Method for aluminum step-by-step electrolysis by using silicon carbide electrode

Abstract

The invention discloses a method for applying a silicon carbide electrode to step-by-step electrolysis of aluminum, belongs to the technical field of electrolytic aluminum, and aims to solve the problems that a carbon anode material adopted by the conventional electrolytic aluminum is easy to corrode in a high-temperature melting environment, the anode generates oxygen reaction loss, the service life is short, frequent replacement is needed, and the production cost is increased. Through combination of a step-by-step electrolysis process and a silicon carbide electrode, the production efficiency of electrolytic aluminum is improved, local concentration fluctuation is easily caused by direct feeding of aluminum oxide into an electrolytic bath in a traditional process, uniform mixing of aluminum oxide and cryolite is realized in advance through an independent dissolving tank, and under the precise temperature control of 950-1100 DEG C and the stirring effect of 30-50 r / min, the aluminum oxide and cryolite are mixed uniformly, so that the production efficiency of the electrolytic aluminum is improved. The aluminum oxide is completely converted into conductive melt, reaction fluctuation caused by uneven concentration is eliminated from the source, aluminum ions in an electrolytic bath are more continuously and uniformly separated out through homogenization treatment, the voltage of electrolytic aluminum is greatly reduced, the stable aluminum electrolysis process between 2.0 volts and 4.2 volts is achieved, and the energy utilization efficiency of the electrolytic aluminum is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis technology, and more specifically, to a method for using silicon carbide electrodes in stepwise aluminum electrolysis. Background Technology

[0002] Electrolytic aluminum production is the main method for producing metallic aluminum in industry. Its core principle is to generate aluminum by electrolyzing a molten mixture of alumina and cryolite (cryolite is used as a flux to lower the melting point of alumina) and causing an electrochemical reaction at the electrode.

[0003] However, existing electrolytic aluminum electrodes use carbon electrodes for the anode and graphite materials for the cathode. In particular, the anode is easily corroded and worn in the high-temperature molten environment, resulting in a short service life and frequent replacement, which increases production costs.

[0004] However, in the current electrolysis process system, carbon and graphite electrodes are still the mainstream choices for electrode materials. Under the extreme environment of high temperature melting, the chemical stability and structural integrity of these carbon and graphite electrodes face severe challenges. High temperature will accelerate the chemical reaction between carbon and graphite electrodes and active components generated during electrolysis, resulting in continuous corrosion of the electrode surface, gradually forming irregular pits and cracks. In addition, the violent flow of molten material will have a mechanical scouring effect on the electrode, further aggravating the material loss.

[0005] Therefore, in order to solve such problems, we propose a method for stepwise electrolysis of aluminum using silicon carbide electrodes. Summary of the Invention

[0006] The purpose of this invention is to provide a method for stepwise electrolysis of aluminum using silicon carbide electrodes, aiming to solve the problems in the background art, where traditional electrolysis electrodes mostly use carbon anodes and graphite cathodes, which are easily corroded and worn in high-temperature molten environments, have short service life, require frequent replacement, and increase production costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for using a silicon carbide electrode in stepwise aluminum electrolysis, comprising the following implementation steps:

[0008] S1: Dissolution stage. In the dissolution tank, alumina is added to the cryolite melt at a mass ratio of 1:9. The temperature of the melt is maintained at 950-1100℃ by heating equipment. At the same time, the stirring device is started and the stirring speed is controlled at 30-50r / min to completely dissolve the alumina and convert it into a conductive melt, forming a uniform and stable mixture.

[0009] S2: In the electrolysis stage, the uniform mixture in the dissolution pool is fed into the electrolytic cell through the conveying component. The silicon carbide electrode is used as the anode and the graphite electrode is used as the cathode. Electrolysis is carried out under the conditions of electrolysis voltage of 2.0-4.2V and electrolysis temperature of 940-960℃.

[0010] S3: Circulation and replenishment. When the alumina concentration in the electrolytic cell drops to 2-3%, the cryolite melt in the electrolytic cell is pumped back to the dissolution tank using the conveying component. Alumina is then added back and the dissolution process is repeated, forming a cycle.

[0011] Furthermore, the dissolution stage in S1 includes the following implementation steps;

[0012] S11: Calculate the amount of alumina and cryolite to be used according to production needs, ensure that the mass ratio of the two is 1:9, and store them in a dry and clean raw material container;

[0013] S12: Add cryolite to the melting tank, start the heating equipment to heat the cryolite until the cryolite is completely melted to form a clear melt;

[0014] S13: After the cryolite melt has stabilized, slowly and evenly add alumina into the melt;

[0015] S14: Start the stirring device and adjust the stirring speed to 30-50 r / min. Observe the state of the melt during stirring to ensure that the alumina particles are evenly dispersed and gradually dissolved.

[0016] S15: After dissolution, maintain the melt temperature at 950-1100℃ and the stirring speed at 30-50r / min to keep the mixture in a uniform and stable state, ready for subsequent processing.

[0017] Furthermore, the electrolysis stage in S2 includes the following implementation steps;

[0018] S21: Using a conveying assembly, the mixture in a uniform and stable state in the dissolving tank is fed into the electrolytic cell at a set rate;

[0019] S22: Turn on the heating equipment of the electrolytic cell to preheat the mixture in the electrolytic cell and gradually adjust the temperature to the range of 940-960℃;

[0020] S23: After the temperature stabilizes, start the power supply, adjust the electrolysis voltage to 2.0-4.2V, and then carry out the electrolysis operation;

[0021] S24: After the electrolysis reaches the preset time, turn off the power supply, stop the electrolysis, and remove the electrolysis products.

[0022] Furthermore, the distance between the silicon carbide electrode and the graphite electrode in S2 is 15 cm.

[0023] Furthermore, the silicon carbide electrode surface in S2 is coated with an antioxidant coating.

[0024] Furthermore, the dissolving tank and the electrolytic cell respectively include a dissolving tank and an electrolytic tank. A feed pipe is provided on the upper side wall of the dissolving tank. The stirring device includes a rotary drive fixedly connected to the upper end of the dissolving tank. A rotating column is fixedly connected to the output end of the rotary drive. The lower end of the rotating column penetrates the inner top wall of the dissolving tank. Multiple stirring rods are uniformly fixedly connected to the side wall of the rotating column inside the dissolving tank. The silicon carbide electrode is installed inside the electrolytic tank. A discharge pipe is provided on the lower side wall of the electrolytic tank. A gas outlet pipe is provided on the upper side wall of the electrolytic tank. The conveying assembly is located on the upper side wall of the dissolving tank and the electrolytic tank.

[0025] Furthermore, the conveying assembly includes a pump body, with a first connecting pipe and a second connecting pipe respectively provided at both ends of the pump body. The end of the first connecting pipe away from the pump body penetrates the inner wall of the dissolving tank, and the end of the second connecting pipe away from the pump body penetrates the inner wall of the electrolysis tank.

[0026] Furthermore, the heating device in S is an electric heating tube, and the total power of the electric heating tube is not less than kW.

[0027] Furthermore, a concentration sensor is installed on the inner wall of the electrolysis tank.

[0028] Furthermore, the first connecting pipe and the second connecting pipe are respectively provided with heat insulation layers on the side walls outside the dissolving tank and the electrolysis tank.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. This invention proposes a method for stepwise electrolysis of aluminum using silicon carbide electrodes. By combining an innovative stepwise electrolysis process with silicon carbide electrodes, the stability and efficiency of electrolytic aluminum production are further improved. In traditional processes, directly adding alumina into the electrolytic cell can easily lead to local concentration fluctuations. However, this invention achieves uniform mixing of alumina and cryolite in advance through an independent dissolution tank. Under precise temperature control of 950-1100℃ and stirring at 30-50 r / min, the alumina is completely converted into a conductive melt, eliminating reaction fluctuations caused by uneven concentration from the source. This homogenization treatment makes the precipitation of aluminum ions in the electrolytic cell more continuous and uniform.

[0031] 2. The method for stepwise aluminum electrolysis using silicon carbide electrodes proposed in this invention, with silicon carbide electrodes as anodes and graphite electrodes as cathodes, is another core advantage of this invention. Silicon carbide material can effectively resist molten erosion and high-temperature oxidation in a high-temperature molten cryolite environment. Combined with a surface anti-oxidation coating, its service life can reach 3-4 times that of graphite electrodes. This not only reduces downtime losses caused by frequent electrode replacements but also lowers material costs. In addition, the automated circulation replenishment system realizes closed-loop circulation of molten liquid through the linkage of concentration sensors and conveying components, eliminating the need for frequent manual feeding. This simplifies the operation process and ensures the continuity of production, providing a practical and feasible technical solution for efficient and low-cost production in the aluminum electrolysis industry. Attached Figure Description

[0032] Figure 1 This is a three-dimensional schematic diagram of the dissolving tank in this invention;

[0033] Figure 2 This is a three-dimensional sectional view of the dissolving vessel in this invention;

[0034] Figure 3 This is a three-dimensional sectional view of the electrolytic vessel in this invention;

[0035] Figure 4 This is a three-dimensional schematic diagram of the conveying component in this invention.

[0036] Legend:

[0037] 1. Dissolving tank; 11. Feed pipe; 12. Rotary drive component; 13. Rotating column; 14. Stirring rod; 2. Electrolytic tank; 22. Discharge pipe; 23. Gas outlet pipe; 3. Electric heating element; 4. Pump body; 41. First connecting pipe; 42. Second connecting pipe. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] To address the issues raised by traditional electrolytic electrodes, which are primarily made of graphite and are prone to corrosion and wear in high-temperature molten environments, resulting in short service life, frequent replacements, and increased production costs, please refer to [link to relevant documentation]. Figures 1-4 .

[0040] A method for using a silicon carbide electrode in stepwise aluminum electrolysis includes the following steps:

[0041] S1: Dissolution stage. In the dissolution tank, alumina is added to the cryolite melt at a mass ratio of 1:9. The temperature of the melt is maintained at 950-1100℃ by heating equipment. At the same time, the stirring device is started and the stirring speed is controlled at 30-50r / min to completely dissolve the alumina and convert it into a conductive melt, forming a uniform and stable mixture.

[0042] Step 2: Electrolysis stage. The homogeneous mixture in the dissolution pool is fed into the electrolytic cell through the conveying component. The silicon carbide electrode is used as the anode and the graphite electrode is used as the cathode. Electrolysis is carried out under the conditions of electrolysis voltage of 2.0-4.2V and electrolysis temperature of 940-960℃.

[0043] Step 3: Circulation and replenishment. When the alumina concentration in the electrolytic cell drops to 2-3%, the cryolite melt in the electrolytic cell is pumped back to the dissolution tank using the conveying component. Alumina is then added back and the dissolution process is repeated to form a cycle.

[0044] Furthermore, the dissolution stage in step 1 includes the following implementation steps;

[0045] Step 11: Calculate the amount of alumina and cryolite to be used according to production needs, ensuring that the mass ratio of the two is 1:9, and store them in a dry and clean raw material container;

[0046] Step 12: Add cryolite to the melting tank and start the heating equipment to heat the cryolite until it is completely melted and forms a clear melt.

[0047] Step 13: After the cryolite melt has stabilized, slowly and evenly add alumina into the melt;

[0048] Step 14: Start the stirring device and adjust the stirring speed to 30-50 r / min. Observe the state of the melt during stirring to ensure that the alumina particles are evenly dispersed and gradually dissolved.

[0049] Step 15: After dissolution, maintain the melt temperature at 950-1100℃ and the stirring speed at 30-50 r / min to keep the mixture in a uniform and stable state, ready for subsequent processing.

[0050] Furthermore, the electrolysis stage in step 2 includes the following implementation steps;

[0051] Step 21: Using the conveying assembly, the mixture in a uniform and stable state in the dissolving tank is fed into the electrolytic cell at a set rate;

[0052] Step 22: Turn on the heating equipment of the electrolytic cell to preheat the mixture in the electrolytic cell, and gradually adjust the temperature to the range of 940-960℃;

[0053] Step 23: After the temperature stabilizes, turn on the power supply, adjust the electrolysis voltage to 2.0-4.2V, and then carry out the electrolysis operation;

[0054] Step 24: After the electrolysis reaches the preset time, turn off the power supply, stop the electrolysis, and remove the electrolysis product.

[0055] Example 1:

[0056] Dissolving tank: with a volume of 500L, the inner wall is made of high temperature resistant ceramic material, the electrolysis tank 2 has an internal electric heating tube (total power 20kW), and a stirring device is installed on the top (stirring rod diameter 30cm, material is high temperature resistant alloy).

[0057] Electrolytic cell: 1000L volume, with 6 sets of electrodes arranged in parallel inside (silicon carbide electrode as anode, graphite electrode as cathode), the electrode dimensions are 10cm long, 20cm wide, and 5cm thick, with a spacing of 15cm.

[0058] Circulation path: The melting tank and the electrolytic cell are connected by a first connecting pipe 41 and a second connecting pipe 42 made of high temperature resistant alloy. A solenoid valve (model DN65) and a pump body 4 (flow rate 20L / min) are installed on the pipeline.

[0059] Operating steps

[0060] Dissolution stage: Add 450kg of cryolite to the dissolution tank, heat to 1000℃ to melt it, then add 50kg of alumina (alumina to cryolite mass ratio 1:9), start the stirring device (stirring speed 30r / min), and continue stirring for 60 minutes until the alumina is completely dissolved, forming a uniform and stable conductive melt mixture.

[0061] Electrolysis stage: Open the solenoid valve on the pipeline, and send the mixture in the dissolving tank into the electrolytic cell through the first connecting pipe 41 via the pump body 4 (liquid level to 80% of the electrolytic cell volume), turn on the power, set the electrolysis voltage to 2.0V and the electrolysis temperature to 940℃, and carry out the electrolysis reaction.

[0062] Circulation replenishment: After 12 hours of electrolysis, the concentration sensor in the electrolytic cell detects that the alumina concentration has dropped to 2-3%. Pump 4 is started to pump the cryolite melt in the electrolytic cell back to the dissolution tank along the second connecting pipe 42 (flow rate 20L / min). When the liquid level in the electrolytic cell drops to 50% of its volume, pump 4 and the solenoid valve are turned off. 15kg of alumina is added to the dissolution tank, and the dissolution stage operation is repeated (temperature 1000℃, stirring speed 30r / min, stirring for 50 minutes). After the alumina is completely dissolved, the mixture is sent back to the electrolytic cell to continue electrolysis.

[0063] This embodiment operated continuously for 2000 hours, producing a total of 1100 kg of aluminum. During the electrolysis process, the molten liquid remained uniform throughout, with no localized concentration fluctuations. The silicon carbide electrode loss was 0.7 kg, far lower than the 3.2 kg loss of the graphite electrode under the same conditions. The energy consumption per unit of aluminum production was 13100 kWh / t, approximately 10% lower than that of traditional processes.

[0064] Example 2:

[0065] Dissolving tank: with a volume of 500L, the inner wall is made of high temperature resistant ceramic material, the electrolysis tank 2 has an internal electric heating tube (total power 20kW), and a stirring device is installed on the top (stirring rod diameter 30cm, material is high temperature resistant alloy).

[0066] Electrolytic cell: 1000L volume, with 6 sets of electrodes arranged in parallel inside (silicon carbide electrode as anode, graphite electrode as cathode), the electrode dimensions are 10cm long, 20cm wide, and 5cm thick, with a spacing of 15cm.

[0067] Circulation path: The melting tank and the electrolytic cell are connected by a first connecting pipe 41 and a second connecting pipe 42 made of high temperature resistant alloy. A solenoid valve (model DN65) and a pump body 4 (flow rate 20L / min) are installed on the pipeline.

[0068] Operating steps

[0069] Dissolution stage: Add 425 kg of cryolite to the dissolution tank, heat to 1050℃ to melt it, then add 50 kg of alumina (alumina to cryolite mass ratio 1:8.5), start the stirring device (stirring speed 40 r / min), and continue stirring for 55 minutes until the alumina is completely dissolved, forming a uniform and stable conductive melt mixture.

[0070] Electrolysis stage: Open the solenoid valve on the pipeline, and send the mixture in the dissolving pool into the electrolytic cell through the first connecting pipe 41 via the pump body 4 (liquid level to 80% of the electrolytic cell volume), turn on the power, set the electrolysis voltage to 3.0V and the electrolysis temperature to 950℃, and carry out the electrolysis reaction.

[0071] Circulation replenishment: After 12 hours of electrolysis, the concentration sensor in the electrolytic cell detects that the alumina concentration has dropped to 2-3%. Pump 4 is started to pump the molten liquid in the electrolytic cell back to the dissolution tank along the second connecting pipe 42 (flow rate 20L / min). When the liquid level in the electrolytic cell drops to 50% of its volume, pump 4 and the solenoid valve are turned off. 14kg of alumina is added to the dissolution tank, and the dissolution stage operation is repeated (temperature 1050℃, stirring speed 40r / min, stirring for 45 minutes). After the alumina is completely dissolved, the mixture is sent back to the electrolytic cell to continue electrolysis.

[0072] This embodiment operated continuously for 2000 hours, producing a total of 1150 kg of aluminum. The electrolytic reaction showed good stability, and the aluminum deposition rate was approximately 2% higher than in Example 1. The silicon carbide electrode loss was 0.8 kg, and the energy consumption per unit aluminum production was 13300 kWh / t, which was within a reasonable range.

[0073] Example 3:

[0074] Dissolving tank: with a volume of 500L, the inner wall is made of high temperature resistant ceramic material, the electrolysis tank 2 has an internal electric heating tube (total power 20kW), and a stirring device is installed on the top (stirring rod diameter 30cm, material is high temperature resistant alloy).

[0075] Electrolytic cell: 1000L volume, with 6 sets of electrodes arranged in parallel inside (silicon carbide electrode as anode, graphite electrode as cathode), the electrode dimensions are 10cm long, 20cm wide, and 5cm thick, with a spacing of 15cm.

[0076] Circulation path: The melting tank and the electrolytic cell are connected by a first connecting pipe 41 and a second connecting pipe 42 made of high temperature resistant alloy. A solenoid valve (model DN65) and a pump body 4 (flow rate 20L / min) are installed on the pipeline.

[0077] Operating steps

[0078] Dissolution stage: Add 400 kg of cryolite to the dissolution tank, heat to 1100℃ to melt it, then add 50 kg of alumina (alumina to cryolite mass ratio 1:8), start the stirring device (stirring speed 50 r / min), and continue stirring for 50 minutes until the alumina is completely dissolved, forming a uniform and stable conductive melt mixture.

[0079] Electrolysis stage: Open the solenoid valve on the pipeline, and send the mixture in the dissolving pool into the electrolytic cell through the first connecting pipe 41 via the pump body 4 (liquid level to 80% of the electrolytic cell volume), turn on the power, set the electrolysis voltage to 4.0V and the electrolysis temperature to 960℃, and carry out the electrolysis reaction.

[0080] Circulation replenishment: After 12 hours of electrolysis, the concentration sensor in the electrolytic cell detects that the alumina concentration has dropped to 2-3%. Pump 4 is started to pump the cryolite melt in the electrolytic cell back to the dissolution tank along the second connecting pipe 42 (flow rate 20L / min). When the liquid level in the electrolytic cell drops to 50% of the volume, pump 4 and the solenoid valve are turned off. 13kg of alumina is added to the dissolution tank, and the dissolution stage operation is repeated (temperature 1100℃, stirring speed 50r / min, stirring for 40 minutes). After the alumina is completely dissolved, the mixture is sent back to the electrolytic cell to continue electrolysis.

[0081] This embodiment operated continuously for 2000 hours, producing a total of 1200 kg of aluminum. The aluminum precipitation rate was the highest among the three embodiments, about 5% higher than that of Embodiment 1; the silicon carbide electrode loss was 0.9 kg, and the energy consumption per unit aluminum production was 13500 kWh / t, which was slightly higher than the previous two embodiments, but still lower than the traditional process, and the electrode life remained stable.

[0082] In summary, all three embodiments are based on the same device structure. By adjusting parameters such as the ratio of alumina to cryolite, dissolution temperature, stirring speed, electrolysis voltage, and electrolysis temperature, the stability and adjustability of the stepwise electrolysis method of the present invention were verified. The low ratio and low voltage scheme of Embodiment 1 focuses on energy consumption control, the high ratio and high voltage scheme of Embodiment 3 focuses on improving precipitation efficiency, and Embodiment 2 is an intermediate balance scheme. All three provide a reference for applications of different production scales.

[0083] This invention avoids the problem of uneven local concentration caused by directly feeding materials into the electrolytic cell in traditional processes. This pre-homogenization treatment ensures that the composition of the melt in the electrolytic cell remains stable, providing a balanced chemical environment for the electrolytic reaction. It effectively eliminates reaction fluctuations caused by concentration fluctuations, making the deposition process of aluminum ions on the electrode surface more continuous and uniform. Ultimately, it increases the aluminum deposition rate by 5-8%, significantly improving production efficiency and effectively reducing production energy consumption.

[0084] The use of silicon carbide electrodes as anodes significantly extends the service life of the electrodes. They possess excellent high-temperature resistance and corrosion resistance. In the high-temperature molten cryolite environment of electrolytic aluminum production, they can effectively resist the erosion of the molten liquid and high-temperature oxidation. Compared with traditional graphite electrodes, they have better chemical stability and physical strength, and their service life can be 3-4 times that of graphite electrodes. This not only reduces the frequency of electrode replacement and reduces production interruptions caused by downtime for electrode replacement, but also saves a lot of electrode material costs, significantly reducing production costs from a long-term operating perspective.

[0085] By simplifying the operation process and improving production continuity, the carefully designed circulation path enables automated circulation and replenishment of the molten liquid between the dissolution tank and the electrolytic cell. When the alumina concentration in the electrolytic cell drops to a set threshold, the molten liquid can be pumped back to the dissolution tank for alumina replenishment and redissolution. This reduces operational complexity, ensures continuous production, effectively increases the effective operating time of the equipment, and further guarantees stable output of production efficiency.

[0086] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0087] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for using a silicon carbide electrode in stepwise aluminum electrolysis, characterized in that, The implementation steps include the following: S1: Dissolution stage. In the dissolution tank, alumina is added to the cryolite melt at a mass ratio of 1:

9. The temperature of the melt is maintained at 950-1100℃ by heating equipment. At the same time, the stirring device is started and the stirring speed is controlled at 30-50r / min to completely dissolve the alumina and convert it into a conductive melt, forming a uniform and stable mixture. S2: In the electrolysis stage, the uniform mixture in the dissolution pool is fed into the electrolytic cell through the conveying component. The silicon carbide electrode is used as the anode and the graphite electrode is used as the cathode. Electrolysis is carried out under the conditions of electrolysis voltage of 2.0-4.2V and electrolysis temperature of 940-960℃. S3: Circulation and replenishment. When the alumina concentration in the electrolytic cell drops to 2-3%, the cryolite melt in the electrolytic cell is pumped back to the dissolution tank using the conveying component. Alumina is then added back and the dissolution process is repeated, forming a cycle.

2. The method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 1, characterized in that; The dissolution stage in S1 includes the following implementation steps; S11: Calculate the amount of alumina and cryolite to be used according to production needs, ensure that the mass ratio of the two is 1:9, and store them in a dry and clean raw material container; S12: Add cryolite to the melting tank, start the heating equipment to heat the cryolite until the cryolite is completely melted to form a clear melt; S13: After the cryolite melt has stabilized, slowly and evenly add alumina into the melt; S14: Start the stirring device and adjust the stirring speed to 30-50 r / min. Observe the state of the melt during stirring to ensure that the alumina particles are evenly dispersed and gradually dissolved. S15: After dissolution, maintain the melt temperature at 950-1100℃ and the stirring speed at 30-50r / min to keep the mixture in a uniform and stable state, ready for subsequent processing.

3. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 1, characterized in that; The electrolysis stage in S2 includes the following implementation steps; S21: Using a conveying assembly, the mixture in a uniform and stable state in the dissolving tank is fed into the electrolytic cell at a set rate; S22: Turn on the heating equipment of the electrolytic cell to preheat the mixture in the electrolytic cell and gradually adjust the temperature to the range of 940-960℃; S23: After the temperature stabilizes, start the power supply, adjust the electrolysis voltage to 2.0-4.2V, and then carry out the electrolysis operation; S24: After the electrolysis reaches the preset time, turn off the power supply, stop the electrolysis, and remove the electrolysis products.

4. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 1, characterized in that; The distance between the silicon carbide electrode and the graphite electrode in S2 is 15 cm.

5. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 2, characterized in that: The silicon carbide electrode in S2 is coated with an antioxidant coating.

6. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 1, characterized in that: The dissolving tank and the electrolytic cell respectively include a dissolving tank (1) and an electrolytic tank (2). The upper side wall of the dissolving tank (1) is provided with a feed pipe (11). The stirring device includes a rotating drive (12) fixedly connected to the upper end of the dissolving tank (1). The output end of the rotating drive (12) is fixedly connected with a rotating column (13). The lower end of the rotating column (13) penetrates the inner top wall of the dissolving tank (1). Multiple stirring rods (14) are uniformly fixedly connected to the side wall inside the dissolving tank (1) of the rotating column (13). The silicon carbide electrode is installed inside the electrolytic tank (2). The lower side wall of the electrolytic tank (2) is provided with a discharge pipe (22). The upper side wall of the electrolytic tank (2) is provided with a gas outlet pipe (23). The conveying assembly is located on the upper side wall of the dissolving tank (1) and the electrolytic tank (2).

7. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 2, characterized in that; The conveying assembly includes a pump body (4), and a first connecting pipe (41) and a second connecting pipe (42) are respectively provided at both ends of the pump body (4). The end of the first connecting pipe (41) away from the pump body (4) penetrates the inner wall of the dissolving tank (1), and the end of the second connecting pipe (42) away from the pump body (4) penetrates the inner wall of the electrolytic tank (2).

8. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 1, characterized in that: The heating device in S1 is an electric heating tube, and the total power of the electric heating tube is not less than 15kW.

9. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 4, characterized in that; A concentration sensor is installed on the inner wall of the electrolysis tank (2).

10. A method for using a silicon carbide electrode in stepwise aluminum electrolysis according to claim 5, characterized in that: The first connecting pipe (41) and the second connecting pipe (42) are respectively provided with heat insulation layers on the side walls outside the dissolving tank (1) and the electrolytic tank (2).

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