Full-graphitization asymmetric cathode structure of aluminum electrolysis cell

Abstract

The invention discloses an aluminum electrolysis cell full-graphitization asymmetric cathode structure which comprises a first calcium silicate board arranged at the bottom in an electrolysis cell shell, a first nanometer heat insulation board is arranged on the first calcium silicate board, and two layers of first light heat insulation bricks with the thickness of 65 mm are arranged on the first nanometer heat insulation board. A layer of dry type anti-seepage material with the thickness of 186 mm is arranged on the first light heat preservation bricks, two layers of first vermiculite anti-seepage heat insulation bricks with the thickness of 65 mm are arranged in the long side of the electrolytic cell shell, and three layers of second vermiculite anti-seepage heat insulation bricks with the thickness of 65 mm are arranged in the short side of the electrolytic cell shell; the asymmetric heat preservation design is adopted, a multi-layer and high-performance composite heat preservation system is formed, natural heat dissipation differences caused by physical positions and magnetic field effects are compensated through differential heat preservation, an electrolytic bath is guided to form ideal furnace wall shapes with uniform thicknesses on the four side walls, and therefore the problem that heat dissipation of corners is large is solved, and the service life of the electrolytic bath is prolonged. And the service life of the electrolytic bath is prolonged.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis cell technology, specifically to a fully graphitized asymmetric cathode structure for an aluminum electrolysis cell. Background Technology

[0002] Existing traditional 400kA aluminum electrolytic cells generally adopt an inner cathode structure consisting of 50% graphite cathode carbon blocks, ordinary cathode steel rods, ceramic fiber boards, and anti-seepage materials. In actual long-term operation, this structure has gradually revealed several inherent defects, which have restricted the energy efficiency, stability, and lifespan of the electrolytic cell.

[0003] First, the resistivity of the 50% graphite cathode carbon block is relatively high (approximately 27 μΩ·m at 20℃ and approximately 16 μΩ·m at 1000℃), resulting in a generally high voltage drop at the furnace bottom (approximately 210 mV), directly increasing the DC power consumption per ton of aluminum. Simultaneously, its poor thermal conductivity (approximately 22 W / (m·K) at 20℃) hinders timely heat dissipation from the sides, easily causing uneven heat dissipation at the corners and affecting the stability of the furnace wall shape.

[0004] Secondly, this material has weak resistance to sodium corrosion. It has a high sodium absorption capacity and a high sodium expansion rate (up to approximately 0.8%), making it prone to volume expansion during electrolysis due to sodium penetration. This can lead to carbon block bulging, electrolyte leakage, and even premature cathode damage. Further sodium penetration can also react with the cryolite at the carbon-steel contact surface, increasing contact resistance and exacerbating the voltage drop.

[0005] Furthermore, the components of traditional linings are not adequately matched in terms of thermal, electrical, and corrosion resistance, making it difficult for the overall structure to maintain a stable physical and electrochemical state under long-term high-temperature and highly corrosive environments. These problems collectively lead to higher operating voltages, limited current efficiency, and increased maintenance costs in electrolytic cells, thus hindering further improvements in the technical and economic indicators of aluminum electrolysis production. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the existing defects and provide a fully graphitized asymmetric cathode structure for aluminum electrolysis cells. It adopts an asymmetric insulation design to form a multi-layered, high-performance composite insulation system. Through differentiated insulation, it compensates for the natural heat dissipation differences caused by physical location and magnetic field effects, and guides the electrolysis cell to form a uniform and ideal furnace side shape on the four side walls, thereby solving the problem of large heat dissipation at the corners and extending the service life of the electrolysis cell. This can effectively solve the problems in the background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a fully graphitized asymmetric cathode structure for an aluminum electrolytic cell, comprising a first calcium silicate plate disposed at the bottom of the electrolytic cell shell, a first nano-insulation plate disposed on the first calcium silicate plate, two layers of 65mm thick first lightweight insulating bricks disposed on the first nano-insulation plate, a 186mm thick dry impermeable material disposed on the first lightweight insulating bricks, two layers of 65mm thick first vermiculite impermeable heat-insulating bricks disposed on the long side of the electrolytic cell shell, three layers of 65mm thick second vermiculite impermeable heat-insulating bricks disposed on the short side of the electrolytic cell shell, uniformly distributed fully graphitized cathode carbon blocks disposed on the dry impermeable material, and high-strength castable refractory surrounding the fully graphitized cathode carbon blocks. The outer side of the high-strength castable on the short side of the electrolytic cell shell consists of two 60mm thick second calcium silicate boards, and the outer side of the second calcium silicate boards consists of a 20mm thick second nano-insulation board. The outer side of the high-strength castable on the long side of the electrolytic cell shell consists of a 65mm thick second lightweight insulating brick, the outer side of the second lightweight insulating brick consists of a 60mm thick third calcium silicate board, and the outer side of the third calcium silicate board consists of a 20mm thick ceramic fiber board. A 65mm thick high-alumina refractory brick is provided on the upper side of the high-strength castable, and a 90mm thick side carbon block is provided on the upper layer of the high-alumina refractory brick. Adjacent fully graphitized cathode carbon blocks are firmly bonded together with carbon interlayer paste, and the fully graphitized cathode carbon blocks and the side carbon blocks are fixed together with carbon interlayer paste to form a slope shape, creating artificial extension legs.

[0008] As a preferred embodiment of the present invention, the first calcium silicate board is a convex structure with a thickness of 70 mm in the middle and 40 mm on both sides, and the first nano-insulation board is a concave structure with a thickness of 20 mm in the middle and 50 mm on both sides, so that the first calcium silicate board and the first nano-insulation board can be fitted together.

[0009] As a preferred embodiment of the present invention, the fully graphitized cathode carbon block is provided with a 125*180mm cathode steel rod inside, and the fully graphitized cathode carbon block and the cathode steel rod are connected by casting with phosphorus pig iron.

[0010] As a preferred embodiment of the present invention, a third nanometer heat insulation plate is provided on the bottom inclined surface of the electrolytic cell shell.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. The fully graphitized asymmetric cathode structure of the aluminum electrolytic cell in this invention reduces sodium corrosion to a certain extent. At the same time, the cathode steel rod is a large steel rod of 130*180mm, which increases the cross-sectional area and reduces the resistance.

[0012] 2. The aluminum electrolytic cell of the present invention features a fully graphitized asymmetric cathode structure. It adopts an asymmetric insulation design and compensates for the natural heat dissipation differences caused by physical location and magnetic field effects through differentiated insulation. This guides the electrolytic cell to form a uniform and ideal furnace side shape on the four side walls, balances heat dissipation at the corners, and solves the problem of long corner extensions during production.

[0013] 3. The aluminum electrolytic cell of the present invention features a fully graphitized asymmetric cathode structure, which can maintain good electrical and thermal balance. The primary crystallization temperature line is located below the cathode carbon block and inside the anti-seepage material; the 800-degree isotherm is maintained above the insulation brick; and the internal isotherms are reasonably distributed, which not only ensures the stable production of the electrolytic cell, but also solves the problem of large heat dissipation at the corners, and to a certain extent suppresses the extension of the corner legs, thus extending the service life of the electrolytic cell.

[0014] 4. The aluminum electrolytic cell of the present invention features a fully graphitized asymmetric cathode structure. It adopts an asymmetric insulation design to form a multi-layered, high-performance composite insulation system. Through differentiated insulation, it compensates for the natural heat dissipation differences caused by physical location and magnetic field effects, and guides the electrolytic cell to form a uniform and ideal furnace side shape on the four side walls, thereby solving the problem of large heat dissipation at the corners. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a partial structural diagram of the present invention; Figure 3 This is a side view of the structure of the present invention.

[0016] In the figure: 1 First calcium silicate board, 2 First nano-insulation board, 3 First lightweight insulation brick, 4 Dry seepage prevention material, 5 First vermiculite seepage prevention and insulation brick, 6 Second vermiculite seepage prevention and insulation brick, 7 Fully graphitized cathode carbon block, 8 High-strength castable, 9 Second calcium silicate board, 10 Second nano-insulation board, 11 Second lightweight insulation brick, 12 Third calcium silicate board, 13 Ceramic fiber board, 14 High alumina refractory brick, 15 Side carbon block, 16 Artificial extension leg, 17 Third nano-insulation board. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1-3This invention provides a technical solution: a fully graphitized asymmetric cathode structure for an aluminum electrolytic cell, comprising a first calcium silicate plate 1 disposed at the bottom of the electrolytic cell shell, a first nano-insulation plate 2 disposed on the first calcium silicate plate 1, two layers of 65mm thick first lightweight insulating bricks 3 disposed on the first nano-insulation plate 2, a layer of 186mm thick dry anti-seepage material 4 disposed on the first lightweight insulating bricks 3, two layers of 65mm thick first vermiculite anti-seepage and heat-insulating bricks 5 disposed on the long side of the electrolytic cell shell, three layers of 65mm thick second vermiculite anti-seepage and heat-insulating bricks 6 disposed on the short side of the electrolytic cell shell, uniformly distributed fully graphitized cathode carbon blocks 7 disposed on the dry anti-seepage material 4, high-strength castable refractory 8 surrounding the fully graphitized cathode carbon blocks 7, two layers of 60mm thick second calcium silicate plates 9 disposed on the outer side of the high-strength castable refractory 8 on the short side of the electrolytic cell shell, and a 20mm thick second nano-insulation plate 10 disposed on the outer side of the second calcium silicate plates 9. The outer side of the high-strength castable 8 on the long side of the electrolytic cell is covered with a 65mm thick second lightweight insulating brick 11. The outer side of the second lightweight insulating brick 11 is covered with a 60mm thick third calcium silicate board 12. The outer side of the third calcium silicate board 12 is covered with a 20mm thick ceramic fiber board 13. The upper side of the high-strength castable 8 is covered with a 65mm thick high-alumina refractory brick 14. The upper layer of the high-alumina refractory brick 14 is covered with a 90mm thick side carbon block 15. The adjacent fully graphitized cathode carbon blocks 7 are firmly bonded together with carbon interlayer paste. The fully graphitized cathode carbon blocks 7 and the side carbon blocks 15 are also bonded together with carbon interlayer paste to form a slope, creating artificial extension legs 16. This asymmetrical insulation design constitutes a multi-layer, high-performance composite insulation system. Through differentiated insulation, the natural heat dissipation differences caused by physical location and magnetic field effects are compensated, guiding the electrolytic cell to form a uniform and ideal furnace side shape on the four side walls, solving the problem of large heat dissipation at the corners.

[0019] Furthermore, the first calcium silicate board 1 has a convex structure with a thickness of 70mm in the middle and 40mm on both sides, and the first nano-insulation board 2 has a concave structure with a thickness of 20mm in the middle and 50mm on both sides, so that the first calcium silicate board 1 and the first nano-insulation board 2 can be fitted together; the first nano-insulation board 2 at the long side corner is higher than the middle position. The nano-insulation board is a top-level high-efficiency insulation material that can greatly reduce heat loss.

[0020] Furthermore, the fully graphitized cathode carbon block 7 has a 125*180mm cathode steel rod inside, and the fully graphitized cathode carbon block 7 and the cathode steel rod are connected by casting with phosphorus pig iron. The use of phosphorus pig iron to connect the cathode steel rod and the graphitized cathode carbon block further reduces the contact pressure drop and reduces the pressure drop at the bottom of the furnace.

[0021] Furthermore, a third nanometer heat insulation plate 17 is provided on the bottom inclined surface of the electrolytic cell shell.

[0022] During production, the electrolytic cell using fully graphitized cathode carbon blocks can maintain a stable bottom voltage drop of approximately 165mV, which is about 45mV lower than the approximately 210mV of the 50% graphite cathode electrolytic cell; the set voltage is maintained between 3.85-3.87V; the process parameters of the fully graphitized cathode cell are also more stable: the aluminum level is maintained at 23-25cm, the insulation material thickness is 12-14cm, the electrolyte level is controlled at 18-20cm, the electrolyte temperature is maintained at 940-950℃, the superheat is 5-15℃, and the molecular ratio is maintained within the range of 2.35-2.45.

[0023] 1. Low resistivity: The resistivity of fully graphitized carbon blocks is significantly lower than that of 50% graphitic carbon blocks: at 20℃, the resistivity of fully graphitized material is 10.5 μΩ·m, while that of 50% graphitic material is 27 μΩ·m; at 1000℃, the resistivity of fully graphitized material drops to 9.6 μΩ·m, while that of 50% graphitic material drops to 16 μΩ·m; since the resistivity decreases significantly with the increase of graphitization degree, the use of highly graphitized materials can reduce the cathode voltage drop by about 40-60mV, thereby effectively reducing power consumption.

[0024] 2. Thermal conductivity: The thermal conductivity of fully graphitized carbon blocks at 20℃ can reach 115W / (m·K), which is about 5.2 times that of 50% graphite carbon blocks (22W / (m·K). This excellent thermal conductivity helps to enhance heat dissipation on the side of the electrolytic cell, promotes the formation of a stable furnace side, thereby reducing horizontal current and aluminum liquid fluctuations, and ultimately improving current efficiency by about 1–2%.

[0025] 3. Thermal expansion: The average thermal expansion rate of fully graphitized carbon blocks is significantly lower than that of 50% graphite. The lower thermal expansion rate reduces the risk of deformation and breakage caused by temperature fluctuations, which helps to extend the life of the tank.

[0026] 4. Sodium Erosion Resistance: The sodium absorption of fully graphitized cathode carbon blocks is only about 1 / 3 that of 50% graphite carbon blocks, and its sodium expansion rate can be reduced from 0.8% to 0.4%. Reduced sodium erosion helps prevent electrolyte leakage and carbon block bulging, thus lowering the risk of early breakage. Fully graphitized carbon blocks have a denser volumetric structure and lower ash content, significantly enhancing sodium resistance; therefore, their sodium expansion rate is much lower than that of 50% graphite carbon blocks. During electrolysis, the rate and total amount of sodium penetration into the carbon block are greatly reduced. Even if a small amount of sodium enters the carbon block and diffuses to the carbon-steel contact interface, reacting with cryolite to form aluminum and sodium fluoride, the increase in resistance caused by this reaction layer is relatively limited. Furthermore, due to the stable structure of the carbon block itself, the upward bulging is less pronounced when constrained by the lining and tank shell. Therefore, using fully graphitized cathode carbon blocks not only effectively controls the physical deformation caused by sodium expansion but also maintains a lower furnace bottom pressure drop, and the pressure drop changes more gradually with increasing production time, which is beneficial for the long-term stable operation of the electrolytic cell.

[0027] This invention uses a cathode steel rod with a cross-sectional dimension of 125x180mm, which increases the cross-sectional area by 38.9% compared to the previous method. The resistance value is reduced to 69.4% of the original value. After the steel rod resistance is reduced, the total voltage drop of the cathode circuit is reduced. Theoretically, increasing the cross-sectional area of ​​the steel rod by 20% can reduce the cathode voltage drop by more than 24mV, saving more than 60kWh of electricity per ton of aluminum. With the modified steel rod cross-sectional area increased by 38.9%, the expected voltage drop reduction is even greater, and the energy-saving effect is more significant.

[0028] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fully graphitized asymmetric cathode structure for an aluminum electrolytic cell, comprising a first calcium silicate plate (1) disposed at the bottom of the cell shell, characterized in that: A first nano-insulation board (2) is provided on the first calcium silicate board (1). Two layers of 65mm thick first lightweight insulation bricks (3) are provided on the first nano-insulation board (2). A layer of 186mm thick dry seepage-proof material (4) is provided on the first lightweight insulation bricks (3). Two layers of 65mm thick first vermiculite seepage-proof and heat-insulating bricks (5) are provided inside the long side of the electrolytic cell shell. Three layers of 65mm thick second vermiculite seepage-proof and heat-insulating bricks (6) are provided inside the short side of the electrolytic cell shell. A uniformly distributed fully graphitized cathode carbon block (7) is provided on the dry seepage-proof material (4). The fully graphitized cathode carbon block (7) is surrounded by high-strength castable (8). Two layers of 60mm thick second calcium silicate board (9) are provided outside the high-strength castable (8) on the short side of the electrolytic cell shell. The outer side of the calcium plate (9) is a 20mm thick second nano-insulation plate (10). The outer side of the high-strength castable (8) on the long side of the electrolytic cell shell is a 65mm thick second lightweight insulation brick (11). The outer side of the second lightweight insulation brick (11) is a 60mm thick third calcium silicate plate (12). The outer side of the third calcium silicate plate (12) is a 20mm thick ceramic fiber plate (13). The upper side of the high-strength castable (8) is provided with a 65mm thick high-alumina refractory brick (14). The upper layer of the high-alumina refractory brick (14) is provided with a 90mm thick side carbon block (15). The adjacent fully graphitized cathode carbon blocks (7) are firmly fixed with carbon inter-paste, and the fully graphitized cathode carbon blocks (7) and the side carbon blocks (15) are fixed together with carbon inter-paste to form a slope, forming an artificial leg (16).

2. The fully graphitized asymmetric cathode structure for aluminum electrolysis cells according to claim 1, characterized in that: The first calcium silicate board (1) is a convex structure with a thickness of 70 mm in the middle and 40 mm on both sides, and the first nano-insulation board (2) is a concave structure with a thickness of 20 mm in the middle and 50 mm on both sides, so that the first calcium silicate board (1) and the first nano-insulation board (2) can be fitted together.

3. The fully graphitized asymmetric cathode structure for aluminum electrolysis cells according to claim 1, characterized in that: The fully graphitized cathode carbon block (7) is equipped with a 125*180mm cathode steel rod inside, and the fully graphitized cathode carbon block (7) and the cathode steel rod are connected by casting with phosphorus pig iron.

4. The fully graphitized asymmetric cathode structure for aluminum electrolysis cells according to claim 1, characterized in that: The bottom slope of the inner shell of the electrolytic cell is provided with a third nano heat insulation plate (17).

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