A trichlorosilane purification process in polysilicon production

Abstract

The present invention belongs to the technical field of polysilicon industrial production, and provides a trichlorosilane purification process in the polysilicon production process. The process includes: light removal: liquid phase crude chlorosilane from the cold hydrogenation section is passed into a light removal tower to obtain liquid phase crude trichlorosilane; complex adsorption: liquid phase crude trichlorosilane is passed into a complex adsorption device to perform complex adsorption on some metal impurities and B, P non-metallic impurities; crude distillation: liquid phase crude trichlorosilane obtained after complex adsorption is passed into a crude distillation unit to remove metal impurities and B, P non-metallic impurities, high and low boiling points, and obtain primary purified trichlorosilane liquid; CPS adsorption: primary purified trichlorosilane liquid is passed into a CPS adsorption device to further remove impurities; distillation: liquid phase trichlorosilane after CPS adsorption is passed into a distillation unit to obtain high-purity trichlorosilane liquid. The present invention combines complex adsorption, CPS adsorption and distillation process optimization, which can effectively reduce impurities such as B and P in trichlorosilane, and reduce distillation costs.

Description

Technical Field

[0001] The invention belongs to the technical field of polysilicon industrial production, and in particular relates to a trichlorosilane purification process in the polysilicon production process. Background Art

[0002] During the polysilicon production process, due to the metallic and non-metallic impurities in industrial silicon powder, hydrogen chloride, hydrogen, purchased trichlorosilane, etc., as well as the impurities introduced when the materials flow through the equipment pipeline, the initial raw material chlorosilane contains a large number of impurities of different types and contents, mainly elements such as B, P, C, O and metals (Fe, Cr, Ni, Cu, Zn, Na, Al, etc.).

[0003] As a raw material for the production of polysilicon, trichlorosilane must go through a multi-stage rigorous impurity removal process before entering the reduction furnace to react with hydrogen to produce polysilicon. Most impurity contents meet production requirements after a single distillation purification, but some boron and phosphorus impurity compounds in trichlorosilane have boiling points close to that of trichlorosilane, and are difficult to remove directly by distillation. Therefore, their content is still relatively high relative to the final requirements and needs to be further removed.

[0004] At present, both at home and abroad, the purpose of purification is basically achieved through multi-stage distillation, but distillation purification has high energy consumption and large investment, which puts great pressure on the operation and production of enterprises. In addition, in recent years, some domestic enterprises have also used adsorption devices to remove impurities and used the principle of chemical adsorption to remove boron and phosphorus impurities, but since a series of chemical reactions will occur during the adsorption process, which is almost irreversible, the adsorbent needs to be replaced frequently, and the adsorption efficiency is greatly reduced in the later stage of use, and the B and P content in the chlorosilane after adsorption cannot meet the requirements.

[0005] Complex adsorption not only has a strong adsorption capacity, but also the selective adsorption process is reversible, and the adsorbate can be desorbed and separated under certain conditions. Complex adsorption utilizes the selective adsorption of complex bonds, overcoming the disadvantages of weak van der Waals bond energy and irreversible adsorption with other chemical reactions. It is an adsorption separation technology with great application research prospects.

[0006] The combination of complex adsorption and other adsorption methods, as well as the optimization of the distillation process, can more efficiently and economically purify trichlorosilane in polysilicon production. Summary of the invention

[0007] The present invention aims to solve the above-mentioned defects of the prior art and provide a trichlorosilane purification process in the polysilicon production process, which effectively reduces the content of impurities such as B and P in trichlorosilane by optimizing the combination of complex adsorption, CPS adsorption (Chlorosilane Purification System) and distillation process, and reduces the operating cost of the distillation system.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] A trichlorosilane purification process in a polysilicon production process comprises the following steps:

[0010] Step S1: Light removal: Liquid crude chlorosilane from the cold hydrogenation section is passed into a light removal tower to remove light components to obtain liquid crude trichlorosilane;

[0011] Step S2: complex adsorption; the liquid phase crude trichlorosilane is passed into a complex adsorption device, and the complex adsorption device performs complex adsorption treatment on some metal impurities and B and P non-metallic impurities;

[0012] Step S3: crude distillation; the crude liquid trichlorosilane obtained after the complex adsorption is passed into a crude distillation unit to remove metal impurities and B, P non-metallic impurities, high and low boiling points, and obtain primary purified trichlorosilane liquid;

[0013] Step S4: CPS adsorption; passing the primary purified trichlorosilane liquid into a CPS adsorption device to further remove impurities in the primary purified trichlorosilane liquid;

[0014] Step S5: distillation; the liquid phase trichlorosilane after CPS adsorption is passed into a distillation unit to obtain high-purity trichlorosilane liquid.

[0015] Furthermore, the liquid crude chlorosilane in step S1 is a liquid mixture of dichlorosilane, trichlorosilane and hydrogen chloride containing metal impurities and non-metallic impurities, the metal impurities include Fe, Cr, Ni, Cu, Zn, Na, Al and K, and the non-metallic impurities include B and P.

[0016] Furthermore, in step S1, the light-removing tower is a sieve plate tower, and the light components removed by the light-removing tower include dichlorosilane; the operating temperature of the light-removing tower is 60-95° C., and the operating pressure is 0.2-0.6 Mpag.

[0017] Furthermore, the complex adsorption device in step S2 includes two parallel complex adsorption towers, namely: complex adsorption tower A and complex adsorption tower B; each of the complex adsorption towers is provided with a complex adsorption column with a vertical bed structure, and the complex adsorption column is loaded with a complex adsorbent; the complex adsorbent is a silica gel-based loading agent.

[0018] Furthermore, the volume of the complex adsorption tower is 7.5m 3 The outer periphery of the complex adsorption tower is provided with a regeneration heating jacket, and the working temperature of the complex adsorption tower is between 30-90°C.

[0019] Furthermore, the crude distillation unit in step S3 comprises at least three stages of crude distillation devices connected in series; and the crude distillation devices are all packed towers.

[0020] Furthermore, the crude distillation unit includes a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series in sequence, the operating temperature of the first crude distillation tower is 60-70°C, and the working pressure is 0.1-0.3Mpag; the operating temperature of the second crude distillation tower is 80-90°C, and the working pressure is 0.35-0.40Mpag; the operating temperature of the third crude distillation tower is 90-110°C, and the working pressure is 0.4-0.7Mpag.

[0021] Furthermore, the operating temperature of the CPS adsorption device in step S4 is 84-93° C., and the operating pressure is 0.3-0.5 Mpag.

[0022] Furthermore, the distillation unit in step S5 comprises at least three stages of distillation devices connected in series; and the distillation devices are all packed towers.

[0023] Furthermore, the distillation unit includes a first distillation tower, a second distillation tower and a third distillation tower connected in series in sequence, the operating temperature of the first distillation tower is 55-70°C, and the working pressure is 0.1-0.3Mpag; the operating temperature of the second distillation tower is 80-100°C, and the working pressure is 0.3-0.5Mpag; the operating temperature of the third distillation tower is 100-115°C, and the working pressure is 0.6-0.8Mpag.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The present invention provides a trichlorosilane purification process in the polysilicon production process. Taking into account the current impurity situation (impurity content, type), purification device cost and effect, comprehensive energy consumption and other factors of the polysilicon system, the adsorption device and the order of crude distillation and rectification are arranged scientifically and reasonably. First, a light component such as dichlorodihydrogen silicon is removed by a light removal tower, and then a complex adsorption device is used to form a complex to adsorb part of the metal impurities and non-metallic impurities such as B and P in the liquid phase crude trichlorosilane. Then, the crude distillation unit performs crude distillation treatment, and the CPS adsorption device performs adsorption treatment, and finally, the distillation unit performs rectification and purification. Compared with the prior art, the present invention adopts a process combining multiple adsorption modes with rectification optimization, and scientifically arranges the position and sequence of each impurity removal device, which can efficiently remove part of the metal impurities and non-metallic impurities such as B and P in trichlorosilane in polysilicon production. The content of metal impurities, B, and P is maintained at the ppb level, and the purification accuracy and efficiency are high.

[0026] (2) The present invention provides a process for purifying trichlorosilane in a polysilicon production process, which adopts a process combining multiple adsorption and distillation. After adding multiple adsorption devices before distillation, the impurities in trichlorosilane that need to be distilled and removed are relatively reduced, the reflux ratio of the distillation device is reduced, the energy consumption is significantly reduced, and the equipment installation is relatively simple, the investment is small, and the purpose of reducing the operating cost of the enterprise can be achieved, thereby reducing costs, improving quality, and increasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of the trichlorosilane purification process according to an embodiment of the present invention;

[0028] Markings in the figure: 1- lightness removal tower; 2- complex adsorption device, 21- complex adsorption tower A, 22- complex adsorption tower B; 3- crude distillation unit; 4- CPS adsorption unit; 5- distillation unit. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Combination Figure 1 As shown, an embodiment of the present invention provides a trichlorosilane purification process in a polysilicon production process, and the process includes the following steps:

[0031] Step S1: Light removal: Liquid crude chlorosilane from the cold hydrogenation section is passed into a light removal tower 1 to remove light components to obtain liquid crude trichlorosilane;

[0032] Step S2: complex adsorption; the liquid phase crude trichlorosilane is passed into the complex adsorption device 2, and the complex adsorption device 2 performs complex adsorption treatment on part of the metal impurities and B and P non-metallic impurities;

[0033] Step S3: crude distillation; the crude liquid trichlorosilane obtained after the complex adsorption is passed into the crude distillation unit 3 to remove metal impurities and B, P non-metallic impurities, high and low boiling points, and obtain primary purified trichlorosilane liquid;

[0034] Step S4: CPS adsorption; passing the primary purified trichlorosilane liquid into the CPS adsorption device 4 to further remove impurities in the primary purified trichlorosilane liquid;

[0035] Step S5: distillation; the liquid phase trichlorosilane after CPS adsorption is passed into the distillation unit 5 to obtain high-purity trichlorosilane liquid.

[0036] Specifically, in step S1, the liquid crude chlorosilane is a liquid mixture of dichlorosilane, trichlorosilane and hydrogen chloride containing metal impurities such as Fe, Cr, Ni, Cu, Zn, Na, Al, K and non-metallic impurities such as B and P; the light-removing tower 1 is a sieve plate tower, and the light components removed by the light-removing tower are light components such as dichlorosilane; the operating temperature of the light-removing tower is 60-95°C, and the operating pressure is 0.2-0.6Mpag.

[0037] The complex adsorption device 2 in step S2 includes two parallel complex adsorption towers, namely: complex adsorption tower A21 and complex adsorption tower B22; the complex adsorption towers are each provided with a complex adsorption column with a vertical bed structure, and the complex adsorption column is loaded with a complex adsorbent; the complex adsorbent is a silica gel loading agent, and the silica gel loading agent includes a silica-alumina gel inorganic mineral (aluminum gel skeleton composite Lewis acid-base mixture), which can more specifically and effectively adsorb and remove some metal impurities and non-metallic impurities such as B and P in the liquid phase crude trichlorosilane discharged from the lightness removal tower 1. The volume of the complex adsorption tower is 7.5m 3 The outer periphery of the complex adsorption tower is provided with a regeneration heating jacket for heating, and the working temperature of the complex adsorption tower is between 30-90°C.

[0038] The crude distillation unit 3 in step S3 includes three stages of crude distillation devices connected in series, namely a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series in sequence, and the crude distillation devices are all packed towers; wherein the working temperature of the first crude distillation tower is 60-70°C, and the working pressure is 0.1-0.3Mpag; the working temperature of the second crude distillation tower is 80-90°C, and the working pressure is 0.3-0.4Mpag; the working temperature of the third crude distillation tower is 90-110°C, and the working pressure is 0.4-0.7Mpag.

[0039] The CPS adsorption device in step S4 is used to perform CPS adsorption treatment on the trichlorosilane liquid discharged from the crude distillation unit 3. The CPS adsorption device is two adsorption columns used in parallel. The adsorption columns are filled with adsorbents. The principle is that the solid adsorbent is adsorbed and separated based on the polarity of the chemical bonds of the compounds. The working temperature is 84-93°C and the working pressure is 0.3-0.5Mpag.

[0040] The distillation unit 5 in step S5 comprises three-stage series-connected distillation devices, namely a first distillation tower, a second distillation tower and a third distillation tower; the distillation devices are all packed towers; wherein the working temperature of the first distillation tower is 55-70°C, and the working pressure is 0.1-0.3Mpag; the working temperature of the second distillation tower is 80-100°C, and the working pressure is 0.3-0.5Mpag; the working temperature of the third distillation tower is 100-115°C, and the working pressure is 0.6-0.8Mpag.

[0041] The beneficial effects of the present invention will be further illustrated below in conjunction with embodiments and comparative examples.

[0042] Example 1

[0043] The composition of the liquid crude chlorosilane is 97.44% trichlorosilane, 2.49% dichlorosilane, impurity B≤45ppbw, impurity P≤2ppbw, and the total metal impurities≤1000ng / g.

[0044] Step S1: light removal; the liquid crude chlorosilane is passed into the light removal tower 1 for light removal treatment to obtain a crude trichlorosilane liquid product. During the light removal process, the bottom temperature of the tower is 83°C, the bottom pressure of the tower is 0.38Mpag, and the feed rate is controlled not to exceed 5m per hour. 3 ;

[0045] Step S2: complex adsorption; the crude trichlorosilane liquid is passed into the complex adsorption device 2 for complex adsorption treatment, and the complex reaction temperature is 60°C;

[0046] Step S3: crude distillation; the product obtained in step S2 is introduced into a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series for crude distillation, wherein the working temperature of the bottom of the first crude distillation tower is 60°C and the bottom pressure is 0.165Mpag; the bottom temperature of the second crude distillation tower is 81°C and the bottom pressure is 0.35Mpag; the bottom temperature of the third crude distillation tower is 91°C and the bottom pressure is 0.45Mpag;

[0047] Step S4: CPS adsorption; the product obtained in step S3 is passed into the CPS adsorption device 4, the top temperature is 91.1°C, the top pressure is 0.30Mpag, the bottom temperature is 84.5°C, and the bottom pressure is 0.37Mpag;

[0048] Step S5: distillation; the product obtained in step S4 is passed into a first distillation tower, a second distillation tower and a third distillation tower connected in series for distillation, wherein the bottom temperature of the first distillation tower is 58°C and the bottom pressure is 0.14Mpag; the bottom temperature of the second distillation tower is 83°C and the bottom pressure is 0.37Mpag; the bottom temperature of the third distillation tower is 107.7°C and the bottom pressure is 0.64Mpag.

[0049] The purity of trichlorosilane finally obtained after the above steps is above 6N, impurity B≤0.3ppbw, impurity P≤1.0ppbw, and the total impurity content (excluding Ca 2+ )≤10ng / g.

[0050] Comparative Example 1

[0051] The composition of the liquid crude chlorosilane is 97.44% trichlorosilane, 2.49% dichlorosilane, impurity B≤45ppbw, impurity P≤2ppbw, and the total metal impurities≤1000ng / g.

[0052] Step S1: light removal; the liquid crude chlorosilane is passed into the light removal tower 1 for light removal treatment to obtain a crude trichlorosilane liquid product. During the light removal process, the bottom temperature of the tower is 83°C, the bottom pressure of the tower is 0.38Mpag, and the feed rate is controlled not to exceed 5m per hour. 3 ;

[0053] Step S2: complex adsorption; the crude trichlorosilane liquid is passed into the complex adsorption device 2 for complex adsorption treatment, and the complex reaction temperature is 60°C;

[0054] Step S3: crude distillation; the product obtained in step S2 is introduced into a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series for crude distillation, wherein the working temperature of the bottom of the first crude distillation tower is 60°C and the bottom pressure is 0.165Mpag; the bottom temperature of the second crude distillation tower is 81°C and the bottom pressure is 0.35Mpag; the bottom temperature of the third crude distillation tower is 91°C and the bottom pressure is 0.45Mpag;

[0055] Step S4: distillation; the product obtained in step S4 is passed into a first distillation tower, a second distillation tower and a third distillation tower connected in series for distillation, wherein the bottom temperature of the first distillation tower is 58°C and the bottom pressure is 0.14Mpag; the bottom temperature of the second distillation tower is 83°C and the bottom pressure is 0.37Mpag; the bottom temperature of the third distillation tower is 107.7°C and the bottom pressure is 0.64Mpag.

[0056] The purity of trichlorosilane finally obtained after the above steps is above 5N, impurity B≤0.8ppbw, impurity P≤1.5ppbw, and the total impurity content (excluding Ca 2+ )≤50ng / g.

[0057] Example 2

[0058] The composition of the liquid crude chlorosilane is 99.90% trichlorosilane, 0.73wt% dichlorosilane, impurity B≤7ppbw, impurity P≤2ppbw, and the total metal impurities≤100ng / g.

[0059] Step S1: light removal; the liquid crude chlorosilane is passed into the light removal tower 1 for light removal treatment to obtain a crude trichlorosilane liquid product. During the light removal process, the bottom temperature of the tower is 84.5°C, the bottom pressure of the tower is 0.385Mpag, and the feed rate is controlled not to exceed 5m per hour. 3 ;

[0060] Step S2: complex adsorption; the crude trichlorosilane liquid is passed into the complex adsorption device 2 for complex adsorption treatment, and the complex reaction temperature is 60°C;

[0061] Step S3: crude distillation; the product obtained in step S2 is introduced into a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series for crude distillation, wherein the working temperature of the bottom of the first crude distillation tower is 61°C and the bottom pressure is 0.170Mpag; the bottom temperature of the second crude distillation tower is 81.3°C and the bottom pressure is 0.35Mpag; the bottom temperature of the third crude distillation tower is 92°C and the bottom pressure is 0.455Mpag;

[0062] Step S4: CPS adsorption; the product obtained in step S3 is passed into the CPS adsorption device 4, the top temperature is 91.6°C, the top pressure is 0.30Mpag, the bottom temperature is 85.1°C, and the bottom pressure is 0.37Mpag;

[0063] Step S5: distillation; the product obtained in step S4 is passed into a first distillation tower, a second distillation tower and a third distillation tower connected in series for distillation, wherein the bottom temperature of the first distillation tower is 58.4°C and the bottom pressure is 0.145Mpag; the bottom temperature of the second distillation tower is 83.2°C and the bottom pressure is 0.375Mpag; the bottom temperature of the third distillation tower is 108.7°C and the bottom pressure is 0.646Mpag.

[0064] The purity of trichlorosilane finally obtained after the above steps is above 8N, impurity B≤0.1ppbw, impurity P≤0.06ppbw, and the total impurity content (excluding Ca 2+ )≤8ng / g.

[0065] Comparative Example 2

[0066] The composition of the liquid crude chlorosilane is 99.90% trichlorosilane, 0.73wt% dichlorosilane, impurity B≤7ppbw, impurity P≤2ppbw, and the total metal impurities≤100ng / g.

[0067] Step S1: light removal; the liquid crude chlorosilane is passed into the light removal tower 1 for light removal treatment to obtain a crude trichlorosilane liquid product. During the light removal process, the bottom temperature of the tower is 84.5°C, the bottom pressure of the tower is 0.385Mpag, and the feed rate is controlled not to exceed 5m per hour. 3 ;

[0068] Step S2: crude distillation; the product obtained in step S2 is introduced into a first crude distillation tower, a second crude distillation tower and a third crude distillation tower connected in series for crude distillation, wherein the working temperature of the bottom of the first crude distillation tower is 61°C and the bottom pressure is 0.170Mpag; the bottom temperature of the second crude distillation tower is 81.3°C and the bottom pressure is 0.35Mpag; the bottom temperature of the third crude distillation tower is 92°C and the bottom pressure is 0.455Mpag;

[0069] Step S3: CPS adsorption; the product obtained in step S3 is passed into the CPS adsorption device 4, the top temperature is 91.6°C, the top pressure is 0.30Mpag, the bottom temperature is 85.1°C, and the bottom pressure is 0.37Mpag;

[0070] Step S4: distillation; the product obtained in step S4 is passed into a first distillation tower, a second distillation tower and a third distillation tower connected in series for distillation, wherein the bottom temperature of the first distillation tower is 58.4°C and the bottom pressure is 0.145Mpag; the bottom temperature of the second distillation tower is 83.2°C and the bottom pressure is 0.375Mpag; the bottom temperature of the third distillation tower is 108.7°C and the bottom pressure is 0.646Mpag.

[0071] The purity of trichlorosilane finally obtained after the above steps is above 6N, impurity B≤0.7ppbw, impurity P≤1.4ppbw, and the total impurity content (excluding Ca 2+ )≤30ng / g.

[0072] The above description is only an embodiment of the present application and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for purifying trichlorosilane in a polysilicon production process, characterized in that: The steps include: Step S1: Light removal: Liquid crude chlorosilane from the cold hydrogenation section is passed into a light removal tower (1) to remove light components to obtain liquid crude trichlorosilane; Step S2: complex adsorption; the liquid phase crude trichlorosilane is passed into the complex adsorption device (2), and the complex adsorption device (2) performs complex adsorption treatment on part of the metal impurities and B and P non-metallic impurities; Step S3: crude distillation; the crude liquid trichlorosilane obtained after the complex adsorption is passed into the crude distillation unit (3) to remove metal impurities and B, P non-metallic impurities, high and low boiling points, and obtain primary purified trichlorosilane liquid; Step S4: CPS adsorption; passing the primary purified trichlorosilane liquid into a CPS adsorption device (4) to further remove impurities in the primary purified trichlorosilane liquid; Step S5: distillation; passing the liquid phase trichlorosilane after CPS adsorption into the distillation unit (5) to obtain high-purity trichlorosilane liquid; The liquid crude chlorosilane in step S1 is a liquid mixture of dichlorosilane, trichlorosilane and hydrogen chloride containing metal impurities and non-metal impurities, wherein the metal impurities include Fe, Cr, Ni, Cu, Zn, Na, Al and K, and the non-metal impurities include B and P; The CPS adsorption device in step S4 is two adsorption columns used in parallel, and the adsorption columns are filled with adsorbents. The principle is that the solid adsorbent is adsorbed and separated based on the polarity of the chemical bonds of the compounds.

2. The process for purifying trichlorosilane in a polysilicon production process according to claim 1, characterized in that: In step S1, the light-removal tower (1) is a sieve plate tower, and the light components removed by the light-removal tower include dichlorosilane; the operating temperature of the light-removal tower is 60-95° C., and the operating pressure is 0.2-0.6 MPag.

3. The process for purifying trichlorosilane in a polysilicon production process according to claim 1, characterized in that: The complex adsorption device (2) in step S2 comprises two parallel complex adsorption towers, namely: complex adsorption tower A (21) and complex adsorption tower B (22); each of the complex adsorption towers is provided with a complex adsorption column with a vertical bed structure, and the complex adsorption column is loaded with a complex adsorbent; the complex adsorbent is a silica gel-based loading agent.

4. The process for purifying trichlorosilane in a polysilicon production process according to claim 3, characterized in that: The volume of the complex adsorption tower is 7.5m 3 The outer periphery of the complex adsorption tower is provided with a regeneration heating jacket, and the working temperature of the complex adsorption tower is between 30-90°C.

5. The process for purifying trichlorosilane in a polysilicon production process according to claim 1, characterized in that: The crude distillation unit (3) in step S3 comprises at least three stages of crude distillation devices connected in series; all of the crude distillation devices are packed towers.

6. The process for purifying trichlorosilane in a polysilicon production process according to claim 5, characterized in that: The crude distillation unit (3) comprises a first crude distillation tower, a second crude distillation tower and a third crude distillation tower which are connected in series in sequence. The working temperature of the first crude distillation tower is 60-70°C and the working pressure is 0.1-0.3MPag; the working temperature of the second crude distillation tower is 80-90°C and the working pressure is 0.3-0.4MPag; the working temperature of the third crude distillation tower is 90-110°C and the working pressure is 0.4-0.7MPag.

7. The process for purifying trichlorosilane in a polysilicon production process according to claim 1, characterized in that: The operating temperature of the CPS adsorption device in step S4 is 84-93° C., and the operating pressure is 0.3-0.5 MPag.

8. The process for purifying trichlorosilane in a polysilicon production process according to claim 1, characterized in that: The distillation unit (5) in step S5 comprises at least three stages of distillation devices connected in series; all of the distillation devices are packed towers.

9. The process for purifying trichlorosilane in a polysilicon production process according to claim 8, characterized in that: The distillation unit (5) comprises a first distillation tower, a second distillation tower and a third distillation tower which are connected in series in sequence, wherein the working temperature of the first distillation tower is 55-70°C and the working pressure is 0.1-0.3MPag; the working temperature of the second distillation tower is 80-100°C and the working pressure is 0.3-0.5MPag; the working temperature of the third distillation tower is 100-115°C and the working pressure is 0.6-0.8MPag.

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