Preparation method of high-density anti-oxidation carbon anode suitable for aluminum electrolysis cell

Abstract

The invention relates to the technical field of aluminum electrolysis science, and particularly discloses a preparation method of a high-density anti-oxidation carbon anode suitable for an aluminum electrolysis cell, which comprises the following steps: taking calcined coke as a raw material, and taking the calcined coke of each size fraction for batching; crushing blocky asphalt, sieving to obtain powdery asphalt, and fully mixing a proper amount of powdery asphalt with the ingredients obtained in the step S1 to obtain a mixture; mixing and kneading a composite additive and the mixture obtained in the step S2, and uniformly mixing and kneading to obtain a viscous material; performing hot compression molding on the viscous material obtained in the step S3 to obtain a green anode; sintering the green anode in a high-temperature furnace, and cooling at room temperature to obtain a carbon anode; in the step S3, the composite additive is composed of B2O3 and AlF3, the carbon anode subjected to process optimization and optimal burdening is not prone to cracking, fine and evenly-distributed pores are formed after sintering, and the carbon structure layer is obvious. B2O3 in the composite additive enters the carbon anode in a liquid form at a high temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum electrolysis, and in particular relates to a method for preparing a high-density, oxidation-resistant carbon anode suitable for an aluminum electrolysis cell. Background Art

[0002] The aluminum electrolysis industry is a key sector supporting the modern industrial system. Its core lies in the production of metallic aluminum through the electrolysis of alumina. This process relies on carbon anodes as both a conductive material and a carrier for electrochemical reactions. However, due to the prolonged exposure of carbon anodes to high temperatures and a highly oxidizing environment, they are susceptible to reaction with oxygen in the electrolyte, resulting in slagging or cracking. Simultaneously, oxygen ions discharge on the carbon anodes, oxidizing them to produce CO and CO₂ gases, which consume the anode, leading to anode failure and severely impacting the efficiency and energy consumption of electrolytic aluminum production. Research has shown that slagging can cause current efficiency losses of up to 5% to 10%, while approximately 15% of the energy consumed per ton of aluminum produced is directly related to carbon anode performance. Therefore, improving the oxidation resistance of carbon anodes has become a key area of ​​technological innovation in the industry.

[0003] The oxidation resistance of a carbon anode refers to its ability to resist oxidation reactions in high-temperature or electrochemical environments. Traditional carbon anodes contain numerous pores, allowing oxygen and corrosive substances to easily penetrate. This results in insufficient oxidation resistance, impacting service life and electrolysis efficiency. Optimizing the preparation process and adding additives such as trace elements and rare earth compounds to the carbon anode have been shown to significantly influence its pore structure, reduce air permeability, and thus enhance the carbon anode's oxidation resistance. However, issues such as additive selection, dosage optimization, and corresponding preparation process improvements remain unresolved. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a high-density, oxidation-resistant carbon anode suitable for an aluminum electrolytic cell comprises the following steps:

[0007] S1. Using calcined coke as raw material, calcined coke of various particle sizes is used for batching;

[0008] S2. Crushing the block asphalt and sieving it into powdered asphalt, taking an appropriate amount and mixing it thoroughly with the ingredients obtained in step S1 to obtain a mixture;

[0009] S3, taking the composite additive and the mixture obtained in step S2 and kneading them until the mixture is uniformly kneaded to obtain a viscous material;

[0010] S4, hot-molding the viscous material obtained in step S3 to obtain a green anode;

[0011] S5, placing the green anode into a high-temperature furnace for sintering, and cooling to room temperature to obtain a carbon anode;

[0012] In the step S3, the composite additive consists of B2O3 and AlF3.

[0013] Preferably, in step S1, the calcined coke of each particle size is divided into coarse, medium, fine and powder, the average particle size of the coarse coke is 3-6 mm, the medium coke is 1-3 mm, the fine coke is 0.074-1 mm, and the powder is less than 0.074 mm.

[0014] Preferably, in step S1, the ratio of calcined coke of each particle size is coarse coke: medium coke: fine coke: powder = 26:31:9:34.

[0015] Preferably, in step S2, the mesh size of the powdered asphalt is 60 mesh.

[0016] Preferably, in step S2, the mass percentage of powdered asphalt in the mixture is 13-17%.

[0017] Preferably, in step S3, the particle sizes of B2O3 and AlF3 are both below 1 μm, and the mass of B2O3 and AlF3 accounts for 1 to 14% of the total mass of the calcined coke batch and powdered asphalt; and the B2O3 and AlF3 do not exceed 7% each.

[0018] Preferably, in step S3, the kneading parameters are dry mixing at 120° C. for 30 min and wet mixing at 160° C. for 30 min.

[0019] Preferably, in step S4, the temperature of the hot compression molding head is 105-130°C, the temperature of the mold box is 110-135°C, and the temperature of the bottom mold is 105-130°C.

[0020] Preferably, in step S4, the green anode forming pressure is 20-50 MPa, and the holding time is 45 minutes.

[0021] Preferably, in step S5, during sintering, the green anode is placed in a crucible, and metallurgical coke is filled around the crucible to completely cover the anode. The sintering temperature is 1000-1100° C., and the sintering time is 45 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The carbon anode, which is kneaded with the optimal ingredients and powdered asphalt as a binder, is not easy to crack. After sintering, the pores of the carbon anode become small and evenly distributed, the carbon structure is clearly layered, and the burn-out rate is low.

[0024] (2) During high-temperature sintering, the B2O3 in the composite additive liquefies and enters the interior of the carbon anode, blocking the pores. At the same time, AlF3 also forms a dense Al2O3 protective film on the surface of the carbon anode. The synergistic effect of each component improves the density of the carbon anode and prevents the corrosive gases and substances generated during the aluminum electrolysis process from penetrating into the interior of the carbon anode.

[0025] (3) In the present invention, F from the composite additive is easily inserted into the carbon layer, so that all valence bonds of the C atoms participate in the bonding, and the structure of the carbon crystal becomes more stable during the graphitization process, which is beneficial to improving the oxidation resistance of the carbon anode.

[0026] (4) During the sintering process of the carbon anode, part of Al2O3 enters the pores of the carbon anode along with the liquid B2O3 at high temperature. It reacts with B2O3 to generate a large number of Al4B2O9 nanoparticles, which further block the pores. This is beneficial to increasing the density and antioxidant properties of the carbon anode. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the ordered carbon layer structure of the carbon anode prepared in Example 2 of the present invention;

[0028] Figure 2 This is a schematic diagram of the internal pores of the carbon anode prepared in Example 2 of the present invention;

[0029] Figure 3 These are Raman spectra of the carbon anodes prepared in Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Example 1:

[0032] See also Figure 1-Figure 3 As shown, a method for preparing a high-density, oxidation-resistant carbon anode suitable for an aluminum electrolytic cell comprises the following steps:

[0033] Calcined coke ingredients (14.31 g of coarse coke, 17.07 g of medium coke, 4.95 g of fine coke, and 18.73 g of fine powder) were weighed according to the optimal ratio of calcined coke (coarse coke: medium coke: fine coke: powder = 26:31:9:34) and thoroughly mixed in a blender at a temperature of 110°C.

[0034] Weigh 9.94 g of sieved powdered asphalt as a binder (15.3% of the mixture by mass);

[0035] After the powdered asphalt and calcined coke are fully mixed at room temperature, they are kneaded at 110°C for 30 minutes;

[0036] The uniformly mixed viscous material was placed in a preheated mold, the temperature of the pressure head was maintained at 105-130°C, the temperature of the mold box was maintained at 110-135°C, and the temperature of the bottom mold was maintained at 105-130°C. The pressure was maintained at 20 MPa for 45 minutes to obtain a Φ50×20 mm green anode.

[0037] The raw anode is placed in a crucible, and after the metallurgical coke is completely filled, the temperature is raised to 1100°C in a high-temperature furnace and kept at this temperature for 45 minutes, and then cooled to room temperature along with the furnace temperature to obtain a carbon anode.

[0038] Example 2:

[0039] Calcined coke ingredients (14.31 g of coarse coke, 17.07 g of medium coke, 4.95 g of fine coke, and 18.73 g of fine powder) were weighed according to the optimal ratio of calcined coke (coarse coke: medium coke: fine coke: powder = 26:31:9:34) and thoroughly mixed in a blender at a temperature of 110°C.

[0040] Weigh 9.94 g of sieved powdered asphalt as a binder (15.3% of the mixture by mass), and weigh 4.55 g and 3.25 g of B2O3 and AlF3 nanoparticles as composite additives (5% and 7% of the total mass of the calcined coke batch and powdered asphalt, respectively);

[0041] After the powdered asphalt and calcined coke are fully mixed at room temperature, the composite additives are added to the mixture and kneaded at 110°C for 30 minutes. The uniformly kneaded viscous material is placed in a preheated mold, the pressure head temperature is maintained at 105-130°C, the mold box temperature is maintained at 110-135°C, and the bottom mold temperature is maintained at 105-130°C. The pressure is maintained at 20MPa for 45 minutes to obtain a Φ50×20mm green anode;

[0042] The raw anode is placed in a crucible, and after the metallurgical coke is completely buried, the crucible is heated to 1100°C in a high-temperature furnace and kept at this temperature for 45 minutes, and then cooled to room temperature along with the furnace temperature to obtain a carbon anode;

[0043] The internal structure of the carbon anode of this embodiment is orderly and has obvious layers.

[0044] Example 3:

[0045] Calcined coke ingredients (14.31 g of coarse coke, 17.07 g of medium coke, 4.95 g of fine coke, and 18.73 g of fine powder) were weighed according to the optimal ratio of calcined coke (coarse coke: medium coke: fine coke: powder = 26:31:9:34) and thoroughly mixed in a blender at a temperature of 110°C.

[0046] Weigh 9.94 g of sieved powdered asphalt as a binder (15.3% of the mass of the mixture) and 4.55 g of AlF3 nanoparticles as an additive (7% of the total mass of the calcined coke batch and powdered asphalt, respectively);

[0047] After the powdered pitch and calcined coke are fully mixed at room temperature, the additives are added to the mixture and kneaded at 110°C for 30 minutes. The uniformly kneaded viscous material is placed in a preheated mold, and the temperature of the pressure head, mold box and bottom mold are maintained at 105-130°C, 110-135°C and 105-130°C, respectively. The pressure is maintained at 20 MPa for 45 minutes to obtain a Φ50×20mm green anode.

[0048] The raw anode is placed in a crucible, and after the metallurgical coke is completely filled, the temperature is raised to 1100°C in a high-temperature furnace and kept at this temperature for 45 minutes, and then cooled to room temperature along with the furnace temperature to obtain a carbon anode.

[0049] Example 4:

[0050] Calcined coke ingredients (14.31 g of coarse coke, 17.07 g of medium coke, 4.95 g of fine coke, and 18.73 g of fine powder) were weighed according to the optimal ratio of calcined coke (coarse coke: medium coke: fine coke: powder = 26:31:9:34) and thoroughly mixed in a blender at a temperature of 110°C.

[0051] Weigh 9.94 g of sieved powdered asphalt as a binder (15.3% of the mass of the mixture) and 1.2 g of B2O3 nanoparticles as an additive (2% of the total mass of the calcined coke batch and powdered asphalt);

[0052] After the powdered asphalt and calcined coke are fully mixed at room temperature, the additives are added to the mixture and kneaded at 110°C for 30 minutes;

[0053] The uniformly mixed viscous material was placed in a preheated mold, the temperature of the pressure head was maintained at 105-130°C, the temperature of the mold box was maintained at 110-135°C, and the temperature of the bottom mold was maintained at 105-130°C. The pressure was maintained at 20 MPa for 45 minutes to obtain a Φ50×20 mm green anode.

[0054] The raw anode is placed in a crucible, and after the metallurgical coke is completely filled, the temperature is raised to 1000°C in a high-temperature furnace and kept at this temperature for 45 minutes, and then cooled to room temperature along with the furnace temperature to obtain a carbon anode.

[0055] Experimental example:

[0056] Raman spectroscopy was used to analyze the graphitization degree of the carbon anode. The two most obvious diffraction peaks in the Raman spectrum were at 1350 cm -1 D belt and 1580cm -1 The G band and D band characterize the defects and disorder in carbon materials, which mainly come from sp 2 Irregular vibration of bonds, G band characterizes sp 2 The ordered vibration of the bond reflects the orderliness and crystallinity of the graphite layer, and the intensity ratio of the two diffraction peaks (I D / I G ) is used to evaluate the degree of graphitization of carbon materials. The smaller the value, the higher the degree of graphitization.

[0057] An air permeability meter was used to test the gas permeability of the carbon anode. The Archimedes drainage method was used to determine the volume density and porosity of the carbon anode. The volume density was calculated as shown in formula (1), and the porosity was calculated as shown in formula (2).

[0058]

[0059] Where m1 represents the dry weight when weighing, m2 represents the suspended weight after the sample is immersed in water for 30 minutes, and m3 refers to the wet weight directly weighed after being taken out of the water. The units are all g.

[0060] Bulk density refers to the amount of substance in a certain volume. Bulk density depends on the size, shape and porosity of the sample particles.

[0061] The above test was carried out on Example 1, Example 2, Example 3 and Example 4, as shown in the following table:

[0062]

[0063] From the above, it can be seen that Example 2 has the best comprehensive performance, which verifies that the composite additive significantly optimizes the density and oxidation resistance of the carbon anode through synergistic effects (filling pores, forming a protective film, and improving the degree of graphitization).

[0064] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-density, anti-oxidation carbon anode suitable for aluminum electrolysis cells, characterized in that: The following steps are involved: S1. Using calcined coke as raw material, calcined coke of various particle sizes is used for batching; S2. Crushing the block asphalt and sieving it into powdered asphalt, taking an appropriate amount and mixing it thoroughly with the ingredients obtained in step S1 to obtain a mixture; S3, taking the composite additive and the mixture obtained in step S2 and kneading them until the mixture is uniformly kneaded to obtain a viscous material; S4, hot-molding the viscous material obtained in step S3 to obtain a green anode; S5, placing the green anode into a high-temperature furnace for sintering, and cooling to room temperature to obtain a carbon anode; In the step S3, the composite additive consists of B2O3 and AlF3.

2. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S1, the calcined coke of each particle size is divided into coarse, medium, fine and powder. The average particle size of the coarse coke is 3-6 mm, the medium coke is 1-3 mm, the fine coke is 0.074-1 mm, and the powder is less than 0.074 mm.

3. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S1, the ratio of calcined coke of each particle size is coarse coke: medium coke: fine coke: powder = 26:31:9:

34.

4. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In the step S2, the mesh size of the powdered asphalt is 60 mesh.

5. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S2, the mass percentage of powdered asphalt in the mixture is 13-17%.

6. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S3, the particle sizes of B2O3 and AlF3 are both below 1 μm, and the mass of the B2O3 and AlF3 accounts for 1 to 14% of the total mass of the calcined coke batch and powdered asphalt; the B2O3 and AlF3 do not exceed 7% respectively.

7. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S3, the kneading parameters are dry mixing at 120° C. for 30 minutes and wet mixing at 160° C. for 30 minutes.

8. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S4, the temperature of the hot compression molding head is 105-130°C, the temperature of the mold box is 110-135°C, and the temperature of the bottom mold is 105-130°C.

9. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S4, the green anode forming pressure is 20-50 MPa, and the holding time is 45 minutes.

10. The method for preparing a high-density, oxidation-resistant carbon anode suitable for aluminum electrolysis cells according to claim 1, characterized in that: In step S5, during sintering, the green anode is placed in a crucible, and metallurgical coke is filled around the crucible to completely cover the anode. The sintering temperature is 1000-1100° C., and the sintering time is 45 minutes.

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