A rapid cycle polysilicon production system

Abstract

This invention discloses a rapid-circulation polycrystalline silicon preparation system, comprising a polycrystalline silicon reactor, a circulation riser, and a heater. The upper part of the polycrystalline silicon reactor is equipped with an exhaust pipe and a silicon particle feed pipe, while the lower part is equipped with a solid product outlet pipe and a silicon-containing raw material gas inlet pipe. The circulation riser is arranged longitudinally, with one end of the solid product outlet pipe connected to the middle of the circulation riser. The upper end of the circulation riser is directly or indirectly connected to the silicon particle feed pipe, and the lower part of the circulation riser is connected to a hot air pipe. The heater is used to heat the airflow entering the hot air pipe to obtain hot air. This invention directly heats the silicon particles outside the reactor and uses high-temperature hot air to rapidly circulate the silicon particles in the circulation riser, simultaneously completing the heating and classification of the silicon particles, improving the wall deposition problem, enabling long-cycle operation, and significantly expanding production capacity.

Description

Technical Field

[0001] This invention belongs to the field of polycrystalline silicon production technology, and specifically relates to a rapid-cycle polycrystalline silicon preparation system. Background Technology

[0002] High-purity polycrystalline silicon has always been a fundamental raw material for the semiconductor and photovoltaic industries. The main methods for preparing polycrystalline silicon include the modified Siemens process and the silane fluidized bed process.

[0003] The modified Siemens process is currently the mainstream technology in the polysilicon industry. Its core process involves purifying the raw material trichlorosilane (SiHCl3) through distillation, mixing it with high-purity hydrogen, and then feeding it into a reduction furnace reactor. A chemical vapor deposition reaction occurs on the surface of the silicon core within the reactor (temperature 1000-1150℃), depositing the resulting silicon onto the core and gradually thickening it. The reaction tail gas contains trichlorosilane, dichlorosilane, silicon tetrachloride, hydrogen, and hydrogen chloride, which are recovered, separated, and distilled for recycling. After the silicon core has grown into a polycrystalline silicon rod of a certain diameter, the furnace is shut down and replaced, and the silicon rod is removed. The silicon rod is then crushed and packaged. This process is characterized by a long flow, high reaction temperature, low conversion rate, low production capacity, intermittent operation, low relative volatility of raw materials and major impurities, and difficulty in separation, resulting in high investment, high energy consumption (especially electricity consumption), and high costs.

[0004] To address this, a silane fluidized bed process has been further developed in this field. This process uses silane (SiH4) as a raw material, which is purified and fed into a fluidized bed reactor (with seed crystals) in a specific proportion. Within the reactor, it decomposes to generate silicon. Theoretically, the silicon deposits on the seed crystals, causing them to gradually grow and form granular silicon of the required size. The byproduct gas is a single type of hydrogen gas, which is recycled to the upstream process for silane production. The grown granular silicon is continuously collected from the reactor, screened to obtain the product, and smaller particles are returned to the reactor for further growth. A small amount of the product is also crushed and used as seed crystals to replenish the reactor, maintaining continuous production. Theoretically, this process has advantages such as a short process flow, low reaction temperature, high conversion rate, high reactor capacity, continuous operation, low difficulty in silane separation, and no need for product crushing.

[0005] In actual production, the reactor generates a large number of bubbles under fluidized conditions, resulting in numerous homogeneous reactions within these bubbles. This generates a significant amount of dust, some of which is carried out of the system, leading to a reduced product yield. Furthermore, the homogeneous reactions produce numerous dangling bonds, resulting in a hydrogen-containing product with a loose structure, making it prone to fine powder generation during transportation and use. All of these factors contribute to low product quality and difficulties in downstream applications. Due to the presence of these homogeneous reactions, production can only be carried out at lower pressures and lower silane concentrations; otherwise, even more dust will be generated. In addition, the generation of these bubbles causes a small amount of silane to be carried out of the reactor before reaching the reaction temperature, requiring subsequent separation and recovery processes. This reduces yield while increasing energy consumption and investment. Moreover, the heating method can easily lead to wall deposition, resulting in a short production cycle and low production capacity.

[0006] CN105819449A discloses a silane moving bed reactor and a method for producing particulate polycrystalline silicon using the reactor. It adopts a moving bed scheme and mentions the circulation and heating of solid materials, but the two are separate. That is, the low-temperature particles are circulated to the preheating system and heated in the preheating system, but the implementation method of circulation is not specifically described.

[0007] CN104803386A discloses a fluidized bed riser reactor and method for preparing high-purity polycrystalline silicon particles. It adopts a circulating fluidized bed reactor, which uses gas to transport particles and then achieves particle circulation through gas-solid separation. The heating method is to heat the external wall of the system, including a riser or a solid particle collection mechanism. The riser is used as the reactor, a cyclone is used as the gas-solid separation device, and fluidizing gas is used for particle classification, but the effect is poor.

[0008] In addition, CN11853400A also discloses a silane moving bed reaction system, including a heater, a reactor, and a stripper, wherein the outlet of the heater is connected to the inlet of the reactor, and the outlet of the reactor is connected to the inlet of the stripper; polycrystalline silicon enters the heater and is heated to the reaction temperature, and the heated polycrystalline silicon enters the reactor from top to bottom to undergo crystal growth, while the reaction gas enters the reactor from bottom to top and comes into countercurrent contact with the polycrystalline silicon in the reactor and reacts, and the tail gas after the reaction is discharged from the top of the reactor; the reacted polycrystalline silicon enters the stripper for stripping. Although the product is screened externally and unqualified materials are fed into the seed crystal preparation unit, the design of its heating and feeding methods can easily lead to uneven bed temperature, incomplete silane reaction, and powder entrainment in the tail gas. To address this, a filter element is installed at the tail gas outlet of the reactor, which increases the system complexity and pollution risk. In addition, the head design at the bottom of the reactor adds an extra support force to the bed, thereby reducing the bed head. The particle flow rate in the entire bed above the support surface is slow, the particle flow rate is greatly reduced, and it is easy to form a central flow. The material near the wall will remain for a long time, resulting in poor flowability and the risk of agglomeration.

[0009] CN103787336A discloses a method for producing high-purity granular silicon, which requires the addition of auxiliary gas to maintain the bed state. However, the addition of auxiliary gas increases energy consumption, and its distribution plate is prone to clogging. Both the auxiliary gas and the reactant gas are dispersed in the reaction chamber, which can easily lead to the reactant gas diffusing to the wall and posing a risk of wall deposition. Therefore, an air curtain device is added, making the overall structure very complex and difficult to operate. In addition, although it adopts an external sieving method to transport unqualified materials to the preheating system, and the circulation and heating are separated, the particles in the bed itself move slowly and the heat transfer efficiency is poor, which can easily lead to uneven bed temperature and incomplete reaction of silane. Therefore, a tail gas separation mechanism is added, which makes the particle surface loose and easy to produce fine powder. Therefore, a surface treatment mechanism is added, which is inefficient and makes the system more complex. Utility Model Content

[0010] The purpose of this invention is to provide a rapid cycle polycrystalline silicon preparation system for the efficient preparation of granular polycrystalline silicon products.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A rapid-cycle polycrystalline silicon fabrication system, the polycrystalline silicon fabrication system comprising:

[0013] A polycrystalline silicon reactor is provided with an exhaust pipe and a silicon particle feed pipe for inputting high-temperature silicon particles at the top, and a solid product outlet pipe and a silicon-containing raw material gas inlet pipe for introducing silicon-containing raw material gas at the bottom. The polycrystalline silicon reactor is used to contact and react the silicon-containing raw material gas with high-temperature silicon particles as seed crystals, so that silicon generated from the decomposition of the silicon-containing raw material gas is deposited and grown on the surface of the silicon particles. The grown silicon particles are discharged from the solid product outlet pipe and the tail gas after reaction is discharged from the exhaust pipe.

[0014] A circulating riser is provided, which is arranged longitudinally. The other end of the solid product outlet pipe is connected to the middle of the circulating riser to feed the grown silicon particles discharged from the polycrystalline silicon reactor into the circulating riser. The upper end of the circulating riser is directly or indirectly connected to the silicon particle feed pipe, and the lower part of the circulating riser is connected to a hot air pipe for sending hot air into the circulating riser to classify the grown silicon particles. The smaller particles are heated to a temperature sufficient to decompose the silicon-containing raw material gas and fed upward into the silicon particle feed pipe as high-temperature silicon particles. The remaining larger particles are discharged downward as polycrystalline silicon products.

[0015] A heater is used to heat the airflow entering the hot air duct to obtain the hot air.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) This invention directly heats silicon particles outside the reactor and uses high-temperature hot air to make the silicon particles circulate rapidly in the circulating riser, thereby completing the heating and classification of silicon particles at the same time. In addition, since the silicon-containing raw material gas is directly heated on the silicon particles, the heating area is greatly increased, and the problems of wall deposition and lining damage are greatly improved, enabling long-term operation. Furthermore, since it is easy to replenish sufficient heat (the amount of hot particles), the size of the reactor of this invention is not limited by the heating conditions, so it can be greatly enlarged to expand the production capacity, and it is also conducive to the high-speed movement of particles to prevent agglomeration.

[0018] (2) In this utility model, a circulating riser is used instead of a reactor. Instead, the circulating riser is used to complete the classification, circulation and heating of silicon particles by taking advantage of its rapid circulation, large transport capacity and high heat transfer intensity. At the same time, the silicon particles are repeatedly heated by high-temperature hot air at a higher temperature, rather than the reaction temperature in the existing fluidized bed. Therefore, it is beneficial to the complete breaking of silicon-hydrogen bonds, so that the product has a complete crystal form and a dense structure.

[0019] (3) By setting a variable diameter section on the circulating riser, this utility model can enhance particle classification and heat transfer effect; by using multiple variable diameter sections, the gas velocity of hot gas can be continuously changed, silicon particles can be separated multiple times, the separation effect can be enhanced, and the heat transfer effect can be enhanced.

[0020] (4) This invention employs a conical polycrystalline silicon reactor with an integral conical design in the reaction section, which facilitates rapid movement of particles in the reaction bed and, during downward movement, the relative movement between particles effectively prevents particle agglomeration. Furthermore, the reaction section of this invention does not require additional auxiliary gas intake, and the conical design promotes gas reaction expansion and diffusion, preventing bubble generation within the reactor and thus avoiding homogeneous reactions, significantly reducing dust generation and improving product yield. Moreover, due to the absence of bubbles, silanes react 100%, and there is no silane in the tail gas, reducing the need for subsequent tail gas separation processes. Additionally, this invention allows the raw material gas to be fed radially to the center of the reaction section, which... This invention facilitates heat exchange and concentration of the reaction zone within the reactor, resulting in a large product deposition area and a dense product structure, while also reducing wall deposition. Furthermore, by setting a ring at the lower end of the settling section to form an annular platform, this invention effectively prevents direct impact of the feed onto the reactor wall while enabling lateral feeding. Simultaneously, the accumulated silicon particles achieve a dynamic balance between particle slippage caused by the lateral feed impact and the silicon particles carried in by the feed airflow, as well as the particles deposited within the settling section. Finally, the invention utilizes a conveying duct at the lower part of the sealing section, which, in conjunction with the sealing and conveying sections, facilitates rapid transport of solid materials within the conveying section, better accommodating the rapid movement of particles within the reactor.

[0021] In summary, this utility model enables large-scale equipment, significantly increases production capacity, improves product quality, reduces costs, shortens processes, reduces investment, and reduces carbon emissions, resulting in substantial economic benefits. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of one embodiment of the polycrystalline silicon preparation system of this utility model;

[0023] Figure 2 This is a schematic diagram of another embodiment of the polycrystalline silicon preparation system of this utility model;

[0024] Figure 3 for Figure 1 A schematic diagram of one embodiment of the conical polycrystalline silicon reactor. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as values ​​±10% of the endpoint values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Without conflict, the embodiments and features described in this application can be combined with each other.

[0027] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0028] like Figure 1 As shown, the polycrystalline silicon preparation system of this utility model includes a polycrystalline silicon reactor 1, a circulating riser 2, and a heater 3; wherein, the upper part of the polycrystalline silicon reactor is provided with an exhaust pipe 13 and a silicon particle feed pipe 12 for inputting high-temperature silicon particles, and the lower part is provided with a solid product outlet pipe 16 and a silicon-containing raw material gas inlet pipe 15 for introducing silicon-containing raw material gas. The polycrystalline silicon reactor 1 is used to contact and react the silicon-containing raw material gas with the high-temperature silicon particles as seed crystals, so that the silicon generated from the decomposition of the silicon-containing raw material gas is deposited and grown on the surface of the silicon particles, and the grown silicon particles are discharged from the solid product outlet pipe 16 and the reaction tail gas is discharged from the exhaust pipe 13.

[0029] The circulating riser 2 is arranged longitudinally, and the other end of the solid product outlet pipe 16 is connected to the middle of the circulating riser 2 to send the grown silicon particles discharged from the polycrystalline silicon reactor 1 into the circulating riser 2; the upper end of the circulating riser 2 is directly or indirectly connected to the silicon particle feed pipe 12, and the lower part of the circulating riser 2 is connected to a hot air pipe 21 for sending hot air into the circulating riser 2 and performing airflow classification on the grown silicon particles, so that the smaller particles separated are heated to a temperature sufficient to decompose the silicon-containing raw material gas and sent upward into the silicon particle feed pipe 12 as the high-temperature silicon particles, while the remaining larger particles are discharged downward as polycrystalline silicon products.

[0030] The heater 3 is used to heat the airflow entering the hot air duct 21 to obtain the hot air. The specific selection of the heater 3 is well known in the art, such as electric heating / radiation heating / electromagnetic heating, etc., and will not be described in detail here.

[0031] In some embodiments, it will be understood in the art that when the upper end of the circulating riser 2 is directly connected to the silicon particle feed pipe 12, the gas-solid mixture sent from the upper end of the circulating riser 2 can directly enter the silicon particle feed pipe 12 and then undergo gas-solid separation in the upper part of the polycrystalline silicon reactor 1. For example, the upper part of the polycrystalline silicon reactor has sufficient space to facilitate gas-solid separation, with silicon particles settling downwards and gas rising and discharging. When the upper end of the circulating riser 2 is indirectly connected to the silicon particle feed pipe 12, the gas-solid mixture sent from the upper end of the circulating riser 2 can undergo gas-solid separation before entering the silicon particle feed pipe. For example, gas-solid separation can be performed first in a cyclone separator, and then the separated silicon particles can be sent into the silicon particle feed pipe 12.

[0032] In some embodiments, the circulating riser 2 has one or more diameter-enlarging variable sections 22 at the connection point with the solid product outlet pipe 16 and in the section of the circulating riser between the hot air pipe and the solid product outlet pipe. By varying the diameter of these variable sections among the other pipe sections, the gas velocity of the hot gas is continuously changed, which is beneficial for enhancing particle classification and heat transfer. This allows for direct separation of the product within the circulating riser, especially through multiple diameter changes, achieving continuous changes in the gas velocity of the hot gas and multiple separations of silicon particles, thus enhancing classification and heat transfer. It will be understood in the art that the section of the circulating riser 2 between the hot air pipe 21 and the solid product outlet pipe 16 does not include the connection point between the circulating riser and the solid product outlet pipe, or the connection point between the circulating riser and the hot air pipe. Preferably, the circulating riser pipe has a variable diameter section 22 at the connection point with the solid product outlet pipe. The expansion section facilitates the direct settling of large particles when airflow containing product particles of different sizes enters, resulting in better classification effect. More preferably, the circulating riser pipe has a variable diameter section 22 at the connection point with the solid product outlet pipe, and the section of the circulating riser pipe between the hot air pipe and the solid product outlet pipe has one or two or more variable diameter sections.

[0033] In one implementation, such as Figure 1 As shown, the polycrystalline silicon preparation system also includes a buffer tank 4 and a cooler 5; wherein the buffer tank 4 is connected to the lower end of the circulating riser 2 and is used to buffer the polycrystalline silicon product discharged from the circulating riser 2; in this utility model, the buffer tank can not only play a role in buffering the product discharge, but also isolate the hot air from the cooler, which is conducive to the upward conveying of hot air.

[0034] The cooler 5 is connected to the buffer tank 4 and is used to cool the polysilicon product discharged from the buffer tank. In one embodiment, the cooler 5 includes a housing 51, and a gas distributor 52 is provided at the lower part of the housing, thereby dividing the interior of the housing into an inlet zone below the gas distributor 52 and a cooling zone above the gas distributor; a polysilicon product feed pipe 56 extending downward into the cooling zone is provided at the top of the cooling zone for feeding polysilicon product into the cooling zone and depositing it on the gas distributor 52 to form a polysilicon product bed; the inlet zone is provided with a cooling gas inlet to introduce cooling gas to cool the polysilicon product deposited on the gas distributor 52; the cooling zone is provided with a cooling gas outlet, which is higher than the lower end of the polysilicon product feed pipe 56, to discharge the cooling gas after heat exchange and temperature rise with the polysilicon product; the gas distributor... The gas distributor 52 is equipped with a polycrystalline silicon product discharge pipe, for example, a polycrystalline silicon product discharge pipe 57 extending downwards to the outside of the cooler housing is provided in the center of the gas distributor; the cooler 5 is used to cool the polycrystalline silicon products accumulated on the gas distributor by using the rising cooling air introduced from the gas inlet area, and to discharge the cooled polycrystalline silicon products from the bottom of the polycrystalline silicon product bed through the polycrystalline silicon product discharge pipe 57; it is understood in the art that during operation, the polycrystalline silicon product bed accumulates to the lower end of the polycrystalline silicon product feed pipe. When the cooled polycrystalline silicon products are discharged, causing the height of the polycrystalline silicon product bed to drop, the polycrystalline silicon product feed pipe will automatically feed into the polycrystalline silicon product bed, making the polycrystalline silicon product bed as high as the lower end of the polycrystalline silicon product feed pipe, isolating the hot air from the cooler, which is conducive to the upward conveying of hot air.

[0035] In this invention, the polycrystalline silicon preparation system further includes a pressure-bearing outer shell 80 for housing the polycrystalline silicon reactor 1 and the circulation riser 2, and can further house a buffer tank 4 and a cooler 5 as pressure-bearing components of the system.

[0036] In one implementation, such as Figure 2 As shown, the polycrystalline silicon preparation system further includes an exhaust gas heat exchange unit 30, an exhaust gas dust removal unit 40, and a circulating gas compressor 50; wherein, the exhaust gas heat exchange unit 30 is used to cool the exhaust gas from the exhaust pipe 13 of the polycrystalline silicon reactor 1 using circulating gas to recover heat, and sends the heated circulating gas into the heater 3 for further heating, so as to be sent into the circulating riser pipe 2 as hot air; the exhaust gas heat exchange unit can be a heat exchanger, which is well known in the art and will not be described in detail here.

[0037] The exhaust gas dust removal unit 40 is used to remove dust from the exhaust gas from the exhaust gas heat exchange unit 30 to obtain dust-removed exhaust gas. It is understood in the art that a dust collector, such as a bag filter, can be used for dust removal, which is well known in the art and will not be described in detail here.

[0038] The circulating gas compressor 50 is used to pressurize the dust removal exhaust gas so that it can be sent into the exhaust gas heat exchange unit as circulating gas. In some embodiments, the dust removal exhaust gas can also be sent to an adsorption unit for gas separation before being sent into the circulating gas compressor 50. For example, pressure swing adsorption or temperature swing adsorption can be used to separate impurity gases and / or hydrogen (hydrogen is produced by the decomposition of silane) brought in during the gas circulation process. The separated hydrogen can be further sent out as by-product hydrogen.

[0039] In one implementation, such as Figure 2 As shown, the polysilicon preparation system also includes a product tank 60, which is used to receive polysilicon products discharged from the polysilicon preparation system; wherein, dual product tanks can be set up for intermittent operation, with one product tank receiving material and the other product tank being pneumatically conveyed to the system's outer packaging.

[0040] In one implementation, such as Figure 2 As shown, the polycrystalline silicon preparation system also includes a seed crystal preparation unit 70. The seed crystal preparation unit 70 is used to crush the polycrystalline silicon product discharged from the polycrystalline silicon preparation system and send it back to the polycrystalline silicon reactor as fine seed crystals (seed crystals) to maintain the silicon particle storage in the polycrystalline silicon reactor. Since the amount added per unit time is very small (the amount of polycrystalline silicon product is tens of times that of the fine seed crystals), the impact is small.

[0041] For example, most of the polycrystalline silicon product discharged from the cooler 5 enters the product tank 60, and a small portion enters the seed crystal preparation unit 70.

[0042] In one implementation, such as Figure 2 As shown, the polycrystalline silicon preparation system further includes a first cold air pipe 53 and a second cold air pipe 55; wherein the first cold air pipe 53 is connected to the cooling air inlet of the cooler 5 and is used to send cooling air into the cooler to cool the incoming polycrystalline silicon product; the second cold air pipe 55 is connected to the cooling air outlet of the cooler 5 and the exhaust gas dust removal unit 40 respectively, and is used to send the heated cooling air from the cooler as part of the exhaust gas into the exhaust gas dust removal unit.

[0043] In some embodiments, the polycrystalline silicon reactor 1 can be a fluidized bed reactor or a moving bed reactor; in other embodiments, such as Figure 3As shown, the polycrystalline silicon reactor is a conical polycrystalline silicon reactor, which includes a conical reaction section 14 with a gradually decreasing diameter from top to bottom and a settling section 11 disposed above the conical reaction section. The settling section 11 has an exhaust pipe 13 at its top and a silicon particle feed pipe 12 for gas delivery as seed crystals on its sidewall. The settling section 11 is used to separate silicon particles from the gas-solid mixture from the silicon particle feed pipe 12, so that the silicon particles settle into the conical reaction section 14 to form a silicon particle bed. Those skilled in the art will understand that when the gas-solid mixture carrying particles suddenly enters a large space, the flow rate decreases sharply. With sufficient space in the settling section, the particles will settle and separate from the carrier gas.

[0044] The upper end of the conical reaction section 14 is connected to the lower end of the settling section 11. The bottom of the conical reaction section 14 is provided with a solid product outlet pipe 16 and the side wall is provided with a silicon-containing raw material gas inlet pipe 15. The conical reaction section 14 is used to make the rising silicon-containing raw material gas contact and react with the descending silicon particle bed, so that the silicon produced by the decomposition of the silicon-containing raw material gas introduced from the silicon-containing raw material gas inlet pipe 15 is deposited and grown on the surface of the silicon particles used as seed crystals, and the grown silicon particles are discharged from the solid product outlet pipe 16.

[0045] In this invention, the gas-solid mixture fed from the silicon particle feed pipe 12 undergoes gas-solid separation in the settling section 11. The exhaust gas exits from the top, while the silicon particles sink into the conical reaction section 14 to form a bed, where they come into countercurrent contact with the silicon-containing raw material gas. This allows the silicon generated from the decomposition to deposit and grow on the surface of the silicon particles, and finally exits from the bottom. Those skilled in the art will understand that in the product discharged from the solid product outlet pipe 16, insufficiently grown silicon particles can be separated and recycled back to the reactor as seed crystals for continued growth; this is well-known in the art and will not be elaborated upon here.

[0046] In this invention, the settling section 11 is used to provide a gas-solid separation settling space. Its diameter can gradually increase from bottom to top or remain constant, such as a cylindrical shape or a frustum shape with a larger diameter at the top and a smaller diameter at the bottom. In addition, its height should be sufficient to allow silicon particles in the gas-solid mixture to settle sufficiently, for example, sufficient to allow silicon particles with a particle size greater than 0.01 mm to settle sufficiently, for example, the settling rate can reach 99.99%. It is understood in the art that silicon dust directly decomposed from silicon-containing raw material gas and not deposited on the surface of silicon particles is difficult to settle naturally in the rising exhaust gas. It is necessary to optimize from other aspects to reduce the generation of silicon dust, such as the full conversion of silane, collection in the silicon particle bed, and reduction of collision and friction crushing in this invention.

[0047] In this invention, it will be understood in the art that the lower end of the settling section 11 can be directly connected to or connected to the upper end of the conical reaction section 14 via other transition sections. For example, in conventional embodiments, the settling section 11 is typically connected via a narrowing section that is larger at the top and smaller at the bottom, such as connecting to the upper end of the conical reaction section 14. The cone angle (the angle between the two generatrices of the axial section of the cone) of the conical reaction section 14 can be 15-50°, for example, 20, 25, 30, 35, 40, or 45°, such as 20-40°.

[0048] In this invention, the outlets of the silicon-containing raw material gas inlet pipe 15 can typically be multiple, arranged circumferentially and / or longitudinally along the conical reaction section 14, to ensure more uniform feeding of the silicon-containing raw material gas. In one embodiment, the outlet of the silicon-containing raw material gas inlet pipe 15 extends radially to near the radial center of the conical reaction section 14 (i.e., the center of the horizontal circular cross-section of the conical reaction section), so that the silicon-containing raw material gas is fed into the central region surrounding the central axis of the conical reaction section 14. Preferably, the distance between the outlet of the silicon-containing raw material gas inlet pipe 15 and the central axis of the conical reaction section 14 is (1 / 10-2 / 3)R, more preferably (1 / 8-1 / 2)R, such as 1 / 6R, 1 / 4R, or 1 / 3R, so that the silicon-containing raw material gas can be fed into the radial center of the conical reaction section 14, where R is the radius of the circular cross-section of the conical reaction section on the horizontal plane where the silicon-containing raw material gas inlet pipe is located.

[0049] It is understood in the art that, to prevent premature decomposition of the feed gas, the feed gas fed into the reactor is usually a relatively low-temperature cold gas (e.g., temperature not exceeding 400°C, such as 25, 50, 100, 200, or 300°C). To ensure uniform gas distribution, the feed gas is usually distributed as much as possible along the inner wall of the reactor. However, in this invention, for the overall conical reaction section design, the cone angle remains constant or changes very little from top to bottom, such as not exceeding 10° or 5°. Research has found that concentrating the feed gas in the middle of the conical reaction section 14 allows the feed gas to preferentially contact the silicon particles with the fastest downward flow velocity within the conical reaction section 14 (thus better maintaining its feed heat), resulting in high reaction efficiency. Simultaneously, the gas temperature rises after contact, and the volume of the reaction-generated gas expands exponentially. The conical design also facilitates the rapid upward diffusion of the remaining gas to the entire bed cross-section for reaction. Because the low-temperature gas contacts the high-velocity particles in the middle first, the Reynolds number is high, and the heat transfer coefficient is also high. The main heat exchange is completed instantly, the gas temperature reaches the decomposition temperature, and the reaction is basically complete. During the radial diffusion process, contact with particles with lower flow rates ensures that the gas temperature and particle temperature are consistent, resulting in a more uniform temperature across the entire cross-section. This is beneficial for gas reaction and deposition, further improving the reactor conversion rate. Furthermore, due to the overall conical design of the reaction section, although the silicon particles near the inner wall of the conical reaction section 14 have a lower downward velocity compared to the silicon particles in the middle, their absolute and relative moving velocities are still higher. Therefore, even with a small amount of residual gas diffusing and reacting efficiently, it is still possible to effectively prevent the silicon particles near the inner wall of the conical reaction section 14 from agglomerating. In addition, the overall conical design of the reaction section also facilitates the deceleration of the rising airflow due to volume expansion caused by heating and reaction, ensuring a stable bed without fluidization or bubble generation. Moreover, through the settling section and cross-mixing with the transverse airflow within the settling section, the gas velocity can be reduced, and solid entrainment can be minimized.

[0050] In this invention, the silicon-containing raw material gas inlet pipe 15 can be provided in one set or multiple sets, such as 2-4 sets, at different heights. Each set includes multiple (e.g., 2-6) silicon-containing raw material gas inlet pipes 15 evenly distributed circumferentially along the conical reaction section 14 on the same plane, so as to feed the raw material from multiple positions to the radial center of the conical reaction section 14. In some embodiments, the outlet of the silicon-containing raw material gas inlet pipe 15 can be located at 1 / 6-2 / 3, such as 1 / 5-1 / 2, such as 1 / 4 or 1 / 3 of the height of the conical reaction section from bottom to top, which is more conducive to sufficient contact and reaction with silicon particles in the conical reaction section 14. It is understood in the art that if the height is too low, some raw material gas may flow downward or even generate bubbles, resulting in a decrease in yield, while if it is too high, the reaction section may become shorter, resulting in a decrease in conversion rate.

[0051] In this invention, the silicon particle feed pipe 12 introduces silicon particles into the reactor via gas delivery. Preferably, the silicon particle feed pipe is horizontally positioned towards the central axis of the settling section 11 so that the gas-solid mixture is fed in a generally horizontal direction. This avoids the problem of excessive upward tilting which would hinder settling, and excessive downward tilting which would affect the rising airflow from the conical reaction section 14 and cause the particles in the feed to have a greater impact force due to gravity acceleration. However, if the feed is horizontally tangential, it is easy to cause wear between the silicon particles and the reactor wall of the settling section.

[0052] However, it is understood in the art that since the silicon particle feed pipe is provided on the side wall of the settling section, its feeding (especially horizontal transverse feeding) will still impact the side wall of the settling section 11, which will not only cause the silicon particle feed to be crushed, but also easily lead to an increase in the impurity content of the product.

[0053] In one embodiment, the lower diameter of the settling section 11 is larger than the upper diameter of the conical reaction section 14 and is flush with the upper end of the conical reaction section 14. The lower end of the settling section 11 is connected to the upper end of the conical reaction section 14 via a horizontally arranged ring 10, wherein the outer ring of the ring 10 connects to the lower end of the settling section 11, and the inner ring of the ring 10 connects to the upper end of the conical reaction section 14, thereby forming an annular platform at the bottom of the settling section 11 that supports a silicon particle layer. The silicon particle layer accumulated on this platform can then be used to block silicon particles fed from the silicon particle feed pipe 12 from impacting the reaction. The impact on the wall of the settling section of the reactor; the study found that, due to its location in the settling section 11, this arrangement is conducive to the natural settling and accumulation of silicon particles on the annular platform and does not lead to the expected natural downward movement by gravity; in addition, due to the impact of the gas-solid mixture introduced by the silicon particle feed pipe 12 and the particle deposition in the settling section 11, the accumulated silicon particle layer can, on the one hand, effectively prevent the feed from directly impacting the inner wall of the reactor while realizing transverse feeding, and on the other hand, the accumulated silicon particles can achieve a dynamic balance between the particle reduction caused by the transverse feed airflow impact and the particle deposition in the settling section 11, thus achieving a balance between a certain material replacement and continuous protection.

[0054] In one embodiment, the solid product outlet pipe 16 is L-shaped, including a vertically arranged sealing section 17 and a conveying section 18 connected to the lower end of the sealing section 17. The upper end of the sealing section 17 is directly connected to the bottom of the conical reaction section 14, allowing the silicon particles grown after leaving the conical reaction section 14 to directly enter the sealing section 17 of the solid product outlet pipe 16, thereby reducing resistance and facilitating the conveying of the product descending from the solid product outlet pipe. Of course, it will be understood in the art that the "L" shape of the solid product outlet pipe 16 does not imply a limitation on the sealing section 17 and the... The conveying sections 18 are connected at strict right angles or the material sealing section 17 and the conveying section 18 are connected at a strict length ratio. In this utility model, the "L" shape mainly refers to the bent design of the solid product outlet pipe 16. For example, the material sealing section 17 and the conveying section 18 can be connected by an arc-shaped bend, and the included angle between the material sealing section 17 and the conveying section 18 does not have to be 90°. It is understood in the art that the conveying section can also be set to tilt downwards for conveying. For example, the included angle between the conveying section 18 and the material sealing section 17 can be 90-150°, such as 100, 120, 140° or 110-130°.

[0055] In one embodiment, the material sealing section 17 is further provided with a conveying air duct 19, which is horizontally connected to the lower part of the material sealing section 17, for example, at a position 2D to 5D, such as 3D or 4D (D is the inner diameter of the pipe in the conveying section). Studies have found that the coordinated arrangement of the conveying air duct 19 and the material sealing section 17 can better facilitate the conveying of solid materials. The material sealing section 17 can form a material seal of a certain height, and the conveying air horizontally delivered by the conveying air duct 19, being perpendicular to the material sealing section, can appropriately increase the particle gap in the material sealing section, reduce the internal friction between particles, and play a role in loosening the material. The material sealing section 17 can also effectively prevent the airflow from rising into the conical reaction section 14. Finally, the conveying air flows downward to transport the product, which is also conducive to the rapid conveying of solid materials in the conveying section 18, so as to better match the rapid movement of particles in the reactor.

[0056] In addition, a feed pipe can be provided at an appropriate location in the conical polycrystalline silicon reactor to add the fine seed crystals (the amount added per unit time is very small and has little impact) to maintain the bed in the reactor, for example, it can be set in the settling section or on the silicon particle feed pipe.

[0057] The process for preparing granular polycrystalline silicon using the polycrystalline silicon preparation system of this invention includes:

[0058] (1) The silicon-containing raw material gas fed into the silicon-containing raw material gas inlet pipe and the high-temperature silicon particles fed into the silicon particle inlet pipe are contacted and reacted in the polycrystalline silicon reactor so that the silicon produced by the decomposition of the silicon-containing raw material gas is deposited and grown on the surface of the silicon particles used as seed crystals.

[0059] (2) The grown silicon particles are fed from the solid product outlet pipe into the circulating riser pipe, and the exhaust gas is discharged from the exhaust pipe.

[0060] (3) Hot air heated by the heater is sent from the hot air pipe into the circulating riser pipe, and the grown silicon particles are classified by airflow. The smaller particles are heated to a temperature sufficient to decompose the silicon-containing raw material gas and sent upward as the high-temperature silicon particles into the silicon particle feed pipe. The remaining larger particles are discharged downward as polycrystalline silicon products.

[0061] In this invention, the silicon-containing raw material gas can be a mixture of silicon-containing effective gas and dilution gas. The silicon-containing effective gas is a gas that can decompose to produce silicon when heated, and is well known in the art, such as silane or ethylsilane. The dilution gas can be hydrogen, nitrogen, helium, or argon (it is understood in the art that it can also be used as a gas for transporting silicon particles). For example, the silicon-containing raw material gas can be a mixture of silane and hydrogen, wherein the volume content of silane can be 5-100%, such as 20%, 40%, 60%, or 80%, preferably 50-100%. It is understood in the art that when the silane content is 100%, the silicon-containing raw material gas is pure silane gas rather than a mixture.

[0062] In this invention, the temperature of the silicon particle bed can be 650-850°C, such as 700, 750 or 800°C, to allow the reaction to proceed; it is understood in the art that the temperature of the hot air should be even higher to be sufficient to heat the silicon particles to the required temperature.

[0063] In this invention, the pressure inside the reactor can be 0.5-3 MPa.g, such as 1 or 2 MPa.g.

[0064] In this invention, the hourly circulation ratio of the silicon particles in the polycrystalline silicon reactor (i.e., the ratio of the amount of silicon particles fed into the silicon particle feed pipe 12 per hour to the amount of silicon particles stored in the polycrystalline silicon reactor) can be 5-20, such as 8, 10 or 15. It is understood in the art that too low an hourly circulation ratio may be detrimental to preventing particle agglomeration, while too high an hourly circulation ratio may cause wear and tear on the system equipment and affect the purity of the product.

[0065] In this invention, the silicon particles in the polycrystalline silicon reactor serve both as seed crystals to provide a deposition surface and as a heating medium to heat the feed gas. Preferably, the mass ratio of the silicon-containing feed gas to the silicon particles fed through the silicon particle inlet pipe 12 is (0.05-0.25):1, such as 0.1:1, 0.15:1, or 0.2:1. It is understood in the art that a ratio that is too low may result in low yield and high cost, while a ratio that is too high may result in a decrease in conversion rate.

[0066] The present invention will be further illustrated below with reference to specific operational embodiments / comparative examples.

[0067] Example 1

[0068] like Figure 1 As shown, the polycrystalline silicon preparation system of this invention includes a polycrystalline silicon reactor 1, a circulating riser 2, a heater 3, a buffer tank 4, and a cooler 5; wherein, the polycrystalline silicon reactor 1 is a conical polycrystalline silicon reactor, as shown in the figure. Figure 3 As shown, it includes the conical reaction section 14 (cone angle 20°) and the settling section 11 connected thereto; the top of the settling section is provided with an exhaust pipe 13 and the side wall is provided with a silicon particle feed pipe 12 for gas transportation as a seed crystal; the upper end of the conical reaction section is connected to the lower end of the settling section, and the bottom of the conical reaction section is provided with a solid product outlet pipe 16 and a silicon-containing raw material gas inlet pipe 15 on the side wall.

[0069] The outlet of the silicon-containing raw material gas inlet pipe 15 extends radially close to the radial center of the conical reaction section, and the distance between it and its central axis is 1 / 2R; and four silicon-containing raw material gas inlet pipes are evenly distributed circumferentially along the conical reaction section on the same plane, with their height at 1 / 3 of the height of the conical reaction section from bottom to top.

[0070] A horizontal ring 10 is provided at the lower end of the settling section. The outer ring of the ring is connected to the lower end of the settling section, and the inner ring of the ring is connected to the upper end of the conical reaction section, thereby forming an annular platform at the bottom of the settling section to support the silicon particle layer and block the feeding impact of the silicon particle feed pipe.

[0071] The solid product outlet pipe 16 is L-shaped and includes a vertically arranged material sealing section 17 and a conveying section 18 horizontally connected to the lower end of the material sealing section. The upper end of the material sealing section is directly connected to the bottom of the conical reaction section, and the horizontally connected conveying air pipe 19 is connected to the lower part of the material sealing section at a position higher than the conveying section 3D.

[0072] The other end of the conveying section is connected to the middle of the vertically arranged circulating lifting pipe, and the upper end of the circulating lifting pipe is connected to the silicon particle feed pipe. Hot air (hydrogen) heated by the heater enters from the lower part of the circulating lifting pipe through the hot air pipe. The circulating lifting pipe has a variable diameter section at the connection with the solid product outlet pipe, and two variable diameter sections are provided on the section of the circulating lifting pipe between the hot air pipe and the solid product outlet pipe.

[0073] In addition, a feed pipe is provided at an appropriate location in the polycrystalline silicon reactor 1 to add fine seed crystals (the amount added per unit time is very small and has little impact) to maintain the bed in the reactor. For example, it is set in the settling section or at the position of the circulating riser between the conveying section and the silicon particle feed pipe.

[0074] During operation, (1) the silicon particles in the gas-solid mixture fed from the silicon particle inlet pipe are separated by sedimentation in the sedimentation section, so that the silicon particles settle into the conical reaction section to form a silicon particle bed; (2) the silicon-containing raw material gas (100% silane) fed from the silicon-containing raw material gas inlet pipe rises and reacts with the descending silicon particle bed, so that the silicon produced by the decomposition of the silicon-containing raw material gas is deposited and grown on the surface of the silicon particles used as seed crystals to obtain granular polycrystalline silicon; (3) the grown silicon particles are fed from the solid product outlet pipe into the... (3) The circulating riser pipe is used to discharge exhaust gas from the exhaust pipe; (4) Hot air (850°C) heated by the heater is sent into the circulating riser pipe from the hot air pipe, and the grown silicon particles are classified by airflow. The smaller particles are heated to a temperature sufficient to decompose the silicon-containing raw material gas and sent upward as the high-temperature silicon particles into the silicon particle feed pipe. The remaining larger particles are discharged downward as polycrystalline silicon products; (6) The discharged polycrystalline silicon products are sent downward into the buffer tank for buffering, and then from the buffer tank into the cooler for cooling.

[0075] The reactor pressure is approximately 5 bar.g, the average temperature of the silicon particle bed is approximately 700°C, the mass ratio of silicon-containing raw material gas to silicon particle feed entering from the silicon particle inlet pipe is approximately 0.15:1, the silicon particle circulation ratio is approximately 17.5, and the raw material gas inlet temperature is 250°C.

[0076] Reaction results: Silane conversion rate 100%, exhaust gas dust content (ratio to product weight) 0.03% wt, and the apparent density of the silicon particles in the product was measured to be 2.05 g / cm³. 3 Hydrogen content was not detected, the product had a complete crystal form and a dense structure; the lining of the settling section was intact with no wear, there was no deposit on the reactor wall, and the product showed no agglomeration.

[0077] Example 2

[0078] The difference from Example 1 is that the conical polycrystalline silicon reactor is replaced with a fluidized bed reactor. Everything else is the same as in Example 1.

[0079] Reaction results description: Due to the use of circulating riser heating, there was no obvious deposition on the inner wall of the reactor after operation. However, due to the presence of bubbles in the reactor, a large amount of fine powder still existed in the exhaust gas.

[0080] Example 3

[0081] The difference from Embodiment 1 is that the circulating feed pipe does not have a diameter reducing section. Everything else is the same as in Embodiment 1.

[0082] The reaction results showed that the content of fine particles (particle size less than 1 mm) in the polycrystalline silicon product increased by 3 wt% compared to Example 1.

[0083] Example 4

[0084] The difference from Example 1 is as follows: the cone angle of the reaction section is 40°; the distance between the outlet of the conical reaction section at 1 / 5 of its height from bottom to top and the central axis is 1 / 4R; the silane content of the inlet gas is 50% (the silicon-containing raw material gas is 50 vol% silane + 50 vol% hydrogen). The rest is the same as in Example 1.

[0085] Reaction results: Silane conversion rate 100%, exhaust gas dust content (ratio to product weight) 0.05% wt, and the apparent density of the silicon particles in the product was measured to be 2.04 g / cm³. 3 Hydrogen content was not detected, the lining of the settling section was intact with no wear, there was no sediment on the reactor wall, and the product showed no agglomeration.

[0086] Example 5

[0087] The difference from Example 1 is that the annular ring 10 used to form the annular platform in the reactor is replaced with a frustum-shaped transition section with a larger diameter at the top and a smaller diameter at the bottom, and a sidewall inclined at 45°. The upper end of this transition section is connected to the lower end of the settling section 11, and the upper end is connected to the upper end of the conical reaction section 14. The rest is the same as in Example 1.

[0088] Description of reaction results: Compared with Example 1, obvious scratches appeared on the lining on the side opposite to the inlet of the solid-gas mixture in the settling section after long-term operation, and the lining material component was detected in the silicon particle product; in addition, the exhaust gas dust content (ratio to product weight) was 0.05% wt.

[0089] Example 6

[0090] The difference from Example 1 is that the outlets of the four silicon-containing raw material gas inlet pipes are retracted to the inner wall of the conical reaction section. Everything else is the same as in Example 1.

[0091] Reaction results description: Compared with Example 1, the dust content in the exhaust gas (ratio to product weight) was higher, reaching 0.22% wt, and a small amount of deposition appeared on the reactor wall.

[0092] Example 7

[0093] The difference from Embodiment 1 is that the connection position of the conveying duct 19 is moved down to align with the conveying section 18, so that the material sealing section forms an inverted T-shaped connection with the conveying section and the conveying duct. The rest is the same as in Embodiment 1.

[0094] Description of reaction results: Compared with Example 1, due to the deterioration of the feeding effect, the hourly circulation ratio decreased to 5. Due to the decrease in circulation ratio, the number of hot silicon particles entering the reactor decreased significantly, the temperature inside the reactor began to decrease, and the conversion rate decreased. When the mass of the inlet gas was reduced to 20% of that in Example 1, the reactor temperature reached the required level and the conversion rate recovered to 100%, which had a significant impact on the overall output.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the lowest section of the conical reaction section 14 (i.e., the part of the conical reaction section below 1 / 6 of its height from bottom to top) is replaced with a conical head with a cone angle of 60°, and the solid product outlet pipe 16 is directly connected to the bottom of this head. The rest is the same as in Example 1.

[0097] Description of reaction results: Compared with Example 1, the particles were almost stationary at the point where the cone angle changed, the upper particles flowed slowly, and after running for a period of time, the particles agglomerated and gradually increased in size.

[0098] As can be seen from the above examples / comparative examples, (1) the present invention uses a circulating riser pipe instead of a reactor. Instead, it utilizes the characteristics of the circulating riser pipe, which has a large circulation capacity and high heat transfer intensity, to complete the classification, circulation and heating of silicon particles and reduce the deposition on the reactor wall. At the same time, the silicon particles are repeatedly heated by high-temperature hot air at higher temperatures, which is conducive to the complete breaking of silicon-hydrogen bonds, making the product crystal form complete and the structure dense.

[0099] (2) By setting a variable diameter section on the circulating riser, this utility model can enhance the particle classification and heat transfer effect; by using multiple variable diameter sections, the gas velocity of the hot gas can be continuously changed, silicon particles can be separated multiple times, the separation effect can be enhanced, and the heat transfer effect can be enhanced.

[0100] (3) The reaction section of the reactor of this utility model adopts an overall conical design and has no additional lower head design, resulting in a large change in cone angle. The wall of the entire reaction section is straighter, which is conducive to the rapid movement of particles in the reaction bed. Furthermore, the relative movement between particles during downward movement can effectively prevent particle agglomeration.

[0101] (4) By feeding the raw material gas into the reaction section radially to the middle, compared with feeding the gas near the inner wall of the reaction section, this utility model is more conducive to heat exchange and concentration of the reaction area in the reactor, resulting in a large product deposition area, a dense product structure, reduced fine powder generation, less tail gas entrainment, and also more conducive to reducing wall surface reaction.

[0102] (5) By setting a ring at the lower end of the settling section to form a ring platform, it is beneficial to improve product purity and reduce the entrainment of fine powder in the exhaust gas while reducing equipment wear.

[0103] (6) This utility model can cooperate with the material sealing section and the conveying section by conveying air pipe at the bottom of the material sealing section, which is conducive to the rapid conveying of solid materials in the conveying section, so as to better cooperate with the rapid movement of particles in the reactor, which is conducive to improving the circulation ratio and increasing the output.

Claims

1. A rapid-cycle polycrystalline silicon fabrication system, characterized in that, The polycrystalline silicon fabrication system includes: A polycrystalline silicon reactor is provided with an exhaust pipe and a silicon particle feed pipe for inputting high-temperature silicon particles at the top, and a solid product outlet pipe and a silicon-containing raw material gas inlet pipe for introducing silicon-containing raw material gas at the bottom. The polycrystalline silicon reactor is used to contact and react the silicon-containing raw material gas with high-temperature silicon particles as seed crystals, so that silicon generated from the decomposition of the silicon-containing raw material gas is deposited and grown on the surface of the silicon particles. The grown silicon particles are discharged from the solid product outlet pipe and the tail gas after reaction is discharged from the exhaust pipe. A circulating riser is provided, which is arranged longitudinally. The other end of the solid product outlet pipe is connected to the middle of the circulating riser to feed the grown silicon particles discharged from the polycrystalline silicon reactor into the circulating riser. The upper end of the circulating riser is directly or indirectly connected to the silicon particle feed pipe, and the lower part of the circulating riser is connected to a hot air pipe for sending hot air into the circulating riser to classify the grown silicon particles. The sorted particles are heated to a temperature sufficient to decompose the silicon-containing raw material gas and fed upward into the silicon particle feed pipe as high-temperature silicon particles. The remaining particles are discharged downward as polycrystalline silicon products. A heater is used to heat the airflow entering the hot air duct to obtain the hot air.

2. The rapid cycling polycrystalline silicon fabrication system according to claim 1, characterized in that, The circulating riser pipe has one or more diameter-enlarging variable sections at the connection point with the solid product outlet pipe and on the section of the circulating riser pipe located between the hot air pipe and the solid product outlet pipe.

3. The rapid cycling polycrystalline silicon fabrication system according to claim 2, characterized in that, The polycrystalline silicon fabrication system also includes: A buffer tank, connected to the lower end of the circulating riser, is used to buffer the polysilicon product discharged from the circulating riser. A cooler, connected to the buffer tank, is used to cool the polysilicon product discharged from the buffer tank.

4. The rapid cycling polycrystalline silicon fabrication system according to claim 3, characterized in that, The cooler includes a housing, and a gas distributor is provided at the lower part of the housing, thereby dividing the interior of the housing into an air intake zone located below the gas distributor and a cooling zone located above the gas distributor. The top of the cooling zone is provided with a polysilicon product feed pipe that extends downward into the cooling zone, for feeding polysilicon products into the cooling zone and accumulating them on the gas distributor to form a polysilicon product bed. The air intake zone is provided with a cooling gas inlet to introduce cooling gas to cool the polycrystalline silicon products accumulated on the gas distributor; the cooling zone is provided with a cooling gas outlet, which is higher than the lower end of the polycrystalline silicon product feed pipe to discharge the cooling gas that has been heated by heat exchange with the polycrystalline silicon product. The gas distributor is equipped with a polysilicon product discharge pipe. The cooler is used to cool the polysilicon products piled on the gas distributor by using the rising cooling gas introduced from the gas inlet area, and to discharge the cooled polysilicon products from the bottom of the polysilicon product bed through the polysilicon product discharge pipe. The polycrystalline silicon preparation system also includes a pressure-bearing shell, which houses the polycrystalline silicon reactor, circulation riser, buffer tank, and cooler.

5. The rapid cycling polycrystalline silicon fabrication system according to claim 4, characterized in that, The polycrystalline silicon fabrication system also includes: The exhaust gas heat exchange unit is used to cool the exhaust gas from the exhaust pipe of the polycrystalline silicon reactor using circulating gas to recover heat, and to send the heated circulating gas into the heater for further heating, so as to be sent into the circulating riser pipe as hot air circulation. The exhaust gas dust removal unit is used to remove dust from the exhaust gas from the exhaust gas heat exchange unit to obtain dust-removed exhaust gas. A circulating gas compressor is used to pressurize the dust removal exhaust gas so that it can be sent into the exhaust gas heat exchange unit as circulating gas. Product tank, used to receive polysilicon products discharged from the polysilicon preparation system; The seed crystal preparation unit is used to crush the polycrystalline silicon product discharged from the polycrystalline silicon preparation system and send it back to the polycrystalline silicon reactor as a seed crystal. The first cooling pipe is connected to the cooling gas inlet of the cooler and is used to send cooling gas into the cooler to cool the incoming polycrystalline silicon product. The second cooling pipe is connected to the cooling gas outlet of the cooler and the exhaust gas dust removal unit, respectively, and is used to send the heated cooling gas from the cooler as part of the exhaust gas into the exhaust gas dust removal unit.

6. The rapid cycling polycrystalline silicon fabrication system according to claim 1, characterized in that, The polycrystalline silicon reactor is a fluidized bed reactor or a moving bed reactor; the gas-solid mixture sent from the upper end of the circulating riser directly enters the silicon particle feed pipe and then undergoes gas-solid separation in the upper part of the polycrystalline silicon reactor, or gas-solid separation is performed first and then the mixture enters the silicon particle feed pipe.

7. The rapid cycling polycrystalline silicon fabrication system according to any one of claims 1-6, characterized in that, The polycrystalline silicon reactor is a conical polycrystalline silicon reactor, comprising a conical reaction section whose diameter gradually decreases from top to bottom and a settling section disposed above the conical reaction section; The settling section is provided with an exhaust pipe at the top and a silicon particle feed pipe on the side wall; the settling section is used to separate silicon particles from the gas-solid mixture from the silicon particle feed pipe, so that the silicon particles settle into the conical reaction section to form a silicon particle bed. The upper end of the conical reaction section is connected to the lower end of the settling section. The bottom of the conical reaction section is provided with the solid product outlet pipe, and the side wall is provided with the silicon-containing raw material gas inlet pipe. The conical reaction section is used to make the rising silicon-containing raw material gas contact and react with the descending silicon particle bed, so that the silicon produced by the decomposition of the silicon-containing raw material gas introduced from the silicon-containing raw material gas inlet pipe is deposited and grown on the surface of the silicon particles that serve as seed crystals, and the grown silicon particles are discharged from the solid product outlet pipe.

8. The rapid cycling polycrystalline silicon fabrication system according to claim 7, characterized in that, The outlet of the silicon-containing feed gas inlet pipe extends radially close to the radial center of the conical reaction section.

9. The rapid cycling polycrystalline silicon fabrication system according to claim 8, characterized in that, The solid product outlet pipe is L-shaped and includes a vertically arranged material sealing section and a conveying section connected to the lower end of the material sealing section. The upper end of the material sealing section is directly connected to the bottom of the conical reaction section, and the other end of the conveying section is connected to the middle of the circulation riser pipe to send the grown silicon particles discharged from the conical reaction section into the circulation riser pipe. The material sealing section is also equipped with a conveying air duct, which is horizontally connected to the lower part of the material sealing section.

10. The rapid cycling polycrystalline silicon fabrication system according to claim 9, characterized in that, The lower end of the settling section has a larger diameter than the upper end of the conical reaction section and is flush with the upper end of the conical reaction section. The lower end of the settling section is connected to the upper end of the conical reaction section by a horizontally arranged ring, wherein the outer ring of the ring is connected to the lower end of the settling section and the inner ring of the ring is connected to the upper end of the conical reaction section, thereby forming an annular platform at the bottom of the settling section to support the silicon particle layer and to block the impact of silicon particles fed from the silicon particle feed pipe on the reactor wall.

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