Method for preparing high-purity indium based on integration of magnetic suspension smelting and vacuum distillation grading purification

Abstract

The invention belongs to the field of preparation of high-purity indium, and provides a method for preparing high-purity indium based on integration of magnetic suspension smelting and vacuum distillation grading purification. According to the method, a crucible in a vacuum magnetic suspension smelting furnace is communicated with a crucible in a vacuum distillation furnace through a high-temperature-resistant pipe fitting with a control valve; by controlling the pressure difference in the vacuum magnetic suspension smelting furnace and the vacuum distillation furnace in the technological process and matching with opening and closing of the control valve, molten indium subjected to high-temperature impurity removal and deoxidation is transferred into the vacuum distillation furnace under the vacuum condition, and the problem of secondary pollution caused by transferring of materials among different devices is avoided. By means of the method, preparation of the high-purity indium product with the purity larger than or equal to 99.9999% and the oxygen content smaller than or equal to 0.4 ppm is achieved, and the problem that it is difficult to further improve the purity of the high-purity indium product and further reduce the oxygen content of the high-purity indium product through an existing method is solved.

Description

Technical Field

[0001] The present invention belongs to the field of high-purity indium preparation, and relates to a method for preparing high-purity indium based on the integration of magnetic suspension melting and vacuum distillation graded purification. Background Art

[0002] Indium, with its excellent conductivity, ductility, low melting point, and optoelectronic properties, plays a key role in numerous high-tech fields, particularly in displays, semiconductors, and photovoltaics. It is a core material supporting the modern electronic information industry. With the advancement of display technology, the miniaturization of semiconductors, and the development of new energy sources, higher requirements are being placed on the purity and oxygen content of indium.

[0003] Traditional methods for preparing high-purity indium primarily include zone melting, electrolytic refining, and vacuum distillation-electrolytic refining. Zone melting is not ideal for removing certain impurity elements, particularly those with similar solubility in solid and liquid indium. Electrolytic refining also struggles to remove elements like Cd and Tl, which have similar electrical potentials to indium. Consequently, a single purification method cannot effectively remove impurity elements of varying properties, limiting further improvements in the purity of high-purity indium products and making it difficult to meet the high-end electronics industry's demand for high-purity indium. The vacuum distillation-electrolytic refining method combines the advantages of vacuum distillation and electrolytic refining to more effectively remove impurity elements of varying properties. However, this method requires separate processing steps within vacuum distillation and electrolytic refining equipment. For example, this method first uses the difference in vapor pressure between indium and impurity elements to separate some impurities in a vacuum distillation device. The indium removed by vacuum distillation is then melted and cast into an anode plate. The potential difference between indium and the impurity element is then used to electrolytically refine the anode plate in conjunction with a cathode plate (titanium plate). Indium is deposited on the cathode plate, collected, and melted to form an ingot to obtain a high-purity indium ingot. However, this method involves many intermediate steps and pollution sources are difficult to effectively control. The transfer process between different devices is prone to secondary pollution, oxidation of indium, and residual impurities, limiting the further improvement of the purity of high-purity indium products and the further reduction of oxygen content. Furthermore, this method suffers from high energy consumption. Summary of the Invention

[0004] In response to the problem that the existing technology cannot effectively remove impurity elements of different properties when preparing high-purity indium using a single purification method, and the problem that the existing technology uses different purification methods in combination to improve the removal ability of impurity elements of different properties, but requires step-by-step processing in different equipment, has many intermediate links, and is prone to secondary pollution, which limits the further improvement of the quality of high-purity indium products, the present invention provides a method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification, so as to reduce the intermediate links of the process, realize the preparation of high-purity indium with a purity of ≥99.9999% and an oxygen content of ≤0.4 ppm, and reduce the process energy consumption.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0006] The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification includes the following steps:

[0007] (1) Device construction: Connect the crucible in the vacuum magnetic levitation melting furnace and the crucible in the vacuum distillation furnace through a high-temperature resistant pipe fitting, and a control valve is provided on the high-temperature resistant pipe fitting;

[0008] (2) High-temperature volatilization impurity removal and deoxidation treatment: Close the control valve, add porous filler and raw material indium into the crucible of the vacuum magnetic levitation melting furnace under the protection of high-purity inert gas, evacuate the vacuum magnetic levitation melting furnace to a pressure of less than 1Pa, heat the crucible to 1000~1200℃ and fully keep it warm to remove volatile impurities and vacuum deoxidize, and obtain molten indium after high-temperature impurity removal and deoxidation;

[0009] In this step, the purity of the raw indium is at the 2N or 3N level, and during the heating and insulation process, the pressure in the vacuum magnetic levitation melting furnace is controlled to be less than 1 Pa;

[0010] (3) Multi-stage vacuum distillation purification and condensation collection: evacuate the vacuum distillation furnace to a pressure of less than 5×10 -3 Pa, and control the pressure in the vacuum distillation furnace to be lower than the pressure in the vacuum magnetic levitation melting furnace, open the control valve, and introduce the molten indium that has been high-temperature impurity-removed and vacuum-deoxidized into the crucible in the vacuum distillation furnace through the high-temperature resistant pipe fittings, and close the control valve; keep the pressure in the vacuum distillation furnace <5×10 -3 Pa, heating the crucible to 500-600°C for primary heat preservation distillation, during which the steam generated by the distillation enters the condensation system, and impurities are collected at a condensation temperature of 200-300°C. Then, heating the crucible to 1000-1200°C for secondary heat preservation distillation, during which the steam generated by the distillation enters the condensation system, and high-purity indium is collected at a condensation temperature of 700-800°C. The collected high-purity indium is then cooled in a vacuum distillation furnace to room temperature for forming;

[0011] (4) Product collection: The cooled and formed high-purity indium product is collected under the protection of high-purity inert gas. The purity of the high-purity indium product is ≥99.9999% and the oxygen content is ≤0.4 ppm.

[0012] In the above technical solution, in step (1), the inlet end of the high-temperature resistant pipe is controlled not to contact the melt in the crucible of the vacuum magnetic levitation melting furnace. In step (2), before opening the control valve, the relative position of the inlet end of the high-temperature resistant pipe and the melt in the crucible of the vacuum magnetic levitation melting furnace is adjusted so that the molten indium that has been subjected to high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe.

[0013] In the above technical solution, in step (3), when the pressure difference between the vacuum magnetic levitation melting furnace and the vacuum distillation furnace is used to introduce the high-temperature de-doped and deoxidized molten indium into the crucible of the vacuum distillation furnace through the high-temperature resistant pipe fitting, in order to prevent the porous filler from being sucked into the crucible of the vacuum distillation furnace, the inner diameter of the port of the first high-temperature resistant pipe fitting can be controlled to be smaller than the size of the porous filler.

[0014] In the above technical solution, the control valves are located outside the vacuum magnetic levitation melting furnace and vacuum distillation furnace for ease of operation. It is also advisable to provide insulation around the high-temperature resistant pipes outside the vacuum magnetic levitation melting furnace and vacuum distillation furnace to prevent the molten indium undergoing high-temperature impurity removal and deoxidation from solidifying in the pipes due to excessive temperature drop.

[0015] In the above technical solution, in order to enhance the convection and disturbance of the molten indium in step (2), promote impurity segregation, and make impurities such as Pb, Tl, Cd, As, and Zn better enrich and volatilize on the surface of the molten indium, the vacuum magnetic levitation melting furnace is preferably designed with an asymmetric electromagnetic field.

[0016] In the above technical solution, in order to avoid secondary contamination of indium products caused by high-temperature resistant pipes during the entire process, the high-temperature resistant pipes are preferably high-purity quartz tubes or high-purity graphite tubes.

[0017] In step (2) of the above technical solution, the holding time should be long enough to ensure that volatile impurities can be fully removed during the holding process. Volatile impurities mainly include low-boiling-point impurities such as Pb, Tl, Cd, As, and Zn. During the holding period, the composition of the volatile gas can be monitored by a mass spectrometer or spectrometer until the volatile impurities are fully removed. Preferably, the holding time in step (2) is controlled to be 1 to 2 hours.

[0018] In the above technical solution, in step (3), the time of the first-stage heat preservation distillation is preferably controlled to be 1 to 2 hours, and the time of the second-stage heat preservation distillation is preferably controlled to be 1 to 2 hours.

[0019] In step (3) of the above technical solution, the collected high-purity indium is preferably cooled to room temperature at a cooling rate of 20-50°C / s to form the indium.

[0020] In the above technical solution, the crucible of the vacuum magnetic levitation melting furnace is made of high-purity quartz or high-purity graphite, and the porous filler in the crucible is made of high-purity graphene or high-purity alumina. The purity of the high-purity quartz, high-purity graphite, high-purity graphene, and high-purity alumina is ≥99.9999%.

[0021] In the above technical solution, the porous filler is loaded at the bottom of the crucible in the vacuum magnetic levitation melting furnace to absorb impurities in the molten indium in the crucible in step (2). Furthermore, the porous filler is in a granular form and has a nano-scale or micro-scale pore structure.

[0022] In the above technical solution, the porous filler can be approximately 10 mm in size, for example, 5 to 15 mm. Accordingly, the inner diameter of the port of the first high-temperature-resistant pipe located within the vacuum magnetic levitation melting furnace is 10% to 20% smaller than the size of the porous filler. Furthermore, the porous filler can be packed into a layer at the bottom of the crucible, with a thickness of 10 to 20 mm.

[0023] In the above technical solution, the high-purity quartz tubes, high-purity quartz crucibles and other equipment involved must be soaked in aqua regia, then rinsed with high-purity deionized water and dried before use; the high-purity graphite tubes, high-purity graphene, and high-purity alumina fillers involved must be soaked in aqua regia, then rinsed with high-purity deionized water, and then calcined at a high temperature of 1000~1100℃ in a vacuum to remove impurities before use.

[0024] In the above technical solution, the purity of the high-purity inert gas is ≥99.999%, and the high-purity inert gas is high-purity argon.

[0025] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects:

[0026] 1. The present invention provides a method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification. The method connects the crucible in the vacuum magnetic levitation melting furnace and the crucible in the vacuum distillation furnace through a high-temperature resistant pipe fitting, and provides a control valve on the high-temperature resistant pipe fitting. By controlling the pressure in the vacuum magnetic levitation melting furnace and the vacuum distillation furnace during the process, a suitable pressure difference is established and the control valve is used to realize the transfer of high-temperature impurity-removed and deoxidized molten indium to the vacuum distillation furnace, thereby avoiding secondary pollution caused by the transfer of materials between different equipment, and preparing a high-purity indium product with a purity of ≥99.9999% and an oxygen content of ≤0.4 ppm, thereby solving the problems of low purity and high oxygen content of existing high-purity indium.

[0027] 2. The method of the present invention connects the vacuum magnetic levitation melting furnace and the vacuum distillation furnace through high-temperature resistant pipes, controls the pressure inside the vacuum magnetic levitation melting furnace and the vacuum distillation furnace in combination with the process, and realizes the transfer of molten indium between the vacuum magnetic levitation melting furnace and the vacuum distillation furnace under vacuum conditions. After the molten indium is transferred to the vacuum distillation furnace, it remains in a molten state, which greatly shortens its heating time in the vacuum distillation furnace. Compared with the prior art method of using multiple devices for step-by-step processing, which requires a process path of heating and melting-ingot molding-cooling-reheating and evaporation, the method of the present invention only needs to go through a process path of heating and melting-maintaining the molten indium state for evaporation. It can not only shorten the process flow and improve production efficiency, but also effectively reduce the energy consumption of the process and improve the recovery rate of indium. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a connection diagram of the device constructed in the embodiment. The figure numbers are as follows: 1 is a vacuum magnetic levitation melting furnace, 2 is a vacuum distillation furnace, 3 is a high-temperature resistant pipe fitting, 4 is a control valve, 5 is a porous filler, 6 is a crucible in the vacuum magnetic levitation melting furnace, and 7 is a crucible in the vacuum distillation furnace. DETAILED DESCRIPTION

[0029] The following examples, combined with the accompanying drawings, further illustrate the method for preparing high-purity indium based on the integrated magnetic levitation melting and vacuum distillation graded purification of the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above-mentioned invention content and implement them in a specific manner, which still falls within the scope of protection of the invention.

[0030] In the following embodiments and comparative examples, the high-purity quartz tubes, high-purity quartz crucibles and other equipment involved must be soaked in aqua regia, then rinsed with high-purity deionized water and dried before use; the high-purity graphite tubes, high-purity graphene, and high-purity alumina fillers involved must be soaked in aqua regia, then rinsed with high-purity deionized water, and then calcined at a high temperature of 1000~1100℃ in a vacuum to remove impurities before use.

[0031] In the following embodiments, the vacuum magnetic levitation melting furnace and vacuum distillation furnace used during device construction are existing equipment in the prior art. The vacuum magnetic levitation melting furnace utilizes an asymmetric electromagnetic field design and is equipped with a motor-driven lifting system to adjust the crucible's elevation, that is, to raise or lower the crucible's placement. To connect the crucible in the vacuum magnetic levitation melting furnace with the crucible in the vacuum distillation furnace via high-temperature resistant pipe fittings, through-holes matching the outer diameter of the high-temperature resistant pipe fittings are provided in the furnace bodies of the vacuum magnetic levitation melting furnace and the vacuum distillation furnace. After the high-temperature resistant pipe fittings are installed, they are sealed with sealing members.

[0032] Example 1

[0033] In this embodiment, a method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification is provided, and the steps are as follows:

[0034] (1) Device construction: Figure 1 As shown, the crucible in the vacuum magnetic levitation melting furnace is connected to the crucible in the vacuum distillation furnace through a high-temperature resistant pipe fitting. The inlet end of the high-temperature resistant pipe fitting is located above the crucible in the vacuum magnetic levitation melting furnace, and the outlet end of the high-temperature resistant pipe fitting is located at the inlet of the crucible in the vacuum distillation furnace. The inner diameter of the high-temperature resistant pipe fitting is 6 mm. A control valve is provided on the high-temperature resistant pipe fitting. The control valve is located outside the vacuum magnetic levitation melting furnace and the vacuum distillation furnace. During the entire process of step (2), the inlet end of the high-temperature resistant pipe fitting does not contact the molten indium. Before the high-temperature resistant pipe fitting is used to introduce the molten indium that has been subjected to high-temperature impurity removal and vacuum deoxidation into the crucible of the vacuum distillation furnace in step (3), the position of the crucible in the vacuum magnetic levitation melting furnace is raised so that the molten indium that has been subjected to high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe fitting.

[0035] (2) High-temperature volatilization and deoxidation treatment: Close the control valve and, under the protection of high-purity argon, fill a layer of porous filler of about 10 mm into the high-purity quartz crucible of the vacuum magnetic levitation melting furnace. Then add 100 g of raw indium (purity 99.9%). The porous filler is a high-purity graphene filler. The porous filler is granular with a particle size in the range of 5-10 mm. Evacuate the vacuum magnetic levitation melting furnace to a pressure of less than 1 Pa. Start the high-frequency electromagnetic heating system of the vacuum magnetic levitation melting furnace and heat the crucible to 1100 ° C and keep it warm for 2 h to remove volatile impurities (mainly Pb, Tl, Cd, As, Zn) in the molten indium and achieve vacuum deoxidation of the molten indium, thereby obtaining molten indium after high-temperature impurity removal and deoxidation.

[0036] During this step, the pressure in the vacuum magnetic levitation melting furnace is controlled to less than 1 Pa during the heating and insulation processes. As the raw indium gradually melts, the molten indium comes into contact with the porous filler in the crucible. The porous filler absorbs and removes some impurities from the molten indium. After the raw indium is completely melted, the molten indium remains suspended. This means that during the high-temperature volatilization and vacuum deoxidation processes, the molten indium remains suspended, preventing contact with the container and reducing contamination. During this step, the inlet end of the high-temperature resistant tubing is located above the molten indium and does not come into contact with it.

[0037] (3) Multi-stage vacuum distillation purification and condensation collection: evacuate the vacuum distillation furnace until the pressure inside the furnace is less than 10 -3Pa, and control the pressure in the vacuum distillation furnace to be at least one order of magnitude lower than the pressure in the vacuum magnetic levitation melting furnace. Raise the position of the crucible in the vacuum magnetic levitation melting furnace so that the molten indium after high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe. Open the control valve and use the pressure difference in the furnace chamber of the vacuum magnetic levitation melting furnace and the vacuum distillation furnace to guide the molten indium after high-temperature impurity removal and vacuum deoxidation through the high-temperature resistant pipe into the crucible of the vacuum distillation furnace. Close the control valve. Keep the pressure in the vacuum distillation furnace <10 -3 Pa, the crucible is heated to 500℃ for primary insulation distillation, and the time of the primary insulation distillation is controlled to be 1.5 h. During the primary insulation distillation process, low-boiling-point impurities such as Cd and Zn are distilled to form vapor and enter the condensation system. The low-boiling-point impurities are collected under the condition of a condensation temperature of 200℃, and the molten indium remains in the crucible. Then the crucible is heated to 1100℃ for secondary insulation distillation, and the time of the secondary insulation distillation is controlled to be 1.5 h. During the secondary insulation distillation process, the molten indium is distilled to form vapor and enter the condensation system. The high-boiling-point impurities such as Fe, Ni, Cu, Sn, and Al remain at the bottom of the crucible; the collected high-purity indium is rapidly cooled to room temperature at a cooling rate of 30℃ / s in a vacuum distillation furnace to form.

[0038] (4) Product collection: Collect the cooled and formed high-purity indium products under the protection of high-purity argon gas.

[0039] The high-purity indium product prepared in this example was tested for all element impurity content. The results showed that the product purity was 99.9999%, the direct indium yield was 92.8%, the impurity elements Fe, Ni, Cu, Sn, Al, Cd, Zn, Pb, and Tl were all ≤ 0.08 ppm, and the oxygen content was ≤ 0.4 ppm. The quality of the high-purity indium product prepared in this example meets the purity and oxygen content requirements of indium in the electronics industry.

[0040] Comparative Example 1

[0041] This comparative example is used for comparison with Example 1 and provides a method for preparing high-purity indium. The steps are as follows:

[0042] (1) High-temperature volatilization and deoxidation treatment: Under the protection of high-purity argon, a layer of porous filler with a thickness of about 10 mm is placed in the high-purity quartz crucible of the vacuum magnetic levitation melting furnace, and then 100 g of raw indium (purity 99.9%) is added. The porous filler is a high-purity graphene filler, and the porous filler is granular with a particle size in the range of 5-10 mm. The vacuum magnetic levitation melting furnace is evacuated to a pressure of less than 1 Pa. The high-frequency electromagnetic heating system of the vacuum magnetic levitation melting furnace is started, and the crucible is heated to 1100 °C and kept warm for 2 h to remove volatile impurities (mainly Pb, Tl, Cd, As, Zn) in the molten indium and to achieve vacuum deoxidation of the molten indium, thereby obtaining molten indium after high-temperature impurity removal and deoxidation.

[0043] In this step, during the heating and insulation process, the pressure in the vacuum magnetic levitation melting furnace is controlled to be less than 1 Pa. As the raw indium gradually melts, the molten indium contacts the porous filler in the crucible. The porous filler can adsorb and remove some impurities in the molten indium in contact with it. After the raw indium is completely melted, the molten indium is in a suspended state, that is, during the high-temperature volatilization and impurity removal and vacuum deoxidation treatment, the molten indium is in a suspended state. At this time, the molten indium can be prevented from contacting the container to reduce contamination.

[0044] (2) Ingot forming: Under the protection of high-purity argon, the molten indium after high-temperature volatilization, impurity removal and deoxidation in step (1) is transferred to a casting device for ingot forming to obtain indium ingot forming.

[0045] (3) Multi-stage vacuum distillation purification and condensation collection: under the protection of high-purity argon, the indium formed by the ingot in step (2) is added to the crucible of the vacuum distillation furnace, and the vacuum distillation furnace is evacuated until the pressure inside the furnace is less than 10 -3 Pa, and then the crucible is heated to 500℃ for primary insulation distillation, and the time of the primary insulation distillation is controlled to be 1.5 h. During the primary insulation distillation process, low-boiling-point impurities such as Cd and Zn are distilled to form vapor and enter the condensation system. The low-boiling-point impurities are collected under the condition of a condensation temperature of 200℃, and the molten indium remains in the crucible. Then the crucible is heated to 1100℃ for secondary insulation distillation, and the time of the secondary insulation distillation is controlled to be 2 h. During the secondary insulation distillation process, the molten indium is distilled to form vapor and enter the condensation system. High-purity indium is collected under the condition of a condensation temperature of 750℃, and high-boiling-point impurities such as Fe, Ni, Cu, Sn, and Al remain at the bottom of the crucible; the collected high-purity indium is rapidly cooled to room temperature at a cooling rate of 30℃ / s in a vacuum distillation furnace to form.

[0046] (4) Product collection: Collect the cooled and formed high-purity indium products under the protection of high-purity argon gas.

[0047] The high-purity indium product prepared in this comparative example was tested for all element impurity content, and the results showed that the product purity was 99.996%, the direct yield of indium was 90%, the contents of the impurity elements Fe, Ni, Cu, Sn, Al, Cd, Zn, Pb, and Tl were all ≤1 ppm, and the oxygen content was ≤3 ppm.

[0048] Compared with Example 1, the high-purity indium product of Comparative Example 1 has a higher content of impurity elements, especially a significantly increased oxygen content.

[0049] Example 2

[0050] In this embodiment, a method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification is provided, and the steps are as follows:

[0051] (1) Device construction: Same as Example 1.

[0052] (2) High-temperature volatilization and deoxidation treatment: Close the control valve and, under the protection of high-purity argon, fill a layer of porous filler of about 10 mm into the high-purity quartz crucible of the vacuum magnetic levitation melting furnace. Then add 100 g of raw indium (purity 99.9%). The porous filler is a high-purity graphene filler. The porous filler is granular with a particle size in the range of 5-10 mm. Evacuate the vacuum magnetic levitation melting furnace to a pressure of less than 0.1 Pa. Start the high-frequency electromagnetic heating system of the vacuum magnetic levitation melting furnace, heat the crucible to 1200 ° C and keep it warm for 2 h to remove volatile impurities (mainly Pb, Tl, Cd, As, Zn) in the molten indium and realize vacuum deoxidation treatment of the molten indium, obtaining suspended molten indium after high-temperature impurity removal and deoxidation.

[0053] During this step, the pressure within the vacuum magnetic levitation melting furnace is controlled to less than 0.1 Pa during the heating and insulation processes. As the raw indium gradually melts, the molten indium comes into contact with the porous filler in the crucible. The porous filler absorbs and removes some impurities from the molten indium. After the raw indium is completely melted, the molten indium remains suspended. This means that during the high-temperature volatilization and vacuum deoxidation processes, the molten indium remains suspended, preventing contact with the container and reducing contamination. During this step, the inlet end of the high-temperature resistant tubing is located above the molten indium and does not come into contact with it.

[0054] (3) Multi-stage vacuum distillation purification and condensation collection: evacuate the vacuum distillation furnace to a pressure of less than 5×10 -3Pa, and control the pressure in the vacuum distillation furnace to be at least one order of magnitude lower than the pressure in the vacuum magnetic levitation melting furnace. Raise the position of the crucible in the vacuum magnetic levitation melting furnace so that the molten indium after high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe. Open the control valve and use the pressure difference between the vacuum magnetic levitation melting furnace and the vacuum distillation furnace to guide the molten indium after high-temperature impurity removal and vacuum deoxidation through the high-temperature resistant pipe into the crucible of the vacuum distillation furnace. Close the control valve. Keep the pressure in the vacuum distillation furnace <5×10 -3 Pa, the crucible is heated to 600℃ for the first-level thermal insulation distillation, and the time of the first-level thermal insulation distillation is controlled to be 1h; during the first-level thermal insulation distillation process, low-boiling point impurities such as Cd and Zn are distilled to form vapor and enter the condensation system, and the low-boiling point impurities are collected under the condition of condensation temperature of 300℃, and the molten indium remains in the crucible. Then the crucible is heated to 1200℃ for the second-level thermal insulation distillation, and the time of the second-level thermal insulation distillation is controlled to be 2h; during the second-level thermal insulation distillation process, the molten indium is distilled to form vapor and enter the condensation system, and high-purity indium is collected under the condition of condensation temperature of 800℃, and high-boiling point impurities such as Fe, Ni, Cu, Sn, and Al remain at the bottom of the crucible; the collected high-purity indium is rapidly cooled to room temperature at a cooling rate of 50℃ / s in a vacuum distillation furnace to form.

[0055] (4) Product collection: Collect the cooled and formed high-purity indium products under the protection of high-purity argon gas.

[0056] The high-purity indium product prepared in this example was tested for all element impurity content. The results showed that the product purity was 99.99995%, the direct indium yield was 92.4%, the contents of the impurity elements Fe, Ni, Cu, Sn, Al, Cd, Zn, Pb, and Tl were all ≤ 0.1 ppm, and the oxygen content was ≤ 0.2 ppm. The quality of the high-purity indium product prepared in this example meets the purity and oxygen content requirements of indium in the electronics industry.

[0057] Example 3

[0058] The operation of this embodiment is basically the same as that of embodiment 2, except that the raw material indium with a purity of 99.9% in embodiment 2 is replaced by raw material indium with a purity of 99%.

[0059] The high-purity indium product prepared in this example was tested for all element impurity content. The results showed that the product purity was 99.9999%, the direct yield of indium was 92%, the contents of the impurity elements Cd, Zn, Pb, and Tl were all ≤0.05 ppm, the contents of the impurity elements Fe, Cu, Sn, Al, and Ni were all ≤0.1 ppm, and the oxygen content was ≤0.25 ppm. The quality of the high-purity indium product prepared in this example can also meet the purity and oxygen content requirements of indium in the electronics industry.

[0060] Example 4

[0061] In this embodiment, a method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification is provided, and the steps are as follows:

[0062] (1) Device construction: Same as Example 1.

[0063] (2) High-temperature volatilization and deoxidation treatment: Close the control valve and, under the protection of high-purity argon, fill a layer of porous filler of about 10 mm into the high-purity quartz crucible of the vacuum magnetic levitation melting furnace. Then add 100 g of raw indium (purity 99.9%). The porous filler is a high-purity alumina filler. The porous filler is granular with a particle size in the range of 5-10 mm. The vacuum magnetic levitation melting furnace is evacuated to a pressure of less than 0.5 Pa. Start the high-frequency electromagnetic heating system of the vacuum magnetic levitation melting furnace, heat the crucible to 1000 ° C and keep it warm for 2 h to remove volatile impurities (mainly Pb, Tl, Cd, As, Zn) in the molten indium and realize vacuum deoxidation of the molten indium, obtaining suspended molten indium after high-temperature impurity removal and deoxidation.

[0064] During this step, the pressure in the vacuum magnetic levitation melting furnace is controlled to less than 0.5 Pa during the heating and insulation processes. As the raw indium gradually melts, the molten indium comes into contact with the porous filler in the crucible. The porous filler absorbs and removes some impurities from the molten indium. After the raw indium is completely melted, the molten indium remains suspended. This means that during the high-temperature volatilization and vacuum deoxidation processes, the molten indium remains suspended, preventing contact with the container and reducing contamination. During this step, the inlet end of the high-temperature resistant tubing is located above the molten indium and does not come into contact with it.

[0065] (3) Multi-stage vacuum distillation purification and condensation collection: evacuate the vacuum distillation furnace until the pressure inside the furnace is less than 3×10 -3 Pa, and control the pressure in the vacuum distillation furnace to be at least one order of magnitude lower than the pressure in the vacuum magnetic levitation melting furnace. Raise the position of the crucible in the vacuum magnetic levitation melting furnace so that the molten indium after high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe. Open the control valve and use the pressure difference in the furnace chambers of the vacuum magnetic levitation melting furnace and the vacuum distillation furnace to guide the molten indium after high-temperature impurity removal and vacuum deoxidation through the high-temperature resistant pipe into the crucible of the vacuum distillation furnace. Close the control valve and maintain the pressure in the furnace chamber of the vacuum distillation furnace at <3×10 -3Pa, the crucible is heated to 550℃ for the first-level thermal insulation distillation, and the time of the first-level thermal insulation distillation is controlled to be 2 hours; during the first-level thermal insulation distillation process, low-boiling point impurities such as Cd and Zn are distilled to form vapor and enter the condensation system, and the low-boiling point impurities are collected under the condition of a condensation temperature of 250℃, and the molten indium remains in the crucible. Then the crucible is heated to 1000℃ for the second-level thermal insulation distillation, and the time of the second-level thermal insulation distillation is controlled to be 2 hours; during the second-level thermal insulation distillation process, the molten indium is distilled to form vapor and enter the condensation system, and high-purity indium is collected under the condition of a condensation temperature of 700℃, and high-boiling point impurities such as Fe, Ni, Cu, Sn, and Al remain at the bottom of the crucible; the collected high-purity indium is cooled to room temperature at a cooling rate of 20℃ / s to form.

[0066] (4) Product collection: Collect the cooled and formed high-purity indium products under the protection of high-purity argon gas.

[0067] The high-purity indium product prepared in this example was tested for all elemental impurity content. The results showed that the product purity was 99.99996%, the direct indium yield was 90%, the contents of the impurity elements Fe, Ni, Cu, Sn, Al, Cd, Zn, Pb, and Tl were all ≤ 0.06 ppm, and the oxygen content was ≤ 0.32 ppm. The quality of the high-purity indium product prepared in this example meets the purity and oxygen content requirements of indium in the electronics industry.

Claims

1. A method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification, characterized in that: The following steps are involved: (1) Device construction: Connect the crucible in the vacuum magnetic levitation melting furnace and the crucible in the vacuum distillation furnace through a high-temperature resistant pipe fitting, and a control valve is provided on the high-temperature resistant pipe fitting; (2) High-temperature volatilization impurity removal and deoxidation treatment: Close the control valve, add porous filler and raw material indium into the crucible of the vacuum magnetic levitation melting furnace under the protection of high-purity inert gas, evacuate the vacuum magnetic levitation melting furnace to a pressure of less than 1 Pa, heat the crucible to 1000~1200℃ and fully keep it warm to remove volatile impurities and vacuum deoxidize, and obtain molten indium after high-temperature impurity removal and deoxidation; In this step, the purity of the raw indium is at the 2N or 3N level, and during the heating and insulation process, the pressure in the vacuum magnetic levitation melting furnace is controlled to be less than 1 Pa; (3) Multi-stage vacuum distillation purification and condensation collection: evacuate the vacuum distillation furnace to a pressure of less than 5×10 -3 Pa, and control the pressure in the vacuum distillation furnace to be lower than the pressure in the vacuum magnetic levitation melting furnace, open the control valve, and introduce the molten indium that has been high-temperature impurity-removed and vacuum-deoxidized into the crucible in the vacuum distillation furnace through the high-temperature resistant pipe fittings, and close the control valve; keep the pressure in the vacuum distillation furnace <5×10 -3 Pa, heating the crucible to 500-600°C for primary heat preservation distillation, during which the steam generated by the distillation enters the condensation system, and impurities are collected at a condensation temperature of 200-300°C. Then, heating the crucible to 1000-1200°C for secondary heat preservation distillation, during which the steam generated by the distillation enters the condensation system, and high-purity indium is collected at a condensation temperature of 700-800°C. The collected high-purity indium is then cooled in a vacuum distillation furnace to room temperature for forming; (4) Product collection: The cooled and formed high-purity indium product is collected under the protection of high-purity inert gas. The purity of the high-purity indium product is ≥99.9999% and the oxygen content is ≤0.4 ppm.

2. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation and graded purification according to claim 1, characterized in that: In step (1), the inlet end of the high-temperature resistant pipe is controlled not to contact the melt in the crucible of the vacuum magnetic levitation melting furnace. In step (2), before opening the control valve, the relative position of the inlet end of the high-temperature resistant pipe and the melt in the crucible of the vacuum magnetic levitation melting furnace is adjusted so that the molten indium that has been subjected to high-temperature impurity removal and vacuum deoxidation contacts the inlet end of the high-temperature resistant pipe.

3. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to claim 1, characterized in that: In step (1), the control valve is located outside the vacuum magnetic levitation melting furnace and the vacuum distillation furnace.

4. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation and graded purification according to claim 1, characterized in that: The vacuum magnetic levitation melting furnace adopts an asymmetric electromagnetic field design.

5. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to any one of claims 1 to 4, characterized in that: In step (2), the holding time is controlled to be 1 to 2 h.

6. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to any one of claims 1 to 4, characterized in that: In step (3), the time for the first-stage heat preservation distillation is controlled to be 1 to 2 hours, and the time for the second-stage heat preservation distillation is controlled to be 1 to 2 hours.

7. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to any one of claims 1 to 4, characterized in that: The cooling rate during cooling in step (3) is controlled to be 20~50℃ / s.

8. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to any one of claims 1 to 4, characterized in that: The crucible of the vacuum magnetic levitation melting furnace is made of high-purity quartz or high-purity graphite, and the porous filler in the crucible is made of high-purity graphene or high-purity alumina.

9. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to claim 8, characterized in that: The porous filler is in a granular form and has a nano-scale or micro-scale pore structure.

10. The method for preparing high-purity indium based on the integration of magnetic levitation melting and vacuum distillation graded purification according to any one of claims 1 to 4, characterized in that: The high-purity inert gas includes high-purity argon.

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