System and method for purifying electronic-grade chlorosilane from polycrystalline silicon tail gas
By combining distillation units for silicon tetrachloride, trichlorosilane, and dichlorosilane, along with a backup distillation unit, the problems of high difficulty and cost in separating chlorosilanes from polycrystalline silicon tail gas have been solved, achieving efficient and low-cost production of high-purity chlorosilanes suitable for high-precision semiconductor devices.
Patent Information
- Application Number
- CN202411089215.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies for separating electronic-grade chlorosilanes from polysilicon tail gas involve high equipment investment, high costs, and low efficiency. They also struggle to achieve purity requirements of 6N or higher and are difficult to separate, impacting the performance and production efficiency of semiconductor devices.
By employing distillation units of silicon tetrachloride, trichlorosilane, and dichlorosilane, combined with a backup distillation unit, and through multi-stage distillation and reflux technology, highly efficient separation of polycrystalline silicon tail gas is achieved to obtain electronic-grade chlorosilane products with a N of 6N or higher.
It achieves polycrystalline silicon tail gas purification with low equipment investment, low cost, and high efficiency, producing high-purity electronic-grade chlorosilanes suitable for 12-inch chips and high-precision semiconductor devices, thus improving production efficiency and economic benefits.
Smart Images
Figure CN121490516A_ABST
Abstract
Description
Technical fields:
[0001] This invention relates to the field of chlorosilane purification technology, and in particular to a system and method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas. Background technology:
[0002] Electronic-grade chlorosilanes are essential materials in the manufacturing of semiconductor devices and integrated circuits. In recent years, with the rapid development of my country's semiconductor industry, the market demand for electronic-grade chlorosilanes has been released. To ensure the healthy development of my country's information industry, it is imperative to independently develop electronic-grade chlorosilanes.
[0003] In semiconductor manufacturing and integrated circuits, electronic-grade chlorosilanes are mainly used for polycrystalline silicon epitaxial growth and chemical vapor deposition of silicon dioxide and silicon nitride. Some electronic-grade chlorosilanes have high silicon content, making silicon deposition more efficient and requiring lower deposition temperatures. Therefore, thicker layers can be deposited at lower temperatures in less time, resulting in better crystal quality. Chlorosilanes can also react with nitrogen oxides to form silicon dioxide and with ammonia to prepare silicon nitride. Both silicon dioxide and silicon nitride can serve as insulating or passivation layers in integrated circuit devices. Therefore, they are highly favored by downstream industries, and the market size continues to grow. The purity of electronic-grade chlorosilanes directly affects the performance of electronic devices; therefore, removing impurities is of paramount importance in the production of electronic-grade polycrystalline silicon.
[0004] Traditional methods often employ the disproportionation of trichlorosilane to prepare chlorosilanes. Producing electronic-grade chlorosilanes via disproportionation requires a one-time investment in disproportionation reactors, catalytic fluidized beds, and other disproportionation reaction equipment, along with continuous and costly catalysts. Furthermore, it generates a large amount of silicon tetrachloride as a byproduct, resulting in high costs and low conversion rates. Subsequent single heavy and light component removal towers are insufficient to elevate the product to ultra-high purity electronic-grade chlorosilanes. Adding adsorption purification equipment in the final stage also increases equipment investment, leads to rapid depreciation, and high costs. The electronic-grade chlorosilanes produced by these methods are mostly at the 4N–6N level, suitable for 8-inch chips, the production of large-scale integrated circuits and special devices, solar cells, optical fibers, and liquid crystal display panels. However, for applications in 12-inch chips, the production of very large-scale and extremely large-scale integrated circuits, and high-precision semiconductor devices, the purity of the chlorosilanes needs to reach 6N or higher. Currently, the Siemens process for producing electronic-grade polysilicon requires a highly clean environment. The raw materials, trichlorosilane and hydrogen, undergo multi-stage adsorption and distillation. Therefore, the resulting tail gas contains hydrogen, hydrogen chloride, and chlorosilanes, with the total content of other impurities at the ppm level. Recovering chlorosilanes from this tail gas has significant application value. However, separating chlorosilanes from the tail gas is currently difficult due to their low boiling point and similarity to impurity compounds, making purification challenging. Furthermore, changes in the composition of the tail gas significantly alter the distillation ratio. Continuing with the existing process would require increased distillation time, reduced production efficiency, and increased energy costs. Alternatively, adding new production lines and new distillation equipment would significantly increase equipment investment. Summary of the Invention:
[0005] The objective of this invention is to provide a system for purifying electronic-grade chlorosilanes from polysilicon tail gas that has a simple connection structure, requires less equipment investment, and improves the economic benefits of enterprises.
[0006] The second objective of this invention is to provide a method for purifying electronic-grade chlorosilanes from polysilicon tail gas that is simple in process and improves production efficiency.
[0007] This invention is implemented by the following technical solution: The objective of this patent is to provide a system for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas, which includes a chlorosilane feed tank, a preheater, a silicon tetrachloride distillation device, a trichlorosilane distillation device, and a dichlorosilane distillation device; the liquid outlet of the chlorosilane feed tank is connected to the cold medium inlet of the preheater, the cold medium outlet of the preheater is connected to the middle section inlet of the distillation column of the silicon tetrachloride distillation device, and the bottom outlet of the distillation column of the silicon tetrachloride distillation device is connected to the liquid inlet of the silicon tetrachloride product tank;
[0008] The outlet of the reflux tank of the silicon tetrachloride distillation apparatus is connected to the reflux port of the distillation column of the silicon tetrachloride distillation apparatus and the inlet of the middle section of the distillation column of the trichlorosilane distillation apparatus, respectively. The outlet of the bottom of the distillation column of the trichlorosilane distillation apparatus is connected to the inlet of the trichlorosilane product tank.
[0009] The outlet of the reflux tank of the trichlorosilane distillation apparatus is connected to the reflux port of the distillation column of the trichlorosilane distillation apparatus and the inlet of the middle section of the distillation column of the dichlorosilane distillation apparatus, respectively. The outlet of the reflux tank of the dichlorosilane distillation apparatus is connected to the reflux port of the distillation column of the dichlorosilane distillation apparatus and the inlet of the dichlorosilane product tank, respectively.
[0010] Furthermore, it also includes a backup distillation unit. The outlet of the reflux tank of the silicon tetrachloride distillation unit is connected to the reflux port of the distillation column of the silicon tetrachloride distillation unit and the inlet of the middle section of the distillation column of the backup distillation unit, respectively. The outlet of the distillation column of the backup distillation unit is connected to the inlet of the silicon tetrachloride product tank and the inlet of the trichlorosilane product tank, respectively. The outlet of the reflux tank of the backup distillation unit is connected to the reflux port of the distillation column of the backup distillation unit and the inlet of the middle section of the distillation column of the trichlorosilane distillation unit, respectively.
[0011] Furthermore, the silicon tetrachloride distillation apparatus, the trichlorosilane distillation apparatus, the dichlorosilane distillation apparatus, and the standby distillation apparatus have the same structure, all including a distillation column, a condenser, a reflux tank, and a reboiler; the top outlet of the distillation column is connected to the gas inlet of the condenser, and the liquid outlet of the condenser is connected to the liquid inlet of the reflux tank; the bottom outlet of the distillation column is connected to the cold medium inlet of the reboiler, and the cold medium outlet of the reboiler is connected to the bottom inlet of the distillation column.
[0012] Furthermore, the top outlet of the distillation column of the silicon tetrachloride distillation apparatus is connected to the heat medium inlet of the reboiler of the trichlorosilane distillation apparatus and the heat medium inlet of the reboiler of the dichlorosilane distillation apparatus, respectively. The heat medium outlet of the reboiler of the trichlorosilane distillation apparatus and the heat medium outlet of the reboiler of the dichlorosilane distillation apparatus are both connected to the gas inlet of the condenser of the silicon tetrachloride distillation apparatus.
[0013] The second objective of this patent is to provide a method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas, which includes the following steps:
[0014] (1) Silicon tetrachloride distillation: The chlorosilane raw material in the chlorosilane raw material tank is pumped to the distillation column of the silicon tetrachloride distillation unit for silicon tetrachloride distillation. The silicon tetrachloride product taken from the bottom of the column is sent to the silicon tetrachloride product tank. The chlorosilane mixed gas taken from the top of the column is cooled and condensed by the condenser to obtain the chlorosilane mixed liquid, part of which is returned to the distillation column.
[0015] (2) Trichlorosilane distillation: The remaining part of the chlorosilane mixture in step (1) is pumped to the distillation column of the trichlorosilane distillation unit for trichlorosilane distillation. The trichlorosilane product taken from the bottom of the column is sent to the trichlorosilane product tank. The mixed gas taken from the top of the column is cooled and condensed by the condenser to obtain the mixed liquid, and a part of it is returned to the distillation column.
[0016] (3) Dichlorosilane distillation: The remaining mixture from step (2) is pumped to the distillation column of the dichlorosilane distillation unit for dichlorosilane distillation. The dichlorosilane gas taken from the top of the column is cooled and condensed by the condenser to obtain dichlorosilane liquid. Part of it is returned to the distillation column, and part of it is sent to the dichlorosilane product tank as dichlorosilane product. The high-boiling-point substance taken from the bottom of the column is sent to the subsequent process.
[0017] Furthermore, in step (1), the reflux ratio is 9.0 to 11.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 105 to 109°C, and the bottom temperature is 114 to 118°C.
[0018] The reflux ratio in step (2) is 60.0 to 80.0:1, the operating pressure is 560 to 580 kPa, the top temperature is 84 to 88°C, and the bottom temperature is 98 to 102°C.
[0019] The reflux ratio in step (3) is 18.0 to 25.0:1, the operating pressure is 660 to 680 kPa, the top temperature is 64 to 68°C, and the bottom temperature is 71 to 77°C.
[0020] Furthermore, between steps (1) and (2) is the following: standby distillation: a portion of the remaining chlorosilane mixture from step (1) is pumped to the distillation column of the standby distillation unit for distillation. The silicon tetrachloride product collected from the bottom of the column is sent to the silicon tetrachloride product tank or the trichlorosilane product is sent to the trichlorosilane product tank. The chlorosilane mixture collected from the top of the column is cooled and condensed by a condenser to obtain a chlorosilane mixture, a portion of which is returned to the distillation column.
[0021] Furthermore, when silicon tetrachloride product is collected from the bottom of the column, the reflux ratio is 6.0–8.0:1, the operating pressure is 460–480 kPa, the top temperature is 102–106 °C, and the bottom temperature is 95–99 °C.
[0022] Furthermore, when the trichlorosilane product is collected from the bottom of the tower, the reflux ratio in step (1) is 9.0 to 11.0:1; the operating pressure is 525 to 545 kPa; the top temperature of the tower is 92 to 96°C; and the bottom temperature of the tower is 107 to 111°C.
[0023] The reflux ratio for standby distillation is 6.0–11.0:1, the operating pressure is 460–545 kPa, the top temperature is 92–99 °C, and the bottom temperature is 95–111 °C.
[0024] Furthermore, the chlorosilane mixture gas extracted from the top of the column in step (1) is used as a heat source and sent to the reboiler of the trichlorosilane distillation unit in step (2) and the reboiler of the dichlorosilane distillation unit in step (3) to heat the materials in the corresponding distillation columns. After heat exchange, the mixture is returned to the condenser of the silicon tetrachloride distillation unit for condensation.
[0025] Advantages of this invention:
[0026] 1. The system disclosed in this invention has a simple connection structure. By setting up a silicon tetrachloride distillation device, a trichlorosilane distillation device, and a dichlorosilane distillation device, it can fully separate the tail gas generated in the reduction process of electronic-grade polycrystalline silicon to obtain various electronic-grade chlorosilane products such as electronic-grade silicon tetrachloride, electronic-grade trichlorosilane, and electronic-grade dichlorosilane with a purity of 6N or higher.
[0027] 2. The system disclosed in this invention, by setting up a backup distillation unit, can be used to separate chlorosilane raw materials with different contents. It requires less equipment investment, reduces investment costs, and has high efficiency, thereby improving the economic benefits of enterprises.
[0028] 3. The method disclosed in this invention has a simple process. The appropriate operation process is selected according to the different contents of chlorosilane raw materials. No catalyst or other additives are required, which reduces the production cost. It not only turns the chlorosilane that originally required special treatment into a high-value electronic specialty gas, but also separates various high-purity chlorosilane products that can be used for reduction to produce electronic-grade polysilicon, thereby improving production efficiency. Attached image description:
[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention.
[0031] 1. Silane feedstock tank, 2. Preheater, 3. Silicon tetrachloride distillation unit, 4. Trichlorosilane distillation unit, 5. Dichlorosilane distillation unit, 6. Standby distillation unit, 7. Silicon tetrachloride product tank, 8. Trichlorosilane product tank, 9. Dichlorosilane product tank, 10. Distillation column, 11. Condenser, 12. Reflux tank, 13. Reboiler. Detailed implementation method:
[0032] Example 1: As Figure 1 As shown, a system for purifying electronic-grade chlorosilanes from polysilicon tail gas includes a chlorosilane feed tank 1, a preheater 2, a silicon tetrachloride distillation unit 3, a trichlorosilane distillation unit 4, a dichlorosilane distillation unit 5, and a standby distillation unit 6. The outlet of the chlorosilane feed tank 1 is connected to the cold medium inlet of the preheater 2, the cold medium outlet of the preheater 2 is connected to the middle section inlet of the distillation column 10 of the silicon tetrachloride distillation unit 3, and the bottom outlet of the distillation column 10 of the silicon tetrachloride distillation unit 3 is connected to the inlet of the silicon tetrachloride product tank 7. The outlet of the reflux tank 12 of the silicon tetrachloride distillation unit 3 is connected to the silicon tetrachloride product tank 7. The reflux port of the distillation column 10 of the silicon distillation unit 3 is connected to the middle section inlet of the distillation column 10 of the trichlorosilane distillation unit 4, and the bottom outlet of the distillation column 10 of the trichlorosilane distillation unit 4 is connected to the inlet of the trichlorosilane product tank 8; the outlet of the reflux tank 12 of the trichlorosilane distillation unit 4 is connected to the reflux port of the distillation column 10 of the trichlorosilane distillation unit 4 and the middle section inlet of the distillation column 10 of the dichlorosilane distillation unit 5, respectively, and the outlet of the reflux tank 12 of the dichlorosilane distillation unit 5 is connected to the reflux port of the distillation column 10 of the dichlorosilane distillation unit 5 and the inlet of the dichlorosilane product tank 9, respectively.
[0033] The outlet of the reflux tank 12 of the silicon tetrachloride distillation unit 3 is connected to the reflux port of the distillation column 10 of the silicon tetrachloride distillation unit 3 and the middle section inlet of the distillation column 10 of the standby distillation unit 6, respectively. The bottom outlet of the distillation column 10 of the standby distillation unit 6 is connected to the inlet of the silicon tetrachloride product tank 7 and the inlet of the trichlorosilane product tank 8, respectively. The outlet of the reflux tank 12 of the standby distillation unit 6 is connected to the reflux port of the distillation column 10 of the standby distillation unit 6 and the middle section inlet of the distillation column 10 of the trichlorosilane distillation unit 4, respectively. The standby distillation unit 6 can be used to separate chlorosilane raw materials with different contents. It requires less equipment investment, reduces investment costs, has high utilization efficiency, and improves the economic benefits of enterprises.
[0034] The silicon tetrachloride distillation unit 3, the trichlorosilane distillation unit 4, the dichlorosilane distillation unit 5, and the standby distillation unit 6 have the same structure, all including a distillation column 10, a condenser 11, a reflux tank 12, and a reboiler 13; the top outlet of the distillation column 10 is connected to the gas inlet of the condenser 11, and the liquid outlet of the condenser 11 is connected to the liquid inlet of the reflux tank 12; the bottom outlet of the distillation column 10 is connected to the cold medium inlet of the reboiler 13, and the cold medium outlet of the reboiler 13 is connected to the bottom inlet of the distillation column 10.
[0035] The top outlet of the distillation column 10 of the silicon tetrachloride distillation unit 3 is connected to the heat medium inlet of the reboiler 13 of the trichlorosilane distillation unit 4 and the heat medium inlet of the reboiler 13 of the dichlorosilane distillation unit 5, respectively. The heat medium outlet of the reboiler 13 of the trichlorosilane distillation unit 4 and the heat medium outlet of the reboiler 13 of the dichlorosilane distillation unit 5 are both connected to the gas inlet of the condenser 11 of the silicon tetrachloride distillation unit 3.
[0036] The system disclosed in this invention has a simple connection structure and can fully separate the tail gas generated in the reduction process of electronic-grade polycrystalline silicon to obtain various electronic-grade chlorosilane products such as electronic-grade silicon tetrachloride, electronic-grade trichlorosilane, and electronic-grade dichlorosilane with a purity of 6N or higher.
[0037] Example 2: A method for purifying electronic-grade chlorosilanes from polysilicon tail gas, comprising the following steps: when the concentration of silicon tetrachloride in the raw material in chlorosilane raw material tank 1 is 36-42%, the following operations are performed:
[0038] (1) Silicon tetrachloride distillation: The chlorosilane raw material in the chlorosilane raw material tank 1 is pumped to the distillation column 10 of the silicon tetrachloride distillation unit 3 for silicon tetrachloride distillation. The silicon tetrachloride product with a purity of 99.9999% is collected from the bottom of the column and sent to the silicon tetrachloride product tank 7. The chlorosilane mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a chlorosilane mixed liquid, part of which is refluxed back to the distillation column 10. The reflux ratio is 9.0 to 11.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 105 to 109 °C, and the bottom temperature is 114 to 118 °C.
[0039] (2) Trichlorosilane distillation: The remaining part of the chlorosilane mixture in step (1) is pumped to the distillation column 10 of the trichlorosilane distillation device 4 for trichlorosilane distillation. 99.9999% trichlorosilane product is collected from the bottom of the column and sent to the trichlorosilane product tank 8. The mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a mixed liquid, part of which is refluxed back to the distillation column 10. The reflux ratio is 60.0 to 80.0:1, the operating pressure is 560 to 580 kPa, the top temperature is 84 to 88°C, and the bottom temperature is 98 to 102°C.
[0040] (3) Dichlorosilane distillation: The remaining mixture from step (2) is pumped to the distillation column 10 of the dichlorosilane distillation device 5 for dichlorosilane distillation. The dichlorosilane gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain 99.9999% dichlorosilane liquid. Part of it is returned to the distillation column 10, and part of it is sent to the dichlorosilane product tank 9 as dichlorosilane product. The high-boiling-point substance collected from the bottom of the column is sent to the subsequent process. The reflux ratio is 18.0 to 25.0:1, the operating pressure is 660 to 680 kPa, the top temperature is 64 to 68°C, and the bottom temperature is 71 to 77°C.
[0041] In step (1), the chlorosilane mixture gas extracted from the top of the column is used as a heat source and sent to the reboiler 13 of the trichlorosilane distillation unit 4 in step (2) and the reboiler 13 of the dichlorosilane distillation unit 5 in step (3) to heat the material in the corresponding distillation column 10. After heat exchange, it is returned to the condenser 11 of the silicon tetrachloride distillation unit 3 for condensation. This achieves full utilization of heat, reduces the loss of heating steam, and lowers costs.
[0042] Example 3: A method for purifying electronic-grade chlorosilanes from polysilicon tail gas, comprising the following steps: when the concentration of silicon tetrachloride in the raw material in chlorosilane raw material tank 1 is 42-45%, the following operations are performed:
[0043] (1) Silicon tetrachloride distillation: The chlorosilane raw material in the chlorosilane raw material tank 1 is pumped to the distillation column 10 of the silicon tetrachloride distillation unit 3 for silicon tetrachloride distillation. The silicon tetrachloride product with a purity of 99.9999% is collected from the bottom of the column and sent to the silicon tetrachloride product tank 7. The chlorosilane mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a chlorosilane mixed liquid, part of which is refluxed back to the distillation column 10. The reflux ratio is 9.0 to 11.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 105 to 109 °C, and the bottom temperature is 114 to 118 °C.
[0044] (2) Backup distillation: The remaining part of the chlorosilane mixture in step (1) is pumped to the distillation column 10 of the backup distillation unit 6 for distillation. 99.9999% silicon tetrachloride product is taken from the bottom of the column and sent to the silicon tetrachloride product tank 7. The chlorosilane mixture gas taken from the top of the column is cooled and condensed by the condenser 11 to obtain the chlorosilane mixture. A part of it is refluxed back to the distillation column 10, where the reflux ratio is 6.0 to 8.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 102 to 106 °C, and the bottom temperature is 95 to 99 °C.
[0045] (3) Trichlorosilane distillation: The remaining part of the chlorosilane mixture in step (2) is pumped to the distillation column 10 of the trichlorosilane distillation device 4 for trichlorosilane distillation. The trichlorosilane product with 99.9999% purity is collected from the bottom of the column and sent to the trichlorosilane product tank 8. The mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a mixed liquid, part of which is returned to the distillation column 10. The reflux ratio is 60.0 to 80.0:1, the operating pressure is 560 to 580 kPa, the top temperature is 84 to 88°C, and the bottom temperature is 98 to 102°C.
[0046] (4) Dichlorosilane distillation: The remaining mixture from step (3) is pumped to the distillation column 10 of the dichlorosilane distillation device 5 for dichlorosilane distillation. The dichlorosilane gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain 99.9999% dichlorosilane liquid. Part of it is returned to the distillation column 10, and part of it is sent to the dichlorosilane product tank 9 as dichlorosilane product. The high-boiling-point substance collected from the bottom of the column is sent to the subsequent process. The reflux ratio is 18.0 to 25.0:1, the operating pressure is 660 to 680 kPa, the top temperature is 64 to 68°C, and the bottom temperature is 71 to 77°C.
[0047] In step (1), the chlorosilane mixture gas extracted from the top of the column is used as a heat source and sent to the reboiler 13 of the trichlorosilane distillation unit 4 in step (3) and the reboiler 13 of the dichlorosilane distillation unit 5 in step (4) to heat the material in the corresponding distillation column 10. After heat exchange, it is returned to the condenser 11 of the silicon tetrachloride distillation unit 3 for condensation. This achieves full utilization of heat, reduces the loss of heating steam, and lowers costs.
[0048] Example 4: A method for purifying electronic-grade chlorosilanes from polysilicon tail gas, comprising the following steps: when the concentration of trichlorosilane in the raw material in chlorosilane raw material tank 1 is 30-36%, the following operation is performed:
[0049] (1) Silicon tetrachloride distillation: The chlorosilane raw material in the chlorosilane raw material tank 1 is pumped to the distillation column 10 of the silicon tetrachloride distillation unit 3 for silicon tetrachloride distillation. The silicon tetrachloride product with a purity of 99.9999% is collected from the bottom of the column and sent to the silicon tetrachloride product tank 7. The chlorosilane mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a chlorosilane mixed liquid, part of which is refluxed back to the distillation column 10. The reflux ratio is 9.0 to 11.0:1. The operating pressure is 525 to 545 kPa, the top temperature is 92 to 96°C, and the bottom temperature is 107 to 111°C.
[0050] (2) Backup distillation: The remaining part of the chlorosilane mixture in step (1) is pumped to the distillation column 10 of the backup distillation unit 6 for distillation. The 99.9999% trichlorosilane product is collected from the bottom of the column and sent to the trichlorosilane product tank 8. The chlorosilane mixture gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain the chlorosilane mixture. A part of it is refluxed back to the distillation column 10, where the reflux ratio is 6.0 to 11.0:1, the operating pressure is 460 to 545 kPa, the top temperature is 92 to 99°C, and the bottom temperature is 95 to 111°C.
[0051] (3) Trichlorosilane distillation: The remaining part of the chlorosilane mixture in step (2) is pumped to the distillation column 10 of the trichlorosilane distillation device 4 for trichlorosilane distillation. 99.9999% trichlorosilane product is collected from the bottom of the column and sent to the trichlorosilane product tank 8. The mixed gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain a mixed liquid, part of which is refluxed back to the distillation column 10. The reflux ratio is 60.0 to 80.0:1, the operating pressure is 560 to 580 kPa, the top temperature is 84 to 88°C, and the bottom temperature is 98 to 102°C.
[0052] (4) Dichlorosilane distillation: The remaining mixture from step (3) is pumped to the distillation column 10 of the dichlorosilane distillation device 5 for dichlorosilane distillation. The dichlorosilane gas collected from the top of the column is cooled and condensed by the condenser 11 to obtain 99.9999% dichlorosilane liquid. Part of it is returned to the distillation column 10, and part of it is sent to the dichlorosilane product tank 9 as dichlorosilane product. The high-boiling-point substance collected from the bottom of the column is sent to the subsequent process. The reflux ratio is 18.0 to 25.0:1, the operating pressure is 660 to 680 kPa, the top temperature is 64 to 68°C, and the bottom temperature is 71 to 77°C.
[0053] In step (1), the chlorosilane mixture gas extracted from the top of the column is used as a heat source and sent to the reboiler 13 of the trichlorosilane distillation unit 4 in step (3) and the reboiler 13 of the dichlorosilane distillation unit 5 in step (4) to heat the material in the corresponding distillation column 10. After heat exchange, it is returned to the condenser 11 of the silicon tetrachloride distillation unit 3 for condensation. This achieves full utilization of heat, reduces the loss of heating steam, and lowers costs.
[0054] The method disclosed in this invention has a simple process. Depending on the content of the chlorosilane raw materials, the corresponding operation process is selected. No catalyst or other additives are required, which reduces the production cost. It not only transforms the chlorosilanes that originally required special treatment into high-value electronic specialty gases, but also separates various high-purity chlorosilane products that can be used for the reduction and production of electronic-grade polysilicon, thereby improving production efficiency.
[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A system for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas, characterized in that, It includes a chlorosilane feedstock tank, a preheater, a silicon tetrachloride distillation unit, a trichlorosilane distillation unit, and a dichlorosilane distillation unit; the liquid outlet of the chlorosilane feedstock tank is connected to the cold medium inlet of the preheater, the cold medium outlet of the preheater is connected to the middle section inlet of the distillation column of the silicon tetrachloride distillation unit, and the bottom outlet of the distillation column of the silicon tetrachloride distillation unit is connected to the liquid inlet of the silicon tetrachloride product tank; The outlet of the reflux tank of the silicon tetrachloride distillation apparatus is connected to the reflux port of the distillation column of the silicon tetrachloride distillation apparatus and the inlet of the middle section of the distillation column of the trichlorosilane distillation apparatus, respectively. The outlet of the bottom of the distillation column of the trichlorosilane distillation apparatus is connected to the inlet of the trichlorosilane product tank. The outlet of the reflux tank of the trichlorosilane distillation apparatus is connected to the reflux port of the distillation column of the trichlorosilane distillation apparatus and the inlet of the middle section of the distillation column of the dichlorosilane distillation apparatus, respectively. The outlet of the reflux tank of the dichlorosilane distillation apparatus is connected to the reflux port of the distillation column of the dichlorosilane distillation apparatus and the inlet of the dichlorosilane product tank, respectively.
2. The system for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 1, characterized in that, It also includes a backup distillation unit, wherein the outlet of the reflux tank of the silicon tetrachloride distillation unit is connected to the reflux port of the distillation column of the silicon tetrachloride distillation unit and the inlet of the middle section of the distillation column of the backup distillation unit, respectively; the outlet of the distillation column of the backup distillation unit is connected to the inlet of the silicon tetrachloride product tank and the inlet of the trichlorosilane product tank, respectively; and the outlet of the reflux tank of the backup distillation unit is connected to the reflux port of the distillation column of the backup distillation unit and the inlet of the middle section of the distillation column of the trichlorosilane distillation unit, respectively.
3. The system for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 2, characterized in that, The silicon tetrachloride distillation apparatus, the trichlorosilane distillation apparatus, the dichlorosilane distillation apparatus, and the standby distillation apparatus have the same structure, all including a distillation column, a condenser, a reflux tank, and a reboiler; the top outlet of the distillation column is connected to the gas inlet of the condenser, and the liquid outlet of the condenser is connected to the liquid inlet of the reflux tank; the bottom outlet of the distillation column is connected to the cold medium inlet of the reboiler, and the cold medium outlet of the reboiler is connected to the bottom inlet of the distillation column.
4. The system for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 3, characterized in that, The top outlet of the distillation column of the silicon tetrachloride distillation apparatus is connected to the heat medium inlet of the reboiler of the trichlorosilane distillation apparatus and the heat medium inlet of the reboiler of the dichlorosilane distillation apparatus, respectively. The heat medium outlet of the reboiler of the trichlorosilane distillation apparatus and the heat medium outlet of the reboiler of the dichlorosilane distillation apparatus are both connected to the gas inlet of the condenser of the silicon tetrachloride distillation apparatus.
5. A method for purifying electronic-grade chlorosilanes using the system described in any one of claims 1-4, characterized in that, It includes the following steps: (1) Silicon tetrachloride distillation: The chlorosilane raw material in the chlorosilane raw material tank is pumped to the distillation column of the silicon tetrachloride distillation unit for silicon tetrachloride distillation. The silicon tetrachloride product taken from the bottom of the column is sent to the silicon tetrachloride product tank. The chlorosilane mixed gas taken from the top of the column is cooled and condensed by the condenser to obtain the chlorosilane mixed liquid, part of which is returned to the distillation column. (2) Trichlorosilane distillation: The remaining part of the chlorosilane mixture in step (1) is pumped to the distillation column of the trichlorosilane distillation unit for trichlorosilane distillation. The trichlorosilane product taken from the bottom of the column is sent to the trichlorosilane product tank. The mixed gas taken from the top of the column is cooled and condensed by the condenser to obtain the mixed liquid, and a part of it is returned to the distillation column. (3) Dichlorosilane distillation: The remaining mixture from step (2) is pumped to the distillation column of the dichlorosilane distillation unit for dichlorosilane distillation. The dichlorosilane gas taken from the top of the column is cooled and condensed by the condenser to obtain dichlorosilane liquid. Part of it is returned to the distillation column, and part of it is sent to the dichlorosilane product tank as dichlorosilane product. The high-boiling-point substance taken from the bottom of the column is sent to the subsequent process.
6. The method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 5, characterized in that, The reflux ratio in step (1) is 9.0 to 11.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 105 to 109°C, and the bottom temperature is 114 to 118°C. The reflux ratio in step (2) is 60.0 to 80.0:1, the operating pressure is 560 to 580 kPa, the top temperature is 84 to 88°C, and the bottom temperature is 98 to 102°C. The reflux ratio in step (3) is 18.0 to 25.0:1, the operating pressure is 660 to 680 kPa, the top temperature is 64 to 68°C, and the bottom temperature is 71 to 77°C.
7. The method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 5, characterized in that, Between steps (1) and (2), the following is also included: standby distillation: a portion of the remaining chlorosilane mixture from step (1) is pumped to the distillation column of the standby distillation unit for distillation. The silicon tetrachloride product taken from the bottom of the column is sent to the silicon tetrachloride product tank or the trichlorosilane product is sent to the trichlorosilane product tank. The chlorosilane mixture gas taken from the top of the column is cooled and condensed by the condenser to obtain the chlorosilane mixture, a portion of which is returned to the distillation column.
8. A method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 7, characterized in that, When silicon tetrachloride product is collected from the bottom of the column, the reflux ratio is 6.0 to 8.0:1, the operating pressure is 460 to 480 kPa, the top temperature is 102 to 106°C, and the bottom temperature is 95 to 99°C.
9. A method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 7, characterized in that, When trichlorosilane is extracted from the bottom of the tower... The reflux ratio in step (1) is 9.0 to 11.0:1; the operating pressure is 525 to 545 kPa; the top temperature is 92 to 96°C; and the bottom temperature is 107 to 111°C. The reflux ratio for standby distillation is 6.0–11.0:1, the operating pressure is 460–545 kPa, the top temperature is 92–99°C, and the bottom temperature is 95–111°C.
10. A method for purifying electronic-grade chlorosilanes from polycrystalline silicon tail gas according to claim 5, characterized in that, The chlorosilane mixture gas extracted from the top of the column in step (1) is used as a heat source and sent to the reboiler of the trichlorosilane distillation unit in step (2) and the reboiler of the dichlorosilane distillation unit in step (3) to heat the material in the corresponding distillation column. After heat exchange, it is returned to the condenser of the silicon tetrachloride distillation unit for condensation.