Method for testing conversion rate of cold hydrogenation reaction and application

Abstract

The invention relates to the field of polycrystalline silicon production, in particular to a method for testing the conversion rate of a cold hydrogenation reaction and application, and the method comprises the following steps: after carrying out adsorption treatment, drying treatment, washing treatment and screening treatment on raw material silicon powder, calculating the activity constant gamma of the silicon powder to be tested according to a formula shown in a formula (1), the conversion rate of the cold hydrogenation reaction is calculated according to the formula shown in the formula (2), the accuracy of the conversion rate, obtained through testing, of the cold hydrogenation reaction is high, and meanwhile the activity of the silicon powder can be further predicted. Formula (1): Activity Constant Gamma = I (111) / [0.217 * I (220) + 0.116 * I (311)] Formula (2): Eta = 0.04 Gamma.

Description

Technical Field

[0001] The present invention relates to the field of polysilicon production, and particularly to a test method and application for the conversion rate of the cold hydrogenation reaction. Background Art

[0002] The activity of silicon powder in polysilicon production refers to the reaction activity of silicon powder in the cold hydrogenation process or trichlorosilane synthesis, which can directly affect the efficiency and product quality of the cold hydrogenation process and trichlorosilane synthesis. High-activity silicon powder has the advantages of improving the reaction conversion rate, optimizing the use of catalysts, controlling product quality, and reducing side reactions. Therefore, the accurate determination of the activity of silicon powder is of great significance.

[0003] There are mainly two existing methods for determining the activity of silicon powder. One is to measure the reaction rate of silicon powder with sodium hydroxide, such as in patent documents CN220829481U and CN213181133U; the other is the method disclosed in patent document CN116183836A, in which silicon tetrachloride, silicon powder of different specifications are added into a high-temperature and high-pressure autoclave and filled with high-purity hydrogen to simulate production, and finally the activity of silicon powder is evaluated by detecting the content of trichlorosilane in the silane liquid after the reaction and the metal impurities and silicon content of the remaining silicon powder.

[0004] However, the existing solutions still have some problems such as low accuracy, complex processes, and inability to provide timely feedback. For example, in the aforementioned detection method of measuring the reaction rate of silicon powder with sodium hydroxide, considering the reaction kinetics, the reaction mechanisms of the cold hydrogenation reaction process, trichlorosilane synthesis process and sodium hydroxide reaction process are completely different. Silicon powder with high reactivity with sodium hydroxide cannot be considered to have high reactivity in the cold hydrogenation process or trichlorosilane synthesis process. Another example is the method of evaluating the activity of silicon powder by detecting the content of trichlorosilane in the silane liquid after the reaction and the metal impurities and silicon content of the remaining silicon powder, which has problems such as complex reaction processes, long time consumption, high cost, a large amount of silicon powder required for cold hydrogenation production, inability to obtain the required silicon powder activity data in a timely manner, and inability to guide production in a timely manner. The inventor found that by testing the conversion rate of the cold hydrogenation reaction, the activity of silicon powder can be fed back in a timely manner. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art, and provide a test method for the conversion rate of the cold hydrogenation reaction, which has high accuracy, simple process and can timely feedback the activity result of silicon powder.

[0006] To achieve the above purpose, on the one hand, the present invention provides a test method for the conversion rate of the cold hydrogenation reaction, the method comprising:

[0007] (1) Adsorbing, drying and washing the raw material silicon powder in sequence to obtain intermediate I;

[0008] (2) Screen and process the intermediate I according to the following particle size range;

[0009] The particle size range includes: D 10 > 20 μm, D 50 is 50 - 100 μm, D 90 < 200 μm;

[0010] (3) Test the I of the silicon powder to be tested (111) 、I (220) and I (311) , and calculate the activity constant γ of the silicon powder to be tested according to the formula shown in Equation (1);

[0011] Equation (1): Activity constant γ = I (111) / [0.217×I (220) +0.116×I (311) ;

[0012] Among them, I (111) is the light intensity at the (111) crystal plane of the silicon powder to be tested; I (220) is the light intensity at the (220) crystal plane of the silicon powder to be tested; I (311) is the light intensity at the (311) crystal plane of the silicon powder to be tested;

[0013] (4) Calculate the conversion rate η of the cold hydrogenation reaction in the polysilicon production process according to the formula shown in Equation (2);

[0014] Equation (2): η = 0.04γ.

[0015] The second aspect of the present invention provides an application of the above-mentioned test method for the conversion rate of the cold hydrogenation reaction in the field of polysilicon production.

[0016] Through the above technical solution, the activity constant γ of the silicon powder to be tested is calculated by using the formula shown in Equation (1), and the conversion rate η of the cold hydrogenation reaction in the polysilicon production process is calculated by using the formula shown in Equation (2), which can accurately predict the conversion rate of the cold hydrogenation reaction in the actual polysilicon production process, further can correctly evaluate the activity of the silicon powder, and then can select the appropriate type of silicon powder for the subsequent process, ensure the efficient progress of the reaction, reduce the maintenance time and improve the overall product quality. Description of the Drawings

[0017] Figure 1 is the X-ray diffraction pattern of silicon powder A1 in Example 1;

[0018] Figure 2 is the X-ray diffraction pattern of silicon powder A2 in Example 2;

[0019] Figure 3 is the X-ray diffraction pattern of silicon powder A3 in Example 3. Detailed implementation manners

[0020] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0021] On the one hand, the present invention provides a method for testing the conversion rate of the cold hydrogenation reaction, and the method includes:

[0022] (1) Adsorbing, drying, and washing the raw material silicon powder in sequence to obtain intermediate I;

[0023] (2) Screening the intermediate I according to the following particle size range;

[0024] The particle size range includes: D 10 > 20 μm, D 50 is 50 - 100 μm, D 90 < 200 μm;

[0025] (3) Testing I (111) , I (220) and I (311) of the silicon powder to be tested, and calculating the activity constant γ of the silicon powder to be tested according to the formula shown in formula (1);

[0026] Formula (1): Activity constant γ = I (111) / [0.217×I (220) +0.116×I (311) ;

[0027] Wherein, I (111) is the light intensity at the (111) crystal plane of the silicon powder to be tested; I (220) is the light intensity at the (220) crystal plane of the silicon powder to be tested; I (311) is the light intensity at the (311) crystal plane of the silicon powder to be tested;

[0028] (4) Calculating the conversion rate η of the cold hydrogenation reaction in the polysilicon production process according to the formula shown in formula (2);

[0029] Formula (2): η = 0.04γ.

[0030] In the present invention, the light intensities at the (111) crystal plane, (220) crystal plane, and (311) crystal plane of the silicon powder are all relative intensities, which are dimensionless values after normalization processing.

[0031] In the present invention, in the polysilicon production process, the cold hydrogenation reaction refers to the adsorption of silicon tetrachloride and hydrogen on the surface of the silicon crystal and the adsorption of hydrogen chloride on the surface of the silicon crystal to generate trichlorosilane, as shown in formulas (a) and (b) respectively;

[0032] Formula (a): SiCl4 + H2 → SiHCl3 + HCl;

[0033] Formula (b): 3HCl + Si → SiHCl3 + H2.

[0034] It can be known that the adsorption reaction activity on the surface of the silicon crystal has an important influence on the cold hydrogenation reaction. The inventor found that the change in the conversion rate of the cold hydrogenation reaction is closely related to the activity of the silicon powder. Generally speaking, when η = 0 - 20%, the activity of the silicon powder is poor; when 20% < η < 28%, the activity of the silicon powder is average; when η = 28 - 40%, the activity of the silicon powder is good.

[0035] Thus, it can be seen that when γ < 5, the activity of the silicon powder is poor; when 5 < γ < 7, the activity of the silicon powder is moderate; when γ ≥ 7, the activity of the silicon powder is good.

[0036] By adopting the above calculation scheme, a cold hydrogenation conversion rate with relatively high accuracy is predicted. Based on this, the activity of the raw material silicon powder can be predicted, enabling it to be better applied in the field of polysilicon production.

[0037] In the present invention, the inventor found that the (111) crystal plane promotes the activity of the silicon powder. The (220) crystal plane and the (311) crystal plane have a weak contribution to the activity and an inhibitory effect on the activity of the silicon powder due to the dense atomic arrangement or low surface energy. Based on this, the inventor constructed the calculation formula for the activity of the silicon powder shown in formula (1).

[0038] In the present invention, preferably, before the adsorption treatment, the silicon powder is also reduced in amount by using a splitter.

[0039] In the present invention, in order to efficiently remove impurities in the silicon powder and improve the subsequent detection effect, preferably, the adsorption treatment includes: using an adsorbent to perform adsorption treatment on the silicon powder; the adsorbent is selected from at least one of ethyl acetate, ethanol, and butanol.

[0040] In the present invention, preferably, the mass ratio of the amount of the raw material silicon powder to the amount of the adsorbent used is 1:10 - 20. For example, pure ethyl acetate can be used, or ethyl acetate and ethanol with a volume ratio of 3:1 can be used as the adsorbent.

[0041] In the present invention, preferably, the conditions of the adsorption treatment include: the temperature is 20 - 40°C, and the time is 1 - 5 h.

[0042] In the present invention, preferably, the adsorption treatment is a staged adsorption treatment, which may include: the first adsorption stage: soaking the silicon powder with an adsorbent at 20 - 40 °C for 0.5 - 1 h; the second adsorption stage: soaking the raw material silicon powder with an adsorbent at 20 - 40 °C for 1 - 3 h.

[0043] In the present invention, preferably, the conditions of the drying treatment include: the pressure is 2 - 20 kPa, the temperature is 40 - 100 °C, and the time is 0.5 - 4 h.

[0044] In the present invention, preferably, before the drying treatment, nitrogen bubbling replacement is also carried out for 10 - 30 min to prevent the pollution of the instrument by volatile organic compounds, promote the subsequent drying treatment of the silicon powder, and reduce the solvent residue.

[0045] In the present invention, preferably, the flow rate of nitrogen is 0.4 - 1 L / min, and for example, it can be values such as 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, and 1 L / min and the ranges between any of these values.

[0046] In the present invention, preferably, the drying treatment is a staged drying treatment, including: the conditions of the first drying treatment include: the pressure is 5 - 15 kPa, the temperature is 40 - 60 °C, and the time is 1 - 3 h; the conditions of the second drying treatment include: the pressure is 2 - 10 kPa, the temperature is 60 - 80 °C, and the time is 0.5 - 1.5 h.

[0047] In the present invention, preferably, the post-treatment of the drying treatment includes: replacing with nitrogen at room temperature.

[0048] In the present invention, preferably, the washing treatment includes: washing the product after the drying treatment with a detergent; the detergent is selected from ethanol and / or butanol.

[0049] To ensure complete washing, the conditions for the end of the washing treatment include: until no white smoke is generated on the surface of the silicon powder, it is regarded as the end of the washing treatment.

[0050] In the present invention, preferably, the particle size range includes: D 10 is 30 - 80 μm, D 50 is 60 - 90 μm, D 90 is 100 - 130 μm.

[0051] According to the present invention, the silicon powder can be waste silicon powder obtained from the polysilicon production process. For example, it can be the silicon powder discharged from the polysilicon production system after participating in the polysilicon production process. The surface of this waste silicon powder contains chlorosilane and has certain corrosiveness.

[0052] The second aspect of the present invention provides an application of the test method for the conversion rate of the cold hydrogenation reaction in the polysilicon production process.

[0053] In the present invention, the application in the polysilicon production field may include: when the activity constant γ of the silicon powder calculated by the formula shown in formula (1) ≤ 5, the silicon powder cannot be separately put into the polysilicon production process for use and needs to be mixed with silicon powder with γ > 5. The mixing ratio can be 1:5 - 10. For example, the silicon powder with γ = 4.39 is mixed with the silicon powder with γ = 6.87 in a ratio of 1:5, and then applied to the polysilicon production process.

[0054] The present invention will be described in detail below through examples.

[0055] Example 1

[0056] This example is used to illustrate the test method for the conversion rate of the cold hydrogenation reaction, including:

[0057] (1) Take 200 g of cold hydrogenation outer cyclone outer discharged silicon powder and use a riffle divider to reduce it to 5 g;

[0058] (2) Perform adsorption treatment, drying treatment, and washing treatment on the silicon powder in step (1) to obtain intermediate I1, including:

[0059] (2-1) At 40 °C, first soak 5 g of silicon powder in 50 ml of ethyl acetate and ethanol with a volume ratio of 3:1, ultrasonically vibrate for 30 min, and then place it in 50 ml of pure ethyl acetate for 90 min;

[0060] (2-2) Bubble and displace the product in step (2-1) with nitrogen at a flow rate of 0.5 L / min for 15 min;

[0061] (2-3) Perform drying treatment on the product in step (2-2), including: drying at 50 °C / 10 kPa for 2 h, then drying at 80 °C / 5 kPa for 1 h, and then performing nitrogen displacement at room temperature for 1 h;

[0062] (2-4) Wash the product in step (2-3) with ethanol until no white smoke is generated on the surface of the silicon powder to prepare silicon powder a1;

[0063] (3) Screen the silicon powder in intermediate I1 according to the following particle size ranges, and the silicon powder obtained after screening is denoted as A1; wherein, the particle size ranges are: D 10 is 40 - 50 μm, D 50 is 75 - 85 μm, D 90 is 120 - 130 μm.

[0064] Example 2

[0065] Using a method similar to that of Example 1, except that the silicon powder pretreatment step (2) is not carried out, and the prepared silicon powder is denoted as A2.

[0066] Example 3

[0067] Using a method similar to that of Example 1, except that the silicon powder screening step (3) is not carried out, and the prepared silicon powder is denoted as A3.

[0068] Test Example 1

[0069] This test example is used to test the light intensity of the silicon powder prepared in the examples at the (111), (220), and (311) crystal planes, as shown in Table 1 specifically. Figures 1 - 3 as shown;

[0070] Test method: Use XRD to test the X-ray diffraction pattern of the silicon powder.

[0071] Table 1

[0072] Silica powder number <![CDATA[I (111) > <![CDATA[I (220) > <![CDATA[I (311) > A1 6007 4117 4093 A2 5950 4185 4132 A3 5857 4246 4198

[0073] Test Example 2

[0074] This test example is used to test the accuracy of the test method for the conversion rate of the cold hydrogenation reaction of the present invention, including: calculating the activity constant γ of the silicon powder, calculating the conversion rate η of the cold hydrogenation reaction, and testing the conversion rate η' of the cold hydrogenation reaction under laboratory conditions. By calculating the relative deviation between the conversion rate η and the conversion rate η', the accuracy of the test method for the conversion rate of the cold hydrogenation reaction of the present invention is judged, as shown in Table 2 specifically;

[0075] Test method:

[0076] 1. Calculate the activity constant γ of the silicon powder through Equation (1);

[0077] 2. Calculate the cold hydrogenation conversion rate η through Equation (2);

[0078] 3. Test the cold hydrogenation conversion rate η' under laboratory conditions, specifically as follows:

[0079] (1) Use 5 kg of fresh industrial silicon powder, and carry out a cold hydrogenation experiment with a raw material H / SiCl molar ratio of 3:1. Record the initial partial pressure P (initial STC) of silicon tetrachloride entering the reactor and the partial pressure P (unconverted STC) of unreacted silicon tetrachloride after the reaction; among them, the laboratory conditions include: the temperature is 550 °C ± 5 °C, and the pressure is 30 bar ± 0.1 bar;

[0080] (2) According to the cold hydrogeneration conversion rate formula η’ = [(P(initial STC) - P(unconverted STC)) / P(initial STC)] × 100%, the cold hydrogeneration conversion rate measured in the cold hydrogeneration experiment under laboratory conditions was calculated to be 17.62%;

[0081] 4. Relative deviation = (conversion rate η’ - conversion rate η) / conversion rate η’ × 100%.

[0082] Table 2

[0083] Silica powder number Activity constant γ Conversion rate η / % Conversion rate η' / % Relative deviation / % A1 4.39 17.56 17.62 0.3 A2 4.29 17.16 17.62 2.6 A3 4.17 16.68 17.62 5.3

[0084] It can be seen from the results in Table 2 that in Examples 1-3, the relative deviation between the cold hydrogeneration conversion rate η calculated by formula (2) and the cold hydrogeneration conversion rate η’ under laboratory conditions is less than 6%. That is, the test method for the conversion rate of the cold hydrogeneration reaction of the present invention can accurately detect the actual conversion rate of the cold hydrogeneration reaction. In particular, Example 1, which has undergone adsorption treatment, drying treatment, washing treatment, and screening treatment, has significantly better accuracy.

[0085] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A test method for the conversion rate of the cold hydrogenation reaction, characterized in that, The method includes: (1) sequentially subjecting raw material silicon powder to adsorption treatment, drying treatment, and washing treatment to obtain intermediate I; (2) performing screening treatment on the intermediate I according to the following particle size range; The particle size range includes: D 10 > 20 μm, D 50 is 50 - 100 μm, D 90 < 200 μm; (3) Test the I of the silicon powder to be tested (111) , I (220) and I (311) , and calculate the activity constant γ of the silicon powder to be tested according to the formula shown in formula (1); Equation (1): Activity constant γ = I (111) / [0.217 × I (220) + 0.116 × I (311) ; Among them, I (111) is the light intensity at the (111) crystal plane of the silicon powder to be measured; I (220) is the light intensity at the (220) crystal plane of the silicon powder to be measured; I (311) is the light intensity at the (311) crystal plane of the silicon powder to be measured; (4) calculating the conversion rate η of the cold hydrogenation reaction in the polysilicon production process according to the formula shown in formula (2); Formula (2): η = 0.04γ.

2. The method according to claim 1, wherein, The adsorption treatment includes: using an adsorbent to perform adsorption treatment on the raw material silicon powder; the adsorbent is selected from at least one of ethyl acetate, ethanol, and butanol; Preferably, the mass ratio of the amount of the raw material silicon powder to the adsorbent is 1:10 - 20.

3. The method according to claim 1 or 2, wherein The conditions of the adsorption treatment include: the temperature is 20 - 40°C, and the time is 1 - 5 h.

4. The method according to claim 3, wherein The adsorption treatment is a staged adsorption treatment, including: the first adsorption stage: soaking the silicon powder with the adsorbent at 20 - 40°C for 0.5 - 1 h; and / or, the second adsorption stage: soaking the raw material silicon powder with the adsorbent at 20 - 40°C for 1 - 3 h.

5. The method according to any one of claims 1-4, wherein, The conditions of the drying treatment include: the pressure is 2 - 20 kPa, the temperature is 40 - 100°C, and the time is 0.5 - 4 h.

6. The method according to claim 5, wherein The drying treatment is a staged drying treatment, including: The conditions of the first drying treatment include: the pressure is 5 - 15 kPa, the temperature is 40 - 60°C, and the time is 1 - 3 h; and / or, the conditions of the second drying treatment include: the pressure is 2 - 10 kPa, the temperature is 60 - 80°C, and the time is 0.5 - 1.5 h.

7. The method according to any one of claims 1-6, wherein, The washing treatment includes: using a detergent to perform washing treatment on the product after the drying treatment; the detergent is selected from ethanol and / or butanol.

8. The method according to any one of claims 1-7, wherein, The particle size range includes: D 10 is 30 - 80 μm, D 50 is 60 - 90 μm, D 90 is 100 - 130 μm.

9. The method according to any one of claims 1 to 8, wherein The raw material silicon powder is waste silicon powder obtained from the polysilicon production process.

10. Application of the method according to any one of claims 1 - 9 in the field of polysilicon production.

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