebensdauer von Elektrolysezellen zur Erzeugung von Aluminium zu verlängern und den Energiebedarf zu senken.The invention is therefore based on the object of extending the life of electrolysis cells for producing aluminum and reducing the energy requirement by coordinating the heat-insulating layer and a lining of graphite stones.
Die Aufgabe wird mit einer ausgekleideten Wanne der eingangs genannten Art gelöst, die
- a) mit Graphitblöcken ausgekleidet ist, die eine Wärmeleitfähigkeit von 80 bis 120 W/m - K, einen spez. elektrischen Widerstand von 6 bis 12, µΩm und ein zugängliches Porenvolumen von höchstens 22 % haben,
- b) eine aus wenigstens zwei Teilschichten mit einer Wärmeleitfähigkeit von 0,1 bis 0,2 und 0,8 bis 1,2 W/m - K bestehende wärmedämmende Isolierschicht enthält und
- c) ein Dickenverhältnis von Auskleidung und Isolierschicht von 1,5 bis 3,0 hat.
- a) is lined with graphite blocks that have a thermal conductivity of 80 to 120 W / m - K, a spec. have electrical resistance of 6 to 12 µΩm and an accessible pore volume of at most 22%,
- b) contains an insulating insulating layer consisting of at least two partial layers with a thermal conductivity of 0.1 to 0.2 and 0.8 to 1.2 W / m-K and
- c) has a thickness ratio of lining and insulating layer of 1.5 to 3.0.
Nach einer bevorzugten Ausbildung der Erfindung beträgt die zugängliche Porosität der Graphitblöcke höchstens 18 % und nach einer anderen Ausführungsform ist die Wärmeleitfähigkeit 100 bis 120 W/m - K und der spez. elektrische Widerstand 6 bis 10 µΩm. Besonders geeignet sind auch Graphitblöcke, die mit einem carbonisierbaren Imprägniermittel imprägniert und zur Pyrolyse des Imprägniermittel imprägniert und zur Pyrolyse des Imprägniermittels auf etwa 700 bis 1 000 °C erhitzt worden sind. Als lmprägniermittel eignen sich besonders Steinkohlenteerpeche und Petrolpeche. Die wärmedämmende Isolationsschicht besteht vorteilhaft aus Schamotte, deren Druckfestigkeit mehr als 10 MPa beträgt.According to a preferred embodiment of the invention, the accessible porosity of the graphite blocks is at most 18% and according to another embodiment, the thermal conductivity is 100 to 120 W / m - K and the spec. electrical resistance 6 to 10 µΩm. Also particularly suitable are graphite blocks which have been impregnated with a carbonizable impregnating agent and impregnated for pyrolysis of the impregnating agent and have been heated to about 700 to 1,000 ° C. for pyrolysis of the impregnating agent. Coal tar pitch and petroleum pitch are particularly suitable as impregnating agents. The heat-insulating layer advantageously consists of chamotte, the compressive strength of which is more than 10 MPa.
Unter dem Terminus « Graphit versteht man Kohlenstoffkörper, die einer Graphitierungsbehandlung unterworfen und dabei auf eine Temperatur oberhalb etwa 2 500 °C erhitzt wurden. Das Ergebnis dieser Behandlung hängt wesentlich von den Ausgangsprodukten, z. B. Art des verwendeten Kokses, und den Herstellungsparametern ab, z. B. das Formungsverfahren, so daß die als Graphit bezeichneten Produkte nur zu einem kleinen Teil den Anforderungen in einer Zelle zur schmelzflußelektrolytischen Herstellung von Aluminium gewachsen sind. Es wurde gefunden, daß der für diesen Zweck brauchbare Teil' der Werkstoffgruppe Graphit mit Hilfe seiner Stoffeigenschaften ausgesondert werden kann.The term “graphite” is understood to mean carbon bodies which have been subjected to a graphitization treatment and have been heated to a temperature above about 2500 ° C. The result of this treatment depends essentially on the starting products, e.g. B. type of coke used, and the manufacturing parameters, e.g. B. the molding process, so that the products referred to as graphite are only able to a small extent to meet the requirements in a cell for the melt flow electrolytic production of aluminum. It has been found that the useful for this purpose part 'of the material group graphite can be sorted out with the help of its material properties.
Zur Herstellung der Graphitblöcke werden in bekannter Weise Petrolkoks, Anthracit und andere im wesentlichen aus Kohlenstoff bestehende Stoffe zusammen mit einem carbonisierbaren Binder gemischt, die Mischung wird zu Blöcken geformt und die Blöcke in einer ersten Stufe zur Carbonisierung des Binders auf etwa 1 000 °C und in einer zweiten Stufe auf 2600 bis 3000°C erhitzt. Durch die Verwendung von Rohstoffen mit vorgeordneten Strukturelementen und die Anwendung höherer Temperaturen erhält man Graphitblöcke mit vergleichsweise hoher Wärmeleitfähigkeit und einem kleinen spezifischen elektrischen Widerstand. Nach der Erfindung beträgt die Wärmeleitfähigkeit der Blöcke 80 bis 120 W/m - K und der spezifische elektrische Widerstand 6 bis 13 µΩm. Der vergleichsweise kleine Widerstand bewirkt eine wesentliche Senkung des Spannungsabfalls in der Auskleidung, in der entsprechend weniger Joulesche Wärme erzeugt wird. Durch die große Wärmeleitfähigkeit der Graphitblöcke werden größere, gegebenenfalls die Lebensdauer der Zelle beeinträchtigende Temperaturdifferenzen in der Auskleidung ausgeschlossen und in Verbindung mit der thermischen Isolierschicht wird ein stärkerer Energieabfluß aus dem schmelzflüssigen Elektrolyten vermieden. Der Effekt ist besonders günstig für Auskleidungen, die Graphitblöcke mit einer Wärmeleitfähigkeit von 100 bis 120 W/m - K und einem spez. elektrischen Widerstand von 6 bis 10 pnm enthalten. Es wurde schließlich gefunden, daß zur Erzielung einer großen Lebensdauer der Elektrolysezelle auch das offene, für die Schmelze zugängliche Porenvolumen der Graphitblöcke vermindert werden muß. Das zugängliche Porenvolumen soll höchstens 22 % und nach einer bevorzugten Ausführung der Erfindung höchstens 18 % betragen. Es ist bekannt, für die Auskleidung der Wannen von Elektrolysezellen bestimmte Kohlenstoff- und Graphitblöcke mit Furfurol oder Furfurylalkohol zu imprägnieren und das Imprägniermittel in situ zu verkoken (US-PS 3 616 045). Durch dieses Verfahren wird das zugängliche Porenvolumen verkleinert, die Größe des zugänglichen Porenvolumens dieser Blöcke ist aber nicht bekannt. Zur Verringerung des zugänglichen Porenvolumens ist besonders ein Verfahren geeignet, bei welchem der poröse Graphitkörper mit Steinkohlenteerpech oder Petrolpech imprägniert und zur Verkokung des Pechs auf etwa 700 bis 1 000 °C erhitzt wird. Der Graphitkörper enthält. in den Poren einen Pechkoks, durch welchen die Permeabilität des Körpers gesenkt und die mechanische Belastbarkeit verbessert wird.To produce the graphite blocks, petroleum coke, anthracite and other substances consisting essentially of carbon are mixed together with a carbonizable binder, the mixture is formed into blocks and the blocks in a first stage for carbonizing the binder to about 1,000 ° C. and heated to 2600 to 3000 ° C in a second stage. The use of raw materials with upstream structural elements and the use of higher temperatures result in graphite blocks with a comparatively high thermal conductivity and a low specific electrical resistance. According to the invention, the thermal conductivity of the blocks is 80 to 120 W / m-K and the specific electrical resistance is 6 to 13 µΩm. The comparatively low resistance brings about a substantial reduction in the voltage drop in the lining, in which less Joule heat is generated accordingly. Due to the high thermal conductivity of the graphite blocks, larger temperature differences in the lining, which may impair the service life of the cell, are excluded, and in conjunction with the thermal insulation layer, a greater outflow of energy from the molten electrolyte is avoided. The effect is particularly favorable for linings, the graphite blocks with a thermal conductivity of 100 to 120 W / m - K and a spec. electrical resistance from 6 to 10 pnm included. It was finally found that in order to achieve a long service life for the electrolytic cell, the open pore volume of the graphite blocks accessible to the melt must also be reduced. The accessible pore volume should be at most 22% and, according to a preferred embodiment of the invention, at most 18%. It is known to impregnate carbon and graphite blocks intended for lining the tubs of electrolysis cells with furfurol or furfuryl alcohol and to coke the impregnating agent in situ (US Pat. No. 3,616,045). The accessible pore volume is reduced by this method, but the size of the accessible pore volume of these blocks is not known. In order to reduce the accessible pore volume, a method is particularly suitable in which the porous graphite body is impregnated with coal tar pitch or petroleum pitch and heated to about 700 to 1,000 ° C. for coking the pitch. The graphite body contains. a pitch coke in the pores, through which the permeability of the body is reduced and the mechanical resilience is improved.
Die die Auskleidung der Wanne bildenden Graphitblöcke sind zweckmäßig fugenlos miteinander verklebt, wobei unter dem Begriff « fugenlos Fugen mit einer Breite von höchstens 1 mm zu verstehen sind. Als Fugenkitt eignen sich besonders die in der EP 0 027 534 beschriebenen plastischen Massen. Die üblichen Fugen mit einer Breite von 20 mm und mehr sind Schwachstellen der Auskleidung, die durch thermische Spannungen oder eindiffundierende Schmelze leicht zerstört werden.The graphite blocks forming the lining of the trough are expediently glued to one another without any joints, the term “seamless joints being understood to have a width of at most 1 mm. The plastic compounds described in EP 0 027 534 are particularly suitable as joint cement. The usual joints with a width of 20 mm and more are weak points in the lining, which are easily destroyed by thermal stress or by diffusing melt.
Die Erfindung wird im folgenden anhand von Beispielen und Zeichnungen erläutert. Es zeigen
Figur 1 einen Längsschnitt durch eine Elektrolysezelle zur Gewinnung von Aluminium,- Figur 2 den Spannungsabfall verschiedener Auskleidungen als Funktion der Betriebszeit.
- FIG. 1 shows a longitudinal section through an electrolysis cell for extracting aluminum,
- Figure 2 shows the voltage drop of various liners as a function of operating time.
In Fig. 1 ist die Stahlwanne mit 1 bezeichnet. Die wärmeisolierende Schicht besteht aus den Teilschichten 2 und 3, deren Wärmeleitfähigkeit 0,1 bis 0,2 W/m - K und 0,8 bis 1,2 W/m - K beträgt. Das Verhältnis der Wärmedurchgangswiderstände der Schichten ist etwa 0.05. In die auf der Schicht 3 aufliegenden Graphitblöcken 4 sind Strombarren oder Schienen 5 eingelassen. Die Wärmeleitfähigkeit der Graphitblöcke beträgt 80 bis 120 W/m - K, der spezifische elektrische Widerstand 6 bis 13 µΩm und das zugängliche Porenvolumen höchstens 22 %. Das Dickenverhältnis der Graphitschicht 4 zur Summe der Schichten 2 und 3 ist 1,5 bis 1,6. Die Graphitblöcke 4 kleiden den Wannenboden vollständig aus, die Wannenseitenflächen sind durch den Block 6 abgeschirmt, der aus Graphit oder aus Kohlenstoff besteht. Die eigentliche Kathode ist die Aluminiumschicht 7. Die Anoden 9 mit der anodischen Stromzuführung 10 tauchen in den schmelzflüssigen Elektrolyten 8 ein und sind durch die vorwiegend aus Tonerde bestehende Kruste 11 gegen den Angriff von Luftsauerstoff geschützt.In Fig. 1 the steel trough is designated 1. The heat-insulating layer consists of the sub-layers 2 and 3, the thermal conductivity of which is 0.1 to 0.2 W / m - K and 0.8 to 1.2 W / m - K. The ratio of the thermal resistance of the layers is about 0.05. Current bars or
Der bei der Inbetriebnahme einer Zelle zur Gewinnung von Aluminium gemessene Spannungsabfall, ist im wesentlichen eine Funktion der Auskleidung. Der Spannungsabfall einer Auskleidung aus Kohlenstoffblöcken beträgt etwa 400 mV, einer Auskleidung aus kohlenstoffgebundenen Graphitblöcken etwa 300 mV und einer erfindungsgemäßen Auskleidung aus Graphitblöcken nur etwa 200 mV. Die Temperatur der Wanne beträgt für diese Auskleidungen und einer wärmeisolierenden Schicht, gebildet aus zwei Teilschichten A und B mit der Wärmeleitfähigkeit 1,0 und 0,1 W/m - K etwa 150 bis 50 °C (Tabelle 1).
Die geringen Energieverluste der erfindungsgemäßen Auskleidung lassen sich naturgemäß nur realisieren, wenn die bei Inbetriebnahme der Elektrolysezelle gemessenen Kenngrößen sich während des Betriebs der Zelle nicht oder nur geringfügig ändern. In der Fig. 2 ist die Zunahme des Spannungsabfalls als Funktion der Betriebszeit dargestellt ; A ist eine aus Kohlenstoffblöcken bestehende Auskleidung, B eine Auskleidung aus kohlenstoffgebundenem Graphit und C eine aus Graphitblöcken. Der Anstieg des Spannungsabfalls mit der Betriebszeit wird im wesentlichen durch die zunehmende Zersetzung und Zerstörung der Auskleidung verursacht. Der ursprüngliche Vorteil erfindungsgemäßer Auskleidungen bleibt beim Betrieb der Elektrolysezelle nicht nur erhalten, sondern vergrößert sich mit fortschreitender Betriebsdauer.The low energy losses of the lining according to the invention can of course only be realized if the parameters measured when the electrolysis cell is started up do not change or change only slightly during the operation of the cell. 2 shows the increase in the voltage drop as a function of the operating time; A is a liner made of carbon blocks, B is a liner made of carbon-bonded graphite and C is one made of graphite blocks. The increase in the voltage drop with the operating time is essentially caused by the increasing decomposition and destruction of the lining. The original advantage of linings according to the invention not only remains when the electrolysis cell is in operation, but also increases as the operating time progresses.
Claims (5)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3327230 | 1983-07-28 | ||
| DE19833327230 DE3327230A1 (en) | 1983-07-28 | 1983-07-28 | LINING FOR ELECTROLYSIS PAN FOR PRODUCING ALUMINUM |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0132647A2 EP0132647A2 (en) | 1985-02-13 |
| EP0132647A3 EP0132647A3 (en) | 1985-03-13 |
| EP0132647B1 true EP0132647B1 (en) | 1987-03-04 |
Family
ID=6205144
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP84107810A Expired EP0132647B1 (en) | 1983-07-28 | 1984-07-05 | Lining for an electrolytic cell for the production of aluminium |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4589967A (en) |
| EP (1) | EP0132647B1 (en) |
| JP (1) | JPS6052589A (en) |
| AU (1) | AU565836B2 (en) |
| CA (1) | CA1248495A (en) |
| DE (1) | DE3327230A1 (en) |
| NO (1) | NO161008C (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8522138D0 (en) * | 1985-09-06 | 1985-10-09 | Alcan Int Ltd | Linings for aluminium reduction cells |
| NO157462C (en) * | 1985-10-24 | 1988-03-23 | Hydro Aluminium As | LAMINATED CARBON CATHOD FOR CELLS-MELT-ELECTROLYTIC ALUMINUM PREPARATION. |
| DE4201490A1 (en) * | 1992-01-21 | 1993-07-22 | Otto Feuerfest Gmbh | FIRE-RESISTANT MATERIAL FOR ELECTROLYSIS OVENS, METHOD FOR THE PRODUCTION AND USE OF THE FIRE-RESISTANT MATERIAL |
| FR2789093B1 (en) | 1999-02-02 | 2001-03-09 | Carbone Savoie | GRAPHITE CATHODE FOR ALUMINUM ELECTROLYSIS |
| FR2789091B1 (en) | 1999-02-02 | 2001-03-09 | Carbone Savoie | GRAPHITE CATHODE FOR ALUMINUM ELECTROLYSIS |
| DK2042211T3 (en) * | 2001-06-29 | 2019-06-11 | Coloplast As | catheter assembly |
| US7126928B2 (en) * | 2003-08-05 | 2006-10-24 | Qualcomm Incorporated | Grant, acknowledgement, and rate control active sets |
| FR2900665B1 (en) * | 2006-05-03 | 2008-06-27 | Carbone Savoie Soc Par Actions | ALUMINUM OBTAINING ELECTROLYSIS TANK |
| US20090236233A1 (en) * | 2008-03-24 | 2009-09-24 | Alcoa Inc. | Aluminum electrolysis cell electrolyte containment systems and apparatus and methods relating to the same |
| UA111247C2 (en) * | 2011-11-11 | 2016-04-11 | Сгл Карбон Се | METHOD OF MEASURING SURFACES OF SURFACES IN OPERATING ALUMINUM ELECTROLYZERS |
| RU2668615C2 (en) * | 2012-12-13 | 2018-10-02 | СГЛ КФЛ ЦЕ Гмбх | Side bock for electrolytic cell wall for reducing aluminum |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1146259B (en) * | 1960-10-28 | 1963-03-28 | Aluminium Ind Ag | Process for lining the walls of the cathode trough of an aluminum electrolysis cell and cathode trough manufactured using this process |
| US3434957A (en) * | 1966-02-18 | 1969-03-25 | Arthur F Johnson | Aluminum reduction cell with aluminum and refractory layered bottom construction |
| US3616045A (en) * | 1969-02-17 | 1971-10-26 | Tatabanyai Aluminiumkoho | Process for increasing the strength and electrical conductivity of graphite or carbon articles and/or for bonding such articles to each other to ceramic articles or to metals |
| JPS4941006B1 (en) * | 1970-03-16 | 1974-11-06 | ||
| US4046650A (en) * | 1970-03-16 | 1977-09-06 | Sumitomo Aluminum Smelting Co., Ltd. | Carbon block for cathodes of aluminum |
| DE2105247C3 (en) * | 1971-02-04 | 1980-06-12 | Schweizerische Aluminium Ag, Zuerich (Schweiz) | Furnace for the fused aluminum electrolysis |
| US3723286A (en) * | 1971-11-08 | 1973-03-27 | Kaiser Aluminium Chem Corp | Aluminum reduction cell |
| JPS5332811A (en) * | 1976-09-07 | 1978-03-28 | Mitsubishi Keikinzoku Kogyo | Reduction of heat radiation in the aluminium electrolytic cell |
| DE2942469C2 (en) * | 1979-10-20 | 1983-09-15 | Sigri Elektrographit Gmbh, 8901 Meitingen | Contact mass containing carbon |
| CH653711A5 (en) * | 1981-04-22 | 1986-01-15 | Alusuisse | ELECTROLYSIS PAN. |
| GB2103657A (en) * | 1981-07-18 | 1983-02-23 | British Aluminium Co Ltd | Electrolytic cell for the production of aluminium |
| US4411758A (en) * | 1981-09-02 | 1983-10-25 | Kaiser Aluminum & Chemical Corporation | Electrolytic reduction cell |
-
1983
- 1983-07-28 DE DE19833327230 patent/DE3327230A1/en active Granted
-
1984
- 1984-06-08 NO NO842315A patent/NO161008C/en unknown
- 1984-07-05 EP EP84107810A patent/EP0132647B1/en not_active Expired
- 1984-07-09 US US06/628,807 patent/US4589967A/en not_active Expired - Fee Related
- 1984-07-13 CA CA000458820A patent/CA1248495A/en not_active Expired
- 1984-07-19 AU AU30862/84A patent/AU565836B2/en not_active Ceased
- 1984-07-27 JP JP59157138A patent/JPS6052589A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0132647A2 (en) | 1985-02-13 |
| US4589967A (en) | 1986-05-20 |
| NO161008B (en) | 1989-03-13 |
| AU565836B2 (en) | 1987-10-01 |
| DE3327230A1 (en) | 1985-02-07 |
| JPS6052589A (en) | 1985-03-25 |
| EP0132647A3 (en) | 1985-03-13 |
| DE3327230C2 (en) | 1990-08-23 |
| CA1248495A (en) | 1989-01-10 |
| NO842315L (en) | 1985-01-29 |
| NO161008C (en) | 1989-06-21 |
| AU3086284A (en) | 1985-01-31 |
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