Method and device for preparing 7N ultra-high-purity indium through distillation-zone melting method

Abstract

The invention belongs to the technical field of high-purity metal preparation, and particularly relates to a method and device for preparing 7N ultra-high-purity indium through a distillation-zone melting method. The method comprises the following steps: (1) carrying out graded vacuum distillation on a 4N-5N indium ingot serving as a raw material to obtain a distillation product; (2) carrying out hydrogenation degassing on a distillation product; (3) collecting distillation products subjected to hydrogenation degassing treatment in stages, and respectively carrying out zone melting on the distillation products to obtain zone melting products; and (4) cutting the head end and the tail end to obtain the 7N ultra-high-purity indium. According to the preparation method, graded vacuum distillation is adopted, the gas-phase mass transfer path is increased, and the impurity segregation efficiency is high; the content of gas impurities such as C, N and O is reduced through hydrogenation degassing, and the influence of the gas impurities on the zone melting process is reduced; meanwhile, zone melting is conducted on products of different impurity enrichment zones, the purification efficiency of the zone melting process is improved, 7N ultra-high-purity indium is prepared after the fractional distillation-hydrogenation degassing-zone refining process, and the product stability is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-purity metal preparation, and in particular relates to a method and device for preparing 7N ultra-high purity indium by a distillation-zone melting method. Background Art

[0002] Indium is a rare metal. Due to its advantages such as good ductility, strong plasticity, good light permeability and conductivity, it is widely used in scientific and technological fields such as solar cells, communications, atomic energy, national defense and military, and modern information industry. High-purity indium has important strategic value. For example, 5N high-purity indium is mainly used in the production of CIGS thin-film solar cells and additives for glass and ceramics. Semiconductors, ITO targets, InP and other indium materials used in the electronics industry all require the purity of indium to reach 6N-7N or above.

[0003] At present, the preparation methods of high-purity indium and ultra-high-purity indium are mainly chemical and physical methods. The chemical method includes electrolysis, metal organic compound method, low-halogen compound method, etc., and the physical method includes vacuum distillation method, zone melting method, etc. It is difficult to produce indium with a purity of more than 5N by chemical method, and the production process will produce wastewater and waste gas, so it is less used. In the physical method, due to the complex impurity composition of high-purity indium and the large difference in saturated vapor pressure of different impurities at different temperatures (see Table 1 and Table 2 below), vacuum distillation is not efficient in removing impurities with a vapor pressure close to that of indium (such as impurities Ga, Al, Mn, Ag, etc.), and zone melting is not efficient in removing impurities with a distribution coefficient close to 1 (such as impurities Zn, Sn, Pb, Cd, Mg). Therefore, it is difficult to deeply remove impurities in indium using a single method, the purification efficiency is low, the production cycle is long, and it is not conducive to the industrial production of indium.

[0004] Table 1 Saturated vapor pressure of impurities at different temperatures

[0005] Table 2 Distribution coefficients of main impurities in indium

[0006] Chinese invention patent CN116254592A provides a method for preparing 7N ultra-high purity indium. This method uses 6N indium as raw material and adopts single crystal pulling method to prepare 7N ultra-high purity indium. Seed crystals must be prepared before purification. The purification process is cumbersome and the purification efficiency is low. Chinese invention patents CN107058766A and CN117051266A both use vacuum distillation to purify metallic indium. The former uses crude indium as raw material and undergoes 5-15 distillations, while the latter uses 4N indium as raw material for vacuum distillation purification. The product purity can only reach 5N, which is difficult to further purify. Chinese invention patent CN106244830A provides a method for preparing 7N ultra-high purity indium. This method uses 4N-5N indium as raw material and adopts zone melting method to prepare 7N ultra-high purity indium. This method requires more than 26 zone meltings to achieve a product purity of 7N. The purification cycle is long, the impurity removal efficiency is low, and the raw material adaptability is poor. Impurities such as Sn, Pb, and Cd are difficult to remove deeply and efficiently.

[0007] Therefore, there is still a lack of preparation solutions and related preparation devices for high-purity indium with high impurity removal efficiency, low energy consumption and short cycle. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the preparation and purification cycle of high-purity indium is long, the impurity removal efficiency is low, and the energy consumption is high. The shortcomings and defects mentioned in the above background technology are overcome, and a method and device for preparing 7N ultra-high purity indium by distillation-zone melting method are provided.

[0009] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing 7N ultra-high purity indium by distillation-zone melting method, comprising the following steps: (1) Using 4N-5N indium ingot as raw material, performing graded vacuum distillation to obtain a distillation product; (2) subjecting the distillation product obtained in step (1) to a hydrogenation and degassing treatment; (3) collecting the distillation products after the hydrogenation and degassing treatment in step (2) in a graded manner, and performing zone smelting on the products respectively to obtain zone smelting products; (4) Cutting off the front and rear ends of the zone melting product obtained in step (3) to obtain 7N ultra-high purity indium.

[0010] From the analysis of the background technology, it can be seen that in the indium distillation process, impurities Si, Fe, Ni, Cu, etc. are low-volatility impurities, and the distillation process is mainly enriched in the distillation residue; impurities P, S, Zn, Mg, Cd, etc. are high-volatility impurities, and the distillation process is mainly enriched at the top of the distillation product; impurities Ga, Al, Mn, Ag, etc. are similar in volatility to indium. Therefore, the indium distillation process will obtain multiple sections of distillation products with different content components. Conventional distillation is difficult to effectively condense, and subsequent treatment is required to improve the purification effect. One reason for the low efficiency of impurity removal in conventional regional smelting is that indium contains a high level of gas impurities (such as impurity O), because oxygen will form oxides with metal impurities, which is difficult to remove by regional smelting. Therefore, the present application adds a hydrogenation degassing process after the distillation is completed, and after the distillation is completed, the influence of impurity O on the regional smelting process is removed. Immediately connecting the regional smelting, the regional smelting effect can be well improved, the number of regional smelting times can be reduced, and a high-purity indium product can be obtained.

[0011] In addition, the present application collects the distillation products in grades and performs regional smelting on them respectively, and can design the steps and times of regional smelting according to the conditions of the distillation products, so as to obtain the indium product with the best regional smelting effect and the highest purity under the premise of minimum energy consumption and working times.

[0012] Preferably, the graded vacuum distillation in step (1) is carried out under the condition of a vacuum degree of 10 -2 Pa and below, the distillation temperature is 1000-1100℃, the condensation temperature is 500-600℃, the distillation time is 10-15 h, and the mass of the distillation residue is 8-12% of the raw material.

[0013] Preferably, the graded vacuum distillation in step (1) adopts a distillation apparatus, wherein 4-8 stages of trays are sequentially designed from bottom to top inside the distillation apparatus, and the distillation products on each stage of tray correspond to the distillation products of the tray of that stage. More preferably, 5-6 stages of trays are sequentially designed from bottom to top.

[0014] The present invention adopts a fractional distillation method and designs a multi-stage tower plate in the condensation zone so that the indium volatiles can be fully fractionated and condensed. Low-volatility impurities are enriched in the distillation residue, and relatively low-volatility impurities are condensed on the 1-2 stage tower plates. The middle part of the tower plates are indium with higher purity, and relatively high-volatility impurities are condensed on the top 1-2 stage tower plates, thereby improving the removal rate of impurities. The number of stages of the tower plates is preferably 4-8. Too few stages will make it difficult to achieve the effect of fractionation, and too many stages will cause the product to be overly dispersed, increasing the complexity of the equipment and operation. Figure 1 Taking the 6-stage tower plate as an example, the 5-6-stage tower plate can effectively condense the product while the high-purity indium product will not be too dispersed, which is beneficial to improving the direct recovery rate of high-purity indium.

[0015] Preferably, the degassing temperature of the hydrogenation degassing treatment in step (2) is 500-700°C, the degassing time is 3-5 h, and the purity of the hydrogen used in the hydrogenation is 6N or above. This process adds a hydrogenation degassing step after vacuum distillation to pre-remove gas impurities such as O, N, and C in indium, reduce the obstruction (forming oxides or adsorption) of gas impurities on other metal impurities during the zone smelting process, and effectively improve the migration efficiency of impurities during the zone smelting process of indium, thereby improving the purification efficiency of indium during the zone smelting process.

[0016] Preferably, the graded collection in step (3) is to record the distillation products of the bottom 1-2 level trays and the top 1-2 level trays in the 4-8 level trays as 1# products, and the distillation products of the remaining level trays as 2# products, and perform zone melting on the 1# products and 2# products respectively; the 1# products are subjected to 4-5 zone melting cycles, and the 2# products are subjected to 3-4 zone melting cycles. All melting zones are completely passed from the front end to the end of the indium ingot, indicating 1 zone melting.

[0017] In the traditional process, direct zone melting of indium distillation products will reduce the efficiency of impurity removal. This is because a small amount of higher volatility impurities with similar saturated vapor pressure to indium will be enriched on the top 1-2 level plates (impurity Pb), and a small amount of lower volatility impurities with similar saturated vapor pressure to indium will be enriched on the bottom 1-2 level plates (impurity Sn), and both impurities are difficult to remove in the zone melting process. Separating the graded condensation products in the indium distillation process for zone melting and purification will help improve production efficiency and the purity of indium.

[0018] Preferably, the zone melting rate is 20-50 mm / h, the zone melting temperature is 300-500°C, the number of melting zones is 3-4, and the melting zone width is 70-90 mm; during the zone melting process, inert gas is introduced into the zone melting system at a gas flow rate of 1-2 L / min.

[0019] Preferably, the inert gas is argon or nitrogen with a purity of 6N or above.

[0020] Preferably, the cutting of the head and tail ends in step (4) is to cut off 8-12% of the head end and 8-12% of the tail end; The container used for the vacuum distillation is a graphite boat, and the container used for the zone smelting is a graphite boat or a titanium boat. The ash content of the graphite boat is less than 5 ppm, and the purity of the titanium boat is above 5N.

[0021] Under the same technical concept, the present application also provides a device used in the method for preparing 7N ultra-high purity indium by the distillation-zone melting method, including distillation equipment and zone melting equipment, the distillation equipment including a furnace body and a vacuum chamber arranged inside the furnace body, the vacuum chamber is connected to a vacuum control system; a group of tower plates are arranged along the inner wall of the vacuum chamber, and the tower plates are multi-stage tower plates.

[0022] Preferably, the multi-stage trays include 1st stage tray, 2nd stage tray, 3rd stage tray, 4th stage tray, 5th stage tray and 6th stage tray from bottom to top, and each stage tray is arranged at an angle of 3-6° upward with respect to the horizontal direction of the vacuum chamber tube wall. Since the melting point of indium is very low, it will be in liquid state during the condensation process, and setting the angle is conducive to the collection of high-purity indium products on the trays.

[0023] Preferably, the first-stage tower plate is located at 35-45% of the height of the inner wall of the vacuum chamber from bottom to top, and the vertical spacing between each stage of the tower plates is 3-6% of the height of the inner wall of the vacuum chamber; the spacing between the two heaters should be maintained at 3-6% of the height of the inner wall of the vacuum chamber, thereby reducing the mutual influence of the temperature zones of the heating section and the condensation section, making the temperature distribution gradient of the condensation zone more conducive to impurity segregation and improving the impurity removal efficiency.

[0024] More preferably, two adjacent steps of the multi-stage tray are staggeredly arranged on opposite sides of the inner wall of the cavity.

[0025] Preferably, a boat is provided at the bottom of the vacuum cavity, and the raw material is arranged inside the boat; a distillation section heater and a condensation section heater are respectively provided on the outside of the vacuum cavity from bottom to top, and the condensation section heater is provided on the lower side of the tower plate and covers the first-level tower plate; a cooling water inlet and a cooling water outlet are respectively provided at the upper end of the vacuum cavity; During the distillation process, a heat source is set in the condensation section, so that the highly volatile impurities continue to migrate upward, thereby further improving the impurity removal efficiency.

[0026] The vacuum control system comprises a bellows, a gas inlet and a vacuum system. The vacuum system is connected to the vacuum cavity through the bellows, and the gas inlet is arranged on the bellows.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of the present invention adopts graded vacuum distillation, which increases the gas phase mass transfer path and improves the impurity fractionation efficiency. After the distillation, a hydrogenation degassing operation is performed to further reduce the content of gas impurities such as C, N, and O, and reduce the influence of gas impurities on the regional smelting process. At the same time, the products of different impurity enrichment areas are regionally smelted respectively, which improves the purification efficiency of the regional smelting process. Using 4-5N indium as raw material, after the graded distillation-hydrogenation degassing-regional refining process, 7N ultra-high purity indium is prepared, and the product stability is high. (2) The device provided by the present invention is designed with multiple tower plates, which can effectively separate indium products of different purities, so that different regional smelting processes are adopted for the products on different condensing plates, thereby improving the impurity removal rate; at the same time, the multi-stage tower plate distillation process of indium has a distillation effect, so that the impurities Ga, Mn, Ag, etc. that are difficult to remove in the distillation process and the impurities Sn, Zn, Pb, etc. that are difficult to remove in the regional smelting process are effectively condensed, thereby improving the impurity removal rate; the vacuum distillation and hydrogenation degassing required in the preparation method of the present invention can be carried out in the device, and the operation is convenient and simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a schematic structural diagram of the distillation equipment in the device used in the method for preparing 7N ultra-high purity indium by distillation-zone melting method in the embodiment of the present application; Among them, 1. furnace body; 2. distillation section heater; 3. condensation section heater; 4. vacuum chamber; 5. boat body; 6. raw materials; 7-1. 1st level tower plate; 7-2. 2nd level tower plate; 7-3. 3rd level tower plate; 7-4. 4th level tower plate; 7-5. 5th level tower plate; 7-6. 6th level tower plate; 8. cooling water inlet; 9. cooling water outlet; 10. bellows; 11. gas inlet; 12. vacuum system. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0033] The ash content of the graphite boat used in the examples and comparative examples is less than 5 ppm, and the purity of the titanium boat is above 5N.

[0034] Embodiment 1: The device used in the method for preparing 7N ultra-high purity indium by distillation-zone melting method in this embodiment includes a distillation device and a zone melting device, the distillation device includes a furnace body 1 and a vacuum chamber 4 arranged inside the furnace body, and the vacuum chamber 4 is connected to a vacuum control system; a group of tower plates are arranged along the inner wall of the vacuum chamber 4, and the tower plates are multi-level tower plates, which respectively include a first-level tower plate 7-1, a second-level tower plate 7-2, a third-level tower plate 7-3, and a fourth-level tower plate 7-4 from bottom to top, and each level of the tower plate is arranged at an angle of 3-6° upward in the horizontal direction of the tube wall of the vacuum chamber 4, and two adjacent levels of the multi-level tower plates are staggered on opposite sides of the inner wall of the cavity; the first-level tower plate 7-1 is located at 40% of the height of the inner wall of the vacuum chamber from bottom to top, and the vertical spacing between each level of the tower plates is 5% of the height of the inner wall of the vacuum chamber; A boat 5 is arranged at the bottom of the vacuum chamber 4, and the raw material 6 is arranged inside the boat 5; a distillation section heater 2 and a condensation section heater 3 are arranged on the outside of the vacuum chamber 4 from bottom to top, and the condensation section heater 3 is arranged on the lower side of the tower plate 7 and covers the first-level tower plate; a cooling water inlet 8 and a cooling water outlet 9 are arranged at the upper end of the vacuum chamber 4; the vacuum control system includes a bellows 10, a gas inlet 11 and a vacuum system 12, the vacuum system 12 is connected to the vacuum chamber 4 through the bellows 10, and the gas inlet 11 is arranged on the bellows 10.

[0035] This embodiment provides a method for preparing 7N ultra-high purity indium by distillation-zone melting, which specifically includes the following steps: (1) Fractional vacuum distillation.

[0036] Clean the high-purity graphite boat, weigh 5 kg of 4N indium ingot, put it into the high-purity graphite boat, put the high-purity graphite boat into the distillation furnace, and install the condenser, 4-stage tower plate, etc. in sequence, and seal it. Turn on the vacuum pump and evacuate to 10 -2 When the pressure is below 5N, turn off the vacuum pump and fill with nitrogen to normal pressure. Repeat the above operation 3 times to fully expel the air in the system. The gas purity should be above 5N.

[0037] The vacuum degree is reduced to 10 -2Pa, maintain for 2 h. Start the heating program, and start keeping warm when the temperature reaches the set temperature. During the distillation process, the distillation temperature is controlled at 1080℃, the condensation temperature is controlled at 500℃, and the distillation time is controlled at 11 h. The quality of the distillation residue is controlled to be 10% of the raw material, mainly enriching low-volatile impurities.

[0038] (2) Hydrogenation degassing.

[0039] After the distillation is finished, turn off the temperature of the distillation section and continue to maintain the temperature of the condensation section at 500°C. Turn off the vacuum pump and fill the system with H2 to normal pressure. The degassing time is controlled to 3h.

[0040] (3) Regional smelting.

[0041] The distillation products on the 1st and 2nd stage plates (referred to as 1# products) and the distillation products on the 3rd and 4th stage plates (referred to as 2# products) were respectively loaded into different graphite crucibles for zone melting and purification. The zone melting rate was controlled at 30 mm / h, the zone melting temperature was controlled at 350°C, the number of melting zones was 4, the melting zone width was controlled at 70 mm, the 1# raw material was controlled to be 4 zone melting cycles, and the 2# pure raw material was controlled to be 3 zone melting cycles. All melting zones passed completely from the front end to the end of the indium ingot, indicating one zone melting cycle, and the length of the indium ingot was 800 mm. In order to prevent indium from being oxidized during the zone melting process, an inert gas was introduced into the zone melting system, and the gas flow rate was controlled at 1 L / min. The inert gas was nitrogen with a purity of more than 6N.

[0042] (4) After the zone smelting product is taken out, 8% of the head end and 8% of the tail end are cut off. The product is 7N ultra-high purity indium. The product data is shown in Table 4.

[0043] Embodiment 2: The device used in the method for preparing 7N ultra-high purity indium by distillation-zone melting method in this embodiment includes a distillation device and a zone melting device, the distillation device includes a furnace body 1 and a vacuum chamber 4 arranged inside the furnace body, and the vacuum chamber 4 is connected to a vacuum control system; a group of tower plates 7 are arranged along the inner wall of the vacuum chamber 4, and the tower plates 7 are multi-level tower plates, which respectively include a first-level tower plate 7-1, a second-level tower plate 7-2, a third-level tower plate 7-3, a fourth-level tower plate 7-4, and a fifth-level tower plate 7-5 from bottom to top, and each level of the tower plate is arranged at an angle of 3-6° upward with the horizontal direction of the tube wall of the vacuum chamber 4; the first-level tower plate 7-1 is located at 40% of the height of the inner wall of the vacuum chamber from bottom to top, and the vertical spacing between each level of the tower plates is 5% of the height of the inner wall of the vacuum chamber; A boat 5 is arranged at the bottom of the vacuum chamber 4, and the raw material 6 is arranged inside the boat 5; a distillation section heater 2 and a condensation section heater 3 are arranged on the outside of the vacuum chamber 4 from bottom to top, and the condensation section heater 3 is arranged on the lower side of the tower plate 7 and covers the first-level tower plate; a cooling water inlet 8 and a cooling water outlet 9 are arranged at the upper end of the vacuum chamber 4; the vacuum control system includes a bellows 10, a gas inlet 11 and a vacuum system 12, the vacuum system 12 is connected to the vacuum chamber 4 through the bellows 10, and the gas inlet 11 is arranged on the bellows 10.

[0044] This embodiment provides a method for preparing 7N ultra-high purity indium by distillation-zone melting, which specifically includes the following steps: (1) Fractional vacuum distillation.

[0045] Clean the high-purity graphite boat, weigh 5 kg of 4N indium ingot, put it into the high-purity graphite boat, put the high-purity graphite boat into the distillation furnace, and install the condenser, 5-stage tower plate, etc. in sequence, and seal it. Turn on the vacuum pump and evacuate to 10 -2 When the pressure is below 200 Pa, turn off the vacuum pump and fill with nitrogen to normal pressure. Repeat the above operation 3 times to fully expel the air in the system. The gas purity should be 5N or above.

[0046] The vacuum degree is reduced to 10 -2 Pa, maintain for 2 h. Start the heating program, and start keeping warm when the temperature reaches the set temperature. During the distillation process, the distillation temperature is controlled at 1100℃, the condensation temperature is controlled at 550℃, and the distillation time is controlled at 12 h. The quality of the distillation residue is controlled to be 10% of the raw material, mainly enriching low-volatile impurities.

[0047] (2) Hydrogenation degassing.

[0048] After the distillation is finished, turn off the temperature of the distillation section and continue to maintain the temperature of the condensation section at 550°C. Turn off the vacuum pump and fill the system with H2 to normal pressure. The degassing time is controlled to 3.5 h.

[0049] (3) Regional smelting.

[0050] The distillation products on the 1st, 2nd and 5th stage plates (referred to as 1# products) and the distillation products on the 3rd and 4th stage plates (referred to as 2# products) were respectively loaded into different graphite crucibles for zone melting and purification. The zone melting rate was controlled at 35 mm / h, the zone melting temperature was controlled at 400℃, the number of melting zones was 3, the melting zone width was controlled at 80 mm, the 1# raw material was controlled to be 5 zone melting cycles, and the 2# pure raw material was controlled to be 4 zone melting cycles. All melting zones passed completely from the front end to the end of the indium ingot, indicating one zone melting cycle, and the length of the indium ingot was 800 mm. In order to prevent indium from being oxidized during the zone melting process, an inert gas was introduced into the zone melting system, and the gas flow rate was controlled at 1 L / min. The inert gas was nitrogen with a purity of more than 6N.

[0051] (4) After the zone smelting product is taken out, 10% of the head end and 10% of the tail end are cut off. The product is 7N ultra-high purity indium. The product data is shown in Table 5.

[0052] Embodiment 3: Figure 1 Schematic diagram of the structure of the distillation equipment in the device used in the method for preparing 7N ultra-high purity indium by distillation-zone melting method in the embodiment of the present application. Figure 1 , including a distillation device and a regional smelting device, the distillation device includes a furnace body 1 and a vacuum chamber 4 arranged inside the furnace body, the vacuum chamber 4 is connected to a vacuum control system; a group of tower plates 7 are arranged along the inner wall of the vacuum chamber 4, the tower plates 7 are multi-level tower plates, from bottom to top, respectively including a first-level tower plate 7-1, a second-level tower plate 7-2, a third-level tower plate 7-3, a fourth-level tower plate 7-4, a fifth-level tower plate 7-5 and a sixth-level tower plate 7-6, each level of the tower plate is arranged at an angle of 3-6° upward with respect to the horizontal direction of the tube wall of the vacuum chamber 4; the first-level tower plate 7-1 is located at 40% of the height of the inner wall of the vacuum chamber from bottom to top, and the vertical interval between each level of the tower plates is 5% of the height of the inner wall of the vacuum chamber; A boat 5 is arranged at the bottom of the vacuum chamber 4, and the raw material 6 is arranged inside the boat 5; a distillation section heater 2 and a condensation section heater 3 are arranged on the outside of the vacuum chamber 4 from bottom to top, and the condensation section heater 3 is arranged on the lower side of the tower plate 7 and covers the first-level tower plate; a cooling water inlet 8 and a cooling water outlet 9 are arranged at the upper end of the vacuum chamber 4; the vacuum control system includes a bellows 10, a gas inlet 11 and a vacuum system 12, the vacuum system 12 is connected to the vacuum chamber 4 through the bellows 10, and the gas inlet 11 is arranged on the bellows 10.

[0053] This embodiment provides a method for preparing 7N ultra-high purity indium by distillation-zone melting, which specifically includes the following steps: (1) Fractional vacuum distillation.

[0054] Clean the high-purity graphite boat, weigh 5 kg of 4N indium ingot, put it into the high-purity graphite boat, put the high-purity graphite boat into the distillation furnace, and install the condenser, 5-stage tower plate, etc. in sequence, and seal it. Turn on the vacuum pump and evacuate to 10 -2 When the pressure is below 200 Pa, turn off the vacuum pump and fill with nitrogen to normal pressure. Repeat the above operation 3 times to fully expel the air in the system. The gas purity should be 5N or above.

[0055] The vacuum degree is reduced to 10 -2 Pa, maintain for 2 h. Start the heating program, and start keeping warm when the temperature reaches the set temperature. During the distillation process, the distillation temperature is controlled at 1050℃, the condensation temperature is controlled at 500℃, and the distillation time is controlled at 13 h. The quality of the distillation residue is controlled to be 10% of the raw material, mainly enriching low-volatile impurities.

[0056] (2) Hydrogenation degassing.

[0057] After the distillation is finished, turn off the temperature of the distillation section and continue to maintain the temperature of the condensation section at 500°C. Turn off the vacuum pump and fill the system with H2 to normal pressure. The degassing time is controlled to 3 h.

[0058] (3) Regional smelting.

[0059] The distillation products on the 1st, 2nd, 5th and 6th stage plates (referred to as 1# products) and the distillation products on the 3rd and 4th stage plates (referred to as 2# products) were respectively loaded into different graphite crucibles for zone melting and purification. The zone melting rate was controlled to 40 mm / h, the zone melting temperature was controlled to 400℃, the number of melting zones was 4, the melting zone width was controlled to 80 mm, the 1# raw material was controlled to 4 zone melting cycles, and the 2# pure raw material was controlled to 3 zone melting cycles. All melting zones passed completely from the front end to the end of the indium ingot, indicating one zone melting cycle, and the length of the indium ingot was 800 mm. In order to prevent indium from being oxidized during the zone melting process, an inert gas was introduced into the zone melting system, and the gas flow rate was controlled to 1 L / min. The inert gas was nitrogen with a purity of more than 6N.

[0060] (4) After the zone smelting product is taken out, 10% of the head end and 10% of the tail end are cut off. The product is 7N ultra-high purity indium. The product data is shown in Table 6.

[0061] Comparative Example 1: The experimental apparatus used in this comparative example is exactly the same as that in Example 3, and is used to illustrate the purification effect when the hydrogenation degassing step is not performed in the process of preparing 7N ultra-high purity indium, and specifically includes the following steps: (1) Fractional vacuum distillation.

[0062] Clean the high-purity graphite boat, weigh 5 kg of 4N indium ingot, put it into the high-purity graphite boat, put the high-purity graphite boat into the distillation furnace, and install the condenser, 6-stage tower plate, etc. in sequence, and seal it. Turn on the vacuum pump and evacuate to 10 -2 When the pressure is below 200 Pa, turn off the vacuum pump and fill with nitrogen to normal pressure. Repeat the above operation 3 times to fully expel the air in the system. The gas purity should be 5N or above.

[0063] The vacuum degree is reduced to 10 -2 Pa, maintain for 2 h. Start the heating program, and start keeping warm when the temperature reaches the set temperature. During the distillation process, the distillation temperature is controlled at 1100℃, the condensation temperature is controlled at 550℃, and the distillation time is controlled at 12 h. The distillation residue is controlled to be about 10% of the raw material, mainly enriching low-volatile impurities.

[0064] (2) Regional smelting.

[0065] The distillation products on the 1st, 2nd, 5th and 6th stage plates (referred to as 1# products) and the distillation products on the 3rd and 4th stage plates (referred to as 2# products) were respectively loaded into different graphite crucibles for zone melting and purification. The zone melting rate was controlled at 35 mm / h, the zone melting temperature was controlled at 400℃, the number of melting zones was 3, the melting zone width was controlled at 80 mm, the 1# raw material was controlled to be 5 zone melting cycles, and the 2# pure raw material was controlled to be 4 zone melting cycles. All melting zones passed completely from the front end to the end of the indium ingot, indicating one zone melting cycle, and the length of the indium ingot was 800 mm. In order to prevent indium from being oxidized during the zone melting process, an inert gas was introduced into the zone melting system, and the gas flow rate was controlled at 1 L / min. The inert gas was nitrogen with a purity of more than 6N.

[0066] (3) After the zone smelting product is taken out, 10% of the head end and 10% of the tail end are cut off. The total impurity content of the product is less than 100 ppb, but the content of impurities such as S, P, Al, and Sb is relatively high, among which the Al content exceeds the 7N indium standard (YS / T 1413-2021). Although the 7N indium standard does not specify the specific content of impurities such as S, P, and Sb, the impurity content is too high, which is not conducive to the back-end application of 7N high-purity indium. The product data is shown in Table 7.

[0067] Comparative Example 2: The experimental device used in this comparative example is exactly the same as that in Example 3, and is used to illustrate the purification effect of not classifying the distillation product during the preparation of 7N ultra-high purity indium, and specifically includes the following steps: (1) Fractional vacuum distillation.

[0068] Clean the high-purity graphite boat, weigh 5 kg of 4N indium ingot, put it into the high-purity graphite boat, put the high-purity graphite boat into the distillation furnace, and install the condenser, 6-stage tower plate, etc. in sequence, and seal it. Turn on the vacuum pump and evacuate to 10 -2 When the pressure is below 5N, turn off the vacuum pump and fill with nitrogen to normal pressure. Repeat the above operation 3 times to fully expel the air in the system. The gas purity should be above 5N.

[0069] The vacuum degree is reduced to 10 -2 Pa, maintain for 2 h. Start the heating program, and start keeping warm when the temperature reaches the set temperature. During the distillation process, the distillation temperature is controlled at 1100℃, the condensation temperature is controlled at 550℃, and the distillation time is controlled at 12 h. The distillation residue is controlled to be about 10% of the raw material, mainly enriching low-volatile impurities.

[0070] (2) Hydrogenation degassing.

[0071] After the distillation is finished, turn off the temperature of the distillation section and continue to maintain the temperature of the condensation section at 550°C. Turn off the vacuum pump and fill the system with H2 to normal pressure. The degassing time is controlled to 3.5 h.

[0072] (3) Regional smelting.

[0073] The distillation products on the 1-6th stage tower plates are loaded into a graphite crucible for zone melting and purification. The zone melting rate is controlled at 35 mm / h, the zone melting temperature is controlled at 400℃, the number of melting zones is 3, the melting zone width is controlled at 80 mm, and it is controlled as 4 zone melting cycles. All melting zones pass completely from the front end to the end of the indium ingot, indicating one zone melting cycle, and the indium ingot length is 800 mm. In order to prevent indium from being oxidized during the zone melting process, an inert gas is introduced into the zone melting system, and the gas flow rate is controlled at 1 L / min. The inert gas is nitrogen with a purity of more than 6N.

[0074] (4) After the zone smelting product is taken out, 10% of the head end and 10% of the tail end are cut off. The total impurity content of the product is less than 100 ppb, but the content of impurities such as Al, Ga, and Sb is relatively high, among which the content of Al and Ga exceeds the 7N indium standard (YS / T 1413-2021). The product data is shown in Table 8.

[0075] Table 3

[0076] Table 4

[0077] Table 5

[0078] Table 6

[0079] Table 7

[0080] Table 8

[0081] From the data in the table, it can be seen that when comparative example 1 is not subjected to hydrogenation degassing, the residual content of elements such as aluminum, silicon, phosphorus, and sulfur is greatly increased, reflecting that the hydrogenation degassing step can effectively reduce the influence of gas impurities; although comparative example 2 has better effect than comparative example 1, it still has the problem of high residual content of elements such as aluminum, silicon, zinc, Sn, and Sb, reflecting the excellent removal effect of graded vacuum distillation on impurity condensation.

Claims

1. A method for preparing 7N ultra-high purity indium by distillation-zone melting, characterized in that: The following steps are involved: (1) Using 4N-5N indium ingot as raw material, performing graded vacuum distillation to obtain a distillation product; (2) subjecting the distillation product obtained in step (1) to a hydrogenation and degassing treatment; (3) collecting the distillation products after the hydrogenation and degassing treatment in step (2) in a graded manner, and performing zone smelting on the products respectively to obtain zone smelting products; (4) Cutting off the front and rear ends of the zone melting product obtained in step (3) to obtain 7N ultra-high purity indium.

2. The method according to claim 1, characterized in that The step (1) of the step of vacuum distillation is carried out under the condition of vacuum degree of 10 -2 Pa, the distillation temperature is 1000-1100℃, the condensation temperature is 500-600℃, the distillation time is 10-15 h, and the mass of the distillation residue is 8-12% of the raw material.

3. The method according to claim 1, characterized in that The graded vacuum distillation in step (1) adopts a distillation apparatus, wherein 4-8 levels of tower plates are designed from bottom to top, and the distillation products on each level of tower plates correspond to the distillation products of the tower plates of that level.

4. The method according to claim 1, wherein: The degassing temperature of the hydrogenation degassing treatment in step (2) is 500-700°C, the degassing time is 3-5 h, and the purity of the hydrogen used in the hydrogenation is above 6N.

5. The method according to claim 3, characterized in that The graded collection in step (3) is to record the distillation products of the lowest 1-2 stage trays and the upper 1-2 stage trays among the 4-8 stage trays as 1# products, and record the distillation products of the remaining stage trays as 2# products, and perform zone melting on the 1# products and the 2# products respectively; the 1# products are subjected to 4-5 zone melting, and the 2# products are subjected to 3-4 zone melting.

6. The method according to claim 5, characterized in that The zone melting rate is 20-50 mm / h, the zone melting temperature is 300-500°C, the number of melting zones is 3-4, and the melting zone width is 70-90 mm; during the zone melting process, inert gas is introduced into the zone melting system, and the gas flow rate is 1-2 L / min.

7. The method according to claim 2 or 6, characterized in that The inert gas is argon or nitrogen, and the purity is above 6N.

8. The method according to claim 1, wherein In step (4), the cutting of the head and tail ends is to cut off 8-12% of the head end and 8-12% of the tail end; The container used for the vacuum distillation is a graphite boat, and the container used for the zone smelting is a graphite boat or a titanium boat. The ash content of the graphite boat is less than 5 ppm, and the purity of the titanium boat is above 5N.

9. An apparatus used in the method for preparing 7N ultra-high purity indium by distillation-zone melting method according to any one of claims 1 to 8, characterized in that: The invention comprises a distillation device and a zone smelting device, wherein the distillation device comprises a furnace body (1) and a vacuum chamber (4) arranged inside the furnace body, wherein the vacuum chamber (4) is connected to a vacuum control system; and a group of tower plates are arranged along the inner wall of the vacuum chamber (4), wherein the tower plates are multi-stage tower plates.

10. The device according to claim 9, characterized in that The multi-stage tower plates respectively include, from bottom to top, a first-stage tower plate (7-1), a second-stage tower plate (7-2), a third-stage tower plate (7-3), a fourth-stage tower plate (7-4), a fifth-stage tower plate (7-5) and a sixth-stage tower plate (7-6), each stage of the tower plates being arranged at an angle of 3-6° upwards with respect to the horizontal direction of the tube wall of the vacuum chamber (4); wherein the first-stage tower plate (7-1) is located at a position of 35-45% of the height of the inner wall of the vacuum chamber from bottom to top, and the vertical spacing between the tower plates of each stage is 3-6% of the height of the inner wall of the vacuum chamber; A boat (5) is arranged at the bottom of the vacuum chamber (4), and the raw material (6) is arranged inside the boat (5); a distillation section heater (2) and a condensation section heater (3) are arranged on the outside of the vacuum chamber (4) from bottom to top, and the condensation section heater (3) on the outside of the vacuum chamber (4) is arranged on the lower side of the tower plate (7) and covers the first-stage tower plate (7-1); a cooling water inlet (8) and a cooling water outlet (9) are arranged on the upper end of the vacuum chamber (4); The vacuum control system comprises a bellows (10), a gas inlet (11) and a vacuum system (12); the vacuum system (12) is connected to the vacuum chamber (4) via the bellows (10); and the gas inlet (11) is arranged on the bellows (10).

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