Cathode carbon block structure for aluminum reduction cells

Abstract

A kind of cathode carbon block structure for aluminum electrolytic cell, mainly applied to the construction of aluminum electrolytic cell cathode conductive output device, the cathode carbon block is characterized in that, at the side of the two ends of cathode carbon block, left and right symmetrical circular closed cathode conductive output hole for arranging and installing circular cathode steel bar is constructed along the length direction of cathode carbon block;The inner diameter of its cathode conductive output hole and the outer diameter of circular cathode steel bar are correspondingly arranged, so that the inner wall surface of cathode carbon block cathode conductive output hole can form dense iron-carbon combined interface conductive connection with the outer surface of circular steel constructed cathode steel bar under electrolytic high temperature thermal working condition technical condition, using the characteristics that the thermal expansion coefficient of steel material of circular cathode steel is greater than that of carbon graphite carbon material.

Description

Technical fields:

[0001] A cathode carbon block structure for aluminum electrolysis cells is mainly used in the construction of cathode conductive output devices, i.e., cathode carbon block steel rod groups, for aluminum electrolysis cells. Background technology:

[0002] The existing cathode conductive output device for aluminum electrolysis cells is mainly composed of a combination of cathode carbon blocks and cathode steel rods. It has two main functions: first, to conduct the cathode current output from the aluminum liquid layer in the electrolytic molten pool to the cathode busbar outside the bottom of the aluminum electrolysis cell; and second, to carry the structure of the molten aluminum and electrolyte liquid molten pool.

[0003] The structural configuration of the cathode conductor output device in an aluminum electrolysis cell not only determines the output mode of the cathode current within the molten aluminum layer of the cathode pool, but also affects the distribution of the electric field, the distribution of the magnetofluid field, and the velocity of the magnetofluid field within the aluminum electrolysis cell. Therefore, the structural design of the cathode conductor output device is crucial.

[0004] As per the instruction manual Figure 1 and attached Figure 2 As shown, the existing cathode conductive device for aluminum electrolysis cells has the following structural features: At the bottom of the cathode carbon block, one or two bottom-opening concave steel rod slots are machined along the length of the cathode carbon block using planing and milling techniques. These slots are used to install rectangular cathode steel rods that serve as the metal conductive output bodies. During assembly, the cathode carbon block is inverted with the bottom concave slots facing upwards. Then, a rectangular cathode steel rod is placed into one of these bottom-opening concave steel rod slots. Finally, in the gap between the cathode carbon block and the cathode steel rod, a conductive transition layer is formed between the inner wall of the concave slot and the outer wall of the cathode steel rod by casting pig iron or reinforcing carbon paste. This creates a three-sided contact conductive transition layer, connecting the cathode steel rod and the cathode carbon block together to form a structural component of the aluminum electrolysis cell cathode conductive output device.

[0005] However, in the actual electrolytic aluminum production process, the cathode current of the aluminum liquid layer in the aluminum electrolytic cell is conducted through the least resistive conductive path. That is, after the aluminum liquid layer is deflected to the side of the electrolytic cell to form a horizontal current, it is then introduced and output through the side end of the cathode carbon block to the cathode steel rod constructed at the bottom of the cathode carbon block. Then, it is conducted through the aluminum-steel composite explosion welded sheet and the soft busbar to the cathode busbar for cathode conductive output.

[0006] One of the biggest drawbacks of existing cathode conductive devices is that they use a rectangular cathode steel rod with a uniform cross-section assembled in a recessed groove at the bottom of the cathode carbon block. Due to the limitations in the structure and processing of the rectangular cathode steel rod and the rectangular recessed groove at the bottom of the cathode carbon block, it is difficult to take advantage of the superior conductivity of metallic materials compared to graphite carbon materials. Instead, the device can be modified by changing the cross-sectional shape of the cathode metal conductor, i.e., the cathode steel rod, and adjusting the distribution of the output cathode current in the aluminum electrolysis cell cathode conductive device. This would allow for the optimization of the current distribution in the aluminum electrolysis cell cathode conductive device and the adjustment of the magnetic flux field of the molten aluminum.

[0007] Currently, with the improvement of production technology and public awareness in the aluminum electrolysis industry, the concept of using round cathode steel bars instead of rectangular cathode steel bars to construct rectangular cathode carbon blocks in aluminum electrolysis cells has begun to be accepted by the industry. However, the existing structure of round cathode steel bars configured with cathode carbon block steel bars has not solved the problem of excessive impact current generated by the conduction of cathode current to the side of the electrolysis cell, causing impact wear on the aluminum liquid magnetohydrodynamic fluid, the furnace side of the cathode carbon block, and the upper surface of the cathode carbon block's side end. Utility model content:

[0008] To optimize the structural and conductive properties of the cathode conductive device in an aluminum electrolytic cell, suppress and adjust the horizontal current within the cell, and optimize the distribution of cathode current and magnetocurrent field, this patent application discloses an innovative technical solution for the cathode carbon block structure of an aluminum electrolytic cell cathode conductive output device configured using circular cathode steel rods.

[0009] The cathode carbon block described herein is combined with a circular cathode steel rod to form a cathode carbon block and steel rod assembly structure that can adjust the horizontal current of the aluminum liquid layer in the cathode molten pool of an aluminum electrolysis cell. The structural technical features of the cathode carbon block are: symmetrical circular, bottom-closed cathode conductive output holes are constructed on the sides of both ends of the cathode carbon block along its length, from the outside inwards, for mounting the circular cathode steel rods; the inner diameter of these cathode conductive output holes corresponds to the outer diameter of the circular cathode steel rods, allowing the inner wall surface of the cathode conductive output holes to directly form a dense iron-carbon interface conductive connection with the outer surface of the circular cathode steel rod under the high-temperature thermal conditions of electrolysis, utilizing the fact that the thermal expansion coefficient of the circular cathode steel is greater than that of carbon graphite. The innovation of this technical method lies in eliminating the existing conductive transition layer between the cathode steel rod and the cathode carbon block in cathode carbon block and steel rod assemblies, namely the tamping paste or pig iron conductive transition layer.

[0010] According to the above technical solution, the structural features of its cathode carbon block are: cathode conductive output holes symmetrically arranged at the ends of the same cathode carbon block, on the same horizontal center line in the length direction of the cathode carbon block.

[0011] According to the above technical solution, the structural feature of its cathode carbon block is that multiple symmetrical cathode conductive output holes can be set at different height positions on the same cathode carbon block.

[0012] According to the above technical solution, the structural features of its cathode carbon block are: in order to increase the iron-carbon contact area between the cathode carbon block and the cathode steel rod, and improve its conductivity and mechanical strength, the circular cathode conductive output holes set on the same cathode carbon block can be configured with different diameters.

[0013] According to the above technical solution, the structural features of its cathode carbon block are: in order to adjust the horizontal current in the electrolytic melting pool of the aluminum electrolysis cell, the same cathode conductive output hole set on the same cathode carbon block can be segmented with different diameters; that is, the same cathode conductive output hole can adopt a design with equal diameter or a variable diameter design with non-equal diameter.

[0014] According to the above technical solution, the structural features of its cathode carbon block are: the same cathode conductive output hole can be divided into two sections, one section can be divided into sections with different diameters, one section adopts a smooth rod design, and the other section adopts a threaded rod design. In order to adjust the horizontal current in the electrolytic melting pool of the aluminum electrolysis cell, the same cathode conductive output hole set on the cathode carbon block can be divided into two sections, one section can be divided into sections with different diameters, one section adopts a smooth rod design, and the other section adopts a threaded rod design.

[0015] Based on the above technical solution, the structural features of its cathode carbon block are as follows: To reduce the manufacturing cost of the cathode conductive output device, the structural design of the cathode carbon block is optimized to increase its conductivity. Two cathode conductive output holes are symmetrically expanded on the same center line on two side sections of the cathode carbon block, with a certain horizontal distance between them at the center of the cathode carbon block. That is, the two symmetrical cathode conductive output holes set on the same center line are non-through design.

[0016] Based on the above technical solution: In order to increase the iron-carbon contact area between the cathode carbon block and the cathode steel rod, and improve their conductivity and mechanical strength, multiple symmetrical cathode conductive output holes can be set at different heights on the same cathode carbon block.

[0017] According to the above technical solution, the structural features of its cathode carbon block are: in order to adjust the distribution of the cathode horizontal current in the aluminum electrolysis cell and reduce the impact and wear of the aluminum liquid magnetic flow field on the side wall of the cathode furnace, the upper part of its cathode carbon block can be designed as a trapezoidal sloping structure with a low middle and high sides.

[0018] By reading the above technical solutions, it can be seen that the cathode carbon block using a circular cathode steel rod described in this invention has the following significant technical advantages compared to the existing cathode carbon block using a rectangular cathode steel rod:

[0019] By reading the above technical solution, it can be seen that the innovative cathode carbon block, when assembling the circular cathode steel rod, adopts a side-mounted horizontal insertion method, connecting the circular cathode steel rod to the cathode conductive output hole on the cathode carbon block. The connection between the two is a direct iron-carbon interface conductive connection. This eliminates the need for a carbon tamping connection transition layer or a cast phosphorus pig iron conductive transition layer between the rectangular cathode steel rod and the concave steel rod groove. This not only reduces the construction cost of the cathode conductive output device and the waste of material resources, but also reduces the resistance and voltage drop of the connection transition layer between the cathode steel rod and the cathode carbon block.

[0020] By reading the above technical solutions, it can be seen that the innovative cathode carbon block not only provides technical and material support for the use of circular cathode steel rods, but also optimizes the mechanical structural design of the cathode carbon block, improving the overall structural stability of the cathode conductive output device of the aluminum electrolysis cell, i.e., the cathode carbon block steel rod assembly.

[0021] By reading the above technical solution, it can be seen that one of the basic principles of the cathode carbon block of the present invention is to use a circular cathode steel rod for configuration. This is because the thermal expansion coefficient of the circular cathode steel rod is greater than that of graphite carbon material, so that the metal surface of the circular cathode steel rod after radial expansion can achieve a tight fit with the inner wall surface of the cathode conductive output hole on the cathode carbon block to achieve a conductive connection between the iron and carbon interface. Since the cross-section of the circular cathode steel rod is circular, its radial expansion deformation stress can be controlled. Therefore, the resistance value and voltage drop between the iron and carbon junction interface can be precisely designed and adjusted to achieve the purpose of optimizing the overall conductive performance of the cathode conductive output device.

[0022] The design incorporates a concave steel rod groove with an opening at the bottom of the cathode carbon block, extending horizontally along the length of the cathode carbon block on both sides, and a circumferentially closed cathode conductive output hole. This design not only improves the mechanical strength of the cathode carbon block in the horizontal direction but also prevents corner fractures on the sidewalls of the concave groove at the bottom of the cathode carbon block, enhancing the stability of the bottom structure of the cathode conductive output device and extending its service life.

[0023] By changing the original through-type, bottom-opening concave steel rod groove, which was originally located at the bottom of the cathode carbon block and ran horizontally along the length of the cathode carbon block, to a design where the groove is located at the cathode conductive output hole, and the left and right ends of the cathode carbon block are not interconnected along the horizontal length of the cathode carbon block, resulting in a solid structure design with no through holes in the middle section of the cathode carbon block, new technical support is provided for the structural innovation of the cathode carbon block in aluminum electrolysis cells.

[0024] By reading the above technical solution, it can be seen that the innovative cathode conductive output device adopts a corresponding configuration of the cathode conductive output holes of the circular cathode steel rod and the cathode carbon block. It can adjust the horizontal current distribution of the aluminum electrolysis cell and optimize the conductivity of the aluminum electrolysis cell by segmenting the diameter of the cathode steel rod and adjusting the cross-sectional ratio of the cathode carbon block and the cathode steel rod on the same center line. Attached image description:

[0025] The technical solution and features of the novel cathode carbon block structure described in this invention will become clearer by reading the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a schematic diagram illustrating the structural configuration of a cathode carbon block and a rectangular cathode steel rod with a concave steel rod groove with an opening at the bottom, as described in the prior art.

[0027] Figure 2 for Figure 1 The side view cross section.

[0028] Figure 3 This is a schematic diagram of the structure of the cathode carbon block in this embodiment, which is configured using a circular cathode steel rod.

[0029] Figure 4 for Figure 3 The side view cross section.

[0030] Figure 5 This is a schematic diagram of the structure of Example 2, in which three cathode conductive output holes are provided on the side of the cathode carbon block.

[0031] Figure 6 for Figure 5 The side view cross section.

[0032] Figure 7 This is a schematic diagram of the structure of Example 3, which features a variable-diameter cathode conductive output hole on the side of the cathode carbon block.

[0033] Figure 8 for Figure 7 Side view cross section

[0034] Figure 9 This is a schematic diagram of the cathode carbon block structure in Example 4, where the upper part of the cathode carbon block is inclined trapezoidal and has a circular cathode conductive output hole.

[0035] Figure 10 for Figure 9 Side view cross section

[0036] The diagram shows: 1. Cathode carbon block; 2. Cathode conductive output hole; 2-1. Large-diameter cathode conductive output hole; 2-2. Small-diameter cathode conductive output hole; 2-3. Threaded cathode conductive output; 3. Circular cathode steel rod; 4. Rectangular bottom-opening concave steel rod groove; 5. Rectangular cathode steel rod; 6. Tamping paste or phosphorus pig iron conductive transition connection layer; 7. Crack; 8. Upper inclined surface of cathode carbon block. Detailed implementation method:

[0037] The technical features of the cathode carbon block structure shown in this invention will be made clearer through the following embodiments.

[0038] Example 1: As Figure 3 and Figure 4 The novel cathode carbon block 1 described in this invention is characterized by having two symmetrical cathode conductive output holes 2 at the left and right ends of the cathode carbon block 1, on the same horizontal line. These holes are used to mount two circular cathode steel rods. The top ends of the two cathode conductive output holes are spaced apart by a certain width S at the center of the cathode carbon block 1. That is, the two cathode conductive output holes 2 on the same horizontal center line are not interconnected. Alternatively, like the existing anode carbon block with rectangular cathode steel rods, the circular cathode conductive output holes could be made interconnected on both sides, but this would be a less desirable design. Implementing such a design would still fall within the scope of this patent application.

[0039] like Figure 3 , Figure 4 As shown in Embodiment 1, the cathode carbon block is characterized in that the inner diameter of the cathode conductive output hole 2 of the cathode carbon block 1 corresponds to the diameter of the circular cathode steel rod 3 installed in the hole. This ensures that the iron-carbon interface between the circular cathode steel rod 3 and the cathode conductive output hole 2 of the cathode carbon block forms a tight, conductive connection under electrolytic thermal conditions. Specifically, when designing the diameter of the cathode steel rod 3, the linear expansion coefficient of the circular cathode steel rod 3's metallic material should be considered, as it is greater than that of the graphite material in the cathode carbon block 1. When designing the assembly gap, the stress change in the thermal expansion coefficient of the cathode steel rod 3 within a temperature range of approximately 850°C should be fully considered, as this affects the compressive stress generated on the inner wall of the cathode conductive output hole 2 of the cathode carbon block 1. This achieves a tight, conductive connection between the cathode steel rod 3 and the cathode carbon block 2's iron-carbon interface while ensuring that the radial thermal expansion stress of the cathode steel rod 3 does not cause mechanical structural damage to the cathode carbon block 1. This optimizes the conductivity and mechanical stability of the cathode conductor.

[0040] Example 2: As Figure 5 , Figure 6As shown, the cathode carbon block in this embodiment has three cathode conductive output holes of unequal diameters on one end. Analysis reveals that multiple cathode conductive output holes 2 of different diameters are provided on the same cathode carbon block 1, and multiple circular cathode steel rods of different diameters are configured on the same cathode carbon block. Under the technical condition that the overall aggregate area of ​​the several circular cathode steel rods remains unchanged, by reducing the diameter of the circular cathode steel rods, the number of circular cathode steel rods can be increased, thereby increasing the overall conductive iron-carbon contact area between the cathode steel rods and the cathode carbon block, thus improving and optimizing the overall mechanical structure of the cathode conductive output device. This enhances the structural stability of the cathode conductive output device.

[0041] Example 3: As Figure 7 , Figure 8 As shown, the cathode carbon block described in this embodiment is basically the same as that in Embodiment 1. The key difference is that the cathode conductive output hole 2 of the cathode carbon block 1 is constructed in two sections with different diameters. This design allows for the use of cathode steel rods of different diameters and conductive properties within the same cathode conductive output hole. For example, a copper steel rod can be used at the left conductive input end 2-2, while a common low-carbon steel rod can be used at the left conductive output end 2-1. The copper section has a relatively smaller diameter, while the low-carbon steel section at the cathode conductive output hole 2 has a relatively larger diameter. Alternatively, a threaded rod can be used at the right conductive input end 2-3, while a common low-carbon steel rod can be used at the right conductive output end 2-1. In other words, the same cathode conductive output hole can be designed in two sections: one with a smooth rod design and the other with a threaded rod design.

[0042] Example 4 Figure 10 One characteristic of the cathode carbon block described in this invention is that the bottom of the central position of the cathode carbon block eliminates the concave groove design with an opening in the prior art. The existence of the through-type concave steel rod groove at the bottom of the carbon block is determined by its planing process. The cathode conductive output hole 2, constructed using a drilling method, is actually a blind hole, thus eliminating the need for drilling the middle part of the cathode and preserving its solid portion. This not only reduces its processing and construction costs but also allows for further optimization of the cathode carbon block's structural shape. For example, to adjust the current distribution of the molten aluminum in the aluminum electrolysis cell and prevent the horizontal current from scouring the side walls of the aluminum electrolysis cell, the upper shape of the cathode carbon block can be constructed as a trapezoidal structure that is high on both sides and low in the middle, sloping from both sides towards the middle. That is, the upper part of the cathode carbon block is designed as a trapezoidal sloping structure that is low in the middle and high on both sides.

Claims

1. A cathode carbon block structure for an aluminum electrolytic cell, characterized in that: in Along the length of the cathode carbon block, the two ends of the cathode carbon block have symmetrical circular closed cathode conductive output holes for mounting circular cathode steel rods. The inner diameter of the cathode conductive output holes corresponds to the outer diameter of the circular cathode steel rods. Under the high-temperature thermal conditions of electrolysis, the inner wall surface of the cathode conductive output holes of the cathode carbon block can directly form a dense iron-carbon interface conductive connection with the outer surface of the circular cathode steel rods by taking advantage of the fact that the thermal expansion coefficient of the circular cathode steel is greater than that of carbon graphite.

2. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: The cathode conductive output holes, which are symmetrically located at the ends of the same cathode carbon block, are set on the same horizontal center line along the length of the cathode carbon block.

3. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: Multiple symmetrical cathode conductive output holes are set at different heights on the same cathode carbon block.

4. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: The cathode conductive output holes on the same cathode carbon block are configured with different diameters.

5. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: The same cathode conductive output hole on the cathode carbon block is segmented with different diameters; that is, the same cathode conductive output hole adopts a design with equal diameter or a variable diameter design with non-equal diameter.

6. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: The same cathode conductive output hole is designed in two sections: one section uses a smooth rod design and the other section uses a threaded rod design.

7. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: Two cathode conductive output holes are symmetrically expanded on the same center line on two side sections of the cathode carbon block, with a certain width of horizontal spacing between them at the center of the cathode carbon block.

8. The cathode carbon block structure for an aluminum electrolytic cell according to claim 1, characterized in that: The upper part of the cathode carbon block is designed to be a trapezoidal sloping structure with a low middle and high sides.

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