A production device and method for preparing 5N high-purity tellurium from 2N crude tellurium

Abstract

The application discloses a production device for preparing 5N high-purity tellurium from 2N crude tellurium, which comprises a distillation-condensation system and a vacuum degree control system for controlling the vacuum degree in the distillation-condensation system; the distillation-condensation system comprises, from bottom to top, a distillation section, a first-stage condensation section, a second-stage condensation section and a third-stage condensation section; the first-stage condensation section, the second-stage condensation section and the third-stage condensation section are provided with condensation temperature control devices for controlling the temperature of the condensation sections to be gradually lowered from the lower condensation section to the upper condensation section; and the distillation section is provided with a distillation temperature control device. The application also provides a production method for preparing 5N high-purity tellurium from 2N crude tellurium by using the above production device. The application has the advantages of short production cycle, short process, no reagent consumption, simple operation, good impurity separation effect, convenient sampling, high-purity products mainly concentrated in the second-stage condensation section, no secondary pollution in the sampling process and the like, and has a wide market application prospect.

Description

Technical Field

[0001] This invention belongs to the field of tellurium purification, and particularly relates to a purification apparatus and method for crude tellurium. Background Technology

[0002] Tellurium, a semimetal, exhibits relatively strong metallic properties and is widely used in defense, aerospace, semiconductors, and electronic communications. For example, CdTe is an important material for solar cells, HgCdTe, ZnCdTe, and PbSnTe are crucial materials for infrared detection research, and BiTe and PbTe are excellent cooling materials. Trace impurities in tellurium directly affect material performance. For instance, impurities can induce point defects in CdTe, thus affecting the heat treatment process and reducing the bandgap, ultimately lowering the photoelectric conversion efficiency of the absorption layer. Therefore, tellurium purification is of great importance.

[0003] Crude tellurium purification techniques include chemical and physical methods. Chemical purification methods include precipitation, aqueous solution reduction, electrolysis, and extraction. For example, Chinese patent CN106276820A discloses a method for preparing high-purity tellurium from crude tellurium powder. This method involves first heating and washing the crude tellurium powder, then pressurizing and oxidizing the washing residue with an alkaline solution. The alkaline solution is then neutralized with dilute sulfuric acid to precipitate the residue, resulting in a precipitate. The oxidized alkaline leaching residue is then leached with dilute sulfuric acid, and the acidic solution is neutralized and reduced with oxalic acid to obtain another precipitate. The precipitates obtained from the previous two steps are then subjected to alkaline leaching to form a solution, which is then refined by electrolysis to obtain high-purity tellurium. This chemical purification method requires wet pretreatment of the raw materials, resulting in a long process, cumbersome operation, high reagent consumption, a high risk of contamination during operation, and low current efficiency during electrolysis.

[0004] Compared to chemical methods, physical purification of crude tellurium avoids the consumption of large amounts of reagents, reduces the risk of contamination, and can shorten the operation process to some extent. Physical purification methods for crude tellurium include vacuum distillation, zone melting, Czochralski purification, and solid-state electromigration. Tellurium is a low-melting-point, high-saturated vapor pressure metal; vacuum distillation can effectively separate most impurities from tellurium, obtaining high-purity distilled tellurium. Therefore, vacuum distillation technology is widely used. Existing technologies for preparing high-purity metals by vacuum distillation often use 4N metal as raw material, undergoing multiple distillations to prepare 5N-6N high-purity metals. For example, Chinese invention patent CN107313063A discloses a method for smelting 5N high-purity tellurium. This method first prepares 4N tellurium using a low-current-density electrodeposition method, then performs low-temperature vacuum distillation on the 4N tellurium ingot to produce distilled tellurium; finally, the distilled tellurium is crushed into small particles and heated under a hydrogen gas flow to cast ingots to obtain 5N high-purity tellurium. Chinese invention patent CN107585745A discloses a process for producing 5N tellurium. This method significantly reduces the content of some impurities in the raw materials through screening or pretreatment, thereby significantly reducing the content of impurities that are difficult to separate. Then, vacuum distillation, hydrogenation to reduce selenium, and medium-frequency ingot casting are performed to obtain high-purity 5N tellurium. However, using the above-mentioned vacuum distillation technology requires pretreatment of the raw materials, i.e., obtaining 4N tellurium that meets various specifications first. This still results in a long production cycle, a cumbersome process, and certain reagent consumption. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a production apparatus and method for preparing 5N high-purity tellurium from 2N crude tellurium, which has a short production cycle, simple process, high impurity removal efficiency, and no reagent consumption. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0006] A production apparatus for preparing 5N high-purity tellurium from 2N crude tellurium includes a distillation-condensation system and a vacuum control system for controlling the vacuum level within the distillation-condensation system. The distillation-condensation system comprises, from bottom to top, a distillation section, a primary condensation section, a secondary condensation section, and a tertiary condensation section. The primary, secondary, and tertiary condensation sections are equipped with condensation temperature control devices to control the temperature of each condensation section to decrease sequentially from the lower condensation section to the upper condensation section (i.e., the temperature decreases sequentially from the primary condensation section to the secondary condensation section and the tertiary condensation section). The distillation section is equipped with a distillation temperature control device.

[0007] In the above-mentioned production apparatus, preferably, a first perforated baffle is provided between the distillation section and the first-stage condensation section, a second perforated baffle is provided between the first-stage condensation section and the second-stage condensation section, and a third perforated baffle is provided between the second-stage condensation section and the third-stage condensation section.

[0008] In the aforementioned production apparatus, preferably, a plurality of first through holes are uniformly formed on the first perforated baffle, a second through hole is formed at the center of the second perforated baffle, and a third through hole is formed at the center of the third perforated baffle; the diameter of the first through hole is 3-4 mm, the total area of ​​the first through hole accounts for 25-30% of the total area of ​​the first perforated baffle, the area of ​​the second through hole accounts for 20-25% of the total area of ​​the second perforated baffle, and the area of ​​the third through hole accounts for 15-20% of the total area of ​​the third perforated baffle. More preferably, the diameter of the first through hole is 3 mm, 328 through holes are uniformly distributed, the total area of ​​the first through hole accounts for 29.5% of the total area of ​​the first perforated baffle, the area of ​​the second through hole accounts for 25% of the total area of ​​the second perforated baffle, and the area of ​​the third through hole accounts for 16% of the total area of ​​the third perforated baffle.

[0009] In the aforementioned production apparatus, preferably, the condensation temperature control device comprises, from bottom to top, a first heating device, a second heat preservation device, and a third cooling device. The first heating device is located on the first-stage condensation section and in the lower middle part of the second-stage condensation section (covering approximately one-third of the lower part of the second-stage condensation device), and is adjacent to the distillation temperature control device. The second heat preservation device is located in the upper middle part of the second-stage condensation section and is adjacent to the first heating device. The third cooling device is located on the third-stage condensation section and is used to rapidly reduce the temperature within the third-stage condensation section. The first heating device can provide a heat source for heating, the second heat preservation device may not provide a heat source (e.g., using a removable heat insulation plate) and is used for heat preservation, and the third cooling device may use a cooling water cooling system for rapid cooling. The first heating device and the distillation temperature control device may also optionally be equipped with heat preservation layers.

[0010] In the above-mentioned production apparatus, preferably, the vacuum control system includes a sealed housing and a vacuum-filling assembly, the vacuum-filling assembly being disposed on the sealed housing, and the distillation-condensation system being disposed within the sealed housing.

[0011] As a general technical concept, the present invention also provides a method for producing 5N high-purity tellurium from 2N crude tellurium using the above-described production apparatus, comprising the following steps:

[0012] (1) Place 2N coarse tellurium powder into the distillation section, seal the distillation-condensation system and evacuate it, set the temperature of the distillation temperature control device to 530-560℃, and set the temperature of the condensation temperature control device at the first-stage condensation section to 430-460℃ to perform one-step vacuum distillation. After the one-step vacuum distillation is completed, take a sample from the second-stage condensation section to obtain the one-step vacuum distillation product.

[0013] (2) Place the first-step vacuum distillation product obtained in the step into the distillation section, seal the distillation-condensation system and evacuate it, set the temperature of the distillation temperature control device to 510-540℃, and set the temperature of the condensation temperature control device at the first-stage condensation section to 430-460℃ to perform second-step vacuum distillation. After the second-step vacuum distillation is completed, take a sample from the second-stage condensation section to obtain the second-step vacuum distillation product.

[0014] (3) Place the two-step vacuum distillation product obtained in the step into the distillation section, seal the distillation-condensation system and evacuate it, set the temperature of the distillation temperature control device to 570-600℃, and set the temperature of the condensation temperature control device at the first-stage condensation section to 420-450℃ to perform three-step vacuum distillation. After the three-step vacuum distillation is completed, take a sample from the second-stage condensation section to obtain 5N high-purity tellurium.

[0015] In the above production method, preferably, during the two-step vacuum distillation, the set temperature of the distillation temperature control device is 10-30°C lower than the set temperature of the distillation temperature control device during the one-step vacuum distillation.

[0016] In the above production method, preferably, the distillation time for the one-step vacuum distillation and the two-step vacuum distillation is controlled to be 4-6 hours; the distillation time for the three-step vacuum distillation is controlled to be 1-3 hours. In this invention, the distillation temperature of the one-step vacuum distillation and the two-step vacuum distillation are relatively low, and the sample evaporation rate is relatively slow, which is beneficial to the separation of low-volatile impurities from the main metal and the segregation efficiency of high-volatile impurities from the main metal. Therefore, the distillation time is relatively long. The distillation temperature of the three-step vacuum distillation is higher, and the evaporation rate is faster. Therefore, the distillation time is relatively short.

[0017] In the above production method, preferably, the vacuum degree is controlled below 0.01 Pa during the one-step vacuum distillation, two-step vacuum distillation and three-step vacuum distillation.

[0018] In the above production method, preferably, at the end of the one-step vacuum distillation, two-step vacuum distillation and three-step vacuum distillation, an inert gas is introduced into the distillation-condensation system to atmospheric pressure through the vacuum control system. The inert gas is N2 or Ar with a purity of 5N.

[0019] This invention uses 2N tellurium powder as raw material. Through calculation and analysis of impurities in the raw material, the impurities are classified into highly volatile impurities and medium- and low-volatile impurities. Based on this, the raw material undergoes stepwise temperature-controlled distillation and segmented condensation to remove impurities in stages. The purity of the distilled product reaches 5N, and all impurities are below the standard values. The specific principle of this invention is as follows:

[0020] The impurities were classified by calculating their saturated vapor pressure at various temperatures, as shown in Table 1 below:

[0021] Table 1: Saturated vapor pressure of each element at various temperatures

[0022]

[0023]

[0024] Impurities are categorized into highly volatile impurities such as S, K, As, Se, and Na, and medium- and low-volatile impurities such as Ca, Mn, Al, Fe, and Cu. Among these, Se, Na, and Mg impurities have saturated vapor pressures close to those of tellurium, making them difficult to remove using conventional vacuum distillation methods. This invention employs a step-by-step impurity removal technique, multi-stage temperature control, and multi-stage condensation to achieve precise impurity removal.

[0025] The vapor pressure of impurities is related to their content in tellurium. Crude tellurium powder contains relatively high levels of low-volatility impurities such as Ca, Mn, Al, Fe, and Cu. Their vapor pressures at lower temperatures differ significantly from those of tellurium. Therefore, the first step employs low-temperature vacuum distillation to ensure that tellurium and high-volatility impurities volatilize in large quantities, while low-volatility impurities remain largely unvolatilized in the distillation residue, achieving initial separation of the main metal, tellurium, from the impurities. The second step uses even lower-temperature vacuum distillation to further reduce the distillation rate and improve the separation efficiency of low-volatility impurities from tellurium, as well as the segregation efficiency of high-volatility impurities from tellurium. The third step uses high-temperature vacuum distillation to increase the distillation rate and further reduce the impurity content. Through stepwise vacuum distillation, impurities are removed stepwise, resulting in highly efficient impurity removal.

[0026] Based on stepwise vacuum distillation, multi-stage temperature control is employed to precisely control the volatilization rate of the metal and the segregation efficiency between impurities and the main metal. Two-stage temperature control is used: the first stage controls the condensation stage, while the second stage maintains the raw materials in a molten state, ensuring tellurium volatilizes continuously at a stable rate. The coupling effect of the first and second stage temperature control maintains system equilibrium. During the first stage temperature control, the temperatures of the primary, secondary, and tertiary condensation stages are controlled to reduce the condensation rate of impurities and the main metal tellurium, allowing for thorough separation of impurities from the main metal and thus improving the segregation effect of impurities. Specifically, the first heating device covers the entire primary condensation stage and the lower third of the secondary condensation stage. The second insulation device covers the upper middle part of the secondary condensation stage to prevent excessive temperature loss and save energy. A third cooling device is used in the tertiary condensation stage, utilizing circulating cooling water for coordinated temperature control, causing the temperature to drop rapidly and fully condensing the remaining volatiles. During control, the cooling water temperature is maintained at 20-25℃, and the flow rate is controlled at 1.0-1.6 L / s.

[0027] Based on two-stage temperature control, volatile substances are controlled to undergo staged condensation. The condensation is divided into three stages. The first stage of condensation primarily condenses a small amount of low-volatility impurities. The first perforated baffle can be a porous graphite baffle to evenly disperse volatile tellurium and impurities, improving the segregation efficiency of tellurium and impurities. The second perforated baffle can be a large-pore graphite ring baffle, allowing most of the volatile substances to pass smoothly through the holes while retaining the low-volatility impurities, achieving separation of high-purity tellurium products from low-volatility impurities. The second stage of condensation is the main condensation stage. Due to the residual heat from the first stage heating, high-volatility impurities are essentially not condensed in this stage, while a large amount of metallic tellurium is condensed, thus achieving separation of high-purity tellurium products from high-volatility impurities. The third perforated baffle can be a small-pore graphite ring baffle to fully condense volatile tellurium in the second stage, reducing tellurium loss, while simultaneously enriching high-volatility impurities in the third stage of condensation. The segregation principle diagram is shown below. Figure 4 As shown.

[0028] The primary and tertiary condensate products can be collected separately. The primary condensate, due to its high content of low-volatile impurities, can be further processed by low-temperature vacuum distillation; the tertiary condensate, with its high content of high-volatile impurities, can be further processed by high-temperature vacuum distillation. The secondary condensate is purified high-purity tellurium. The primary condensate can be collected separately for low-temperature distillation, and the tertiary condensate can be collected separately for high-temperature distillation, resulting in high raw material utilization, high recovery rate, and high product purity.

[0029] In this invention, the same distillation-condensation system can be used for one-step vacuum distillation, two-step vacuum distillation, and three-step vacuum distillation; only a cleaning process is required before each vacuum distillation step. Of course, multiple distillation-condensation systems can also be used. Taking the use of the same distillation-condensation system as an example, the specific operation and parameters of this invention are as follows:

[0030] (1) First step: low temperature vacuum distillation: 1) Sample loading: Put 1.0-3.0 kg of 2N coarse tellurium powder into a graphite crucible, load the crucible into the distillation section, and seal the distillation-condensation system; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 8-12 hours; 3) Heating: Set the distillation temperature control device to 530-560℃ and the first heating device to 430-460℃. Control the distillation holding time to 4-6 hours and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system cools to room temperature, purge with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system.

[0031] (2) Second step low-temperature vacuum distillation: 1) Sample loading: Put all the products from the second-stage condensation section and the distillation products from the upper 1 / 5 of the first-stage condensation section into a graphite crucible, place the crucible into the distillation section, and seal the distillation-condensation system; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 1-2 hours; 3) Heating: Set the temperature of the distillation temperature control device to 510-540℃ and the temperature of the first heating device to 430-460℃, control the distillation holding time to 4-6 hours, and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system cools to room temperature, purge with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system.

[0032] (3) Third step: high temperature vacuum distillation: 1) Sample loading: Put all the products from the second-stage condensation section and the distillation products from the upper 1 / 5 of the first-stage condensation section into the graphite crucible, load the crucible into the distillation section, and seal the distillation-condensation system; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 1-2 hours; 3) Heating: Set the temperature of the distillation temperature control device to 570-600℃ and the temperature of the first heating device to 420-450℃. Control the distillation holding time to 1-3 hours and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system cools to room temperature, purge it with inert gas to atmospheric pressure and take a sample from the second-stage condensation section to obtain 5N high-purity tellurium. Clean the graphite crucible and the distillation-condensation system.

[0033] Compared with the prior art, the advantages of the present invention are as follows:

[0034] The production apparatus and method for preparing 5N high-purity tellurium from 2N crude tellurium of the present invention employs stepwise vacuum distillation, multi-stage temperature control, and multi-stage condensation. 5N high-purity tellurium can be directly obtained from 2N tellurium powder through vacuum distillation, with all impurities below the standard value. Compared with existing technologies for preparing 5N high-purity tellurium from crude tellurium powder, the present invention has advantages such as a short production cycle, a short process, virtually no reagent consumption, simple operation, good impurity separation effect, convenient sampling, and high-purity products mainly concentrated in the secondary condensation stage, avoiding secondary pollution during sampling. It has broad market application prospects. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1This is a schematic diagram of the production apparatus for preparing 5N high-purity tellurium from 2N crude tellurium according to the present invention.

[0037] Figure 2 for Figure 1 A schematic diagram of the structure of the first opening baffle.

[0038] Figure 3 for Figure 1 A schematic diagram of the structure of the second opening baffle.

[0039] Figure 4 This is a schematic diagram illustrating the fractionation principle of the production method for preparing 5N high-purity tellurium from 2N crude tellurium according to the present invention.

[0040] Legend:

[0041] 1. Distillation-condensation system; 11. Distillation section; 12. First-stage condensation section; 13. Second-stage condensation section; 14. Third-stage condensation section; 15. First opening baffle; 151. First through hole; 16. Second opening baffle; 161. Second through hole; 17. Third opening baffle; 171. Third through hole; 18. Condensation temperature control device; 181. First heating device; 182. Second heat preservation device; 183. Third cooling device; 19. Distillation temperature control device; 2. Vacuum control system; 21. Sealed shell; 22. Vacuum-filling assembly. Detailed Implementation

[0042] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0043] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0044] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0045] Example 1:

[0046] like Figure 1As shown, the production apparatus for preparing 5N high-purity tellurium from 2N crude tellurium in this embodiment includes a distillation-condensation system 1 and a vacuum control system 2 for controlling the vacuum level within the distillation-condensation system 1. The distillation-condensation system 1 includes, from bottom to top, a distillation section 11, a primary condensation section 12, a secondary condensation section 13, and a tertiary condensation section 14. The primary condensation section 12, the secondary condensation section 13, and the tertiary condensation section 14 are equipped with condensation temperature control devices 18 for controlling the temperature of each condensation section to decrease sequentially from the lower condensation section to the upper condensation section. The distillation section 11 is equipped with a distillation temperature control device 19.

[0047] like Figure 2 , Figure 3 As shown, in this embodiment, a first perforated baffle 15 is provided between the distillation section 11 and the first-stage condensation section 12, a second perforated baffle 16 is provided between the first-stage condensation section 12 and the second-stage condensation section 13, and a third perforated baffle 17 is provided between the second-stage condensation section 13 and the third-stage condensation section 14.

[0048] In this embodiment, a plurality of first through holes 151 are uniformly formed on the first opening baffle 15, a second through hole 161 is formed at the middle position of the second opening baffle 16, and a third through hole 171 is formed at the middle position of the third opening baffle 17; the diameter of the first through hole 151 is 3-4mm, and the total area of ​​the opening accounts for 25-30% of the total area of ​​the first opening baffle 15; the opening area of ​​the second through hole 161 accounts for 20-25% of the total area of ​​the second opening baffle 16; and the opening area of ​​the third through hole 171 accounts for 15-20% of the total area of ​​the third opening baffle 17. In this embodiment, optionally, the diameter of the first through hole 151 is 3mm, and 328 through holes are evenly distributed, with the total area of ​​the holes accounting for 29.5% of the total area of ​​the first opening baffle 15. The opening area of ​​the second through hole 161 accounts for 25% of the total area of ​​the second opening baffle 16, and the opening area of ​​the third through hole 171 accounts for 16% of the total area of ​​the third opening baffle 17.

[0049] In this embodiment, the condensation temperature control device 18 includes, from bottom to top, a first heating device 181, a second heat preservation device 182, and a third cooling device 183. The first heating device 181 is located on the first-stage condensation section 12 and at the lower 1 / 3 of the second-stage condensation section 13, and is adjacent to the distillation temperature control device 19. The second heat preservation device 182 is located in the upper middle part of the second-stage condensation section 13 and is adjacent to the first heating device 181. The third cooling device 183 adopts a cooling water system and is located on the third-stage condensation section 14 to quickly reduce the temperature in the third-stage condensation section 14.

[0050] In this embodiment, the vacuum control system 2 includes a sealed housing 21 and a vacuum-filling assembly 22. The vacuum-filling assembly 22 is disposed on the sealed housing 21, and the distillation-condensation system 1 is disposed in the sealed housing 21. The vacuum-filling assembly 22 can be a structure assembled from conventional components such as bellows, molecular pumps, and mechanical pumps.

[0051] The production method for preparing 5N high-purity tellurium from 2N crude tellurium in this embodiment includes the following steps:

[0052] (1) First step: low temperature vacuum distillation: 1) Sample loading: Put 1.8 kg of 2N coarse tellurium powder (see Table 2 for test data) into a graphite crucible, load the crucible into the distillation section 11, and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 9 h; 3) Heating: Set the distillation temperature control device 19 to 530℃ and the first heating device 181 to 430℃, control the distillation holding time to 6 h, and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, purge with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0053] (2) Second step low-temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 in the graphite crucible into the graphite crucible, and then put the crucible into the distillation section 11 and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 1 hour; 3) Heating: Set the temperature of the distillation temperature control device 19 to 520℃ and the temperature of the first heating device 181 to 440℃. Control the distillation holding time to 6 hours and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, purge it with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0054] (3) Third step: high temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 in the graphite crucible into the graphite crucible, put the crucible into the distillation section 11, and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum degree below 0.01 Pa and maintain it for 1 hour; 3) Heating: Set the temperature of the distillation temperature control device 19 to 570℃ and the temperature of the first heating device 181 to 430℃. Control the distillation holding time to 1 hour and maintain the system vacuum degree below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, fill it with inert gas to atmospheric pressure and take a sample from the second-stage condenser 13 to obtain 5N high-purity tellurium (see Table 3 for product test data). Clean the graphite crucible and the distillation-condensation system 1.

[0055] In this embodiment, 1.11 kg of product was obtained with a purity of 5N and the impurity content was all below the 5N standard.

[0056] The raw material testing data of this embodiment is shown in Table 2. The product testing data only lists the element types required by the national standard for 5N tellurium. The sum of the contents of other impurity elements is less than 3 ppm, as shown in Table 3.

[0057] Table 2: Raw Material Testing Data

[0058]

[0059] Table 3: Product Detection Data

[0060]

[0061] Example 2:

[0062] The production apparatus for preparing 5N high-purity tellurium from 2N crude tellurium in this embodiment is the same as in Embodiment 1.

[0063] The production method for preparing 5N high-purity tellurium from 2N crude tellurium in this embodiment includes the following steps:

[0064] (1) First step: low temperature vacuum distillation: 1) Sample loading: Put 2.5 kg of 2N coarse tellurium powder (see Table 4 for test data) into a graphite crucible, load the crucible into the distillation section 11, and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 12 h; 3) Heating: Set the distillation temperature control device 19 to 540℃ and the first heating device 181 to 440℃, control the distillation holding time to 5.5 h, and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system cools to room temperature, purge with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0065] (2) Second step low-temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 into the graphite crucible, and then load the crucible into the distillation section 11 and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 1.5 h; 3) Heating: Set the temperature of the distillation temperature control device 19 to 530 °C and the temperature of the first heating device 181 to 430 °C. Control the distillation holding time to 5 h and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, purge it with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0066] (3) Third step high-temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 in the graphite crucible into the graphite crucible, put the crucible into the distillation section 11, and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum degree below 0.01 Pa and maintain it for 1.5 h; 3) Heating: Set the set temperature of the distillation temperature control device 19 to 590℃ and the set temperature of the first heating device 181 to 430℃, control the distillation holding time to 1.5 h, and maintain the system vacuum degree below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, fill it with inert gas to atmospheric pressure, and take a sample from the second-stage condenser 13 to obtain 5N high-purity tellurium (see Table 5 for product test data), and clean the graphite crucible and the distillation-condensation system 1.

[0067] In this embodiment, 1.53 kg of product was obtained with a purity of 5N and the impurity content was all below the 5N standard.

[0068] The raw material testing data for this embodiment is shown in Table 4. The product testing data only lists the element types required by the national standard for 5N tellurium. The sum of the contents of other impurity elements is less than 3 ppm, as shown in Table 5.

[0069] Table 4: Raw Material Testing Data

[0070]

[0071] Table 5: Product Testing Data

[0072]

[0073] Comparative Example 1:

[0074] Comparative Example 1 does not employ a stepwise impurity removal technique and serves as a comparative example of Example 1.

[0075] The comparative example of a method for preparing 5N high-purity tellurium from 2N crude tellurium includes the following steps:

[0076] (1) First step: low temperature vacuum distillation: 1) Sample loading: Put 1.9 kg of 2N coarse tellurium powder (see Table 6 for test data) into a graphite crucible, load the crucible into the distillation section 11, and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 8 hours; 3) Heating: Set the distillation temperature control device 19 to 550℃ and the first heating device 181 to 450℃. Control the distillation holding time to 5 hours and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, purge it with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0077] (2) Second step low-temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 into the graphite crucible, and then load the crucible into the distillation section 11 and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum level below 0.01 Pa and maintain it for 1 hour; 3) Heating: Set the temperature of the distillation temperature control device 19 to 550℃ and the temperature of the first heating device 181 to 450℃. Control the distillation holding time to 5 hours and maintain the system vacuum level below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, purge it with inert gas to atmospheric pressure, take a sample, and clean the graphite crucible and the distillation-condensation system 1.

[0078] (3) Third step high-temperature vacuum distillation: 1) Sample loading: Put the distillation products from the second-stage condenser 13 and the upper part of the first-stage condenser 12 in the graphite crucible into the graphite crucible, and then put the crucible into the distillation section 11 and seal the distillation-condensation system 1; 2) Vacuuming: Evacuate the system to a vacuum degree below 0.01 Pa and maintain it for 1 hour; 3) Heating: Set the temperature of the distillation temperature control device 19 to 550℃ and the temperature of the first heating device 181 to 450℃. Control the distillation holding time to 1 hour and maintain the system vacuum degree below 0.01 Pa during the distillation process; 4) Sampling: After the distillation-condensation system 1 cools to room temperature, fill it with inert gas to atmospheric pressure and take a sample from the second-stage condenser 13 to obtain 4N7 high-purity tellurium (see Table 7 for product test data). Clean the graphite crucible and the distillation-condensation system 1.

[0079] The comparative sample yielded 1.39 kg of product with a purity of 4N7. However, the content of impurities such as Na, Mg, Al, Fe, and Ca exceeded the 5N standard.

[0080] The raw material testing data for this comparative example are shown in Table 6. The product testing data only lists the element types required by the national standard for 5N tellurium, as shown in Table 7.

[0081] Table 6: Raw Material Testing Data

[0082]

[0083] Table 7: Product Testing Data

[0084]

Claims

1. A production apparatus for preparing 5N high-purity tellurium from 2N crude tellurium, used in a method for preparing 5N high-purity tellurium from 2N crude tellurium, characterized in that, The production apparatus includes a distillation-condensation system (1) and a vacuum control system (2) for controlling the vacuum level in the distillation-condensation system (1). The distillation-condensation system (1) includes a distillation section (11), a primary condensation section (12), a secondary condensation section (13), and a tertiary condensation section (14) from bottom to top. The primary condensation section (12), the secondary condensation section (13), and the tertiary condensation section (14) are equipped with condensation temperature control devices (18) for controlling the temperature of each condensation section to decrease sequentially from the lower condensation section to the upper condensation section. The distillation section (11) is equipped with a distillation temperature control device (19). The production method Includes the following steps: (1) Place 2N coarse tellurium powder into the distillation section (11), seal the distillation-condensation system (1) and evacuate it, set the temperature of the distillation temperature control device (19) to 530-560℃, and set the temperature of the condensation temperature control device (18) at the first-stage condensation section (12) to 430-460℃ for one-step vacuum distillation. After the one-step vacuum distillation is completed, take a sample from the second-stage condensation section (13) to obtain the one-step vacuum distillation product. (2) Place the one-step vacuum distillation product obtained in step (1) into the distillation section (11), seal the distillation-condensation system (1) and evacuate it, set the temperature of the distillation temperature control device (19) to 510-540℃, and set the temperature of the condensation temperature control device (18) at the first-stage condensation section (12) to 430-460℃ to perform two-step vacuum distillation. After the two-step vacuum distillation is completed, take a sample from the second-stage condensation section (13) to obtain the two-step vacuum distillation product. (3) Place the two-step vacuum distillation product obtained in step (2) into the distillation section (11), seal the distillation-condensation system (1) and evacuate it, set the temperature of the distillation temperature control device (19) to 570-600℃, and set the temperature of the condensation temperature control device (18) at the first-stage condensation section (12) to 420-450℃ to perform three-step vacuum distillation. After the three-step vacuum distillation is completed, take a sample from the second-stage condensation section (13) to obtain 5N high-purity tellurium.

2. The production method according to claim 1, characterized in that, A first perforated baffle (15) is provided between the distillation section (11) and the first-stage condensation section (12), a second perforated baffle (16) is provided between the first-stage condensation section (12) and the second-stage condensation section (13), and a third perforated baffle (17) is provided between the second-stage condensation section (13) and the third-stage condensation section (14).

3. The production method according to claim 2, characterized in that, The first opening baffle (15) is provided with a plurality of first through holes (151) evenly, the second opening baffle (16) is provided with a second through hole (161) at the middle position, and the third opening baffle (17) is provided with a third through hole (171) at the middle position; the diameter of the first through hole (151) is 3-4mm, the total area of ​​the opening accounts for 25-30% of the total area of ​​the first opening baffle (15), the opening area of ​​the second through hole (161) accounts for 20-25% of the total area of ​​the second opening baffle (16), and the opening area of ​​the third through hole (171) accounts for 15-20% of the total area of ​​the third opening baffle (17).

4. The production method according to any one of claims 1-3, characterized in that, The condensation temperature control device (18) includes, from bottom to top, a first heating device (181), a second heat preservation device (182), and a third cooling device (183). The first heating device (181) is located on the first-stage condensation section (12) and in the lower middle part of the second-stage condensation section (13), and is adjacent to the distillation temperature control device (19). The second heat preservation device (182) is located in the upper middle part of the second-stage condensation section (13) and is adjacent to the first heating device (181). The third cooling device (183) is located on the third-stage condensation section (14) and is used to quickly reduce the temperature in the third-stage condensation section (14).

5. The production method according to any one of claims 1-3, characterized in that, The vacuum control system (2) includes a sealed housing (21) and a vacuum-filling assembly (22), the vacuum-filling assembly (22) being disposed on the sealed housing (21), and the distillation-condensation system (1) being disposed in the sealed housing (21).

6. The production method according to claim 1, characterized in that, During the two-step vacuum distillation, the set temperature of the distillation temperature control device (19) is 10-30°C lower than the set temperature of the distillation temperature control device (19) during the one-step vacuum distillation.

7. The production method according to claim 1, characterized in that, The distillation time for the one-step vacuum distillation and the two-step vacuum distillation is controlled at 4-6 hours; the distillation time for the three-step vacuum distillation is controlled at 1-3 hours.

8. The production method according to claim 1, 6, or 7, characterized in that, The vacuum level is controlled to be below 0.01 Pa during the one-step vacuum distillation, two-step vacuum distillation and three-step vacuum distillation.

9. The production method according to claim 1, 6, or 7, characterized in that, At the end of the first-step vacuum distillation, second-step vacuum distillation and third-step vacuum distillation, an inert gas is introduced into the distillation-condensation system (1) to atmospheric pressure through the vacuum control system (2). The inert gas is N2 or Ar with a purity of 5N.

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