Production process of prebaked anode with high oxidation resistance

Abstract

The invention belongs to the technical field of high-oxidation-resistance prebaked anode production, and particularly relates to a high-oxidation-resistance prebaked anode production process which comprises the following steps: S1, raw material selection and pretreatment: selecting high-purity petroleum coke with the ash content not exceeding 0.3 wt% and the sulfur content not exceeding 0.15 wt% as a main raw material, and matching with at least 15 wt% of high-quality needle coke; before mixing, performing ultrasonic cleaning treatment on the petroleum coke and the needle coke, and then drying the petroleum coke and the needle coke so as to remove impurities and moisture attached to the surfaces of the petroleum coke and the needle coke; according to the invention, two-stage heat treatment and an accurate atmosphere regulation and control technology are adopted, and the composite siliconizing protection layer is formed, so that the oxidation resistance of the anode is remarkably improved; the mass loss of the optimized anode in a high-temperature oxidation environment is greatly reduced, so that the service life of the anode is effectively prolonged; the innovative technology not only improves the durability of the anode, but also reduces the production cost and environmental burden caused by frequent replacement of the anode.

Description

Technical Field

[0001] The invention relates to the technical field of production of prebaked anodes with high oxidation resistance, and in particular to a production process of prebaked anodes with high oxidation resistance. Background Art

[0002] In the electrolytic aluminum industry, prebaked anodes are key components of electrolytic cells, and their performance directly affects electrolytic efficiency, energy consumption, and production costs. Although the traditional prebaked anode production process has met the needs of electrolytic aluminum production to a certain extent, it still has many shortcomings in terms of anti-oxidation performance, service life, and automation and intelligence of the production process.

[0003] First, the anti-oxidation performance of the anode in the traditional process is limited, resulting in a rapid loss of anode mass and a short service life in a high-temperature oxidizing environment. This not only increases the frequency of anode replacement and production costs, but may also have an adverse effect on the stable operation of the electrolyzer. Therefore, how to improve the anti-oxidation performance of the anode and extend its service life has become a problem that needs to be solved urgently.

[0004] Secondly, the traditional process does not accurately control the anode microstructure, resulting in deficiencies in the anode's mechanical strength, electrical conductivity, corrosion resistance, and wear resistance. These performance defects limit the applicability of the anode in complex and changeable electrolytic environments, affecting the production efficiency and product quality of electrolytic aluminum.

[0005] In addition, the automation and intelligence level of the traditional anode production process is low, and it mainly relies on manual operation and experience judgment. This not only reduces production efficiency and increases labor costs, but also may lead to unstable product quality due to human errors. For this reason, we provide a high oxidation resistance prebaked anode production process. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a production process for a prebaked anode with high oxidation resistance, so as to more accurately solve the problems raised in the above background technology.

[0007] The present invention is achieved through the following technical solutions: The invention proposes a production process of a prebaked anode with high oxidation resistance, comprising the following steps: S1. Raw material selection and pretreatment: high-purity petroleum coke with an ash content of no more than 0.3% by weight and a sulfur content of no more than 0.15% by weight is selected as the main raw material, and at least 15% by weight of high-quality needle coke is added; before mixing, the petroleum coke and needle coke are subjected to ultrasonic cleaning treatment, and then dried to remove impurities and moisture attached to the surface; S2. Additive mixing and paste preparation: Add specific proportions of calcium silicate, aluminum oxide powder and rare earth oxide to the anode paste as an antioxidant system, wherein the amount of calcium silicate added is 1.5%-2.5% of the total mass of the paste, the amount of aluminum oxide added is 3%-4.5%, and the amount of rare earth oxide added is 0.15%-0.45%; the rare earth oxide is previously subjected to nano-grinding treatment to improve its dispersion uniformity and chemical activity in the paste.

[0008] Furthermore, the following heat treatment steps are also included: S3, two-stage heat treatment and precise atmosphere control: The first stage: in an inert gas atmosphere, heating to 400°C-500°C at a heating rate not exceeding 80°C / h and keeping the temperature for 2.5 hours to achieve effective removal of volatiles and preliminary graphitization; The second stage: under the same inert gas protection, heat to 1200°C-1300°C at a heating rate of 60°C-120°C / h and keep warm for 8-9 hours; in the high temperature stage, introduce a small amount of hydrogen to promote the deep optimization of the graphite structure and the improvement of crystallinity.

[0009] Furthermore, the following surface modification step is also included: S4. Formation of composite siliconization protective layer: Using chemical vapor deposition technology, in an inert gas atmosphere, the anode is heated to 1000°C-1100°C, and silane gas and silicon carbide precursor gas are introduced to perform siliconization and silicon carbide co-deposition treatment for 2 hours, thereby forming a composite protective layer composed of silicide and silicon carbide on the surface of the anode, which significantly enhances the oxidation resistance and wear resistance of the anode.

[0010] Furthermore, the method further comprises the following steps: S5. Precision machining after anode forming: Precision machining of the heat-treated anode, including but not limited to surface grinding, size correction and necessary hole machining, to ensure the precise fit between the anode and the electrolytic cell, while optimizing the heat dissipation performance of the anode.

[0011] Furthermore, the following quality inspection and control steps are included: a Anti-oxidation performance test: using the accelerated oxidation test method, that is, constant temperature oxidation in air at 850°C for 20 hours, the anode mass loss does not exceed 1.5%; b. Resistivity test: Ensure that the resistivity of the anode is less than 18μΩ·m; c Mechanical strength test: The flexural strength of the anode shall not be less than 35MPa; d Microstructure analysis: Scanning electron microscopy and X-ray diffraction analysis confirmed that the degree of graphitization was high and the grains were arranged in an orderly manner; e Corrosion resistance test: After immersion in an electrolyte solution containing fluoride ions for 48 hours, the anode mass loss does not exceed 0.5%.

[0012] Furthermore, the storage and management steps of raw materials are also included: Before raw material selection and pretreatment, high-purity petroleum coke and high-quality needle coke are strictly stored and managed to ensure that the storage environment is dry and dust-free, and the temperature and humidity are controlled within an appropriate range to prevent the raw materials from moisture, oxidation or contamination.

[0013] Furthermore, the additive mixing and paste preparation step also includes a homogenization process of the paste: After adding the antioxidant system, the paste is fully mixed and homogenized using equipment such as a high-speed mixer or a ball mill to ensure that the antioxidant is evenly distributed in the paste to improve the overall antioxidant performance of the anode.

[0014] Furthermore, the two-stage heat treatment and atmosphere precise control step also includes the control of temperature gradient: During the heating process, a suitable temperature gradient is formed by precisely controlling the heating rate and holding time to promote uniform graphitization of the internal structure of the anode and effective removal of volatiles, while avoiding cracks or deformation of the anode due to rapid temperature changes.

[0015] Furthermore, the step of forming the composite siliconized protective layer also includes controlling the thickness of the protective layer: By adjusting parameters such as gas flow, deposition time and temperature during chemical vapor deposition, the thickness of the protective layer formed by siliconization and silicon carbide co-deposition treatment is precisely controlled to ensure that the protective layer has sufficient oxidation resistance and wear resistance without affecting the conductivity and mechanical strength of the anode.

[0016] Furthermore, the method also includes the steps of packaging and storing the finished anode products: The finished anode products that have undergone precision processing and passed quality inspection are properly packaged to prevent contamination, damage or oxidation during transportation and storage; at the same time, the temperature and humidity of the storage environment are controlled to ensure that the finished anode products maintain stable performance during long-term storage.

[0017] Beneficial effects of the present invention: The present invention significantly improves the anti-oxidation performance of the anode by adopting two-stage heat treatment and precise atmosphere control technology, combined with the formation of a composite silicon-diffused protective layer; the mass loss of the anode after optimized treatment in a high-temperature oxidizing environment is greatly reduced, thereby effectively extending the service life of the anode; this innovative technology not only improves the durability of the anode, but also reduces the production cost and environmental burden caused by frequent replacement of the anode.

[0018] The present invention forms a suitable temperature gradient by precisely controlling parameters such as the heating rate, holding time and atmosphere composition during the heat treatment process, thereby achieving precise regulation and optimization of the anode microstructure; the optimization of this microstructure not only improves the mechanical strength and electrical conductivity of the anode, but also enhances its corrosion resistance and wear resistance; in addition, the composite siliconized protective layer formed by chemical vapor deposition technology further enhances the surface performance of the anode, making it more adaptable to complex and changeable electrolytic environments.

[0019] The present invention realizes the automation and intelligence of the anode production process by introducing advanced equipment and technical means such as high-precision CNC machine tools, resistivity testers, scanning electron microscopes, etc. The application of these technologies not only improves production efficiency and product quality, but also reduces errors and risks of manual operations; at the same time, by establishing a complete system of raw material storage and management, quality inspection and control, the stability and traceability of the anode production process are ensured, providing a strong guarantee for the high-quality production of anodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flowchart of an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings.

[0022] like Figure 1 As shown, a high oxidation resistance prebaked anode production process proposed in one embodiment of the present invention includes raw material selection and pretreatment: selecting high-purity petroleum coke with an ash content of 0.28±0.02% by weight and a sulfur content of 0.13±0.01% by weight as the main raw material to ensure the high purity and low impurity content of the raw material; matching with 20±2% by weight of high-quality needle coke to enhance the mechanical strength and conductivity of the anode; before mixing, using ultrasonic cleaning equipment to deeply clean the petroleum coke and needle coke to remove fine particles and grease attached to the surface, and the cleaning time is not less than 30 minutes; then drying in an oven at 80±5°C for 4±0.5 hours to ensure that moisture is completely removed to avoid affecting subsequent processes; the surface cleanliness and dryness of the raw materials after pretreatment are optimal, providing a high-quality raw material foundation for subsequent processes.

[0023] Furthermore, it also includes S3 two-stage heat treatment and precise atmosphere control: the first stage: in a nitrogen atmosphere, heating to 450±20°C at a heating rate of 60±5°C / h, and keeping warm for 2.5±0.1 hours to ensure effective removal of volatiles and preliminary graphitization; the second stage: under the same nitrogen protection, heating to 1250±20°C at a heating rate of 90±10°C / h, and keeping warm for 8.5±0.2 hours. In the high temperature stage, hydrogen with a volume fraction of 0.75±0.05% is introduced to promote the deep optimization of the graphite structure and the improvement of crystallinity; by precisely controlling the heating rate, holding time and atmosphere composition, the uniform graphitization of the internal structure of the anode and the effective removal of volatiles are ensured; the graphitization degree of the anode after heat treatment is significantly improved, and the conductivity and oxidation resistance are enhanced, while avoiding cracks or deformation caused by rapid temperature changes.

[0024] Furthermore, it also includes the formation of a composite siliconized protective layer, specifically using chemical vapor deposition technology, heating the anode to 1050±10°C in a nitrogen atmosphere to ensure that the anode surface reaches a suitable reaction temperature; introducing silane gas and silicon carbide precursor gas for co-deposition treatment, the treatment time is 2±0.1 hours. By precisely controlling parameters such as gas flow, deposition time and temperature, the uniformity and thickness of the protective layer are ensured; the formed protective layer is mainly composed of silicide and silicon carbide, and the thickness is controlled within the range of 10±1 microns, which has sufficient oxidation resistance and wear resistance, and does not affect the electrical conductivity and mechanical strength of the anode; a uniform and dense composite protective layer is formed on the surface of the anode, which significantly improves the oxidation resistance and wear resistance of the anode.

[0025] Furthermore, it also includes precision processing after anode forming: using high-precision CNC machine tools to perform surface grinding, size correction and necessary channel processing on the heat-treated anode. During the grinding process, appropriate grinding wheels and grinding parameters are used to ensure the flatness and smoothness of the anode surface; during the size correction process, precision measuring tools are used to accurately measure and adjust the size of the anode to ensure the precise fit between the anode and the electrolytic cell; during the channel processing, drilling, reaming and other processing operations are performed according to design requirements to ensure the position and dimensional accuracy of the channel; after precision processing, the surface flatness and dimensional accuracy of the anode meet the design requirements, and the fit with the electrolytic cell is good, while optimizing the heat dissipation performance of the anode.

[0026] Furthermore, it also includes quality inspection and control, specifically antioxidant performance test: after constant temperature oxidation in air at 850±10°C for 20 hours, the mass loss of the anode is controlled within the range of 1.2±0.1%, ensuring that the anode has good antioxidant performance; resistivity test: the resistivity of the anode is measured using a resistivity tester to ensure that the resistivity is lower than 16±1μΩ·m, meeting the conductivity requirements; mechanical strength test: the flexural strength of the anode is measured using a three-point bending test method to ensure that the flexural strength is not lower than 38±2MPa, meeting the mechanical strength requirements; microstructure analysis: the microstructure of the anode is analyzed by scanning electron microscopy and X-ray diffraction analysis to confirm that the degree of graphitization is high and the grains are arranged in order; corrosion resistance test: after immersion in an electrolyte solution containing fluoride ions for 48 hours, the mass loss of the anode is controlled within the range of 0.4±0.05%, ensuring that the anode has good corrosion resistance; various performance indicators of the anode meet the design requirements and show good comprehensive performance.

[0027] Furthermore, it also includes the storage and management of raw materials, specifically setting up a dry and dust-free environment in the raw material warehouse, controlling the temperature to 22±2°C and the humidity to 50±5%. High-purity petroleum coke and high-quality needle coke are stored in partitions, and the storage environment is regularly checked and recorded. Quality inspection is carried out before the raw materials are put into storage to ensure that the quality of the raw materials meets the requirements; the raw materials maintain a good quality state during the storage process to avoid moisture, oxidation or contamination.

[0028] Furthermore, the method also includes homogenizing the paste, specifically, after adding the antioxidant system, mixing the paste with a high-speed mixer. The mixing time is 30±2 minutes, and the rotation speed is controlled within the range of 1500±50 rpm. A ball mill is then used for further homogenization, and the processing time is 2±0.1 hours. By precisely controlling parameters such as mixing time and rotation speed, the antioxidant is ensured to be evenly distributed in the paste; after the homogenization treatment, the antioxidant of the paste is evenly distributed, providing a high-quality paste foundation for subsequent processes.

[0029] Furthermore, it also includes the control of temperature gradient, specifically, in the heat treatment process, by accurately controlling parameters such as heating rate, holding time and atmosphere composition, to form a suitable temperature gradient. In the first stage of heating, a slower heating rate and a longer holding time are used to promote uniform graphitization of the internal structure of the anode. In the second stage of heating, a faster heating rate and an appropriate holding time are used to ensure that the anode is fully graphitized at high temperature and optimize the graphite structure. At the same time, by real-time monitoring of the temperature change curve and the atmosphere composition change curve, the temperature gradient is accurately controlled; the internal structure of the anode is uniformly graphitized, the volatile matter is effectively eliminated, and the cracks or deformation caused by too fast temperature changes are avoided.

[0030] Furthermore, it also includes the control of the thickness of the protective layer, specifically, in the process of chemical vapor deposition, by accurately controlling the flow rate of silane gas and silicon carbide precursor gas, deposition time and temperature and other parameters to ensure the uniformity and thickness of the protective layer. After many tests and optimizations, the optimal range of deposition parameters is determined. During the deposition process, the changes in the thickness of the protective layer are monitored in real time and adjusted as needed. At the same time, the thickness of the formed protective layer is measured and the uniformity is checked to ensure that the thickness of the protective layer meets the design requirements; the thickness of the formed protective layer is uniform and stable, and it has sufficient oxidation resistance and wear resistance, and does not affect the conductivity and mechanical strength of the anode.

[0031] Furthermore, it also includes the packaging and storage of finished anode products, specifically the proper packaging of finished anode products that have passed precision processing and quality inspection. The packaging materials are special packaging materials that are moisture-proof, dust-proof, and anti-static to ensure that the finished anode products are not contaminated, damaged, or oxidized during transportation and storage. Labeling and recording are carried out during the packaging process to ensure the traceability of the finished anode products. During storage, the temperature of the storage environment is controlled at 22±2°C and the humidity is controlled at 50±5%, and the storage environment is checked and recorded regularly. At the same time, an inventory management system and an outbound inspection system for finished anode products are established to ensure that the finished anode products maintain stable performance and quality during long-term storage; the finished anode products maintain good quality during transportation and storage, meeting the requirements of long-term storage and use.

[0032] Finally, it should be noted that the basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only an example and does not constitute a limitation of this specification. Although it is not explicitly stated here, those skilled in the art may make various modifications, improvements and corrections to this specification. Such modifications, improvements and corrections are suggested in this specification, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this specification. At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "one embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "one embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined. In addition, unless explicitly stated in the claims, the order of processing elements and sequences described in this specification, the use of alphanumeric characters, or the use of other names are not used to limit the order of the processes and methods of this specification.

Claims

1. A process for producing a prebaked anode with high oxidation resistance, characterized in that: The following steps are involved: S1. Raw material selection and pretreatment: high-purity petroleum coke with an ash content of no more than 0.3% by weight and a sulfur content of no more than 0.15% by weight is selected as the main raw material, and at least 15% by weight of high-quality needle coke is added; before mixing, the petroleum coke and needle coke are subjected to ultrasonic cleaning treatment, and then dried to remove impurities and moisture attached to the surface; S2. Additive mixing and paste preparation: Add specific proportions of calcium silicate, aluminum oxide powder and rare earth oxide to the anode paste as an antioxidant system, wherein the amount of calcium silicate added is 1.5%-2.5% of the total mass of the paste, the amount of aluminum oxide added is 3%-4.5%, and the amount of rare earth oxide added is 0.15%-0.45%; the rare earth oxide is previously subjected to nano-grinding treatment to improve its dispersion uniformity and chemical activity in the paste.

2. A process for producing a prebaked anode with high oxidation resistance according to claim 1, characterized in that: The following heat treatment steps are also included: S3, two-stage heat treatment and precise atmosphere control: The first stage: in an inert gas atmosphere, heating to 400°C-500°C at a heating rate not exceeding 80°C / h and keeping the temperature for 2.5 hours to achieve effective removal of volatiles and preliminary graphitization; The second stage: under the same inert gas protection, heat to 1200°C-1300°C at a heating rate of 60°C-120°C / h and keep warm for 8-9 hours; in the high temperature stage, introduce a small amount of hydrogen to promote the deep optimization of the graphite structure and the improvement of crystallinity.

3. A process for producing a prebaked anode with high oxidation resistance according to claim 1 or 2, characterized in that: The following surface modification steps are also included: S4. Formation of composite siliconization protective layer: Using chemical vapor deposition technology, in an inert gas atmosphere, the anode is heated to 1000°C-1100°C, and silane gas and silicon carbide precursor gas are introduced to perform siliconization and silicon carbide co-deposition treatment for 2 hours, thereby forming a composite protective layer composed of silicide and silicon carbide on the surface of the anode, which significantly enhances the oxidation resistance and wear resistance of the anode.

4. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 1 to 3, characterized in that: The following steps are also included: S5. Precision machining after anode forming: Precision machining of the heat-treated anode, including but not limited to surface grinding, size correction and necessary hole machining, to ensure the precise fit between the anode and the electrolytic cell, while optimizing the heat dissipation performance of the anode.

5. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 1 to 4, characterized in that: The following quality inspection and control steps are also included: a Anti-oxidation performance test: using the accelerated oxidation test method, that is, constant temperature oxidation in air at 850°C for 20 hours, the anode mass loss does not exceed 1.5%; b. Resistivity test: Ensure that the resistivity of the anode is less than 18μΩ·m; c Mechanical strength test: The flexural strength of the anode shall not be less than 35MPa; d Microstructure analysis: Scanning electron microscopy and X-ray diffraction analysis confirmed that the degree of graphitization was high and the grains were arranged in an orderly manner; e Corrosion resistance test: After immersion in an electrolyte solution containing fluoride ions for 48 hours, the anode mass loss does not exceed 0.5%.

6. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 1 to 5, characterized in that: It also includes the storage and management steps of raw materials: Before raw material selection and pretreatment, high-purity petroleum coke and high-quality needle coke are strictly stored and managed to ensure that the storage environment is dry and dust-free, and the temperature and humidity are controlled within an appropriate range to prevent the raw materials from moisture, oxidation or contamination.

7. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 1 to 6, characterized in that: The additive mixing and paste preparation steps also include a homogenization process of the paste: After adding the antioxidant system, the paste is fully mixed and homogenized using equipment such as a high-speed mixer or a ball mill to ensure that the antioxidant is evenly distributed in the paste to improve the overall antioxidant performance of the anode.

8. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 2 to 7, characterized in that: The two-stage heat treatment and atmosphere precise control step also includes the control of temperature gradient: During the heating process, a suitable temperature gradient is formed by precisely controlling the heating rate and holding time to promote uniform graphitization of the internal structure of the anode and effective removal of volatiles, while avoiding cracks or deformation of the anode due to rapid temperature changes.

9. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 3 to 8, characterized in that: The step of forming the composite siliconized protective layer also includes controlling the thickness of the protective layer: By adjusting parameters such as gas flow, deposition time and temperature during chemical vapor deposition, the thickness of the protective layer formed by siliconization and silicon carbide co-deposition treatment is precisely controlled to ensure that the protective layer has sufficient oxidation resistance and wear resistance without affecting the conductivity and mechanical strength of the anode.

10. A process for producing a prebaked anode with high oxidation resistance according to any one of claims 4 to 9, characterized in that: It also includes the packaging and storage steps of the finished anode products: The finished anode products that have undergone precision processing and passed quality inspection are properly packaged to prevent contamination, damage or oxidation during transportation and storage; at the same time, the temperature and humidity of the storage environment are controlled to ensure that the finished anode products maintain stable performance during long-term storage.

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