JP6629433B2 - Cathode bottom for producing aluminum - Google Patents

Description

  The present invention relates to a cathode bottom, its production method and its use in an electrolytic cell for producing aluminum.

  Aluminum is commonly produced by molten salt electrolysis in an electrolytic cell. Electrolytic cells generally comprise a trough of foil steel or steel, the bottom of which is lined with insulation. In the above trough, up to 24 cathode blocks of carbon or graphite connected to the negative terminal of the power supply form another trough floor, the walls of which consist of side wall bricks of carbon, graphite or silicon carbide. A gap is formed between the two cathode blocks in each case. The arrangement of the cathode block and the gap that can be filled is commonly referred to as the cathode bottom. The gap between the cathode blocks is conventionally filled with a ramming mass of coal and / or graphite based on coal tar. This serves as a seal against the molten components and helps compensate for machine adaptation during start-up. A carbon block hanging from a support frame connected to the positive terminal of the power supply is commonly used as the anode.

In this type of electrolytic cell, a molten mixture of aluminum oxide (Al ₂ O ₃ ) and cryolite (Na ₃ AlF ₆ ), preferably about 2-5% aluminum oxide and about 85-80% cryolite And other additives are subject to molten salt electrolysis at a temperature of about 960 ° C. In this process, the dissolved aluminum oxide reacts with the solid carbon anode to form liquid aluminum and gaseous carbon dioxide. The molten mixture has a protective crust with many side walls of the electrolytic cell, while aluminum builds up on the floor of the electrolytic cell below the molten material due to the high density of aluminum compared to the density of the molten material, and oxygen in the air Protected against re-oxidation caused by The aluminum thus produced is removed from the electrolytic cell and further processed.

  During electrolysis, the cathode bottom behaves in a largely chemically inert manner, while the anode is exhausted. Thus, the anode is a consumable part that is replaced during operating hours, while the cathode bottom is designed for extended use over a long period of time. Nevertheless, current cathode bottoms are prone to wear. Mechanical wear of the cathode surface is caused by the aluminum layer moving across the cathode bottom. In addition, (electro) chemical corrosion of the cathode bottom is caused by the formation of aluminum carbide and the insertion of sodium. Generally, 100 to 300 electrolytic cells are connected in series to form an economical facility for producing aluminum, and such facilities are generally used for at least 4 to 10 years. As intended, failure and replacement of a cathode block in an electrolytic cell in such a facility can be expensive, requires expensive repair work, and significantly reduces the economic viability of the facility.

  A disadvantage of the above-described electrolytic cell with a ramming mass of carbon and / or graphite based on coal tar is that it produces a thin layer of coarse ramming mass for technical reasons such as mechanical stability or ramming procedures. There is a gap that allows aluminum and particles to be unable to do so, thus reducing cathode surface area and increasing cathode bottom wear.

  The most widely used anthracite ramming lumps have lower electrical and thermal conductivity, especially than graphitized cathode blocks. This reduces the available cathode surface area, results in higher energy consumption due to the higher overall resistance, and reduces the economic viability of the process. Furthermore, the consumption of the cathode bottom increases due to the higher specific load.

  Another problem is that the ramming mass often contains a binder based on coal tar containing polycyclic aromatic hydrocarbons. These are toxic and / or carcinogenic. During use, some of these or some of the pyrolysis products enter the atmosphere.

  In WO 2010/142580 A1, the ramming mass is replaced with a compressible graphite film, so that substances in the harmful ramming mass such as polycyclic aromatic hydrocarbons can be omitted and the cathode block at the cathode bottom A seal between them can be achieved.

  However, for example, by reusing the steel trough of the electrolytic cell such that additional cracks, cracks, or dislocations of the entire cathode block occur, the deformation behavior changes from ideal, so that a seal cannot be guaranteed . Such additional cracks, cracks, or dislocations are operational risks, as the deformation behavior is often difficult to predict. In this case, the aluminum or electrolytic melt can leak out, which can even cause immediate failure of the cell. For this reason, additional cracks and / or cracks must be compensated.

WO2010 / 142580A1

  The object of the present invention is therefore to provide a cathode bottom which can compensate for the deformation behavior of the electrolytic cell and thus guarantee a seal. In the context of the present invention, the cathode bottom is not only an arrangement of at least two cathode blocks leaving an optionally filled gap, but also at least one cathode block and at least one side wall brick leaving an optionally filled gap. Is also understood to mean the arrangement. A gap is the space between two cathode blocks or between a cathode block and a side wall brick.

  A cathode bottom for an electrolytic cell for producing aluminum comprising at least two cathode blocks and / or at least one cathode block and at least one side wall brick, arranged at a predetermined distance from each other, comprising at least one cathode The gap is filled with fillers which can be pre-arranged on the blocks or on the side wall bricks, said filler being a pre-compressed graphite plate composed of expanded graphite and graphite intercalation compound, characterized in that it has a cathode bottom. Is achieved.

  According to the invention, the cathode bottom comprises a filler arranged on at least one cathode block and / or side wall brick, characterized in that the filler comprises a pre-compressed plate based on expanded graphite and graphite intercalation compounds. . In the sense of the present invention, "pre-compressed" means that the plates based on expanded graphite and graphite intercalation compounds have been compressed, but can be further compressed. This means that the pre-compressed plate based on expanded graphite and graphite intercalation compound is partially compressed and therefore under pressure, and can be subjected to further pressure.

  According to the invention, a pre-compressed graphite plate based on expanded graphite and a graphite intercalation compound is also referred to as a pre-compressed graphite plate. These two terms are interchangeable in the sense of the present invention and refer to a pre-compressed graphite plate consisting of expanded graphite and a graphite intercalation compound.

  Expanded graphite has the following advantageous properties: non-hazardous to health, environmentally compatible, soft, compressible, lightweight, aging resistant, chemically and thermally resistant, Technically air-tight and liquid-tight, non-flammable and easily processable. In addition, expanded graphite does not form an alloy with liquid aluminum. Therefore, it is suitable as a filler for the cathode bottom for an electrolytic cell for producing aluminum.

To produce graphite having a worm-like structure, graphite, such as natural graphite, is usually mixed with an interlayer material, such as an inorganic acid, for example, nitric acid, sulfuric acid, or a mixture thereof, and thus graphite as an intermediate product. An intercalation compound is obtained, which is subsequently heat-treated at a high temperature, for example from 600 ° C. to 1200 ° C. (DE 100 39 927 A1). The acid insertion is typically performed in the presence of an oxidizing agent such as, for example, nitric acid (HNO ₃ ), hydrogen peroxide (H ₂ O ₂ ), potassium permanganate (KMnO ₄ ), or potassium chlorate (KClO ₃ ). Happens in.

  Expanded graphite is, for example, graphite expanded 80 times or more with respect to natural graphite in a plane perpendicular to the hexagonal carbon layer. Expanded graphite is characterized by excellent formability and good connectivity by expansion. Expanded graphite can be plate shaped and thermal conductivity up to 500 W / (mK) can be achieved.

  Thermal conductivity is determined using the Angstrom method ("Angstrom's method of measuring thermal conductivity", Amy L. Lytle, Wooster University, Faculty of Physics, dissertation).

  The intercalation material of the graphite intercalation compound may be an electron donor or an electron acceptor, preferably an electron acceptor. An "electron donor" is understood in the context of the present invention as being a compound or element having free electrons, for example lithium, potassium, rubidium or cesium. An “electron acceptor” is understood in the present invention to be a compound with an electron gap, ie an incomplete noble gas composition.

Iron (Fe), aluminum (Al), antimony (Sb), tin (Zn), yttrium (Y), chromium (Cr) or nickel (Ni) metal halides, preferably metal chlorides, and acids, preferably sulfuric acid ( H ₂ SO ₄ ), acetic acid (CH ₃ COOH), and nitric acid (HNO ₃ ), or mixtures of sulfuric / nitric and sulfuric / acetic acids may be selected as electron acceptors in the context of the present invention. Preferably, an aluminum halide, particularly preferably aluminum chloride, or sulfuric acid (H ₂ SO ₄ ) is used as the electron acceptor.

  By using a pre-compressed graphite plate as a filler, the cracks or cracks that occur during processing or during reuse of the steel trough can be closed by expanding the graphite intercalation compound, the expansion of which depends on the operating temperature . In this way, some kind of "self-healing" of cracks or cracks is possible.

  Defects or cracks that may be caused by equipment can also be repaired by salt swelling, and the potential between adjacent edges when using a pre-compressed graphite plate, smaller than the entire length of the cathode. Gaps are minimized.

  As a result, cracks or cracks, in particular, can also be closed in the inaccessible areas of the cathode. By closing additional cracks and / or cracks, sealing of the electrolytic cell is achieved.

  According to the present invention, various graphite intercalation compounds can be mixed together, which exhibit onset of expansion at different temperatures due to different intercalation materials. In this way, it is possible to cover the various temperature regions of the cell, for example, between the cathode blocks or between the cathode and the side wall brick, as desired.

  As a result, a customized filler can be provided.

  Advantageously, the proportion of expanded graphite in the pre-compressed graphite plate is 70-99.5 wt%, preferably 80-95 wt%, particularly preferably 90 wt%, and the proportion of graphite intercalation compound in the pre-compressed graphite plate is , 0.5 to 30 wt%, preferably 5 to 20 wt%, particularly preferably 10 wt%. The components, namely expanded graphite and graphite intercalation compound, always constitute 100 wt% together.

  If the proportion of the graphite intercalation compound in the pre-compressed graphite plate is less than 0.5 wt%, too few graphite intercalation compounds can be expanded later, so that too few cracks are closed and therefore the graphite intercalation compound is near the surface. May be in inappropriate locations due to the limited distribution of

  When the proportion of the graphite intercalation compound in the pre-compressed graphite plate exceeds 30 wt%, the stability of the pre-compressed graphite plate is achieved because the pre-compressed graphite plate achieves the stability by the connection of the already expanded graphite particles. Is too low.

  If the proportion of graphite intercalation compound in the pre-compressed graphite plate is between 0.5 and 30 wt%, the above self-healing of cracks and / or cracks is possible; that is, after the graphite intercalation compound at the operating temperature of the electrolytic cell. The expansion closes any remaining cracks or cracks. Fillers adapted to the temperature program of the electrolytic cell and thus customized can be provided by the choice of graphite intercalation compound.

  Another beneficial effect is the physiological harmlessness of the pre-compacted graphite plates as compared to conventional coal tar-containing carbon compositions containing polycyclic aromatic hydrocarbons that are harmful to health. In addition, the pre-compressed graphite plate has a higher electrical and thermal conductivity as compared to conventional coal tar-containing carbon compositions, thus also increasing the effective cathode surface area.

  The pre-compressed graphite plate used in accordance with the invention can be applied to the area of the electrolysis cell where conventional ramming masses are used, i.e., in particular to the gaps formed between the cathode blocks, but to the side walls of the electrolysis cell and the cathode block. Can also be inserted into the space between. The pre-compressed graphite plate is used in particular as a sealing means between the cathode blocks of the cathode bottom and between the cathode blocks and the side walls of the cathode bottom.

  The filler and the cathode block or the cathode block and the side walls are connected in a frictional manner, preferably ending in the same plane. The filler and cathode block or sidewall may optionally be adhesively bonded, for example, by a phenolic resin. In the present invention, the terms side wall and side wall brick are used similarly.

By using a pre-compressed graphite plate instead of the conventionally used coal tar containing ramming mass, the width of the gap between the cathode blocks can be reduced and the effective cathode surface area can be increased. This material is used as a filler between the two cathode blocks, not only can they seal the gap between the two cathode blocks, but also due to the compressible nature of the cathode blocks caused by the expansion of sodium that occurs during electrolysis And / or compensate for swelling of the side wall bricks. Sodium penetrates into the cathode block and / or side wall bricks by diffusing from the molten cryolite (Na ₃ AlF ₆ ).

  According to the invention, the pre-compressed graphite plate thus has a thickness of 2 to 35 mm, preferably 5 to 20 mm, particularly preferably 10 to 15 mm. A minimum thickness of 2 mm is required to be able to compensate for the sodium expansion of the cathode block and / or sidewalls.

According to the invention, the pre-compressed graphite plate has a thickness of 0.04 to 0.5 g / cm ³ , preferably 0.05 to 0.3 g / cm ³ , particularly preferably 0.07 to 0.1 g / cm ^3. Having a density of The density must be less than 0.5 g / cm ³ so that a 2 mm thick graphite plate is produced with a typical weight per unit area of 1000 g / m ³ . The graphite plate may be further compressed so that no gap is formed between the cathode blocks and / or the side walls.

  In another preferred embodiment, the filler is arranged such that the filler is coplanar on the two opposing surfaces of the cathode block adjacent to the surface forming the gap and on and in the gap. The fact that the fillers are coplanar means that, in the sense of the invention, the fillers are arranged on the cathode block such that the cathode bottom in each case has uniform dimensions along its length, height and width. Means that Within the cathode bottom in the electrolysis cell, there is a space between the side wall of the electrolysis cell and the cathode block. In this case, the filler is arranged such that it fills the gap between the cathode blocks and the area between the cathode blocks and the side walls. Thus, the cathode bottom forms the entire floor of the electrolysis cell, i.e. it extends to all the side walls of the electrolysis cell, and the cathode bottom is a region of relatively high thermal and electrical conductivity in the form of a cathode block. And a region having a relatively low thermal conductivity and electrical conductivity in the form of a filler material comprising expanded graphite and a graphite intercalation compound.

  The cathode block preferably has a length that is greater than the width dimension, while the width and height dimensions are approximately the same. Generally, the cathode block has a maximum length of 3800 mm, a width of 700 mm and a height of 500 mm. Preferably, the at least two cathode blocks are arranged such that their length dimensions are comparable. The predetermined distance between the two cathode blocks is usually about 30-60mm. By using the filler according to the present invention, the distance between the cathode blocks can be reduced. Thus, for example, when using cathode blocks with a width of 650 mm, the distance between the cathode blocks must be at least 40 mm when using a conventional ramming mass as a filler between the cathode blocks, while pre-compressed. If a graphite plate is used, the distance can be reduced to 10 mm.

  Thus, for example, if a 40 mm wide gap between 650 mm wide cathode blocks is reduced to 10 mm, the effective cathode block surface area increases by about 5%.

  Preferably, at least one cathode block comprises at least one connection to a power supply. For example, the cathode block comprises at least one recess for receiving a conductor rail that can be connected to a power supply. If at least two cathode blocks are placed such that their length dimensions are parallel, it is preferred that a recess is placed in the longitudinal direction of the cathode block, i.e. the recess is a gap formed between the two cathode blocks. And extend in parallel. Of course, the cathode bottom may further comprise a composite element between the cathode block and the conductor rail, for example a contact agent.

  The at least one cathode block is electrically and thermally conductive, is resistant to high temperatures, is chemically stable to the bath components of the electrolysis, and is designed such that it cannot alloy with aluminum. The cathode block is preferably made of graphite and / or amorphous carbon. Particularly preferably, the cathode block comprises graphite or graphitized carbon. Because they meet the requirements for thermal conductivity, electrical conductivity and chemical resistance to form the cathode bottom in an electrolytic cell for producing aluminum more than other materials.

  The cathode bottom in the preferred embodiment described above, comprising at least two cathode blocks and / or at least one cathode block and at least one side wall brick, comprises a filler having a region of high conductivity and comprising a pre-compressed graphite plate. In that having a generally lower conductivity than the cathode blocks and / or side wall bricks, but formed between the cathode blocks to prevent bath components from entering the relatively low area of the cathode bottom during electrolysis An area is provided that can seal the gap.

  The two components, the cathode block and the side wall brick, and the pre-compressed graphite plate thus perform various functions of the cathode bottom. Due to its multifunctional design, the cathode bottom can thus be sized for large-scale use. Due to the arrangement of the plurality of cathode blocks and / or cathode blocks and side wall blocks, a large conductive cathode surface is produced and by using pre-compressed graphite plates to effectively seal the gap between the cathode blocks In addition, wear and damage of the cathode surface between the cathode blocks are prevented.

The cathode block according to the invention may be produced according to a method comprising the following steps.
(A) providing at least one cathode block;
(B) disposing a filler on at least one surface of at least one cathode block, the filler comprising at least one pre-compressed plate based on expanded graphite and a graphite intercalation compound;
(C) at least one of the at least one cathode block at a predetermined distance from the at least one cathode block such that the filler fills a gap formed by placing another cathode block or sidewall brick at a predetermined distance from the at least one cathode block; Placing another cathode block or at least one side wall brick.

  By producing a cathode bottom with a pre-compressed graphite plate, a large effective cathode surface area can be achieved, whereby a plurality of cathode blocks can be arranged next to each other.

  The cathode block is produced such that a filler is connected to at least one cathode block in an embodiment connected by the filler disposed on the cathode block, and an adhesive is additionally used if necessary.

  By arranging another cathode block or side wall brick on the cathode block, another connecting connection between the cathode blocks or between the cathode block and the side wall brick is firstly achieved by the pre-compressed graphite plate. Other cathode block or side wall brick placements are achieved by hydraulic or mechanical pressing, optionally with an adhesive, thus creating a frictional connection. By means of the method according to the invention, the width of the gap between the cathode blocks or between the cathode blocks and the side wall bricks can be reduced compared to conventional gap widths, thus increasing the effective cathode surface area. The pre-compressed graphite plate filling the gap is partially reversibly compressible, which can compensate for the bulging of the cathode block.

  After placement of another cathode block, a pre-compressed graphite plate is received in the gap, which is a slightly elastic filler that seals the gap without forming a cavity. Disposing the at least one other cathode block may be performed before or after disposing the filler on the at least one cathode block.

  The cathode blocks may be provided with a means to allow their connection to a power supply before or after they are installed. For example, the cathode block may be provided with at least one recess before or after installation, into which at least one conductor rail is inserted, which may be connected to a power supply. Further, the cathode block thus treated may be provided with other means, before or after installation, for example, a contact agent may be placed between the cathode block and the conductor rail.

  The cathode bottom according to the invention is used in an electrolytic cell for the production of aluminum. In a preferred embodiment, the electrolytic cell comprises a trough, generally comprising foil steel or steel, and has a round or square shape, preferably a rectangular shape. The side walls of the trough may be lined with carbon, carbide or silicon carbide. Preferably, at least the trough floor is lined with insulation. The cathode bottom is located on the floor of the trough or on insulation. At least two, preferably 10 to 24, cathode blocks are arranged at a predetermined distance from each other and parallel to one another in relation to their length dimensions, in each case at least one pre-compressed graphite plate. A gap is formed between each filled block. The space between the side wall and the cathode block is filled with a filler comprising a pre-compressed graphite plate or a conventional anthracite ramming mass. Similarly, the gap between the cathode blocks may be filled with a pre-compressed graphite plate or conventional anthracite ramming mass. Each gap in the cathode bottom may be filled differently. The cathode block is connected to the negative terminal of the power supply. At least one anode, such as a Söderberg electrode or a pre-fired electrode, hangs from the support frame connected to the positive terminal of the power supply and projects into the trough without touching the cathode bottom or the side walls of the trough. Preferably, the distance from the anode to the wall is greater than to the cathode bottom or the formed aluminum layer.

  To produce aluminum, the solution of aluminum oxide in the molten cryolite undergoes molten salt electrolysis at a temperature of about 960 ° C., and the side walls of the trough are covered with a solid crust of the molten mixture, while the aluminum is Aluminum accumulates under the molten material because it is denser than the molten material.

  Other features and advantages of the present invention will be described below with reference to the following drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic sectional view of a cathode bottom according to the present invention. FIG. 2 is a schematic cross-sectional view of a part of an electrolytic cell for producing aluminum having a cathode bottom according to the present invention. 3a to 3c schematically show a method sequence for producing a cathode bottom according to the invention. 4a to 4c schematically show another method sequence for producing a cathode bottom according to the invention.

  FIG. 1 is a schematic sectional view of a cathode bottom 1 according to the present invention. The cathode bottom 1 comprises a filler 3 consisting of a pre-compressed graphite plate filling a gap 5 formed between two cathode blocks 7. Cathode block 7 has sufficient electrical and thermal conductivity for use in molten salt electrolysis and is made, for example, of graphitized carbon. Each cathode block 7 is provided with a recess 9 for receiving a conductor rail (not shown) enabling connection of the cathode block to a power supply. Filler 3 and cathode block 7 end on the same plane.

  FIG. 2 is a schematic sectional view of a part of an electrolytic cell 213 for producing aluminum. The electrolysis cell 213 includes a trough 215 made of steel. The side wall 217 of the trough 215, one of which is shown in FIG. 2, is lined with the side wall brick 219 made of graphite, one of which is shown in FIG. The floor of the trough 215 is lined with the thermal insulation layer 221 so as to be completely covered thereby. The cathode bottom 21 is disposed on the heat insulating layer 221. The cathode bottom 21 comprises a filler 23 and a cathode block 27, two of which are shown in FIG. 2, which are arranged at a predetermined distance from each other. In a standard electrolytic cell, the filler 24 disposed between the side wall brick 219 and the cathode block 27 is a ramming mass made of carbon. The gap between the side wall brick 219 and the cathode block 27 is filled in this way. According to the present invention, filler 24 may be a pre-compressed graphite plate. Filler 23 also comprises a pre-compressed graphite plate. A gap 25 is formed between each cathode block 27. The filler 23 fills the gap 25, and the ramming mass 24 is formed between the cathode block 27 and the side wall 217 such that the heat insulating layer 221 is completely covered by the cathode bottom 21 including the ramming mass 24, the filler 23, and the cathode block 27. Fill the relevant space of. As shown in FIG. 2, the filler 23 ends on the same plane as the cathode block 27. Each cathode block 27 includes a recess 29 suitable for receiving a conductor rail (not shown) that can be connected to a negative terminal of a power supply (not shown). In addition, the electrolytic cell 213 includes an anode 223, two of which are shown in FIG. 2, each depending from a support 225 connected to the positive terminal of a power supply (not shown). A solution 227 of aluminum oxide in molten cryolite is located in electrolysis cell 213. During electrolysis, aluminum 229 accumulates between solution 227 and cathode bottom 21.

  3a to 3c schematically show a method sequence for producing a cathode bottom 31 according to the invention.

  FIG. 3a shows the provision of two cathode blocks 37, each having a recess 39 for receiving a conductor rail, and arranged at a predetermined distance from each other such that a gap 35 is formed. FIG. 3 b shows the filler 33 with a pre-compressed graphite plate inserted into the gap 35. FIG. 3c shows a cathode bottom 31 that can be used in an electrolytic cell for aluminum production. The filler 33 fills the gap 35. The quantity dimension of the filler 33 is chosen such that the filler 33 ends flush with the cathode block 37 and completely fills the gap 35. Note that for clarity, the possible connection of the cathode bottom 31 to the power supply and the connection means have been omitted from FIGS. 3a to 3c.

  4a to 4c schematically show another method sequence for producing a cathode bottom 41 according to the invention.

  FIG. 4a shows the provision of a cathode block 47 with a recess 49 for receiving a conductor rail (not shown). FIG. 4b shows a filler 43 comprising a pre-compressed graphite plate arranged in a plane on the surface of the cathode block 47, and optionally an adhesive is used to secure said filler. FIG. 4 c shows another cathode block 47 with a recess 49 arranged on the filler 43 so that another cathode block is frictionally connected to the cathode block 47 by the filler 43. FIG. 4c shows a cathode bottom 41 that can be used in an electrolytic cell for producing aluminum. By repeating the steps shown in FIGS. 4b and 4c, a cathode bottom with a plurality of cathode blocks arranged next to each other can be produced. Note that for clarity, the possible connection of the cathode bottom 41 to the power supply and the connection means have been omitted from FIGS. 4a to 4c.

  Hereinafter, the present invention will be described based on embodiments, but the embodiments do not limit the present invention.

[Embodiment 1]
It was added and 50g of sulfuric acid (95% to 98%) and _H 2 _O 2 (70%) of 1g to 20g of graphite. After an intercalation time of 20 minutes had elapsed, the reaction mixture was suction filtered, washed several times with distilled water (about 250 ml) and suction filtered again. The obtained graphite intercalation compound was dried at 120 ° C. to a constant weight. Thereafter, 90% by weight of the obtained graphite intercalation compound was expanded at about 1000 ° C. 10% by weight of the graphite intercalation compound was added to the expanded graphite thus obtained by continuously distributing the graphite intercalation compound on the layer of expanded graphite particles and then immediately compressed.

[Embodiment 2]
It was added and 50g of sulfuric acid (95% to 98%) and _H 2 _O 2 (70%) of 1g to 20g of graphite. After an intercalation time of 20 minutes had elapsed, the reaction mixture was suction filtered, washed several times with distilled water (about 250 ml) and suction filtered again. The obtained graphite intercalation compound was dried at 120 ° C. to a constant weight. Thereafter, 90% by weight of the resulting graphite intercalation compound was expanded at about 1000 ° C. and directed through a ramp onto a conveyor belt. In the above-mentioned transfer inclined table, a graphite intercalation compound of 10% by weight was continuously supplied at a ratio of 1: 9. Then, compression was performed immediately.

Reference Signs List 1 cathode bottom 3 filler 5 gap 7 cathode block 9 recess 21 cathode bottom 23 filler 24 ramming mass 25 gap 27 cathode block 29 recess 31 cathode bottom 33 filler 35 gap 37 cathode block 39 recess 41 cathode bottom 43 filler 47 cathode block 49 recess 213 Electrolysis cell 215 Trough 217 Side wall 219 Side wall brick 221 Insulation layer 223 Anode 225 Support 227 Aluminum oxide solution 229 Aluminum

Claims (10)

A cathode bottom for an electrolytic cell for producing aluminum comprising at least two cathode blocks and / or at least one cathode block and at least one side wall brick, arranged at a predetermined distance from each other, comprising at least one cathode on or in at least one side wall on the bricks is filled with a gap in the pre-arranged filler, the gap is defined as the space between the cathode blocks or between the cathode block and the side wall brick, wherein the filler is expanded graphite And a pre-compressed graphite plate comprising a graphite intercalation compound.   The cathode bottom according to claim 1, wherein the proportion of expanded graphite in the pre-compressed graphite plate is 70 to 99.5% by weight.   The cathode bottom according to claim 1, wherein the ratio of the graphite intercalation compound in the pre-compressed graphite plate is 0.5 to 30% by weight. The intercalation material of the graphite intercalation compound is an acid selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), acetic acid (CH ₃ COOH), or nitric acid (HNO ₃ ), or a mixture of sulfuric acid / nitric acid and sulfuric acid / acetic acid. 4. The cathode bottom according to claim 3, wherein the cathode bottom is in the form of an electron acceptor.   The cathode bottom according to claim 1, wherein the pre-compressed graphite plate has a thickness of 2 to 35 mm. The cathode bottom according to claim 1, wherein the pre-compressed graphite plate has a density of 0.04 to 0.5 g / cm ³ . 3. The cathode bottom according to claim 1, wherein the at least two cathode blocks and / or the at least one cathode block and at least one side wall brick and the filler end in the same plane . 4. (A) providing at least one cathode block;
(B) disposing a filler on at least one surface of the at least one cathode block, the filler comprising at least one pre-compressed plate based on expanded graphite and a graphite intercalation compound;
(C) at a predetermined distance from the at least one cathode block such that the filler fills a gap formed by placing another cathode block or sidewall brick at a predetermined distance from the at least one cathode block. Placing at least one other cathode block or at least one side wall brick;
A method for producing a cathode bottom according to any one of the preceding claims, comprising: 9. The arrangement of claim 8, wherein the placement of the filler on the at least one surface of the at least one cathode block is achieved by securing the filler to the at least one surface with an adhesive. the method of.   Use of the cathode bottom according to any one of claims 1 to 7 in an electrolytic cell for producing aluminum.

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