Efficient boron and phosphorus impurity removal device in granular silicon production

Abstract

The utility model discloses a kind of high-efficiency boron-phosphorus impurity removal devices in granular silicon production, the discharge end of feed line is respectively communicated with the material port of upper distributor, middle distributor and lower distributor, the material port of upper distributor and lower distributor is also respectively communicated with discharge line, two discharge lines are connected with liquid chromatography online analysis device respectively;Upper feed valve is provided on the feed line at the material port of upper distributor, upper discharge valve is provided on the discharge line at the material port of upper distributor;Middle feed valve is provided on the feed line at the material port of middle distributor;Lower feed valve is provided on the feed line at the material port of lower distributor, lower discharge valve is provided on the discharge line at the material port of lower distributor.Affirmative effect: the utility model connection structure is simple, easy to realize, impurity removal is efficient, reach high-purity requirement, ensure granular silicon product pass rate;High degree of automation, reduce error, stable and flexible operation, adapt to industrial production.

Description

Technical Field

[0001] This utility model relates to the field of granular silicon production technology, and in particular to a high-efficiency device for removing boron and phosphorus impurities in granular silicon production. Background Technology

[0002] In the industrial production of granular silicon, the main raw material used is industrial silicon powder, with the commonly used specification being 99# silicon powder. This industrial silicon powder is not pure silicon; in addition to the main element silicon, it also contains various impurity elements, specifically: the total content of iron, aluminum, and calcium is approximately 1%, boron content is 0.0090%, phosphorus content is 0.0080%, and it also contains small amounts of manganese, lead, and carbon. The particle silicon manufacturing process requires a key intermediate product, chlorosilane. Chlorosilane is prepared by the chlorosilane disproportionation method, which uses silicon powder, silicon tetrachloride, and hydrogen as raw materials to produce silane gas. During the generation and transfer of chlorosilane, various impurity elements contained in the raw industrial silicon powder will be carried into the chlorosilane in various forms (such as compounds), directly and negatively affecting the purity of the subsequently prepared particle silicon product. This has become a key factor restricting the improvement of particle silicon purity. To address the issue of removing impurity elements from chlorosilanes, existing technologies primarily employ distillation of chlorosilanes using distillation columns to remove impurity elements from the system along with the bottom product; and utilize adsorbents to adsorb and retain boron and phosphorus impurities in chlorosilanes. The aforementioned existing treatment methods can indeed reduce the content of metal elements, carbon, boron, and phosphorus in chlorosilanes to a certain extent, achieving a preliminary impurity removal effect. However, it should be noted that photovoltaic-grade and electronic-grade granular silicon have extremely stringent requirements for the content of impurity elements, needing to control the content of each impurity element to the level of one part per trillion. Existing impurity removal technologies, while meeting this high purity requirement, reveal significant shortcomings, as follows: The drawbacks of the distillation column discharge process: Although this process can effectively reduce impurity elements, the material discharged from the system along with the bottom product still contains a large amount of usable components. Direct discharge will cause serious material waste and result in significant economic losses. Therefore, the material discharged from the system needs to be treated in a secondary manner, which increases the workload and processing costs of downstream processes and is not conducive to the economy and efficiency of industrial production. The drawbacks of adsorbent adsorption processes: Compared to distillation column discharge processes, adsorbent adsorption processes do not significantly increase the workload of downstream processes or the amount of material discharged, and have certain advantages in terms of ease of operation and material utilization. For example, CN222900478U discloses a boron and phosphorus removal device for the cold hydrogenation product chlorosilane, which removes impurities, mainly boron and phosphorus, and finally returns the product to the chlorosilane storage tank. The impurity removal device uses a resin boron and phosphorus removal adsorption column that combines physical adsorption and chemical adsorption.

[0003] Boron and phosphorus removal adsorption columns are used to adsorb and remove boron and phosphorus impurities from chlorosilanes. However, these columns operate in a "bottom-in, top-out" manner, meaning the chlorosilane enters from the bottom of the column and flows upwards through the adsorbent layer. In this mode, the adsorbent adsorbs impurities layer by layer along the material flow direction, with the adsorbent at the very front (closest to the bottom of the column) reaching saturation first. As operating time increases, the saturated adsorbent at the front can no longer perform its adsorption function, causing a continuous decline in the overall adsorption efficiency of the entire column. When the adsorption efficiency drops to 85%, the retention effect of boron and phosphorus impurities in the chlorosilane weakens significantly. A large amount of unadsorbed boron and phosphorus impurities enter downstream processes with the chlorosilane, severely impacting downstream production and directly causing the final granular silicon product to become substandard. This not only results in economic losses from product scrapping but also increases overall energy consumption due to rework and re-production of substandard products, contradicting the energy-saving and quality-improving requirements of industrial production. Utility Model Content The main purpose of this utility model is to provide a high-efficiency boron and phosphorus impurity removal device in the production of granular silicon. The device removes impurities efficiently, meets high purity requirements, and ensures the qualification rate of granular silicon products. It has a high degree of automation, reduces costs and errors, operates stably and flexibly, and is suitable for industrial production. To achieve the above objectives, the technical solution adopted by this utility model is as follows: a high-efficiency boron and phosphorus impurity removal device in granular silicon production, comprising a feed pipeline and a boron and phosphorus adsorption column, characterized in that it further comprises an upper distributor, a middle distributor, a lower distributor, a discharge pipeline, an online liquid chromatography analysis device, and a controller. The upper distributor, the middle distributor, and the lower distributor are arranged sequentially from top to bottom in the boron and phosphorus adsorption column. The discharge end of the feed pipeline is connected to the inlets of the upper distributor, the middle distributor, and the lower distributor, respectively. The inlets of the upper distributor and the lower distributor are also connected to the discharge pipeline, and the two discharge pipelines are respectively connected to the online liquid chromatography analysis device. An upper feed valve is provided on the feed pipeline at the feed port of the upper distributor, and an upper discharge valve is provided on the discharge pipeline at the feed port of the upper distributor. A central feed valve is provided on the feed pipeline at the feed inlet of the central distributor; A lower feed valve is provided on the feed pipeline at the feed port of the lower distributor, and a lower discharge valve is provided on the discharge pipeline at the feed port of the lower distributor. The signal output terminal of the online liquid chromatography analyzer is connected to the signal input terminal of the controller via a signal connection. The signal output terminal of the controller is connected to the signal input terminals of the upper feed valve, the upper discharge valve, the middle feed valve, the lower feed valve, and the lower discharge valve via a signal connection.

[0004] Furthermore, it also includes a venting pipeline, which is connected to the top of the boron-phosphorus adsorption column. A venting valve is installed on the venting pipeline, and the signal output terminal of the controller is connected to the signal input terminal of the venting valve via a signal connection.

[0005] Furthermore, it also includes a discharge pipeline, and the discharge pipeline is connected to the discharge ports of the middle distributor and the lower distributor respectively. Discharge valves are respectively provided on the discharge pipeline at the discharge port of the middle distributor and the discharge pipeline at the discharge port of the lower distributor. The signal output terminal of the controller is connected to the signal input terminals of the two discharge valves respectively via signal connection.

[0006] This utility model has the following beneficial effects: 1. The connection structure of this utility model is simple and easy to implement, and the impurity removal is highly efficient, achieving high purity requirements. That is, relying on the upper, middle and lower distributors and the four-stage adsorption switching, coupled with online impurity monitoring, the boron and phosphorus in chlorosilane can be reduced from the ppbw level to the ppta level, meeting the requirements of photovoltaic / electronic grade granular silicon. This avoids a large amount of unadsorbed boron and phosphorus impurities from entering the downstream process with the chlorosilane, ensuring the qualification rate of granular silicon products. 2. This utility model has a high degree of automation, reduces costs and errors. The fully closed-loop control system automatically completes the cascade switching and material return without manual intervention, thus reducing operational errors. 3. This utility model is stable and flexible in operation, adaptable to industrial production, can cope with fluctuations in raw material impurities, and can switch stages without stopping the machine; it has a simple structure with no redundant parts, is easy to integrate into existing processes, and its modular design ensures long-term safe and continuous operation. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0007] Figure 1This is a schematic diagram of the overall structure of a high-efficiency boron and phosphorus impurity removal device in the production of granular silicon according to this utility model.

[0008] Figure 2 This is a schematic diagram of the control system for a high-efficiency boron and phosphorus impurity removal device in the production of granular silicon according to this utility model.

[0009] In the diagram: 1. Feed line; 2. Boron-phosphorus adsorption column; 3. Upper distributor; 4. Middle distributor; 5. Lower distributor; 6. Discharge line; 7. Online liquid chromatography analyzer; 8. Controller; 9. Vent line; 10. Discharge line; 11. Upper feed valve; 12. Upper discharge valve; 13. Middle feed valve; 14. Lower feed valve; 15. Lower discharge valve; 16. Vent valve; 17. Discharge valve. Detailed Implementation

[0010] The following is in conjunction with the appendix Figure 1-2 The principles and features of this utility model are described, making the technical means, creative features, and achieved objectives of this utility model easy to understand, and further elaborating on this utility model.

[0011] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0012] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," and "connected," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0013] like Figure 1-2As shown, the technical solution adopted by this utility model is as follows: a high-efficiency boron and phosphorus impurity removal device in the production of granular silicon, which includes a feed line 1 and a boron and phosphorus adsorption column 2. The device further includes an upper distributor 3, a middle distributor 4, a lower distributor 5, a discharge line 6, an online liquid chromatography analyzer 7, a controller 8, a vent line 9, and a discharge line 10. The upper distributor 3, middle distributor 4, and lower distributor 5 are arranged sequentially from top to bottom inside the boron and phosphorus adsorption column 2. The discharge end of the feed line 1 is connected to the inlets of the upper distributor 3, middle distributor 4, and lower distributor 5, respectively. The inlets of the upper distributor 3 and lower distributor 5 are also connected to the discharge line 6, and the two discharge lines 6 are respectively connected to the online liquid chromatography analyzer 7.

[0014] An upper feed valve 11 is installed on the feed line 1 at the feed inlet of the upper distributor 3, and an upper discharge valve 12 is installed on the discharge line 6 at the feed inlet of the upper distributor 3; a middle feed valve 13 is installed on the feed line 1 at the feed inlet of the middle distributor 4; a lower feed valve 14 is installed on the feed line 1 at the feed inlet of the lower distributor 5, and a lower discharge valve 15 is installed on the discharge line 6 at the feed inlet of the lower distributor 5; the signal output terminal of the online liquid chromatography analyzer 7 is connected to the signal input terminal of the controller 8 via a signal connection, and the signal output terminal of the controller 8 is connected to the signal input terminals of the upper feed valve 11, the upper discharge valve 12, the middle feed valve 13, the lower feed valve 14, and the lower discharge valve 15 via a signal connection.

[0015] A venting line 9 is connected to the top of the boron-phosphorus adsorption column 2, and a venting valve 16 is installed on the venting line 9. The signal output terminal of the controller 8 is connected to the signal input terminal of the venting valve 16 via a signal connection.

[0016] The material inlets of the middle distributor 4 and the lower distributor 5 are respectively connected to the discharge pipeline 10. Discharge valves 17 are respectively installed on the discharge pipeline 10 at the material inlet of the middle distributor 4 and the discharge pipeline 10 at the material inlet of the lower distributor 5. The signal output terminal of the controller 8 is respectively connected to the signal input terminal of the two discharge valves 17 through signal connection.

[0017] Working principle: (a) First stage: Initial operation (bottom-in, top-out mode) Operation trigger: The device is being used for the first time, and the adsorbent is in an unsaturated state. Feeding and valve control: Feeding direction: Chlorosilane enters the boron-phosphorus adsorption column 2 via feed line 1 → lower feed valve 14 (open) → lower distributor 5, and after adsorption, it is output via upper distributor 3 → upper discharge valve 12 (open) → discharge line 6. Valve status: Upper feed valve 11, middle feed valve 13, lower discharge valve 15, two return valves, and vent valve 16 are all closed.

[0018] Online monitoring and adjustment: The online liquid chromatography analyzer 7 detects the content of B and P impurities in the chlorosilane at the discharge end every 4 hours; if B element > 10 ppbw or P element > 5 ppbw is detected, the controller 8 triggers the first stage → second stage switching. (ii) Second stage: Dual feeding with increased contact (bottom feed top discharge + middle feed top discharge mode) Operating objective: To split the feed into two streams, increase the contact time between chlorosilane and adsorbent, and reduce the load on the lower part of the adsorbent that comes into contact with impurities first. Feeding and valve control: Feeding direction: Chlorosilane is divided into two streams → ① Lower feed valve 14 (open) → Lower distributor 5; ② Middle feed valve 13 (open) → Middle distributor 4; After the two streams are adsorbed in the boron-phosphorus adsorption column 2, they are output together through the upper distributor 3 → upper discharge valve 12 (open) → discharge pipeline 6. Valve status: Upper feed valve 11, lower discharge valve 15, two return valves, and vent valve 16 remain closed. Online monitoring and adjustment: The discharge impurities are still detected every 4 hours; if B > 10ppbw or P > 5ppbw, the controller 8 triggers the switch from the second stage to the third stage. (III) Third stage: Reverse operation (upward entry and downward exit mode) Operational objective: To utilize the upper portion of the adsorbent in the boron-phosphorus adsorption column 2 that has not fully contacted chlorosilanes to achieve deep adsorption of impurities through reverse feeding. Feeding and valve control: Feeding direction: Chlorosilane enters the boron-phosphorus adsorption column 2 via feed line 1 → upper feed valve 11 (open) → upper distributor 3, and after reverse adsorption, it is output via lower distributor 5 → lower discharge valve 15 (open) → discharge line 6. Valve status: Middle feed valve 13, lower feed valve 14, upper discharge valve 12, two return valves, and vent valve 16 are closed. Online monitoring and adjustment: Detects discharge impurities every 4 hours; if B > 10ppbw or P > 5ppbw, controller 8 triggers the switch from the third stage to the fourth stage. (iv) Fourth stage: Dual feed rate reduction (top feed bottom output + middle feed bottom output mode) Operational objective: To split the feed into two streams, reduce the feed rate of a single stream, ensure sufficient contact between chlorosilane and adsorbent, and maximize the utilization of remaining adsorption capacity. Feeding and valve control: Feeding direction: Chlorosilane is divided into two streams → ① Upper feed valve 11 (open) → Upper distributor 3; ② Middle feed valve 13 (open) → Middle distributor 4; After the two streams are adsorbed in opposite directions in the boron-phosphorus adsorption column 2, they are output together through the lower distributor 5 → lower discharge valve 15 (open) → discharge pipeline 6. Valve status: Lower feed valve 14 and upper discharge valve 12 are closed; 2 discharge valves and vent valve 16 are still closed. Online monitoring and adjustment: If, during the operation of the fourth stage, the online liquid chromatography analysis still detects B > 10 ppbw or P > 5 ppbw, the controller 8 will trigger an "adsorbent is fully saturated" alarm and automatically start the material return procedure.

[0019] (v) Return of materials: Step 1: Controller 8 sends a signal first to close all feed valves (upper feed valve 11, middle feed valve 13, lower feed valve 14) and discharge valves (upper discharge valve 12, lower discharge valve 15), completely cutting off the channel for chlorosilane to enter the boron-phosphorus adsorption column 2 and the channel for material to be output from the column, preventing untreated material from mixing with qualified material. Step 2: Pressure Equilibrium and Venting: Controller 8 opens vent valve 16 (connected to the top of boron-phosphorus adsorption column 2) to slowly release the residual chlorosilane volatile gas and pressure inside the column, so that the pressure inside the column gradually decreases to balance with atmospheric pressure. Step 3: Residual chlorosilane discharge: After the pressure inside the column is balanced, the controller 8 simultaneously opens two discharge valves (connected to the discharge lines 10 of the middle distributor 4 and the lower distributor 5 respectively). The residual liquid chlorosilane in the column is collected through the middle and lower distributors 5 to the discharge line 10, and discharged through the discharge valve to the dedicated chlorosilane recovery tank to avoid material waste and environmental pollution.

[0020] After the material is removed, the adsorbent is replaced.

[0021] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency boron and phosphorus impurity removal device for granular silicon production, comprising a feed pipeline and a boron and phosphorus adsorption column, characterized in that, It also includes an upper distributor, a middle distributor, a lower distributor, a discharge line, an online liquid chromatography analyzer, and a controller. The upper distributor, middle distributor, and lower distributor are arranged sequentially from top to bottom inside the boron-phosphorus adsorption column. The discharge end of the feed line is connected to the inlet of the upper distributor, the middle distributor, and the lower distributor, respectively. The inlets of the upper distributor and the lower distributor are also connected to the discharge line. The two discharge lines are respectively connected to the online liquid chromatography analyzer. An upper feed valve is provided on the feed pipeline at the feed port of the upper distributor, and an upper discharge valve is provided on the discharge pipeline at the feed port of the upper distributor. A central feed valve is provided on the feed pipeline at the feed inlet of the central distributor; A lower feed valve is provided on the feed pipeline at the feed port of the lower distributor, and a lower discharge valve is provided on the discharge pipeline at the feed port of the lower distributor. The signal output terminal of the online liquid chromatography analyzer is connected to the signal input terminal of the controller via a signal connection. The signal output terminal of the controller is connected to the signal input terminals of the upper feed valve, the upper discharge valve, the middle feed valve, the lower feed valve, and the lower discharge valve via a signal connection.

2. The high-efficiency boron and phosphorus impurity removal device in granular silicon production according to claim 1, characterized in that, It also includes a venting pipeline, which is connected to the top of the boron-phosphorus adsorption column. A venting valve is installed on the venting pipeline, and the signal output terminal of the controller is connected to the signal input terminal of the venting valve via a signal connection.

3. The high-efficiency boron and phosphorus impurity removal device in granular silicon production according to claim 1, characterized in that, It also includes a discharge pipeline, and the discharge pipeline is connected to the discharge ports of the middle distributor and the lower distributor respectively. Discharge valves are respectively provided on the discharge pipeline at the discharge port of the middle distributor and the discharge pipeline at the discharge port of the lower distributor. The signal output terminal of the controller is connected to the signal input terminals of the two discharge valves respectively via signal connection.

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