Chlorosilane raw material purification system and method for reducing donor and acceptor impurities in polycrystalline silicon

Abstract

The invention discloses a chlorosilane raw material purification system and method for reducing donor and acceptor impurities in polycrystalline silicon, and belongs to the technical field of polycrystalline silicon production, the chlorosilane raw material enters a first rectifying tower for primary rectification separation, the tower kettle of the first rectifying tower is extracted and flows into a silicon tetrachloride raw material tank, and the tower top of the first rectifying tower is extracted and flows into a second rectifying tower; tower top produced liquid of the first rectifying tower is subjected to secondary rectifying separation in a second rectifying tower, tower bottom produced liquid of the second rectifying tower flows into a third rectifying tower, and tower top produced liquid of the second rectifying tower flows into a mixer; tower kettle produced liquid of the second rectifying tower is subjected to third-time rectifying separation in a third rectifying tower, and tower top produced liquid of the third rectifying tower flows into a fourth rectifying assembly; the tower top produced liquid of the third rectifying tower is subjected to fourth rectifying separation in a fourth rectifying assembly, tower bottom produced liquid of the fourth rectifying assembly flows into a chlorosilane storage tank, and product liquid is produced from the tower top of the fourth rectifying assembly; and the tower kettle produced liquid of the third rectifying tower is subjected to adsorption and impurity removal in the first adsorber, and flows into a chlorosilane storage tank after impurity removal.

Description

Technical Field

[0001] The present invention belongs to the technical field of polysilicon production, and in particular relates to a chlorosilane raw material purification system and method for reducing donor impurities and host acceptor impurities in polysilicon. Background Art

[0002] High-purity polysilicon is typically produced using a CVD process called the Siemens process, using chlorosilane gases, primarily trichlorosilane, as raw materials in a hydrogen atmosphere. Therefore, the chlorosilanes used as raw materials for high-purity polysilicon are also required to be extremely pure.

[0003] In particular, when impurities contained in raw chlorosilanes are impurities such as phosphorus and arsenic that act as donors in silicon crystals, or impurities such as boron and aluminum that act as acceptors, even trace amounts of these impurities can significantly affect the electrical properties (resistivity) of the resulting polycrystalline silicon. Therefore, providing a technology that efficiently removes these donor and acceptor impurities contained in raw chlorosilanes, resulting in high purity, is of great practical significance.

[0004] Generally, chlorosilanes for polycrystalline silicon production are produced by obtaining a chlorosilane distillate from metallurgical-grade silicon (so-called metallic-grade silicon, hereinafter referred to as "metallic silicon") containing a relatively large amount of impurities by a known method, and then further purifying the chlorosilane distillate by distillation or other methods to a high purity.

[0005] However, metallic silicon typically contains these donor and acceptor impurities at levels ranging from several hundred ppb (atomic) to several hundred ppm (atomic) in atomic ratio. Consequently, these impurities are not fully removed during the purification process of the chlorosilane distillate, resulting in residual donor and acceptor impurities in the resulting chlorosilanes. These residual impurities can degrade the quality of polycrystalline silicon.

[0006] As a method for obtaining a chlorosilane distillate, a hydrogenation step is known in which a substance containing tetrachlorosilane (SiCl4) is reacted with hydrogen in the presence of metallic silicon to obtain a chlorosilane distillate containing trichlorosilane (SiHCl3) (for example, see Japanese Unexamined Patent Publication No. 2008-532907 (Patent Document 1), Japanese Unexamined Patent Publication No. 58-217422 (Patent Document 2), Japanese Unexamined Patent Publication No. 58-161915 (Patent Document 3), etc.).

[0007] The hydrogenation reaction proceeds according to the following reaction formula.

[0008] 3SiC14+2H2+Si→4SiHC13[Formula 1] Chlorosilane distillate is a fraction of crude chlorosilanes synthesized by hydrogenation reaction, and is generally a mixture of chlorosilanes such as dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), and tetrachlorosilane (SiCl4) as main components.

[0009] Another known method for obtaining a chlorosilane distillate is a chlorination step in which metallic silicon is brought into contact with hydrogen chloride in the presence of a catalyst to cause a chlorination reaction to produce a chlorosilane distillate containing trichlorosilane (see, for example, Japanese Patent Application Laid-Open No. 2005-67979 (Patent Document 4)).

[0010] The chlorination reaction proceeds according to the following reaction formula.

[0011] Si + 3HCl → SiHC13 + H2 [Formula 2] The chlorosilane distillate is a fraction of crude chlorosilanes synthesized by a chlorination reaction, and in this case, it is generally a mixture containing chlorosilanes such as dichlorosilane, trichlorosilane, and tetrachlorosilane as main components.

[0012] It is generally believed that donor and acceptor impurities contained in metallic silicon undergo simultaneous hydrogenation and chlorination during the production of crude chlorosilanes, contaminating the crude chlorosilanes in the form of compounds with various structures. While purification of these crude chlorosilanes can yield high-purity chlorosilanes, the boiling points of the donor and acceptor impurity compounds are close to that of trichlorosilane, making separation and removal of these impurities difficult using conventional distillation methods.

[0013] Furthermore, when polycrystalline silicon is produced using chlorosilanes from which donor impurities and acceptor impurities have not been sufficiently removed as a raw material, polycrystalline silicon having desired characteristics cannot be obtained.

[0014] In light of the above circumstances, various methods have been proposed for removing donor and acceptor impurities from chlorosilane distillates. For example, a method has been proposed in which an organic substance is added to the chlorosilane distillate to form adducts with the donor or acceptor impurities, and then the adducts are purified by distillation to obtain high-purity chlorosilanes.

[0015] Specifically, Japanese Patent Application Publication No. 2005-67979 (Patent Document 4) discloses a method of adding ethers to chlorosilanes and then performing distillation purification. Furthermore, U.S. Patent No. 3,126,248 (Patent Document 5) discloses a method of removing impurities by adding organic compounds containing dioxane, benzaldehyde, methyl ethyl ketone, dimethylglyoxime, and valerolactone. Furthermore, Japanese Patent Application Publication No. 2009-62213 (Patent Document 6) discloses a method of reacting chlorosilanes with oxygen in the presence of benzaldehyde to convert impurities into high-boiling-point compounds, and then subjecting the treated chlorosilanes to distillation, etc., to separate the high-boiling-point compounds as impurities from the chlorosilanes.

[0016] Furthermore, a method has been proposed in which a metal chloride is added to a chlorosilane distillate to form an adduct with a donor impurity or an acceptor impurity, and then the adduct is purified by distillation to obtain high-purity chlorosilanes.

[0017] Specifically, U.S. Patent No. 2,821,460 (Patent Document 7) discloses a method of adding aluminum chloride to chlorosilanes to form an AlCl3·PCl5 complex, followed by purification by distillation. Japanese Patent Application Laid-Open No. 4-300206 (Patent Document 8) discloses a method of adding a high-concentration aqueous solution of an inorganic salt such as TiCl4 to hydrolyze impurities to form high-boiling-point compounds, followed by purification by distillation.

[0018] Furthermore, a method has been proposed in which impurities contained in chlorosilanes are removed by adsorbing them onto alumina, silica gel, activated carbon, or the like.

[0019] Specifically, the following method is disclosed in the specification of U.S. Patent No. 3252752 (Patent Document 9): a substance having a lone pair of electrons (for example, a substance such as propionitrile having a nitrogen atom or benzaldehyde having an oxygen atom) is fixed to an adsorbent such as activated carbon or silica gel, and a chlorosilane gas is introduced therein to capture and remove impurities. In addition, the specification of German Patent No. 1289834 (Patent Document 10) discloses a method for removing impurities by contacting chlorosilanes with activated alumina in a liquid or vapor state. In addition, the specification of U.S. Patent No. 4112057 (Patent Document 11) discloses a method for removing impurities by contacting chlorosilanes with metal oxides such as hydrated silica gel or alumina gel, and the publication of Japanese Patent Application Laid-Open No. 2001-2407 (Patent Document 12) discloses a method for removing impurities by contacting chlorosilanes with fluoride salts of alkali metals or alkaline earth metals.

[0020] In addition to these methods, the following method has been proposed: a small amount of oxygen is introduced into chlorosilanes under high temperature conditions to cause a reaction to form a complex, the complex is reacted with a donor impurity or an acceptor impurity to form a new complex, and the new complex is separated in the distillation process of the chlorosilanes, thereby obtaining chlorosilanes with a low impurity concentration (see Japanese Patent Publication No. 58-500895 (Patent Document 13)).

[0021] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application No. 2008-532907 Patent Document 2: Japanese Patent Application Laid-Open No. 58-217422 Patent Document 3: Japanese Patent Application Laid-Open No. 58-161915 Patent Document 4: Japanese Patent Application Laid-Open No. 2005-67979 Patent Document 5: U.S. Patent No. 3126248 Patent Document 6: Japanese Patent Application Laid-Open No. 2009-62213 Patent Document 7: U.S. Patent No. 2,821,460 Patent Document 8: Japanese Patent Application Laid-Open No. 4-300206 Patent Document 9: U.S. Patent No. 3,252,752 Patent Document 10: German Patent No. 1289834 Patent Document 11: U.S. Patent No. 4,112,057 Patent Document 12: Japanese Patent Application Laid-Open No. 2001-2407 Patent Document 13: Japanese Patent Application No. 58-500895 Summary of the Invention

[0022] The above technical route introduces other substances to convert donor and acceptor impurities into other substances, which makes subsequent processing complicated. The present invention provides a chlorosilane raw material purification system and method for reducing donor and acceptor impurities in polysilicon. The chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process is subjected to first distillation separation, second distillation separation, third distillation separation and fourth distillation separation in a first distillation tower, a second distillation tower, a third distillation tower and a fourth distillation assembly to obtain high-purity trichlorosilane (trichlorosilane concentration is greater than 99.9%). Dichlorodihydrosilane in the chlorosilane raw material reacts with silicon tetrachloride in a reactor to obtain trichlorosilane, further improving the utilization rate of chlorosilane (the theoretical utilization rate of chlorosilane raw material is 100%, realizing closed-loop use of raw materials). The first adsorber removes B / P impurities in the form of heavy components (the removal rate of B / P impurities in the form of heavy components is greater than 90%), and the second adsorber removes B / P impurities in the form of light components (the removal rate of B / P impurities in the form of light components is greater than 90%).

[0023] The purpose of the present invention is achieved through the following technical solutions: A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon comprises a first distillation tower, the first distillation tower being connected to a chlorosilane feed pipe, a first silicon tetrachloride outlet pipe, and a first connecting pipe, the first connecting pipe being connected to a second distillation tower, the second distillation tower being connected to a second connecting pipe and a third connecting pipe, the second connecting pipe being connected to a third distillation tower, the third distillation tower being connected to a fourth connecting pipe and a fifth connecting pipe, the fourth connecting pipe being connected to a fourth distillation assembly, the fourth distillation assembly being connected to a product liquid outlet pipe and a chlorosilane feed tank; the fifth connecting pipe being connected to a first cooler and a first adsorber, the first adsorber being connected to the chlorosilane feed tank; the third connecting pipe and a tetrachlorosilane inlet pipe being connected to a mixer, the mixer being connected to a reactor via a sixth connecting pipe, the reactor being connected to the fifth distillation tower via a seventh connecting pipe, the fifth distillation tower being connected to an eighth connecting pipe and a ninth connecting pipe, the eighth connecting pipe being connected to a second cooler and a second adsorber, and the second adsorber being connected to the chlorosilane feed tank.

[0024] Preferably, the fourth distillation component includes at least one distillation tower.

[0025] Preferably, the first silicon tetrachloride outlet pipe is connected to the silicon tetrachloride raw material tank.

[0026] Preferably, a feeding pump is provided on the sixth connecting pipe.

[0027] Preferably, the mixer is a pipeline mixer.

[0028] Preferably, the adsorbents of the first adsorber and the second adsorber are silica gel, alumina or amino resin.

[0029] Preferably, the catalyst of the reactor is an amine anion exchange resin.

[0030] A method for purifying chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon comprises the following steps: Step 1: The chlorosilane raw material enters the first distillation tower for the first distillation separation, the output from the first distillation tower kettle flows into the silicon tetrachloride raw material tank, and the output from the top of the first distillation tower flows into the second distillation tower; Step 2: The overhead liquid of the first distillation tower is subjected to a second distillation separation in the second distillation tower, the bottom liquid of the second distillation tower flows into the third distillation tower, and the overhead liquid of the second distillation tower flows into the mixer; Step 3: The produced liquid from the kettle of the second distillation tower is subjected to a third distillation separation in the third distillation tower, and the produced liquid from the top of the third distillation tower flows into the fourth distillation assembly; Step 4: The produced liquid from the top of the third distillation tower is subjected to a fourth distillation separation in the fourth distillation assembly, the produced liquid from the bottom of the fourth distillation assembly flows into a chlorosilane storage tank, and the produced liquid from the top of the fourth distillation assembly is obtained; Step 5: The produced liquid from the bottom of the third distillation tower is subjected to adsorption and impurity removal in the first adsorber, and then flows into the chlorosilane storage tank after impurity removal.

[0031] Preferably, in step 1, the chlorosilane raw material is a chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is greater than 40°C, the mass content of trichlorosilane is 25%-35%, the mass content of dichlorodihydrosilane is 0.5%-1%, the mass content of silicon tetrachloride is 64%-74.5%, and a small amount of chlorosilane polymers and donor and acceptor impurities are contained.

[0032] Preferably, the number of theoretical plates of the first distillation tower is 80-160, the top reflux ratio of the first distillation tower is 3-6, the tower pressure of the first distillation tower is 0.1-0.8 MPaG, the temperature of the top of the first distillation tower is 51-112°C, and the temperature of the bottom of the first distillation tower is 83-147°C; the number of theoretical plates of the second distillation tower is 80-160, the feed reflux ratio of the second distillation tower is 2-5, the tower pressure of the second distillation tower is 0.2-0.5 MPaG, the temperature of the top of the second distillation tower is 41-82°C, and the temperature of the bottom of the second distillation tower is 70-97°C; the number of theoretical plates of the third distillation tower is 80-160, the top reflux ratio of the third distillation tower is 3-7, the tower pressure of the third distillation tower is 0.1-0.8 MPaG, the temperature of the top of the third distillation tower is 53-113°C, and the third distillation tower is 2-5. The temperature of the tower kettle is 55-125°C; the theoretical number of plates of the distillation tower of the fourth distillation component is 80-160, the feed reflux ratio of the distillation tower of the fourth distillation component is 3-5, the tower pressure of the distillation tower of the fourth distillation component is 0.1-0.8MpaG, the temperature of the top of the distillation tower of the fourth distillation component is 53-113°C, and the temperature of the distillation tower kettle of the fourth distillation component is 55-125°C; the temperature in the first adsorber is 10-30°C, and the residence time of the produced liquid from the third distillation tower kettle in the first adsorber is greater than 1h.

[0033] Preferably, the method further comprises the following steps: Step 31: mixing the produced liquid from the top of the second distillation tower and silicon tetrachloride in a mixer; after mixing, flowing the mixture into a reactor for reaction; Step 41: The reaction liquid obtained by the reaction flows into a fifth distillation tower for fifth distillation separation, the output from the bottom of the fifth distillation tower flows into silicon tetrachloride, and the output from the top of the fifth distillation tower flows into a second adsorber; Step 51: The produced liquid from the top of the fifth distillation tower is subjected to adsorption and impurity removal in the second adsorber, and then flows into the chlorosilane storage tank after impurity removal.

[0034] Preferably, the mass feed ratio of silicon tetrachloride to the produced liquid from the top of the second distillation tower is 2.5-6.5: the inlet temperature of silicon tetrachloride is 30-65°C, and the temperature after mixing is 50-65°C; after mixing, it flows into the reactor for reaction, the temperature of the reactor is 55-75°C, and the pressure of the reactor is 0.3-0.7MpaG; the number of plates of the fifth distillation tower is 80-160, the top reflux ratio of the fifth distillation tower is 3-6, the tower pressure of the fifth distillation tower is 0.1-0.5MpaG, the temperature of the top of the fifth distillation tower is 45-85°C, and the temperature of the kettle of the fifth distillation tower is 55-99°C; the temperature in the second adsorber is 10-30°C, and the residence time of the produced liquid from the top of the fifth distillation tower in the second adsorber is greater than 1h.

[0035] The beneficial effects of this technical solution are as follows: 1. The present invention provides a chlorosilane raw material purification system for reducing donor and acceptor impurities in polycrystalline silicon. The chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process is subjected to first distillation separation, second distillation separation, third distillation separation, and fourth distillation separation in a first distillation tower, a second distillation tower, a third distillation tower, and a fourth distillation assembly to obtain high-purity trichlorosilane (trichlorosilane concentration greater than 99.9%). Dichlorodihydrosilane in the chlorosilane raw material reacts with silicon tetrachloride in a reactor to obtain trichlorosilane, further improving the utilization rate of the chlorosilane (the theoretical utilization rate of the chlorosilane raw material is 100%, achieving closed-loop use of the raw material). A first adsorber removes B / P impurities in the form of heavy components (the B / P impurity removal rate as heavy components is greater than 90%), and a second adsorber removes B / P impurities in the form of light components (the B / P impurity removal rate as light components is greater than 90%).

[0036] 2. The present invention provides a method for purifying chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon. The method utilizes the purification function of a distillation tower to concentrate the B / P impurities in the chlorosilane raw materials to a higher concentration, and then utilizes the adsorption function of an adsorbent to adsorb the higher concentration of B / P impurities, separating the impurities from the chlorosilane raw materials, thereby reducing the impurity content in the chlorosilane. The B / P impurities can be reduced to PPB level or even PPT level, and the polysilicon produced using the chlorosilane reaches electronic grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of the present invention; Wherein: 1. first distillation tower; 2. chlorosilane raw material pipe; 3. first silicon tetrachloride outlet pipe; 4. first connecting pipe; 5. second distillation tower; 6. second connecting pipe; 7. third connecting pipe; 8. third distillation tower; 9. fourth connecting pipe; 10. fifth connecting pipe; 12. fourth distillation assembly; 13. product liquid outlet pipe; 14. chlorosilane raw material tank; 15. first adsorber; 16. tetrachlorosilane inlet pipe; 17. mixer; 18. sixth connecting pipe; 19. reactor; 20. seventh connecting pipe; 21. fifth distillation tower; 22. eighth connecting pipe; 23. ninth connecting pipe; 24. second adsorber; 25. silicon tetrachloride raw material tank; 26. feed pump; 27. first cooler; 28. second cooler. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0039] like Figure 1As shown, a chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon includes a first distillation tower 1, the first distillation tower 1 is connected to a chlorosilane raw material pipe 2, a first silicon tetrachloride outlet pipe 3 and a first connecting pipe 4, the first connecting pipe 4 is connected to a second distillation tower 5, the second distillation tower 5 is connected to a second connecting pipe 6 and a third connecting pipe 7, the second connecting pipe 6 is connected to a third distillation tower 8, the third distillation tower 8 is connected to a fourth connecting pipe 9 and a fifth connecting pipe 10, the fourth connecting pipe 9 is connected to a fourth distillation assembly 12, the fourth distillation assembly 12 is connected to a product liquid outlet pipe 13 and The chlorosilane raw material tank 14 is connected; the fifth connecting pipe 10 is connected to the first adsorber 15, and the first adsorber 15 is connected to the chlorosilane raw material tank 14; the third connecting pipe 7 and the tetrachlorosilane inlet pipe 16 are connected to the mixer 17, and the mixer 17 is connected to the reactor 19 through the sixth connecting pipe 18, and the reactor 19 is connected to the fifth distillation tower 21 through the seventh connecting pipe 20, and the fifth distillation tower 21 is connected to the eighth connecting pipe 22 and the ninth connecting pipe 23, and the eighth connecting pipe 22 is connected to the second adsorber 24, and the second adsorber 24 is connected to the chlorosilane raw material tank 14.

[0040] The fourth distillation assembly 12 includes at least one distillation tower. The produced liquid from the top of the distillation tower in the fourth distillation assembly 12 is the product liquid; and the produced liquid from the bottom of the distillation tower in the fourth distillation assembly 12 flows into the chlorosilane raw material tank 14.

[0041] The first silicon tetrachloride outlet pipe 3 is connected to the silicon tetrachloride raw material tank 25 .

[0042] Wherein, a feeding pump 26 is provided on the sixth connecting pipe 18 .

[0043] The mixer 17 is a pipeline mixer 17 .

[0044] Wherein, the adsorbents of the first adsorber and the second adsorber are silica gel, alumina or amino resin.

[0045] The catalyst of the reactor 19 is an amine anion exchange resin.

[0046] A method for purifying chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon comprises the following steps: Step 1: The chlorosilane raw material enters the first distillation tower 1 for the first distillation separation. The output from the bottom of the first distillation tower 1 flows into the silicon tetrachloride raw material tank 25, and the output from the top of the first distillation tower 1 flows into the second distillation tower 5; Step 2: The overhead liquid of the first distillation tower 1 is subjected to a second distillation separation in the second distillation tower 5. The bottom liquid of the second distillation tower 5 flows into the third distillation tower 8, and the overhead liquid of the second distillation tower 5 flows into the mixer 17. Step 3: The produced liquid from the bottom of the second distillation tower 5 is subjected to a third distillation separation in the third distillation tower 8, and the produced liquid from the top of the third distillation tower 8 flows into the fourth distillation assembly 12; Step 4: The overhead liquid of the third distillation tower 8 is subjected to a fourth distillation separation in the fourth distillation assembly 12. The bottom liquid of the fourth distillation assembly 12 flows into the chlorosilane storage tank, and the overhead liquid of the fourth distillation assembly 12 is extracted to obtain the product liquid. Step 5: The produced liquid from the bottom of the third distillation tower 8 is subjected to adsorption and impurity removal in the first adsorber 15, and then flows into the chlorosilane storage tank after impurity removal.

[0047] The following steps are also included: Step 31: The overhead liquid from the second distillation tower 5 and silicon tetrachloride are mixed in the mixer 17; after mixing, the mixture flows into the reactor 19 for reaction; Step 41: The reaction liquid is flowed into the fifth distillation tower 21 for the fifth distillation separation. The output from the bottom of the fifth distillation tower 21 flows into silicon tetrachloride, and the output from the top of the fifth distillation tower 21 flows into the second adsorber 24. Step 51: The produced liquid from the top of the fifth distillation tower 21 is subjected to adsorption and impurity removal in the second adsorber 24, and then flows into the chlorosilane storage tank after impurity removal.

[0048] Example 1 In this embodiment, in step 1, the chlorosilane raw material is a chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 40° C., the mass content of trichlorosilane is 25%, the mass content of dichlorodihydrosilane is 0.5%, the mass content of silicon tetrachloride is 74.5%, and a small amount of chlorosilane polymer and donor and acceptor impurities are contained.

[0049] Among them, the number of theoretical plates of the first distillation tower 1 is 80, the top reflux ratio of the first distillation tower 1 is 6, the tower pressure of the first distillation tower 1 is 0.8MpaG, the temperature of the top of the first distillation tower 1 is 112°C, and the temperature of the bottom of the first distillation tower 1 is 147°C; the number of theoretical plates of the second distillation tower 5 is 80, the feed reflux ratio of the second distillation tower 5 is 5, the tower pressure of the second distillation tower 5 is 0.5MpaG, the temperature of the top of the second distillation tower 5 is 72°C, and the temperature of the bottom of the second distillation tower 5 is 96°C; the number of theoretical plates of the third distillation tower 8 is 80, the top reflux ratio of the third distillation tower 8 is 7, and the third distillation tower 8 has a tower pressure of 0.8 MpaG, a temperature at the top of the third distillation tower 8 is 113°C, and a temperature at the bottom of the third distillation tower 8 is 119°C; the theoretical number of plates of the distillation tower of the fourth distillation component 12 is 80, the feed reflux ratio of the distillation tower of the fourth distillation component 12 is 5, the tower pressure of the distillation tower of the fourth distillation component 12 is 0.8 MpaG, the temperature at the top of the distillation tower of the fourth distillation component 12 is 113°C, and the temperature at the bottom of the distillation tower of the fourth distillation component 12 is 119°C; the temperature in the first adsorber 15 is 30°C, and the residence time of the produced liquid from the bottom of the third distillation tower 8 in the first adsorber 15 is 1h.

[0050] Among them, the mass feed ratio of silicon tetrachloride to the produced liquid from the top of the second distillation tower 5 is 2.5: the inlet temperature of silicon tetrachloride is 65°C, and the temperature after mixing is 65°C; after mixing, it flows into the reactor 19 for reaction, the temperature of the reactor 19 is 75°C, and the pressure of the reactor 19 is 0.6MpaG; the number of plates of the fifth distillation tower 21 is 80, the top reflux ratio of the fifth distillation tower 21 is 6, the tower pressure of the fifth distillation tower 21 is 0.5MpaG, the temperature of the top of the fifth distillation tower 21 is 85°C, and the temperature of the bottom of the fifth distillation tower 21 is 99°C; the temperature in the second adsorber 24 is 30°C, and the residence time of the produced liquid from the top of the fifth distillation tower 21 in the second adsorber 24 is 1h.

[0051] The concentration of trichlorosilane in the product liquid is 99.9%, and the content of B / P impurities is PPB level (<0.5PPB).

[0052] The B / P impurity content of the produced liquid from the bottom of the third distillation tower 8 is greater than 50 PPB. After adsorption and impurity removal in the first adsorber 15, the B / P impurity content is less than 5 PPB.

[0053] The B / P impurity content of the overhead liquid of the fifth distillation tower 21 is greater than 50 PPB. The concentration of trichlorosilane after adsorption and impurity removal in the second adsorber 24 is ≥95% (the rest is unreacted dichlorosilane), and the B / P impurity content is less than 5 PPB.

[0054] The utilization rate of chlorosilane raw materials is 100%.

[0055] Example 2 In this embodiment, in step 1, the chlorosilane raw material is a chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 45° C., the mass content of trichlorosilane is 35%, the mass content of dichlorodihydrosilane is 1%, the mass content of silicon tetrachloride is 64%, and a small amount of chlorosilane polymer and donor and acceptor impurities are contained.

[0056] Among them, the number of theoretical plates of the first distillation tower 1 is 160, the top reflux ratio of the first distillation tower 1 is 3, the tower pressure of the first distillation tower 1 is 0.1MpaG, the temperature of the top of the first distillation tower 1 is 51°C, and the temperature of the bottom of the first distillation tower 1 is 89°C; the number of theoretical plates of the second distillation tower 5 is 160, the feed reflux ratio of the second distillation tower 5 is 4, the tower pressure of the second distillation tower 5 is 0.2MpaG, the temperature of the top of the second distillation tower 5 is 43°C, and the temperature of the bottom of the second distillation tower 5 is 73°C; the number of theoretical plates of the third distillation tower 8 is 160, the top reflux ratio of the third distillation tower 8 is 3, and the third distillation tower 8 is 100. The tower pressure of tower 8 is 0.1MpaG, the temperature at the top of the third distillation tower 8 is 53°C, and the temperature at the bottom of the third distillation tower 8 is 61°C; the theoretical number of plates of the distillation tower of the fourth distillation component 12 is 160, the feed reflux ratio of the distillation tower of the fourth distillation component 12 is 3, the tower pressure of the distillation tower of the fourth distillation component 12 is 0.1MpaG, the temperature at the top of the distillation tower of the fourth distillation component 12 is 53°C, and the temperature at the bottom of the distillation tower of the fourth distillation component 12 is 61°C; the temperature in the first adsorber 15 is 10°C, and the residence time of the produced liquid from the bottom of the third distillation tower 8 in the first adsorber 15 is 1.5h.

[0057] Among them, the mass feed ratio of silicon tetrachloride to the overhead produced liquid of the second distillation tower 5 is 6.5: the inlet temperature of silicon tetrachloride is 30°C, and the temperature after mixing is raised to 50°C; after mixing, it flows into the reactor 19 for reaction, the temperature of the reactor 19 is 55°C, and the pressure of the reactor 19 is 0.3MpaG; the number of plates of the fifth distillation tower 21 is 160, the top reflux ratio of the fifth distillation tower 21 is 3, the tower pressure of the fifth distillation tower 21 is 0.1MpaG, the temperature of the top of the fifth distillation tower 21 is 51°C, and the temperature of the bottom of the fifth distillation tower 21 is 61°C; the temperature in the second adsorber 24 is 10°C, and the residence time of the overhead produced liquid of the fifth distillation tower 21 in the second adsorber 24 is 1.5h.

[0058] The concentration of trichlorosilane in the product liquid is 99.9%, and the content of B / P impurities is PPB level (<0.5PPB).

[0059] The B / P impurity content of the produced liquid from the bottom of the third distillation tower 8 is greater than 50 PPB. After adsorption and impurity removal in the first adsorber 15, the B / P impurity content is less than 5 PPB.

[0060] The B / P impurity content of the overhead liquid of the fifth distillation tower 21 is greater than 50 PPB. After adsorption and impurity removal in the second adsorber 24, the concentration of trichlorosilane is 95% (the rest is unreacted dichlorosilane), and the B / P impurity content is less than 5 PPB.

[0061] The utilization rate of chlorosilane raw materials is 100%.

[0062] Example 3 In this embodiment, in step 1, the chlorosilane raw material is a chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 40° C., the mass content of trichlorosilane is 30%, the mass content of dichlorodihydrosilane is 0.5%, the mass content of silicon tetrachloride is 69.5%, and a small amount of chlorosilane polymer and donor and acceptor impurities are contained.

[0063] Among them, the number of theoretical plates of the first distillation tower 1 is 120, the top reflux ratio of the first distillation tower 1 is 5, the tower pressure of the first distillation tower 1 is 0.5 MPaG, the temperature of the top of the first distillation tower 1 is 93-95° C., and the temperature of the bottom of the first distillation tower 1 is 128-131° C.; the number of theoretical plates of the second distillation tower 5 is 120, the feed reflux ratio of the second distillation tower 5 is 3, the tower pressure of the second distillation tower 5 is 0.3 MPaG, the temperature of the top of the second distillation tower 5 is 50-56° C., and the temperature of the bottom of the second distillation tower 5 is 71-74° C.; the number of theoretical plates of the third distillation tower 8 is 80-120, the top reflux ratio of the third distillation tower 8 is 5, The tower pressure of the third distillation tower 8 is 0.5MpaG, the temperature at the top of the third distillation tower 8 is 94-95°C, and the temperature at the bottom of the third distillation tower 8 is 97-105°C; the theoretical number of plates of the distillation tower of the fourth distillation component 12 is 120, the feed reflux ratio of the distillation tower of the fourth distillation component 12 is 4, the tower pressure of the fourth distillation tower is 0.5MpaG, the temperature at the top of the distillation tower of the fourth distillation component 12 is 94-95°C, and the temperature at the bottom of the distillation tower of the fourth distillation component 12 is 97-105°C; the temperature in the first adsorber 15 is 10-30°C, and the residence time of the produced liquid from the bottom of the third distillation tower 8 in the first adsorber 15 is 1h.

[0064] Among them, the mass feed ratio of silicon tetrachloride to the overhead produced liquid of the second distillation tower 5 is 5; the inlet temperature of silicon tetrachloride is <60°C, and the temperature after mixing and heating is 57°C; after mixing, it flows into the reactor 19 for reaction, the temperature of the reactor 19 is 60°C, and the pressure of the reactor 19 is 0.45MpaG; the number of plates of the fifth distillation tower 21 is 120, the top reflux ratio of the fifth distillation tower 21 is 5, the tower pressure of the fifth distillation tower 21 is 0.3MpaG, the temperature of the top of the fifth distillation tower 21 is 64-68°C, and the temperature of the bottom of the fifth distillation tower 21 is 94-98°C; the temperature in the second adsorber 24 is 10-30°C, and the residence time of the overhead produced liquid of the fifth distillation tower 21 in the second adsorber 24 is 1h.

[0065] The concentration of trichlorosilane in the product liquid is 99.9%, and the content of B / P impurities is <0.5PPB.

[0066] The B / P impurity content of the produced liquid from the bottom of the third distillation tower 8 is greater than 50 PPB. After adsorption and impurity removal in the first adsorber 15, the B / P impurity content is less than 5 PPB.

[0067] The B / P impurity content of the overhead liquid of the fifth distillation tower 21 is greater than 50 PPB. After adsorption and impurity removal in the second adsorber 24, the concentration of trichlorosilane is 95% (the rest is unreacted dichlorosilane), and the B / P impurity content is less than 5 PPB.

[0068] The utilization rate of chlorosilane raw materials is 100%.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention is within the scope of protection of the present invention.

Claims

1. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon, characterized by: The invention comprises a first distillation tower (1), wherein the first distillation tower (1) is connected to a chlorosilane raw material pipe (2), a first silicon tetrachloride outlet pipe (3) and a first connecting pipe (4), the first connecting pipe (4) is connected to a second distillation tower (5), the second distillation tower (5) is connected to a second connecting pipe (6) and a third connecting pipe (7), the second connecting pipe (6) is connected to a third distillation tower (8), the third distillation tower (8) is connected to a fourth connecting pipe (9) and a fifth connecting pipe (10), the fourth connecting pipe (9) is connected to a fourth distillation assembly (12), the fourth distillation assembly (12) is connected to a product liquid outlet pipe (13) and a chlorosilane raw material tank (14); the fifth connecting pipe (10) is connected to the first distillation tower (11), the second distillation tower (12) is connected to the product liquid outlet pipe (13) and the chlorosilane raw material tank (14); the fifth connecting pipe (10) is connected to the first distillation tower (12), the third distillation tower (12) is connected to the product liquid outlet pipe (13) and the chlorosilane raw material tank (14); the fifth connecting pipe (10) is connected to the first distillation tower (1 ... A cooler (27) is connected to the first adsorber (15), and the first adsorber (15) is connected to the chlorosilane raw material tank (14); the third connecting pipe (7) and the tetrachlorosilane inlet pipe (16) are connected to the mixer (17); the mixer (17) is connected to the reactor (19) via the sixth connecting pipe (18); the reactor (19) is connected to the fifth distillation tower (21) via the seventh connecting pipe (20); the fifth distillation tower (21) is connected to the eighth connecting pipe (22) and the ninth connecting pipe (23); the eighth connecting pipe (22) is connected to the second cooler (28) and the second adsorber (24); and the second adsorber (24) is connected to the chlorosilane raw material tank (14).

2. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: The fourth distillation component (12) includes at least one distillation tower.

3. The chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: The first silicon tetrachloride outlet pipe (3) is connected to the silicon tetrachloride raw material tank (25).

4. The chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: A feeding pump (26) is provided on the sixth connecting pipe (18).

5. The chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: The mixer (17) is a pipeline mixer.

6. The chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: The adsorbents of the first adsorber (15) and the second adsorber (24) are silica gel, alumina or amino resin.

7. The chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 1, characterized in that: The catalyst of the reactor (19) is an amine anion exchange resin.

8. A method for purifying chlorosilane raw materials to reduce the concentration of donor and acceptor impurities in polysilicon, characterized in that: The following steps are involved: Step 1: The chlorosilane raw material enters the first distillation tower (1) for the first distillation separation, the bottom of the first distillation tower (1) is drawn into the silicon tetrachloride raw material tank (25), and the top of the first distillation tower (1) is drawn into the second distillation tower (5); Step 2: the overhead liquid of the first distillation tower (1) is subjected to a second distillation separation in the second distillation tower (5); the bottom liquid of the second distillation tower (5) flows into the third distillation tower (8); and the overhead liquid of the second distillation tower (5) flows into the mixer (17); Step 3: The produced liquid from the bottom of the second distillation tower (5) is subjected to a third distillation separation in the third distillation tower (8), and the produced liquid from the top of the third distillation tower (8) flows into the fourth distillation assembly (12); Step 4: the top produced liquid of the third distillation tower (8) is subjected to a fourth distillation separation in the fourth distillation assembly (12); the bottom produced liquid of the fourth distillation assembly (12) flows into a chlorosilane storage tank; the top produced liquid of the fourth distillation assembly (12) is obtained; Step 5: The produced liquid from the bottom of the third distillation tower (8) is subjected to adsorption and impurity removal in the first adsorber (15), and then flows into the chlorosilane storage tank after impurity removal.

9. The method for purifying chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 8, characterized in that: In step 1, the chlorosilane raw material is a chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is greater than 40° C., the mass content of trichlorosilane is 25%-35%, the mass content of dichlorodihydrosilane is 0.5%-1%, the mass content of silicon tetrachloride is 64%-74.5%, and a small amount of chlorosilane polymer and donor and acceptor impurities are contained.

10. The method for purifying chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 8, characterized in that: The number of theoretical plates of the first distillation tower (1) is 80-160, the reflux ratio of the top of the first distillation tower (1) is 3-6, the tower pressure of the first distillation tower (1) is 0.1-0.8 MPaG, the temperature of the top of the first distillation tower (1) is 51-112°C, and the temperature of the bottom of the first distillation tower (1) is 83- 147°C; the number of theoretical plates of the second distillation tower (5) is 80-160, the feed reflux ratio of the second distillation tower (5) is 2-5, the tower pressure of the second distillation tower (5) is 0.2-0.5MpaG, the temperature of the top of the second distillation tower (5) is 41-82°C, and the temperature of the bottom of the second distillation tower (5) is 70-97°C; the number of theoretical plates of the third distillation tower (8) is 80-160, the tower reflux ratio of the top of the third distillation tower (8) is 3-7, the tower pressure of the third distillation tower (8) is 0.1-0.8MpaG, the tower temperature of the top of the third distillation tower (8) is 53-113°C, and the tower temperature of the third distillation tower (8) is 53-113°C. ) The temperature of the bottom of the tower is 55-125°C; the theoretical number of plates of the distillation tower of the fourth distillation component (12) is 80-160, the feed reflux ratio of the distillation tower of the fourth distillation component (12) is 3-5, the tower pressure of the distillation tower of the fourth distillation component (12) is 0.1-0.8MpaG, the temperature of the top of the distillation tower of the fourth distillation component (12) is 53-113°C, and the temperature of the bottom of the distillation tower of the fourth distillation component (12) is 55-125°C; the temperature in the first adsorber (15) is 10-30°C, and the residence time of the produced liquid from the bottom of the third distillation tower (8) in the first adsorber (15) is greater than 1h.

11. The method for purifying chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 8, characterized in that: The following steps are also included: Step 31: The overhead liquid from the second distillation tower (5) and silicon tetrachloride are mixed in a mixer (17); after mixing, the mixture flows into a reactor (19) for reaction; Step 41: the reaction liquid is flowed into the fifth distillation tower (21) for the fifth distillation separation, the output from the bottom of the fifth distillation tower (21) is flowed into silicon tetrachloride, and the output from the top of the fifth distillation tower (21) is flowed into the second adsorber (24); Step 51: The produced liquid from the top of the fifth distillation tower (21) is subjected to adsorption and impurity removal in the second adsorber (24), and then flows into the chlorosilane storage tank after impurity removal.

12. The method for purifying chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 11, characterized in that: The mass feed ratio of silicon tetrachloride to the produced liquid from the top of the second distillation tower (5) is 2.5-6.5: the inlet temperature of silicon tetrachloride is 30-65°C, and the temperature after mixing is 50-65°C; after mixing, it flows into the reactor (19) for reaction, the temperature of the reactor (19) is 55-75°C, and the pressure of the reactor (19) is 0.3-0.7 MPaG; the number of plates of the fifth distillation tower (21) is 80-160, the top reflux ratio of the fifth distillation tower (21) is 3-6, the tower pressure of the fifth distillation tower (21) is 0.1-0.5 MPaG, the top temperature of the fifth distillation tower (21) is 45-85°C, and the bottom temperature of the fifth distillation tower (21) is 55-99°C; the temperature in the second adsorber (24) is 10-30°C, and the residence time of the produced liquid from the top of the fifth distillation tower (21) in the second adsorber (24) is greater than 1 hour.

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