Covering material of carbon anode for prebaked anode aluminum electrolysis production and use mode of covering material

Abstract

The invention relates to the technical field of aluminum electrolysis production, in particular to a carbon anode covering material for prebaked anode aluminum electrolysis production and a use mode of the carbon anode covering material. The chemical properties of the alumina aerosol and the alumina fiber blanket are very stable, the alumina aerosol and the alumina fiber blanket do not react with a carbon anode or an electrolyte in a high-temperature environment of an electrolytic cell, oxygen can be continuously blocked, and the loss of the carbon anode is reduced; the heat conductivity coefficient of the alumina fiber blanket is obviously lower than that of a traditional crusting covering material, the alumina aerosol and the alumina fiber blanket are free of crusting phenomena, the pole changing operation time is shortened, and the labor and mechanical cost is reduced; the main material bodies of the alumina aerosol and the alumina fiber blanket are high-purity alumina and do not contain volatile harmful components.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis production technology, specifically to the covering material for carbon anodes used in prebaked anode aluminum electrolysis production and its application method. Background Technology

[0002] In the electrolytic production of prebaked anode aluminum, the carbon anode is the key electrode for the electrolytic reaction. The surface of the carbon anode needs to be covered with a mixture of electrolyte and alumina. The main component of the electrolyte is cryolite. The purpose of covering the surface of the carbon anode with the mixture of electrolyte and alumina is to achieve two core functions: first, to prevent direct contact between air, especially oxygen, and the carbon anode, thus avoiding the carbon anode from being damaged due to excessive oxidation; and second, to utilize the low thermal conductivity of the mixture of electrolyte and alumina to form an insulation layer, reducing the loss of heat from the electrolytic cell to the outside and maintaining the high-temperature environment of 900℃-1000℃ required for the electrolytic reaction.

[0003] However, traditional covering materials will form a hard crust due to high-temperature sintering during long-term use. Although the crust can enhance the heat preservation and anti-oxidation effect for a certain period of time, it needs to be mechanically crushed or manually cleaned during the electrode replacement operation of the electrolytic cell. This not only increases the labor intensity and time cost of the electrode replacement operation, but may also affect the stability of the electrolytic reaction due to the crust fragments mixed into the electrolyte, and may even cause damage to the carbon anode surface.

[0004] Therefore, developing an alternative material that can maintain anti-oxidation and heat preservation properties while avoiding crust formation and facilitating electrode replacement is of great significance for improving aluminum electrolysis production efficiency and reducing energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a covering material for carbon anodes used in the production of prebaked aluminum electrolysis anodes, comprising alumina aerosol. The alumina aerosol uses α-alumina powder with a particle size of 5μm-50μm as the dispersed phase and an inert gas, specifically nitrogen or argon, as the dispersion medium. The alumina powder has a purity ≥99.5%, and the alumina mass concentration in the dispersed phase is 10 g / m³. 3 -50g / m 3 .

[0006] The method for using the alumina aerosol of the present invention includes the following steps: S1. Pretreatment: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2. Equipment preparation: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3. Covering Operation: Aim the spray nozzle of the sprayer at the surface of the carbon anode and move it at a constant speed at a distance of 30cm-50cm from the surface of the carbon anode to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode; S4. Replenish Covering: Every 24-48 hours after use, spray alumina aerosol onto the carbon anode according to steps S1-S3 to maintain the integrity of the covering layer.

[0007] Furthermore, in step S3, the aerosol coverage at the edge of the carbon anode in contact with the electrolyte is thickened to 1mm-3mm.

[0008] In addition to alumina aerosol, the covering material for the carbon anode used in the prebaked anode aluminum electrolysis production of the present invention can also be alumina fiber blanket. The alumina fiber blanket is a flexible blanket-like material made of continuous interwoven alumina fibers with a diameter of 5μm-20μm, a length of 10mm-50mm, a purity of ≥99.5%, a blanket thickness of 5mm-20mm, and a porosity of 80%-95%.

[0009] The method of using the alumina fiber blanket of the present invention includes the following steps: S1': Cutting and Adaptation: Cut the alumina fiber blanket to a shape slightly larger than the anode surface according to the diameter and height of the carbon anode, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S2': Laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring that there are no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface; S3': Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S4': Removal of electrode: When changing electrodes, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused.

[0010] In addition to using alumina aerosol and alumina fiber blanket alone, this invention can also be used in combination. The method of using alumina aerosol and alumina fiber blanket in combination includes the following steps: S1”. Pretreatment before alumina aerosol spraying: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2”. Preparation of alumina aerosol spraying equipment: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3”. Alumina aerosol spraying and covering operation: Aim the sprayer nozzle at the carbon anode surface and move it at a constant speed at a distance of 30cm-50cm from the carbon anode surface to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode, and the aerosol coverage in the edge area where the carbon anode contacts the electrolyte is thickened to 1mm-3mm. S4”. Wait for the alumina aerosol to adhere stably: After completing step S3, wait 5-10 minutes to allow the alumina aerosol to adhere stably to the carbon anode. S5”: Alumina fiber blanket cutting and fitting: Based on the diameter and height of the carbon anode after completing step S4, cut the alumina fiber blanket to a shape slightly larger than the anode surface, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S6”: Alumina fiber blanket laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface. S7”: Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S8”: Removal of electrode: When changing the electrode, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused.

[0011] The beneficial effects of this invention are: More stable anti-oxidation performance: Both alumina aerosol and alumina fiber blanket have very stable chemical properties. Alumina aerosol and alumina fiber blanket do not react with carbon anode or electrolyte in the high-temperature environment of the electrolytic cell, and can continuously block oxygen, reducing carbon anode loss rate by 5%-10%; Superior thermal insulation: The thermal conductivity of alumina fiber blanket is significantly lower than that of traditional crust covering materials, which can reduce heat loss in the electrolytic cell by 8%-15% and indirectly reduce electrolysis energy consumption. Improved efficiency of electrode replacement: There is no crust formation in alumina aerosol and alumina fiber blanket. Alumina aerosol dissipates naturally with the airflow or is collected by negative pressure. Alumina fiber blanket can be directly peeled off, reducing electrode replacement time by 30%-50% and reducing labor and machinery costs. Better environmental performance: The main material of alumina aerosol and alumina fiber blanket is high-purity alumina, with no volatile harmful components. The fiber blanket can be reused, with a general service life of ≥5 times, reducing the amount of solid waste generated. Detailed Implementation

[0012] Example 1: The covering material for the prebaked anode carbon anode used in aluminum electrolysis production of the present invention includes alumina aerosol. The alumina aerosol uses α-alumina powder with a particle size of 5μm-50μm as the dispersed phase and an inert gas as the dispersion medium, wherein the inert gas is nitrogen or argon; the alumina powder purity is ≥99.5%, and the alumina mass concentration in the dispersed phase is 10g / m³. 3 -50g / m 3 The purity of alumina powder is ≥99.5% to avoid introducing impurities that could affect the quality of aluminum products.

[0013] The method for using the alumina aerosol of the present invention includes the following steps: S1. Pretreatment: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2. Equipment preparation: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3. Covering Operation: Aim the spray nozzle of the sprayer at the surface of the carbon anode and move it at a constant speed at a distance of 30cm-50cm from the surface of the carbon anode to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode, and the aerosol coverage in the edge area where the carbon anode contacts the electrolyte is thickened to 1mm-3mm. S4. Replenish Covering: Every 24-48 hours after use, spray alumina aerosol onto the carbon anode according to steps S1-S3 to maintain the integrity of the covering layer.

[0014] Alumina aerosol has good fluidity and good diffusion in the sol state, and can be uniformly attached to the surface of carbon anode and the surrounding area of ​​electrolytic cell.

[0015] Alumina aerosol has good high-temperature resistance; α-alumina has a melting point as high as 2050℃ and can withstand the high-temperature environment of the electrolytic cell without decomposing or melting.

[0016] Alumina aerosol has good anti-oxidation properties. After covering, it forms a dense gas-solid mixed barrier layer, which isolates oxygen from contact with the carbon anode.

[0017] Alumina aerosol does not form a crust, there is no tendency for the dispersed phase particles to sinter, and it does not form a hard crust with long-term use.

[0018] The alumina aerosol of this invention was used in a 400kA prebaked anode electrolytic cell. α-alumina powder with a particle size of 20μm was used, and nitrogen was used as the dispersion medium to prepare an aerosol with a concentration of 30g / m³. The aerosol was sprayed onto the surface of a newly installed carbon anode (1.5m in diameter) using a high-pressure sprayer to form a 1mm thick coating. It was used continuously for 30 days, with re-coating every 36 hours during this period.

[0019] The results showed that carbon anodizing loss was reduced by 7% compared to traditional covering materials, and the surface temperature of the electrolytic cell was reduced by 12°C. When changing electrodes, only residual aerosol particles need to be collected through a negative pressure device, and the cleaning time was shortened from the traditional 40 minutes to 15 minutes.

[0020] Example 2: The covering material for the carbon anode used in the prebaked anode aluminum electrolysis production of the present invention includes an alumina fiber blanket. The alumina fiber blanket is a flexible blanket-like material made of continuous interwoven alumina fibers. The alumina fibers have a diameter of 5μm-20μm, a length of 10mm-50mm, a purity of ≥99.5%, a thickness of 5mm-20mm, and a porosity of 80%-95%.

[0021] The method of using the alumina fiber blanket of the present invention includes the following steps: S1': Cutting and Adaptation: Cut the alumina fiber blanket to a shape slightly larger than the anode surface according to the diameter and height of the carbon anode, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S2': Laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring that there are no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface; S3': Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S4': Removal during electrode replacement: When replacing the electrode, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused. The reusable alumina fiber blanket needs to be cleaned of the electrolyte dust adhering to its surface.

[0022] Alumina fiber blankets are flexible and can be cut and laid according to the shape of carbon anodes, closely adhering to the surface. Alumina fiber blankets have good thermal insulation properties. Their high porosity structure forms an air insulation layer with a thermal conductivity of ≤0.1W / (m·K), which is superior to traditional covering materials.

[0023] Alumina fiber blankets have good high-temperature resistance, with a long-term operating temperature of ≥1200℃, meeting the high-temperature requirements of electrolytic cells.

[0024] Alumina fiber blankets are easy to remove, with no sintering or crusting. They can be directly peeled off or rolled up as a whole when changing electrodes, leaving no residue.

[0025] The alumina fiber blanket of this invention was used in a 400kA prebaked anode electrolytic cell. The alumina fiber blanket, 10mm thick and with a porosity of 90%, was cut into circles with a diameter of 1.6m and covered the carbon anode and a 5cm edge area. It was laid on the surface of the carbon anode in the 400kA electrolytic cell, and the edges were fixed with ceramic nails. After 30 days of continuous use, the fiber blanket showed no damage or sintering.

[0026] Tests showed that the heat loss of the electrolytic cell was reduced by 10%, and the carbon anode loss was reduced by 6%; the fiber blanket was directly peeled off during electrode replacement, and the cleaning time was shortened to 10 minutes; the alumina fiber blanket can be reused after cleaning.

[0027] Example 3: The combined use of the alumina aerosol and alumina fiber blanket of the present invention includes the following steps: S1”. Pretreatment before alumina aerosol spraying: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2”. Preparation of alumina aerosol spraying equipment: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3”. Alumina aerosol spraying and covering operation: Aim the sprayer nozzle at the carbon anode surface and move it at a constant speed at a distance of 30cm-50cm from the carbon anode surface to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode, and the aerosol coverage in the edge area where the carbon anode contacts the electrolyte is thickened to 1mm-3mm. S4”. Wait for the alumina aerosol to adhere stably: After completing step S3, wait 5-10 minutes to allow the alumina aerosol to adhere stably to the carbon anode. S5”: Alumina fiber blanket cutting and fitting: Based on the diameter and height of the carbon anode after completing step S4, cut the alumina fiber blanket to a shape slightly larger than the anode surface, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S6”: Alumina fiber blanket laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface. S7”: Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S8”: Removal of electrode: When changing the electrode, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused.

[0028] In a 400kA electrolytic cell, the alumina aerosol and alumina fiber blanket of the present invention were used in combination. First, a 0.8mm thick alumina aerosol was sprayed, with the parameters of the alumina aerosol being the same as in Example 1. Then, an 8mm thick alumina aerosol was laid, with the parameters of the alumina aerosol being the same as in Example 2.

[0029] The results showed that carbon anode loss was reduced by 9%, heat loss was reduced by 14%, and the anode replacement and cleaning time was shortened to 12 minutes, resulting in the best overall benefits.

[0030] The alumina aerosol and alumina fiber blanket of the present invention can effectively replace traditional covering materials, and perform excellently in terms of anti-oxidation, heat preservation and electrode replacement convenience, making them suitable for widespread application in aluminum electrolysis production.

Claims

1. A covering material for a carbon anode used in the electrolytic production of prebaked aluminum anodes, characterized in that: This includes alumina aerosol, in which α-alumina powder with a particle size of 5μm-50μm is used as the dispersed phase, and an inert gas, such as nitrogen or argon, is used as the dispersion medium; the alumina powder purity is ≥99.5%, and the alumina mass concentration in the dispersed phase is 10g / m³. 3 -50g / m 3 .

2. The method of using the covering material for a prebaked anode aluminum electrolysis production carbon anode according to claim 1, characterized in that: The steps include the following: S1. Pretreatment: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2. Equipment preparation: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3. Covering Operation: Aim the spray nozzle of the sprayer at the surface of the carbon anode and move it at a constant speed at a distance of 30cm-50cm from the surface of the carbon anode to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode; S4. Replenish Covering: Every 24-48 hours after use, spray alumina aerosol onto the carbon anode according to steps S1-S3 to maintain the integrity of the covering layer.

3. The method of using the covering material for a prebaked anode aluminum electrolytic production carbon anode according to claim 2, characterized in that: In step S3, the aerosol coverage at the edge of the carbon anode in contact with the electrolyte is thickened to 1mm-3mm.

4. A covering material for a carbon anode used in the electrolytic production of prebaked aluminum anodes, characterized in that: This includes alumina fiber blankets, which are flexible blanket-like materials made of continuous interwoven alumina fibers. The alumina fibers have a diameter of 5μm-20μm, a length of 10mm-50mm, a purity of ≥99.5%, a blanket thickness of 5mm-20mm, and a porosity of 80%-95%.

5. The method of using the covering material for a prebaked anode aluminum electrolysis production carbon anode according to claim 4, characterized in that: The steps include the following: S1': Cutting and Adaptation: Cut the alumina fiber blanket to a shape slightly larger than the anode surface according to the diameter and height of the carbon anode, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S2': Laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring that there are no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface; S3': Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S4': Removal of electrode: When changing electrodes, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused.

6. A covering material for a carbon anode used in the electrolytic production of prebaked aluminum anodes, characterized in that: It includes alumina aerosol and alumina fiber blanket. The alumina aerosol uses α-alumina powder with a particle size of 5μm-50μm as the dispersed phase and an inert gas as the dispersion medium, which is nitrogen or argon. The alumina powder has a purity of ≥99.5% and the mass concentration of alumina in the dispersed phase is 10g / m3-50g / m3. The alumina fiber blanket is a flexible blanket-like material made of continuous interwoven alumina fibers with a diameter of 5μm-20μm, a length of 10mm-50mm, a purity of ≥99.5%, a blanket thickness of 5mm-20mm, and a porosity of 80%-95%.

7. The method of using the covering material for a prebaked anode aluminum electrolysis production according to claim 6, characterized in that: The steps include the following: S1”. Pretreatment before alumina aerosol spraying: Before installing or replacing the carbon anode, clean the residual electrolyte or impurities on the surface of the carbon anode to ensure that the surface is dry and free of oil. S2”. Preparation of alumina aerosol spraying equipment: A high-pressure inert gas atomizing sprayer is used to mix α-alumina powder with inert gas according to the mass concentration of alumina in the dispersed phase to form a stable aerosol; S3”. Alumina aerosol spraying and covering operation: Aim the sprayer nozzle at the carbon anode surface and move it at a constant speed at a distance of 30cm-50cm from the carbon anode surface to make the aerosol evenly cover the surface and form a protective layer with a thickness of 0.5mm-2mm; the coverage area includes the top and side edges of the carbon anode, and the aerosol coverage in the edge area where the carbon anode contacts the electrolyte is thickened to 1mm-3mm. S4”. Wait for the alumina aerosol to adhere stably: After completing step S3, wait 5-10 minutes to allow the alumina aerosol to adhere stably to the carbon anode. S5”: Alumina fiber blanket cutting and fitting: Based on the diameter and height of the carbon anode after completing step S4, cut the alumina fiber blanket to a shape slightly larger than the anode surface, leaving a 5cm-10cm edge to cover the side wall of the electrolytic cell; S6”: Alumina fiber blanket laying operation: After the carbon anode is installed, lay the cut alumina fiber blanket flat on the surface of the carbon anode, ensuring no wrinkles or gaps; for the side edge of the anode, fold the edge of the alumina fiber blanket downwards by 5cm-10cm to fit the side surface. S7”: Fixing: If the alumina fiber blanket moves slightly due to the airflow in the electrolytic cell, use high-temperature resistant ceramic nails with a diameter of 2mm-3mm to lightly fix it at the edge of the alumina fiber blanket; S8”: Removal of electrode: When changing the electrode, directly peel off the entire alumina fiber blanket from the edge. If there are ceramic nails, remove them first. If the fiber blanket is not damaged after peeling, it can be reused.