System and method for purifying trichlorosilane for producing electronic-grade polycrystalline silicon

Abstract

The invention belongs to the technical field of semiconductors, and particularly relates to a trichlorosilane purification system and method for electronic-grade polycrystalline silicon production, and the trichlorosilane purification system comprises a coarse separation rectifying tower which is used for removing a first light component and a first heavy component in a hydrogenation incoming material to obtain a first mixture, the first mixture comprises trichlorosilane, silicon tetrachloride and methyl dichlorosilane; the first-stage rectifying tower is connected with the coarse separation rectifying tower and is used for separating trichlorosilane in the first mixture to obtain a trichlorosilane crude product and a second mixture, and the second mixture comprises silicon tetrachloride and methyl dichlorosilane; and the refining unit is connected with the primary rectifying tower and is used for refining and rectifying the trichlorosilane crude product to obtain purified trichlorosilane. According to the system, methyl dichlorosilane is enriched in silicon tetrachloride by virtue of interaction of silicon tetrachloride and methyl dichlorosilane, so that a relatively large removal amount of trichlorosilane is avoided, meanwhile, the quality fluctuation of trichlorosilane is reduced, and the purity of trichlorosilane is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a trichlorosilane purification system and method for the production of electronic-grade polysilicon. Background Technology

[0002] In the modified Siemens process for producing polycrystalline silicon, SiCl4, H2, and silicon powder are regenerated into SiHCl3 through a hydrogenation process. The directly obtained product (i.e., the hydrogenated feedstock) is typically a mixture of dichlorosilane, trichlorosilane, and silicon tetrachloride. This mixture needs to be sent to a distillation system for purification. The trichlorosilane undergoes multi-stage distillation to achieve a highly pure, qualified product, which is then sent to a reduction furnace for polycrystalline silicon production. In related technologies, the distillation process usually involves first obtaining crude trichlorosilane through coarse fractionation, followed by continuous distillation to purify the crude trichlorosilane. Because industrial silicon powder contains carbon impurities, the carbon is converted into organic carbon, primarily methyldichlorosilane, during the hydrogenation process. Methyldichlorosilane has a boiling point close to that of trichlorosilane and relatively lower volatility, making it difficult to remove from trichlorosilane. This results in the difficulty of obtaining high-purity trichlorosilane for the production of electronic-grade polycrystalline silicon. Furthermore, a large amount of material needs to be removed to remove methyldichlorosilane from trichlorosilane, leading to raw material waste and increased processing costs. Additionally, if the removed trichlorosilane continues to circulate in the system, it can easily cause impurity accumulation, leading to fluctuations in trichlorosilane quality and ultimately affecting the quality of the polycrystalline silicon. Therefore, trichlorosilane purification technology still requires improvement. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a trichlorosilane purification system and method for the production of electronic-grade polycrystalline silicon, which can effectively separate trichlorosilane and methyldichlorosilane.

[0004] In a first aspect, this application provides a trichlorosilane purification system. According to an embodiment of this application, the trichlorosilane purification system includes: a crude distillation column for removing a first light component and a first heavy component from a hydrogenated feedstock to obtain a first mixture, the first mixture comprising trichlorosilane, silicon tetrachloride, and methyldichlorosilane; a primary distillation column connected to the crude distillation column for separating trichlorosilane from the first mixture to obtain crude trichlorosilane and a second mixture, the second mixture comprising silicon tetrachloride and methyldichlorosilane; and a purification unit connected to the primary distillation column for refining and distilling the crude trichlorosilane to obtain purified trichlorosilane. In this trichlorosilane purification system, the first light component, including dichlorosilane, is collected from the top of the column, the first heavy component is collected from the bottom, and the first mixture is collected from the side stream. This first mixture is then fed to a primary distillation column to separate trichlorosilane and silicon tetrachloride. Crude trichlorosilane is collected from the top of the primary distillation column, and silicon tetrachloride rich in methyldichlorosilane is collected from the bottom. The solution formed by methyldichlorosilane and silicon tetrachloride exhibits strong non-ideal properties. During the separation process, silicon tetrachloride has a "dragging" or "retention" effect on methyldichlorosilane, thereby reducing the volatility of methyldichlorosilane and making the separation of methyldichlorosilane and trichlorosilane easier. A better separation effect can be achieved using fewer theoretical plates, without causing the removal of trichlorosilane, reducing raw material waste and processing costs. Further purification yields trichlorosilane with higher purity, which can reduce polysilicon quality fluctuations and improve polysilicon quality when used in production.

[0005] According to an embodiment of this application, the primary distillation column includes a feed inlet and a makeup inlet. The feed inlet is connected to the crude fractionation column and is used to input the first mixture into the primary distillation column. The makeup inlet is located above the feed inlet and is used to input silicon tetrachloride into the primary distillation column. Thus, by adding silicon tetrachloride into the primary distillation column through the makeup inlet, a silicon tetrachloride distribution is formed in the liquid phase of the primary distillation column. This allows for better utilization of the "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane, thereby facilitating the separation of methyldichlorosilane and trichlorosilane and further improving the purity of trichlorosilane.

[0006] According to an embodiment of this application, the trichlorosilane purification system further includes a deimpurification unit disposed between the crude distillation column and the primary distillation column, for removing impurities from the first mixture, the deimpurification unit comprising at least one of the following: A dephosphorization unit is used to remove phosphorus-containing impurities from the first mixture; A deboron removal unit is used to remove boron-containing impurities from the first mixture.

[0007] According to an embodiment of this application, the impurity removal unit includes a dephosphorization unit and a deboronization unit. The dephosphorization unit is disposed between the crude fractionation distillation column and the deboronization unit, and the deboronization unit is disposed between the dephosphorization unit and the primary distillation column. This further removes impurities from trichlorosilane, improving the purity of the trichlorosilane.

[0008] According to an embodiment of this application, the dephosphorization unit includes a dephosphorization adsorption column packed with a phosphorus removal adsorbent. This provides good selectivity, allows for deep dephosphorization, and yields trichlorosilane that meets the production requirements of electronic-grade polycrystalline silicon. Furthermore, the process can be carried out under mild conditions of low temperature and low pressure, resulting in low energy consumption, no introduction of new impurities, and regenerable resin, leading to low operating costs.

[0009] According to embodiments of this application, the boron removal unit includes a boron removal adsorption column packed with a boron removal adsorbent. This allows for deep dephosphorization, yielding trichlorosilane that meets the production requirements of electronic-grade polycrystalline silicon. The process can be carried out under mild conditions of low temperature and low pressure, resulting in low energy consumption, no introduction of new impurities, and regenerable resin, leading to low operating costs. This significantly reduces boron impurity content while maintaining almost constant energy consumption, thereby minimizing equipment investment and maintenance costs associated with high reflux.

[0010] According to embodiments of this application, the refining unit includes at least one set of refining distillation columns, each set of refining distillation columns including a light component removal column and a heavy component removal column connected in sequence. This further removes light component impurities (i.e., light impurities) and heavy component impurities (i.e., heavy impurities) from trichlorosilane, further improving the purity of trichlorosilane and meeting the requirements for electronic-grade polysilicon production.

[0011] According to an embodiment of this application, the trichlorosilane purification system further includes a carbon removal unit connected to the primary distillation column, used to remove methyldichlorosilane from the second mixture to obtain silicon tetrachloride. Thus, carbon tetrachloride and methyldichlorosilane can be separated to obtain carbon tetrachloride with higher purity for further recycling.

[0012] According to an embodiment of this application, the carbon removal unit is connected to the makeup port of the primary distillation column, and is used to deliver silicon tetrachloride to the primary distillation column. This allows for the recycling of carbon tetrachloride, reducing costs and waste discharge.

[0013] According to an embodiment of this application, the trichlorosilane purification system further includes: a mixer connected to the crude distillation column and the decarbonization unit, used to mix the first light component and the silicon tetrachloride to obtain a third mixture; and a disproportionation device connected to the mixer and the crude distillation column, used to disproportionate the third mixture and convey the resulting disproportionation product to the crude distillation column. Thus, low-value, high-hazard dichlorosilane and excess silicon tetrachloride can be simultaneously converted into high-value trichlorosilane, reducing byproducts, significantly reducing the "ineffective flow" of the distillation system, lowering material and energy consumption, significantly reducing carbon emissions, and simultaneously solving the safety and environmental problems caused by dichlorosilane enrichment.

[0014] A second aspect of this application provides a method for purifying trichlorosilane. According to an embodiment of this application, the method includes: performing a crude distillation process on a hydrogenated feedstock to remove a first light component and a first heavy component, obtaining a first mixture comprising trichlorosilane, silicon tetrachloride, and methyldichlorosilane; performing a primary distillation process on the first mixture to separate the trichlorosilane from the first mixture, obtaining crude trichlorosilane and a second mixture, the second mixture comprising silicon tetrachloride and methyldichlorosilane; and performing a refining distillation process on the crude trichlorosilane to obtain purified trichlorosilane. In this method, during the coarse distillation step, a first mixture containing trichlorosilane, silicon tetrachloride, and methyldichlorosilane is separated together, and then trichlorosilane is separated from the first mixture. The "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane can be utilized to reduce the volatility of methyldichlorosilane, making the separation of methyldichlorosilane and trichlorosilane easier. A better separation effect can be achieved with fewer theoretical plates, while avoiding the removal of trichlorosilane, reducing raw material waste and processing costs. Through further purification, the obtained trichlorosilane has higher purity, which can reduce polysilicon quality fluctuations and improve polysilicon quality when used in polysilicon production.

[0015] According to an embodiment of this application, the method further includes: during the first-stage distillation process, contacting the second light component moving towards the top of the column with silicon tetrachloride to remove methyldichlorosilane from the second light component. This allows for a more efficient utilization of the "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane, resulting in better separation of trichlorosilane and methyldichlorosilane.

[0016] According to an embodiment of this application, after the crude distillation process and before the first-stage distillation process, the method further includes: performing a deimpurification treatment on the first mixture, wherein the deimpurification treatment includes at least one of a dephosphorization treatment and a deboration treatment. Specifically, the deimpurification treatment includes the dephosphorization treatment and the deboration treatment performed sequentially. This further removes impurities from trichlorosilane and improves the purity of trichlorosilane.

[0017] According to embodiments of this application, the refining distillation process includes multiple sub-distillation processes, each of which includes sequential removal of light and heavy components. This further removes both light and heavy component impurities from trichlorosilane, thereby improving the purity of trichlorosilane and meeting the requirements for electronic-grade polysilicon production.

[0018] According to embodiments of this application, the method further includes: subjecting the second mixture to a decarbonization treatment to remove methyldichlorosilane from the second mixture, obtaining silicon tetrachloride. Thus, carbon tetrachloride and methyldichlorosilane can be separated to obtain carbon tetrachloride with higher purity for further recycling.

[0019] According to embodiments of this application, the method further includes: mixing the first light component and the silicon tetrachloride to obtain a third mixture; subjecting the third mixture to disproportionation treatment to obtain a disproportionation product, and using the disproportionation product as the raw material for the crude fraction distillation treatment. Thus, low-value, high-hazard dichlorosilane and excess silicon tetrachloride can be simultaneously converted into high-value trichlorosilane, reducing byproducts, significantly reducing the "ineffective flow" of the distillation system, lowering material and energy consumption, and significantly reducing carbon emissions. Simultaneously, it can solve the safety and environmental problems caused by the enrichment of dichlorosilane. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a trichlorosilane purification system according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the structure of a trichlorosilane purification system according to another embodiment of this application.

[0022] Figure 3 This is a schematic diagram of the structure of a trichlorosilane purification system according to another embodiment of this application. Detailed Implementation

[0023] The embodiments of the present invention described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] This application is based on the inventor's discoveries and understanding of the following facts and problems: In the modified Siemens process for producing polycrystalline silicon, SiCl4, H2, and silicon powder are regenerated into SiHCl3 through a hydrogenation process. The directly obtained product (i.e., the hydrogenated feedstock) is typically a mixture of dichlorosilane, trichlorosilane, and silicon tetrachloride. This mixture needs to be sent to a distillation system for purification. The trichlorosilane undergoes multi-stage distillation to obtain a high-purity, qualified product, which is then sent to a reduction furnace for polycrystalline silicon production. In related technologies, the distillation process usually involves first obtaining crude trichlorosilane through coarse fractionation, followed by continuous distillation to purify the crude trichlorosilane. Because industrial silicon powder contains carbon impurities, the carbon is converted into organic carbon, mainly methyldichlorosilane, during the hydrogenation process. Methyldichlorosilane has a boiling point close to that of trichlorosilane and relatively low volatility, making it difficult to remove from trichlorosilane. This results in the difficulty of obtaining high-purity trichlorosilane for the production of electronic-grade polycrystalline silicon. Furthermore, a large amount of material needs to be removed to remove methyldichlorosilane from trichlorosilane, leading to raw material waste and increased processing costs. In addition, if the removed trichlorosilane continues to circulate in the system, it can easily cause impurity accumulation, leading to fluctuations in the quality of trichlorosilane and ultimately affecting the quality of polycrystalline silicon.

[0025] To address the aforementioned issues, the inventors discovered that the solution formed by methyldichlorosilane and silicon tetrachloride exhibits strong non-ideal properties. During the separation process, silicon tetrachloride can exert a "dragging" or "retention" effect on methyldichlorosilane, and the presence of silicon tetrachloride reduces the volatility of methyldichlorosilane. Consequently, under the condition of silicon tetrachloride, the separation of methyldichlorosilane and trichlorosilane becomes easier, requiring fewer theoretical plates in the column to achieve the same separation effect. At the same time, it does not lead to the removal of trichlorosilane, reducing raw material waste and processing costs.

[0026] In view of this, the first aspect of this application provides a trichlorosilane purification system. According to an embodiment of this application, referring to... Figure 1The trichlorosilane purification system includes: a crude distillation column 10 for removing a first light component and a first heavy component from the hydrogenated feedstock to obtain a first mixture, the first mixture including trichlorosilane, silicon tetrachloride and methyldichlorosilane; a primary distillation column 20 connected to the crude distillation column 10 for separating trichlorosilane from the first mixture to obtain crude trichlorosilane and a second mixture, the second mixture including silicon tetrachloride and methyldichlorosilane; and a purification unit 30 connected to the primary distillation column 20 for refining and distilling the crude trichlorosilane to obtain purified trichlorosilane. In this trichlorosilane purification system, the first light component, including dichlorosilane, is collected from the top of the column, the first heavy component is collected from the bottom, and the first mixture is collected from the side stream. This first mixture is then fed to a primary distillation column to separate trichlorosilane and silicon tetrachloride. Crude trichlorosilane is collected from the top of the primary distillation column, and silicon tetrachloride rich in methyldichlorosilane is collected from the bottom. The solution formed by methyldichlorosilane and silicon tetrachloride exhibits strong non-ideal properties. During the separation process, silicon tetrachloride has a "dragging" or "retention" effect on methyldichlorosilane, thereby reducing the volatility of methyldichlorosilane and making the separation of methyldichlorosilane and trichlorosilane easier. A better separation effect can be achieved using fewer theoretical plates, without causing the removal of trichlorosilane, reducing raw material waste and processing costs. Further purification yields trichlorosilane with higher purity, which can reduce polysilicon quality fluctuations and improve polysilicon quality when used in production.

[0027] In this article, hydrogenated feedstock refers to a mixture of dichlorosilane, trichlorosilane, silicon tetrachloride, and methyl dichlorosilane synthesized in the hydrogenation process during the production of polycrystalline silicon using the modified Siemens process.

[0028] According to embodiments of this application, the crude distillation column can be a plate column, a packed column, a wall-mounted column, a thermally coupled column, etc. Specifically, the crude distillation column collects the first light component (such as dichlorosilane) with a boiling point lower than trichlorosilane from the top of the column, collects the first heavy component with a boiling point higher than silicon tetrachloride from the bottom of the column, and collects the mixture containing trichlorosilane, silicon tetrachloride, and methyldichlorosilane (boiling point between trichlorosilane and silicon tetrachloride) from the side stream. The crude distillation column collects trichlorosilane and silicon tetrachloride from the same side stream, resulting in good separation of the first light component and the first heavy component, small amount of trichlorosilane removed, and facilitates better separation of trichlorosilane and methyldichlorosilane in subsequent steps through the "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane. This improves the purity of trichlorosilane while reducing the amount of trichlorosilane removed.

[0029] In some embodiments, reference is made to Figure 1The crude distillation column 10 may be provided with a hydrogenated feed inlet 101 in the middle, a first light component outlet 102 at the top of the crude distillation column 10, a first heavy component outlet 103 at the bottom of the crude distillation column 10, and a first mixture outlet 104 in the middle of the crude distillation column 10.

[0030] According to embodiments of this application, the specific type of the primary distillation column is not particularly limited and can be a plate column, packed column, wall-mounted column, thermally coupled column, etc. In some embodiments, the primary distillation column can be a plate column, specifically at least one of sieve plate column, valve column, bubble cap column, and tongue column. Therefore, it offers high throughput, stable stage efficiency, wide operational flexibility, anti-clogging, easy maintenance, low cost, and long service life. Furthermore, the primary distillation column can efficiently separate trichlorosilane. Specifically, the first mixture contains trichlorosilane, silicon tetrachloride, and methyldichlorosilane. While separating trichlorosilane, silicon tetrachloride has a "dragging" or "retention" effect on methyldichlorosilane, thereby better separating trichlorosilane and methyldichlorosilane. This improves the purity of trichlorosilane while reducing the amount of trichlorosilane removed, thus reducing raw material waste and processing costs.

[0031] According to embodiments of this application, the theoretical plate number of the primary distillation column is 20 to 200, specifically 20, 50, 80, 100, 120, 150, 180, 200, or any range between two of these. Therefore, better separation performance can be achieved with a lower theoretical plate number.

[0032] According to the embodiments of this application, referring to Figure 1 The primary distillation column 20 includes a feed inlet 210 and a replenishment inlet 220. The feed inlet 210 is connected to the crude fractionation column 10 and is used to input the first mixture into the primary distillation column 20. The replenishment inlet 220 is located above the feed inlet 210 and is used to input silicon tetrachloride into the primary distillation column 20. Thus, by replenishing the primary distillation column with silicon tetrachloride through the replenishment inlet, a silicon tetrachloride distribution is formed in the liquid phase of the primary distillation column. This allows for better utilization of the "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane, thereby facilitating the separation of methyldichlorosilane and trichlorosilane and further improving the purity of trichlorosilane.

[0033] According to the embodiments of this application, referring to Figure 2 The trichlorosilane purification system further includes a deimpurification unit 40, which is disposed between the crude distillation column 10 and the primary distillation column 20, and is used to remove impurities from the first mixture. The deimpurification unit 40 includes at least one of the following: a dephosphorization unit 41, used to remove phosphorus-containing impurities from the first mixture; and a deboronization unit 42, used to remove boron-containing impurities from the first mixture.

[0034] According to the embodiments of this application, referring to Figure 2 The impurity removal unit 40 includes the dephosphorization unit 41 and the deboronization unit 42. The dephosphorization unit 41 is disposed between the crude fractionation distillation column 10 and the deboronization unit 42, and the deboronization unit 42 is disposed between the dephosphorization unit 41 and the primary distillation column 20. This further removes impurities from trichlorosilane, improving its purity.

[0035] According to an embodiment of this application, the dephosphorization unit includes a dephosphorization adsorption column packed with a phosphorus removal adsorbent. This provides good selectivity, allows for deep dephosphorization, and yields trichlorosilane that meets the production requirements of electronic-grade polycrystalline silicon. Furthermore, the process can be carried out under mild conditions of low temperature and low pressure, resulting in low energy consumption, no introduction of new impurities, and regenerable resin, leading to low operating costs.

[0036] According to embodiments of this application, the type of phosphorus removal adsorbent is not particularly limited, and includes, but is not limited to, at least one of chelating / anion exchange resins, supported amine silica gel, metal oxide-type phosphorus removal adsorbents, activated alumina / activated carbon, and bio-mineral composite adsorbents. Therefore, it has a specific coordination effect on phosphorus-containing species such as PH3 and PCl3 in trichlorosilane, exhibiting high selectivity, good adsorption capacity, and better removal effect on phosphorus-containing impurities.

[0037] According to embodiments of this application, the boron removal unit includes a boron removal adsorption column packed with a boron removal adsorbent. This allows for deep dephosphorization, yielding trichlorosilane that meets the production requirements of electronic-grade polycrystalline silicon. The process can be carried out under mild conditions of low temperature and low pressure, resulting in low energy consumption, no introduction of new impurities, and regenerable resin, leading to low operating costs. This significantly reduces boron impurity content while maintaining almost constant energy consumption, thereby minimizing equipment investment and maintenance costs associated with high reflux.

[0038] According to embodiments of this application, the type of boron-removing adsorbent is not particularly limited, and includes, but is not limited to, at least one of amine / polyhydroxy resins, amines supported on inorganic porous supports, lanthanide-modified adsorbents, magnetic core-shell adsorbents, and modified carbon-based materials. Therefore, it exhibits high selectivity, good adsorption capacity, and better removal of boron-containing impurities.

[0039] According to the embodiments of this application, referring to Figure 1 The refining unit 30 includes at least one set of refining distillation columns 310, each set of refining distillation columns 310 including a light component removal column 311 and a heavy component removal column 312 connected in sequence. This further removes light and heavy component impurities from trichlorosilane, further improving the purity of trichlorosilane and meeting the requirements for electronic-grade polysilicon production.

[0040] According to the embodiments of this application, referring to Figure 2The trichlorosilane purification system further includes a carbon removal unit 50, which is connected to the primary distillation column 20 and is used to remove methyldichlorosilane from the second mixture to obtain silicon tetrachloride. Thus, carbon tetrachloride and methyldichlorosilane can be separated to obtain purified carbon tetrachloride for further recycling.

[0041] According to embodiments of this application, since methyldichlorosilane is enriched in silicon tetrachloride, and silicon tetrachloride is a non-polar substance while methyldichlorosilane is a polar substance, it is more easily captured by adsorption. Therefore, the carbon removal unit includes a carbon removal adsorption column, which is filled with a carbon removal adsorbent. This allows for deep carbon removal, the obtained silicon tetrachloride can be reused, and the process can be carried out under mild conditions of low temperature and low pressure, resulting in low energy consumption, no introduction of new impurities, and regenerable resin, leading to low operating costs.

[0042] According to embodiments of this application, the carbon removal adsorbent includes at least one of molecular sieves, silica gel, resin, and γ-alumina. Therefore, the adsorption effect on methyldichlorosilane is better, and the carbon removal effect can be further improved.

[0043] According to an embodiment of this application, the carbon removal unit is connected to the makeup port of the primary distillation column, and is used to deliver silicon tetrachloride to the primary distillation column. This allows for the recycling of carbon tetrachloride, reducing costs and waste discharge.

[0044] According to the embodiments of this application, referring to Figure 3 The trichlorosilane purification system further includes: a mixer 60, connected to the crude distillation column 10 and the carbon removal unit 50, for mixing the first light component and the silicon tetrachloride to obtain a third mixture; and a disproportionation device 70, connected to the mixer 60 and the crude distillation column 10, for disproportionating the third mixture and conveying the resulting disproportionated product to the crude distillation column 10. Thus, low-value, high-hazard dichlorosilane and excess silicon tetrachloride can be simultaneously converted into high-value trichlorosilane, reducing byproducts, significantly reducing the "ineffective flow" of the distillation system, lowering material and energy consumption, and significantly reducing carbon emissions. It also addresses the safety and environmental concerns caused by dichlorosilane enrichment.

[0045] A second aspect of this application provides a method for purifying trichlorosilane. According to an embodiment of this application, the method includes: performing a crude distillation process on a hydrogenated feedstock to remove a first light component and a first heavy component, obtaining a first mixture comprising trichlorosilane, silicon tetrachloride, and methyldichlorosilane; performing a primary distillation process on the first mixture to separate the trichlorosilane from the first mixture, obtaining crude trichlorosilane and a second mixture, the second mixture comprising silicon tetrachloride and methyldichlorosilane; and performing a refining distillation process on the crude trichlorosilane to obtain purified trichlorosilane. In this method, during the coarse distillation step, a first mixture containing trichlorosilane, silicon tetrachloride, and methyldichlorosilane is separated together, and then trichlorosilane is separated from the first mixture. The "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane can be utilized to reduce the volatility of methyldichlorosilane, making the separation of methyldichlorosilane and trichlorosilane easier. A better separation effect can be achieved with fewer theoretical plates, while avoiding the removal of trichlorosilane, reducing raw material waste and processing costs. Through further purification, the obtained trichlorosilane has higher purity, which can reduce polysilicon quality fluctuations and improve polysilicon quality when used in polysilicon production.

[0046] According to an embodiment of this application, the method further includes: during the first-stage distillation process, contacting the second light component moving towards the top of the column with silicon tetrachloride to remove methyldichlorosilane from the second light component. This allows for a more efficient utilization of the "dragging" or "retention" effect of silicon tetrachloride on methyldichlorosilane, resulting in better separation of trichlorosilane and methyldichlorosilane.

[0047] According to an embodiment of this application, after the crude distillation process and before the first-stage distillation process, the method further includes: performing a deimpurification treatment on the first mixture, wherein the deimpurification treatment includes at least one of a dephosphorization treatment and a deboration treatment. Specifically, the deimpurification treatment includes the dephosphorization treatment and the deboration treatment performed sequentially. This further removes impurities from trichlorosilane and improves the purity of trichlorosilane.

[0048] According to embodiments of this application, the refining distillation process includes multiple sub-distillation processes, each of which includes sequential removal of light and heavy components. This further removes both light and heavy component impurities from trichlorosilane, thereby improving the purity of trichlorosilane and meeting the requirements for electronic-grade polysilicon production.

[0049] According to embodiments of this application, the method further includes: subjecting the second mixture to a decarbonization treatment to remove methyldichlorosilane from the second mixture, obtaining silicon tetrachloride. Thus, carbon tetrachloride and methyldichlorosilane can be separated to obtain purified carbon tetrachloride for further recycling.

[0050] According to embodiments of this application, the method further includes: mixing the first light component and the silicon tetrachloride to obtain a third mixture; subjecting the third mixture to disproportionation treatment to obtain a disproportionation product, and using the disproportionation product as the raw material for the crude fraction distillation treatment. Thus, low-value, high-hazard dichlorosilane and excess silicon tetrachloride can be simultaneously converted into high-value trichlorosilane, reducing byproducts, significantly reducing the "ineffective flow" of the distillation system, lowering material and energy consumption, and significantly reducing carbon emissions. Simultaneously, it can address the safety and environmental concerns caused by the enrichment of dichlorosilane.

[0051] It is understood that the trichlorosilane purification method of the second aspect of this application can be implemented using the trichlorosilane purification system of the first aspect, and the specific operation can be consistent with the above description, and will not be repeated here.

[0052] The following reference Figure 3 The following is a detailed example illustrating the specific steps of implementing the trichlorosilane purification method of the second aspect of this application using the trichlorosilane purification system of the first aspect of this application: The product from the hydrogenation process in the improved Siemens polysilicon production process (i.e., the hydrogenated feedstock) is fed to a roughing distillation column 10. After roughing distillation, the first light component with a boiling point lower than trichlorosilane is collected from the top of the column, and the first heavy component with a boiling point higher than silicon tetrachloride is collected from the bottom of the column. The first mixture containing trichlorosilane, methyldichlorosilane, and silicon tetrachloride is collected from the side stream. The first mixture then passes through a dephosphorization unit 41 and a deboronization unit 42 to remove phosphorus and boron impurities. The purified first mixture then enters the primary distillation column 10 to separate trichlorosilane from the first mixture. In this step, silicon tetrachloride can effectively separate methyldichlorosilane from trichlorosilane through a "dragging" or "retention" effect on it. Methyldichlorosilane tends to concentrate in silicon tetrachloride. The top of the primary distillation column yields crude trichlorosilane, while the bottom yields a second mixture containing silicon tetrachloride and methyldichlorosilane. The crude trichlorosilane enters the refining unit 30, where it passes through a light impurity removal column and a heavy impurity removal column to further remove light and heavy impurities, resulting in highly purified trichlorosilane that meets the stringent requirements for electronic-grade polysilicon production. The second mixture then enters the carbon removal unit, where the difference in polarity and molecular size between methyldichlorosilane and silicon tetrachloride is utilized to remove methyldichlorosilane through an adsorption process, yielding high-purity carbon tetrachloride. The obtained carbon tetrachloride can be fed back into the primary distillation column to promote the separation of trichlorosilane and methyldichlorosilane, or it can be mixed with the first light component in a mixer and then fed into a disproportionation unit to undergo a disproportionation reaction to generate trichlorosilane, which is then fed into the crude distillation column as a raw material for recycling.

[0053] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0056] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A trichlorosilane purification system, characterized in that, include: A crude distillation column is used to remove the first light component and the first heavy component from the hydrogenated feed to obtain a first mixture, the first mixture comprising trichlorosilane, silicon tetrachloride and methyl dichlorosilane; A primary distillation column, connected to the crude distillation column, is used to separate trichlorosilane from the first mixture to obtain crude trichlorosilane and a second mixture, wherein the second mixture includes silicon tetrachloride and methyl dichlorosilane. The refining unit, connected to the primary distillation column, is used to refine and distill the crude trichlorosilane to obtain purified trichlorosilane.

2. The trichlorosilane purification system according to claim 1, characterized in that, The primary distillation column includes a feed inlet and a makeup inlet. The feed inlet is connected to the crude fractionation column and is used to input the first mixture into the primary distillation column. The makeup inlet is located above the feed inlet and is used to input silicon tetrachloride into the primary distillation column.

3. The trichlorosilane purification system according to claim 1, characterized in that, It also includes a purification unit disposed between the crude distillation column and the primary distillation column, for removing impurities from the first mixture, the purification unit comprising at least one of the following: A dephosphorization unit is used to remove phosphorus-containing impurities from the first mixture; A boron removal unit is used to remove boron-containing impurities from the first mixture; Preferably, the impurity removal unit includes the dephosphorization unit and the deboron removal unit, the dephosphorization unit being disposed between the crude fractionation distillation column and the deboron removal unit, and the deboron removal unit being disposed between the dephosphorization unit and the primary distillation column.

4. The trichlorosilane purification system according to claim 3, characterized in that, At least one of the following conditions must be met: The dephosphorization unit includes a dephosphorization adsorption column filled with a phosphorus removal adsorbent; The boron removal unit includes a boron removal adsorption column filled with a boron removal adsorbent.

5. The trichlorosilane purification system according to claim 1, characterized in that, The refining unit includes at least one set of refining distillation columns, each set of refining distillation columns including a light-light removal column and a heavy-light removal column connected in sequence.

6. The trichlorosilane purification system according to claim 1, characterized in that, Also includes: A carbon removal unit, connected to the primary distillation column, is used to remove methyl dichlorosilane from the second mixture to obtain silicon tetrachloride.

7. The trichlorosilane purification system according to claim 6, characterized in that, The carbon removal unit is connected to the replenishment port of the first-stage distillation column and is used to transport silicon tetrachloride to the first-stage distillation column.

8. The trichlorosilane purification system according to claim 7, characterized in that, Also includes: A mixer, connected to the crude distillation column and the decarbonization unit, is used to mix the first light component and the silicon tetrachloride to obtain a third mixture; The disproportionation device, connected to the mixer and the crude distillation column, is used to disproportionate the third mixture and to transport the resulting disproportionated product to the crude distillation column.

9. A method for purifying trichlorosilane, characterized in that, include: The hydrogenated feedstock is subjected to coarse distillation to remove the first light component and the first heavy component, resulting in a first mixture, which includes trichlorosilane, silicon tetrachloride and methyl dichlorosilane. The first mixture is subjected to primary distillation to separate trichlorosilane from the first mixture, yielding crude trichlorosilane and a second mixture, the second mixture comprising silicon tetrachloride and methyl dichlorosilane; The crude trichlorosilane was purified by distillation to obtain purified trichlorosilane.

10. The method according to claim 9, characterized in that, Also includes: During the first-stage distillation process, the second light component moving towards the top of the column is contacted with silicon tetrachloride to remove methyl dichlorosilane from the second light component.

11. The method according to claim 9, characterized in that, After the crude fractionation process and before the first-stage distillation process, the process further includes: The first mixture is subjected to a deimpurification treatment, which includes at least one of a dephosphorization treatment and a deboration treatment, preferably the deimpurification treatment includes the dephosphorization treatment and the deboration treatment performed sequentially.

12. The method according to claim 9, characterized in that, The refining and distillation process includes multiple sub-distillation processes, each of which includes sequential removal of light and heavy components.

13. The method according to claim 9, characterized in that, Also includes: The second mixture is subjected to a decarbonization treatment to remove methyl dihydrosilane from the second mixture, yielding silicon tetrachloride.

14. The method according to claim 13, characterized in that, Also includes: The first light component and the silicon tetrachloride are mixed to obtain a third mixture; The third mixture is subjected to anti-disproportionation treatment to obtain an anti-disproportionation product, which is then used as the raw material for the crude fractionation distillation treatment.

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