Gradient resistance graphitized cathode carbon block and preparation method thereof

Abstract

The invention provides a gradient resistance graphitized cathode carbon block and a preparation method thereof, and belongs to the field of carbon materials. The gradient resistance graphitized cathode carbon block is composed of a base body layer, a resistance increasing layer and / or a resistance reducing layer. Wherein the resistance increasing layers are located at the two end parts of the gradient resistance graphitized cathode carbon block in the length direction and are symmetrically arranged; the resistance reducing layer is positioned in the middle of the gradient resistance graphitized cathode carbon block in the length direction; the room temperature resistivity of the resistance increasing layer is greater than the room temperature resistivity of the base body layer; and the room temperature resistivity of the resistance reducing layer is smaller than that of the base body layer. The resistance reducing layer is additionally arranged in the middle of the carbon block, the resistance increasing layers are additionally arranged at the two ends of the carbon block, distribution of current in the carbon block is optimized, uniform consumption of a cathode is achieved, the service life of an electrolytic cell is effectively prolonged, and therefore through the unique structure and material design, current distribution is optimized, and the comprehensive performance of the cathode carbon block is improved; the problem that a traditional graphitized cathode carbon block is uneven in current distribution is solved.

Description

Technical Field

[0001] The present application relates to the technical field of carbon materials, and in particular to a gradient resistance graphitized cathode carbon block and a preparation method thereof. Background Art

[0002] In the aluminum electrolysis industry, conventional graphitized cathode carbon blocks exhibit uneven current distribution in practical applications. This results in higher cathode current density in the side areas of the electrolytic cell, which in turn causes increased wear of the cathode carbon blocks in these areas, forming significant cathode corrosion pits. This issue is one of the key factors that shortens the life of electrolytic cells using graphitized cathode carbon blocks.

[0003] Current technological improvements are mainly focused on the mechanical strength, wear resistance and other physical properties of graphitized cathode carbon blocks, while research on optimizing current distribution and achieving gradient resistance is relatively scarce. However, none of these existing technical means have effectively solved the problem of uneven current distribution. Therefore, there is an urgent need to develop a graphitized cathode carbon block with gradient resistance to improve current distribution, thereby improving the overall performance of the cathode carbon block, extending the service life of the electrolytic cell, and promoting technological progress in the aluminum electrolysis industry. Summary of the Invention

[0004] The present application provides a gradient resistance graphitized cathode carbon block and a preparation method thereof, in order to solve the technical problem of uneven current distribution of existing graphitized cathode carbon blocks.

[0005] In a first aspect, an embodiment of the present application provides a gradient resistance graphitized cathode carbon block, wherein the gradient resistance graphitized cathode carbon block comprises a base layer, a resistance-increasing layer and / or a resistance-reducing layer; wherein,

[0006] The resistance layers are located at both ends of the gradient resistor graphitized cathode carbon block in the length direction and are arranged symmetrically;

[0007] The resistance reduction layer is located in the middle of the gradient resistance graphitized cathode carbon block in the length direction;

[0008] The room temperature resistivity of the resistance layer is greater than the room temperature resistivity of the base layer;

[0009] The room temperature resistivity of the resistance-reducing layer is less than the room temperature resistivity of the base layer.

[0010] Optionally, it is characterized in that the height of the resistance layer is 20% to 40% of the total height of the gradient resistor graphitized cathode carbon block, and the single-side length of the resistance layer is 20% to 30% of the total length of the gradient resistor graphitized cathode carbon block.

[0011] Optionally, the height of the resistance reduction layer is 20% to 40% of the total height of the gradient resistance graphitized cathode carbon block, and the length of the resistance reduction layer is 40% to 60% of the total length of the gradient resistance graphitized cathode carbon block.

[0012] Optionally, the resistance-increasing layer and the resistance-reducing layer are both at least 50 mm higher than the top of the conductive steel rod groove of the gradient resistance graphitized cathode carbon block.

[0013] Optionally, the paste of the base layer is composed of graphitized cathode carbon block material;

[0014] The paste of the resistance layer is composed of a graphitized cathode carbon block material and a first functional material, wherein the mass of the first functional material is 1% to 6% of the total mass of the resistance layer;

[0015] The paste of the resistance reduction layer is composed of a graphitized cathode carbon block material and a second functional material, and the mass of the second functional material is 1% to 5% of the total mass of the resistance reduction layer.

[0016] Optionally, the first functional material includes at least one of the following: silicon carbide, boron carbide and titanium carbide.

[0017] Optionally, the second functional material includes at least one of the following: titanium boride and carbon fiber.

[0018] Optionally, the room temperature resistivity of the resistance layer satisfies the following relationship:

[0019] 1μΩm≤ρ1-ρ2≤10μΩm

[0020] Wherein, ρ1 is the room temperature resistivity of the resistive layer, and ρ1 is 12 μΩm to 20 μΩm; ρ2 is the room temperature resistivity of the base layer, and ρ2≤12 μΩm.

[0021] Optionally, the room temperature resistivity of the resistance reduction layer satisfies the following relationship:

[0022] 1μΩm≤ρ2-ρ3≤5μΩm

[0023] Wherein, ρ2 is the room temperature resistivity of the substrate layer, and ρ2≤12 μΩm; ρ3 is the room temperature resistivity of the resistance-reducing layer, and ρ3 is 7 μΩm to 11 μΩm.

[0024] In a second aspect, the present application provides a method for preparing the gradient resistance graphitized cathode carbon block according to any one embodiment of the first aspect, the method comprising:

[0025] respectively obtaining pastes of the base layer, the resistance-increasing layer and / or the resistance-reducing layer;

[0026] Filling the paste of the base layer, the resistance-increasing layer and / or the resistance-reducing layer in layers according to set areas, and forming green blocks through vibration molding;

[0027] The green block is subjected to calcination, graphitization and mechanical processing in sequence to obtain the gradient resistor graphitized cathode carbon block.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The embodiment of the present application provides a gradient resistance graphitized cathode carbon block, which is composed of a base layer, a resistance-adding layer and / or a resistance-reducing layer; wherein the resistance-adding layer is located at both ends of the gradient resistance graphitized cathode carbon block in the length direction and is arranged symmetrically; the resistance-reducing layer is located in the middle of the gradient resistance graphitized cathode carbon block in the length direction; the room temperature resistivity of the resistance-adding layer is greater than the room temperature resistivity of the base layer; the room temperature resistivity of the resistance-reducing layer is less than the room temperature resistivity of the base layer. By adding a resistance-reducing layer in the middle of the carbon block (to reduce resistivity) and adding a resistance-adding layer at both ends of the carbon block (to increase resistivity), the distribution of current in the carbon block is optimized, thereby achieving uniform cathode consumption and effectively extending the life of the electrolytic cell. Thus, through unique structure and material design, the current distribution is optimized, the comprehensive performance of the cathode carbon block is improved, and the problem of uneven current distribution in traditional graphitized cathode carbon blocks is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 A schematic structural diagram of a gradient resistance graphitized cathode carbon block comprising a base layer, a resistance-increasing layer, and a resistance-reducing layer provided in an embodiment of the present application;

[0033] Figure 2 A schematic structural diagram of a gradient resistance graphitized cathode carbon block comprising a base layer and a resistance layer provided in an embodiment of the present application;

[0034] Figure 3 A schematic structural diagram of a gradient resistance graphitized cathode carbon block comprising a base layer and a resistance-reducing layer provided in an embodiment of the present application;

[0035] Figure 4A schematic flow chart of a method for preparing a gradient resistance graphitized cathode carbon block provided in an embodiment of the present application;

[0036] Figure 5 A schematic diagram of the actual process of preparing a gradient resistance graphitized cathode carbon block provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0039] In addition, in the description of the specification of this application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass represent the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0040] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0041] Figure 1 A schematic structural diagram of a gradient resistance graphitized cathode carbon block comprising a base layer, a resistance-increasing layer, and a resistance-reducing layer provided in an embodiment of the present application; Figure 2 A schematic structural diagram of a gradient resistance graphitized cathode carbon block comprising a base layer and a resistance layer provided in an embodiment of the present application; Figure 3 A schematic structural diagram of a gradient resistance graphitized cathode carbon block consisting of a base layer and a resistance-reducing layer provided in an embodiment of the present application.

[0042] like Figures 1 to 3 As shown, the present application provides a gradient resistance graphitized cathode carbon block, which is composed of a base layer, a resistance-increasing layer and / or a resistance-reducing layer; wherein,

[0043] The resistance layers are located at both ends of the gradient resistor graphitized cathode carbon block in the length direction and are arranged symmetrically;

[0044] The resistance reduction layer is located in the middle of the gradient resistance graphitized cathode carbon block in the length direction;

[0045] The room temperature resistivity of the resistance layer is greater than the room temperature resistivity of the base layer;

[0046] The room temperature resistivity of the resistance-reducing layer is less than the room temperature resistivity of the base layer.

[0047] It's important to note that in nearly all current electrolytic cell designs, current is drawn in through the anode, located at the top, and discharged through cathode steel rods on the two large sides of the cell. This current then makes a 90-degree bend within the cell. This uneven resistance distribution leads to uneven current distribution, characterized by a current density biased toward the output end.

[0048] The outer resistance is Rc (the sum of the cathode carbon block resistance and the contact resistance), the middle resistance is Rc + Rb (half the steel rod resistance), and the inner resistance is Rc + 2Rb. When Rb → 0, the current distribution tends to be uniform. The larger the 2Rb / Rc, the more the current distribution is concentrated toward the outside.

[0049] The greater the current flowing through the cathode carbon block, the more severe the corrosion at that location. For electrolytic cells using graphitized cathode carbon blocks, if the current distribution is not well designed, the cell life will be severely affected. This is because the resistivity of graphitized cathode carbon blocks (≤12μΩm) is only 1 / 2-1 / 3 of that of the commonly used GS-5 graphite cathode carbon blocks (≤30μΩm). This means that Rc decreases significantly while 2Rb / Rc increases, which means that the current distribution is concentrated toward the output end.

[0050] Therefore, the present embodiment adds a resistance-reducing layer (reducing resistivity) in the middle of the carbon block and a resistance-increasing layer (increasing resistivity) at both ends of the carbon block to optimize the current distribution within the carbon block, achieving uniform cathode consumption and effectively extending the life of the electrolytic cell. This unique structure and material design optimizes current distribution, improves the overall performance of the cathode carbon block, and solves the problem of uneven current distribution in traditional graphitized cathode carbon blocks.

[0051] In some embodiments, it is characterized in that the height of the resistance layer is 20% to 40% of the total height of the gradient resistance graphitized cathode carbon block, and the single-side length of the resistance layer is 20% to 30% of the total length of the gradient resistance graphitized cathode carbon block.

[0052] In some embodiments, the height of the resistance reducing layer is 20% to 40% of the total height of the gradient resistance graphitized cathode carbon block, and the length of the resistance reducing layer is 40% to 60% of the total length of the gradient resistance graphitized cathode carbon block.

[0053] This embodiment of the application effectively reduces the central resistance by providing a resistance-reducing layer (low-resistivity region) in the middle of the carbon block, guiding the current through the carbon block more evenly and reducing the accumulation of current at the output end. Resistance-enhancing layers (high-resistivity regions) are provided at both ends of the carbon block to increase the end resistance, further balancing the overall current distribution and achieving uniform cathode consumption.

[0054] The optimization of current distribution reduces cathode corrosion caused by excessive local current, thereby significantly extending the service life of the electrolytic cell. Compared with traditional graphitized cathode carbon blocks, the design of the present application better adapts to the high requirements of modern electrolytic cells for current distribution uniformity by finely controlling the resistance distribution. At the same time, the unique layered structure design combined with the optimization of material properties makes the gradient resistance graphitized cathode carbon block perform well in terms of conductivity, corrosion resistance and mechanical strength. The precise arrangement of the resistance-adding layer and the resistance-reducing layer not only solves the problem of uneven current distribution, but also improves the overall stability and durability of the carbon block. In addition, by adjusting the dimensions of the resistance-adding layer and the resistance-reducing layer (such as height and length), it is possible to flexibly respond to different electrolytic cell designs and current distribution requirements, providing the possibility for customized design of the electrolytic cell. Therefore, the structural design of the gradient resistance graphitized cathode carbon block in the embodiment of the present application effectively optimizes the flow path of the current in the carbon block by precisely controlling the resistance distribution, solves the problem of uneven current distribution in traditional cathode carbon blocks, and thus improves the overall performance and service life of the electrolytic cell.

[0055] For example, the height of the resistance-adding layer can be 20%, 30%, 35%, 38%, 40%, etc. of the total height of the gradient resistance graphitized cathode carbon block, and the length of a single side of the resistance-adding layer can be 20%, 22%, 24%, 26%, 28%, 30%, etc. of the total length of the gradient resistance graphitized cathode carbon block. The height of the resistance-reducing layer can be 20%, 25%, 30%, 35%, 40%, etc. of the total height of the gradient resistance graphitized cathode carbon block, and the length of the resistance-reducing layer can be 40%, 45%, 50%, 55%, 60%, etc. of the total length of the gradient resistance graphitized cathode carbon block.

[0056] In some embodiments, the resistance-increasing layer and the resistance-reducing layer are both at least 50 mm higher than the top of the conductive steel rod groove of the gradient resistance graphitized cathode carbon block.

[0057] The resistance-increasing layer and the resistance-reducing layer are both at least 50 mm higher than the top of the conductive steel rod groove of the gradient resistance graphitized cathode carbon block, which can avoid direct contact between the steel rod and the resistance-increasing layer and the resistance-reducing layer, leaving a transition in the middle.

[0058] In some embodiments, the paste of the substrate layer is composed of graphitized cathode carbon block material;

[0059] The paste of the resistance layer is composed of a graphitized cathode carbon block material and a first functional material, wherein the mass of the first functional material is 1% to 6% of the total mass of the resistance layer;

[0060] The paste of the resistance reduction layer is composed of a graphitized cathode carbon block material and a second functional material, and the mass of the second functional material is 1% to 5% of the total mass of the resistance reduction layer.

[0061] In some embodiments, the first functional material includes at least one of the following: silicon carbide, boron carbide, and titanium carbide.

[0062] In some embodiments, the second functional material includes at least one of the following: titanium boride and carbon fiber.

[0063] The matrix layer is made of conventional materials used in the production of graphitized cathode carbon blocks, including calcined petroleum coke, asphalt, etc. The requirements for calcined petroleum coke must comply with the standard "YS / T 763-2019 Calcined Petroleum Coke for Graphitized Cathode Carbon Blocks". The asphalt used in the production of graphitized cathode carbon blocks is modified asphalt, which must comply with the standard "YB / T 5194-2024 Modified Asphalt". The asphalt components are extremely complex, most of which are aromatic hydrocarbons with three or more rings, as well as heterocyclic compounds containing elements such as oxygen, nitrogen and sulfur, and a small amount of high-molecular carbon substances. The chemical components of graphitized cathode carbon blocks are carbon and no more than 0.5% ash (inorganic matter).

[0064] The first functional material is one or more of silicon carbide, boron carbide, and titanium carbide. Silicon carbide, boron carbide, and titanium carbide have slightly lower electrical conductivity than graphite and are resistant to high temperatures and corrosion. Adding the first functional material to the graphite material at a ratio of 1% to 6% of the total mass of the resistive layer can achieve a controllable increase in the resistivity of the graphitized cathode carbon block. For example, the mass of the first functional material can be 1%, 2%, 3%, 4%, 5%, or 6% of the total mass of the resistive layer.

[0065] The second functional material is one or both of titanium boride and carbon fiber. Titanium boride and carbon fiber offer superior electrical conductivity compared to graphite and are also resistant to high temperatures and corrosion. Adding the second functional material to the graphite material at a ratio of 1% to 5% of the total mass of the resistance-reduction layer can achieve a controlled reduction in the resistivity of the graphitized cathode carbon block. For example, the mass of the second functional material can range from 1%, 2%, 3%, 4%, or 5% of the total mass of the resistance-reduction layer.

[0066] In some embodiments, the room temperature resistivity of the resistive layer satisfies the following relationship:

[0067] 1μΩm≤ρ1-ρ2≤10μΩm

[0068] Wherein, ρ1 is the room temperature resistivity of the resistive layer, and ρ1 is 12 μΩm to 20 μΩm; ρ2 is the room temperature resistivity of the base layer, and ρ2≤12 μΩm.

[0069] In some embodiments, the room temperature resistivity of the resistance reducing layer satisfies the following relationship:

[0070] 1μΩm≤ρ2-ρ3≤5μΩm

[0071] Wherein, ρ2 is the room temperature resistivity of the substrate layer, and ρ2≤12 μΩm; ρ3 is the room temperature resistivity of the resistance-reducing layer, and ρ3 is 7 μΩm to 11 μΩm.

[0072] It should be noted that the resistance layer is based on the base layer composition formula, with the addition of silicon carbide, boron carbide, and titanium carbide. As the total proportion of these additives increases, the resistivity of the resistance layer gradually increases compared to the base layer. The ash content, compressive strength, apparent density, true density, sodium expansion coefficient, and thermal expansion coefficient of the resistance layer also gradually increase, while the thermal conductivity of the resistance layer decreases to a certain extent. The main function of the resistance layer is to increase the resistivity of the area, thereby reducing the current flowing through it.

[0073] The resistance-reduction layer is constructed from titanium boride and carbon fiber functional materials added to the base layer's composition. As the total proportion of these additives increases, the resistivity of the resistance-reduction layer decreases compared to the base layer. The ash content, compressive strength, apparent density, true density, sodium expansion coefficient, and thermal expansion coefficient of the resistance-reduction layer gradually increase, while the thermal conductivity of the resistance-reduction layer also increases to a certain extent. The resistance-reduction layer primarily reduces the resistivity of the area, thereby increasing the current flowing through it.

[0074] Figure 4 A schematic flow chart of a method for preparing a gradient resistance graphitized cathode carbon block provided in an embodiment of the present application; Figure 5 A schematic diagram of the actual process of preparing a gradient resistance graphitized cathode carbon block provided in an embodiment of the present application.

[0075] Based on a general inventive concept, such as Figure 4 and Figure 5 As shown, the present application provides a method for preparing the gradient resistance graphitized cathode carbon block according to any one of the above embodiments, the method comprising:

[0076] S1. respectively obtaining pastes of the base layer, the resistance-increasing layer and / or the resistance-reducing layer;

[0077] S2, filling the paste of the base layer, the resistance-increasing layer and / or the resistance-reducing layer in layers according to the set areas, and forming green blocks by vibration molding;

[0078] S3, sequentially performing calcination, graphitization and mechanical processing on the green block to obtain the gradient resistor graphitized cathode carbon block.

[0079] It should be noted that the specific preparation method of the gradient resistor graphitized cathode carbon block includes: placing the mixed carbon block matrix layer paste into the forming mold of the vibration molding machine, using partitions to partition the upper part of the current matrix layer paste, placing the mixed carbon block resistance layer and resistance reduction layer pastes into the designed area, and then placing the carbon block matrix layer paste again, removing the partition, and performing integrated vibration molding. After the molded raw carbon block is roasted, it is graphitized and finally mechanically processed into a graphitized cathode carbon block product.

[0080] The product prepared by the preparation method of the gradient resistance graphitized cathode carbon block is the above-mentioned gradient resistance graphitized cathode carbon block. The chemical composition and structural organization of the gradient resistance graphitized cathode carbon block prepared by the preparation method of the gradient resistance graphitized cathode carbon block can refer to the above-mentioned embodiment. Since the preparation method of the gradient resistance graphitized cathode carbon block adopts part or all of the technical solutions of the gradient resistance graphitized cathode carbon block embodiment, it at least has all the beneficial effects brought by the technical solutions of the gradient resistance graphitized cathode carbon block embodiment, which will not be repeated here.

[0081] In summary, the gradient resistance graphitized cathode carbon block and its preparation method provided in the embodiments of the present application have many significant advantages, which are summarized as follows:

[0082] (1) Optimization of current distribution and extension of electrolytic cell life: By setting a resistance-reducing layer (low resistivity area) in the middle of the carbon block and a resistance-enhancing layer (high resistivity area) at both ends, fine control of the resistance distribution is achieved. This design effectively guides the current through the carbon block more evenly, reduces the accumulation of current at the output end, and thus balances the overall current distribution. At the same time, the optimization of current distribution significantly reduces the risk of cathode corrosion caused by excessive local current, helps to extend the service life of the electrolytic cell and improve the stability and durability of the equipment.

[0083] (2) Perfect combination of material performance and structural design: The unique layered structure design makes the gradient resistance graphitized cathode carbon block perform well in terms of conductivity, corrosion resistance and mechanical strength. The precise arrangement of the resistance-increasing layer and the resistance-reducing layer not only solves the problem of uneven current distribution, but also improves the overall performance of the carbon block. At the same time, functional materials such as silicon carbide, boron carbide and titanium carbide are added to the resistance-increasing layer. These materials are resistant to high temperatures and corrosion, and can controllably increase the resistivity. Functional materials such as titanium boride and carbon fiber are added to the resistance-reducing layer. These materials have excellent conductivity and can controllably reduce the resistivity.

[0084] (3) Flexibility and customized design: The height and length of the resistance-increasing layer and the resistance-reducing layer can be adjusted according to actual needs, which makes it possible to customize the design of the electrolytic cell. This flexibility enables the gradient resistance graphitized cathode carbon block to adapt to different electrolytic cell designs and current distribution requirements. At the same time, the resistance-increasing layer and the resistance-reducing layer are limited to at least 50 mm above the top of the conductive steel rod groove, avoiding direct contact between the steel rod and the resistance-increasing layer and the resistance-reducing layer, leaving a transition area in the middle, further improving the rationality and practicality of the design.

[0085] (4) Advantages of the preparation method: The preparation method includes the steps of paste preparation, layered filling, vibration molding, roasting, graphitization, and mechanical processing. The process is clear and easy to operate, which helps to improve production efficiency and reduce production costs. At the same time, by precisely controlling the ratio of each layer of paste and the preparation process parameters, the quality stability and consistency of the gradient resistor graphitized cathode carbon block can be ensured.

[0086] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0087] Example 1

[0088] Produce gradient resistance graphitized cathode carbon block products containing matrix layer, resistance layer and resistance reduction layer. The final product is as follows Figure 1 shown.

[0089] (1) Raw material formula

[0090] Matrix layer: conventional graphitized cathode carbon block materials (including calcined petroleum coke, asphalt, etc.) are used.

[0091] Resistance layer: Silicon carbide, boron carbide, and titanium carbide are added to conventional graphitized cathode carbon blocks to increase resistance. A combination of one or more of these materials is used. The amount added is a percentage of the total mass of the layer. Table 1 lists some combinations, but actual use is not limited to these.

[0092] Table 1 Addition amount of functional materials in the resistance layer

[0093] combination Silicon carbide Boron carbide titanium carbide total Resistance layer 1 6％ 0 0 6％ Resistance layer 2 0 6％ 0 6％ Resistance layer 3 0 0 6％ 6％ Resistance layer 4 1％ 2％ 0 3％ Resistance layer 5 2％ 0 1％ 3％ Resistance layer 6 1％ 2％ 3％ 6％ Resistance layer 7 3％ 1％ 1％ 5％

[0094] Resistance-reducing layer: Titanium boride and carbon fiber functional materials are added to the conventional graphitized cathode carbon block to reduce resistance. One or a combination of these functional materials is used. The amount added is a percentage of the total mass of the layer. Table 2 lists some combinations, but actual use is not limited to these.

[0095] Table 2 Addition amount of functional materials in the resistance reduction layer

[0096] combination Titanium boride carbon fiber total Resistance reduction layer 1 4％ 1％ 5％ Resistance reduction layer 2 5％ 0 5％ Resistance reduction layer 3 3％ 0.5％ 3.5％ Resistance reduction layer 4 2％ 1％ 3％ Resistance reduction layer 5 0％ 3％ 3％

[0097] (2) Preparation steps

[0098] Mixing and kneading the ingredients: Mix the raw materials of the base layer, resistance-adding layer and resistance-reducing layer according to the formula, heat them to 145°C in a mixer, dry mix them for 30 minutes, add 21% coal tar as a binder of the total mass of the paste, continue wet mixing, the wet mixing temperature is 180°C, the wet mixing time is 45 minutes, and form a uniform paste.

[0099] Vibration molding:

[0100] Fill the vibrating mold with the matrix paste, laying it to a thickness of 50% of the total carbon block height. After vibrating, the paste is compressed and reduced in volume. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block is 430mm tall, the initial matrix layer height is approximately 430 x 50% x 1.5 = 323mm.

[0101] Place two spacers on top of the already laid base layer paste to form three areas: a resistance-enhancing layer, a resistance-reducing layer, and a resistance-enhancing layer. The two resistance-enhancing layers are the same length, with the length of a single resistance-enhancing layer being 25% of the total length of the carbon block. For example, if the total length is 3580mm, the length of the resistance-enhancing layer on one side is approximately 3580×25%=895mm; the length of the resistance-reducing layer is approximately 3580×(1-2×25%)=1790mm.

[0102] Fill the resistance-enhancing and resistance-reducing layers with the corresponding paste, each to a thickness of 30% of the total carbon block height. After vibrating and forming the paste, the paste volume is compressed and reduced. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block has a total height of 430 mm, the initial filling height of the resistance-enhancing and resistance-reducing layers is approximately 430 × 30% × 1.5 = 194 mm.

[0103] Continue filling the mold with the remaining base layer paste until it reaches the designed height. After vibrating the paste, the paste volume is compressed and reduced. Assume the ratio of paste height to green block height is 1.5:1. For example, if the green block has a total height of 430 mm, the final total height of the paste will be 430 x 1.5 = 645 mm. Remove the spacers.

[0104] The vibration forming machine is started to form green blocks. The height of the carbon block steel bar groove is 145 mm, and the distance between the resistance-increasing layer and the resistance-reducing layer and the top of the steel bar groove is about 430 × 50% - 145 = 70 mm.

[0105] Roasting treatment: The green block is placed in a roasting furnace and roasted to obtain a roasted block.

[0106] Graphitization treatment: The calcined block is placed in a graphitization furnace for high-temperature treatment to obtain a graphitized block. The room temperature resistivity of the added resistance layer after graphitization is 12μΩm to 20μΩm, the room temperature resistivity of the reduced resistance layer after graphitization is 7μΩm to 11μΩm, and the resistivity of the base layer is 11μΩm.

[0107] Machining: The graphitized block is machined to finally obtain the graphitized cathode carbon block product.

[0108] Example 2

[0109] Produce gradient resistance graphitized cathode carbon block products containing matrix layer and resistance layer, the final product is as follows Figure 2 shown.

[0110] (1) Raw material formula

[0111] Matrix layer: conventional graphitized cathode carbon block materials (including calcined petroleum coke, asphalt, etc.) are used.

[0112] Resistance layer: Silicon carbide, boron carbide, and titanium carbide are added to conventional graphitized cathode carbon blocks to increase resistance. A combination of one or more of these materials is used. The amount added is a percentage of the total mass of the layer. Table 1 lists some combinations, but actual use is not limited to these.

[0113] (2) Preparation steps

[0114] Mixing the ingredients: Mix the raw materials of the base layer and the resistance layer according to the formula, heat them to 145°C in a mixer, dry mix them for 30 minutes, add 21% coal tar as a binder according to the total mass of the paste, continue wet mixing, the wet mixing temperature is 180°C, the wet mixing time is 45 minutes, and form a uniform paste.

[0115] Vibration molding:

[0116] Fill the vibrating mold with the matrix paste, laying it to a thickness of 60% of the total carbon block height. After vibrating, the paste is compressed and reduced in volume. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block has a total height of 430mm, the initial matrix layer filling height is approximately 430 x 60% x 1.5 = 387mm.

[0117] Place two spacers on top of the already laid base layer paste to form three areas: the resistance layer, the base layer, and the resistance layer. The two resistance layers are the same length, with the length of each resistance layer being 30% of the total length of the carbon block. For example, if the total length is 3580mm, the length of the resistance layer on one side is approximately 3580×30%=1074mm; the length of the base layer is approximately 3580×(1-2×30%)=1432mm.

[0118] The resistance-enhancing layer and base layer are filled with the corresponding paste, each with a thickness of 20% of the total carbon block height. After the paste is vibrated and formed, its volume is compressed and reduced. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block has a total height of 430 mm, the initial filling height of the resistance-enhancing layer and the resistance-reducing layer is approximately 430 × 20% × 1.5 = 129 mm.

[0119] Continue filling the mold with the remaining base layer paste until it reaches the designed height. After vibrating the paste, the paste volume is compressed and reduced. Assume the ratio of paste height to green block height is 1.5:1. For example, if the green block has a total height of 430 mm, the final total height of the paste will be 430 x 1.5 = 645 mm. Remove the spacers.

[0120] The vibration forming machine is started to form green blocks. The height of the steel bar groove of the carbon block is 145 mm, and the distance between the gradient layer and the top of the steel bar groove is about 430×60%-145=113 mm.

[0121] Roasting treatment: The green block is placed in a roasting furnace and roasted to obtain a roasted block.

[0122] Graphitization treatment: The calcined block is placed in a graphitization furnace for high-temperature treatment to obtain a graphitized block. After graphitization, the resistivity of the resistive layer is 12μΩm to 20μΩm at room temperature, and the resistivity of the base layer is 10μΩm.

[0123] Machining: The graphitized block is machined to finally obtain the graphitized cathode carbon block product.

[0124] Example 3

[0125] Produce gradient resistance graphitized cathode carbon block products containing matrix layer and resistance reduction layer, the final product is Figure 3 shown.

[0126] (1) Raw material formula

[0127] Matrix layer: conventional graphitized cathode carbon block materials (including calcined petroleum coke, asphalt, etc.) are used.

[0128] Resistance-reducing layer: Titanium boride and carbon fiber functional materials are added to conventional graphitized cathode carbon blocks to reduce resistance. One or a combination of these materials is used. The amount added is a percentage of the total mass of the layer. Table 2 lists some combinations, but actual use is not limited to these.

[0129] (2) Preparation steps

[0130] Mixing the ingredients: Mix the raw materials of the base layer and the resistance reduction layer according to the formula, heat them to 145°C in a mixer, dry mix them for 30 minutes, add 21% coal tar as a binder by the total mass of the paste, continue wet mixing, the wet mixing temperature is 180°C, the wet mixing time is 45 minutes, and form a uniform paste.

[0131] Vibration molding:

[0132] Fill the vibrating mold with the matrix paste, laying it to a thickness of 47% of the total carbon block height. After vibrating, the paste is compressed and reduced in volume. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block has a total height of 430mm, the initial matrix layer filling height is approximately 430 x 47% x 1.5 = 303mm.

[0133] Two separators are placed above the already laid base layer paste, forming three areas: the base layer, the resistance reduction layer, and the base layer. The two base layers are the same length, with the length of a single base layer being 20% of the total length of the carbon block. For example, if the total length is 3580mm, the length of a single base layer is approximately 3580×20%=716mm; the length of the resistance reduction layer is approximately 3580×(1-2×20%)=2148mm.

[0134] The base layer and drag reduction layer are filled with the corresponding paste, each to a thickness of 50% of the total carbon block height. After vibrating and forming the paste, the paste volume is compressed and reduced. Assuming a 1.5:1 ratio between the paste height and the green block height, for example, if the green block has a total height of 430 mm, the initial filling height of the base layer and drag reduction layer is approximately 430 × 50% × 1.5 = 323 mm.

[0135] Continue filling the mold with the remaining base layer paste until it reaches the designed height. After vibrating the paste, the paste volume is compressed and reduced. Assume the ratio of paste height to green block height is 1.5:1. For example, if the green block has a total height of 430 mm, the final total height of the paste will be 430 x 1.5 = 645 mm. Remove the spacers.

[0136] The vibration forming machine is started to form green blocks. The height of the steel bar groove of the carbon block is 145 mm, and the distance between the gradient layer and the top of the steel bar groove is about 430×47%-145=57 mm.

[0137] Roasting treatment: The green block is placed in a roasting furnace and roasted to obtain a roasted block.

[0138] Graphitization treatment: The calcined block is placed in a graphitization furnace for high-temperature treatment to obtain a graphitized block. After graphitization, the room temperature resistivity of the resistance-reducing layer is 7μΩm to 11μΩm, and the resistivity of the base layer is 12μΩm.

[0139] Machining: The graphitized block is machined to finally obtain the graphitized cathode carbon block product.

[0140] The performance of the base layer, resistance-adding layer 1 to resistance-adding layer 7, and resistance-reducing layer 1 to resistance-reducing layer 5 in Examples 1 to 3 was measured, and the results are shown in Table 3.

[0141] Table 3 Properties of base layer, resistance-adding layer 1 to resistance-adding layer 7, and resistance-reducing layer 1 to resistance-reducing layer 5

[0142]

[0143]

[0144] In Table 3, the substrate layer is the conventional graphitized cathode.

[0145] The resistive layer is constructed by adding silicon carbide, boron carbide, and titanium carbide to the base layer's composition. As the total proportion of these additives increases, the resistive layer's resistivity gradually increases compared to the base layer. The ash content, compressive strength, apparent density, true density, sodium expansion coefficient, and thermal expansion coefficient of the resistive layer also gradually increase, while the thermal conductivity of the layer decreases somewhat. The resistive layer's primary function is to increase the resistivity of the area, thereby reducing the current flowing through it.

[0146] The resistance-reduction layer is constructed from titanium boride and carbon fiber functional materials added to the base layer's composition. As the total proportion of these additives increases, the resistivity of the resistance-reduction layer decreases compared to the base layer. The ash content, compressive strength, apparent density, true density, sodium expansion coefficient, and thermal expansion coefficient of the resistance-reduction layer gradually increase, while the thermal conductivity of the resistance-reduction layer also increases to a certain extent. The resistance-reduction layer primarily reduces the resistivity of the area, thereby increasing the current flowing through it.

[0147] It should be noted that the gradient resistance graphitized cathode carbon block in Example 1 is composed of a base layer, a resistance-adding layer and a resistance-reducing layer. The base layer can be any one of the base layers 1 to 3 in Table 3, the resistance-adding layer can be any one of the resistance-adding layers 1 to 7 in Table 3, and the resistance-reducing layer can be any one of the resistance-reducing layers 1 to 5. In other words, any one of the base layers 1 to 3, any one of the resistance-adding layers 1 to 7, and any one of the resistance-reducing layers 1 to 5 can be arbitrarily combined to form a gradient resistance graphitized cathode carbon block. Example 2 is similar to Example 3 and will not be described in detail. Since the room temperature resistivity of the resistance-adding layer in Examples 1 to 3 is higher than that of the base layer by 1μΩm to 10μΩm, and the room temperature resistivity of the resistance-reducing layer is lower than that of the base layer by 1μΩm to 5μΩm, the distribution of current in the carbon block is optimized, achieving the technical effect of uniform cathode consumption and effective extension of the life of the electrolytic cell.

[0148] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0149] In the embodiments of the present application, the problem of uneven current distribution of traditional graphitized cathode carbon blocks is solved. Through unique structure and material design, the current distribution is optimized, the comprehensive performance of the cathode carbon blocks is improved, the service life of the electrolytic cell is extended, and technological progress in the aluminum electrolysis industry is promoted.

[0150] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A gradient resistance graphitized cathode carbon block, the gradient resistance graphitized cathode carbon block comprising a base layer, a resistance-increasing layer and / or a resistance-reducing layer; wherein: The resistance layers are located at both ends of the gradient resistor graphitized cathode carbon block in the length direction and are arranged symmetrically; The resistance reduction layer is located in the middle of the gradient resistance graphitized cathode carbon block in the length direction; The room temperature resistivity of the resistance layer is greater than the room temperature resistivity of the base layer; The room temperature resistivity of the resistance-reducing layer is less than the room temperature resistivity of the base layer.

2. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The height of the resistance layer is 20% to 40% of the total height of the gradient resistance graphitized cathode carbon block, and the single side length of the resistance layer is 20% to 30% of the total length of the gradient resistance graphitized cathode carbon block.

3. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The height of the resistance-reducing layer is 20% to 40% of the total height of the gradient resistance graphitized cathode carbon block, and the length of the resistance-reducing layer is 40% to 60% of the total length of the gradient resistance graphitized cathode carbon block.

4. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The resistance-increasing layer and the resistance-reducing layer are both at least 50 mm higher than the top of the conductive steel rod groove of the gradient resistance graphitized cathode carbon block.

5. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The paste of the substrate layer is composed of graphitized cathode carbon block material; The paste of the resistance layer is composed of a graphitized cathode carbon block material and a first functional material, wherein the mass of the first functional material is 1% to 6% of the total mass of the resistance layer; The paste of the resistance reduction layer is composed of a graphitized cathode carbon block material and a second functional material, and the mass of the second functional material is 1% to 5% of the total mass of the resistance reduction layer.

6. The gradient resistor graphitized cathode carbon block according to claim 5, characterized in that: The first functional material includes at least one of the following: silicon carbide, boron carbide, and titanium carbide.

7. The gradient resistor graphitized cathode carbon block according to claim 5, characterized in that: The second functional material includes at least one of the following: titanium boride and carbon fiber.

8. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The room temperature resistivity of the resistance layer satisfies the following relationship: 1μΩm≤ρ1-ρ2≤10μΩm Wherein, ρ1 is the room temperature resistivity of the resistive layer, and ρ1 is 12 μΩm to 20 μΩm; ρ2 is the room temperature resistivity of the base layer, and ρ2≤12 μΩm.

9. The gradient resistor graphitized cathode carbon block according to claim 1, characterized in that: The room temperature resistivity of the resistance reduction layer satisfies the following relationship: 1μΩm≤ρ2-ρ3≤5μΩm Wherein, ρ2 is the room temperature resistivity of the substrate layer, and ρ2≤12 μΩm; ρ3 is the room temperature resistivity of the resistance-reducing layer, and ρ3 is 7 μΩm to 11 μΩm.

10. A method for preparing a gradient resistance graphitized cathode carbon block according to any one of claims 1 to 9, characterized in that: The method comprises: respectively obtaining pastes of the base layer, the resistance-increasing layer and / or the resistance-reducing layer; Filling the paste of the base layer, the resistance-increasing layer and / or the resistance-reducing layer in layers according to set areas, and forming green blocks through vibration molding; The green block is subjected to calcination, graphitization and mechanical processing in sequence to obtain the gradient resistor graphitized cathode carbon block.

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