Method for preparing selenium powder by using freezing airflow crushing method

Abstract

The invention belongs to the technical field of powder material preparation, and particularly relates to a method for preparing selenium powder by using a freezing airflow crushing method, and the method comprises the following steps: dissolving selenium oxide in water to form a solution, and adding a reducing agent to carry out a reduction reaction to obtain a mixed solution containing elemental selenium; the mixed solution containing the selenium simple substance is subjected to evaporation, crushing, freezing airflow crushing and grading treatment, and the selenium powder is obtained; the freezing airflow crushing temperature is-40 DEG C to 0 DEG C; the pressure of the freezing air flow crushing is 2 to 15 bar. The method provided by the invention can realize accurate regulation and control of the particle size of the selenium powder, and the prepared selenium powder is uniform in particle size, high in purity and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of powder material preparation technology, specifically relating to a method for preparing selenium powder using a cryogenic airflow pulverization method. Background Technology

[0002] Selenium, as an important semiconductor material, has key applications in photovoltaics, optoelectronics, and agriculture due to its unique photoelectric and chemical properties. In the photovoltaic industry, selenium is a core raw material for preparing high-efficiency cadmium telluride thin-film solar cells, and its particle size and purity directly affect the photoelectric conversion efficiency of the cells. In the optoelectronic field, selenium can be used to manufacture high-performance photodetectors and sensors. In addition, selenium is also widely used in selenium-enriched fertilizers and nutrient additives.

[0003] Currently, the preparation of selenium powder mainly relies on the redox method. Although this method can directly synthesize selenium particles, the products are mostly amorphous and prone to phase transitions and agglomeration during subsequent processing, making it difficult to accurately control the particle size distribution. Furthermore, due to the high viscosity of selenium powder, it easily adheres to the walls during mechanical crushing and grading, causing equipment blockage, reduced efficiency, and a wider particle size distribution, making it difficult to meet the stringent consistency requirements of high-end applications. Existing processes often reduce viscosity by adding dispersants, but this easily introduces impurities, affecting product purity. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing selenium powder by cryogenic airflow pulverization and classification. The method can effectively solve the problems of wall adhesion, agglomeration and difficulty in particle size control caused by high viscosity of selenium powder during pulverization and classification, realize precise control of selenium powder particle size, and obtain selenium powder with uniform particle size, high purity and suitable for large-scale production.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing selenium powder using a cryogenic airflow milling method, comprising the following steps: S1. Add selenium oxide to deionized water and stir until homogeneous to obtain a selenium oxide aqueous solution; S2. Add the reducing agent to the selenium oxide aqueous solution to carry out the reduction reaction and obtain a mixed solution containing elemental selenium. S3. The mixture containing selenium is evaporated and crushed to obtain crude selenium powder; S4. The crude selenium powder is subjected to cryogenic airflow pulverization and classification to obtain the selenium powder.

[0006] The temperature of the refrigerated gas flow pulverizer is -40℃ to 0℃, and can be, for example, but not limited to, -40℃, -39℃, -38℃, -37℃, -36℃, -35℃, -34℃, -33℃, -32℃, -31℃, -30℃, -29℃, -28℃, -27℃, -26℃, -25℃, -24℃, -23℃, -22℃, -21℃, -20℃, -19℃, -18℃, -17℃, -16℃, -15℃, -14℃, -13℃, -12℃, -11℃, -10℃, -9℃, -8℃, -7℃, -6℃, -5℃, -4℃, -3℃, -2℃, -1℃, 0℃, or any two of the above temperatures.

[0007] In some preferred embodiments, the temperature of the cryogenic gas flow pulverizer is -40°C to -20°C, for example, but not limited to -40°C, -39°C, -38°C, -37°C, -36°C, -35°C, -34°C, -33°C, -32°C, -31°C, -30°C, -29°C, -28°C, -27°C, -26°C, -25°C, -24°C, -23°C, -22°C, -21°C, -20°C, or any two of the above temperatures.

[0008] The pressure of the refrigerated gas stream pulverization is 2 to 15 bar, for example, but not limited to 2.0 bar, 2.5 bar, 3.0 bar, 3.5 bar, 4.0 bar, 4.5 bar, 5.0 bar, 5.5 bar, 6.0 bar, 6.5 bar, 7.0 bar, 7.5 bar, 8.0 bar, 8.5 bar, 9.0 bar, 9.5 bar, 10.0 bar, 10.5 bar, 11.0 bar, 11.5 bar, 12.0 bar, 12.5 bar, 13.0 bar, 13.5 bar, 14.0 bar, 14.5 bar, 15.0 bar, or any two of the above pressures.

[0009] In some preferred embodiments, the pressure of the cryogenic gas pulverizer is 8 to 10 bar, for example, but not limited to 8.0 bar, 8.5 bar, 9.0 bar, 9.5 bar, 10.0 bar, or any two of the above pressures.

[0010] In some embodiments, the selenium oxide is dried before use.

[0011] In some embodiments, the drying temperature is 60~100°C, for example, but not limited to 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, or any two of the above temperatures.

[0012] In some embodiments, the drying time is 1 to 5 hours, for example, but not limited to 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, or any range between two of the above times.

[0013] In some embodiments, the concentration of the selenium oxide aqueous solution is (0.5~1) mol / L, for example, but not limited to 0.50 mol / L, 0.52 mol / L, 0.54 mol / L, 0.56 mol / L, 0.58 mol / L, 0.60 mol / L, 0.62 mol / L, 0.64 mol / L, 0.66 mol / L, 0.68 mol / L, 0.70 mol / L, 0.72 mol / L, 0.74 mol / L, 0.76 mol / L, 0.78 mol / L, 0.80 mol / L, 0.82 mol / L, 0.84 mol / L, 0.86 mol / L, 0.88 mol / L, 0.90 mol / L, 0.92 mol / L, 0.94 mol / L, 0.96 mol / L, 0.98 mol / L, 1.00 mol / L, or any range between two of the above concentrations.

[0014] In some implementations, the reducing agent includes hydrazine hydrate.

[0015] In some embodiments, the molar ratio of selenium oxide to reducing agent is 1:(2~3), for example, but not limited to 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3 or any range between two of the above molar ratios.

[0016] In some embodiments, the reduction reaction temperature is 30~60°C, for example, but not limited to 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, or any two of the above temperatures. The reduction reaction can have a suitable reaction rate within the above temperature range, while preventing the selenium powder from agglomerating due to excessively high temperatures, making it difficult to break down and / or pulverize into micron-sized selenium powder.

[0017] In some preferred embodiments, the temperature of the reduction reaction is 30~50°C, for example, but not limited to 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C or any two of the above temperatures.

[0018] In some implementations, the reduction reaction time is 1 to 5 hours, for example, but not limited to 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, or any range between two of the above times.

[0019] In some embodiments, the evaporation is carried out under the protection of an inert gas. The inert gas can be a conventional inert gas in the art, capable of preventing the selenium powder from oxidizing during the evaporation process. The inert gas can be, for example, but is not limited to, at least one of neon, nitrogen, and helium.

[0020] In some embodiments, the crushing involves crushing the blocky selenium powder obtained from the evaporation process. The crushing method can be a conventional method in the art. More preferably, the blocky selenium powder is crushed into coarse selenium powder with a particle size ≤ 5 mm. The coarse selenium powder with this particle size has better pulverization efficiency when used in subsequent cryogenic airflow milling.

[0021] In some implementations, gas is introduced during the cryogenic gas pulverization process.

[0022] In some embodiments, the gas includes at least one of nitrogen or air.

[0023] In some embodiments, the gas flow rate is 2-50 m / s. 3 / min, for example, can be, but is not limited to, 2m 3 / min, 4m 3 / min, 6m 3 / min, 8m 3 / min, 10m3 / min, 12m 3 / min, 14m 3 / min, 16m 3 / min, 18m 3 / min, 20m 3 / min, 22m 3 / min, 24m 3 / min, 26m 3 / min, 28m 3 / min, 30m 3 / min, 32m 3 / min, 34m 3 / min, 36m 3 / min, 38m 3 / min, 40m 3 / min, 42m 3 / min, 44m 3 / min, 46m 3 / min, 48m 3 / min, 50m 3 / min or the range between any two of the above flow rates.

[0024] Under the action of the cooling airflow, the brittleness of the coarse selenium powder increases and its viscosity decreases. It is subjected to strong impact and collision in the crushing chamber and is rapidly crushed into fine particles.

[0025] In some preferred embodiments, the gas flow rate is 2~20m. 3 / min, for example, can be, but is not limited to, 2m 3 / min, 2.5m 3 / min, 3m 3 / min, 3.5m 3 / min, 4m 3 / min, 4.5m 3 / min, 5m 3 / min, 5.5m 3 / min, 6m 3 / min, 6.5m 3 / min, 7m 3 / min, 7.5m 3 / min, 8m 3 / min, 8.5m 3 / min、9 m 3 / min, 9.5m 3 / min, 10m 3 / min, 10.5m 3 / min, 11m 3 / min, 11.5m 3 / min, 12m 3 / min, 12.5m 3 / min, 13m 3 / min, 13.5m 3 / min, 14m 3 / min, 14.5m 3 / min, 15m 3 / min, 15.5m 3 / min, 16m 3 / min, 16.5m 3 / min, 17m 3 / min, 17.5m 3 / min, 18m 3 / min, 18.5m 3 / min, 19m 3 / min, 19.5m 3 / min, 20m 3 / min or the range between any two of the above flow rates.

[0026] In some embodiments, the grading process includes at least one of airflow grading and turbine grading. When turbine grading is used, the grading particle size can be adjusted by regulating the rotational speed of the turbine.

[0027] A second aspect of the present invention provides a selenium powder, which is prepared by the above method.

[0028] Compared with the prior art, the present invention has the following beneficial effects: This invention prepares selenium powder through reduction reaction, evaporation, crushing, cryogenic airflow pulverization, and classification. In particular, pulverization at low temperature effectively increases the brittleness of the selenium powder and reduces its stickiness, effectively solving the problems of wall adhesion, agglomeration, and difficulty in particle size control caused by high stickiness during the pulverization and classification process. It achieves precise control of the particle size of micron-sized selenium powder and obtains micron-sized selenium powder with uniform particle size, high purity, and suitable for large-scale production. At the same time, it effectively improves production efficiency and equipment stability, and is especially suitable for the large-scale production of high-quality micron-sized selenium powder. Attached Figure Description

[0029] Figure 1 The image shows the electron microscope morphology of the micron-sized selenium powder prepared in Example 1.

[0030] Figure 2 The particle size distribution of the micron-sized selenium powder prepared in Example 1 is shown in the figure.

[0031] Figure 3 The image shows the electron microscope morphology of the micron-sized selenium powder prepared in Example 2.

[0032] Figure 4 The particle size distribution diagram is shown for the micron-sized selenium powder prepared in Example 2. Detailed Implementation

[0033] The following detailed embodiments further illustrate the content of the present invention. These embodiments do not constitute a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention. The raw materials, reagents, or devices used in the embodiments are all available from conventional commercial sources or can be obtained through existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0034] Example 1 S1. Place selenium oxide in a vacuum oven and dry it at 80°C for 2 hours. Weigh the dried selenium oxide and add it to deionized water to prepare a 0.5 mol / L selenium oxide aqueous solution.

[0035] S2. Under nitrogen protection, hydrazine hydrate solution is slowly added dropwise to the solution at a rate of 20 mL / min until the molar ratio of selenium oxide to hydrazine hydrate in the system is 1:2. The reaction temperature is controlled at 50℃ and the reaction is carried out for 2 hours. The reaction endpoint is determined by measuring the pH value (pH>7) to obtain a mixed solution containing elemental selenium.

[0036] S3. Transfer the above mixture to an evaporation device, purge with nitrogen gas at a rate of 1 L / min for protection, and evaporate at 80°C until all moisture is evaporated to obtain lumpy selenium powder. Crush the lumpy selenium powder and pass it through a 40-mesh sieve to obtain coarse selenium powder.

[0037] S4. Feed the selenium coarse powder into a cryogenic airflow mill, use a silicone oil compressor to lower the temperature of the milling chamber to -20℃, and use freeze-dried nitrogen as the medium to mill at a depth of 5m. 3 The coarse selenium powder is pulverized at a gas flow rate of / min and an air pressure of 8 bar. The pulverized material then enters a turbine classifier, where the particle size is controlled by adjusting the speed of the classifying wheel, and micron-sized selenium powder is collected.

[0038] The micron-sized selenium powder obtained in Example 1 was observed using a field emission scanning electron microscope, and tested using a laser particle size analyzer (dry method). The results are as follows: Figure 1 , Figure 2 As shown.

[0039] The micron-sized selenium powder was tested and found to have a D50 of 4.194 μm, a D97 of 10.58 μm, and a purity of 99.99%.

[0040] Example 2 S1. Place selenium oxide in a vacuum oven and dry it at 80℃ for 5 hours. Weigh the dried selenium oxide and add it to deionized water to prepare a 1mol / L selenium oxide aqueous solution.

[0041] S2. Under nitrogen protection, hydrazine hydrate solution is slowly added dropwise to the solution at a rate of 40 mL / min until the molar ratio of selenium oxide to hydrazine hydrate in the system is 1:3. The reaction temperature is controlled at 30℃ and the reaction is carried out for 4 hours. The reaction endpoint is determined by measuring the pH value (pH>7) to obtain a mixed solution containing elemental selenium.

[0042] S3. Transfer the above mixture to an evaporation device, purge with nitrogen at a rate of 2 L / min for protection, and evaporate at 80°C until all moisture is evaporated to obtain lumpy selenium powder. Crush the lumpy selenium powder and pass it through a 100-mesh sieve to obtain coarse selenium powder.

[0043] S4. The coarse selenium powder is fed into a refrigerated airflow mill. The temperature of the milling chamber is lowered to -40°C using a silicone oil compressor. Freeze-dried nitrogen is used as the medium, and the milling process is carried out at a depth of 6.5m. 3 The coarse selenium powder is pulverized at a gas flow rate of / min and an air pressure of 10 bar. The pulverized material then enters a turbine classifier, where the particle size is controlled by adjusting the speed of the classifying wheel, and micron-sized selenium powder is collected.

[0044] The micron-sized selenium powder obtained in Example 1 was observed using a field emission scanning electron microscope, and tested using a laser particle size analyzer (dry method). The results are as follows: Figure 3 , Figure 4 As shown.

[0045] The micron-sized selenium powder was tested and found to have a D50 of 1.674 μm, a D100 of 3.052 μm, and a purity of 99.99%.

[0046] Comparative Example 1 The only difference from Example 1 is that in step S2, the reduction reaction temperature is 80°C, while the other components and steps are exactly the same as in Example 1.

[0047] Testing revealed that the micron-sized selenium powder had a D50 of 9.386 μm, a D100 of 35.977 μm, and a purity of 99.99%, but its particle size distribution was too wide.

[0048] Comparative Example 2 The only difference from Example 1 is that in step S4, the silicone oil compressor is turned on to maintain the ambient temperature at 25°C, while the other components and steps are exactly the same as in Example 1.

[0049] Testing revealed that the micron-sized selenium powder had a D50 of 13.141 μm, a D100 of 65.371 μm, and a purity of 99.99%, but its particle size distribution was too wide.

[0050] Comparative Example 3 The only difference from Example 1 is that no pulverization is performed after the evaporation process. The specific steps are as follows: S1. Place selenium oxide in a vacuum oven and dry it at 80°C for 2 hours. Weigh the dried selenium oxide and add it to deionized water to prepare a 0.5 mol / L selenium oxide aqueous solution.

[0051] S2. Under nitrogen protection, hydrazine hydrate solution is slowly added dropwise to the solution at a rate of 20 mL / min until the molar ratio of selenium oxide to hydrazine hydrate in the system is 1:2. The reaction temperature is controlled at 50℃ and the reaction is carried out for 2 hours. The reaction endpoint is determined by measuring the pH value (pH>7) to obtain a mixed solution containing elemental selenium.

[0052] S3. Transfer the above mixture to an evaporation device, introduce nitrogen gas at a rate of 1 L / min for protection, and evaporate at 80°C until all moisture is evaporated to obtain block selenium powder.

[0053] S4. The lumpy selenium powder is fed into a cryogenic airflow mill. The temperature of the milling chamber is lowered to -20°C using a silicone oil compressor. Freeze-dried nitrogen is used as the medium, and the mixture is milled at a depth of 5m. 3 The coarse selenium powder is pulverized at a gas flow rate of / min and an air pressure of 8 bar. The pulverized material then enters a turbine classifier, where the particle size is controlled by adjusting the speed of the classifying wheel, and micron-sized selenium powder is collected.

[0054] Testing revealed that the micron-sized selenium powder had a D50 of 25.844 μm and a D100 exceeding 1 mm, making it difficult to completely pulverize, with an excessively wide particle size distribution and a purity of 99.99%.

[0055] Comparing Example 1 and Comparative Example 3, it is evident that the lumpy selenium powder obtained after evaporation is a large, unevenly shaped, hard agglomerate. If it is not pre-crushed before being fed into the cryogenic airflow mill, these large, hard agglomerates have a low probability of being impacted by the airflow, resulting in poor pulverization efficiency, longer powder output time, and a wide particle size distribution and poor uniformity in the final selenium powder. Furthermore, since the lumpy selenium powder obtained after evaporation is not pre-crushed, some areas within it may still remain that have not been fully embrittled at low temperatures due to stickiness. This makes it more prone to localized blockages or adhesion to the walls during pulverization, further reducing pulverization efficiency and even compromising the machine's operational stability.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing selenium powder by a freeze stream pulverization method, characterized by, Includes the following steps: S1. Add selenium oxide to deionized water and stir until homogeneous to obtain a selenium oxide aqueous solution; S2. Add the reducing agent to the selenium oxide aqueous solution to carry out the reduction reaction and obtain a mixed solution containing elemental selenium. S3. The mixture containing selenium is evaporated and crushed to obtain crude selenium powder; S4. The crude selenium powder is subjected to cryogenic airflow pulverization and classification to obtain the selenium powder; The temperature of the cryogenic gas pulverizer is -40℃ to 0℃; The pressure of the refrigerated gas flow pulverizer is 2~15 bar.

2. The method of claim 1, wherein, The temperature of the refrigerated airflow pulverizer is -40℃ to -20℃.

3. The method of claim 1, wherein, The selenium oxide is dried before use, and the drying temperature is 60~100℃, and the drying time is 1~5h.

4. The method of claim 1, wherein, The concentration of the selenium oxide aqueous solution is (0.5~1) mol / L.

5. The method of claim 1, wherein, The molar ratio of selenium oxide to reducing agent is 1:(2~3); the reducing agent includes hydrazine hydrate.

6. The method of claim 1, wherein, The reduction reaction is carried out at a temperature of 30-60°C for 1-5 hours.

7. The method of claim 1, wherein, The evaporation is carried out under an inert atmosphere.

8. The method as described in claim 1, characterized in that, The gas is introduced during the cryogenic jet milling process; the gas comprises at least one of nitrogen or air; the gas has a flow rate of 2 to 50 m 3 / min.

9. The method as described in claim 1, characterized in that, The graded processing includes at least one of airflow grading and turbine grading.

10. A selenium powder, characterized in that, The selenium powder is prepared by the method described in any one of claims 1 to 9.

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