Cone-shaped polycrystalline silicon reactor capable of rapidly moving particles

Abstract

The utility model discloses a conical polycrystalline silicon reactor capable of rapidly moving particles. The conical polycrystalline silicon reactor comprises a conical reaction section and a settling section, wherein the diameter of the conical reaction section is gradually reduced from top to bottom; the settling section is arranged above the conical reaction section; the top of the settling section is provided with an exhaust pipe, and the side wall of the settling section is provided with a silicon particle feeding pipe which is used for conveying gas and is used as a seed crystal; the upper end of the conical reaction section is communicated with the lower end of the settling section, a solid product outlet pipe is arranged at the bottom of the conical reaction section, and a silicon-containing raw material gas inlet pipe is arranged on the side wall of the conical reaction section; the reaction section of the reactor is conical, silicon particles are high in moving speed, reaction efficiency is high, silane completely reacts, product crystal forms are complete, hydrogen is not contained, product density is high, yield is high, energy consumption is low, amplification is easy, meanwhile, side face feeding and top exhaust design of the settling section are matched, tail gas entrainment is small, tail gas dust is not generated, and product quality is good.

Description

A cone-shaped polycrystalline silicon reactor with rapid particle movement Technical Field

[0001] This utility model relates to the field of polycrystalline silicon production technology, and in particular to a conical polycrystalline silicon reactor with rapidly moving particles. Background Technology

[0002] High-purity polycrystalline silicon has always been a fundamental raw material for the semiconductor and photovoltaic industries, leading to the rapid development of the polycrystalline silicon industry. 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] 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. However, due to design issues with its heating and feeding methods, it is prone to uneven bed temperature, incomplete silane reaction, and powder entrainment in the tail gas. To address this, a filter element is installed at the reactor tail gas outlet, increasing 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.

[0007] CN103787336A discloses a method for producing high-purity granular silicon, which requires the addition of an auxiliary gas to maintain the bed state. However, the addition of the 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, the particles in the bed itself move slowly and have poor heat transfer efficiency, 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 prone to producing fine powder. Therefore, a surface treatment mechanism is added, making the system even more complicated. Summary of the Invention

[0008] In view of this, the purpose of this utility model is to provide a cone-shaped polycrystalline silicon reactor with rapid particle movement for efficient preparation of granular polycrystalline silicon.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A conical polycrystalline silicon reactor with rapidly moving particles, characterized in that:

[0011] The conical polycrystalline silicon reactor includes a conical reaction section whose diameter gradually decreases from top to bottom and a settling section disposed above the conical reaction section;

[0012] The settling section is equipped with an exhaust pipe at the top and a gas-feeding pipe for transporting silicon particles as seed crystals 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.

[0013] 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 a solid product outlet pipe, and the side wall is provided with a 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 as seed crystals, and the obtained granular polycrystalline silicon is discharged from the solid product outlet pipe.

[0014] Preferably, the outlet of the silicon-containing raw material gas inlet pipe extends radially close to the radial center of the conical reaction section.

[0015] Preferably, the distance between the outlet of the silicon-containing raw material gas inlet pipe and the central axis of the conical reaction section is (1 / 10-2 / 3)R, more preferably (1 / 8-1 / 2)R; 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.

[0016] Preferably, the silicon-containing raw material gas inlet pipe is provided in one group or multiple groups located at different heights, and each group includes multiple silicon-containing raw material gas inlet pipes that are evenly distributed circumferentially along the conical reaction section on the same plane.

[0017] Preferably, the outlet of the silicon-containing raw material gas inlet pipe is located at 1 / 6-2 / 3 of the height from bottom to top of the conical reaction section, more preferably at 1 / 5-1 / 2 of the height.

[0018] Preferably, the solid product outlet pipe is L-shaped, including a vertically arranged material sealing section and a conveying section connected to the lower end of the material sealing section, wherein the upper end of the material sealing section is directly connected to the bottom of the conical reaction section to convey the solid product descending from the conical reaction section.

[0019] Preferably, the angle between the conveying section and the material sealing section is 90-150°, more preferably 110-130°.

[0020] Preferably, the material sealing section is further provided with a conveying air duct, which is horizontally connected to the lower part of the material sealing section, for example, at a position 2D-5D higher than the conveying section (D is the inner diameter of the pipe in the conveying section).

[0021] Preferably, the cone angle of the conical reaction section is 15-50°, more preferably 20-40°; the conical reaction section of this invention is an integral cone shape, and the cone angle remains unchanged from top to bottom.

[0022] Preferably, the lower end diameter of the settling section is larger than the upper end diameter 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, which is used to block the impact of silicon particles fed from the silicon particle feed pipe on the reactor wall.

[0023] Preferably, the silicon particle feed pipe is horizontally positioned toward the central axis of the settling section.

[0024] Preferably, the conical polycrystalline silicon reactor further includes a heating section for heating the silicon particles in the gas-solid mixture to be fed into the settling section so that they can react in the conical reaction section.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) This invention directly heats the particles outside the reactor, so that the silicon-containing raw material gas is heated on the particles, which greatly increases the heating area and greatly improves the wall deposition problem and the lining damage problem, enabling long-term operation; 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.

[0027] (2) The reaction section adopts an integral conical design, which is conducive to the rapid movement of particles in the reaction bed, and the relative movement between particles during downward movement can effectively prevent particle agglomeration.

[0028] (3) The reaction section of this utility model can be introduced without additional auxiliary gas and the conical design is conducive to gas reaction expansion and diffusion, which helps to prevent the generation of bubbles in the reactor, thereby avoiding the occurrence of homogeneous reaction, greatly reducing dust generation and improving product yield; and since there are no bubbles, silane can react 100% and there is no silane in the tail gas, which helps to reduce the tail gas separation process in subsequent sections.

[0029] (4) By feeding the raw material gas to the radial center of the reaction section, this utility model is beneficial to heat exchange and concentration of the reaction area in the reactor, resulting in a large product deposition area and a dense product structure. It also helps to reduce wall deposition.

[0030] (5) By setting a ring at the lower end of the settling section to form an annular platform, this utility model can effectively prevent the feed from directly impacting the inner wall of the reactor while realizing transverse feeding. At the same time, the accumulated silicon particles can achieve a dynamic balance between the particle slippage caused by the transverse feeding impact and the silicon particles brought in by the feed airflow and the particles in the settling section deposited here.

[0031] (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 material in the conveying section, so as to better cooperate with the rapid movement of particles in the reactor.

[0032] 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

[0033] Figure 1 is a schematic diagram of one embodiment of the conical polycrystalline silicon reactor of this utility model. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] As shown in Figure 1, the conical polycrystalline silicon reactor of this invention 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.

[0038] 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 as seed crystals, and the obtained granular polycrystalline silicon is discharged from the solid product outlet pipe 16.

[0039] 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.

[0040] 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.

[0041] 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°.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In this invention, the silicon particles in the conical reaction section 14 descend and are then discharged from the solid product outlet pipe 16. It is understood in the art that the discharged solid product can be subsequently graded, in which silicon particles that do not meet the size requirements will be separated and, for example, recycled back to the reactor through the silicon particle inlet to continue growth.

[0049] 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, so that the solid product leaving the conical reaction section 14 directly enters the sealing section 17 of the solid product outlet pipe 16, thereby reducing resistance and facilitating the conveying of the solid product descending from the solid product outlet. 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 conveying section 18. The conveying sections 18 are connected at a strict right angle 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°.

[0050] 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 solid products, 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.

[0051] In this invention, the conical polycrystalline silicon reactor may further include a heating section (not shown in the figure) for heating the silicon particles in the gas-solid mixture fed into the settling section 11 so that they can react in the conical reaction section 14; wherein the heating section may operate by hot gas heating / electric heating / radiation heating / electromagnetic heating, etc.

[0052] In addition, a feed pipe can be provided at an appropriate location in the conical polycrystalline silicon reactor 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 can be set in the settling section or on the silicon particle feed pipe.

[0053] When preparing granular polycrystalline silicon using the conical polycrystalline silicon reactor of this invention:

[0054] (1) The silicon particles in the gas-solid mixture fed from the silicon particle inlet pipe 12 are separated by sedimentation in the sedimentation section 11 so that the silicon particles settle into the conical reaction section 14 to form a silicon particle bed.

[0055] (2) The silicon-containing raw material gas fed into the silicon-containing raw material gas inlet pipe 15 rises and reacts with the downward 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 as seed crystals to obtain granular polycrystalline silicon.

[0056] (3) The obtained granular polycrystalline silicon is discharged from the solid product outlet pipe 16 and the exhaust gas is discharged from the exhaust pipe 13. The exhaust gas is the gas that rises from the conical reaction section 14 into the settling section 11 and the gas from the gas-solid mixture.

[0057] 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.

[0058] In this invention, the temperature of the silicon particle bed can be 650-850℃, such as 700, 750 or 800℃, to allow the reaction to proceed.

[0059] In this invention, the pressure inside the reactor can be 0.5-3 MPa.g, such as 1 or 2 MPa.g.

[0060] In this invention, the hourly circulation ratio of the silicon particles in the conical reaction section 14 (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 silicon particle bed in the conical reaction section) 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 a ratio may cause wear and tear on the system equipment and affect the purity of the product.

[0061] In this invention, the silicon particle bed in the conical reaction section 14 serves both as a seed crystal 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 particle feed entering from 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 too low a ratio may result in low yield and high cost, while too high a ratio may result in a decrease in conversion rate.

[0062] The present invention will be further illustrated below with reference to specific operational embodiments / comparative examples.

[0063] Example 1

[0064] The conical polycrystalline silicon reactor used is shown in Figure 1, including 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 seed crystals; 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.

[0065] The outlet of the silicon-containing raw material gas inlet pipe 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.

[0066] 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.

[0067] 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.

[0068] The other end of the conveying section is connected to the middle of a vertically arranged heating circulation pipe (not shown in the figure). The upper end of the heating circulation pipe is connected to the silicon particle feed pipe. Hot air (hydrogen) heated by the heating unit enters through the lower part of the heating circulation pipe. Small particles from the solid product from the conveying section 18 are pneumatically separated and heated together with silicon particles from the feed pipe, and then fed upward into the silicon particle feed pipe. In addition, a feed pipe is also provided at an appropriate position in the reactor 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 heating circulation pipe between the conveying section and the silicon particle feed pipe.

[0069] 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 as seed crystals to obtain granular polycrystalline silicon; (3) the granular polycrystalline silicon obtained is discharged from the solid product outlet pipe and the tail gas is discharged from the exhaust port.

[0070] 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.

[0071] Reaction results: Silane conversion rate 100%, exhaust gas dust content (ratio to product weight) 0.03% wt, and the apparent density of silicon particles in the product measured to be 2.05 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.

[0072] Example 2

[0073] 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.

[0074] 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. 3Hydrogen 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.

[0075] Example 3

[0076] 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.

[0077] 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.

[0078] Example 4

[0079] 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.

[0080] 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.

[0081] Example 5

[0082] 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.

[0083] 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.

[0084] Comparative Example 1

[0085] 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.

[0086] 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.

[0087] As can be seen from the above examples / comparative examples, (1) 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 entire reaction section wall 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.

[0088] (2) 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 larger product deposition area, a denser product structure, reduced fine powder generation, less tail gas entrainment, and also more conducive to reducing wall surface reaction.

[0089] (3) 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.

[0090] (4) 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 material 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 cone-shaped polycrystalline silicon reactor for rapid particle movement, characterized in that: The conical polycrystalline silicon reactor includes a conical reaction section with a gradually decreasing diameter from top to bottom and a settling section located above the conical reaction section. The settling section has an exhaust pipe at its top and a gas feed pipe for transporting silicon particles as seed crystals on its sidewall. The settling section separates silicon particles from the gas-solid mixture from the silicon particle feed pipe, allowing the silicon particles to settle into the conical reaction section and form a silicon particle bed. 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 has a solid product outlet pipe and a silicon-containing raw material gas inlet pipe on its sidewall. The conical reaction section allows the rising silicon-containing raw material gas to contact and react with the descending silicon particle bed, causing silicon produced by the decomposition of the silicon-containing raw material gas introduced from the silicon-containing raw material gas inlet pipe to deposit and grow on the surface of the seed silicon particles, and the resulting granular polycrystalline silicon is discharged from the solid product outlet pipe.

2. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 1, 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 to convey the solid product descending from the conical reaction section.

3. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 2, characterized in that, 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.

4. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to any one of claims 1-3, 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.

5. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 4, characterized in that, The distance between the outlet of the silicon-containing raw material gas inlet pipe and the central axis of the conical reaction section is (1 / 10-2 / 3)R, 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.

6. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 5, characterized in that, The silicon-containing raw material gas inlet pipe is provided in one set or multiple sets at different heights, and each set contains multiple silicon-containing raw material gas inlet pipes that are evenly distributed circumferentially along the conical reaction section on the same plane.

7. The conical polycrystalline silicon reactor with rapidly moving particles according to any one of claims 1-3 and 5-6, 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.

8. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 7, characterized in that, The silicon particle feed pipe is horizontally positioned towards the central axis of the settling section.

9. The conical polycrystalline silicon reactor with rapid particle movement according to any one of claims 1-3, 5-6 and 8, characterized in that, The conical polycrystalline silicon reactor also includes a heating section for heating the silicon particles in the gas-solid mixture to be fed into the settling section so that they can react in the conical reaction section.

10. The cone-shaped polycrystalline silicon reactor with rapidly moving particles according to claim 9, characterized in that, The cone angle of the conical reaction section is 15-50°.

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