EP2989235B9 - Cathode block having a slot with varying depth and a securing system - Google Patents

Cathode block having a slot with varying depth and a securing system Download PDF

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Publication number
EP2989235B9
EP2989235B9 EP14721300.3A EP14721300A EP2989235B9 EP 2989235 B9 EP2989235 B9 EP 2989235B9 EP 14721300 A EP14721300 A EP 14721300A EP 2989235 B9 EP2989235 B9 EP 2989235B9
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EP
European Patent Office
Prior art keywords
cathode block
cathode
groove
busbar
recess
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Active
Application number
EP14721300.3A
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German (de)
French (fr)
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EP2989235A1 (en
EP2989235B1 (en
Inventor
Frank Hiltmann
Markus Pfeffer
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Tokai Cobex GmbH
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Cobex GmbH
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Publication date
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Priority to PL19166841T priority Critical patent/PL3546620T3/en
Priority to EP19166841.7A priority patent/EP3546620B1/en
Priority to PL14721300T priority patent/PL2989235T3/en
Publication of EP2989235A1 publication Critical patent/EP2989235A1/en
Application granted granted Critical
Publication of EP2989235B1 publication Critical patent/EP2989235B1/en
Publication of EP2989235B9 publication Critical patent/EP2989235B9/en
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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
    • 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
    • C25C3/16—Electric current supply devices, e.g. bus bars

Definitions

  • the present invention relates to a cathode block for an aluminum electrolytic cell, its use and a cathode arrangement comprising it.
  • Electrolysis cells are used, for example, for the electrolytic production of aluminum, which is usually carried out industrially using the Hall-Heroult process.
  • a melt composed of aluminum oxide and cryolite is electrolyzed.
  • the cryolite, Na 3 [AlF 6 ] serves to lower the melting point from 2,045 ° C for pure aluminum oxide to approximately 950 ° C for a mixture containing cryolite, aluminum oxide and additives such as aluminum fluoride and calcium fluoride.
  • the electrolytic cell used in this method has a cathode base which is composed of a large number of, for example, up to 28 adjacent cathode blocks that form the cathode.
  • the spaces between the cathode blocks are usually filled with a carbon-containing ramming mass in order to seal the cathode from molten components of the electrolytic cell and to compensate for mechanical stresses that occur during commissioning of the electrolytic cell.
  • the cathode blocks are typically composed of a carbon-containing material such as graphite.
  • Grooves are usually provided on the undersides of the cathode blocks, in each of which at least one or two busbars are arranged, through which the current supplied via the anodes is dissipated.
  • the spaces between the individual walls of the cathode blocks delimiting the grooves and the busbars are often filled with cast iron to electrically and mechanically connect the busbars to the cathode blocks by covering the busbars with cast iron.
  • the aluminum formed is deposited below the electrolyte layer, i.e. as an intermediate layer between the top of the cathode and the electrolyte layer, due to its greater density compared to that of the electrolyte.
  • the aluminum oxide dissolved in the melt is broken down into aluminum and oxygen by the flow of electric current.
  • the layer of liquid aluminum is the actual cathode, as aluminum ions are reduced to elemental aluminum on its surface.
  • the term cathode is not understood below to mean the cathode from an electrochemical point of view, i.e. the layer made of liquid aluminum, but rather the component that forms the electrolysis cell base, for example composed of one or more cathode blocks.
  • a major disadvantage of the cathode arrangements used in the Hall-Heroult process is their comparatively low wear resistance, which is manifested by erosion of the cathode block surfaces during electrolysis. Due to an inhomogeneous current distribution within the cathode blocks, the removal of the cathode block surfaces does not occur evenly over the length of the cathode blocks, but to an increased extent at the cathode block ends, so that the surfaces of the cathode blocks change to a W-shaped profile after a certain period of electrolysis. Through Due to the uneven erosion of the cathode block surfaces, the service life of the cathode blocks is limited by the areas with the greatest erosion.
  • the WO 2007/118510 A2 A cathode block has been proposed, the groove of which is intended to accommodate one or more busbars, based on the length of the cathode block, has a greater depth in the middle than at the ends of the cathode block.
  • the busbar(s) is or are covered in a conventional manner with cast iron, this covering being carried out by pouring liquid cast iron into the space between the groove and the busbar(s).
  • such a cathode block has disadvantages.
  • the cathode block is comparatively large Subjected to temperature changes, which lead to expansion or shrinkage of the cast iron and the busbar (s) relative to the cathode block. This effect of expansion or shrinkage can be intensified by temperature gradients that occur. In the following, when “large temperature change(s)” is mentioned, it is understood that one or both of the mentioned effects, ie expansion/shrinkage or temperature gradient, is/are present.
  • the cast iron and the busbar(s) expand relative to the cathode block when the temperature increases, whereas they shrink relative to the cathode block when the temperature decreases.
  • the electrical contact between the busbar, cast iron and cathode block deteriorates, which leads to increased electrical resistance of the arrangement and thus to poor energy efficiency of the electrolysis process.
  • the busbar or busbars are movable in both the vertical and horizontal directions before pouring the liquid cast iron into the space between the groove and the busbar(s), so that they move during pouring of the liquid cast iron and during the subsequent cooling and solidification of the cast iron can move uncontrollably in the groove, which can also lead to uneven electrical contact between the busbar, cast iron and cathode block. This also leads to increased electrical resistance of the arrangement and thus to poor energy efficiency of the electrolysis process.
  • Ramming compound can also be used instead of cast iron. Ramming compounds based on anthracite, graphite and any mixtures thereof can be used as ramming compound. A graphite-based ramming compound is preferably used.
  • DE 2 405 461 and EP 0 052 577 describe a carbon-based cathode block having a groove in whose side walls there is a recess.
  • the object of the present invention is therefore to provide a cathode block that is particularly suitable for use in an aluminum electrolytic cell, with which a substantially homogeneous vertical current distribution is achieved over the length of the cathode block when the electrolytic cell is operated, which also has an inserted busbar coated with cast iron ( n) low and especially over even with large temperature changes longer operating times, permanently low specific electrical resistance and low contact resistance between the cast iron-coated busbar and the cathode block, and which is stable against mechanical damage, such as cracking, even with large temperature changes even with the cast iron-coated busbar(s) inserted.
  • Ramming compound can also be used instead of cast iron.
  • a cathode block for an aluminum electrolysis cell based on carbon and / or graphite having at least one groove extending in the longitudinal direction of the cathode block for receiving at least one busbar, at least one of the at least one groove having a , seen over the length of the cathode block, has varying depth, wherein in the wall of the cathode block delimiting at least one groove with varying depth, at least one recess having a semicircular, triangular, rectangular or trapezoidal cross-section is provided, which is at least in the longitudinal direction of the cathode block extends horizontally approximately over the entire length of the at least one groove.
  • a recess extending horizontally in the longitudinal direction of the cathode block is understood to mean that the recess extends parallel to the longitudinal plane of the cathode block.
  • a parallel extension is understood to mean that the recess at each of its points has an angle of less than 5°, particularly preferably less than 2°, very particularly preferably less than 1°, most preferably less than 0.5°, and most preferably of less than 0.1° to the longitudinal plane of the cathode block.
  • the term longitudinal plane is understood to mean the plane which extends in the direction of the longitudinal axis of the cathode block and runs parallel to the surface of the side of the cathode block opposite the groove.
  • a recess in contrast to mere surface roughness, is understood to mean a recess which, based on the surface of the wall delimiting the groove, has a depth of at least 0.5 mm and preferably at least 2 mm.
  • a cathode block is created, which has a low electrical resistance and low contact resistance even with the busbar inserted into the groove and coated with cast iron.
  • the use of a groove with a variable depth in the longitudinal direction of the cathode block achieves such a uniform current density distribution on the cathode block surface that, during the operation of the electrolytic cell comprising the cathode block, excessive removal of cathode block material is effectively avoided in those areas where, when using a Cathode block with the same groove depth in the longitudinal direction of the cathode block would have a high local current density.
  • the groove depth By appropriately adjusting the groove depth, the current density distribution can be modified and evened out within broad limits.
  • the cathode block has a recess in its groove that extends horizontally in the longitudinal direction of the cathode block, a vertical fixation of the cast iron-coated busbar in the groove of the cathode block is achieved, which, however, allows a certain movement in the horizontal direction of the cathode block Cathode blocks allow.
  • At least one of the at least one groove and preferably all of the grooves with varying depth has or have a smaller depth at their longitudinal ends than in their center(s). In this way, an even distribution of the electrical current supplied during electrolysis operation is achieved over the entire length of the cathode block, thereby avoiding excessive electrical current density at the longitudinal ends of the cathode block and thus premature wear at the ends of the cathode block.
  • Such a uniform current density distribution over the length of the cathode block also avoids movements in the aluminum melt caused by interaction of electromagnetic fields during electrolysis, which makes it possible to arrange the anode at a lower height above the surface of the aluminum melt. This reduces the electrical resistance between the anode and the aluminum melt and increases the energy efficiency of the fusion electrolysis carried out.
  • Another particular advantage of this embodiment is that with this configuration of the groove, the busbar(s) provided in the recess of the groove, possibly covered with cast iron, expands in the horizontal direction during and after the increase in temperature that occurs when the electrolytic cell is put into operation or expand, as a result of which the busbar(s) are pressed against the bottom wall of the cathode block delimiting the groove at this point, whereby the contact resistance between the cast iron-coated busbar and the cathode block is reduced.
  • the depth of at least one of the at least one groove with varying depth, viewed in the longitudinal direction of the cathode block preferably increases at least substantially monotonically from one longitudinal end to the center of the cathode block and increases from the center to the other longitudinal end End of the cathode block at least substantially monotonously, so that, seen in the longitudinal section of the cathode block, an at least substantially triangular groove results.
  • the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each of the two side walls having at least one depression which extends horizontally in the longitudinal direction of the cathode block.
  • the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each side wall having exactly one recess which extends horizontally in the longitudinal direction of the cathode block.
  • a particularly good vertical fixation of the busbar in the groove is achieved with comparatively little manufacturing effort, while at the same time sufficiently high mobility in the horizontal direction in order to reliably avoid the occurrence of shear stresses due to the different thermal expansion coefficients of cast iron, busbar and cathode block in the event of large temperature changes .
  • the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each side wall having two depressions, each of which extends horizontally in the longitudinal direction of the cathode block.
  • the cathode block can have two grooves arranged on the same side of the cathode block, both grooves having the same dimensions and the delimiting walls of which each comprise a bottom wall and two side walls, each side wall having a depression which extends horizontally in the longitudinal direction of the cathode block, or wherein each side wall has two depressions which extend horizontally in the longitudinal direction of the cathode block.
  • the cathode block can also only comprise one groove.
  • the busbar which may be coated with cast iron
  • the at least one recess and particularly preferably each of the at least one recess extends continuously at least 60%, preferably over at least 80%, particularly preferably over at least 90%, very particularly preferably over at least 95% of the length of the at least one groove, which is not part of the invention.
  • the at least one depression extends at least approximately over the entire length of the at least one groove.
  • At least one of the at least one depression and particularly preferably each of the at least one depression has a depth of 0.5 mm to 40 mm, preferably of 2 mm to 30 mm and particularly preferably of 5 mm to 20 mm having.
  • At least one of the at least one recess and particularly preferably each of the at least one recess has an opening width, based on the height of the cathode block, of 2 mm to 40 mm, preferably of 5 mm to 30 mm and particularly preferably of 10 mm to 20 mm.
  • the at least one depression can have any polygonal or curved cross section.
  • Good results with regard to good engagement of the cast iron casing in the at least one recess and at the same time with regard to reliable and unproblematic filling of the recess with cast iron during casting are achieved in particular if at least one of the at least one recess and particularly preferably each of the at least one recess an at least essentially semicircular, triangular, rectangular or trapezoidal, preferably semicircular, triangular, rectangular or trapezoidal, cross-section.
  • the at least one recess extends at least substantially vertically, preferably vertically, into the wall of the cathode block delimiting the at least one groove.
  • the at least one depression - viewed in the depth direction of the groove - is delimited at each of its ends by a transition region between the depression and a section of the groove wall adjacent thereto. If this transition region is designed at an angle, the angle between the adjacent section of the groove wall and the wall of the recess, viewed from the inside of the cathode block, is preferably 90 degrees to 160 degrees, particularly preferably 90 degrees to 135 degrees and most preferably 100 degrees to 120 Degree.
  • the radius of curvature of the transition region is preferably a maximum of 50 mm, particularly preferably a maximum of 20 mm and most preferably a maximum of 5 mm.
  • the present invention relates to a cathode arrangement which contains at least one previously described cathode block, wherein at least one busbar is provided in at least one of the at least one groove with varying depth of the at least one cathode block, which has at least partially a casing made of cast iron, which at least partially in which engages at least one depression.
  • the section of the cast iron casing which engages in the at least one recess is designed to be complementary to the recess.
  • a particularly good positive engagement of the cast iron casing in the recess and thus a particularly effective mechanical fastening of the cast iron casing and the busbar connected to it to the cathode block can be achieved, which nevertheless results in the avoidance of shear stresses between the cast iron, busbar and cathode block allows sufficient mobility of the busbar in the horizontal direction due to large temperature changes.
  • the cast iron casing engages into the at least one recess over at least 50%, more preferably over at least 80%, particularly preferably over at least 90%, very particularly preferably over at least 95% and most preferably over at least substantially its entire length.
  • the advantages described above are achieved to a particularly high extent.
  • the section of the casing which engages in the at least one recess and possibly the busbar covered by it is at least 70%, preferably at least 80%, particularly preferably at least 90%, completely particularly preferably fills at least 95% and most preferably 100% of the depression.
  • the cathode block of the cathode arrangement has a groove with at least essentially rectangular, preferably a rectangular, cross-section and one or two adjacent busbar(s) are inserted into the groove, the space between the groove and the busbar(s) being filled with cast iron in such a way that the cast iron is at least substantially above it entire length engages in at least one recess.
  • a further subject of the present invention is a cathode which comprises at least one previously described cathode block or at least one previously described cathode arrangement.
  • the present invention further relates to the use of a previously described cathode block, a previously described cathode arrangement or a previously described cathode for carrying out fusion electrolysis for the production of metal, preferably for the production of aluminum.
  • a further subject of the present invention is a cathode arrangement which comprises at least one cathode block described above.
  • the present invention further relates to the use of a previously described cathode block, a previously described cathode arrangement for carrying out fusion electrolysis for the production of metal, preferably for the production of aluminum.
  • a section of an aluminum electrolysis cell 10 is shown in cross section with a cathode arrangement 12, which simultaneously forms the bottom of a trough for an aluminum melt 14 generated during operation of the electrolysis cell 10 and for a cryolite-aluminum oxide melt 16 located above the aluminum melt 14.
  • An anode 18 is in contact with the cryolite-alumina melt 16.
  • the trough formed by the lower part of the aluminum electrolysis cell 10 is formed by an in the Fig. 1 lining made of carbon and/or graphite, not shown.
  • the cathode arrangement 12 comprises a plurality of cathode blocks 20, each of which is connected to one another via a ramming mass 24 inserted into a ramming mass joint 22 arranged between the cathode blocks 20.
  • a cathode block 20 comprises two grooves 26 arranged on its underside with a rectangular, namely essentially rectangular cross section, in each Groove 26 each accommodates a busbar 28 made of steel with a rectangular cross section.
  • the grooves 26 are each delimited by two side walls 32 and a bottom wall 34 of the cathode block 20, with a depression 36 with an approximately semicircular cross section extending essentially vertically into the side wall 32 being provided in each of the side walls 32.
  • Each depression 36 is delimited by an upper and a lower transition region 37 of the cathode block 20.
  • the transition regions 37 are formed at an angle with an angle ⁇ between the adjacent section of the groove wall and the wall of the recess of 90 degrees.
  • the space between the busbar 28 and the groove 26 is filled with cast iron 38.
  • the cast iron 38 forms a casing 39 for the busbar 28 and is in a material connection with the busbar 28.
  • the cast iron 38 accommodated in the recesses 36 forms a positive connection with the material of the cathode block 20 delimiting the recess 36, which prevents the busbar 28 connected to the cast iron 38 from moving in the direction of the arrow 40.
  • the cross section of the cathode arrangement 12 is shown at a longitudinal end of the cathode block 20.
  • the depth of the groove 26 of the cathode block 20 varies over the length of the groove 26.
  • the groove cross section in the area of the center of the groove 26 - based on the longitudinal direction of the cathode block - is in the Fig. 1 indicated by a dashed line 42.
  • the difference between the groove depth at the longitudinal ends of the groove 26 and in the center of the groove 26 - based on the longitudinal direction of the cathode block - is approximately 5 cm in the present exemplary embodiment.
  • the depth of the groove 26 at the two longitudinal ends of the groove 26 is approximately 16 cm, whereas the depth the groove 26 in which - based on the longitudinal direction of the cathode block - the center of the groove 26 is approximately 21 cm.
  • the width 44 of each groove 26 is essentially constant over the entire groove length and is approximately 15 cm, whereas the width 46 of the cathode blocks 20 is each approximately 42 cm.
  • each anode 18 and several cathode blocks 20 are arranged one above the other in such a way that each anode 18 covers two adjacent cathode blocks 20 in width and covers half of a cathode block 20 in length, with two adjacent anodes 18 each having the length of one Cover cathode block 20.
  • the Fig. 2 shows the one in the Fig. 1 Cathode block 20 shown in longitudinal section.
  • the groove 26 viewed in its longitudinal section tapers towards the center of the cathode block 20 in the shape of a triangle, thereby ensuring a substantially uniform electrical vertical current density over the entire cathode length.
  • the depression 36 runs like in the Fig. 2 indicated by the correspondingly marked line parallel to the horizontal direction, ie parallel to the surface of the side of the cathode block 20 opposite the groove 26.
  • busbar 28 is designed in the form of a bar in the present exemplary embodiment and has a rectangular longitudinal section, so that between the busbar and the groove bottom 34 there is a space that increases towards the middle of the groove 26, which is either through cast iron 38 or through Additional metal plates connected to the busbar 28 can be filled.
  • Fig. 5a to d exemplary depressions 36 which are provided in a groove 26 of a cathode block 20 according to the invention, in cross section.
  • the depressions 36 each have a substantially semicircular cross section ( Fig. 5a ), a substantially trapezoidal cross-section ( Fig. 5b ) or a substantially triangular cross section ( Fig. 5c ) on.
  • the angle ⁇ of the transition regions 37 between the wall of the recess 36 and the adjacent section of the groove wall 32, seen from the inside of the cathode block 20, is in Fig. 5a about 90 degrees, in the Fig. 5b about 120 degrees and in the Fig. 5c about 125 degrees.
  • the Fig. 5a about 90 degrees
  • Fig. 5b about 120 degrees
  • Fig. 5c about 125 degrees.
  • FIG. 5d shows an embodiment in which several as in the Fig. 5c shown depressions 36 with a triangular cross section are arranged one after the other in the depth direction of the groove 26 in order to ensure a particularly reliable holding of an inserted busbar 28.
  • the transition areas 48 between two adjacent depressions 36 have an angle ⁇ of approximately 70 degrees between the walls of two adjacent depressions 36, viewed from the inside of the cathode block 20. The ones in the Fig.
  • the depressions 36 shown each extend vertically into the side wall 32 of the cathode block 20 delimiting the groove 26, so that they form a fixation with cast iron accommodated in the depressions 36, which is effective in the depth direction of the groove 26 and prevents unwanted movement of the busbar 28 parallel to the depth direction of the groove 26 after the busbar 28 has been cast with cast iron 38 is prevented, but a horizontal movement of the cast iron-coated busbar - for example as a result of an expansion of the cast iron-coated busbar as a result of a large temperature change - is permitted.

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Description

Die vorliegende Erfindung betrifft einen Kathodenblock für eine Aluminium-Elektrolysezelle, dessen Verwendung sowie eine diesen umfassende Kathodenanordnung.The present invention relates to a cathode block for an aluminum electrolytic cell, its use and a cathode arrangement comprising it.

Elektrolysezellen werden beispielsweise zur elektrolytischen Herstellung von Aluminium eingesetzt, welche industriell üblicherweise nach dem Hall-Heroult-Verfahren durchgeführt wird. Bei dem Hall-Heroult-Verfahren wird eine aus Aluminiumoxid und Kryolith zusammengesetzte Schmelze elektrolysiert. Dabei dient der Kryolith, Na3[AlF6], dazu, den Schmelzpunkt von 2.045 °C für reines Aluminiumoxid auf ca. 950 °C für eine Kryolith, Aluminiumoxid und Zusatzstoffe, wie Aluminiumfluorid und Calciumfluorid, enthaltende Mischung zu senken.Electrolysis cells are used, for example, for the electrolytic production of aluminum, which is usually carried out industrially using the Hall-Heroult process. In the Hall-Heroult process, a melt composed of aluminum oxide and cryolite is electrolyzed. The cryolite, Na 3 [AlF 6 ], serves to lower the melting point from 2,045 ° C for pure aluminum oxide to approximately 950 ° C for a mixture containing cryolite, aluminum oxide and additives such as aluminum fluoride and calcium fluoride.

Die bei diesem Verfahren eingesetzte Elektrolysezelle weist einen Kathodenboden auf, der aus einer Vielzahl von beispielsweise bis zu 28 aneinander angrenzenden, die Kathode ausbildenden Kathodenblöcken zusammengesetzt ist. Dabei sind die Zwischenräume zwischen den Kathodenblöcken üblicherweise mit einer kohlenstoffhaltigen Stampfmasse gefüllt, um die Kathode gegenüber schmelzflüssigen Bestandteilen der Elektrolysezelle abzudichten, und, um mechanische Spannungen, welche während der Inbetriebnahme der Elektrolysezelle auftreten, zu kompensieren. Um den bei dem Betrieb der Zelle herrschenden thermischen und chemischen Bedingungen standzuhalten, sind die Kathodenblöcke üblicherweise aus einem kohlenstoffhaltigen Material, wie Graphit, zusammengesetzt. An den Unterseiten der Kathodenblöcke sind üblicherweise jeweils Nuten vorgesehen, in denen jeweils wenigstens eine oder zwei Stromschiene angeordnet sind, durch welche der über die Anoden zugeführte Strom abgeführt wird. Dabei sind die Zwischenräume zwischen den einzelnen die Nuten begrenzenden Wänden der Kathodenblöcke und den Stromschienen häufig mit Gusseisen ausgegossen, um durch die dadurch hergestellte Umhüllung der Stromschienen mit Gusseisen die Stromschienen elektrisch und mechanisch mit den Kathodenblöcken zu verbinden. Etwa 3 bis 5 cm oberhalb der auf der Kathodenoberseite befindlichen, üblicherweise 15 bis 50 cm hohen, Schicht aus flüssigem Aluminium ist eine, insbesondere aus einzelnen Anodenblöcken ausgebildete, Anode angeordnet, zwischen der und der Oberfläche des Aluminiums sich der Elektrolyt, also die Aluminiumoxid und Kryolith enthaltende Schmelze, befindet. Während der bei etwa 1.000 °C durchgeführten Elektrolyse setzt sich das gebildete Aluminium aufgrund seiner im Vergleich zu der des Elektrolyten größeren Dichte unterhalb der Elektrolytschicht ab, also als Zwischenschicht zwischen der Oberseite der Kathode und der Elektrolytschicht. Bei der Elektrolyse wird das in der Schmelze gelöste Aluminiumoxid durch elektrischen Stromfluss zu Aluminium und Sauerstoff aufgespalten. Elektrochemisch gesehen handelt es sich bei der Schicht aus flüssigem Aluminium um die eigentliche Kathode, da an dessen Oberfläche Aluminiumionen zu elementarem Aluminium reduziert werden. Nichtsdestotrotz wird nachfolgend unter dem Begriff Kathode nicht die Kathode aus elektrochemischer Sicht, also die Schicht aus flüssigem Aluminium verstanden, sondern das den Elektrolysezellenboden ausbildende, beispielsweise aus einem oder mehreren Kathodenblöcken zusammengesetzte Bauteil.The electrolytic cell used in this method has a cathode base which is composed of a large number of, for example, up to 28 adjacent cathode blocks that form the cathode. The spaces between the cathode blocks are usually filled with a carbon-containing ramming mass in order to seal the cathode from molten components of the electrolytic cell and to compensate for mechanical stresses that occur during commissioning of the electrolytic cell. To withstand the thermal and chemical conditions encountered during cell operation, the cathode blocks are typically composed of a carbon-containing material such as graphite. Grooves are usually provided on the undersides of the cathode blocks, in each of which at least one or two busbars are arranged, through which the current supplied via the anodes is dissipated. The spaces between the individual walls of the cathode blocks delimiting the grooves and the busbars are often filled with cast iron to electrically and mechanically connect the busbars to the cathode blocks by covering the busbars with cast iron. About 3 to 5 cm above the layer of liquid aluminum located on the top of the cathode, usually 15 to 50 cm high, is an anode, in particular formed from individual anode blocks, between which and the surface of the aluminum the electrolyte, i.e. the aluminum oxide and Melt containing cryolite. During the electrolysis, which is carried out at around 1,000 °C, the aluminum formed is deposited below the electrolyte layer, i.e. as an intermediate layer between the top of the cathode and the electrolyte layer, due to its greater density compared to that of the electrolyte. During electrolysis, the aluminum oxide dissolved in the melt is broken down into aluminum and oxygen by the flow of electric current. From an electrochemical point of view, the layer of liquid aluminum is the actual cathode, as aluminum ions are reduced to elemental aluminum on its surface. Nevertheless, the term cathode is not understood below to mean the cathode from an electrochemical point of view, i.e. the layer made of liquid aluminum, but rather the component that forms the electrolysis cell base, for example composed of one or more cathode blocks.

Ein wesentlicher Nachteil der bei dem Hall-Heroult-Verfahren eingesetzten Kathodenanordnungen ist deren vergleichsweise geringe Verschleißbeständigkeit, welche sich durch einen Abtrag der Kathodenblockoberflächen während der Elektrolyse manifestiert. Dabei erfolgt der Abtrag der Kathodenblockoberflächen aufgrund einer inhomogenen Stromverteilung innerhalb der Kathodenblöcke nicht gleichmäßig über die Länge der Kathodenblöcke, sondern in erhöhtem Ausmaß an den Kathodenblockenden, so dass sich die Oberflächen der Kathodenblöcke nach einer gewissen Elektrolysedauer zu einem W-förmigen Profil verändern. Durch den ungleichmäßigen Abtrag der Kathodenblockoberflächen wird die Nutzungsdauer der Kathodenblöcke durch die Stellen mit dem größten Abtrag begrenzt. Um diesem Problem zu begegnen, ist in der WO 2007/118510 A2 ein Kathodenblock vorgeschlagen worden, dessen zur Aufnahme einer oder mehrerer Stromschiene(n) bestimmte Nut, bezogen auf die Kathodenblocklänge, in der Mitte eine größere Tiefe aufweist als an den Kathodenblockenden. Dadurch wird bei dem Betrieb der Elektrolysezelle über die Kathodenblocklänge eine im Wesentlichen homogene vertikale Stromverteilung erreicht, wodurch der erhöhte Verschleiß an den Kathodenblockenden verringert wird und so die Lebensdauer der Kathode erhöht wird. Die Stromschiene(n) ist bzw. sind dabei in herkömmlicher Weise mit Gusseisen umhüllt, wobei diese Umhüllung durch Eingießen von flüssigem Gusseisen in den Zwischenraum zwischen der Nut und der bzw. den Stromschiene(n) erfolgt. Ein solcher Kathodenblock ist allerdings mit Nachteilen behaftet. Während und nach dem Eingießen des flüssigen Gusseisens in den Zwischenraum zwischen der Nut und der bzw. den Stromschiene(n), während und nach der Inbetriebnahme der den Kathodenblock umfassenden Elektrolysezelle sowie während und nach dem Abschalten der Elektrolysezelle und späterer Wiederinbetriebnahme ist der Kathodenblock vergleichsweise großen Temperaturänderungen ausgesetzt, welche zu einer Ausdehnung bzw. einem Schrumpf des Gusseisens und der Stromschiene(n) relativ zu dem Kathodenblock führen. Dieser Effekt der Ausdehnung bzw. des Schrumpfes kann durch auftretende Temperaturgradienten verstärkt werden. Im Folgenden wird, wenn von "großen Temperaturänderung(en)" gesprochen wird, verstanden, dass einer oder beide der genannten Effekte, d.h. Ausdehnung/Schrumpf oder Temperaturgradient, vorhanden ist/sind. Aufgrund der höheren Wärmeausdehnungskoeffizienten von Gusseisen und dem Material der Stromschiene(n) als dem Wärmeausdehnungskoeffizient des Kathodenblockmaterials dehnen sich das Gusseisen und die Stromschiene(n) bei einer Temperaturerhöhung nämlich relativ zu dem Kathodenblock aus, wohingegen diese bei einer Temperaturverringerung relativ zu dem Kathodenblock schrumpfen. Dadurch verschlechtert sich insbesondere bei üblichen Nuten mit rechteckiger Querschnittsform der elektrische Kontakt zwischen Stromschiene, Gusseisen und Kathodenblock, was zu einem erhöhten elektrischen Widerstand der Anordnung und damit zu einer schlechten Energieeffizienz des Elektrolyseverfahrens führt. Abgesehen davon ist die Stromschiene bzw. sind die Stromschienen vor dem Eingießen des flüssigen Gusseisens in den Zwischenraum zwischen der Nut und der bzw. den Stromschiene(n) sowohl in der vertikalen als auch in der horizontalen Richtung beweglich, so dass sich diese bei dem Eingießen des flüssigen Gusseisens und während dem nachfolgenden Abkühlen und Erstarren des Gusseisens unkontrolliert in der Nut bewegen können, was ebenfalls zu einem ungleichmäßigen elektrischen Kontakt zwischen Stromschiene, Gusseisen und Kathodenblock führen kann. Auch dies führt zu einem erhöhten elektrischen Widerstand der Anordnung und damit zu einer schlechten Energieeffizienz des Elektrolyseverfahrens. Anstelle des Gusseisens kann auch Stampfmasse verwendet werden. Als Stampfmasse können Stampfmassen auf Basis von Anthrazit, Graphit und beliebigen Mischungen davon eingesetzt werden. Vorzugsweise wird eine Stampfmasse auf Basis von Graphit verwendet. DE 2 405 461 und EP 0 052 577 beschreiben einen Kathodenblock auf Basis von Kohlenstoff aufweisend eine Nut, in deren Seitenwänden jeweils eine Ausnehmung vorhanden ist.A major disadvantage of the cathode arrangements used in the Hall-Heroult process is their comparatively low wear resistance, which is manifested by erosion of the cathode block surfaces during electrolysis. Due to an inhomogeneous current distribution within the cathode blocks, the removal of the cathode block surfaces does not occur evenly over the length of the cathode blocks, but to an increased extent at the cathode block ends, so that the surfaces of the cathode blocks change to a W-shaped profile after a certain period of electrolysis. Through Due to the uneven erosion of the cathode block surfaces, the service life of the cathode blocks is limited by the areas with the greatest erosion. To address this problem, the WO 2007/118510 A2 A cathode block has been proposed, the groove of which is intended to accommodate one or more busbars, based on the length of the cathode block, has a greater depth in the middle than at the ends of the cathode block. As a result, a substantially homogeneous vertical current distribution is achieved when the electrolytic cell is operated over the length of the cathode block, which reduces the increased wear on the cathode block ends and thus increases the service life of the cathode. The busbar(s) is or are covered in a conventional manner with cast iron, this covering being carried out by pouring liquid cast iron into the space between the groove and the busbar(s). However, such a cathode block has disadvantages. During and after pouring the liquid cast iron into the space between the groove and the busbar(s), during and after the commissioning of the electrolytic cell comprising the cathode block, as well as during and after switching off the electrolytic cell and later recommissioning, the cathode block is comparatively large Subjected to temperature changes, which lead to expansion or shrinkage of the cast iron and the busbar (s) relative to the cathode block. This effect of expansion or shrinkage can be intensified by temperature gradients that occur. In the following, when “large temperature change(s)” is mentioned, it is understood that one or both of the mentioned effects, ie expansion/shrinkage or temperature gradient, is/are present. Because of the higher thermal expansion coefficients of cast iron and the material of the busbar(s) than the thermal expansion coefficient of the cathode block material, the cast iron and the busbar(s) expand relative to the cathode block when the temperature increases, whereas they shrink relative to the cathode block when the temperature decreases. Through this Especially in the case of conventional grooves with a rectangular cross-sectional shape, the electrical contact between the busbar, cast iron and cathode block deteriorates, which leads to increased electrical resistance of the arrangement and thus to poor energy efficiency of the electrolysis process. Apart from this, the busbar or busbars are movable in both the vertical and horizontal directions before pouring the liquid cast iron into the space between the groove and the busbar(s), so that they move during pouring of the liquid cast iron and during the subsequent cooling and solidification of the cast iron can move uncontrollably in the groove, which can also lead to uneven electrical contact between the busbar, cast iron and cathode block. This also leads to increased electrical resistance of the arrangement and thus to poor energy efficiency of the electrolysis process. Ramming compound can also be used instead of cast iron. Ramming compounds based on anthracite, graphite and any mixtures thereof can be used as ramming compound. A graphite-based ramming compound is preferably used. DE 2 405 461 and EP 0 052 577 describe a carbon-based cathode block having a groove in whose side walls there is a recess.

Um ein Verschieben einer Stromschiene in der Nut eines Kathodenblocks zu verhindern oder zumindest zu erschweren, ist es in der WO 2012/107412 A2 vorgeschlagen worden, in der die mit einer Graphitfolie ausgekleideten Nut eines Kathodenblocks begrenzenden Wand wenigstens eine Vertiefung vorzusehen und nach dem Einsetzen der Stromschiene(n) in die Nut den sich bildenden Zwischenraum zwischen der Nut und der bzw. den Stromschiene(n) so mit flüssigen Gusseisen auszufüllen, dass das erstarrte Gusseisen in die wenigstens eine Vertiefung eingreift. Sofern die Nut eine, über die Länge des Kathodenblocks gesehen, variierende Tiefe aufweist, soll die wenigstens eine Vertiefung parallel zu dem Nutboden - also bezogen auf die horizontale Richtung schräg - verlaufen, also einen konstanten Abstand zu der Bodenwand der Nut aufweisen, um eine Verschiebbarkeit der Stromschiene(n) parallel zu dem Nutboden zu gewährleisten. Dies ist jedoch nachteilhaft, weil aufgrund der höheren Wärmeausdehnungskoeffizienten von Gusseisen und dem Material der Stromschiene(n) im Vergleich zu dem des Kathodenblocks während und nach dem Eingießen des flüssigen Gusseisens in den Zwischenraum zwischen der Nut und der bzw. den Stromschiene(n) des Kathodenblocks auftretenden Temperaturänderungen sowie den während der Inbetriebnahme und dem Ausschalten, und gegebenenfalls der Wiederinbetriebnahme, der den Kathodenblock umfassenden Elektrolysezelle auftretenden Temperaturänderungen zwischen dem Gusseisen und der bzw. den Stromschiene(n) einerseits und dem Kathodenblock andererseits Scherspannungen auftreten, welche zu einer die Funktion des Kathodenblocks beeinträchtigenden Beschädigung des Kathodenblocks in Form von beispielsweise Rissbildung in dem Kathodenblock oder gar einem Zerbrechen des Kathodenblocks führen kann. Eine solche Schädigung führt zu einer verringerten elektrischen Leitfähigkeit zwischen der Stromschiene bzw. dem Gusseisen und dem Kathodenblock und zu einer geringeren Stabilität der Anordnung oder führt sogar zum Versagen der gesamten Anordnung. Anstelle des Gusseisens kann hier auch Stampfmasse - wie oben beschrieben - verwendet werden.In order to prevent or at least make it more difficult for a busbar to move in the groove of a cathode block, it is in the WO 2012/107412 A2 It has been proposed to provide at least one recess in the wall delimiting the groove of a cathode block lined with graphite foil and, after inserting the busbar(s) into the groove, to fill the gap that forms between the groove and the busbar(s) with liquid Fill cast iron so that the solidified cast iron engages in at least one recess. If the groove has a varying depth as seen over the length of the cathode block, the at least one depression should run parallel to the bottom of the groove - i.e. obliquely in relation to the horizontal direction - i.e. have a constant distance from the bottom wall of the groove in order to allow for displaceability to ensure that the busbar(s) are parallel to the bottom of the groove. However, this is disadvantageous because due to the higher thermal expansion coefficients of cast iron and the material of the busbar(s) compared to that of the cathode block during and after pouring the liquid cast iron into the space between the groove and the busbar(s) of the The temperature changes occurring in the cathode block as well as the temperature changes that occur between the cast iron and the busbar(s) on the one hand and the cathode block on the other hand, which result in the function of the cathode block, occur during the commissioning and switching off, and if necessary the recommissioning, of the electrolytic cell comprising the cathode block Damage to the cathode block affecting the cathode block can result in, for example, cracks forming in the cathode block or even breaking the cathode block. Such damage leads to reduced electrical conductivity between the busbar or the cast iron and the cathode block and to less stability of the arrangement or even leads to failure of the entire arrangement. Instead of cast iron, ramming compound - as described above - can also be used here.

Wenn im Folgenden von Gusseisen gesprochen wird, ist zu verstehen, dass das Gusseisen durch Stampfmasse ersetzt werden kann, ohne dass es jedes Mal explizit beschrieben wird.When we talk about cast iron below, it should be understood that the cast iron can be replaced by ramming mass without it being explicitly described each time.

Aufgabe der vorliegenden Erfindung ist es daher, einen insbesondere zur Verwendung für eine Aluminium-Elektrolysezelle geeigneten Kathodenblock bereitzustellen, mit dem bei dem Betrieb der Elektrolysezelle über die Kathodenblocklänge eine im Wesentlichen homogene vertikale Stromverteilung erreicht wird, welcher zudem mit eingesetzter und mit Gusseisen ummantelter Stromschiene(n) auch bei großen Temperaturänderungen einen niedrigen und insbesondere auch über längere Betriebszeiten dauerhaft niedrigen spezifischen elektrischen Widerstand und niedrigen Übergangswiderstand zwischen der mit Gusseisen ummantelten Stromschiene und dem Kathodenblock aufweist, und, welcher bei großen Temperaturänderungen auch mit eingesetzter und mit Gusseisen ummantelter Stromschiene(n) gegenüber mechanischen Schädigungen, wie Rissbildung, stabil ist. Anstelle des Gusseisens kann auch Stampfmasse eingesetzt werden.The object of the present invention is therefore to provide a cathode block that is particularly suitable for use in an aluminum electrolytic cell, with which a substantially homogeneous vertical current distribution is achieved over the length of the cathode block when the electrolytic cell is operated, which also has an inserted busbar coated with cast iron ( n) low and especially over even with large temperature changes longer operating times, permanently low specific electrical resistance and low contact resistance between the cast iron-coated busbar and the cathode block, and which is stable against mechanical damage, such as cracking, even with large temperature changes even with the cast iron-coated busbar(s) inserted. Ramming compound can also be used instead of cast iron.

Erfindungsgemäß wird diese Aufgabe gelöst durch einen Kathodenblock für eine Aluminium-Elektrolysezelle auf Basis von Kohlenstoff und/oder Graphit, wobei der Kathodenblock wenigstens eine sich in der Längsrichtung des Kathodenblocks erstreckende Nut zur Aufnahme wenigstens einer Stromschiene aufweist, wobei wenigstens eine der wenigstens einen Nut eine, über die Länge des Kathodenblocks gesehen, variierende Tiefe aufweist, wobei in der die wenigstens eine Nut mit variierender Tiefe begrenzenden Wand des Kathodenblocks wenigstens eine Vertiefung aufweisend einen halbkreisförmigen, dreieckigen, rechteckigen oder trapezförmigen Querschnitt vorgesehen ist, welche sich in der Längsrichtung des Kathodenblocks zumindest annähernd über die gesamte Länge der wenigstens einen Nut horizontal erstreckt.According to the invention, this object is achieved by a cathode block for an aluminum electrolysis cell based on carbon and / or graphite, the cathode block having at least one groove extending in the longitudinal direction of the cathode block for receiving at least one busbar, at least one of the at least one groove having a , seen over the length of the cathode block, has varying depth, wherein in the wall of the cathode block delimiting at least one groove with varying depth, at least one recess having a semicircular, triangular, rectangular or trapezoidal cross-section is provided, which is at least in the longitudinal direction of the cathode block extends horizontally approximately over the entire length of the at least one groove.

Unter einer sich in der Längsrichtung des Kathodenblocks horizontal erstreckenden Vertiefung wird im Rahmen der vorliegenden Erfindung verstanden, dass sich die Vertiefung parallel zu der Längsebene des Kathodenblocks erstreckt. Unter einer parallelen Erstreckung wird dabei verstanden, dass die Vertiefung an jeder ihrer Stellen einen Winkel von weniger als 5°, besonders bevorzugt von weniger als 2°, ganz besonders bevorzugt von weniger als 1°, höchst bevorzugt von weniger als 0,5°, und am höchsten bevorzugt von weniger als 0,1° zu der Längsebene des Kathodenblocks aufweist. In diesem Zusammenhang wird unter Längsebene die Ebene verstanden, welche sich in der Richtung der Längsachse des Kathodenblocks erstreckt und parallel zu der Oberfläche der der Nut gegenüberliegenden Seite des Kathodenblocks verläuft.In the context of the present invention, a recess extending horizontally in the longitudinal direction of the cathode block is understood to mean that the recess extends parallel to the longitudinal plane of the cathode block. A parallel extension is understood to mean that the recess at each of its points has an angle of less than 5°, particularly preferably less than 2°, very particularly preferably less than 1°, most preferably less than 0.5°, and most preferably of less than 0.1° to the longitudinal plane of the cathode block. In this context, the term longitudinal plane is understood to mean the plane which extends in the direction of the longitudinal axis of the cathode block and runs parallel to the surface of the side of the cathode block opposite the groove.

Zudem wird im Rahmen der vorliegenden Erfindung unter einer Vertiefung in Abgrenzung zu einer bloßen Oberflächenrauigkeit eine Aussparung verstanden, welche bezogen auf die Oberfläche der die Nut begrenzenden Wand eine Tiefe von mindestens 0,5 mm und bevorzugt von mindestens 2 mm aufweist.In addition, in the context of the present invention, a recess, in contrast to mere surface roughness, is understood to mean a recess which, based on the surface of the wall delimiting the groove, has a depth of at least 0.5 mm and preferably at least 2 mm.

Erfindungsgemäß wurde erkannt, dass durch das Vorsehen wenigstens einer sich in der Längsrichtung des Kathodenblocks horizontal erstreckenden Vertiefung in der die Nut des Kathodenblocks begrenzenden Wand, und zwar bevorzugt in beiden der Seitenwände, insbesondere auch bei Ausgestalten der Nut mit variierender Tiefe in dem Kathodenblock ein Kathodenblock geschaffen wird, welcher auch mit in die Nut eingesetzter und mit Gusseisen ummantelter Stromschiene einen niedrigen elektrischen Widerstand und niedrigen Übergangswiderstand aufweist. Abgesehen davon wird aufgrund des Vorsehens der sich in der Längsrichtung des Kathodenblocks horizontal erstreckenden Vertiefung in der die Nut des Kathodenblocks begrenzenden Wand auch bei großen Temperaturänderungen eine mechanische Schädigung des Kathodenblocks mit in die Nut eingesetzter und mit Gusseisen ummantelter Stromschiene, wie beispielsweise eine Rissbildung des Kathodenblocks, zuverlässig vermieden. Zum einen wird durch die Verwendung einer Nut mit variabler Tiefe in der Längsrichtung des Kathodenblocks eine derart gleichmäßige Stromdichteverteilung an der Kathodenblockoberfläche erreicht, dass bei dem Betrieb der den Kathodenblock umfassenden Elektrolysezelle ein übermäßiger Abtrag von Kathodenblockmaterial in denjenigen Bereichen wirksam vermieden wird, wo bei Verwendung eines Kathodenblocks mit in der Längsrichtung des Kathodenblocks gleicher Nuttiefe eine hohe lokale Stromdichte vorliegen würde. Durch entsprechende Anpassung der Nuttiefe kann die Stromdichteverteilung in breiten Grenzen modifiziert und vergleichmäßigt werden. Indem der Kathodenblock in seiner Nut eine sich in der Längsrichtung des Kathodenblocks horizontal erstreckende Vertiefung aufweist, wird eine vertikale Fixierung der mit Gusseisen ummantelten Stromschiene in der Nut des Kathodenblocks erreicht, welche aber eine gewisse Bewegung in horizontaler Richtung des Kathodenblocks zulässt. Aufgrund dieser horizontalen Beweglichkeit der mit Gusseisen ummantelten Stromschiene wird insbesondere auch bei den während und nach der Inbetriebnahme bzw. während dem Abschalten einer den Kathodenblock umfassenden Elektrolysezelle auftretenden raschen Temperaturänderungen das Auftreten von Scherspannungen zwischen der mit Gusseisen ummantelten Stromschiene und dem Kathodenblock zuverlässig vermieden, wie diese bei einer schräg angeordneten Vertiefung infolge der - aufgrund der höheren Wärmeausdehnungskoeffizienten von Gusseisen und dem Material der Stromschienen im Vergleich zu dem Wärmeausdehnungskoeffizienten des Materials des Kathodenblocks auftretenden - höheren Ausdehnung bzw. Schrumpfung des Gusseisens und der Stromschiene relativ zu dem Kathodenblock auftreten würden. Dadurch wird eine Schädigung des Kathodenblocks beispielsweise in Form von Rissbildung oder gar ein Zerbrechen des Kathodenblocks auch während langer Betriebsdauer der Elektrolysezelle zuverlässig verhindert, bei gleichzeitiger Gewährleistung einer hervorragenden elektrischen Leitfähigkeit zwischen der Stromschiene bzw. dem Gusseisen und dem Kathodenblock. Aufgrund der vertikalen Fixierung der mit Gusseisen ummantelten Stromschiene in der Nut der Kathodenblockes kommt es zu einer vorteilhaften Anpressung der Kathodenbarren / Gusseisenanordnung gegen den Nutboden durch die thermische Ausdehnung der Barren/Gusseisenanordnung relativ zum Kathodenblock während der Inbetriebnahme. Damit wird ein verbesserter elektrischer Kontakt erreicht, der zu einem geringeren elektrischen Widerstand und damit zu einer höheren Energieeffizienz führt. Im weiteren Vorteil zu dem aus der WO 2012/107412 A2 bekannten Kathodenblock werden diese hervorragenden Eigenschaften insbesondere auch dann erreicht, wenn die Nut des Kathodenblocks nicht mit einer teuren und aufwendig einzubringenden Graphitfolie ausgekleidet ist. Insgesamt wird somit auch bei großen Temperaturänderungen eine Kontrolle von - infolge der unterschiedlichen Wärmeausdehnungskoeffizienten von Gusseisen, Stromschiene und Kathodenblock auftretenden - Zugspannungen, Scherspannungen und Druckspannungen erreicht, welche eine hervorragende elektrische Leitfähigkeit und eine exzellente mechanische Stabilität des Kathodenblocks auch mit in die Nut eingesetzter und mit Gusseisen ummantelter Stromschiene gewährleistet.According to the invention, it was recognized that by providing at least one recess extending horizontally in the longitudinal direction of the cathode block in the wall delimiting the groove of the cathode block, preferably in both of the side walls, in particular also when the groove is designed with varying depth in the cathode block, a cathode block is created, which has a low electrical resistance and low contact resistance even with the busbar inserted into the groove and coated with cast iron. Apart from this, due to the provision of the recess extending horizontally in the longitudinal direction of the cathode block in the wall delimiting the groove of the cathode block, even with large temperature changes, mechanical damage to the cathode block with the busbar inserted into the groove and coated with cast iron, such as cracking of the cathode block , reliably avoided. On the one hand, the use of a groove with a variable depth in the longitudinal direction of the cathode block achieves such a uniform current density distribution on the cathode block surface that, during the operation of the electrolytic cell comprising the cathode block, excessive removal of cathode block material is effectively avoided in those areas where, when using a Cathode block with the same groove depth in the longitudinal direction of the cathode block would have a high local current density. By appropriately adjusting the groove depth, the current density distribution can be modified and evened out within broad limits. Because the cathode block has a recess in its groove that extends horizontally in the longitudinal direction of the cathode block, a vertical fixation of the cast iron-coated busbar in the groove of the cathode block is achieved, which, however, allows a certain movement in the horizontal direction of the cathode block Cathode blocks allow. Due to this horizontal mobility of the cast iron-coated busbar, the occurrence of shear stresses between the cast iron-coated busbar and the cathode block is reliably avoided, especially during the rapid temperature changes that occur during and after commissioning or during switching off of an electrolytic cell comprising the cathode block, such as this in the case of an obliquely arranged depression as a result of the higher expansion or shrinkage of the cast iron and the busbar relative to the cathode block - which occurs due to the higher coefficient of thermal expansion of cast iron and the material of the busbars compared to the coefficient of thermal expansion of the material of the cathode block. This reliably prevents damage to the cathode block, for example in the form of cracks or even breakage of the cathode block, even during a long period of operation of the electrolytic cell, while at the same time ensuring excellent electrical conductivity between the busbar or the cast iron and the cathode block. Due to the vertical fixation of the cast iron-coated busbar in the groove of the cathode block, there is an advantageous pressure of the cathode bar/cast iron arrangement against the bottom of the groove due to the thermal expansion of the bar/cast iron arrangement relative to the cathode block during commissioning. This achieves improved electrical contact, which leads to lower electrical resistance and thus higher energy efficiency. In further advantage to that from the WO 2012/107412 A2 Known cathode block, these excellent properties are achieved in particular even if the groove of the cathode block is not lined with an expensive graphite foil that is difficult to install. Overall, even with large temperature changes, control of tensile stresses, shear stresses and compressive stresses - which occur as a result of the different thermal expansion coefficients of cast iron, busbar and cathode block - is achieved, which ensures excellent electrical conductivity and excellent mechanical properties Stability of the cathode block is guaranteed even with the busbar inserted into the groove and covered with cast iron.

Um bei dem Elektrolysebetrieb eine besonders gleichmäßige vertikale Stromdichteverteilung an der Kathodenblockoberfläche zu erreichen, wird in Weiterbildung des Erfindungsgedankens vorgeschlagen, dass wenigstens eine der wenigstens einen Nut und bevorzugt alle der Nuten mit variierender Tiefe an ihren längsseitigen Enden eine geringere Tiefe aufweist bzw. aufweisen als in ihrer bzw. ihren Mitte(n). Auf diese Weise wird eine gleichmäßige Verteilung des bei dem Elektrolysebetrieb zugeführten elektrischen Stroms über die gesamte Länge des Kathodenblocks erreicht, wodurch eine übermäßige elektrische Stromdichte an den längsseitigen Enden des Kathodenblocks und so ein vorzeitiger Verschleiß an den Enden des Kathodenblocks vermieden wird. Durch eine solche gleichmäßige Stromdichteverteilung über die Länge des Kathodenblocks werden zudem bei der Elektrolyse durch Wechselwirkung elektromagnetischer Felder hervorgerufene Bewegungen in der Aluminiumschmelze vermieden, wodurch es möglich wird, die Anode in einer geringeren Höhe über der Oberfläche der Aluminiumschmelze anzuordnen. Dadurch wird der elektrische Widerstand zwischen der Anode und der Aluminiumschmelze verringert und die Energieeffizienz der durchgeführten Schmelzflusselektrolyse erhöht. Ein weiterer besonderer Vorteil dieser Ausführungsform ist es, dass sich bei dieser Ausgestaltung der Nut die in der Vertiefung der Nut vorgesehene ggf. mit Gusseisen umhüllte Stromschiene(n) während und nach der bei der Inbetriebnahme der Elektrolysezelle auftretenden Erhöhung der Temperatur in der horizontalen Richtung ausdehnt bzw. ausdehnen, infolge dessen die Stromschiene(n) jeweils an die die Nut an dieser Stelle begrenzende Bodenwand des Kathodenblocks angepresst werden, wodurch der Übergangswiderstand zwischen der mit Gusseisen ummantelten Stromschiene und dem Kathodenblock verringert wird.In order to achieve a particularly uniform vertical current density distribution on the cathode block surface during electrolysis operation, it is proposed in a further development of the inventive concept that at least one of the at least one groove and preferably all of the grooves with varying depth has or have a smaller depth at their longitudinal ends than in their center(s). In this way, an even distribution of the electrical current supplied during electrolysis operation is achieved over the entire length of the cathode block, thereby avoiding excessive electrical current density at the longitudinal ends of the cathode block and thus premature wear at the ends of the cathode block. Such a uniform current density distribution over the length of the cathode block also avoids movements in the aluminum melt caused by interaction of electromagnetic fields during electrolysis, which makes it possible to arrange the anode at a lower height above the surface of the aluminum melt. This reduces the electrical resistance between the anode and the aluminum melt and increases the energy efficiency of the fusion electrolysis carried out. Another particular advantage of this embodiment is that with this configuration of the groove, the busbar(s) provided in the recess of the groove, possibly covered with cast iron, expands in the horizontal direction during and after the increase in temperature that occurs when the electrolytic cell is put into operation or expand, as a result of which the busbar(s) are pressed against the bottom wall of the cathode block delimiting the groove at this point, whereby the contact resistance between the cast iron-coated busbar and the cathode block is reduced.

Bei der vorstehenden Ausführungsform nimmt die Tiefe wenigstens einer der wenigstens einen Nut mit variierender Tiefe, in der Längsrichtung des Kathodenblocks gesehen, vorzugsweise von einem längsseiteigen Ende bis zu der Mitte des Kathodenblocks zumindest im Wesentlichen monoton zu und nimmt diese von der Mitte zu dem anderen längsseitigen Ende des Kathodenblocks zumindest im Wesentlichen monoton ab, so dass sich, im Längsschnitt des Kathodenblocks gesehen, eine zumindest im Wesentlichen dreiecksförmige Nut ergibt. Dadurch werden die vorstehend genannten Vorteile in verstärktem Ausmaß erreicht.In the above embodiment, the depth of at least one of the at least one groove with varying depth, viewed in the longitudinal direction of the cathode block, preferably increases at least substantially monotonically from one longitudinal end to the center of the cathode block and increases from the center to the other longitudinal end End of the cathode block at least substantially monotonously, so that, seen in the longitudinal section of the cathode block, an at least substantially triangular groove results. As a result, the advantages mentioned above are achieved to an increased extent.

Gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung umfasst die die wenigstens eine Nut mit variierender Tiefe begrenzende Wand eine Bodenwand und zwei Seitenwände, wobei jede der beiden Seitenwände jeweils wenigstens eine Vertiefung aufweist, welche sich in der Längsrichtung des Kathodenblocks horizontal erstreckt. Auf diese Weise wird eine besonders gute vertikale Fixierung der Stromschiene in der Nut erreicht, bei gleichzeitig ausreichend hoher Beweglichkeit der Stromschiene in horizontaler Richtung, um auch bei großen Temperaturänderungen das Auftreten von Scherspannungen infolge der unterschiedlichen Wärmeausdehnungskoeffizienten von Gusseisen, Stromschiene und Kathodenblock zuverlässig zu vermeiden.According to a further preferred embodiment of the present invention, the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each of the two side walls having at least one depression which extends horizontally in the longitudinal direction of the cathode block. In this way, a particularly good vertical fixation of the busbar in the groove is achieved, while at the same time the busbar has sufficient mobility in the horizontal direction in order to reliably avoid the occurrence of shear stresses due to the different thermal expansion coefficients of cast iron, busbar and cathode block, even with large temperature changes.

Vorzugsweise umfasst die die wenigstens eine Nut mit variierender Tiefe begrenzende Wand eine Bodenwand und zwei Seitenwände, wobei jede Seitenwand jeweils genau eine Vertiefung aufweist, welche sich in der Längsrichtung des Kathodenblocks horizontal erstreckt. Auf diese Weise wird bei vergleichsweise geringem Herstellungsaufwand eine besonders gute vertikale Fixierung der Stromschiene in der Nut erreicht, bei gleichzeitig ausreichend hoher Beweglichkeit in horizontaler Richtung, um bei großen Temperaturänderungen das Auftreten von Scherspannungen infolge der unterschiedlichen Wärmeausdehnungskoeffizienten von Gusseisen, Stromschiene und Kathodenblock zuverlässig zu vermeiden.Preferably, the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each side wall having exactly one recess which extends horizontally in the longitudinal direction of the cathode block. In this way, a particularly good vertical fixation of the busbar in the groove is achieved with comparatively little manufacturing effort, while at the same time sufficiently high mobility in the horizontal direction in order to reliably avoid the occurrence of shear stresses due to the different thermal expansion coefficients of cast iron, busbar and cathode block in the event of large temperature changes .

Gleichermaßen ist es bevorzugt, dass die die wenigstens eine Nut mit variierender Tiefe begrenzende Wand eine Bodenwand und zwei Seitenwände umfasst, wobei jede Seitenwand jeweils zwei Vertiefungen aufweist, welche sich in der Längsrichtung des Kathodenblocks jeweils horizontal erstrecken. Auf diese Weise wird eine besonders gute vertikale Fixierung der Stromschiene in der Nut bei gleichzeitig ausreichend hoher Beweglichkeit in horizontaler Richtung auch erreicht, wenn die Tiefe der einzelnen Vertiefungen vergleichsweise gering ist.Equally, it is preferred that the wall delimiting the at least one groove with varying depth comprises a bottom wall and two side walls, each side wall having two depressions, each of which extends horizontally in the longitudinal direction of the cathode block. In this way, a particularly good vertical fixation of the busbar in the groove is achieved while at the same time sufficiently high mobility in the horizontal direction, even if the depth of the individual recesses is comparatively small.

Dabei kann der Kathodenblock zwei auf derselben Seite des Kathodenblocks angeordnete Nuten aufweisen, wobei beide Nuten dieselben Ausmaße aufweisen und deren begrenzende Wände jeweils eine Bodenwand und zwei Seitenwände umfassen, wobei jede Seitenwand jeweils eine Vertiefung aufweist, welche sich in der Längsrichtung des Kathodenblocks horizontal erstreckt, oder wobei jede Seitenwand jeweils zwei Vertiefungen aufweist, welche sich in der Längsrichtung des Kathodenblocks horizontal erstrecken. So wird für einen zwei Nuten aufweisenden Kathodenblock bei vergleichsweise geringem Herstellungsaufwand eine besonders gute vertikale Fixierung beider Stromschienen in den Nuten erreicht, bei gleichzeitig ausreichend hoher Beweglichkeit in horizontaler Richtung, um bei großen Temperaturänderungen das Auftreten von Scherspannungen infolge der unterschiedlichen Wärmeausdehnungskoeffizienten von Gusseisen, Stromschiene und Kathodenblock zuverlässig zu vermeiden.The cathode block can have two grooves arranged on the same side of the cathode block, both grooves having the same dimensions and the delimiting walls of which each comprise a bottom wall and two side walls, each side wall having a depression which extends horizontally in the longitudinal direction of the cathode block, or wherein each side wall has two depressions which extend horizontally in the longitudinal direction of the cathode block. For a cathode block with two grooves, a particularly good vertical fixation of both busbars in the grooves is achieved with comparatively little manufacturing effort, while at the same time sufficiently high mobility in the horizontal direction to prevent shear stresses from occurring in the event of large temperature changes as a result of the different thermal expansion coefficients of cast iron, busbar and Cathode block can be reliably avoided.

Alternativ zu der vorstehenden Ausführungsform kann der Kathodenblock auch nur eine Nut umfassen.As an alternative to the above embodiment, the cathode block can also only comprise one groove.

Um eine besonders gute Fixierung der ggf. mit Gusseisen ummantelten Stromschiene in der Nut in vertikaler Richtung bei gleichzeitig ausreichender Beweglichkeit in horizontaler Richtung zu gewährleisten, kann es sein, dass sich wenigstens eine der wenigstens einen Vertiefung und besonders bevorzugt jede der wenigstens einen Vertiefung durchgehend über wenigstens 60 %, bevorzugt über wenigstens 80 %, besonders bevorzugt über wenigstens 90 %, ganz besonders bevorzugt über wenigstens 95 % der Länge der wenigstens einen Nut erstreckt, was nicht Teil der Erfindung ist. Erfindungsgemäß erstreckt sich die wenigstens eine Vertiefung zumindest annähernd über die gesamte Länge der wenigstens einen Nut.In order to ensure a particularly good fixation of the busbar, which may be coated with cast iron, in the groove in the vertical direction while at the same time ensuring sufficient mobility in the horizontal direction, it may be that at least one of the at least one recess and particularly preferably each of the at least one recess extends continuously at least 60%, preferably over at least 80%, particularly preferably over at least 90%, very particularly preferably over at least 95% of the length of the at least one groove, which is not part of the invention. According to the invention, the at least one depression extends at least approximately over the entire length of the at least one groove.

Aus dem gleichen Grund ist es bevorzugt, dass wenigstens eine der wenigstens einen Vertiefung und besonders bevorzugt jede der wenigstens einen Vertiefung eine Tiefe von 0,5 mm bis 40 mm, bevorzugt von 2 mm bis 30 mm und besonders bevorzugt von 5 mm bis 20 mm aufweist.For the same reason, it is preferred that at least one of the at least one depression and particularly preferably each of the at least one depression has a depth of 0.5 mm to 40 mm, preferably of 2 mm to 30 mm and particularly preferably of 5 mm to 20 mm having.

Aus dem gleichen Grund ist es zudem bevorzugt, dass wenigstens eine der wenigstens einen Vertiefung und besonders bevorzugt jede der wenigstens einen Vertiefung eine auf die Höhe des Kathodenblocks bezogene Öffnungsbreite von 2 mm bis 40 mm, bevorzugt von 5 mm bis 30 mm und besonders bevorzugt von 10 mm bis 20 mm aufweist.For the same reason, it is also preferred that at least one of the at least one recess and particularly preferably each of the at least one recess has an opening width, based on the height of the cathode block, of 2 mm to 40 mm, preferably of 5 mm to 30 mm and particularly preferably of 10 mm to 20 mm.

Grundsätzlich kann die wenigstens eine Vertiefung jeden polygonalen oder gebogenen Querschnitt aufweisen. Gute Ergebnisse im Hinblick auf einen guten Eingriff der Gusseisenumhüllung in die wenigstens eine Vertiefung und gleichzeitig im Hinblick auf eine zuverlässige und unproblematische Füllbarkeit der Vertiefung mit Gusseisen beim Vergießen werden insbesondere erreicht, wenn wenigstens eine der wenigstens einen Vertiefung und besonders bevorzugt jede der wenigstens einen Vertiefung einen zumindest im Wesentlichen halbkreisförmigen, dreieckigen, rechteckigen oder trapezförmigen, bevorzugt halbkreisförmigen, dreieckigen, rechteckigen oder trapezförmigen, Querschnitt aufweist.In principle, the at least one depression can have any polygonal or curved cross section. Good results with regard to good engagement of the cast iron casing in the at least one recess and at the same time with regard to reliable and unproblematic filling of the recess with cast iron during casting are achieved in particular if at least one of the at least one recess and particularly preferably each of the at least one recess an at least essentially semicircular, triangular, rectangular or trapezoidal, preferably semicircular, triangular, rectangular or trapezoidal, cross-section.

Gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung erstreckt sich die wenigstens eine Vertiefung zumindest im Wesentlichen senkrecht, bevorzugt senkrecht, in die die wenigstens eine Nut begrenzende Wand des Kathodenblocks hinein.According to a further preferred embodiment of the present invention, the at least one recess extends at least substantially vertically, preferably vertically, into the wall of the cathode block delimiting the at least one groove.

Gemäß der vorliegenden Erfindung wird die wenigstens eine Vertiefung - in der Tiefenrichtung der Nut betrachtet - an jedem ihrer Enden durch einen Übergangsbereich zwischen der Vertiefung und einem daran angrenzenden Abschnitt der Nutwand begrenzt. Wenn dieser Übergangsbereich winklig ausgestaltet ist, beträgt der Winkel zwischen dem angrenzenden Abschnitt der Nutwand und der Wand der Vertiefung, von der Kathodenblockinnenseite aus gesehen, vorzugsweise 90 Grad bis 160 Grad, besonders bevorzugt 90 Grad bis 135 Grad und ganz besonders bevorzugt 100 Grad bis 120 Grad.According to the present invention, the at least one depression - viewed in the depth direction of the groove - is delimited at each of its ends by a transition region between the depression and a section of the groove wall adjacent thereto. If this transition region is designed at an angle, the angle between the adjacent section of the groove wall and the wall of the recess, viewed from the inside of the cathode block, is preferably 90 degrees to 160 degrees, particularly preferably 90 degrees to 135 degrees and most preferably 100 degrees to 120 Degree.

In dem Fall, dass dieser Übergangsbereich gekrümmt, möglicherweise, aber nicht notwendigerweise ideal kreisförmig gekrümmt, ausgestaltet ist, beträgt der Krümmungsradius des Übergangsbereichs bevorzugt maximal 50 mm, besonders bevorzugt maximal 20 mm und höchst bevorzugt maximal 5 mm.In the event that this transition region is curved, possibly but not necessarily ideally circularly curved, the radius of curvature of the transition region is preferably a maximum of 50 mm, particularly preferably a maximum of 20 mm and most preferably a maximum of 5 mm.

Zudem betrifft die vorliegende Erfindung eine Kathodenanordnung, welche wenigstens einen zuvor beschriebenen Kathodenblock enthält, wobei in wenigstens einer der wenigstens einen Nut mit variierender Tiefe des wenigstens einen Kathodenblocks wenigstens eine Stromschiene vorgesehen ist, welche zumindest bereichsweise eine Umhüllung aus Gusseisen aufweist, welche zumindest abschnittsweise in die wenigstens eine Vertiefung eingreift.In addition, the present invention relates to a cathode arrangement which contains at least one previously described cathode block, wherein at least one busbar is provided in at least one of the at least one groove with varying depth of the at least one cathode block, which has at least partially a casing made of cast iron, which at least partially in which engages at least one depression.

Gemäß einer bevorzugten Ausführungsform der vorliegenden Erfindung ist der in die wenigstens eine Vertiefung eingreifenden Abschnitt der Umhüllung aus Gusseisen komplementär zu der Vertiefung ausgestaltet. Auf diese Weise kann ein besonders guter formschlüssiger Eingriff der Umhüllung aus Gusseisen in die Vertiefung und somit eine besonders wirksame mechanische Befestigung der Gusseisenumhüllung und der damit verbundenen Stromschiene an dem Kathodenblock erreicht werden, welche dennoch eine zur Vermeidung von Scherspannungen zwischen Gusseisen, Stromschiene und Kathodenblock infolge von großen Temperaturänderungen hinreichende Beweglichkeit der Stromschiene in horizontaler Richtung zulässt.According to a preferred embodiment of the present invention, the section of the cast iron casing which engages in the at least one recess is designed to be complementary to the recess. In this way, a particularly good positive engagement of the cast iron casing in the recess and thus a particularly effective mechanical fastening of the cast iron casing and the busbar connected to it to the cathode block can be achieved, which nevertheless results in the avoidance of shear stresses between the cast iron, busbar and cathode block allows sufficient mobility of the busbar in the horizontal direction due to large temperature changes.

Vorzugsweise greift die Umhüllung aus Gusseisen über wenigstens 50 %, weiter bevorzugt über wenigstens 80 %, besonders bevorzugt über wenigstens 90%, ganz besonders bevorzugt über wenigstens 95 % und höchst bevorzugt über zumindest im Wesentlichen deren gesamte Länge in die wenigstens eine Vertiefung ein. Dadurch werden die vorstehend beschriebenen Vorteile in besonders hohem Ausmaß erreicht.Preferably, the cast iron casing engages into the at least one recess over at least 50%, more preferably over at least 80%, particularly preferably over at least 90%, very particularly preferably over at least 95% and most preferably over at least substantially its entire length. As a result, the advantages described above are achieved to a particularly high extent.

Aus dem gleichen Grund ist es gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung vorgesehen, dass der in die wenigstens eine Vertiefung eingreifende Abschnitt der Umhüllung und ggf. die davon umhüllte Stromschiene wenigstens 70 %, bevorzugt wenigstens 80 %, besonders bevorzugt wenigstens 90 %, ganz besonders bevorzugt wenigstens 95 % und höchst bevorzugt 100 % der Vertiefung ausfüllt. Dadurch kann eine ungewollte Verschiebung der Stromschiene in der vertikalen Richtung des Kathodenblocks und insbesondere ein Herausfallen der Stromschiene aus der Nut besonders zuverlässig vermieden werden.For the same reason, according to a further preferred embodiment of the present invention, it is provided that the section of the casing which engages in the at least one recess and possibly the busbar covered by it is at least 70%, preferably at least 80%, particularly preferably at least 90%, completely particularly preferably fills at least 95% and most preferably 100% of the depression. As a result, an unwanted displacement of the busbar in the vertical direction of the cathode block and in particular the busbar falling out of the groove can be avoided particularly reliably.

In Weiterbildung des Erfindungsgedankens wird vorgeschlagen, dass der Kathodenblock der Kathodenanordnung eine Nut mit einem zumindest im Wesentlichen rechteckigen, bevorzugt einem rechteckigen, Querschnitt aufweist und in die Nut eine oder zwei aneinander angrenzende Stromschiene(n) eingesetzt sind, wobei der Zwischenraum zwischen der Nut und der Stromschiene(n) so mit Gusseisen ausgefüllt ist, dass das Gusseisen über zumindest im Wesentlichen dessen gesamte Länge in die wenigstens eine Vertiefung eingreift.In a further development of the inventive concept, it is proposed that the cathode block of the cathode arrangement has a groove with at least essentially rectangular, preferably a rectangular, cross-section and one or two adjacent busbar(s) are inserted into the groove, the space between the groove and the busbar(s) being filled with cast iron in such a way that the cast iron is at least substantially above it entire length engages in at least one recess.

Ein weiterer Gegenstand der vorliegenden Erfindung ist eine Kathode, welche wenigstens einen zuvor beschriebenen Kathodenblock oder zumindest eine zuvor beschriebene Kathodenanordnung umfasst.A further subject of the present invention is a cathode which comprises at least one previously described cathode block or at least one previously described cathode arrangement.

Ferner betrifft die vorliegende Erfindung die Verwendung eines zuvor beschriebenen Kathodenblocks, einer zuvor beschriebenen Kathodenanordnung oder einer zuvor beschriebenen Kathode zur Durchführung einer Schmelzflusselektrolyse zur Herstellung von Metall, und zwar bevorzugt zur Herstellung von Aluminium.The present invention further relates to the use of a previously described cathode block, a previously described cathode arrangement or a previously described cathode for carrying out fusion electrolysis for the production of metal, preferably for the production of aluminum.

Ein weiterer Gegenstand der vorliegenden Erfindung ist eine Kathodenanordnung, welche wenigstens einen zuvor beschriebenen Kathodenblock umfasst.A further subject of the present invention is a cathode arrangement which comprises at least one cathode block described above.

Ferner betrifft die vorliegende Erfindung die Verwendung eines zuvor beschriebenen Kathodenblocks, einer zuvor beschriebenen Kathodenanordnung zur Durchführung einer Schmelzflusselektrolyse zur Herstellung von Metall, und zwar bevorzugt zur Herstellung von Aluminium.The present invention further relates to the use of a previously described cathode block, a previously described cathode arrangement for carrying out fusion electrolysis for the production of metal, preferably for the production of aluminum.

Nachfolgend wird die vorliegende Erfindung rein beispielhaft anhand vorteilhafter Ausführungsformen und unter Bezugnahme auf die beigefügten Zeichnungen beschrieben.The present invention is described below purely by way of example using advantageous embodiments and with reference to the accompanying drawings.

Dabei zeigen:

Fig. 1
einen Querschnitt eines Ausschnitts einer Aluminium-Elektrolysezelle mit einer Kathodenanordnung gemäß eines ersten Ausführungsbeispiels der vorliegenden Erfindung,
Fig. 2
einen Längsschnitt der Kathodenanordnung der in der Fig. 1 gezeigten Aluminium-Elektrolysezelle,
Fig. 3
einen Längsschnitt eines Ausschnitts einer Aluminium-Elektrolysezelle mit einer Kathodenanordnung gemäß eines zweiten Ausführungsbeispiels der vorliegenden Erfindung,
Fig. 4
einen Querschnitt der Kathodenanordnung der in der Fig. 3 gezeigten Aluminium-Elektrolysezelle,
Fig. 5a-d
beispielhafte Querschnitte von Vertiefungen, die in einer Nut eines erfindungsgemäßen Kathodenblocks vorgesehen sind,
Show:
Fig. 1
a cross section of a section of an aluminum electrolytic cell with a cathode arrangement according to a first exemplary embodiment of the present invention,
Fig. 2
a longitudinal section of the cathode arrangement in the Fig. 1 aluminum electrolysis cell shown,
Fig. 3
a longitudinal section of a section of an aluminum electrolytic cell with a cathode arrangement according to a second exemplary embodiment of the present invention,
Fig. 4
a cross section of the cathode arrangement in the Fig. 3 aluminum electrolysis cell shown,
Fig. 5a-d
exemplary cross sections of depressions which are provided in a groove of a cathode block according to the invention,

In der Fig. 1 ist im Querschnitt ein Ausschnitt einer Aluminium-Elektrolysezelle 10 mit einer Kathodenanordnung 12 gezeigt, die gleichzeitig den Boden einer Wanne für eine während des Betriebs der Elektrolysezelle 10 erzeugte Aluminiumschmelze 14 und für eine oberhalb der Aluminiumschmelze 14 befindliche Kryolith-Aluminiumoxid-Schmelze 16 bildet. Mit der Kryolith-Aluminiumoxid-Schmelze 16 steht eine Anode 18 in Kontakt. Seitlich wird die durch den unteren Teil der Aluminium-Elektrolysezelle 10 gebildete Wanne durch eine in der Fig. 1 nicht dargestellte Auskleidung aus Kohlenstoff und/oder Graphit begrenzt.In the Fig. 1 a section of an aluminum electrolysis cell 10 is shown in cross section with a cathode arrangement 12, which simultaneously forms the bottom of a trough for an aluminum melt 14 generated during operation of the electrolysis cell 10 and for a cryolite-aluminum oxide melt 16 located above the aluminum melt 14. An anode 18 is in contact with the cryolite-alumina melt 16. On the side, the trough formed by the lower part of the aluminum electrolysis cell 10 is formed by an in the Fig. 1 lining made of carbon and/or graphite, not shown.

Die Kathodenanordnung 12 umfasst mehrere Kathodenblöcke 20, die jeweils über eine in eine zwischen den Kathodenblöcken 20 angeordnete Stampfmassenfuge 22 eingefügte Stampfmasse 24 miteinander verbunden sind. Ein Kathodenblock 20 umfasst dabei zwei an seiner Unterseite angeordnete Nuten 26 mit einem rechtwinkligen, nämlich im Wesentlichen rechteckigen Querschnitt, wobei in jeder Nut 26 jeweils eine Stromschiene 28 aus Stahl mit ebenfalls rechtwinkligem Querschnitt aufgenommen ist.The cathode arrangement 12 comprises a plurality of cathode blocks 20, each of which is connected to one another via a ramming mass 24 inserted into a ramming mass joint 22 arranged between the cathode blocks 20. A cathode block 20 comprises two grooves 26 arranged on its underside with a rectangular, namely essentially rectangular cross section, in each Groove 26 each accommodates a busbar 28 made of steel with a rectangular cross section.

Die Nuten 26 werden jeweils durch zwei Seitenwände 32 und eine Bodenwand 34 des Kathodenblocks 20 begrenzt, wobei in jeder der Seitenwände 32 eine sich im Wesentlichen senkrecht in die Seitenwand 32 hinein erstreckende Vertiefung 36 mit annähernd halbkreisförmigem Querschnitt vorgesehen ist. Jede Vertiefung 36 wird jeweils durch einen oberen und einen unteren Übergangsbereich 37 des Kathodenblocks 20 begrenzt. Die Übergangsbereiche 37 sind in dem vorliegenden Ausführungsbeispiel winklig mit einem Winkel α zwischen dem angrenzenden Abschnitt der Nutwand und der Wand der Vertiefung von 90 Grad ausgebildet. Der Zwischenraum zwischen der Stromschiene 28 und der Nut 26 ist dabei jeweils mit Gusseisen 38 ausgegossen. Dabei bildet das Gusseisen 38 eine Umhüllung 39 für die Stromschiene 28 und steht mit der Stromschiene 28 in stoffschlüssiger Verbindung.The grooves 26 are each delimited by two side walls 32 and a bottom wall 34 of the cathode block 20, with a depression 36 with an approximately semicircular cross section extending essentially vertically into the side wall 32 being provided in each of the side walls 32. Each depression 36 is delimited by an upper and a lower transition region 37 of the cathode block 20. In the present exemplary embodiment, the transition regions 37 are formed at an angle with an angle α between the adjacent section of the groove wall and the wall of the recess of 90 degrees. The space between the busbar 28 and the groove 26 is filled with cast iron 38. The cast iron 38 forms a casing 39 for the busbar 28 and is in a material connection with the busbar 28.

Darüber hinaus bildet das in den Vertiefungen 36 aufgenommene Gusseisen 38 mit dem die Vertiefung 36 begrenzenden Material des Kathodenblocks 20 jeweils eine formschlüssige Verbindung, die eine Bewegung der mit dem Gusseisen 38 verbundenen Stromschiene 28 in Richtung des Pfeils 40 verhindert.In addition, the cast iron 38 accommodated in the recesses 36 forms a positive connection with the material of the cathode block 20 delimiting the recess 36, which prevents the busbar 28 connected to the cast iron 38 from moving in the direction of the arrow 40.

In der Fig. 1 ist konkret der Querschnitt der Kathodenanordnung 12 an einem längsseitigen Ende des Kathodenblocks 20 gezeigt. Die Tiefe der Nut 26 des Kathodenblocks 20 variiert dabei über die Länge der Nut 26. Der Nutquerschnitt im Bereich der - bezogen auf die Längsrichtung des Kathodenblocks - Mitte der Nut 26 ist in der Fig. 1 durch eine gestrichelte Linie 42 angedeutet. Der Unterschied zwischen der Nuttiefe an den längsseitigen Enden der Nut 26 und in der - bezogen auf die Längsrichtung des Kathodenblocks - Mitte der Nut 26 beträgt im vorliegenden Ausführungsbeispiel etwa 5 cm. Dabei beträgt die Tiefe der Nut 26 an den beiden längsseitigen Enden der Nut 26 etwa 16 cm, wohingegen die Tiefe der Nut 26 in der - bezogen auf die Längsrichtung des Kathodenblocks - Mitte der Nut 26 etwa 21 cm beträgt. Die Breite 44 jeder Nut 26 ist über die gesamte Nutlänge im Wesentlichen konstant und beträgt etwa 15 cm, wohingegen die Breite 46 der Kathodenblöcke 20 jeweils etwa 42 cm beträgt.In the Fig. 1 Specifically, the cross section of the cathode arrangement 12 is shown at a longitudinal end of the cathode block 20. The depth of the groove 26 of the cathode block 20 varies over the length of the groove 26. The groove cross section in the area of the center of the groove 26 - based on the longitudinal direction of the cathode block - is in the Fig. 1 indicated by a dashed line 42. The difference between the groove depth at the longitudinal ends of the groove 26 and in the center of the groove 26 - based on the longitudinal direction of the cathode block - is approximately 5 cm in the present exemplary embodiment. The depth of the groove 26 at the two longitudinal ends of the groove 26 is approximately 16 cm, whereas the depth the groove 26 in which - based on the longitudinal direction of the cathode block - the center of the groove 26 is approximately 21 cm. The width 44 of each groove 26 is essentially constant over the entire groove length and is approximately 15 cm, whereas the width 46 of the cathode blocks 20 is each approximately 42 cm.

In dem vorliegenden Ausführungsbeispiel sind mehrere Anoden 18 und mehrere Kathodenblöcke 20 derart übereinander angeordnet, dass jede Anode 18 in der Breite zwei nebeneinander angeordnete Kathodenblöcke 20 abdeckt und in der Länge die Hälfte eines Kathodenblockes 20 abdeckt, wobei jeweils zwei nebeneinander angeordnete Anoden 18 die Länge eines Kathodenblockes 20 überdecken.In the present exemplary embodiment, several anodes 18 and several cathode blocks 20 are arranged one above the other in such a way that each anode 18 covers two adjacent cathode blocks 20 in width and covers half of a cathode block 20 in length, with two adjacent anodes 18 each having the length of one Cover cathode block 20.

Die Fig. 2 zeigt den in der Fig. 1 dargestellten Kathodenblock 20 im Längsschnitt. Wie aus der Fig. 2 ersichtlich, läuft die in ihrem Längsschnitt betrachtete Nut 26 zur Mitte des Kathodenblocks 20 hin in der Form eines Dreiecks zu, wodurch eine im Wesentlichen gleichmäßige elektrische vertikale Stromdichte über die gesamte Kathodenlänge hinweg gewährleistet wird. Die Vertiefung 36 verläuft dabei wie in der Fig. 2 durch die entsprechend gekennzeichnete Linie angedeutet parallel zu der horizontalen Richtung, d.h. parallel zu der Oberfläche der der Nut 26 gegenüberliegenden Seite des Kathodenblocks 20. Die in der Fig. 2 der besseren Übersichtlichkeit halber nicht dargestellte Stromschiene 28 ist in dem vorliegenden Ausführungsbeispiel barrenförmig ausgebildet und weist einen rechtwinkligen Längsschnitt auf, so dass zwischen der Stromschiene und dem Nutboden 34 ein zur Mitte der Nut 26 hin größer werdender Zwischenraum besteht, der entweder durch Gusseisen 38 oder durch zusätzliche mit der Stromschiene 28 verbundene Metallplatten ausgefüllt sein kann.The Fig. 2 shows the one in the Fig. 1 Cathode block 20 shown in longitudinal section. Like from the Fig. 2 As can be seen, the groove 26 viewed in its longitudinal section tapers towards the center of the cathode block 20 in the shape of a triangle, thereby ensuring a substantially uniform electrical vertical current density over the entire cathode length. The depression 36 runs like in the Fig. 2 indicated by the correspondingly marked line parallel to the horizontal direction, ie parallel to the surface of the side of the cathode block 20 opposite the groove 26. The in the Fig. 2 For the sake of clarity, busbar 28, not shown, is designed in the form of a bar in the present exemplary embodiment and has a rectangular longitudinal section, so that between the busbar and the groove bottom 34 there is a space that increases towards the middle of the groove 26, which is either through cast iron 38 or through Additional metal plates connected to the busbar 28 can be filled.

Die in den Fig. 3 und 4 im Längsschnitt und Querschnitt gezeigte Kathodenanordnung und Kathodenblock gemäß einem zweiten Ausführungsbeispiel der vorliegenden Erfindung unterscheidet sich von der in den Fig. 1 und 2 gezeigten dadurch, dass in dem Kathodenblock 20 nur eine Nut 26 vorgesehen ist, welche zwei Vertiefungen 36,36' aufweist.The ones in the Fig. 3 and 4 Cathode arrangement and cathode block shown in longitudinal section and cross section according to a second embodiment of the present invention differs from that in the Fig. 1 and 2 shown thereby, that only one groove 26 is provided in the cathode block 20, which has two recesses 36, 36 '.

Ferner zeigen die Fig. 5a bis d beispielhafte Vertiefungen 36, die in einer Nut 26 eines erfindungsgemäßen Kathodenblocks 20 vorgesehen sind, im Querschnitt. Dabei weisen die Vertiefungen 36 jeweils einen im Wesentlichen halbkreisförmigen Querschnitt (Fig. 5a), einen im Wesentlichen trapezförmigen Querschnitt (Fig. 5b) oder einen im Wesentlichen dreieckigen Querschnitt (Fig. 5c) auf. Der Winkel α der Übergangsbereiche 37 zwischen der Wand der Vertiefung 36 und dem angrenzenden Abschnitt der Nutwand 32, von der Innenseite des Kathodenblocks 20 aus gesehen, beträgt dabei in Fig. 5a etwa 90 Grad, in der Fig. 5b etwa 120 Grad und in der Fig. 5c etwa 125 Grad. Die Fig. 5d zeigt eine Ausgestaltung, bei der mehrere wie in der Fig. 5c gezeigte Vertiefungen 36 mit dreieckigem Querschnitt in Tiefenrichtung der Nut 26 aufeinander folgend angeordnet sind, um eine besonders zuverlässige Halterung einer eingesetzten Stromschiene 28 zu bewirken. Die Übergangsbereiche 48 zwischen zwei aneinander angrenzenden Vertiefungen 36 weisen dabei zwischen den Wänden von zwei aneinander angrenzenden Vertiefungen 36, von der Innenseite des Kathodenblocks 20 aus gesehen, einen Winkel ß von etwa 70 Grad auf. Die in den Fig. 5a bis d gezeigten Vertiefungen 36 erstrecken sich jeweils senkrecht in die die Nut 26 begrenzende Seitenwand 32 des Kathodenblocks 20, so dass sie mit in den Vertiefungen 36 aufgenommenem Gusseisen eine Fixierung bilden, die in Tiefenrichtung der Nut 26 wirksam ist und eine ungewollte Bewegung der Stromschiene 28 parallel zu der Tiefenrichtung der Nut 26 nach dem Vergießen der Stromschiene 28 mit Gusseisen 38 verhindert, aber eine horizontale Bewegung der mit Gusseisen ummantelten Stromschiene - beispielsweise infolge einer Ausdehnung der mit Gusseisen ummantelten Stromschiene infolge eine großen Temperaturänderung - zulässt.Furthermore, they show Fig. 5a to d exemplary depressions 36, which are provided in a groove 26 of a cathode block 20 according to the invention, in cross section. The depressions 36 each have a substantially semicircular cross section ( Fig. 5a ), a substantially trapezoidal cross-section ( Fig. 5b ) or a substantially triangular cross section ( Fig. 5c ) on. The angle α of the transition regions 37 between the wall of the recess 36 and the adjacent section of the groove wall 32, seen from the inside of the cathode block 20, is in Fig. 5a about 90 degrees, in the Fig. 5b about 120 degrees and in the Fig. 5c about 125 degrees. The Fig. 5d shows an embodiment in which several as in the Fig. 5c shown depressions 36 with a triangular cross section are arranged one after the other in the depth direction of the groove 26 in order to ensure a particularly reliable holding of an inserted busbar 28. The transition areas 48 between two adjacent depressions 36 have an angle β of approximately 70 degrees between the walls of two adjacent depressions 36, viewed from the inside of the cathode block 20. The ones in the Fig. 5a to d The depressions 36 shown each extend vertically into the side wall 32 of the cathode block 20 delimiting the groove 26, so that they form a fixation with cast iron accommodated in the depressions 36, which is effective in the depth direction of the groove 26 and prevents unwanted movement of the busbar 28 parallel to the depth direction of the groove 26 after the busbar 28 has been cast with cast iron 38 is prevented, but a horizontal movement of the cast iron-coated busbar - for example as a result of an expansion of the cast iron-coated busbar as a result of a large temperature change - is permitted.

BezugszeichenlisteReference symbol list

1010
Aluminium-ElektrolysezelleAluminum electrolytic cell
1212
KathodenanordnungCathode arrangement
1414
Aluminiumschmelzealuminum melt
1616
Kryolith-Aluminiumoxid -SchmelzeCryolite-alumina melt
1818
Anodeanode
2020
Kathodenblockcathode block
2222
StampfmassenfugeRammed compound joint
2424
StampfmasseRamming mass
2626
NutNut
2828
Stromschienebusbar
3232
SeitenwandSide wall
3434
Bodenwandfloor wall
36, 36'36, 36'
Vertiefungdeepening
3737
Übergangsbereich zwischen der Wand der Vertiefung und dem angrenzenden Abschnitt der NutwandTransition area between the wall of the recess and the adjacent section of the groove wall
3838
Gusseisencast iron
3939
Umhüllungwrapping
4040
PfeilArrow
4242
gestrichelte Liniedashed line
4444
Breite der Nut 26Width of the groove 26
4646
Breite des Kathodenblocks 20Width of cathode block 20
4848
Übergangsbereich zwischen zwei aneinander angrenzenden VertiefungenTransition area between two adjacent depressions
αα
Winkel zwischen der Wand der Vertiefung und dem angrenzenden Abschnitt der NutwandAngle between the wall of the recess and the adjacent portion of the groove wall
ßß
Winkel zwischen den Wänden von zwei aneinander angrenzenden VertiefungenAngle between the walls of two adjacent depressions

Claims (7)

  1. Cathode block (20) for an aluminium electrolytic cell based on carbon and/or graphite, wherein the cathode block (20) has at least one slot (26) extending in the longitudinal direction of the cathode block (20) for accommodating at least one busbar (28), wherein at least one of the at least one slot (26) has a varying depth when viewed along the length of the cathode block (20), wherein the at least one slot (26) of varying depth comprises a delimiting wall (32, 34) of the cathode block (20), wherein at least one recess (36, 36') having a semicircular, triangular, rectangular or trapezoidal cross section is provided in at least one side wall (32) and extends horizontally in the longitudinal direction of the cathode block (20), wherein horizontally means that the at least one recess (36, 36') has, at each of its points, an angle of less than 5° with respect to the plane of the cathode block (20) which extends in the direction of the longitudinal axis of the cathode block (20) at least approximately along the entire length of the at least one slot and is parallel to the surface of the side of the cathode block (20) opposite the slot.
  2. Cathode block (20) according to claim 1, characterised in that at least one of the at least one slot (26) of varying depth has a shallower depth at its longitudinal ends than in its centre.
  3. Cathode block (20) according to either claim 1 or claim 2, characterised in that the wall (32, 34) delimiting the at least one slot (26) of varying depth comprises a bottom wall (34) and two side walls (32), each side wall (32) having at least one recess (36, 36') which extends horizontally in the longitudinal direction of the cathode block (20).
  4. Cathode block (20) according to claim 3, characterised in that at least one of the at least one recess (36, 36') has a depth of from 0.5 mm to 40 mm.
  5. Cathode block (20) according to claim 4, characterised in that at least one of the at least one recess (36, 36') has an opening width of from 2 mm to 40 mm based on the height of the cathode block (20).
  6. Cathode assembly (12) which contains at least one cathode block (20) according to at least one of claims 1 to 5, wherein at least one busbar (28) is provided in at least one of the at least one slot (26) of varying depth in the at least one cathode block (20), which busbar has, at least in regions, a coating (39) of cast iron (38) or ramming mix which engages, at least in portions, in the at least one recess (36, 36').
  7. Use of a cathode block (20) according to at least one of claims 1 to 5 or of a cathode assembly (12) according to claim 6 for carrying out fused-salt electrolysis to produce metal, preferably to produce aluminium.
EP14721300.3A 2013-04-26 2014-04-25 Cathode block having a slot with varying depth and a securing system Active EP2989235B9 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PL19166841T PL3546620T3 (en) 2013-04-26 2014-04-25 Cathode assembly having a cathode block having a slot with varying depth and a securing system
EP19166841.7A EP3546620B1 (en) 2013-04-26 2014-04-25 Cathode assembly having a cathode block having a slot with varying depth and a securing system
PL14721300T PL2989235T3 (en) 2013-04-26 2014-04-25 Cathode block having a slot with varying depth and a securing system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102013207737.8A DE102013207737A1 (en) 2013-04-26 2013-04-26 Cathode block with a groove of varying depth and a fixing device
PCT/EP2014/058478 WO2014174089A1 (en) 2013-04-26 2014-04-25 Cathode block having a slot with varying depth and a securing system

Related Child Applications (2)

Application Number Title Priority Date Filing Date
EP19166841.7A Division EP3546620B1 (en) 2013-04-26 2014-04-25 Cathode assembly having a cathode block having a slot with varying depth and a securing system
EP19166841.7A Division-Into EP3546620B1 (en) 2013-04-26 2014-04-25 Cathode assembly having a cathode block having a slot with varying depth and a securing system

Publications (3)

Publication Number Publication Date
EP2989235A1 EP2989235A1 (en) 2016-03-02
EP2989235B1 EP2989235B1 (en) 2019-06-12
EP2989235B9 true EP2989235B9 (en) 2023-11-15

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EP19166841.7A Active EP3546620B1 (en) 2013-04-26 2014-04-25 Cathode assembly having a cathode block having a slot with varying depth and a securing system
EP14721300.3A Active EP2989235B9 (en) 2013-04-26 2014-04-25 Cathode block having a slot with varying depth and a securing system

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EP (2) EP3546620B1 (en)
JP (1) JP6808485B2 (en)
CN (1) CN105247109B (en)
CA (1) CA2910233C (en)
DE (1) DE102013207737A1 (en)
PL (2) PL2989235T3 (en)
RU (1) RU2727621C2 (en)
UA (1) UA117481C2 (en)
WO (1) WO2014174089A1 (en)

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DE102016210693A1 (en) 2016-06-15 2017-12-21 Sgl Cfl Ce Gmbh Cathode block having a novel groove geometry
CN106929688B (en) * 2017-04-17 2018-08-17 新疆大学 A kind of apparatus and method preparing rafifinal using aluminium lime-ash
CN106894052B (en) * 2017-04-19 2018-10-16 新疆大学 A kind of conjuncted-multilevel aluminum electrolysis unit and its application method preparing rafifinal

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Publication number Priority date Publication date Assignee Title
CH544578A (en) * 1973-02-09 1973-11-30 Alusuisse Electrode block for an electrolysis cell with a current conducting bar in a groove in the electrode block
FR2318244A1 (en) * 1975-07-17 1977-02-11 Savoie Electrodes Refactaires PROCESS FOR JOINING METAL BARS WITH CARBON BLOCKS
EP0052577B1 (en) * 1980-11-19 1984-02-15 Schweizerische Aluminium AG Anchorage for a cathode bar
GB8331769D0 (en) * 1983-11-29 1984-01-04 Alcan Int Ltd Aluminium reduction cells
PL1845174T3 (en) 2006-04-13 2011-10-31 Sgl Carbon Se Cathodes for aluminium electrolysis cell with non-planar slot design
RU2401887C1 (en) * 2009-07-20 2010-10-20 Федеральное государственное образовательное учреждение высшего профессионального образования "Сибирский федеральный университет" Cathode assembly of aluminium electrolysis cell
DE102011004009A1 (en) 2011-02-11 2012-08-16 Sgl Carbon Se Cathode arrangement and cathode block with a guide groove having a groove
CN102181883B (en) * 2011-04-11 2012-10-03 中南大学 Aluminum electrolysis cell cathode structure of horizontal current in controllable regulation aluminum liquid

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WO2014174089A1 (en) 2014-10-30
CN105247109B (en) 2018-06-05
RU2015150375A (en) 2017-06-02
EP2989235A1 (en) 2016-03-02
EP3546620A1 (en) 2019-10-02
DE102013207737A1 (en) 2014-10-30
CN105247109A (en) 2016-01-13
JP6808485B2 (en) 2021-01-06
PL3546620T3 (en) 2022-03-28
EP3546620B1 (en) 2021-12-22
RU2727621C2 (en) 2020-07-22
RU2020114123A (en) 2020-06-10
RU2020114123A3 (en) 2021-11-22
UA117481C2 (en) 2018-08-10
EP2989235B1 (en) 2019-06-12
PL2989235T3 (en) 2019-10-31
JP2016516905A (en) 2016-06-09
CA2910233C (en) 2018-01-16
CA2910233A1 (en) 2014-10-30

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