Composite adsorption system for removing impurities from trichlorosilane by rectification

Abstract

The utility model discloses a kind of for trichlorosilane rectification impurity removal composite adsorption system, system includes the crude distillation first tower, high-low boiling concentration tower, product trichlorosilane rectification tower, protective bed, activated carbon adsorption tank, catalytic reaction rectification tower and resin adsorption tank connected by pipeline.It is in at its core by protective bed and activated carbon adsorption tank series to carry out raw material pretreatment;Utilize the lateral line of crude distillation first tower to accurately extract difficult separation methyl dichlorosilane, and after being concentrated by high-low boiling concentration tower, it is sent into catalytic reaction rectification tower and is converted and separated;Energy is saved by using differential pressure thermal coupling connection between each rectification tower;Final product is refined by resin adsorption tank in depth.The utility model is integrated by the cooperation of each unit, realizes the fractional directional removal of impurity, and has the advantages of high product purity, high security and low operating cost.

Description

Technical Field

[0001] This utility model relates to the field of purification technology for raw materials in polycrystalline silicon production, specifically a composite adsorption system for distillation and impurity removal of trichlorosilane. Background Technology

[0002] High-purity trichlorosilane is a core raw material for the preparation of semiconductor-grade polycrystalline silicon, and its purity directly determines the quality of the final polycrystalline silicon product. Impurities in trichlorosilane are complex in form, especially metal compounds such as boron and phosphorus, as well as carbon-based impurities such as methyldichlorosilane with boiling points close to these, which are difficult to remove effectively using traditional multi-stage distillation processes.

[0003] Currently, resin adsorption is commonly used in the industry to remove impurities such as boron and phosphorus. However, resin adsorbents are expensive, and there is a safety risk of disproportionation reactions during the adsorption process, usually requiring strict control of raw material composition to reduce this risk. Furthermore, for impurities like methyldichlorosilane, which have boiling points close to trichlorosilane and extremely low relative volatility, simple distillation separation is energy-intensive and difficult to completely remove, leading to accumulation within the system and affecting product purity. Therefore, existing technologies suffer from a difficulty in balancing impurity removal efficiency, operating costs, and system safety, necessitating an integrated, efficient, and safe purification solution. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a composite adsorption system for distillation and impurity removal of trichlorosilane. By integrating adsorption, reaction and distillation operations, it realizes the graded and directional removal of impurities, ensuring product purity while having high safety and low operating costs.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a composite adsorption system for distillation and impurity removal of trichlorosilane, comprising a crude distillation column, a high and low boiling concentration column, a product trichlorosilane distillation column, a protective bed, an activated carbon adsorption tank, a catalytic reaction distillation column, and a resin adsorption tank. The outlet of the protective bed is connected to the inlet of the activated carbon adsorption tank, and the outlet of the activated carbon adsorption tank is connected to the feed port of the primary distillation column on the primary distillation column body through a pipeline. The crude distillation first-stage column side outlet on the crude distillation first-stage column body is connected to the high and low boiling point concentration column inlet on the high and low boiling point concentration column body via a pipeline. The high and low boiling point concentration tower side outlet on the high and low boiling point concentration tower body is connected to the silicon tetrachloride replenishment pipe through a pipeline and then connected to the catalytic reaction distillation tower feed inlet on the catalytic reaction distillation tower body. The vapor phase outlet at the top of the catalytic reaction distillation column is connected to the product trichlorosilane distillation column feed inlet on the product trichlorosilane distillation column body via a pipeline. The vapor phase outlet at the top of the trichlorosilane distillation column is connected to the inlet of the resin adsorption tank via a pipeline. The outlet pipe of the resin adsorption tank is connected to the high-purity trichlorosilane product tank.

[0006] In a preferred embodiment, the middle section of the catalytic reactive distillation column is filled with a catalyst bed.

[0007] In a preferred embodiment, the feed inlet of the catalytic reactive distillation column is located above the catalyst bed.

[0008] In a preferred embodiment, the bottom outlet of the catalytic reactive distillation column is connected to the silicon tetrachloride recovery system via a pipeline.

[0009] In a preferred embodiment, the vapor phase outlet at the top of the primary crude distillation column is connected via a pipeline to the heat medium inlet of the reboiler in the high-low boiling concentration column.

[0010] In a preferred embodiment, the vapor phase outlet at the top of the high-low boiling concentration tower is connected via a pipeline to the heat medium inlet of the reboiler of the product trichlorosilane distillation tower.

[0011] In a preferred embodiment, there are two resin adsorption tanks, which are connected in parallel to the pipeline at the vapor phase outlet of the product trichlorosilane distillation column via a pipeline. Switching valves are provided at the inlet and outlet ends of the two parallel pipelines containing the two resin adsorption tanks.

[0012] In a preferred embodiment, the bottom outlet of the crude distillation primary column is connected via a pipeline to the feed inlet of the product trichlorosilane distillation column.

[0013] In a preferred embodiment, the bottom outlet of the high- and low-boiling-point concentration tower is connected to the feed inlet of a deweighting tower via a pipeline.

[0014] In a preferred embodiment, the adsorbent packed in the protective bed is a molecular sieve or modified alumina; The adsorbent filled in the activated carbon adsorption tank is coal-based granular activated carbon.

[0015] The composite adsorption system for removing impurities from trichlorosilane distillation provided by this utility model has the following beneficial effects by adopting the above structure: (1) The material rich in methyldichlorosilane is precisely extracted through the side stream outlet of the crude distillation first-stage column, and is converted into easily separable substances by using a catalytic reaction distillation column. This solves the industry problem of difficult separation and easy accumulation of impurities with near boiling points from the perspective of process principle, so that the purity of the final trichlorosilane product can stably reach the semiconductor electronic grade standard. (2) The activated carbon adsorption tank is used to undertake the initial adsorption of most of the impurities in the raw materials, while the high-cost resin adsorption tank is placed at the end of the process with small processing volume and high impurity concentration for deep purification. On the one hand, the high safety of activated carbon reduces the risk of the main adsorption process, and on the other hand, it greatly reduces the amount of resin used and the frequency of replacement. Thus, while improving the inherent safety of the system, it significantly reduces the overall cost of adsorbent use. (3) Differential pressure thermal coupling connection is adopted between the crude distillation first-stage column, the high and low boiling concentration column and the product trichlorosilane distillation column. That is, the latent heat of the steam at the top of the preceding column is used as the heat source of the reboiler of the subsequent column, which maximizes the recovery and utilization of the energy inside the system, and the overall steam consumption is significantly reduced compared with the traditional sequential distillation process. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0017] In the diagram: 1. Crude distillation primary column; 2. High and low boiling point concentration column; 3. Product trichlorosilane distillation column; 4. Protective bed; 5. Activated carbon adsorption tank; 6. Catalytic reactive distillation column; 7. Crude distillation primary column feed inlet; 8. Crude distillation primary column side stream outlet; 9. High and low boiling point concentration column feed inlet; 10. High and low boiling point concentration column side stream outlet; 11. Silicon tetrachloride makeup pipe; 12. Catalytic reactive distillation column feed inlet; 13. Catalyst bed; 14. Catalytic reactive distillation column top vapor phase outlet; 15. Product trichlorosilane distillation column feed inlet; 16. Product trichlorosilane distillation column top vapor phase outlet; 17. Resin adsorption tank; 18. High-purity trichlorosilane product tank; 19. Catalytic reactive distillation column bottom outlet; 20. Crude distillation primary column top vapor phase outlet; 21. High and low boiling point concentration column reboiler heat medium inlet; 22. High and low boiling point concentration column top vapor phase outlet; 23. Product trichlorosilane distillation column reboiler heat medium inlet. Detailed Implementation

[0018] like Figure 1 As shown, the present invention provides a composite adsorption system for removing impurities by distillation of trichlorosilane. The core components include a crude distillation column 1, a high- and low-boiling concentration column 2, a product trichlorosilane distillation column 3, a protective bed 4, an activated carbon adsorption tank 5, a catalytic reaction distillation column 6, and a resin adsorption tank 17.

[0019] The outlet of the protective bed 4 is connected to the inlet of the activated carbon adsorption tank 5, and the outlet of the activated carbon adsorption tank 5 is connected to the feed port 7 of the primary distillation column 1 on the cylinder of the primary distillation column 1 through a pipeline. The crude distillation first-stage column 1 side outlet 8 is connected to the high and low boiling concentration column 2 feed inlet 9 via a pipeline. The high and low boiling concentration tower side line outlet 10 on the high and low boiling concentration tower 2 is connected to the silicon tetrachloride replenishment pipe 11 through a pipeline and then connected to the catalytic reaction distillation tower inlet 12 on the catalytic reaction distillation tower 6. The vapor phase outlet 14 at the top of the catalytic reaction distillation column 6 is connected to the product trichlorosilane distillation column inlet 15 on the shell of the product trichlorosilane distillation column 3 via a pipeline. The product trichlorosilane distillation column 3 has its top vapor phase outlet 16 connected to the inlet of the resin adsorption tank 17 via a pipeline. The outlet pipe of the resin adsorption tank 17 is connected to the high-purity trichlorosilane product tank 18.

[0020] In a preferred embodiment, the middle section of the catalytic reactive distillation column 6 is filled with a catalyst bed 13.

[0021] In a preferred embodiment, the feed inlet 12 of the catalytic reactive distillation column is located above the catalyst bed 13.

[0022] In a preferred embodiment, the bottom outlet 19 of the catalytic reaction distillation column 6 is connected to the silicon tetrachloride recovery system via a pipeline.

[0023] In a preferred embodiment, the vapor phase outlet 20 at the top of the primary distillation column 1 is connected via a pipeline to the heat medium inlet 21 of the reboiler of the high and low boiling concentration column 2.

[0024] In a preferred embodiment, the vapor phase outlet 22 at the top of the high-low boiling concentration tower 2 is connected via a pipeline to the heat medium inlet 23 of the reboiler of the product trichlorosilane distillation tower 3.

[0025] In a preferred embodiment, there are two resin adsorption tanks 17, which are connected in parallel to the pipeline at the vapor phase outlet 16 of the product trichlorosilane distillation column via a pipeline. Switching valves are provided at the inlet and outlet ends of the two parallel pipelines containing the two resin adsorption tanks 17.

[0026] In a preferred embodiment, the bottom outlet of the crude distillation column 1 is connected via a pipeline to the inlet 15 of the product trichlorosilane distillation column 3.

[0027] In a preferred embodiment, the bottom outlet of the high- and low-boiling-point concentration tower 2 is connected to the feed inlet of a de-weighting tower via a pipeline.

[0028] In a preferred embodiment, the adsorbent packed in the protective bed 4 is a molecular sieve or modified alumina; The adsorbent filled in the activated carbon adsorption tank 5 is coal-based granular activated carbon.

[0029] The operating principle of the entire system is as follows: 1. Principle of graded adsorption and protection: In production, the raw material trichlorosilane first flows through a forced series path from the protective bed 4 to the activated carbon adsorption tank 5. The core of this process lies in achieving a division of labor between precise protection and broad-spectrum purification. The protective bed 4, acting as the system's outpost, utilizes the shape-selective adsorption capacity of molecular sieves to deeply remove trace amounts of moisture, oxygen-containing / nitrogen-containing compounds, and other catalytic poisons from the raw material. Its primary goal is to protect the expensive downstream catalysts and resins, ensuring the production unit can achieve long-term, poison-free, and stable operation. Subsequently, the material enters the activated carbon adsorption tank 5, where the large specific surface area of ​​activated carbon is used to primarily adsorb relatively high levels of impurities such as boron, phosphorus, and metal compounds from the raw material. This two-stage series configuration significantly reduces the operating load and impurity handling pressure of the subsequent main distillation system from the source.

[0030] 2. The coupling principle of impurity directional transport and reaction separation: This system utilizes a dedicated channel for side-stream sampling and reactive distillation to target the most difficult-to-separate impurity, methyldichlorosilane (MDCS). In actual operation, the primary distillation column 1 precisely controls the temperature and concentration distribution in the rectification section, accurately collecting a narrow fraction rich in MDCS from the side-stream sampling outlet 8, and directly introducing it into the high-low boiling concentration column 2 for concentration. This high-concentration MDCS material then enters the catalytic reactive distillation column 6 through the side-stream sampling outlet 10 of the high-low boiling concentration column, along with silicon tetrachloride from the silicon tetrachloride replenishment pipe 11. The catalytic reactive distillation column 6 is the core of the process; its internal catalyst bed 13 promotes the disproportionation reaction of MDCS, converting it into light and heavy components with significant boiling point differences that are easily separated by conventional distillation. Simultaneously, the distillation process within the column immediately removes the reaction products from the reaction zone, disrupting the reaction equilibrium, thereby achieving a high conversion rate of MDCS under mild conditions. Ultimately, the purified main material is returned to the main product stream from the vapor return outlet 14 at the top of the catalytic reactive distillation column, while the heavy components generated by the conversion are discharged and recovered from the bottom outlet 19 of the catalytic reactive distillation column. This connection forms a closed loop of precise extraction → efficient conversion → instant separation, fundamentally solving the problem of MDCS accumulation affecting product quality.

[0031] 3. The principle of energy cascade utilization: In terms of energy management, this system achieves deep energy savings through differential pressure thermal coupling. Specifically, the overhead steam from the higher-pressure crude distillation column 1 is directly introduced through the column's overhead vapor sampling outlet 20 to the reboiler heat medium inlet 21 of the lower-pressure high-low boiling concentration column 2 as a heat source. Similarly, the steam from the top of the high-low boiling concentration column 2 provides heat to the reboiler heat medium inlet 23 of the product trichlorosilane distillation column 3 through its overhead vapor sampling outlet 22. This design concept essentially recovers the latent heat of condensation of the overhead steam from the previous distillation column as the heat energy required for the boiling of the subsequent column, achieving in-situ cascade utilization of energy. In actual operation, this significantly reduces the system's total demand for external fresh steam, directly resulting in a significant reduction in production energy consumption and outstanding economic benefits.

[0032] 4. Final Refining and Protection Principles: After undergoing the aforementioned multi-stage purification, trichlorosilane is purified to an extremely high purity at the top of the product trichlorosilane distillation column 3. The key connection here is that the top-grade material is transported to the tail-end resin adsorption tank 17 for final processing via the vapor phase outlet 16 at the top of the product trichlorosilane distillation column. Since most impurities have been effectively removed in the upstream processes, the resin adsorption unit here only performs final polishing, responsible for capturing trace amounts of residual impurities. This process layout results in an extremely low resin adsorption load, which not only extends its service life and significantly reduces the cost per production run, but more importantly, provides a reliable and economical final guarantee for the final product to consistently meet or even exceed electronic-grade standards.

Claims

1. A composite adsorption system for removing impurities by distillation of trichlorosilane, characterized in that: It includes a crude distillation primary column (1), a high and low boiling concentration column (2), a product trichlorosilane distillation column (3), a protective bed (4), an activated carbon adsorption tank (5), a catalytic reaction distillation column (6), and a resin adsorption tank (17). The outlet of the protective bed (4) is connected to the inlet of the activated carbon adsorption tank (5), and the outlet of the activated carbon adsorption tank (5) is connected to the feed port (7) of the primary distillation column (1) on the cylinder of the primary distillation column (1) through a pipeline. The crude distillation first-stage column (1) side outlet (8) on the shell is connected to the high and low boiling concentration column (2) feed inlet (9) on the shell through a pipeline. The high and low boiling concentration tower (2) side line outlet (10) on the cylinder is connected to the silicon tetrachloride replenishment pipe (11) through a pipeline and then connected to the catalytic reaction distillation tower inlet (12) on the cylinder of the catalytic reaction distillation tower (6). The vapor phase outlet (14) at the top of the catalytic reaction distillation column (6) is connected to the product trichlorosilane distillation column feed inlet (15) on the shell of the product trichlorosilane distillation column (3) via a pipeline. The vapor phase outlet (16) at the top of the product trichlorosilane distillation column (3) is connected to the inlet of the resin adsorption tank (17) via a pipeline; The outlet pipe of the resin adsorption tank (17) is connected to the high-purity trichlorosilane product tank (18).

2. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: The catalyst bed (13) is filled in the middle of the catalytic reaction distillation column (6).

3. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 2, characterized in that: The feed inlet (12) of the catalytic reaction distillation column is located above the catalyst bed (13).

4. A composite adsorption system for removing impurities from trichlorosilane by distillation according to any one of claims 1-3, characterized in that: The bottom outlet (19) of the catalytic reaction distillation column (6) is connected to the silicon tetrachloride recovery system via a pipeline.

5. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: The vapor phase outlet (20) at the top of the primary distillation column (1) is connected via a pipeline to the heat medium inlet (21) of the reboiler of the high and low boiling concentration column (2).

6. A composite adsorption system for removing impurities from trichlorosilane by distillation according to claim 1 or 5, characterized in that: The vapor phase outlet (22) at the top of the high-low boiling concentration tower (2) is connected by a pipeline to the heat medium inlet (23) of the reboiler of the product trichlorosilane distillation tower (3).

7. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: There are two resin adsorption tanks (17). The two resin adsorption tanks (17) are connected in parallel to the pipeline at the vapor phase outlet (16) of the top of the product trichlorosilane distillation column through a pipeline. Switching valves are provided at the inlet and outlet ends of the two parallel pipelines where the two resin adsorption tanks (17) are located.

8. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: The bottom outlet of the crude distillation column (1) is connected to the product trichlorosilane distillation column inlet (15) of the product trichlorosilane distillation column (3) via a pipeline.

9. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: The bottom outlet of the high and low boiling concentration tower (2) is connected to the feed inlet of a de-weighting tower via a pipeline.

10. The composite adsorption system for removing impurities by distillation of trichlorosilane according to claim 1, characterized in that: The adsorbent filled in the protective bed (4) is a molecular sieve or modified alumina; The adsorbent filled in the activated carbon adsorption tank (5) is coal-based granular activated carbon.

Images