Process for the purification of aluminium and its use in the production of high purity aluminium

Abstract

The application relates to the field of aluminum purification, in particular to a method for removing impurities from aluminum and application in preparation of high-purity aluminum. The method for removing impurities from aluminum comprises the following steps: after aluminum raw materials and aluminum boride alloy are melted in a vacuum environment, heat preservation is carried out, and after the heat preservation is completed, the obtained product is subjected to rotary crystallization to complete the removal of impurities from aluminum. The method for removing impurities from aluminum provided by the application combines the advantages of rotary crystallization, vacuum distillation and boride trapping technology, realizes one-step removal of Si, Fe, Zn, Mg, Ti and V impurities in aluminum by controlling and coordinating key process parameters of each technology, and simultaneously solves the problems of B introduction and pollution.

Description

Technical Field

[0001] This invention relates to the field of aluminum purification and preparation, and more particularly to a method for removing impurities from aluminum and its application in the preparation of high-purity aluminum. Background Technology

[0002] In recent years, with the rapid development of the electronics and aerospace industries, the demand for high-purity aluminum has increased year by year. However, the current annual output of high-purity aluminum is less than 200,000 tons, and the supply-demand contradiction is becoming increasingly prominent. The foundation for high-purity aluminum production is weak, and development has been slow. Although some progress has been made in high-purity aluminum production in recent years through technology introduction and process innovation, problems such as low production efficiency, high costs, and unclear purification mechanisms remain prominent, which have become bottlenecks restricting the development of the high-purity aluminum industry. In response to this situation, actively carrying out basic research on high-purity aluminum production and developing new processes and technologies with independent intellectual property rights are of great significance for optimizing the aluminum industry structure and enhancing the international competitiveness of the aluminum industry.

[0003] Segregation is a physical method that does not produce any toxic or harmful substances during production, meeting environmental protection requirements. However, the ability of segregation to remove impurities depends heavily on the equilibrium distribution coefficient, resulting in significant differences in removal efficiency. Furthermore, some impurities tend to accumulate in large quantities, leading to low purity in the final product. In addition, conventional segregation methods have a long processing time and typically require multiple operations to obtain a qualified product, resulting in low production capacity.

[0004] Rotary crystallization achieves uniform mixing in the molten system through rotation, reducing the solute boundary layer and optimizing the directional precipitation of impurities. Compared to zone melting and directional solidification, it offers higher production and separation efficiency and has attracted widespread attention in recent years. Rotary crystallization primarily relies on the equilibrium distribution coefficient (…). k 0 Purification can effectively remove ferrosilicon and other substances. k 0 Impurities much smaller than 1, but for k 0 Impurities such as zinc and magnesium with a concentration close to 1 are not effectively removed, while impurities such as Ti and V are less effective. k 0 Impurities greater than 1 will accumulate in large quantities in the crystallized product during the segregation process. Therefore, a single rotary crystallization process is difficult to remove Si, Fe, Zn, Mg, Ti, and V simultaneously and efficiently. Existing technologies can remove Si and Fe impurities from aluminum through segregation, and then remove Zn and Mg impurities through vacuum distillation. However, the removal of Ti and V requires the introduction of borides to form precipitates, which are then removed by settling and slag removal or filtration. This process introduces a large amount of B impurities, and each technology requires independent equipment and processes, resulting in high cost and low efficiency.

[0005] Therefore, how to simultaneously remove Si, Fe, Zn, Mg, Ti, and V impurities from aluminum, and solve the problems of boron introduction and contamination, are urgent issues that need to be addressed. Summary of the Invention

[0006] This invention provides a method for removing impurities from aluminum and its application in the preparation of high-purity aluminum. It aims to combine the advantages of rotational crystallization, vacuum distillation and boride trapping technologies, and achieve the one-step removal of Si, Fe, Zn, Mg, Ti and V impurities from aluminum by controlling and coordinating the key process parameters of each technology, while solving the problems of boron introduction and contamination.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for removing impurities from aluminum, comprising the following steps: The aluminum raw material and aluminum-boron alloy are melted in a vacuum environment and then held at a certain temperature. After the holding period, the resulting product is subjected to rotational crystallization to remove impurities from the aluminum.

[0008] Preferably, the impurities in the aluminum raw material include the equilibrium distribution coefficient. k 0 Impurities <0.2, 0.2≤ k 0 ≤1 impurities and k 0 Impurities greater than 1.

[0009] Preferably, the impurities in the aluminum raw material include Si, Fe, Zn, Mg, Ti, and V.

[0010] Preferably, in the aluminum raw material, the Si content is 5~15000ppm, more preferably 10~13000ppm, and even more preferably 300~11000ppm; the Fe content is 5~20000ppm, more preferably 10~15000ppm, and even more preferably 50~10000ppm; the Ti content is 1~3000ppm, more preferably 5~2500ppm, and even more preferably 50~1000ppm; the V content is 1~2000ppm, more preferably 5~1500ppm, and even more preferably 50~1000ppm; the Zn content is 1~4000ppm, more preferably 5~3000ppm, and even more preferably 50~1500ppm; and the Mg content is 1~2000ppm, more preferably 5~1500ppm, and even more preferably 25~1000ppm.

[0011] Preferably, in the aluminum-boron alloy, the content of B is 4 wt.% and the content of Al is 96 wt.%.

[0012] Preferably, in the melted system, the ratio of the total mass of V and Ti to the mass of B is 1:1 to 1:10, more preferably 1:2 to 1:8, and even more preferably 1:5.

[0013] Preferably, the pressure of the vacuum is ≤1 Pa, more preferably ≤0.1 Pa, and even more preferably ≤0.01 Pa.

[0014] Preferably, the melting temperature is 670~800℃, more preferably 700~780℃, and even more preferably 750℃.

[0015] Preferably, the heat preservation time is >20 min, more preferably 21~50 min, and even more preferably 30 min.

[0016] Preferably, the conditions for the rotational crystallization are: rotational speed of 0~300 rpm, more preferably 50~150 rpm, and even more preferably 60 rpm; temperature of 500~700℃, more preferably 480~600℃, and even more preferably 500℃; time of 5 min~90 min, more preferably 15~60 min, and even more preferably 30 min; atmosphere of air or inert gas, and gas flow rate of 20~200 L / min, more preferably 30~100 L / min, and even more preferably 50 L / min.

[0017] Preferably, the process further includes cooling the resulting product to room temperature after the rotational crystallization is completed.

[0018] A second aspect of the present invention also provides the application of the above-described method for removing impurities from aluminum in the preparation of high-purity aluminum.

[0019] Preferably, the aluminum raw material is refined aluminum with a purity of 4N or higher, and the aluminum is subjected to a single impurity removal process. That is, when the aluminum raw material is refined aluminum with a purity of 4N or higher, high-purity aluminum can be obtained by the above-mentioned aluminum impurity removal process.

[0020] Preferably, the aluminum raw material is aluminum with a purity lower than 4N, and the impurity removal method for the aluminum is repeated two or more times. That is, when the aluminum raw material is aluminum with a purity lower than 4N, repeating the above-mentioned aluminum impurity removal method can also yield high-purity aluminum.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for purifying aluminum, which utilizes a coupled process of aluminum-boron alloy addition, vacuum, and rotational crystallization to improve the purity of boron (B) and its equilibrium distribution coefficient. k 0Impurities with a value greater than 1, such as vanadium and titanium, can spontaneously react to form denser titanium vanadium borides, which then settle at the bottom of the molten aluminum system, thus achieving the removal of vanadium and titanium. Simultaneously, under vacuum conditions, the equilibrium distribution coefficient... k 0 The volatilization of volatile impurities (zinc (Zn) and magnesium (Mg)) with a value close to 1 provides the driving force, allowing them to evaporate from the melt using vacuum distillation, thus effectively removing impurities such as zinc and magnesium. Rotary crystallization enhances the reaction between boron and titanium vanadium through rotational stirring, promoting the formation and precipitation of borides and strengthening the removal of volatile impurities. Simultaneously, rotation lowers the solute concentration boundary layer at the solid-liquid interface at the crystallization front, promoting the removal of impurities with a k0 much less than 1, such as ferrosilicon. Furthermore, the boron introduced in this invention has an equilibrium distribution coefficient k0 of 0.2~0.4, which is not considered an impurity with an equilibrium distribution coefficient much less than 1. Since boron is not a volatile impurity under the conditions of this process, its removal does not rely on vacuum distillation. Instead, it segregates with the melt during rotary crystallization and is gradually discharged as crystals, thus effectively removing residual boron and preventing its enrichment in the final aluminum product. Finally, the material undergoes radial layer-by-layer growth on the surface of the crystallization axis, utilizing the solid-liquid phase transition to obtain aluminum products with higher purity. This achieves the goal of simultaneously removing multiple impurities such as Si, Fe, Zn, Mg, Ti, and V in one step, while preventing the introduction and contamination of B in the product. Attached Figure Description

[0022] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 This is a schematic diagram of the rotary crystallizer in Example 1. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 The method for removing impurities from aluminum is as follows: Figure 1 The rotary crystallizer shown includes the following steps: Electrolytic aluminum and aluminum-boron alloy (B content 4 wt.%, Al content 96 wt.%) were cleaned and air-dried, then placed in a graphite crucible in a crystallization furnace. The furnace was covered, and the gas inside was evacuated to a vacuum level of 0.1 Pa. The furnace temperature was then raised to 750℃ to melt the raw materials and held for 30 minutes. The crystallization shaft was then preheated to 500℃ and lowered to approximately 10 cm into the melt, with a rotation speed controlled at 80 rpm to ensure complete reaction between boron and titanium-vanadium in the system. Air was introduced at a flow rate of 50 L / min. After crystallization for 30 minutes, the crystallization shaft was lifted out of the melt, ending the rotational crystallization process. Once the temperature dropped to room temperature, the crystallized product was removed to complete the removal of impurities from the aluminum. The amount of aluminum-boron alloy added was calculated based on the Ti and V content in the molten system, ensuring that the total mass ratio of Ti and V to B in the molten system was 1:1.

[0025] The content of impurities in the system after the raw materials were melted in Example 1 is shown in Table 1.

[0026] Table 1. Impurity content in the system after raw material melting in Example 1

[0027] The types, contents, and removal rates of impurities in the crystallized product of Example 1 were tested and are shown in Table 2.

[0028] Table 2. Types, contents, and removal rates of impurities in the crystallized product of Example 1.

[0029] Example 2 The method for removing impurities from aluminum differs from that in Example 1 in that the amount of aluminum-boron alloy added is calculated based on the content of Ti and V in the melted system, so that the ratio of the total mass of Ti and V to the mass of B in the melted system is 1:5. All other aspects are the same as in Example 1.

[0030] The content of impurities in the system after the raw materials of Example 2 were tested is shown in Table 3.

[0031] Table 3. Impurity content in the system after raw material melting in Example 2

[0032] The types, contents, and removal rates of impurities in the crystallized product of Example 2 were tested and are shown in Table 4.

[0033] Table 4. Types, contents, and removal rates of impurities in the crystallized product of Example 2.

[0034] Example 3 The method for removing impurities from aluminum differs from that in Example 1 in that the amount of aluminum-boron alloy added is calculated based on the content of Ti and V in the melted system, so that the ratio of the total mass of Ti and V to the mass of B in the melted system is 1:10. All other aspects are the same as in Example 1.

[0035] The content of impurities in the system after the raw materials of Example 3 were tested is shown in Table 5.

[0036] Table 5. Impurity content in the system after raw material melting in Example 3

[0037] The types, contents, and removal rates of impurities in the crystallized product of Example 3 are shown in Table 6.

[0038] Table 6. Types, contents, and removal rates of impurities in the crystallized product of Example 3.

[0039] Example 4 The method for removing impurities from aluminum differs from that in Example 2 in that: after covering the furnace, the gas inside the furnace is extracted until the vacuum level inside the furnace is 1 Pa; otherwise, it is the same as in Example 2.

[0040] The content of impurities in the system after the raw materials were melted in Example 4 is shown in Table 7.

[0041] Table 7. Impurity content in the system after raw material melting in Example 4

[0042] The types, contents, and removal rates of impurities in the crystallized product of Example 4 are shown in Table 8.

[0043] Table 8. Types, contents, and removal rates of impurities in the crystallized product of Example 4.

[0044] Example 5 The method for removing impurities from aluminum differs from that in Example 2 in that the rotation speed during crystallization is 20 rpm, while the rest is the same as in Example 2.

[0045] The content of impurities in the system after the raw materials were melted in Example 5 is shown in Table 9.

[0046] Table 9. Impurity content in the system after raw material melting in Example 5

[0047] The types, contents, and removal rates of impurities in the crystallized product of Example 5 were tested and are shown in Table 10.

[0048] Table 10. Types, contents, and removal rates of impurities in the crystallized product of Example 5.

[0049] Example 6 The method for removing impurities from aluminum differs from that in Example 2 in that the rotation speed during crystallization is 200 rpm, while the rest is the same as in Example 2.

[0050] The content of impurities in the system after the raw materials were melted in Example 6 is shown in Table 11.

[0051] Table 11. Impurity content in the system after raw material melting in Example 6

[0052] The types, contents, and removal rates of impurities in the crystallized product of Example 6 are shown in Table 12.

[0053] Table 12. Types, contents, and removal rates of impurities in the crystallized product of Example 6.

[0054] Example 7 The method for removing impurities from aluminum differs from that in Example 2 in that the crystallization time during the crystallization process is 5 minutes, while the rest is the same as in Example 2.

[0055] The content of impurities in the system after the raw materials were melted in Example 7 is shown in Table 13.

[0056] Table 13. Impurity content in the system after raw material melting in Example 7

[0057] The types, contents, and removal rates of impurities in the crystallized product of Example 7 were tested and are shown in Table 14.

[0058] Table 14. Types, contents, and removal rates of impurities in the crystallized product of Example 7.

[0059] Example 8 The method for removing impurities from aluminum differs from that in Example 2 in that the crystallization time during the crystallization process is 60 minutes, while the rest is the same as in Example 2.

[0060] The content of impurities in the system after the raw materials were melted in Example 8 is shown in Table 15.

[0061] Table 15. Impurity content in the system after raw material melting in Example 8

[0062] The types, contents, and removal rates of impurities in the crystallized product of Example 8 are shown in Table 16.

[0063] Table 16. Types, contents, and removal rates of impurities other than aluminum in the crystallized product of Example 8.

[0064] Example 9 The method for removing impurities from aluminum differs from that in Example 2 in that the atmosphere during crystallization is replaced with argon instead of air; otherwise, it is the same as in Example 2.

[0065] The content of impurities in the system after the raw materials were melted in Example 9 is shown in Table 17.

[0066] Table 17. Impurity content in the system after raw material melting in Example 9

[0067] The types, contents, and removal rates of impurities in the crystallized product of Example 9 are shown in Table 18.

[0068] Table 18. Types, contents, and removal rates of impurities in the crystallized product of Example 9.

[0069] Example 10 The method for removing impurities from aluminum differs from that in Example 2 in that the air flow rate during crystallization is 30 L / min, while the rest is the same as in Example 2.

[0070] The content of impurities in the system after the raw materials were melted in Example 10 is shown in Table 19.

[0071] Table 19. Impurity content in the system after raw material melting in Example 10

[0072] The types, contents, and removal rates of impurities in the crystallized product of Example 10 are shown in Table 20.

[0073] Table 20. Types, contents, and removal rates of impurities in the crystallized product of Example 10.

[0074] Example 11 The method for removing impurities from aluminum differs from that in Example 2 in that the air flow rate during crystallization is 100 L / min, while the rest is the same as in Example 2.

[0075] The content of impurities in the system after the raw materials were melted in Example 11 is shown in Table 21.

[0076] Table 21. Impurity content in the system after raw material melting in Example 11

[0077] The types, contents, and removal rates of impurities in the crystallized product of Example 11 are shown in Table 22.

[0078] Table 22. Types, contents, and removal rates of impurities in the crystallized product of Example 11.

[0079] Example 12 The method for removing impurities from aluminum differs from that in Example 2 in that electrolytic aluminum is replaced with waste aluminum; otherwise, the method is the same as in Example 2.

[0080] The content of impurities in the system after the raw materials were melted in Example 12 is shown in Table 23.

[0081] Table 23. Impurity content in the system after raw material melting in Example 12

[0082] The types, contents, and removal rates of impurities in the crystallized product of Example 12 were tested and are shown in Table 24.

[0083] Table 24. Types, contents, and removal rates of impurities in the crystallized product of Example 12.

[0084] Example 13 The method for removing impurities from aluminum differs from that in Example 2 in that electrolytic aluminum is replaced with refined aluminum, while the rest is the same as in Example 2.

[0085] The content of impurities in the system after the raw materials were melted in Example 13 is shown in Table 25.

[0086] Table 25. Impurity content in the system after raw material melting in Example 13.

[0087] The types, contents, and removal rates of impurities in the crystallized product of Example 13 are shown in Table 26.

[0088] Table 26. Types, contents, and removal rates of impurities in the crystallized product of Example 13.

[0089] Example 14 The method for removing impurities from aluminum is as follows: Figure 1 The rotary crystallizer shown includes the following steps: After cleaning and air-drying, 4N refined aluminum and aluminum-boron alloy were placed in a graphite crucible inside a crystallization furnace. The furnace was covered, and the gas inside was evacuated to a vacuum level of 0.1 Pa. The furnace temperature was then raised to 750℃ to melt the raw materials and held for 30 minutes. The crystallization shaft was then preheated to 500℃ and lowered to approximately 10 cm into the melt, with a rotation speed controlled at 80 rpm to ensure complete reaction between boron and titanium-vanadium in the system. Argon gas was introduced at a flow rate of 50 L / min. After crystallization for 30 minutes, the crystallization shaft was lifted out of the melt, ending the rotational crystallization process. Once the temperature dropped to room temperature, the crystallized product was removed to complete the removal of impurities from the aluminum. The amount of aluminum-boron alloy added was calculated based on the Ti and V content in the melted system, ensuring that the total mass ratio of Ti and V to B in the melted system was 1:5.

[0090] The content of impurities in the system after the raw materials were melted in Example 14 is shown in Table 27.

[0091] Table 27. Impurity content in the system after raw material melting in Example 14

[0092] The types, contents, and removal rates of impurities in the crystallized product of Example 14 are shown in Table 28.

[0093] Table 28. Types, contents, and removal rates of impurities in the crystallized product of Example 14.

[0094] The experimental results of Examples 2, 12, 13, and 14 show that the aluminum impurity removal method provided by this invention has a good purification effect on aluminum raw materials of different purity grades. Examples 2, 12, 13, and 14 used electrolytic aluminum, waste aluminum, refined aluminum, and 4N refined aluminum as raw materials, respectively. After purification, the content of each impurity element in the resulting crystalline products was significantly reduced, indicating that the method of this invention has good applicability to aluminum raw materials of different sources and purity grades, and can effectively remove impurity elements from aluminum, thus demonstrating the wide applicability of this invention to raw materials.

[0095] Furthermore, the results of Examples 2, 12, 13, and 14 further demonstrate that for waste aluminum raw materials with high impurity content, repeated processing using the purification process described in this invention can gradually reduce the content of various impurity elements in aluminum, thereby continuously improving the purity of the aluminum. The detection results of Example 14 show that the content of each impurity element in the obtained crystalline product meets the content standard of 4N8 grade high-purity aluminum (grade GB / T 33912-2017), indicating that the method of this invention can not only further purify high-purity raw materials but also gradually purify low-purity aluminum raw materials to high-purity aluminum grades through multiple purification processes.

[0096] Therefore, the aluminum purification method provided by this invention is applicable to various types of aluminum raw materials such as electrolytic aluminum, waste aluminum, refined aluminum, and high-purity aluminum. Moreover, it can achieve a gradual increase in aluminum purity through repeated purification, thereby obtaining products that meet the high-purity aluminum standard requirements. It has the advantages of strong raw material adaptability, stable purification effect, and the ability to prepare high-purity aluminum.

[0097] Comparative Example 1 The method for removing impurities from aluminum differs from that in Example 2 in that no aluminum-boron alloy was added; otherwise, the method is the same as in Example 2.

[0098] The content of impurities in the system after the raw materials in Comparative Example 1 were tested and is shown in Table 29.

[0099] Table 29. Impurity content in the system after raw material melting in Comparative Example 1

[0100] The types, contents, and removal rates of the crystallized products in Comparative Example 1 are shown in Table 30. It is evident that the absence of aluminum-boron alloy resulted in a zero B content in the molten system, leading to the failure to remove Ti and V. This indicates that the introduction of B is crucial for the effective removal of Ti and V. B reacts with Ti and V to form denser borides that settle at the bottom of the melt. Without the introduction of B, impurities with equilibrium distribution coefficients greater than 1, such as Ti and V, would accumulate in large quantities in the crystallized products during rotational crystallization, making effective removal impossible.

[0101] Table 30. Types, contents, and removal rates of impurities in the crystallized product of Comparative Example 1

[0102] Comparative Example 2 The method for removing impurities from aluminum differs from that in Example 2 in that the amount of aluminum-boron alloy added is calculated based on the content of Ti and V in the melted system, so that the ratio of the total mass of Ti and V to the mass of B in the melted system is 1:0.1. All other aspects are the same as in Example 2.

[0103] The content of impurities in the system after melting of the raw materials in Comparative Example 2, as shown in Table 31, was determined by testing.

[0104] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 2 are shown in Table 32. It can be seen that when the content of B element is too low, the removal of Ti and V will not be obvious, while B will be introduced.

[0105] Table 32. Types, contents, and removal rates of impurities in the crystallized products of Comparative Example 2

[0106] Comparative Example 3 The method for removing impurities from aluminum differs from that in Example 2 in that the amount of aluminum-boron alloy added is calculated based on the content of Ti and V in the melted system, so that the ratio of the total mass of Ti and V to the mass of B in the melted system is 1:20. All other aspects are the same as in Example 2.

[0107] Table 33. Impurity content in the system after raw material melting in Comparative Example 3

[0108] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 3 are shown in Table 34. It can be seen that when the content of B element is too high, although the removal of Ti and V is obvious, a large amount of B is introduced.

[0109] Table 34. Types, contents, and removal rates of impurities in the crystallized products of Comparative Example 3

[0110] The experimental results of Examples 2, 2, and 3 show that the ratio of the total mass of Ti and V to the mass of B in the molten system has a significant impact on the impurity removal effect. When the ratio is 1:5, B can react fully with Ti and V to form borides and precipitate, thus effectively removing Ti and V while avoiding excessive B residue. However, when the ratio is 1:0.1, the insufficient amount of B makes it difficult for Ti and V to react fully to form borides, resulting in a significant decrease in removal efficiency. When the ratio is 1:20, although the removal efficiency of Ti and V is improved, the excessive amount of B leads to a large amount of B impurities remaining in the system, which is detrimental to obtaining high-purity aluminum products. This indicates that controlling the ratio of the total mass of Ti and V to the mass of B within an appropriate range is beneficial for achieving effective removal of Ti and V while avoiding B contamination, and is an important process condition for achieving good purification results.

[0111] Comparative Example 4 The method for removing impurities from aluminum differs from that in Example 2 in that: after covering the furnace, the gas inside the furnace is extracted until the vacuum level inside the furnace is 10 Pa; otherwise, it is the same as in Example 2.

[0112] The impurity content in the system after the raw materials in Comparative Example 4 are shown in Table 35.

[0113] Table 35. Impurity content in the system after raw material melting in Comparative Example 4

[0114] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 4 are shown in Table 36.

[0115] Table 36. Types, contents, and removal rates of impurities in the crystallized products of Comparative Example 4

[0116] Comparative Example 5 The method for removing impurities from aluminum differs from that in Example 2 in that: after covering the furnace, the gas inside is extracted until the vacuum level inside the furnace reaches 1×10⁻⁶. 5 Pa, the rest are the same as in Example 2.

[0117] The content of impurities in the system after the raw materials in Comparative Example 5 are shown in Table 37.

[0118] Table 37. Impurity content in the system after raw material melting in Comparative Example 5

[0119] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 5 are shown in Table 38.

[0120] Table 38. Types, contents, and removal rates of impurities in the crystallized products of Comparative Example 5

[0121] The results from Examples 2, 4, and 5 show that vacuum level has a significant impact on impurity removal efficiency. In Example 2, with a vacuum level of 0.1 Pa, volatile impurities such as Zn and Mg can be effectively volatilized and removed under vacuum conditions, with a high removal rate. However, in Comparative Examples 4 and 5, as the vacuum level decreases, the driving force for the volatilization of Zn and Mg weakens, and their removal rate decreases significantly. Simultaneously, the removal efficiency of segregation impurities such as Si and Fe also decreases. This indicates that controlling the vacuum level within a lower pressure range is beneficial for improving impurity removal efficiency and is an important process condition for achieving purification effects.

[0122] Comparative Example 6 The method for removing impurities from aluminum differs from that in Example 2 in that the rotation speed during crystallization is 0, while all other aspects are the same as in Example 2.

[0123] The impurity content in the system after the raw materials in Comparative Example 6 are shown in Table 39.

[0124] Table 39. Impurity content in the system after raw material melting in Comparative Example 6

[0125] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 6 are shown in Table 40. It can be seen that in the absence of rotation, the removal of Si and Fe is not obvious.

[0126] Table 40. Types, contents, and removal rates of impurities in the crystallized products of Comparative Example 6

[0127] Comparative Example 7 The method for removing impurities from aluminum differs from that in Example 2 in that the rotation speed during crystallization is 400 rpm, while the rest is the same as in Example 2. It is difficult to form crystal products due to excessively high rotation speed.

[0128] The content of impurities in the system after the raw materials in Comparative Example 7 are shown in Table 41.

[0129] Table 41. Impurity content in the system after raw material melting in Comparative Example 7

[0130] The experimental results from Examples 2, 6, and 7 show that the rotational speed during the spin crystallization process has a significant impact on the impurity removal effect. A rotational speed of 80 rpm effectively promotes impurity removal. However, at 0 rpm, the melt is essentially stationary, leading to a significant decrease in the removal rate of impurities such as Si and Fe. When the rotational speed is increased to 400 rpm, the excessively high speed makes it difficult to form a stable crystallization interface, resulting in the inability to form an effective crystallized product. This indicates that controlling the rotational speed within an appropriate range is beneficial for promoting impurity removal and stabilizing the crystallization process, and is an important process condition for achieving purification effects.

[0131] Comparative Example 8 The method for removing impurities from aluminum differs from that in Example 2 in that the crystallization time during the crystallization process is 0, while the rest is the same as in Example 2. Due to insufficient crystallization time, it is difficult to form a crystalline product.

[0132] The content of impurities in the system after the raw materials in Comparative Example 8 are shown in Table 42.

[0133] Table 42. Impurity content in the system after raw material melting in Comparative Example 8

[0134] Comparative Example 9 The method for removing impurities from aluminum differs from that in Example 2 in that the crystallization time during the crystallization process is 150 minutes, while the rest is the same as in Example 2.

[0135] The content of impurities in the system after the raw materials in Comparative Example 9 are shown in Table 43.

[0136] Table 43. Impurity content in the system after raw material melting in Comparative Example 9

[0137] The types, contents, and removal rates of impurities in the high-purity aluminum of Comparative Example 9 were tested and are shown in Table 44. It can be seen that the crystallization time was too long and Ti and V were enriched in the crystals and were not removed. Other elements were also enriched in the crystals and the removal effect was not obvious.

[0138] Table 44. Types, contents, and removal rates of impurities in high-purity aluminum in Comparative Example 9

[0139] The experimental results from Examples 2, 8, and 9 show that the rotational crystallization time has a significant impact on the impurity removal effect. A crystallization time of 15 min allows for the formation of a stable crystallization interface, achieving a good purification effect. However, at a crystallization time of 0 min, no crystallization product can be formed since the crystallization process has not yet occurred. When the crystallization time is extended to 150 min, the excessively long crystallization time leads to a large accumulation of impurities on the outer layer of the crystallized product, significantly reducing the removal effect of impurities such as Si, Fe, Ti, and V, thus affecting the overall purification effect. This indicates that controlling the crystallization time within an appropriate range is beneficial for the effective removal of impurities and is an important process condition for achieving good purification results.

[0140] Comparative Example 10 The method for removing impurities from aluminum differs from that in Example 2 in that no air is introduced during the crystallization process, while the rest is the same as in Example 2. Without gas being introduced into the intermediate shaft, it is impossible to obtain a crystallized product.

[0141] The impurity content in the system after the raw materials in Comparative Example 10 are shown in Table 45.

[0142] Table 45. Impurity content in the system after raw material melting in Comparative Example 10

[0143] Comparative Example 11 The method for removing impurities from aluminum differs from that in Example 2 in that the air flow rate during crystallization is 300 L / min, while the rest is the same as in Example 2.

[0144] The content of impurities in the system after the raw materials in Comparative Example 11 are shown in Table 46.

[0145] Table 46. Impurity content in the system after raw material melting in Comparative Example 11

[0146] The types, contents, and removal rates of impurities in the crystallized product of Comparative Example 11 were tested and are shown in Table 47. It can be seen that when the gas flow is too high, Ti and V impurities do not have enough time to react and settle, and are enriched in large quantities in the crystallized product. The removal effect of other elements is also not obvious.

[0147] Table 47. Types, contents, and removal rates of impurities in the crystallized product of Comparative Example 11

[0148] The experimental results from Examples 2, 10, and 11 show that the gas introduced during rotary crystallization and its flow rate have a significant impact on the crystallization process and the impurity removal effect. Introducing air at a certain flow rate ensures the smooth progress of the rotary crystallization process and achieves effective impurity removal. However, when no gas is introduced during crystallization, it is difficult to form a stable crystallization interface, thus failing to obtain a crystalline product. When the gas flow rate is increased to 300 L / min, the crystallization rate becomes too fast, leading to a significant decrease in impurity removal efficiency. This indicates that controlling the gas flow rate within an appropriate range is beneficial for maintaining a stable crystallization process and improving impurity removal efficiency, and is an important process condition for achieving good purification results.

[0149] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A method for removing impurities from aluminum, characterized in that, Includes the following steps: The aluminum raw material and aluminum-boron alloy are melted in a vacuum environment and then held at a certain temperature. After the holding period, the resulting product is subjected to rotational crystallization to remove impurities from the aluminum.

2. The method for removing impurities from aluminum according to claim 1, characterized in that, Impurities in the aluminum raw material include the equilibrium distribution coefficient. k 0 Impurities <0.2, 0.2≤ k 0 ≤ 1 impurities and k 0 Impurities greater than 1.

3. The method for removing impurities from aluminum according to claim 2, characterized in that, The impurities in the aluminum raw material include Si, Fe, Zn, Mg, Ti, and V.

4. The method for removing impurities from aluminum according to claim 3, characterized in that, The aluminum raw material contains 5-15000ppm of Si, 5-20000ppm of Fe, 1-3000ppm of Ti, 1-2000ppm of V, 1-4000ppm of Zn, and 1-2000ppm of Mg.

5. The method for removing impurities from aluminum according to claim 1, characterized in that, In the aluminum-boron alloy, the content of B is 4 wt.% and the content of Al is 96 wt.%. In the melted system, the ratio of the total mass of V and Ti to the mass of B is 1:1 to 1:

10.

6. The method for removing impurities from aluminum according to claim 1, characterized in that, The pressure of the vacuum is ≤1 Pa; The melting temperature is 670~800℃; The heat preservation time is >20 minutes.

7. The method for removing impurities from aluminum according to claim 1, characterized in that, The conditions for rotational crystallization are: rotation speed of 0~300 rpm, temperature of 500~700℃, time of 5min~90min, atmosphere of air or inert gas, and gas flow rate of 20~200L / min.

8. The application of the method for removing impurities from aluminum according to any one of claims 1 to 7 in the preparation of high-purity aluminum.

9. An application as described in claim 8, characterized in that, The aluminum raw material is refined aluminum with a purity of 4N or higher, and the aluminum is subjected to a single impurity removal process.

10. An application as described in claim 8, characterized in that, The aluminum raw material is aluminum with a purity of less than 4N, and the method for removing impurities from the aluminum is repeated two or more times.

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