System and method for removing carbon impurities in chlorosilane

Abstract

The invention discloses a system and a method for removing carbon impurities in chlorosilane, and belongs to the technical field of polycrystalline silicon production, a chlorosilane raw material produced in a cold hydrogenation or trichlorosilane synthesis process is subjected to first rectification separation, second rectification separation, third rectification separation, fourth rectification separation and fifth rectification separation to obtain high-purity trichlorosilane; dichlorosilane in the chlorosilane raw material reacts with silicon tetrachloride in the reactor to obtain trichlorosilane, so that the utilization rate of chlorosilane is further increased; the sixth rectifying tower is used for separating high-carbon chlorosilane which exists in the form of methyl chlorosilane and is discharged from tower kettles of the third rectifying tower and the fifth rectifying tower, the seventh rectifying tower is used for further concentrating the high-carbon chlorosilane discharged from the tower kettle of the sixth rectifying tower, the concentrated material is discharged from the tower kettle of the seventh rectifying tower, the part of the material is high in carbon impurity content, and the content of methyl chlorosilane is low. The high-carbon material is subjected to high-pressure cryogenic treatment, methyl chlorosilane is cooled into a solid state, and chlorosilane is recovered after filtration.

Description

Technical Field

[0001] The present invention belongs to the technical field of polysilicon production, and in particular relates to a system and method for removing carbon impurities from chlorosilane. Background Art

[0002] The chlorosilane decarbonization process is a method for decarbonizing chlorosilane in polysilicon production. At present, the production of polysilicon mainly adopts the trichlorosilane reduction method. The trichlorosilane synthesis of this method uses industrial silicon powder, H2, hydrogen chloride and silicon tetrachloride as raw materials. Under the action of the catalyst in the hydrogenation furnace, a reaction occurs to produce trichlorosilane. In this process, carbon-containing impurities such as methyldichlorosilane, methyltrichlorosilane, and dimethylchlorosilane will be produced. These carbon-containing impurities will be deposited in the silicon element, affecting the carbon index in the polysilicon to exceed the standard, and need to be separated before the trichlorosilane reduction reaction. The trichlorosilane purification process uses a distillation separation process, which uses the difference in boiling points between different substances for separation. Since the boiling point of methyldichlorosilane is 41°C, which is close to the boiling point of trichlorosilane (32°C), in order to reduce the content of methyldichlorosilane, a distillation tower with a high theoretical plate number and reflux ratio is required, resulting in high investment and operating costs for the distillation device. With the continuous development of science and technology, people have increasingly higher requirements for the manufacturing process of chlorosilane decarbonization process.

[0003] The existing chlorosilane decarbonization process has certain drawbacks when used. The reactive distillation tower has safety issues such as the need to stop and overhaul when replacing the catalyst. The raw materials need to be pretreated before entering the reactor, and the decarbonization conversion rate is incomplete. The treated silicon tetrachloride and monomethyltrichlorosilane need to be further separated downstream. Patent CN109179426A proposes a method for reactive decarbonization, in which pretreated silicon tetrachloride and carbon-containing trichlorosilane are sent to a reactive distillation tower for chlorine atom redistribution reaction, and through the separation effect of reactive distillation, the reaction product trichlorosilane is extracted from the top of the tower, and the excess silicon tetrachloride and the generated methyltrichlorosilane are extracted from the bottom of the tower. This invention converts methyldichlorosilane, which is difficult to separate from trichlorosilane, into methyltrichlorosilane that is easy to separate by converting the reactive carbon, thereby achieving the decarbonization function of trichlorosilane. However, this reactive distillation technology requires the tower to be shut down when the catalyst in the tower fails and needs to be replaced, which affects the production stability of the system and brings safety risks. Excess silicon tetrachloride and monomethyltrichlorosilane are extracted from the bottom of the tower and need to be separated downstream, which places a burden on downstream separation. To prevent catalyst poisoning, a treatment device must be installed before entering the tower, making the decarbonization system more complicated.

[0004] Patent CN110980742A proposes a reactive decarbonization method that extracts unreacted chlorine donors through a side stream and returns them to the column for further reaction, allowing monomethyldichlorosilane to be extracted from the column bottom. This fully utilizes the chlorine donors, but it still presents a series of problems caused by replacing the reactive distillation catalyst after it expires. Furthermore, it is difficult to completely separate the chlorine donors from monomethyldichlorosilane in the side stream. Patent CN114956092A proposes a method for decarbonizing trichlorosilane. Carbon-containing trichlorosilane reacts with a resin catalyst, and the resulting materials are distilled and separated, yielding silicon tetrachloride and monomethyltrichlorosilane at the bottom. This process does not completely convert monomethyldichlorosilane, and the subsequent separation of silicon tetrachloride and monomethyltrichlorosilane is also incomplete. Patent CN 212740754 U proposes a trichlorosilane decarbonization reaction and distillation method, including a reactive distillation tower and a series of distillation towers. To improve the decarbonization conversion rate, multiple reactive distillation towers are set up in series or parallel, further increasing the complexity of the reactive distillation. We have proposed a process for decarbonizing chlorosilane in polysilicon production. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a system and method for removing carbon impurities from chlorosilane. The chlorosilane raw material produced by the cold hydrogenation or trichlorosilane synthesis process is subjected to the first distillation separation, the second distillation separation, the third distillation separation, the fourth distillation separation and the fifth distillation separation to obtain high-purity trichlorosilane (the concentration of trichlorosilane needs to be greater than 99.9%); the dichlorodihydrosilane in the chlorosilane raw material reacts with silicon tetrachloride in the reactor to obtain trichlorosilane, which further improves the utilization rate of chlorosilane (the utilization rate of chlorosilane raw material is theoretically The sixth distillation tower separates the high-carbon chlorosilane in the form of methylchlorosilane discharged from the kettles of the third distillation tower and the fifth distillation tower. The seventh distillation tower further concentrates the high-carbon chlorosilane discharged from the kettle of the sixth distillation tower. The concentrated material is discharged from the kettle of the seventh distillation tower. This part of the material has a high carbon impurity content (it can be highly concentrated through process adjustment, for example, to 5000-50000 ppm). This part of the high-carbon material is subjected to high-pressure cryogenic cooling to cool the methylchlorosilane into a solid state. After filtering, the chlorosilane is recovered.

[0006] The purpose of the present invention is achieved through the following technical solutions: A system for removing carbon impurities from chlorosilanes comprises a first distillation tower, wherein the first distillation tower is connected to a chlorosilane raw material pipe, a first silicon tetrachloride outlet pipe and a first connecting pipe, the first connecting pipe is connected to a second distillation tower, the second distillation tower is connected to a second connecting pipe and a first external pipe, the second connecting pipe is connected to a third distillation tower, the third distillation tower is connected to a fourth connecting pipe and a fifth connecting pipe, the fourth connecting pipe is connected to a fourth distillation tower, the fourth distillation tower is connected to the second external pipe and a sixth connecting pipe, the sixth connecting pipe is connected to a fifth distillation tower, the fifth distillation tower is connected to a product The liquid outlet pipe is connected to the seventh connecting pipe, the fifth connecting pipe is connected to the seventh connecting pipe and then flows into the sixth distillation tower, the sixth distillation tower is connected to the eighth connecting pipe and the third external pipe, the eighth connecting pipe is connected to the seventh distillation tower, the seventh distillation tower is connected to the fourth external pipe and the ninth connecting pipe, the ninth connecting pipe is connected to the deep cold filtration unit, the deep cold filtration unit is connected to the tenth connecting pipe and the fifth external pipe, the tenth connecting pipe is connected to the heat exchanger, the heat exchanger is connected to the sixth external pipe, the third external pipe, the fourth external pipe and the sixth external pipe are all connected to the chlorosilane raw material tank.

[0007] Preferably, the first silicon tetrachloride outlet pipe is connected to a silicon tetrachloride raw material system.

[0008] Preferably, the first outer row pipe is connected to a dichlorosilane treatment unit.

[0009] Preferably, the second outer row pipe is connected to the light component processing unit.

[0010] Preferably, the fifth outer row pipe is connected to the methylchlorosilane treatment unit.

[0011] Preferably, the deep cold filtration unit adopts a low temperature freezing device.

[0012] A method for removing carbon impurities from chlorosilanes 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 storage 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 dichlorosilane treatment process; Step 3, the produced liquid from the bottom of the second distillation tower is subjected to a third distillation separation in the third distillation tower, the top produced from the third distillation tower flows into the fourth distillation tower, and the produced liquid from the bottom of the third distillation tower flows into the sixth distillation tower; Step 4: The overhead liquid of the third distillation tower is subjected to a fourth distillation separation in the fourth distillation tower. The overhead liquid of the fourth distillation tower flows into the light component processing unit, and the bottom liquid of the fourth distillation tower flows into the fifth distillation tower. Step 5: The produced liquid from the bottom of the fourth distillation tower is subjected to the fifth distillation separation in the fifth distillation tower. The produced liquid from the top of the fifth distillation tower is high-purity trichlorosilane. The produced liquid from the bottom of the fifth distillation tower flows into the sixth distillation tower.

[0013] Preferably, in step 1, the chlorosilane raw material is a chlorosilane raw material produced by a cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 30-80°C, the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl4 70-75%, SiHCl3 25-30%, and SiH2Cl2 ≤ 1.5%; the chlorosilane raw material produced by the trichlorosilane synthesis process includes SiCl4 10-20%, SiHCl3 80-90%, and SiH2Cl2 ≤ 1.5%.

[0014] 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 top temperature of the first distillation tower is 51-112°C, and the bottom temperature of the first distillation tower is 83- 147℃; the theoretical plate number 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 0.2~0.5MpaG, the temperature of the top of the second distillation tower is 41~82℃, and the temperature of the bottom of the second distillation tower is 70~97℃; the theoretical plate number 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 0.1~0.8MpaG, the temperature of the top of the third distillation tower is 53~113℃, and the temperature of the bottom of the third distillation tower is 55~125 ℃; the number of theoretical plates of the fourth distillation tower is 60~160, the feed reflux ratio of the fourth distillation tower is 3~6, the tower pressure of the fourth distillation tower is 0.1~0.8MpaG, the temperature of the top of the fourth distillation tower is 53~113℃, and the temperature of the bottom of the fourth distillation tower is 55~125℃; the number of theoretical plates of the fifth distillation tower is 60~160, the reflux ratio of the fifth distillation tower is 2~5, the tower pressure of the fifth distillation tower is 0.05~0.8MpaG, the temperature of the top of the fifth distillation tower is 52~112℃, and the temperature of the bottom of the fifth distillation tower is 55~124℃.

[0015] Preferably, the method further comprises the following steps: Step 6: The produced liquid from the bottom of the third distillation tower and / or the produced liquid from the bottom of the fifth distillation tower is subjected to a sixth distillation separation in a sixth distillation tower, the produced liquid from the bottom of the sixth distillation tower flows into a seventh distillation tower, and the produced liquid from the top of the sixth distillation tower flows into a chlorosilane feed tank; Step 7, the produced liquid from the bottom of the sixth distillation tower is subjected to a seventh distillation separation in the seventh distillation tower, the produced liquid from the bottom of the seventh distillation tower flows into a deep cold filtration unit, and the produced liquid from the top of the seventh distillation tower flows into a chlorosilane raw material tank; Step 8: The produced liquid from the seventh distillation tower is filtered and separated in a deep cold filtration unit, the separated impurities flow into the methylchlorosilane treatment process, and the filtered liquid flows into a heat exchanger; Step 9: The filtered liquid flows into the chlorosilane raw material tank after heat exchange in the heat exchanger.

[0016] Preferably, the number of theoretical plates of the sixth distillation tower is 80~160, the reflux ratio of the sixth distillation tower is 5~8, the tower pressure of the sixth distillation tower is 0.05~0.5MpaG, the temperature of the top of the sixth distillation tower is 44~95°C, and the temperature of the bottom of the sixth distillation tower is 45~96°C; the number of theoretical plates of the seventh distillation tower is 80~160, the reflux ratio of the seventh distillation tower is 6~15, the tower pressure of the seventh distillation tower is 0.05~0.5MpaG, the temperature of the top of the seventh distillation tower is 44~95°C, and the temperature of the bottom of the seventh distillation tower is 45~96°C; the pressure of the deep cooling and filtration unit is 0.1~0.5MpaG, and the temperature of the deep cooling and filtration unit is -150~-160°C.

[0017] The beneficial effects of this technical solution are as follows: 1. The present invention provides a method for removing carbon impurities from chlorosilanes. The chlorosilane raw material produced by cold hydrogenation or trichlorosilane synthesis processes is subjected to first, second, third, fourth, and fifth distillation separations to obtain high-purity trichlorosilane (the trichlorosilane concentration needs to be 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 utilization rate of the chlorosilane raw material is theoretically 100%). A sixth distillation tower separates high-carbon chlorosilanes in the form of methylchlorosilane discharged from the bottoms of the third and fifth distillation towers. A seventh distillation tower further concentrates the high-carbon chlorosilane discharged from the bottom of the sixth distillation tower. The concentrated material is discharged from the bottom of the seventh distillation tower. The carbon impurities in this material are very high (adjustable to 5000-50000 ppm through process adjustment). This high-carbon material is subjected to high-pressure cryogenic cooling to cool the methylchlorosilane to a solid state. After filtration, the chlorosilane is recovered.

[0018] 2. The present invention provides a method for removing carbon impurities from chlorosilane. By utilizing the difference in freezing point between chlorosilane and methylchlorosilane, methylchlorosilane preferentially solidifies into solid particles at ultra-low temperatures of -150 to -160°C, enabling better separation of solid and liquid. The present invention can remove more than 98% of the carbon-containing methylchlorosilane from trichlorosilane, and the substituted carbon in the polysilicon produced by reducing trichlorosilane reaches electronic grade, and can be at least better than the level of electronic premium grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention; Wherein: 1. First distillation tower; 2. Second distillation tower; 3. Third distillation tower; 4. Fourth distillation tower; 5. Fifth distillation tower; 6. Sixth distillation tower; 7. Seventh distillation tower; 8. Cryogenic filtration unit; 9. Heat exchanger; 10. Chlorosilane feed tank; 11. Silicon tetrachloride feed system; 12. Dichlorodihydrosilane treatment unit; 13. Light component treatment unit; 14. Methylchlorosilane treatment unit; 101. Chlorosilane feed pipe; 102. First silicon tetrachloride outlet pipe; 1 03. First connecting pipe; 104. Second connecting pipe; 105. First external pipe; 106. Fourth connecting pipe; 107. Fifth connecting pipe; 108. Second external pipe; 109. Sixth connecting pipe; 110. Product liquid outlet pipe; 111. Seventh connecting pipe; 112. Eighth connecting pipe; 113. Third external pipe; 114. Fourth external pipe; 115. Ninth connecting pipe; 116. Tenth connecting pipe; 117. Fifth external pipe; 118. Sixth external pipe. DETAILED DESCRIPTION

[0020] 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.

[0021] like Figure 1 As shown, a system for removing carbon impurities from chlorosilane includes a first distillation tower 1, wherein the first distillation tower 1 is connected to a chlorosilane raw material pipe 101, a first silicon tetrachloride outlet pipe 102, and a first connecting pipe 103, the first connecting pipe 103 is connected to a second distillation tower 2, the second distillation tower 2 is connected to a second connecting pipe 104 and a first external pipe 105, the second connecting pipe 104 is connected to a third distillation tower 3, the third distillation tower 3 is connected to a fourth connecting pipe 106 and a fifth connecting pipe 107, the fourth connecting pipe 106 is connected to a fourth distillation tower 4, the fourth distillation tower 4 is connected to a second external pipe 108 and a sixth connecting pipe 109, the sixth connecting pipe 109 is connected to a fifth distillation tower 5, and the fifth distillation tower 5 is connected to a product liquid outlet pipe 1 10 is connected to the seventh connecting pipe 111, the fifth connecting pipe 107 is connected to the seventh connecting pipe 111 and then flows into the sixth distillation tower 6, the sixth distillation tower 6 is connected to the eighth connecting pipe 112 and the third external pipe 113, the eighth connecting pipe 112 is connected to the seventh distillation tower 7, the seventh distillation tower 7 is connected to the fourth external pipe 114 and the ninth connecting pipe 115, the ninth connecting pipe 115 is connected to the deep cold filtration unit 8, the deep cold filtration unit 8 is connected to the tenth connecting pipe 116 and the fifth external pipe 117, the tenth connecting pipe 116 is connected to the heat exchanger 9, the heat exchanger 9 is connected to the sixth external pipe 118, the third external pipe 113, the fourth external pipe 114 and the sixth external pipe 118 are all connected to the chlorosilane raw material tank 10.

[0022] The first silicon tetrachloride outlet pipe 102 is connected to a silicon tetrachloride raw material system 11. The silicon tetrachloride raw material system 11 is conventional, and includes, for example, a silicon tetrachloride raw material tank, a silicon tetrachloride connecting pipe, and a silicon tetrachloride delivery pump.

[0023] The first external pipe 105 is connected to the dichlorosilane treatment unit 12. The dichlorosilane treatment unit 12 includes a mixer for dichlorosilane and silicon tetrachloride. The mixed material is pressurized to 0.8-1.2 MPa by a pump, heated to 50-65°C by a heat exchanger 9, and then passes through a reaction column for a deproportionation reaction (SiH2Cl2+SiCl4→SiHCl3). The resulting raw material trichlorosilane, along with unreacted silicon tetrachloride and dichlorosilane, enters the cooler of the next process for cooling. After the temperature drops to 10-20°C, it enters an adsorption column for impurity adsorption. The adsorbed material then enters the original chlorosilane storage tank as raw material for distillation.

[0024] The second outer pipe 108 is connected to the light component processing unit 13. The light component processing unit 13 includes a condenser and an adsorber. After the light component is cooled, it absorbs and removes light component impurities. It can also return to the raw material tank as raw material. The light component processing unit 13 is prior art and will not be described in detail here.

[0025] The fifth outer pipe 117 is connected to the methylchlorosilane processing unit 14. The methylchlorosilane processing unit 14 includes a methylchlorosilane storage tank and a heating system to melt the solidified methylchlorosilane into liquid. The methylchlorosilane processing unit 14 is prior art and will not be described in detail here.

[0026] The cryogenic filtration unit 8 is a cryogenic freezing device. The cryogenic freezing device solidifies the methylchlorosilane into a solid, thereby separating it from the liquid chlorosilane. The cryogenic freezing device is a prior art and will not be described in detail here.

[0027] A method for removing carbon impurities from chlorosilanes comprises the following steps: 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 extracted and flows into the silicon tetrachloride storage tank, and the top of the first distillation tower 1 is extracted and flows into the second distillation tower 2; Step 2: The overhead liquid of the first distillation tower 1 is subjected to a second distillation separation in the second distillation tower 2; the bottom liquid of the second distillation tower 2 flows into the third distillation tower 3; and the overhead liquid of the second distillation tower 2 flows into the dichlorosilane treatment process; Step 3, the produced liquid from the bottom of the second distillation tower 2 is subjected to a third distillation separation in the third distillation tower 3, the top produced from the third distillation tower 3 flows into the fourth distillation tower 4, and the bottom produced from the third distillation tower 3 flows into the sixth distillation tower 6; Step 4: The overhead liquid of the third distillation tower 3 is subjected to a fourth distillation separation in the fourth distillation tower 4. The overhead liquid of the fourth distillation tower 4 flows into the light component processing unit 13, and the bottom liquid of the fourth distillation tower 4 flows into the fifth distillation tower 5; Step 5: The produced liquid from the bottom of the fourth distillation tower 4 is subjected to the fifth distillation separation in the fifth distillation tower 5 . The produced liquid from the top of the fifth distillation tower 5 is high-purity trichlorosilane. The produced liquid from the bottom of the fifth distillation tower 5 flows into the sixth distillation tower 6 .

[0028] Wherein, in the step 1, the chlorosilane raw material is a chlorosilane raw material produced by a cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 30-80°C, the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl470-75%, SiHCl325-30%, and SiH2Cl2≤1.5%; the chlorosilane raw material produced by the trichlorosilane synthesis process includes SiCl410-20%, SiHCl380-90%, and SiH2Cl2≤1.5%.

[0029] Among them, the number of theoretical plates of the first distillation tower 1 is 80~160, the top reflux ratio of the first distillation tower 1 is 3~6, the tower pressure of the first distillation tower 1 is 0.1~0.8MpaG, the temperature of the top of the first distillation tower 1 is 51~112℃, and the temperature of the bottom of the first distillation tower 1 is 83~147℃; the number of theoretical plates of the second distillation tower 2 is 80~160, the feed reflux ratio of the second distillation tower 2 is 2~5, the tower pressure of the second distillation tower 2 is 0.2~0.5MpaG, the temperature of the top of the second distillation tower 2 is 41~82℃, and the temperature of the bottom of the second distillation tower 2 is 70~97℃; the number of theoretical plates of the third distillation tower 3 is 80~160, the top reflux ratio of the third distillation tower 3 is 3~7, and the tower pressure of the third distillation tower 3 is 0 .1~0.8MpaG, the temperature of the top of the third distillation tower 3 is 53~113℃, and the temperature of the bottom of the third distillation tower 3 is 55~125℃; the number of theoretical plates of the fourth distillation tower 4 is 60~160, the feed reflux ratio of the fourth distillation tower 4 is 3~6, the tower pressure of the fourth distillation tower 4 is 0.1~0.8MpaG, the temperature of the top of the fourth distillation tower 4 is 53~113℃, and the temperature of the bottom of the fourth distillation tower 4 is 55~125℃; the number of theoretical plates of the fifth distillation tower 5 is 60~160, the reflux ratio of the fifth distillation tower 5 is 2~5, the tower pressure of the fifth distillation tower 5 is 0.05~0.8MpaG, the temperature of the top of the fifth distillation tower 5 is 52~112℃, and the temperature of the bottom of the fifth distillation tower 5 is 55~124℃.

[0030] The following steps are also included: Step 6: The produced liquid from the bottom of the third distillation tower 3 and / or the produced liquid from the bottom of the fifth distillation tower 5 is subjected to a sixth distillation separation in the sixth distillation tower 6. The produced liquid from the bottom of the sixth distillation tower 6 flows into the seventh distillation tower 7, and the produced liquid from the top of the sixth distillation tower 6 flows into the chlorosilane raw material tank 10. Step 7, the produced liquid from the bottom of the sixth distillation tower 6 is subjected to a seventh distillation separation in the seventh distillation tower 7, the produced liquid from the bottom of the seventh distillation tower 7 flows into the deep cold filtration unit 8, and the produced liquid from the top of the seventh distillation tower 7 flows into the chlorosilane raw material tank 10; Step 8: The produced liquid from the bottom of the seventh distillation tower 7 is filtered and separated in a deep cold filtration unit 8, and the separated impurities flow into the methylchlorosilane treatment process, and the filtered liquid flows into a heat exchanger 9; Step 9: The filtered liquid flows into the chlorosilane raw material tank 10 after heat exchange in the heat exchanger 9.

[0031] Among them, the number of theoretical plates of the sixth distillation tower 6 is 80-160, the reflux ratio of the sixth distillation tower 6 is 5-8, the tower pressure of the sixth distillation tower 6 is 0.05-0.5 MPaG, the temperature at the top of the sixth distillation tower 6 is 44-95°C, and the temperature at the bottom of the sixth distillation tower 6 is 45-96°C; the number of theoretical plates of the seventh distillation tower 7 is 80-160, the reflux ratio of the seventh distillation tower 7 is 6-15, the tower pressure of the seventh distillation tower 7 is 0.05-0.5 MPaG, the temperature at the top of the seventh distillation tower 7 is 44-95°C, and the temperature at the bottom of the seventh distillation tower 7 is 45-96°C; the pressure of the deep cooling and filtration unit is 0.1-0.5 MPaG, and the temperature of the deep cooling and filtration unit is -150--160°C.

[0032] Example 1 In this embodiment, in step 1, the temperature of the chlorosilane raw material is 80° C., and the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl 4 70%, SiHCl 3 28.5%, and SiH 2 Cl 21.5%.

[0033] 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 2 is 80, the feed reflux ratio of the second distillation tower 2 is 5, the tower pressure of the second distillation tower 2 is 0.5MpaG, the temperature of the top of the second distillation tower 2 is 82°C, and the temperature of the bottom of the second distillation tower 2 is 97°C; the number of theoretical plates of the third distillation tower 3 is 80, the top reflux ratio of the third distillation tower 3 is 7, and the tower pressure of the third distillation tower 3 is 0.8MpaG. is 0.8MpaG, the temperature of the top of the third distillation tower 3 is 113°C, and the temperature of the bottom of the third distillation tower 3 is 125°C; the number of theoretical plates of the fourth distillation tower 4 is 60, the feed reflux ratio of the fourth distillation tower 4 is 6, the tower pressure of the fourth distillation tower 4 is 0.8MpaG, the temperature of the top of the fourth distillation tower 4 is 113°C, and the temperature of the bottom of the fourth distillation tower 4 is 125°C; the number of theoretical plates of the fifth distillation tower 5 is 60, the reflux ratio of the fifth distillation tower 5 is 5, the tower pressure of the fifth distillation tower 5 is 0.8MpaG, the temperature of the top of the fifth distillation tower 5 is 112°C, and the temperature of the bottom of the fifth distillation tower 5 is 124°C.

[0034] The number of theoretical plates of the sixth distillation tower 6 is 80, the reflux ratio of the sixth distillation tower 6 is 8, the tower pressure of the sixth distillation tower 6 is 0.5 MPaG, the temperature at the top of the sixth distillation tower 6 is 95°C, and the temperature at the bottom of the sixth distillation tower 6 is 96°C; the number of theoretical plates of the seventh distillation tower 7 is 80, the reflux ratio of the seventh distillation tower 7 is 15, the tower pressure of the seventh distillation tower 7 is 0.5 MPaG, the temperature at the top of the seventh distillation tower 7 is 95°C, and the temperature at the bottom of the seventh distillation tower 7 is 96°C; the pressure of the deep cooling and filtration unit is 0.5 MPaG, and the temperature of the deep cooling and filtration unit is -160°C.

[0035] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0036] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0037] Example 2 In this embodiment, in step 1, the temperature of the chlorosilane raw material is 30° C., and the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl 4 75%, SiHCl 3 29.5%, and SiH 2 Cl 20.5%.

[0038] 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 83°C; the number of theoretical plates of the second distillation tower 2 is 160, the feed reflux ratio of the second distillation tower 2 is 2, the tower pressure of the second distillation tower 2 is 0.2MpaG, the temperature of the top of the second distillation tower 2 is 41°C, and the temperature of the bottom of the second distillation tower 2 is 70°C; the number of theoretical plates of the third distillation tower 3 is 160, the top reflux ratio of the third distillation tower 3 is 3, and the The tower pressure is 0.1 MPaG, the temperature at the top of the third distillation tower 3 is 53°C, and the temperature at the bottom of the third distillation tower 3 is 55°C; the theoretical plate number of the fourth distillation tower 4 is 160, the feed reflux ratio of the fourth distillation tower 4 is 3, the tower pressure of the fourth distillation tower 4 is 0.1 MPaG, the temperature at the top of the fourth distillation tower 4 is 53°C, and the temperature at the bottom of the fourth distillation tower 4 is 55°C; the theoretical plate number of the fifth distillation tower 5 is 160, the reflux ratio of the fifth distillation tower 5 is 2, the tower pressure of the fifth distillation tower 5 is 0.05 MPaG, the temperature at the top of the fifth distillation tower 5 is 52°C, and the temperature at the bottom of the fifth distillation tower 5 is 55°C.

[0039] The number of theoretical plates of the sixth distillation tower 6 is 160, the reflux ratio of the sixth distillation tower 6 is 5, the tower pressure of the sixth distillation tower 6 is 0.05 MPaG, the temperature at the top of the sixth distillation tower 6 is 44°C, and the temperature at the bottom of the sixth distillation tower 6 is 45°C; the number of theoretical plates of the seventh distillation tower 7 is 160, the reflux ratio of the seventh distillation tower 7 is 6, the tower pressure of the seventh distillation tower 7 is 0.05 MPaG, the temperature at the top of the seventh distillation tower 7 is 44°C, and the temperature at the bottom of the seventh distillation tower 7 is 45°C; the pressure of the deep cooling and filtration unit is 0.1 MPaG, and the temperature of the deep cooling and filtration unit is -150°C.

[0040] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0041] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0042] Example 3 In this embodiment, in step 1, the temperature of the chlorosilane raw material is 55° C., and the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl 4 72%, SiHCl 3 27%, and SiH 2 Cl 21%.

[0043] 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 0.5MpaG, the temperature of the top of the first distillation tower 1 is 82°C, and the temperature of the bottom of the first distillation tower 1 is 115°C; the number of theoretical plates of the second distillation tower 2 is 120, the feed reflux ratio of the second distillation tower 2 is 4, the tower pressure of the second distillation tower 2 is 0.4MpaG, the temperature of the top of the second distillation tower 2 is 62°C, and the temperature of the bottom of the second distillation tower 2 is 83°C; the number of theoretical plates of the third distillation tower 3 is 120, the top reflux ratio of the third distillation tower 3 is 5, and the tower pressure of the third distillation tower 3 is 0.5MpaG. The tower pressure of the third distillation tower 3 is 0.5 MPaG, the temperature at the top of the third distillation tower 3 is 83°C, and the temperature at the bottom of the third distillation tower 3 is 80°C; the number of theoretical plates of the fourth distillation tower 4 is 120, the feed reflux ratio of the fourth distillation tower 4 is 4, the tower pressure of the fourth distillation tower 4 is 0.5 MPaG, the temperature at the top of the fourth distillation tower 4 is 83°C, and the temperature at the bottom of the fourth distillation tower 4 is 80°C; the number of theoretical plates of the fifth distillation tower 5 is 120, the reflux ratio of the fifth distillation tower 5 is 3, the tower pressure of the fifth distillation tower 5 is 0.4 MPaG, the temperature at the top of the fifth distillation tower 5 is 82°C, and the temperature at the bottom of the fifth distillation tower 5 is 80°C.

[0044] The number of theoretical plates of the sixth distillation tower 6 is 120, the reflux ratio of the sixth distillation tower 6 is 7, the tower pressure of the sixth distillation tower 6 is 0.3 MpaG, the temperature at the top of the sixth distillation tower 6 is 70°C, and the temperature at the bottom of the sixth distillation tower 6 is 70°C; the number of theoretical plates of the seventh distillation tower 7 is 120, the reflux ratio of the seventh distillation tower 7 is 10, the tower pressure of the seventh distillation tower 7 is 0.3 MpaG, the temperature at the top of the seventh distillation tower 7 is 70°C, and the temperature at the bottom of the seventh distillation tower 7 is 70°C; the pressure of the deep cooling and filtration unit is 0.3 MpaG, and the temperature of the deep cooling and filtration unit is -155°C.

[0045] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0046] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0047] Example 4 The difference between this embodiment and embodiment 1 is that the chlorosilane raw material produced in the trichlorosilane synthesis process includes SiCl4 10%, SiHCl3 88.5%, and SiH2Cl2 1.5%.

[0048] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0049] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0050] Example 5 The difference between this embodiment and embodiment 2 is that the chlorosilane raw material produced in the trichlorosilane synthesis process includes SiCl4 19.5%, SiHCl3 90%, and SiH2Cl2 0.5%.

[0051] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0052] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0053] Example 6 The difference between this embodiment and embodiment 3 is that the chlorosilane raw material produced in the trichlorosilane synthesis process includes SiCl4 19%, SiHCl3 80%, and SiH2Cl2 1%.

[0054] The overhead stream of the fifth distillation tower 5 is high-purity trichlorosilane with a concentration of >99.9% and a carbon impurity (methylchlorosilane) content of <1 ppm.

[0055] The carbon impurity content of trichlorosilane raw materials is low, and the carbon substitute in the polysilicon produced by trichlorosilane reduction reaches electronic grade level, and can be at least better than the level of electronic special grade products.

[0056] 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 system for removing carbon impurities from chlorosilanes, characterized by: The invention comprises a first distillation tower (1), wherein the first distillation tower (1) is connected to a chlorosilane raw material pipe (101), a first silicon tetrachloride outlet pipe (102) and a first connecting pipe (103), the first connecting pipe (103) is connected to a second distillation tower (2), the second distillation tower (2) is connected to a second connecting pipe (104) and a first external pipe (105), the second connecting pipe (104) is connected to a third distillation tower (3), the third distillation tower (3) is connected to a fourth connecting pipe (106) and a fifth connecting pipe (107), the fourth connecting pipe (106) is connected to a fourth distillation tower (4), the fourth distillation tower (4) is connected to a second external pipe (108) and a sixth connecting pipe (109), the sixth connecting pipe (109) is connected to a fifth distillation tower (5), the fifth distillation tower (5) is connected to a product liquid outlet pipe (110) and a seventh connecting pipe (111). 11), the fifth connecting pipe (107) and the seventh connecting pipe (111) are connected and then flow into the sixth distillation tower (6), the sixth distillation tower (6) is connected to the eighth connecting pipe (112) and the third external pipe (113), the eighth connecting pipe (112) is connected to the seventh distillation tower (7), the seventh distillation tower (7) is connected to the fourth external pipe (114) and the ninth connecting pipe (115), the ninth connecting pipe (115) is connected to the deep cold filter unit (8), the deep cold filter unit (8) is connected to the tenth connecting pipe (116) and the fifth external pipe (117), the tenth connecting pipe (116) is connected to the heat exchanger (9), the heat exchanger (9) is connected to the sixth external pipe (118), the third external pipe (113), the fourth external pipe (114) and the sixth external pipe (118) are all connected to the chlorosilane raw material tank (10).

2. The system for removing carbon impurities from chlorosilanes according to claim 1, characterized in that: The first silicon tetrachloride outlet pipe (102) is connected to the silicon tetrachloride raw material system (11).

3. The system for removing carbon impurities from chlorosilanes according to claim 1, characterized in that: The first outer pipe (105) is connected to the dichlorosilane treatment unit (12).

4. The system for removing carbon impurities from chlorosilanes according to claim 1, characterized in that: The second outer row pipe (108) is connected to the light component processing unit (13).

5. The system for removing carbon impurities from chlorosilanes according to claim 1, characterized in that: The fifth outer pipe (117) is connected to the methylchlorosilane treatment unit (14).

6. The system for removing carbon impurities from chlorosilanes according to claim 1, characterized in that: The deep cold filtration unit (8) adopts a low temperature freezing device.

7. A method for removing carbon impurities from chlorosilane, 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 storage tank, and the top of the first distillation tower (1) is drawn into the second distillation tower (2); Step 2: the overhead liquid of the first distillation tower (1) is subjected to a second distillation separation in the second distillation tower (2); the bottom liquid of the second distillation tower (2) flows into the third distillation tower (3); and the overhead liquid of the second distillation tower (2) flows into the dichlorosilane treatment process; Step 3, the produced liquid from the bottom of the second distillation tower (2) is subjected to a third distillation separation in the third distillation tower (3), the produced liquid from the top of the third distillation tower (3) flows into the fourth distillation tower (4), and the produced liquid from the bottom of the third distillation tower (3) flows into the sixth distillation tower (6); Step 4: the overhead liquid of the third distillation tower (3) is subjected to a fourth distillation separation in the fourth distillation tower (4); the overhead liquid of the fourth distillation tower (4) flows into the light component processing unit (13); the bottom liquid of the fourth distillation tower (4) flows into the fifth distillation tower (5); Step 5: The bottom produced liquid of the fourth distillation tower (4) is subjected to a fifth distillation separation in the fifth distillation tower (5). The top produced stream of the fifth distillation tower (5) is high-purity trichlorosilane. The bottom produced stream of the fifth distillation tower (5) flows into the sixth distillation tower (6).

8. The method for removing carbon impurities in chlorosilane according to claim 7, characterized in that: In step 1, the chlorosilane raw material is a chlorosilane raw material produced by a cold hydrogenation or trichlorosilane synthesis process, the temperature of the chlorosilane raw material is 30-80°C, the chlorosilane raw material produced by the cold hydrogenation synthesis process includes SiCl4 70-75%, SiHCl3 25-30%, and SiH2Cl2 ≤1.5%; the chlorosilane raw material produced by the trichlorosilane synthesis process includes SiCl4 10-20%, SiHCl3 80-90%, and SiH2Cl2 ≤1.5%.

9. The method for removing carbon impurities in chlorosilane 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 (2) is 80-160, the feed reflux ratio of the second distillation tower (2) is 2-5, the tower pressure of the second distillation tower (2) is 0.2-0.5 MPaG, the temperature of the top of the second distillation tower (2) is 41-82°C, and the temperature of the bottom of the second distillation tower (2) is 70-97°C; the number of theoretical plates of the third distillation tower (3) is 80-160, the reflux ratio of the top of the third distillation tower (3) is 3-7, and the tower pressure of the third distillation tower (3) is 0. 1~0.8MpaG, the temperature of the top of the third distillation tower (3) is 53~113℃, and the temperature of the bottom of the third distillation tower (3) is 55~125℃; the number of theoretical plates of the fourth distillation tower (4) is 60~160, the feed reflux ratio of the fourth distillation tower (4) is 3~6, the tower pressure of the fourth distillation tower (4) is 0.1~0.8MpaG, the temperature of the top of the fourth distillation tower (4) is 53~113℃, and the temperature of the bottom of the fourth distillation tower (4) is 55~125℃; the number of theoretical plates of the fifth distillation tower (5) is 60~160, the reflux ratio of the fifth distillation tower (5) is 2~5, the tower pressure of the fifth distillation tower (5) is 0.05~0.8MpaG, the temperature of the top of the fifth distillation tower (5) is 52~112℃, and the temperature of the bottom of the fifth distillation tower (5) is 55~124℃.

10. The method for removing carbon impurities in chlorosilane according to claim 9, characterized in that: The following steps are also included: Step 6: the bottom produced liquid of the third distillation tower (3) and / or the bottom produced liquid of the fifth distillation tower (5) are subjected to a sixth distillation separation in the sixth distillation tower (6); the bottom produced liquid of the sixth distillation tower (6) flows into the seventh distillation tower (7); and the top produced liquid of the sixth distillation tower (6) flows into the chlorosilane raw material tank (10); Step 7, the produced liquid from the bottom of the sixth distillation tower (6) is subjected to a seventh distillation separation in the seventh distillation tower (7), the produced liquid from the bottom of the seventh distillation tower (7) flows into the deep cold filtration unit (8), and the produced liquid from the top of the seventh distillation tower (7) flows into the chlorosilane raw material tank (10); Step 8: The produced liquid from the bottom of the seventh distillation tower (7) is filtered and separated in a deep cold filtration unit (8); the separated impurities flow into the methylchlorosilane treatment process; and the filtered liquid flows into a heat exchanger (9); Step 9: The filtered liquid is heated in the heat exchanger (9) and flows into the chlorosilane raw material tank (10).

11. The method for removing carbon impurities in chlorosilane according to claim 10, characterized in that: The number of theoretical plates of the sixth distillation tower (6) is 80-160, the reflux ratio of the sixth distillation tower (6) is 5-8, the tower pressure of the sixth distillation tower (6) is 0.05-0.5 MPaG, the temperature of the top of the sixth distillation tower (6) is 44-95°C, and the temperature of the bottom of the sixth distillation tower (6) is 45-96°C; the number of theoretical plates of the seventh distillation tower (7) is 80-160, the reflux ratio of the seventh distillation tower (7) is 6-15, the tower pressure of the seventh distillation tower (7) is 0.05-0.5 MPaG, the temperature of the top of the seventh distillation tower (7) is 44-95°C, and the temperature of the bottom of the seventh distillation tower (7) is 45-96°C; the pressure of the deep cooling and filtration unit is 0.1-0.5 MPaG, and the temperature of the deep cooling and filtration unit is -150--160°C.

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