A cathode current collector and connector assembly for an aluminum electrolysis cell; corresponding component set and aluminum electrolysis cell

Abstract

The invention relates to a cathode current collector and connector assembly, a kit of parts for manufacturing the cathode current collector, and an aluminum electrolysis cell including the cathode current collector and connector assembly.

Description

Field of the Invention

[0001] The present invention relates to a cathode current collector and a connector assembly, a kit of parts for manufacturing a cathode current collector, and an aluminum electrolysis cell including the cathode current collector and the connector assembly. Background of the Invention

[0003] Aluminum is produced by electrolyzing alumina dissolved in a cryolite-based electrolyte at temperatures up to 1000 °C by the Hall-Héroult process. A typical Hall-Héroult cell consists of a steel shell, a refractory insulating lining, and a carbon cathode that holds the liquid metal. The cathode is composed of a plurality of cathode blocks, where collector bars are embedded at the bottom of the cathode blocks to extract the current flowing through the cell.

[0004] Many patent publications have proposed different methods for minimizing the voltage drop between the liquid metal and the end of the current collector bar. WO 2008 / 062318 discloses using a highly conductive material as a supplement to the existing steel current collector bar, with reference to WO 02 / 42525, WO 01 / 63014, WO 01 / 27353, WO 2004 / 031452, and WO 2005 / 098093, which disclose solutions using copper inserts inside the current collector steel bar. US Patent 4,795,540 divides the cathode as well as the current collector bar into sections. WO 2001 / 27353 and WO 2001 / 063014 use highly conductive materials inside the current collector bar. US2006 / 0151333 covers the use of different electrical conductivities in the current collector bar. WO 2007 / 118510 proposes increasing the cross-section of the current collector bar as it moves towards the center of the cell to change the current distribution at the surface of the cathode. US 5,976,333 and US 6,231,745 propose using copper inserts inside the steel current collector bar. EP 2 133 446 A1 describes a cathode block arrangement for modifying the surface geometry of the cathode in order to stabilize the waves at the surface of the metal pad and thus minimize the ACD (anode-to-cathode distance). WO 2011 / 148347 describes a carbon cathode for an aluminum production cell, which includes highly conductive inserts sealed in a housing within the carbon cathode. These inserts change the conductivity of the cathode body but do not participate in the current collection and extraction of the current collector bar. The conductivity of molten cryolite is very low, and due to the formation of magneto-hydrodynamic instabilities, the ACD cannot be reduced too much, and magneto-hydrodynamic instabilities result in waves at the metal-bath (metal-cryolite electrolyte) interface. The presence of waves causes a loss in the current efficiency of the process and does not allow the energy consumption to be reduced below a critical value. On average, in the aluminum industry, the current density is such that the voltage drop in the ACD is minimized at 0.3 V / cm. Since the ACD is 3 cm to 5 cm, the voltage drop in the ACD is typically 1.0 V to 1.5 V. The magnetic field inside the liquid metal is the result of the current flowing in the external busbars and the internal current. The internal local current density inside the liquid metal is mainly defined by the cathode geometry and its local conductivity. The magnetic field and the current density generate a Lorentz force field, which itself generates the metal surface profile, and the metal velocity field defines the basic environment for the stability of the magneto-hydrodynamic cell. The cell stability can be expressed as the ability to reduce the ACD without generating unstable waves at the surface of the metal pad. The stability level depends on the current density and the induction of the magnetic field, but also on the shape of the liquid metal pool. The shape of the pool depends on the surface and ledge shape of the cathode. The prior art solutions respond to a given level of the desired magneto-hydrodynamic state to achieve good cell stability (low ACD), but the solutions using copper inserts usually require complex machining processes.

[0005] Therefore, in recent years, there has been a trend to replace steel current collector bars equipped with copper inserts with pure copper current collector bars. For example, WO 2016 / 079605 discloses a highly conductive current collector bar that includes a central portion located below the central portion of a carbon cathode, typically directly in a cathode slot or via hole or using a U-shaped profile as a support. At least the upper outer surface of this central portion of the highly conductive current collector bar is in direct electrical contact with the carbon cathode, or in contact with the carbon cathode through a conductive interface formed by a conductive adhesive and / or a conductive flexible foil or a conductive flexible sheet applied to the surface of the highly conductive current collector bar. The material of the highly conductive current collector bar is selected from copper, aluminum, silver, and their alloys, and includes one or two outer portions positioned adjacent to one or both sides of the central portion and on one or both sides of the central portion; and one or more terminal portions extending outward from the outer portion. These terminal portions of the highly conductive current collector bar are each connected in series electrically to a steel conductor bar having a cross-sectional area greater than that of the highly conductive current collector bar, the steel conductor bar extending outward, and the terminal portions of this current collector and connector assembly of the steel conductor bar serve as cathode connection sites to an external current supply bus.

[0006] In aluminum production equipment, multiple cells are arranged in rows and connected in series electrically. A busbar system provides an electrical connection from the cathode of an upstream reduction cell to the anode of a downstream cell, and this electrical connection is formed by at least one horizontal rigid beam supporting at least one horizontal conductive rod, the horizontal conductive rod including an anode frame to which an anode suspension shaft is attached. Typically, each cell includes more than one longitudinally arranged parallel cathode current collector and connector assembly, and each assembly includes two connection sites arranged at the ends of the assembly. The connection sites are electrically connected to the supply busbar to enable the flow of current. In particular, due to the deviated path lengths of the current from different cathode connection sites to the anode of the downstream cell, non-uniform current distribution is observed within the busbar system, and thus non-uniform current distribution is observed in the cathodes, where the current collector bars have different current pickups. Therefore, efforts have been made to improve the current distribution by modifying the busbar design, such as by adjusting the required path lengths, grouping the cathode bars into common busbar sections, or using busbars with different cross-sections.

[0007] However, modifying the busbar structure can be laborious and expensive and cannot be carried out in existing cells, which is why there is still a need for improvements in simple and effective cell designs to compensate for unbalanced current flow, which can lead to asymmetric wear behavior, unstable cell performance, and related detrimental effects on cell efficiency.

[0008] Object of the Invention

[0009] Accordingly, the object of the present invention is to provide a cathode current collector and connector assembly for an aluminum electrolysis cell, which has high and stable performance, and which can perform electrolysis with a permanent low contact resistance and a low voltage drop.

[0010] Description of the Invention

[0011] The above problems are solved by a cathode current collector and connector assembly for an aluminum electrolysis cell, the cathode current collector and connector assembly comprising

[0012] a1) a first copper or copper alloy current collector system with an optional protective steel layer cladding,

[0013] a2) a second copper or copper alloy current collector system with an optional protective steel layer cladding,

[0014] b) at least one longitudinal carbonaceous cathode having at least one groove extending in the longitudinal direction of the carbonaceous cathode for receiving at least a part of a1) and a2),

[0015] wherein a1) is at least partially disposed in the at least one groove of b) along the longitudinal direction of the carbonaceous cathode over a length L1 having a first part a 1,1 ) and

[0016] wherein a2) is at least partially disposed in the at least one groove of b) along the longitudinal direction of the carbonaceous cathode over a length L2 having a first part a 2,1 ),

[0017] wherein the part of b) extending in the longitudinal direction over length L1 is defined as the first part of b), which is designated as b1), and

[0018] wherein the part of b) extending in the longitudinal direction over length L2 is defined as the second part of b), which is designated as b2),

[0019] wherein the cathode current collector and connector assembly includes a first connection site,

[0020] wherein the cathode current collector and connector assembly includes a second connection site,

[0021] wherein the first connection site and the second connection site are electrically connectable to an external supply busbar,

[0022] Optionally :

[0023] c1) a first conductor element that electrically interconnects a1) and the first connection site,

[0024] ​c2) A second conductor element, which is electrically interconnected between a2) and a second connection site, wherein

[0025] The sum of the resistivities of a1), b1) and optionally included c1) is different from the sum of the resistivities of a2), b2) and optionally included c2).

[0026] The cathode current collector and connector assembly includes a longitudinal carbon cathode having at least one groove in at least one of the longitudinal surfaces recessed in the longitudinal direction. In at least one groove, at least two current collector systems are at least partially arranged. In the case where at least two current collector systems are arranged in a single groove, the current collector systems are electrically separated, for example, by an insulating material. Electrical contact between the carbon cathode and the current collector can be achieved over the entire embedding area. The assembly may also include one or more conductor elements, which preferably include or consist of steel. Preferably, the terminal portion of the current collector (e.g., a current collecting bar) is electrically connected to the conductor element. That is, in the context of the present invention, the term "cathode current collector and connector assembly" encompasses both embodiments without conductor elements (usually denoted as "cathode current collector assembly") and embodiments with conductor elements (usually denoted as "cathode current collector and connector assembly").

[0027] The above-described split cell design (in the longitudinal direction) of the two halves of the current collector and connector assembly includes (at least) two connection sites, which are located at the current collector system or the conductor element of each respective half. Each connection site can be electrically connected to an external power supply bus. Current flows from the carbon cathode into the copper current collector system of each half, and then flows into the bus via the optional conductor element through the connection site. Preferably, the connection site is located at the current collector (or the conductor element, in the case where the assembly includes one or more conductor elements), especially at the corresponding terminal portion.

[0028] The groove and the corresponding ("negative") current collector system can have different shapes. Generally, the current collector system is rod-shaped, especially rectangular rod-shaped, however, oval or circular forms are also possible.

[0029] The current collector system can consist of one or more elements, which are especially rod-shaped elements. Preferably, the current collector system includes at least two longitudinal rectangular rod elements, which are spaced apart by a thermal expansion gap or an insulating material.

[0030] The "sum of the resistivities" also includes the contact resistivity present at the interface between the elements a1), b1) and optionally included c1), and correspondingly, the contact resistivity present at the interface between a2), b2) and optionally included c2).

[0031] According to the present invention, the term "carbonaceous" means all types of materials based on anthracite and / or graphite and / or coke, whether these cathodes are baked or graphitized.

[0032] In a preferred embodiment of the present invention, the cathode current collector assembly is configured in such a way that in the operating position of the cathode current collector assembly in the electrolytic cell, the groove is arranged at the bottom side of the cathode current collector assembly.

[0033] In a preferred embodiment of the present invention, the cathode is a rectangular cathode block.

[0034] Preferably, the current collector system has a bar shape, most preferably a rectangular bar shape.

[0035] Preferably, the difference between the sum of the resistivities of a1), b1) and optionally included c1) and the sum of the resistivities of a2), b2) and optionally included c2) is ≥ 1%, more preferably ≥ 2%, even more preferably ≥ 3% and most preferably ≥ 4%, but also preferably less than 30%. The foregoing values refer to the higher resistivity value.

[0036] In sharp contrast to the established teachings of the prior art that propose symmetric cell designs, the inventors have found that by using an asymmetric design of the current collector and connector assembly, the current pick-up at the two connection sites of the current collector and connector assembly can be equalized. Thereby, an aluminum electrolytic cell with enhanced current efficiency is obtained, which in turn reduces the total specific energy consumption. In addition, the erosion of the cathode block is more homogeneous, reducing the asymmetry of the typical so-called W-shaped erosion. Therefore, the cathode current collector and connector assembly of the present invention enables an aluminum electrolytic cell to be obtained, which has higher and more stable performance, and which can electrolyze with a permanent low contact resistance and a low cathode voltage drop. By means of the asymmetric unit design of the present invention, unbalanced current flow can be compensated for without the need to implement a complex busbar design.

[0037] The first option found by the inventors that affects the sum of the resistivities is to modify the amount of copper or copper alloy and / or the geometry of the current collector systems a1) and a2).

[0038] Therefore, in a preferred embodiment, a deviated amount of copper or copper alloy is used in the current collector systems a1) and a2). A significantly reduced amount of copper or copper alloy on one side of the cathode current collector and connector assembly will result in a higher resistivity, which means that side will have resistance, which in turn reduces the current pick-up at the corresponding connection site.

[0039] In a preferred embodiment of the present invention, the amount of the copper or copper alloy in a1) ≤ 0.9 times the mass of the copper or copper alloy in a2), more preferably ≤ 0.8 times the mass of the copper or copper alloy in a2), even more preferably ≤ 0.7 times the mass of the copper or copper alloy in a2), and most preferably ≤ 0.6 times the mass of the copper or copper alloy in a2), but preferably also ≥ 0.3 times the mass of the copper or copper alloy in a2).

[0040] The same effect can be achieved by using the deviating geometries of a1) and a2). For example, in the case where the current collector system is rod-shaped, the cross-sectional area of the a1) rod can be smaller than the cross-sectional area of the a2) rod, or vice versa, thereby increasing the resistivity on one side of the current collector and the connector assembly. In this case, preferably, the cross-sectional area of the a1) rod ≤ 0.9 times the cross-sectional area of the a2) rod, more preferably ≤ 0.8 times the cross-sectional area of the a2) rod, even more preferably ≤ 0.7 times the cross-sectional area of the a2) rod, and most preferably ≤ 0.6 times the cross-sectional area of the a2) rod, but preferably also ≥ 0.3 times the cross-sectional area of the a2) rod.

[0041] Another option for increasing or decreasing the resistivity on one side of the current collector and the connector assembly is to adjust the contact surface between the cathode and the current collector system. This can be achieved by changing the length by which the current collector system extends in the longitudinal direction of the groove of the cathode. As the lengths L1 and L2 increase, a higher contact surface is obtained, thereby reducing the contact resistance. In a preferred embodiment of the present invention, L1 ≤ 0.9*L2, more preferably ≤ 0.8*L2, even more preferably ≤ 0.7*L2, and most preferably ≤ 0.6*L2, but preferably also ≥ 0.3*L2.

[0042] In a preferred embodiment of the present invention, the contact surface between a1) and b1) ≤ 0.9 times the contact surface between a2) and b2), more preferably ≤ 0.8 times the contact surface between a2) and b2), even more preferably ≤ 0.7 times the contact surface between a2) and b2), and most preferably ≤ 0.6 times the contact surface between a2) and b2), but preferably also ≥ 0.3 times the contact surface between a2) and b2).

[0043] Another option for increasing or decreasing the resistivity on one side of the current collector and the connector assembly is to use at least partial isolation of a1) and / or a2).

[0044] In a preferred embodiment of the present invention, a1) and / or a2) are at least partially electrically insulated, preferably electrically insulated with a refractory material such as alumina, silica, silicon carbide, or boron nitride, and the refractory material is preferably in the form of a sheet.

[0045] In a preferred embodiment of the present invention, the surface of the electrically insulated a1) is ≤ 0.9 times the surface of the electrically insulated a2), more preferably ≤ 0.8 times the surface of the electrically insulated a2), even more preferably ≤ 0.7 times the surface of the electrically insulated a2), and most preferably ≤ 0.6 times the surface of the electrically insulated a2), but preferably also ≥ 0.3 times the surface of the electrically insulated a2).

[0046] In another preferred embodiment, the current collector system is rod-shaped, and a1) and a2) are surrounded by an electrically insulating layer over a length L iso-1 (a1)) and L iso-2 (a2)), where L iso-1 ≤ 0.9 * L iso-2 , more preferably ≤ 0.8 * L iso-2 , even more preferably ≤ 0.7 * L iso-2 and most preferably ≤ 0.6 * L iso-2 , but preferably also ≥ 0.3 * L iso-2 .

[0047] Another option for increasing or decreasing the resistivity on one side of the current collector and connector system is to use different copper alloys.

[0048] Thus, in a preferred embodiment of the present invention, the specific electrical conductivities of a1) and a2) of copper or copper alloy are different.

[0049] In a preferred embodiment of the present invention, the cathode current collector and connector assembly includes one or more conductor elements, which are preferably arranged at the terminal part of the current collector system. Both of the optional conductor elements c1) and c2) preferably each include at least one recess, and a1) is at least partially arranged in the recess of c1) having a second part a 1,2 ), and / or c2) is at least partially arranged in the recess of c2) having a second part a 2,2 ). The type of the conductor element, i.e., its composition, as well as its size and geometry also affect the resistivity of the sides of the current collector and connector assembly.

[0050] A simple and effective way to adjust the resistivity of the sides of the current collector and connector assembly is to change the contact surface between this optional conductor element and the current collector system. This has proven to be particularly preferred because the design limitations are relatively low at this position.

[0051] In a preferred embodiment of the present invention, the contact surface between a1) and c1) ≤ 0.9 times the contact surface between a2) and c2), more preferably ≤ 0.7 times the contact surface between a2) and c2), even more preferably ≤ 0.4 times the contact surface between a2) and c2), and most preferably ≤ 0.2 times the contact surface between a2) and c2), but preferably also ≥ 0.1 times the contact surface between a2) and c2).

[0052] Preferably, when the second part a 1,2 )(correspondingly a 2,2 )) of the copper current collector system is arranged in the recess of the steel conductor element, the recess of the steel bar is formed to block the movement of the second part of the copper current collector system in two or more, more preferably three or more, even more preferably four or more or even five spatial directions under normal conditions according to DIN 1341.

[0053] Preferably, the recess of the steel bar is formed to block the movement of the second part of the current collector system in one or more additional spatial directions under the operating conditions of the Hall-Héroult process compared to normal conditions.

[0054] Preferably, the recess of the steel bar is formed to block the movement of the second part of the current collector system by friction and / or form-fit.

[0055] In a particularly preferred embodiment, the recess has the form of a pocket that blocks movement in four (one-sided open pocket) or five (fully enclosed pocket) of the six spatial directions. As the movement constraint increases, the pressure increases, and in such an embodiment, the above effects are enhanced, and a tight friction and form-fit can be obtained. The beneficial effect is maximized when the recess is a pocket that completely surrounds the steel bar.

[0056] To fix the copper current collector system in its position, the steel conductor element can include several elements. For example, the pocket can be formed by two half-sections that can be assembled to surround the second part of the current collector system. Another option is to create a pocket that individually blocks movement in four spatial directions, place the second part of the current collector system and cover the pocket with a steel plate that can be welded or otherwise connected to the rest of the steel conductor element.

[0057] After arranging the second part of the copper current collector system in the recess (e.g., in the form of a pocket), a covering element can be used to completely "seal" the recess, i.e., cover the accessible gap between the copper current collector system inside the recess and the steel conductor element.

[0058] The inventors have observed that the combination of the above measures is conducive to obtaining a balanced current distribution. To change the resistivity, it is particularly preferred to use the contact of the current collector system and the conductor system in the form of cavities (conductor elements) and the corresponding negative form (current collector system). By using cavities of different sizes or inserting the current collector system asymmetrically on both sides, a deviated resistivity can be obtained in a simple and effective manner, which even enables simple modification of the existing current collector and connector assemblies.

[0059] In a preferred embodiment of the present invention, the cathode current collector and the connector assembly are at least partially coated with an optional protective steel layer cladding, where a 1,2 ) and / or a 2,2 ) is at least partially free, preferably completely free, of the optional protective steel layer cladding.

[0060] Preferably, at least 50%, more preferably at least 60%, even more preferably at least 70%, and most preferably at least 80% of the surface of the current collector system a 1,2 ) and / or a 2,2 ) is coated with the protective steel layer cladding. In a particularly preferred embodiment, the surface of the current collector system except for the second part is completely coated with the protective steel cladding.

[0061] Preferably, at least 50%, more preferably at least 60%, even more preferably at least 70%, and most preferably at least 80% of the surface of the first part of the current collector system is coated with the protective steel layer. In a particularly preferred embodiment, the surface of the first part of the current collector system is completely coated. Thus, the harmful effects of the diffusion of aluminum or other products generated during the operation of the electrolytic cell can be reduced.

[0062] Preferably, the volume ratio of the copper or copper alloy of the current collector system to the thin protective steel layer is at least 200%, and preferably at least 300%, or more preferably at least 400%.

[0063] Preferably, the thin protective steel layer has a thickness of 0.05 mm to 6 mm, more preferably 0.15 mm to 4 mm, and even more preferably 1.5 mm to 3 mm.

[0064] The thin protective steel layer preferably comprises or consists of steel selected from the following: carbon steel, low-carbon steel, chromium-based steel, nickel-based steel, or chromium-nickel-based steel or alloy steel.

[0065] In a preferred embodiment of the present invention, the copper or copper alloy is in the form of a bar with a rectangular cross-section, and the bar is protected with a thin protective steel layer at least on the side facing the cathode, preferably on all sides facing the cathode.

[0066] In the case where the current collector system includes a steel protective layer, i.e., is at least partially coated with a steel protective layer, the protective steel layer is in direct contact with the wall of the groove of the carbonaceous cathode.

[0067] Preferably, the thin protective steel layer is coated with an additional top layer and / or bottom layer of copper, nickel, and / or chromium and / or a graphite coating or foil layer, where more preferably, the additional top layer and / or bottom layer has a thickness of 1 μm to 1 mm.

[0068] The surface of the current collector system can be rough or provided with recesses such as grooves or protrusions such as fins or ribs to increase the surface area between the cathode and the current collector system, thereby enhancing the contact between the components.

[0069] In a preferred embodiment of the present invention, the current collector system is at least partially coated with an insulator, in particular a sheet of insulating material such as alumina, insulating glue or cement, or any insulating material capable of withstanding up to 1200 °C.

[0070] In a preferred embodiment of the present invention, a1) includes a third part a 1,3 ) that is different from the first part and the second part, and this third part a 1,3 ) is arranged outside the groove of the carbonaceous cathode and the recess of the optional steel conductor element, and wherein this third part is surrounded by a protective shell. In addition, a2) preferably includes a third part a 2,3 ) that is different from the first part and the second part, and this third part a 2,3 ) is arranged outside the groove of the carbonaceous cathode and the recess of the optional steel conductor element, and wherein this third part is surrounded by a protective shell. Preferably, the protective shell includes a material selected from SiC, ramming paste, steel cover plate, refractory material, or a mixture of the foregoing materials. Most preferably, it is a shell having an inner layer of SiC, ramming paste, refractory material, or a mixture of the foregoing materials and an outer steel cover layer, whereby the inner layer is arranged between the current collector system and the outer steel cover layer.

[0071] The present invention also relates to a component kit, i.e., a system of independent components, which component kit includes

[0072] a1) a first copper or copper alloy current collector system with an optional protective steel layer cladding,

[0073] a2) a second copper or copper alloy current collector system with an optional protective steel layer cladding,

[0074] b) at least one longitudinal carbonaceous cathode having at least one groove extending in the longitudinal direction of the carbonaceous cathode for receiving at least a part of a1) and a2),

[0075] Optionally :

[0076] c1) A first conductor element,

[0077] c2) A second conductor element,

[0078] wherein the sum of the resistivities of a1), b1) and optionally included c1) is different from the sum of the resistivities of a2), b2) and optionally included c2).

[0079] The invention also relates to an aluminum electrolysis cell comprising a cathode current collector and a connector assembly of the invention and at least one supply busbar, wherein the cathode current collector and the connector assembly are electrically connected to the at least one supply busbar via a first connection site and a second connection site.

[0080] Preferably, the difference in current pick-up at the two connection sites is ≤ 4%, more preferably ≤ 3%, even more preferably ≤ 2%, and most preferably ≤ 1%. The aforementioned values refer to the higher current value.

[0081] The invention also relates to an aluminum electrolysis cell comprising a cathode current collector and a connector assembly having two connection sites and at least one supply busbar, wherein the cathode current collector and the connector assembly are electrically connected to the at least one supply busbar via a first connection site and a second connection site, preferably electrically connected to the at least one supply busbar by means of flexible copper or aluminum, wherein the difference in current pick-up at the two connection sites is ≤ 5%, more preferably ≤ 3%, even more preferably ≤ 2%, and most preferably ≤ 1%. The aforementioned values refer to the higher current value.

[0082] The invention also relates to an aluminum electrolysis apparatus comprising the battery of the invention as described above.

[0083] The invention also relates to the use of an asymmetric resistivity distribution in a cathode current collector and a connector assembly for compensating for unbalanced upstream and downstream current flows in an aluminum electrolysis cell. Examples

[0084] The invention will now be explained in more detail by means of specific embodiments and with the aid of the drawings.

[0085] Examples of the invention

[0086] The cathode block with dimensions of 550 mm × 450 mm × 3200 mm (width × height × length) is equipped with two central rectangular grooves with dimensions of 40 mm × 135 mm (width × depth). The first groove has a length of 1200 mm from the first end of the cathode block, and the second groove has a length of 1400 mm from the second end of the cathode block. Two rectangular current collector bars are composed of a copper core with a 2.0 mm thick steel cladding around it, and the steel cladding does not include the bar part accommodated in the steel conductor bar. The lengths of the first current collector bar and the second current collector bar are 1480 mm and 1720 mm, where the dimensions applied inside the cathode block are L1 1180 mm, L2 1380 mm, and the depth accommodated in the steel conductor bar is a 1,2 200 mm and a 2,2 240 mm. The outer dimensions of c1) and c2) are the same, and the distance a from the cathode block to the steel conductor bar 1,3 and a 2,3 are both 100 mm.

[0087] With this design, the difference in current pick-up of the two current collector bars observed in the block is less than 2%.

[0088] Comparative example

[0089] The cathode block with dimensions of 550 mm × 450 mm × 3200 mm (width × height × length) is equipped with two central rectangular grooves with dimensions of 40 mm × 135 mm (width × depth), and the lengths of both from the first end and the second end of the cathode block are 1300 mm. Two rectangular current collector bars are composed of a copper core with a 2.0 mm thick steel cladding around it, and the steel cladding does not include the bar part accommodated in the steel conductor bar. The lengths of the first current collector bar and the second current collector bar are 1620 mm, where the dimensions applied inside the cathode block are L1 1280 mm and L2 1280 mm, and the depth accommodated in the steel conductor bar is a 1,2 240 mm and a 2,2 240 mm. The outer dimensions of c1) and c2) are the same, and the distance a from the cathode block to the steel conductor bar 1,3 and a 2,3 are both 100 mm.

[0090] With this design, the difference in current pick-up of the two current collector bars observed in the block is greater than 5%.

[0091] Drawings

[0092] From the following description of the preferred embodiments and the related drawings, further advantages, features, and possible applications will become apparent. The drawings show:

[0093] Figure 1 show a longitudinal section of an aluminum electrolysis device.

[0094] Figure 2 Shows a longitudinal section of an aluminum electrolysis cell having two anodes as well as a cathode current collector and a connector assembly, the aluminum electrolysis cell being arranged with anodes.

[0095] Figure 3 Shows a longitudinal section of a current collector assembly according to the prior art.

[0096] Figure 4 Shows a longitudinal section of a current collector and connector assembly according to the prior art.

[0097] Figure 5 Shows a longitudinal section of a current collector and connector assembly of the present invention.

[0098] Detailed description

[0099] Figure 1 Depicts a longitudinal section of an aluminum electrolysis apparatus. In the electrolysis apparatus, a rectangular cathode block 1 includes grooves recessed in a horizontal surface, in which two current collector bars 2a and 2b are arranged in the longitudinal direction. Generally, the current collector bars can be in direct contact with the cathode block, or a conductive carbonaceous layer (such as a conductive carbonaceous layer of ramming paste) can be arranged between the surfaces. Each current collector bar is connected to supply busbars (4&5) via connection sites 6a and 6b located at the respective current collector bars.

[0100] Figure 2 Depicts a longitudinal section of an aluminum electrolysis cell having two anodes 3 as well as a cathode current collector and a connector assembly. In the electrolysis cell, a rectangular cathode block 1 includes grooves recessed in a horizontal surface, in which two current collector bars 2a and 2b are arranged in the longitudinal direction. Generally, the current collector bars can be in direct contact with the cathode block, or a conductive carbonaceous layer (such as a conductive carbonaceous layer of ramming paste) can be arranged between the surfaces. Each current collector bar is connected at its terminal portion to a conductor element 7a / 7b preferably made of steel. The connection is achieved by arranging the terminal portion of the current collector bar within a recess of the conductor element. Each conductor element provides connection sites 6a, 6b to be respectively connected to an external supply busbar.

[0101] Figure 3 Depicts a longitudinal section of a current collector assembly according to the prior art. In this assembly, a cathode block 1 includes grooves recessed in a horizontal surface, in which two current collector bars 2a and 2b are arranged in the longitudinal direction. Generally, the current collector bars can be in direct contact with the cathode block, or a conductive carbonaceous layer (such as a conductive carbonaceous layer of ramming paste) can be arranged between the surfaces. Each current collector bar can be connected to an external supply busbar via respective connection sites 6a / 6b. The figure also shows a first part a of a first current collector arranged in the groove 1,1 and a third part a arranged outside the groove 1,3This figure also shows the first part a of the second current collector arranged in the groove 2,1 and the third part a arranged outside the groove 2,3 This figure also depicts the length L1 of the first current collecting bar arranged in the cathode block. This figure also depicts the length L2 of the second current collecting bar arranged in the cathode block. The first part of b) extending in the longitudinal direction along the length L1 is defined as b1, and the second part of b) extending in the longitudinal direction along the length L2 is defined as b2). As can be seen, the cathode current collector assembly is symmetrically constructed in the longitudinal direction, i.e., a 1,1 = a 2,1 a 1,2 = a 2,2 and L1 = L2.

[0102] Figure 4 Depicts a longitudinal section of a current collector and connector assembly according to the prior art. In this assembly, the cathode block 1 includes a groove recessed in the horizontal surface, in which two current collecting bars 2a and 2b are arranged in the longitudinal direction. Generally, the current collecting bars can be in direct contact with the cathode block, or a conductive carbonaceous layer (such as the conductive carbonaceous layer of ramming paste) can be arranged between the surfaces. Each current collecting bar is connected at its terminal part to a conductor element 7a / 7b preferably made of steel. The connection is achieved by arranging the terminal part of the current collecting bar within the recess of the conductor element. The conductor element also provides connection sites 6a / 6b to be connected to an external supply busbar. This figure also shows the first part a of the first current collector arranged in the groove 1,1 the second part a arranged in the recess of the conductor element 1,2 and the third part a arranged outside the groove 1,3 This figure also shows the first part a of the second current collector arranged in the groove 2,1 the second part a arranged in the recess of the conductor element 1,2 and the third part a arranged outside the groove 2,3 This figure also depicts the length L1 of the first current collecting bar arranged in the cathode block. This figure also depicts the length L2 of the second current collecting bar arranged in the cathode block. The first part of b) extending in the longitudinal direction along the length L1 is defined as b1, and the second part of b) extending in the longitudinal direction along the length L2 is defined as b2). As can be seen, the cathode current collector assembly is symmetrically constructed in the longitudinal direction, i.e., a 1,1 = a 2,1 a 1,2 = a 2,2 a 1,3 = a 2,3 and L1 = L2.

[0103] Figure 5Depicts a longitudinal section of a current collector and connector assembly according to the prior art. In this assembly, the cathode block 1 includes a groove recessed in a horizontal surface, in which two current collector bars 2a and 2b are arranged in the longitudinal direction. Generally, the current collector bars can be in direct contact with the cathode block, or a conductive carbonaceous layer (such as the conductive carbonaceous layer of ramming paste) can be arranged between the surfaces. Each current collector bar is connected at its terminal part to a conductor element preferably made of steel. The connection is achieved by arranging the terminal part of the current collector bar within a recess of the conductor element. Each conductor element also provides a connection site 6a / 6b to be connected to an external supply busbar. The figure also shows a first part a of the first current collector arranged in the groove 1,1 , a second part a arranged in the recess of the conductor element 1,2 and a third part a arranged outside the groove 1,3 . The figure also shows a first part a of the second current collector arranged in the groove 2,1 , a second part a arranged in the recess of the conductor element 1,2 and a third part a arranged outside the groove 2,3 . The figure also depicts the length L1 of the first current collector bar arranged in the cathode block. The figure also depicts the length L2 of the second current collector bar arranged in the cathode block. The first part b) extending in the longitudinal direction along the length L1 is defined as b1, and the second part b) extending in the longitudinal direction along the length L2 is defined as b2). As can be seen, the cathode current collector assembly is constructed asymmetrically in the longitudinal direction, because the second part a of the second current collector 2b (denoted as a2)) arranged in the recess of the second conductor element 7b (denoted as c2)) 2,2 is smaller than the second part a of the first current collector 2a (denoted as a1)) arranged in the recess of the first conductor element 7a (denoted as c1)) 1,2 .

[0104] Reference signs

[0105] 1 Cathode block

[0106] 2a Current collector bar a1)

[0107] 2b Current collector bar a2)

[0108] 3 Anode

[0109] 4 Anode busbar part

[0110] 5 Cathode busbar part

[0111] 6a First connection site

[0112] 6b Second connection site

[0113] 7a First conductor element c1)

[0114] 7b second conductor element c2).

Claims

1. A cathode current collector and connector assembly for an aluminum electrolysis cell, the cathode current collector and connector assembly comprising a1) a first copper or copper alloy current collector system with an optional protective steel layer cladding, a2) a second copper or copper alloy current collector system with an optional protective steel layer cladding, b) at least one longitudinal carbonaceous cathode having at least one groove extending in the longitudinal direction of the carbonaceous cathode for receiving at least a portion of a1) and a2), wherein a1) is arranged at least partially in the at least one groove of b) over a length L1 having a first part a 1,1 ) along the longitudinal direction of the carbonaceous cathode, and wherein a2) is arranged at least partially in the at least one groove of b) along the longitudinal direction of the carbonaceous cathode over a length L2 having a first part a 2,1 ) wherein a first portion of b) extending in the longitudinal direction along the length L1 is defined as b1), and wherein a second portion of b) extending in the longitudinal direction along the length L2 is defined as b2), wherein the cathode current collector and connector assembly includes a first connection site that can be electrically connected to an external supply busbar, and wherein the cathode current collector and connector assembly includes a second connection site that can be electrically connected to the supply busbar, optionally ： c1) a first conductor element that electrically interconnects a1) and the first connection site, c2) a second conductor element that electrically interconnects a2) and the second connection site, characterized in that the sum of the resistivities of a1), b1) and optionally included c1) is different from the sum of the resistivities of a2), b2) and optionally included c2).

2. The cathode current collector and connector assembly according to claim 1, wherein the masses of the copper or copper alloy of a1) and a2) are different.

3. The cathode current collector and connector assembly according to any one of the preceding claims, wherein L1 and L2 are different.

4. The cathode current collector and connector assembly according to any one of the preceding claims, wherein a1) and / or a2) are at least partially electrically insulated, preferably electrically insulated with boron nitride.

5. The cathode current collector and connector assembly according to any one of the preceding claims, wherein the geometries of a1) and a2) are different.

6. The cathode current collector and connector assembly according to any one of the preceding claims, wherein the specific conductivities of the copper or copper alloy of a1) and a2) are different.

7. The cathode current collector and connector assembly according to any one of the preceding claims, wherein The cathode current collector and connector assembly includes: c1) and c2), both c1) and c2) each include at least one recess, a1) at least partially disposed in a recess of c1) having a second part a 1,2 ) and a2) is at least partially disposed in a recess of c2) having a second part a 2,2 ) 8. The cathode current collector and connector assembly according to claim 7, wherein the cathode current collector and connector assembly is at least partially coated with the optional protective steel layer cladding, where a 1,2 ) and / or a 2,2 ) is at least partially free, preferably completely free, of the optional protective steel layer cladding.

9. The cathode current collector and connector assembly according to any one of the preceding claims, wherein a1) including a third part a different from the first part and the second part 1,3 ) and the third part a 1,3 ) is arranged outside the groove of the carbonaceous cathode and the recess of the optional steel conductor element, and wherein the third part is surrounded by a protective shell a2) includes a third part a different from the first part and the second part 2,3 ), the third part a 2,3 ) is arranged outside the groove of the carbonaceous cathode and the recess of the optional steel conductor element, and wherein the third part is surrounded by a protective shell preferably, the protective shell includes a material selected from SiC, ramming paste or refractory material.

10. A kit of parts for manufacturing the cathode current collector and connector assembly according to any one of the preceding claims, comprising a1) a first copper or copper alloy current collector system with an optional protective steel layer cladding, a2) a second copper or copper alloy current collector system with an optional protective steel layer cladding, b) at least one longitudinal carbonaceous cathode having at least one groove extending in the longitudinal direction of the carbonaceous cathode for receiving at least a portion of a1) and a2), optionally ： c1) A first conductor element, c2) A second conductor element, characterized in that a1), the sum of the resistivity of b1) and optionally included c1) is different from the sum of the resistivity of a2), b2) and optionally included c2).

11. An aluminum electrolysis cell comprising a cathode current collector and a connector assembly preferably according to any one of claims 1-9, and at least one supply busbar, wherein the cathode current collector and the connector assembly are electrically connected to the at least one supply busbar.

12. Use of an asymmetric resistivity distribution in a cathode current collector and connector assembly to compensate for unbalanced upstream and downstream current flows in an aluminum electrolysis cell.

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