Preparation method of high-purity tellurium

Abstract

The invention discloses a preparation method of high-purity tellurium. The preparation method comprises the following steps: roasting crude tellurium serving as a raw material to obtain roasted slag; preparing an electrolyte by using the roasting slag, and electrolyzing to prepare 4N-grade crude tellurium; carrying out vacuum distillation on the 4N-grade crude tellurium, and condensing through a gradient condensation technology to obtain 5N-grade tellurium; the 5N-grade tellurium is placed in a wire groove crystallization device to be smelted and recrystallized, a sample containing impurities at the first section is removed, and the 7N-grade high-purity tellurium is obtained. The method comprises the following steps: firstly, removing most impurities by using a roasting method, preparing 4N-grade crude tellurium by using an electrolysis method, removing most impurities, volatilizing residual S and Se impurities by using a method of combining vacuum distillation with gradient condensation, and finally, carrying out melting and long-path recrystallization by using a trunking crystallization device, so as to obtain the 4N-grade tellurium. The tellurium is separated from Se and S impurities in the process that the tellurium in the wire slot is crystallized and separated out after being fused, and 7N-grade tellurium can be obtained after a sample with high impurity content at the first section is removed; according to the method, 4N-grade crude tellurium can be purified into 7N-grade pure tellurium, and multi-stage distillation is not needed.

Description

Technical Field

[0001] The present invention belongs to the technical field of tellurium preparation and purification, and more specifically, the present invention relates to a method for preparing high-purity tellurium. Background Art

[0002] Tellurium (chemical symbol Te, atomic number 52), as a strategic rare and dispersed metal, its high-purity preparation technology has important value for the development of modern industry and technology. Tellurium belongs to the class of metalloids and has two allotropes: a hexagonal silver-white crystal (density 6.25 g / cm 3 ) and an amorphous black powder (density 4.6 g / cm 3 ). The melting point of tellurium is about 452 °C and the boiling point reaches 1390 °C, showing the strongest metallicity among non-metallic elements. In terms of chemical properties, tellurium is stable at room temperature and can form tellurides with halogens at high temperatures (such as TeCl, TeF4), soluble in strong acids such as sulfuric acid and nitric acid, but insoluble in water and carbon disulfide. This unique semiconductor property (band gap 0.34 eV) makes it an ideal material for the electronics industry. Tellurium is widely used in the new energy field, semiconductors and electronic devices, national defense and aerospace, and special materials industry.

[0003] Existing preparation processes mainly extract tellurium from copper electrolysis anode slime. The polysulfide sodium extraction method can obtain a purity of 99.999%, but there are bottlenecks such as high reagent consumption (3.5 tons of Na2S consumed per ton of tellurium) and high three-waste treatment costs. In recent years, the combined process of vacuum distillation - zone melting can increase the purity to 99.9999% (6N), but the equipment investment intensity is 2.3 times that of traditional methods. Although the melting point of tellurium is about 450 °C, it starts to volatilize at temperatures close to 400 °C. The main impurities in the crude tellurium product include elements such as selenium (Se), sulfur (S), zinc (Zn), cadmium (Cd), aluminum (Al), copper (Cu), iron (Fe), silver (Ag), etc. The saturated vapor pressures of different impurity elements are different. When distilling and purifying tellurium using the difference in saturated vapor pressure between tellurium and most impurities, the saturated vapor pressures of elements such as zinc, cadmium, and selenium are higher than that of tellurium. Therefore, during vacuum distillation, impurities with a vapor pressure lower than that of cadmium basically do not volatilize and remain at the bottom of the pot, while impurities with a vapor pressure close to or higher than that of cadmium enter the gas phase together with cadmium. Next, it is necessary to combine the difference in condensation temperatures of different impurities. Tellurium and impurities with a higher vapor pressure will condense in different regions, thus achieving the purpose of purification. Currently, the purification method of vacuum distillation combined with recrystallization precipitation still has an unsatisfactory purification effect on tellurium. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or defects and provide at least the advantages described hereinafter.

[0005] To achieve these objects and other advantages according to the present invention, a method for preparing high-purity tellurium is provided, comprising the following steps:

[0006] Step 1: Roast using crude tellurium as raw material to obtain roasted slag;

[0007] Step 2: Prepare the roasted slag as an electrolyte and electrolyze to prepare 4N-grade crude tellurium;

[0008] Step 3: Perform vacuum distillation on the 4N-grade crude tellurium to remove low-boiling impurities, and condense by gradient condensation technology to obtain 5N-grade tellurium;

[0009] Step 4: Place the 5N-grade tellurium in a wire groove crystallization device, perform melting and recrystallization, remove the sample containing impurities at the head, and obtain 7N-grade high-purity tellurium.

[0010] Preferably, the specific method of Step 1 includes: mixing crude tellurium and concentrated sulfuric acid with a mass concentration of 98% at a mass ratio of 1-3:1, placing it in a rotary kiln, roasting at 350-600 °C for 1-3 h, and cooling to room temperature to obtain roasted slag.

[0011] Preferably, in Step 2, the specific method of preparing the roasted slag as an electrolyte includes: dissolving the roasted slag in 0.5-1 mol / L NaOH solution, stirring and mixing evenly to obtain the electrolyte, and the dosage ratio of the roasted slag to the NaOH solution is 1 g:2-10 mL.

[0012] Preferably, in Step 2, the specific method of electrolyzing to prepare 4N-grade crude tellurium includes: using a titanium-based coated DSA as the anode and Ag as the cathode, heating the electrolyte to a temperature of 30-50 °C, with a current density of 450-550 A / m 2 , electrolyzing for 24-72 h; after electrolysis, stripping, washing, and vacuum drying the cathode product to obtain 4N-grade crude tellurium.

[0013] Preferably, in Step 3, the temperature for vacuum distillation of the 4N-grade is 450-600 °C, the vacuum degree of vacuum distillation is less than 2.5×10 -2 Pa, and the time for vacuum distillation is 3-8 h.

[0014] Preferably, in Step 3, the specific method of gradient condensation technology includes: first cooling at a cooling rate of 5-10 °C / min to 400-440 °C, and then cooling at a cooling rate of 5-10 °C / min to 300-400 °C.

[0015] Preferably, in Step 4, the temperature for melting and recrystallization is 460-560 °C.

[0016] Preferably, in step 4, the structure of the wire groove crystallization device includes:

[0017] A housing, at one end of its interior is provided with a graphite crucible groove for containing and melting 5N grade tellurium. The housing is hermetically provided with a cover. At one end of the housing is provided with a vacuum port for evacuating and a ventilation port for introducing hydrogen.

[0018] Multiple wire grooves, which are arranged in a two-stage V shape in the axial direction of the housing. The width of the wire groove is 0.5 - 2 mm. The wire groove includes a first wire groove communicating with the graphite crucible and a second wire groove connected to the first wire groove. The connection between the first wire groove and the second wire groove is smoothly connected.

[0019] Multiple thermocouples, which are arranged at intervals at the lower end of the wire groove. The upper surface of the thermocouple is in contact with the lower surface of the wire groove. A water-cooling pipeline is arranged between adjacent two thermocouples, and the water-cooling pipeline is in contact with the lower surface of the wire groove.

[0020] Preferably, the included angle between the center line of the first wire groove and the horizontal line in the axial direction of the housing is 1 - 4°, and the included angle between the center line of the second wire groove and the horizontal line in the axial direction of the housing is 6 - 8°.

[0021] Preferably, during recrystallization, the heating temperatures of each thermocouple are different, and the heating temperatures of each thermocouple gradually decrease one by one along the direction away from the graphite crucible groove. The heating temperature range of the thermocouple is 400 - 500 °C.

[0022] The present invention has at least the following beneficial effects: The present invention provides a method for preparing high-purity tellurium. First, most impurities are removed by roasting method. Subsequently, the roasted slag obtained by roasting is configured into an electrolyte, and 4N grade crude tellurium is prepared by electrolysis method to remove most of the S and Se impurities. Then, the remaining S and Se impurities are volatilized by vacuum distillation combined with gradient condensation. Finally, the wire groove crystallization device is used for melting and long-path recrystallization. During the process of crystallization and precipitation of tellurium in the wire groove after melting, tellurium is separated from Se and S impurities. After removing the samples with higher impurity content at the head, 7N grade tellurium can be obtained. That is, by using the purification method of the present invention, it can ensure that 4N grade crude tellurium is purified to 99.99999% pure tellurium, greatly improving the purity and quality of tellurium products, and there is no need for multi-stage distillation.

[0023] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. Description of the Drawings

[0024] Figure 1Schematic axial cross-section of the wire groove crystallization device used in Embodiment 1 of the present invention; Detailed implementation manners

[0025] The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it according to the description in the specification.

[0026] It should be understood that terms such as "having", "including", and "comprising" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0027] The cross-sectional views of the wire groove crystallization device used in Step 4 of Embodiments 1 - 3 and Comparative Examples 1 - 2 are as Figure 1 shown. The wire groove crystallization device includes:

[0028] A housing 1, at one end of its interior, there is provided a graphite crucible groove 2 for containing and melting 5N grade tellurium. A cover 3 is hermetically provided on the housing 1. At one end of the housing 1, there are provided a vacuum port 101 for evacuating and a gas inlet 102 for introducing hydrogen;

[0029] A plurality of wire grooves 4, which are arranged in a two-stage V shape in the axial direction of the housing. The width of the wire groove 4 is 2 mm, the width of the groove is 5 mm, and the total length of the wire groove is 800 mm. The wire groove 4 includes a first wire groove 41 communicating with the graphite crucible and a second wire groove 42 connected to the first wire groove 41. The connection between the first wire groove 41 and the second wire groove 42 is a smooth connection. The length of the first wire groove 41 is 500 mm, and the length of the second wire groove 42 is 300 mm;

[0030] A plurality of thermocouples 5, which are correspondingly arranged at the lower end of the wire groove 4. The upper surface of the thermocouple 5 is in contact with the lower surface of the wire groove 4. A water cooling pipeline 6 is provided between adjacent two thermocouples. The water outlet and water inlet of the water cooling pipeline 6 are located on both sides of the housing 1. The water cooling pipeline 6 is arranged in a U shape, and its width is slightly larger than the transverse width of the plurality of wire grooves 4, and can completely cover the plurality of wire grooves 4. The water cooling pipeline 6 is in contact with the lower surface of the wire groove 4. The water cooling pipeline 6 is used to cool the wire groove above it, weaken the temperature transfer on the wire groove 4, and ensure the formation of a temperature gradient in the wire groove 4.

[0031] The included angle between the center line of the first wire groove 41 and the axial horizontal line of the housing 1 is 2°, and the included angle between the center line of the second wire groove 42 and the axial horizontal line of the housing 1 is 4°.

[0032] When recrystallization is carried out, the heating temperatures of the respective thermocouples are different, and the heating temperatures of the respective thermocouples gradually decrease one by one along the direction away from the graphite crucible groove. The heating temperature range of the thermocouple 5 is 400 to 500 °C, and the thermocouple 5 is set in a U shape with the same lateral width as that of the plurality of wire grooves 4.

[0033] Example 1

[0034] This example provides a method for preparing high-purity tellurium, which includes the following steps:

[0035] Step 1: Mix 1000 g of crude tellurium with 1000 g of concentrated sulfuric acid with a mass concentration of 98%, place it in a rotary kiln, roast it at 600 °C for 3 h, and obtain roasted slag after cooling to room temperature.

[0036] Step 2: Dissolve 500 g of roasted slag in 1000 mL of NaOH solution with a concentration of 1 mol / L, stir and mix evenly to obtain an electrolyte solution. Use a titanium-based coated DSA as the anode and Ag as the cathode, heat the electrolyte solution to a temperature of 30 °C, and the current density is 450 A / m 2 , and the electrolysis time is 24 h; after the electrolysis is completed, strip, wash, and vacuum-dry the cathode product to obtain 4N-grade crude tellurium;

[0037] Step 3: Perform vacuum distillation on the 4N-grade crude tellurium at a temperature of 450 °C, the vacuum degree of the vacuum distillation is 1.5×10 - 2 Pa, the vacuum distillation time is 6 h to remove low-boiling impurities; first cool down at a cooling rate of 5 °C / min to 400 °C, and then cool down at a cooling rate of 10 °C / min to 350 °C, and condense to obtain 5N-grade tellurium;

[0038] Step 4: Place 5N-grade tellurium in the graphite crucible groove of the wire groove crystallization device. Pump the vacuum inside the housing to below 1.8 Pa through the vacuum port. At the same time, introduce hydrogen into the wire groove crystallization device to make the pressure in the wire groove crystallization device reach 90 kPa. Turn on 5 thermocouples. From left to right, the heating temperature of the first thermocouple is 480 °C, the heating temperature of the second thermocouple is 450 °C, the heating temperature of the third thermocouple is 440 °C, the heating temperature of the fourth thermocouple is 430 °C, and the heating temperature of the fifth thermocouple is 420 °C. Turn on the heating resistor in the graphite crucible groove and set the heating temperature to 500 °C. The 5N-grade tellurium is heated to the molten state in the graphite crucible groove and flows into the wire groove. Since the wire groove is inclined in a V shape, the molten 5N-grade tellurium can flow along the wire groove to the bottom of the wire groove. After gathering at the bottom, part of it flows to the second wire groove. The crystallization gradient temperature formed by the 5 thermocouples gradually decreases, and gradient crystallization is carried out on the molten 5N-grade tellurium. After all the 5N-grade tellurium in the graphite crucible has flowed into the wire groove, turn off the thermocouples one by one. After cooling to room temperature, remove the cover and remove the sample containing impurities in the first calcination section of the wire groove to obtain 7N-grade high-purity tellurium. During the process of the molten 5N-grade tellurium flowing and crystallizing in the wire groove, tellurium crystallizes out first, and the density of tellurium is greater than that of sulfur and selenium. The concentration distribution of tellurium in the wire groove is uneven and mainly concentrated in the middle and rear parts of the V-shaped wire groove. The impurity content at the head end of the wire groove is higher than that in the middle and tail parts. The results show that 7N-grade tellurium can be obtained in the middle of the wire groove with this method and structural setting.

[0039] Example 2

[0040] This example provides a method for preparing high-purity tellurium, including the following steps:

[0041] Step 1: Mix 1000 g of crude tellurium with 1000 g of concentrated sulfuric acid with a mass concentration of 98%, place it in a rotary kiln, roast it at 550 °C for 3 h, and obtain roasted slag after cooling to room temperature.

[0042] Step 2: Dissolve 500 g of roasted slag in 1000 mL of NaOH solution with a concentration of 1 mol / L, stir and mix evenly to obtain an electrolyte. Use a titanium-based coated DSA as the anode and Ag as the cathode. Heat the electrolyte to a temperature of 40 °C, with a current density of 500 A / m 2 , and the electrolysis time is 24 h. After the electrolysis is completed, strip, wash, and vacuum dry the cathode product to obtain 4N-grade crude tellurium;

[0043] Step 3: Carry out vacuum distillation on the 4N-grade crude tellurium at a temperature of 550 °C, and the vacuum degree of vacuum distillation is 1.5×10 - 2Pa, the vacuum distillation time is 5 h to remove low-boiling impurities; first cool down at a rate of 5 °C / min to 440 °C, and then cool down at a rate of 10 °C / min to 400 °C, and condense to obtain 5N-grade tellurium;

[0044] Step 4: Place the 5N-grade tellurium cooled to room temperature in the graphite crucible groove of the wire groove crystallization device, evacuate the vacuum inside the housing to below 1.8 Pa through the vacuum port, and at the same time introduce hydrogen into the wire groove crystallization device to make the pressure in the wire groove crystallization device reach 65 kPa; turn on 5 thermocouples. From left to right, the heating temperature of the first thermocouple is 470 °C, the heating temperature of the second thermocouple is 440 °C, the heating temperature of the third thermocouple is 430 °C, the heating temperature of the fourth thermocouple is 420 °C, and the heating temperature of the fifth thermocouple is 420 °C. Turn on the heating resistor in the graphite crucible groove and set the heating temperature to 480 °C. The 5N-grade tellurium is heated to the molten state in the graphite crucible groove and flows into the wire groove. Since the wire groove is inclined in a V shape, the molten 5N-grade tellurium can flow along the wire groove to the bottom of the wire groove. After gathering at the bottom, part of it flows to the second wire groove. The crystallization gradient temperature with a gradually decreasing gradient formed by the 5 thermocouples performs gradient crystallization on the molten 5N-grade tellurium. After all the 5N-grade tellurium in the graphite crucible has flowed into the wire groove, turn off the thermocouples one by one; after cooling to room temperature, remove the cover, remove the sample containing impurities at the first section of the wire groove, and obtain 7N-grade high-purity tellurium. During the process of the molten 5N-grade tellurium flowing and crystallizing in the wire groove, tellurium crystallizes out first, and the density of tellurium is greater than that of sulfur and selenium, so it is mainly concentrated in the middle of the V-shaped wire groove. The impurity content at the first end of the wire groove is higher than that in the middle and the rear. The results show that 7N-grade tellurium can be obtained in the middle of the wire groove with this method and structural setting.

[0045] Example 3

[0046] This example provides a method for preparing high-purity tellurium, including the following steps:

[0047] Step 1: Mix 1000 g of crude tellurium with 1000 g of concentrated sulfuric acid with a mass concentration of 98%, place it in a rotary kiln, roast at 600 °C for 3 h, and obtain roasted slag after cooling to room temperature.

[0048] Step 2: Dissolve 500 g of roasted slag in 1000 mL of NaOH solution with a concentration of 1 mol / L, stir and mix evenly to obtain an electrolyte solution. Use a titanium-based coated DSA as the anode and Ag as the cathode, heat the electrolyte solution to a temperature of 50 °C, and the current density is 550 A / m 2 , and the electrolysis time is 24 h; after the electrolysis is completed, strip, wash, and vacuum dry the cathode product to obtain 4N-grade crude tellurium;

[0049] Step 3: Vacuum distillation of 4N-grade crude tellurium at a temperature of 550°C, with a vacuum degree of 1.5×10 - 2 Pa, and the vacuum distillation time is 6h to remove low-boiling impurities; first cool down to 440°C at a cooling rate of 5°C / min, and then cool down to 400°C at a cooling rate of 10°C / min to obtain 5N-grade tellurium by condensation;

[0050] Step 4: Place the 5N-grade tellurium cooled to room temperature in the graphite crucible groove of the wire groove crystallization device, evacuate the vacuum degree inside the shell to below 1.8 Pa through the vacuum port, and at the same time introduce hydrogen into the wire groove crystallization device to make the pressure in the wire groove crystallization device reach 85 kPa; turn on 5 thermocouples. From left to right, the heating temperature of the first thermocouple is 480°C, the heating temperature of the second thermocouple is 460°C, the heating temperature of the third thermocouple is 450°C, the heating temperature of the fourth thermocouple is 440°C, and the heating temperature of the fifth thermocouple is 430°C. Turn on the heating resistor in the graphite crucible groove and set the heating temperature to 500°C. The 5N-grade tellurium is heated to a molten state in the graphite crucible groove and flows into the wire groove. Since the wire groove is inclined in a V shape, the molten 5N-grade tellurium can flow along the wire groove to the bottom of the wire groove. After gathering at the bottom, part of it flows to the second wire groove. The crystallization gradient temperature formed by the 5 thermocouples gradually decreases to perform gradient crystallization on the molten 5N-grade tellurium. After all the 5N-grade tellurium in the graphite crucible flows into the wire groove, turn off the thermocouples one by one; after cooling to room temperature, remove the cover, and remove the sample containing impurities at the first section in the wire groove to obtain 7N-grade high-purity tellurium. During the process of the molten 5N-grade tellurium flowing and crystallizing in the wire groove, tellurium crystallizes out first, and the density of tellurium is greater than that of sulfur and selenium, so it is mainly concentrated in the middle of the V-shaped wire groove. The impurity content at the first end of the wire groove is higher than that in the middle and the rear. The results show that 7N-grade tellurium can be obtained in the middle of the wire groove with this method and structural setting.

[0051] Comparative Example 1

[0052] This comparative example provides a method for preparing high-purity tellurium. This comparative example also uses Figure 1 the wire groove crystallization device shown. Different from Example 1, in this comparative example, the heating temperatures of the 5 thermocouples in Step 5 are uniformly set to 450°C.

[0053] The methods and process parameters of the remaining steps in this comparative example are the same as those in Example 1. Finally, after removing the tellurium at the first section in the wire groove in this comparative example, the obtained tellurium is still 5N-grade tellurium.

[0054] Comparative Example 2

[0055] This comparative example provides a method for preparing high-purity tellurium. This comparative example also uses Figure 1The shown wire groove crystallization device, different from that of Embodiment 1, in this comparative example, the heating temperatures of the 5 thermocouples in Step 5 are uniformly set to 480 °C.

[0056] The methods and process parameters of the remaining steps in this comparative example are the same as those in Embodiment 1. Finally, after taking out the first section of tellurium in the wire groove in this comparative example, the obtained tellurium is still 5N grade tellurium.

[0057] The methods and process parameters of the remaining steps in this comparative example are the same as those in Embodiment 1. Finally, after removing the first section of tellurium in the wire groove in this comparative example, the obtained tellurium is still 5N grade tellurium

[0058] The equipment quantities and processing scales described here are used to simplify the description of the present invention. The applications, modifications, and variations of the present invention will be obvious to those skilled in the art.

[0059] Although the embodiments of the present invention have been disclosed as above, it is not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A method for preparing high-purity tellurium, characterized in that: The following steps are involved: Step 1, roasting crude tellurium as a raw material to obtain roasted slag; Step 2: preparing 4N grade crude tellurium by electrolysis using the roasted slag as an electrolyte; Step 3: vacuum distill the 4N grade crude tellurium to remove low boiling point impurities, and condense the 5N grade tellurium using a gradient condensation technique; Step 4: Place the 5N grade tellurium in a wire slot crystallization device for smelting and recrystallization, remove the first impurity sample, and obtain 7N grade high-purity tellurium.

2. The method for preparing high-purity tellurium according to claim 1, characterized in that: The specific method of step one includes: mixing crude tellurium and concentrated sulfuric acid with a mass concentration of 98% in a mass ratio of 1 to 3:1, placing in a rotary kiln, roasting at 350 to 600° C. for 1 to 3 hours, and cooling to room temperature to obtain roasted slag.

3. The method for preparing high-purity tellurium according to claim 1, characterized in that: In the step 2, the specific method of using the calcined slag to prepare the electrolyte includes: dissolving the calcined slag in a 0.5-1 mol / L NaOH solution, stirring and mixing to obtain the electrolyte, and the amount ratio of the calcined slag to the NaOH solution is 1g:2-10mL.

4. The method for preparing high-purity tellurium according to claim 3, characterized in that: In step 2, the specific method for preparing 4N grade crude tellurium by electrolysis includes: using titanium-based coating DSA as an anode and Ag as a cathode, heating the electrolyte to a temperature of 30-50°C and a current density of 450-550A / m 2 , electrolysis time 24 to 72 hours; after the electrolysis is completed, the cathode product is stripped, washed and vacuum dried to obtain 4N grade crude tellurium.

5. The method for preparing high-purity tellurium according to claim 1, characterized in that: In the step 3, the temperature of vacuum distillation for the 4N grade is 450-600°C, and the vacuum degree of vacuum distillation is less than 2.5×10 -2 Pa, the vacuum distillation time is 3 to 8 hours.

6. The method for preparing high-purity tellurium according to claim 1, characterized in that: In the step three, the specific method of the gradient condensation technology includes: first cooling to 400-440°C at a cooling rate of 5-10°C / min, and then cooling to 300-400°C at a cooling rate of 5-10°C / min.

7. The method for preparing high-purity tellurium according to claim 1, characterized in that: In the step 4, the temperature of smelting and recrystallization is 460-560°C.

8. The method for preparing high-purity tellurium according to claim 1, characterized in that: In the step 4, the structure of the wire slot crystallization device includes: A shell, one end of which is provided with a graphite crucible tank for holding and melting 5N grade tellurium, a cover body is sealed on the shell, and one end of the shell is provided with a vacuum port and a vent; A plurality of wire grooves are arranged in a V-shape in the axial direction of the shell, and the width of the wire grooves is 0.5 to 2 mm; the wire grooves include a first wire groove connected to the graphite crucible and a second wire groove connected to the first wire groove, and the connection between the first wire groove and the second wire groove is a smooth connection; A plurality of thermocouples are arranged at intervals at the lower end of the wire slot, the upper surfaces of the thermocouples are in contact with the lower surface of the wire slot, a water cooling pipeline is provided between two adjacent thermocouples, and the water cooling pipeline is in contact with the lower surface of the wire slot.

9. The method for preparing high-purity tellurium according to claim 8, characterized in that: The included angle between the center line of the first wire groove and the axial horizontal line of the shell is 1 to 4 degrees, and the included angle between the center line of the second wire groove and the axial horizontal line of the shell is 4 to 8 degrees.

10. The method for preparing high-purity tellurium according to claim 8, characterized in that: During recrystallization, the heating temperatures of the thermocouples are different, and the heating temperatures of the thermocouples decrease gradually in a direction away from the graphite crucible groove, and the heating temperature range of the thermocouples is 400-500°C.

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