System and method for removing high and low boilers in polycrystalline silicon production

Abstract

The invention provides a system and a method for removing high and low boilers in polycrystalline silicon production. A first rectifying tower in the system comprises a rectifying section at the top, a stripping section at the bottom and a separation section located between the rectifying section and the stripping section, the rectifying section, the separation section and the stripping section are sequentially communicated with one another, and the separation section comprises a pre-fractionation section and a main fractionation section which are arranged in parallel and are not communicated with each other; the main fractionation section sequentially comprises a first main fractionation section and a second main fractionation section which are communicated with each other from top to bottom; the pre-fractionation section is provided with a low-boiling-point material feed port, the stripping section is provided with a bottom discharge port, and the first main fractionation section is provided with a first discharge port; the second rectifying tower is provided with a high-boiling material feed port and a top discharge port, and the bottom discharge port of the stripping section is communicated with the high-boiling material feed port; and the first discharge hole and a top discharge hole of the second rectifying tower are respectively communicated with the adsorption column. According to the system, high-boiling-point substances and low-boiling-point substances in the polycrystalline silicon production process can be efficiently removed, and the production quality of polycrystalline silicon can be improved.

Description

Technical Field

[0001] The present invention relates to a system and method for removing high and low boilers in polysilicon production, belonging to the technical field of chemical separation. Background Art

[0002] With the continuous development of the photovoltaic industry, the competition in the polysilicon market has become increasingly fierce, putting sudden pressure on the survival of polysilicon manufacturers. Therefore, polysilicon manufacturers can only have market competitiveness by continuously improving product quality.

[0003] The improved Siemens method is one of the main processes for producing polysilicon. In the process of producing polysilicon by the improved Siemens method, the impurities in polysilicon mainly include metal impurities (such as Fe, Ca, Al, Ti, Cu, etc.) and non-metal impurities (such as B, P, C, N, etc.). Among them, metal impurities can generally be removed by rectification, but the existence forms of non-metal impurities (B, P, C, etc.) are complex, and their chemical properties are similar to those of chlorosilanes, making it difficult to remove them by ordinary rectification. At present, P and B in trichlorosilane production are mainly removed by extraction, complexation, adsorption, partial hydrolysis, etc.; the carbon impurities in polysilicon mainly come from methylchlorosilanes in trichlorosilane. Since the boiling point of methyldichlorosilane (41.9 °C) is very close to the boiling point of trichlorosilane (31.8 °C), it is difficult to remove by conventional rectification.

[0004] Therefore, it is necessary to provide a system capable of efficiently removing high and low boilers in polysilicon production to improve the quality of polysilicon. Summary of the Invention

[0005] The present invention provides a system for removing high and low boilers in polysilicon production, which can efficiently remove high boilers and low boilers in the polysilicon production process and improve the production quality of polysilicon.

[0006] The present invention provides a method for removing high and low boilers in polysilicon production, which is carried out using the above system. This method can efficiently remove high boilers and low boilers in the polysilicon production process and improve the production quality of polysilicon.

[0007] The first aspect of the present invention provides a system for removing high and low boilers in polysilicon production, which includes a first rectification column, a second rectification column, and an adsorption column;

[0008] The first distillation column includes a rectifying section at the top, a stripping section at the bottom, and a separation section located between the rectifying section and the stripping section. The rectifying section, the separation section, and the stripping section communicate with each other in sequence. The separation section includes a pre-fractionation section and a main fractionation section arranged in parallel and not communicating with each other. The main fractionation section includes a first main fractionation section and a second main fractionation section that communicate with each other from top to bottom in sequence. The pre-fractionation section has a low-boiling material feed port, the stripping section has a bottom discharge port, and the first main fractionation section has a first discharge port.

[0009] The second distillation column has a high-boiling material feed port and a top discharge port. The bottom discharge port of the stripping section communicates with the high-boiling material feed port.

[0010] The first discharge port and the top discharge port of the second distillation column are respectively connected to the adsorption column.

[0011] The low-boiling material includes silicon tetrachloride, trichlorosilane, and dichlorosilane.

[0012] The high-boiling material includes trichlorosilane, silicon tetrachloride, and methyldichlorosilane.

[0013] For the system as described above, the system further includes a first heat exchanger. The second main fractionation section has a second discharge port.

[0014] The second discharge port communicates with the heat source inlet of the first heat exchanger. The low-boiling material communicates with the cold source inlet of the first heat exchanger. The cold source outlet of the first heat exchanger communicates with the low-boiling material feed port.

[0015] For the system as described above, the system further includes a second heat exchanger.

[0016] The top discharge port of the second distillation column communicates with the heat source inlet of the second heat exchanger. The bottom discharge port of the first distillation column communicates with the cold source inlet of the second heat exchanger. The heat source outlet of the second heat exchanger communicates with the adsorption column. The cold source outlet of the second heat exchanger communicates with the stripping section.

[0017] For the system as described above, in the high-boiling material, the content of methyldichlorosilane is 1-100 ppm.

[0018] For the system as described above, in the first distillation column, the operating pressure is 0.15-0.3 MPaG, the operating temperature at the top of the column is 35-52 °C, and the operating temperature at the bottom of the column is 93-110 °C.

[0019] For the system as described above, in the second distillation column, the operating pressure is 0.65-0.95 MPaG, the operating temperature at the top of the column is 106-122 °C, and the operating temperature at the bottom of the column is 109-124 °C.

[0020] The system as described above, wherein the reflux ratio of the second rectification column is 5 - 15.

[0021] The system as described above, wherein in the adsorption column, the operating temperature is 20 - 60 °C and the operating pressure is 0.5 - 1 MPaG.

[0022] The system as described above, wherein the top of the adsorption column has a top feed inlet, and the first discharge port and the top discharge port of the second rectification column are respectively communicated with the top feed inlet of the adsorption column.

[0023] The present invention provides a method for removing high and low boilers in polysilicon production, wherein the system as described above is used.

[0024] The present invention provides a system for removing high and low boilers in polysilicon production. The system includes a first rectification column, a second rectification column and an adsorption column which are connected to each other. Among them, the first rectification column is a dividing wall column, which can separate the light and heavy components in the low-boiling material in one column, improving the separation efficiency; the second rectification column is mainly used for concentrating the high-boiling components, and the adsorption column is used for adsorbing the impurities in the trichlorosilane obtained after the separation of the first rectification column and the second rectification column, so as to obtain high-purity trichlorosilane. The present invention realizes the recovery of high and low boilers in polysilicon production through a system including a first rectification column, a second rectification column 2 and an adsorption column 3, which can reduce equipment investment, floor area and energy consumption, and has a wide application prospect.

[0025] The present invention provides a method for removing high and low boilers in polysilicon production, which is carried out using the above system. Therefore, this method can remove the high boilers and low boilers in polysilicon production, so as to obtain high-purity trichlorosilane. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a system for removing high and low boilers in polysilicon production in some embodiments of the present invention.

[0028] Description of the reference numerals:

[0029] 2: Second rectification column;

[0030] 3: Adsorption column;

[0031] 4: First heat exchanger;

[0032] 5: Second heat exchanger;

[0033] 11: Rectifying section;

[0034] 12: Stripping section;

[0035] 13: Prefractionation section;

[0036] 141: First main fractionation section;

[0037] 142: Second main fractionation section. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Figure 1 For the system for removing high and low boilers in polysilicon production in some embodiments of the present invention, as Figure 1 shown, a first aspect of the present invention provides a system for removing high and low boilers in polysilicon production, including a first rectifying tower, a second rectifying tower 2 and an adsorption column 3;

[0040] The first rectifying tower includes a rectifying section 11 at the top, a stripping section 12 at the bottom, and a separation section located between the rectifying section 11 and the stripping section 12. The rectifying section 11, the separation section, and the stripping section 12 are sequentially and mutually communicated. The separation section includes a prefractionation section 13 and a main fractionation section arranged in parallel and not communicated with each other. The main fractionation section includes a first main fractionation section 141 and a second main fractionation section 142 that are mutually communicated from top to bottom in sequence; the prefractionation section 13 has a low-boiling material feed port, the stripping section 12 has a bottom discharge port, and the first main fractionation section 141 has a first discharge port;

[0041] The second rectifying tower 2 has a high-boiling material feed port and a top discharge port, and the bottom discharge port of the stripping section 12 is communicated with the high-boiling material feed port;

[0042] The first discharge port and the top discharge port of the second rectifying tower 2 are respectively communicated with the adsorption column 3;

[0043] The low-boiling materials include silicon tetrachloride, trichlorosilane, and dichlorosilane;

[0044] The high-boiling materials include trichlorosilane, silicon tetrachloride, and methyldichlorosilane.

[0045] It can be understood that the low-boiling materials of the present invention also include some impurities, and the high-boiling materials also include some impurities.

[0046] The present invention does not make any special limitations on the second rectification column 2. The second rectification column 2 can be a rectification column commonly used in the art. Exemplarily, the second rectification column 2 is an ordinary rectification column.

[0047] It can be understood that the adsorption column 3 of the present invention is filled with an adsorbent, and the adsorbent is used to adsorb impurities in the crude trichlorosilane. The present invention does not make any special limitations on the adsorbent. The adsorbent can be a resin commonly used in the art that can be used to adsorb impurities.

[0048] In a specific embodiment, the low-boiling materials enter the pre-fractionation section 13 through the low-boiling material inlet of the pre-fractionation section 13 of the first rectification column. In the pre-fractionation section 13, the light components in the low-boiling materials (mainly including dichlorosilane dihydride and trichlorosilane) will ascend into the rectification section 11 at the top. The light components are separated in the rectification section 11, so that the trichlorosilane descends into the main fractionation section, thereby enriching the crude trichlorosilane in the main fractionation section and enriching the crude dichlorosilane dihydride in the rectification section 11. The crude dichlorosilane dihydride in the rectification section can be input into other processes (anti-disproportionation process) of polysilicon production; the heavy components in the low-boiling materials (mainly including silicon tetrachloride, trichlorosilane and a small amount of heavy components) will descend to the stripping section 12 at the bottom. In the stripping section 12, the trichlorosilane will ascend into the main fractionation section, thereby enriching the crude silicon tetrachloride and a small amount of heavy components in the stripping section 12 and enriching the crude trichlorosilane in the main fractionation section;

[0049] The crude silicon tetrachloride and a small amount of heavy components in the stripping section 12 are output through the bottom outlet of the stripping section 12. They can directly enter the second rectification column 2 through the high-boiling material inlet of the second rectification column 2, or enter the second rectification column 2 through the high-boiling material inlet of the second rectification column 2 after being mixed with the high-boiling materials. In the second rectification column 2, the crude silicon tetrachloride, a small amount of heavy components and the high-boiling materials are rectified. The crude trichlorosilane will ascend and be enriched at the top of the second rectification column 2, while the silicon tetrachloride and part of methyl dichlorosilane will descend and be enriched at the bottom of the second rectification column 2, and are discharged from the bottom of the second rectification column 2 to the slurry treatment process or sold for external treatment;

[0050] The crude trichlorosilane in the main fractionation section of the first rectification column is output through the first discharge port and can directly enter the adsorption column 3. The crude trichlorosilane generated at the top of the second rectification column 2 is output through the top discharge port of the second rectification column 2 and can directly enter the adsorption column 3; or, the crude trichlorosilane in the main fractionation section of the first rectification column is output through the first discharge port, and the crude trichlorosilane generated at the top of the second rectification column 2 is output through the top discharge port of the second rectification column 2. After the crude trichlorosilane generated by the first rectification column is mixed with the crude trichlorosilane generated by the second rectification column 2, it directly enters the adsorption column 3; in the adsorption column 3, the impurities in the crude trichlorosilane will be adsorbed, thereby obtaining trichlorosilane with a higher purity. This trichlorosilane can enter the rectification unit for further purification to prepare high-purity polysilicon.

[0051] The system for removing high and low boilers in polysilicon production of the present invention includes a first rectification column, a second rectification column 2, and an adsorption column 3 that are connected to each other. Among them, the first rectification column is a partition column, which can be equivalent to 1 - 3 conventional high and low boiler recovery columns, enabling the separation of light and heavy components in the low-boiling material in one column and improving the separation efficiency; the second rectification column 2 is mainly used for concentrating high-boiling components, and the adsorption column 3 is used for adsorbing impurities in the crude trichlorosilane obtained after separation by the first rectification column and the second rectification column 2. This system can remove high-boiling components and low-boiling components in polysilicon production and recover trichlorosilane with a higher purity.

[0052] The present invention realizes the recovery of high and low boilers in polysilicon production through a system including a first rectification column, a second rectification column 2, and an adsorption column 3, which can reduce equipment investment, floor area, and energy consumption, and has broad application prospects.

[0053] In some embodiments of the present invention, the system further includes a first heat exchanger 4, and the second main fractionation section 142 has a second discharge port;

[0054] The second discharge port is communicated with the heat source inlet of the first heat exchanger 4, the low-boiling material is communicated with the cold source inlet of the first heat exchanger 4, and the cold source outlet of the first heat exchanger 4 is communicated with the low-boiling material feed port.

[0055] The main fractionation section of the present invention includes a first main fractionation section and a second main fractionation section that are interconnected from top to bottom. Among them, the first main fractionation section 141 is more enriched in trichlorosilane, and the second main fractionation section 142 is more enriched in silicon tetrachloride. Since the temperature of the material output from the main fractionation section of the first rectification column is relatively high, the crude silicon tetrachloride output from the second main fractionation section 142 of the first rectification column can be used to preheat the low-boiling material, thereby saving energy consumption and reducing production costs.

[0056] Specifically, the system further includes a first heat exchanger 4. The crude trichlorosilane separated by the first distillation column can be output through the second discharge port of the second main fractionation section 142, enter the first heat exchanger 4 through the heat source inlet of the first heat exchanger 4, and the low-boiling material enters the first heat exchanger 4 through the cold source inlet of the first heat exchanger 4. In the first heat exchanger 4, the crude trichlorosilane separated by the first distillation column exchanges heat with the low-boiling material to preheat the low-boiling material. The preheated low-boiling material is output through the cold source outlet of the first heat exchanger 4 and enters the first distillation column through the feed port of the low-boiling material for distillation treatment. The crude trichlorosilane after heat exchange is output through the heat source outlet of the first heat exchanger 4 to other processes (anti-disproportionation process) of polysilicon production.

[0057] The present invention does not make special limitations on the first heat exchanger 4, as long as it can achieve heat exchange between the crude trichlorosilane and the low-boiling material.

[0058] In some embodiments of the present invention, the system further includes a second heat exchanger 5.

[0059] The top discharge port of the second distillation column 2 is communicated with the heat source inlet of the second heat exchanger 5, the bottom discharge port of the first distillation column is communicated with the cold source inlet of the second heat exchanger 5, the heat source outlet of the second heat exchanger 5 is communicated with the adsorption column 3, and the cold source outlet of the second heat exchanger 5 is communicated with the stripping section 12.

[0060] It can be understood that in the present invention, the crude trichlorosilane separated by the second distillation column 2 has a relatively high temperature, and the bottom of the first distillation column requires a heat source to provide heat for the first distillation column. Therefore, the heat of the crude trichlorosilane separated by the second distillation column 2 can be used to provide heat for the bottom of the first distillation column, and the temperature of the crude trichlorosilane obtained by the second distillation column 2 is reduced, so that the temperature of the crude trichlorosilane obtained by the second distillation column 2 is more matched with the temperature in the subsequent adsorption column 3, improving the adsorption efficiency.

[0061] Specifically, the crude trichlorosilane produced by the second distillation column 2 is output through the top discharge port of the second distillation column 2, enters the second heat exchanger 5 through the heat source inlet of the second heat exchanger 5, and the heavy components (including crude trichlorosilane and a small amount of heavy impurities) produced at the bottom of the first distillation column are output through the bottom discharge port of the first distillation column and enter the second heat exchanger 5 through the cold source inlet of the second heat exchanger 5. In the second heat exchanger 5, the material output from the first distillation column exchanges heat with the crude trichlorosilane produced by the second distillation column 2. The heavy components (including crude trichlorosilane and a small amount of heavy impurities) that have absorbed part of the heat are output through the cold source outlet of the second heat exchanger 5 to provide heat for the bottom of the first distillation column, while the crude trichlorosilane with reduced temperature is output through the heat source outlet of the second heat exchanger 5 and enters the adsorption column 3 for adsorption treatment.

[0062] The present invention does not particularly limit the second heat exchanger 5, as long as it can achieve the heat exchange between the heavy components generated by the first rectification column and the crude trichlorosilane.

[0063] In the present invention, the models of the first heat exchanger 4 and the second heat exchanger 5 may be the same or different.

[0064] The system for removing high and low boilers in polysilicon production of the present invention can be used to treat any high and low boilers generated in polysilicon production, and realize the recycling of raw materials. It is particularly suitable for treating high-boiling materials with a content of methyl dichlorosilane of 1-100 ppm.

[0065] It can be understood that the operating temperature and operating pressure of the first rectification column, the second rectification column 2, and the adsorption column 3 will have a crucial impact on the treatment efficiency, treatment load, and treatment result. Therefore, the present invention can further select the operating temperature and operating pressure of the first rectification column, the second rectification column 2, and the adsorption column 3 to improve the treatment efficiency, treatment load, and treatment effect of the system.

[0066] Exemplarily, in some embodiments of the present invention, in the first rectification column, the operating pressure is 0.15-0.3 MPaG, the top operating temperature is 35-52 °C, and the bottom operating temperature is 93-110 °C; and / or,

[0067] In the second rectification column 2, the operating pressure is 0.65-0.95 MPaG, the top operating temperature is 106-122 °C, and the bottom operating temperature is 109-124 °C; and / or,

[0068] In the adsorption column 3, the operating temperature is 20-60 °C, and the operating pressure is 0.5-1 MPaG.

[0069] Specifically, in the first rectification column, the operating pressure can be any one or the range formed by any two of 0.15 MPaG, 0.17 MPaG, 0.19 MPaG, 0.25 MPaG, 0.28 MPaG, and 0.3 MPaG, the top operating temperature can be any one or the range formed by any two of 35 °C, 38 °C, 40 °C, 41 °C, 45 °C, 50 °C, and 52 °C, and the bottom operating temperature can be any one or the range formed by any two of 93 °C, 95 °C, 98 °C, 100 °C, 105 °C, and 110 °C; and / or,

[0070] In the second rectification column 2, the operating pressure can be any one or the range formed by any two of 0.65 MPaG, 0.8 MPaG, and 0.95 MPaG, the top operating temperature can be any one or the range formed by any two of 106 °C, 110 °C, and 122 °C, and the bottom operating temperature can be any one or the range formed by any two of 109 °C, 110 °C, 120 °C, and 124 °C; and / or,

[0071] In the adsorption column 3, the operating temperature can be any one of 20°C, 40°C, 50°C, 60°C or the range formed by any two of them, and the operating pressure can be any one of 0.5 MPaG, 0.7 MPaG, 1 MPaG or the range formed by any two of them.

[0072] Furthermore, in some embodiments of the present invention, the reflux ratio of the second distillation column 2 is 5 - 15.

[0073] The inventors found in the research that when the reflux ratio of the second distillation column 2 is 5 - 15, the processing efficiency of the second distillation column 2 can be improved while saving energy consumption, and the methyl dichlorosilane in the second distillation column 2 can be further separated, thereby improving the purity of the crude trichlorosilane obtained from the second distillation column 2, and further obtaining a higher purity of crude trichlorosilane.

[0074] In a specific embodiment, the reflux ratio is 10.

[0075] By setting the reflux ratio of the second distillation column 2, the present invention can achieve efficient removal of methyl dichlorosilane without filling a catalyst in the second distillation column 2. In practical applications, not only does it not require frequent catalyst replacement, saving production costs; but also it avoids introducing impurities into the reaction system by the catalyst, improving the quality of the product.

[0076] In some embodiments of the present invention, the top of the adsorption column 3 has a top feed port, and the first discharge port and the top discharge port of the second distillation column 2 are respectively communicated with the top feed port of the adsorption column 3.

[0077] Specifically, the crude trichlorosilane separated by the first distillation column is output through the first discharge port, enters the adsorption column 3 through the top feed port of the adsorption column 3, the crude trichlorosilane separated by the second distillation column 2 is output through the top discharge port, and enters the adsorption column through the top feed port of the adsorption column 3; or the crude trichlorosilane separated by the first distillation column is output through the first discharge port, enters the adsorption column 3 through the top feed port of the adsorption column 3, the crude trichlorosilane separated by the second distillation column 2 is output through the top discharge port and is mixed with the crude trichlorosilane output by the first distillation column, and then enters the adsorption column through the top feed port of the adsorption column 3. In the adsorption column 3, the impurities in the crude trichlorosilane will be removed, thereby obtaining a higher purity of trichlorosilane.

[0078] The present invention makes the crude trichlorosilane enter the adsorption column 3 from the top of the adsorption column 3 and then output from the bottom of the adsorption column 3. By adopting the up - in and down - out method, the material flows downward, which helps to reduce the wear of the resin, delay the blockage of the adsorption column 3, and extend the service life of the system.

[0079] The second aspect of the present invention provides a method for removing high and low boilers in polysilicon production, which is carried out by using the system of the first aspect.

[0080] Specifically, the low-boiling material enters the pre-fractionation section 13 through the low-boiling material inlet of the pre-fractionation section 13 of the first distillation column. In the pre-fractionation section 13, the light components in the low-boiling material (mainly including dichlorosilane dihydride and trichlorosilane) will ascend into the rectification section 11 at the top. The light components are separated in the rectification section 11, and trichlorosilane descends into the main fractionation section, so that the main fractionation section is enriched with crude trichlorosilane, and the rectification section 11 is enriched with crude dichlorosilane dihydride. The crude dichlorosilane dihydride in the rectification section can be input into other processes (anti-disproportionation process) of polysilicon production; the heavy components in the low-boiling material (mainly including silicon tetrachloride, trichlorosilane and a small amount of heavy components) will descend to the stripping section 12 at the bottom. In the stripping section 12, trichlorosilane will ascend into the main fractionation section, so that the stripping section 12 is enriched with crude silicon tetrachloride and a small amount of heavy components, and the main fractionation section is enriched with crude trichlorosilane;

[0081] The crude silicon tetrachloride and a small amount of heavy components in the stripping section 12 are output through the bottom outlet of the stripping section 12, and can directly enter the second distillation column 2 through the high-boiling material inlet of the second distillation column 2, or can enter the second distillation column 2 through the high-boiling material inlet of the second distillation column 2 after being mixed with the high-boiling material. In the second distillation column 2, the crude silicon tetrachloride, a small amount of heavy components and the high-boiling material are rectified. The crude trichlorosilane will ascend and be enriched at the top of the second distillation column 2, while silicon tetrachloride and part of methyldichlorosilane will descend and be enriched at the bottom of the second distillation column 2, and are discharged from the bottom of the second distillation column 2 to the slurry treatment process or sold for external treatment;

[0082] The crude trichlorosilane in the main fractionation section of the first distillation column is output through the first outlet and can directly enter the adsorption column 3. The crude trichlorosilane generated at the top of the second distillation column 2 is output through the top outlet of the second distillation column 2 and can directly enter the adsorption column 3; or, the crude trichlorosilane in the main fractionation section of the first distillation column is output through the first outlet, and the crude trichlorosilane generated at the top of the second distillation column 2 is output through the top outlet of the second distillation column 2. After the crude trichlorosilane generated by the first distillation column is mixed with the crude trichlorosilane generated by the second distillation column 2, it directly enters the adsorption column 3; in the adsorption column 3, the impurities in the crude trichlorosilane will be adsorbed, so as to obtain trichlorosilane with higher purity. This trichlorosilane can enter the rectification unit for further purification to prepare high-purity polysilicon.

[0083] This preparation method is carried out by using the above system, so the high boilers and low boilers in polysilicon production can be removed, and thus high-purity trichlorosilane can be obtained. And this preparation method has simple operation and low cost, and is suitable for wide promotion and application.

[0084] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. The above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A system for removing high and low boilers in polysilicon production, characterized in that, it includes a first distillation column, a second distillation column and an adsorption column; The first distillation column includes a rectifying section at the top, a stripping section at the bottom, and a separation section located between the rectifying section and the stripping section. The rectifying section, the separation section, and the stripping section are sequentially and mutually connected. The separation section includes a pre-fractionation section and a main fractionation section arranged in parallel and not connected to each other. The main fractionation section includes a first main fractionation section and a second main fractionation section that are connected to each other from top to bottom in sequence; the pre-fractionation section has a low-boiling material inlet, the stripping section has a bottom outlet, and the first main fractionation section has a first outlet; The second distillation column has a high-boiling material inlet and a top outlet, and the bottom outlet of the stripping section is connected to the high-boiling material inlet; The first outlet and the top outlet of the second distillation column are respectively connected to the adsorption column; The low-boiling materials include silicon tetrachloride, trichlorosilane, and dichlorosilane; The high-boiling materials include trichlorosilane, silicon tetrachloride, and methyldichlorosilane.

2. The system according to claim 1, characterized in that, the system further includes a first heat exchanger, and the second main fractionation section has a second outlet; The second outlet is connected to the heat source inlet of the first heat exchanger, the low-boiling materials are connected to the cold source inlet of the first heat exchanger, and the cold source outlet of the first heat exchanger is connected to the low-boiling material inlet.

3. The system according to claim 1 or 2, characterized in that, the system further includes a second heat exchanger, The top outlet of the second distillation column is connected to the heat source inlet of the second heat exchanger, the bottom outlet of the first distillation column is connected to the cold source inlet of the second heat exchanger, the heat source outlet of the second heat exchanger is connected to the adsorption column, and the cold source outlet of the second heat exchanger is connected to the stripping section.

4. The system according to claim 3, characterized in that, in the high-boiling materials, the content of methyldichlorosilane is 1-100 ppm.

5. The system according to any one of claims 1-4, characterized in that, in the first distillation column, the operating pressure is 0.15-0.3 MPaG, the operating temperature at the top of the column is 35-52 °C, and the operating temperature at the bottom of the column is 93-110 °C.

6. The system according to any one of claims 1-5, characterized in that, in the second distillation column, the operating pressure is 0.65-0.95 MPaG, the operating temperature at the top of the column is 106-122 °C, and the operating temperature at the bottom of the column is 109-124 °C.

7. The system according to any one of claims 1-6, characterized in that, the reflux ratio of the second distillation column is 5-15.

8. The system according to any one of claims 1-7, characterized in that, in the adsorption column, the operating temperature is 20-60 °C, and the operating pressure is 0.5-1 MPaG.

9. The system according to any one of claims 1-8, characterized in that, the top of the adsorption column has a top inlet, and the first outlet and the top outlet of the second distillation column are respectively connected to the top inlet of the adsorption column.

10. A method for removing high and low boilers in polysilicon production, characterized in that, it is carried out by using the system described in any one of claims 1-9.

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