A moving bed reactor apparatus for producing particulate silicon

Abstract

The utility model discloses a kind of mobile bed reactor devices of production granular silicon, including the reactor and filter of interconnection;Reactor top end is equipped with silane gas import and hydrogen import, bottom end is equipped with product export, lateral middle section is equipped with heating device;The lateral side of reactor above heating device is equipped with seed crystal import;Filter lateral side bottom is equipped with granular silicon import, and granular silicon import is communicated with the bottom of reactor lateral side;Filter lateral side top is equipped with granular silicon export, and granular silicon export is in reactor and located above or below heating device;Filter bottom end is equipped with auxiliary carrier gas gas import, and lateral side is equipped with tail gas export.The utility model can effectively utilize the silicon powder microparticle generated in reactor, reduce the phenomenon of silicon deposition device wall, realize the efficient and continuous production of high-purity granular silicon with uniform morphology and size.

Description

Technical Field

[0001] This utility model relates to the field of granular silicon production technology, specifically to a moving bed reactor device for producing granular silicon. Background Technology

[0002] As a core raw material for semiconductors and photovoltaic devices, the innovation of its preparation technology is crucial to the industry's development. In recent years, the modified Siemens process, metallurgical process, and fluidized bed process have become common preparation technologies. The modified Siemens process, with its more mature technology, is the main method for producing granular silicon. This method is based on the principle of chemical vapor deposition (CVD). Under high temperature conditions, trichlorosilane reacts with hydrogen gas at a specific temperature to undergo a reduction reaction, and the resulting silicon is gradually deposited on the surface of the silicon core to form rod-shaped silicon. However, this process has significant limitations: it adopts an intermittent operation mode, requiring periodic shutdowns for cooling to harvest silicon rods, and frequent reactor start-ups and shutdowns make it difficult to effectively recover and utilize heat.

[0003] Compared to the modified Siemens process, the fluidized bed method demonstrates significant advantages in chemical engineering applications. From a reaction engineering perspective, the fluidized bed method employs a continuous production mode, using fluidization technology to continuously deposit silicon-containing gases (such as silanes (SiH4) and chlorosilanes) on the surface of suspended seed particles. Within the fluidized bed reactor, the gas-solid two phases are in a highly turbulent state, greatly enhancing mass and heat transfer processes. The unique mixing characteristics of the fluidized bed ensure uniformity of temperature and concentration among particles, avoiding local overheating or reactant concentration gradients, thus improving the efficiency and quality of silicon deposition. In terms of heat transfer, the efficient contact between the gas and solid phases within the fluidized bed significantly increases the heat transfer coefficient, allowing for more effective and timely removal of reaction heat compared to traditional fixed-bed reactors, thereby reducing energy consumption. It is worth noting that silicon powder particles are often generated during the production of granular silicon. These particles not only deposit on the inner wall of the reactor, affecting heat transfer, but also impact product quality. This can be caused by the gas introduced into the reactor blowing out undeposited silicon particles or by friction between already deposited granular silicon particles due to collisions. To address this issue, patent CN217511820U designs a special gas distributor, including inner and outer ring holes with different numbers, sizes, and diameters of pores on a disc. This concentrates the reactants in the middle of the fluidized bed reactor, reducing the concentration of reactants at the reactor wall, slowing down the rate of silicon deposition, and reducing silicon powder generation. This design alters the gas flow path and concentration distribution within the reactor, reducing the generation of silicon powder due to excessively vigorous local reactions. Patent CN205892763U incorporates a guide plate with flow-guiding holes and an auxiliary gas inlet in the enlarged section at the top of the fluidized bed reactor. The baffle plate directs the airflow towards the center, reducing the content of reactive gases near the vessel wall and minimizing deposition on the wall. An etchant gas is introduced through the auxiliary gas inlet, reacting with the silicon microparticles in the gas phase space through a hydrogenation reaction, converting the silicon microparticles into chlorosilane raw materials, thereby eliminating the harmful effects of silicon powder on the downstream system. Patent CN105460938B discloses a blocking element for a fluidized bed reactor. This element includes multiple receiving and connecting elements, disposed within the reactor and fixed to internal reactor components. When viewed vertically from the top, the area defined by its outer periphery occupies a portion of the horizontal cross-sectional area of ​​the chamber containing the element. The blocking element can interrupt the rising particle surge within the chamber, causing bubbles to break up and preventing large bubbles in the fluidized bed from carrying particles out of the reactor, thus reducing silicon powder generation and dispersion. These patents, through different methods, have to some extent optimized key issues faced by the fluidized bed method in the production of granular polycrystalline silicon, such as silicon formation control, temperature and concentration uniformity, equipment reliability, and product quality. However, they have not effectively solved the problem of reusing silicon powder particles. If silicon powder particles are directly discharged with the exhaust gas, it not only increases production costs but also causes environmental pollution. Therefore, effectively utilizing the silicon powder particles generated in the reactor is an urgent problem to be solved. Utility Model Content

[0004] To address the aforementioned technical problems and shortcomings in the field, this invention provides a moving bed reactor device for producing granular silicon. This device can effectively utilize the silicon powder particles generated in the reactor, reduce silicon deposition on the reactor walls, and achieve efficient and continuous production of high-purity granular silicon with uniform morphology and size.

[0005] The specific technical solution is as follows: A moving bed reactor apparatus for producing granular silicon includes a reactor and a filter connected to each other. The reactor has a silane gas inlet and a hydrogen gas inlet at the top, a product outlet at the bottom, and a heating device in the middle section of the side; a seed inlet is located on the side of the reactor above the heating device. A granular silicon inlet is located at the bottom side of the filter, which connects to the bottom side of the reactor; a granular silicon outlet is located at the top side of the filter, which is inside the reactor and located above or below the heating device; an auxiliary carrier gas inlet is located at the bottom of the filter, and a tail gas outlet is located on the side.

[0006] In the moving bed reactor apparatus for producing granular silicon, the granular silicon inlet of the filter is located above the auxiliary carrier gas inlet, and preferably the granular silicon inlet of the filter is located inside the reactor.

[0007] The moving bed reactor device for producing granular silicon in this invention uses a moving bed filter. The filter can form multiple longitudinally distributed regions, which can be divided into two types: granular silicon aggregation regions and silicon powder particle aggregation regions, with these two types of regions alternating in the longitudinal space. This partitioning design is based on particle classification and filtration separation. The granular silicon aggregation regions mainly rely on gravity settling and inter-particle interaction to use larger-diameter granular silicon as the filter filler material; the silicon powder particle aggregation regions, due to the filtration of larger-diameter granular silicon, allow the silicon powder particles in this region to aggregate and continue to grow. This partitioning method enables efficient separation of particles of different sizes, ensuring the purity and quality of the product.

[0008] The granular silicon inlet of the filter is located inside the reactor, above the auxiliary carrier gas inlet. The filter receives granular silicon and silicon powder particles from the reactor through the granular silicon inlet. The auxiliary carrier gas enters the filter through the auxiliary carrier gas inlet, carrying the granular silicon and silicon powder particles upwards. At a constant gas flow rate, particles of different sizes experience different drag forces and gravitational forces, resulting in different upward velocities. The filter utilizes the carrying effect of the airflow; larger granular silicon particles move upwards slowly, forming granular silicon aggregation areas, while smaller silicon powder particles move upwards quickly. These granular silicon aggregation areas efficiently capture the fine silicon powder particles during their ascent, preventing them from rising further, thus acting as a trapping mechanism. The trapped silicon powder particles aggregate to form silicon powder aggregation areas, creating an alternating distribution of granular silicon aggregation areas and silicon powder aggregation areas in the longitudinal space. The granular silicon outlet of the filter is located inside the reactor, and can be selected above or below the heating device depending on actual production needs. If located above the heating device, it is beneficial to collect granular silicon at a lower temperature, reducing the impact of high temperature on its performance; if located below the heating device, it can make full use of the residual heat of the heating device to promote further growth and aggregation of granular silicon.

[0009] The moving bed reactor device for producing granular silicon has a filter independently installed outside the reactor. From the perspective of equipment layout and maintenance, this facilitates the inspection and replacement of the filter, and allows for maintenance of the filter without affecting the operation of the main reactor, thus reducing the risk of production interruption.

[0010] In some embodiments, the moving bed reactor apparatus for producing granular silicon includes a heating device comprising one or more of a resistance heater, an induction heater, and a microwave heater. A resistance heater, based on Joule's law, generates heat by passing current through a resistor, thus heating the material inside the reactor. This heating method is simple and direct, suitable for applications where temperature uniformity requirements are not particularly high. An induction heater utilizes the principle of electromagnetic induction to generate an induced current in the material, thereby producing heat. It offers advantages such as rapid heating, high efficiency, and the ability to achieve localized heating. A microwave heater utilizes the interaction between microwaves and material molecules, causing the molecules to vibrate at high frequencies, thus achieving rapid heating. Its heating is selective, allowing for targeted heating based on the dielectric properties of the material.

[0011] In some embodiments, the moving bed reactor apparatus for producing granular silicon has a heating device located inside and / or outside the reactor. When the heating device is located inside the reactor, the material can be heated more directly, reducing heat loss during the transfer process; when the heating device is located outside the reactor, installation and maintenance are easier, and proper insulation design can ensure heating efficiency.

[0012] The moving bed reactor apparatus for producing granular silicon can change the gas flow rate at the auxiliary carrier gas inlet to blow granular silicon of different sizes into the filter. The auxiliary carrier gas inlet has the function of changing the gas flow rate; by adjusting the gas flow rate, the residence time and trajectory of the particles in the filter can be changed. When it is necessary to deposit granular silicon to a target size, the gas flow rate can be reduced, allowing the particles sufficient time to contact the reactant gas in the filter, thus achieving particle growth. Once the particles reach the target size, the gas flow rate is increased, blowing them into the reactor for separation and collection.

[0013] In some preferred embodiments, the moving bed reactor apparatus for producing granular silicon has an auxiliary carrier gas inlet smaller than the granular silicon inlet. According to the continuity equation, with a constant gas flow rate, a smaller inlet allows for a higher gas velocity. A higher gas velocity provides sufficient drag to blow granular silicon or silicon powder particles of different sizes into the filter, while ensuring good contact and mass transfer between the gas and the particles.

[0014] In some embodiments, the moving bed reactor apparatus for producing granular silicon has its exhaust gas outlet located on the upper or lower section of the side of the filter. If the exhaust gas outlet is located on the upper section of the filter, it is beneficial to discharge any fine particles that are not completely captured with the exhaust gas, thus preventing their accumulation in the reactor. If the exhaust gas outlet is located on the lower section of the filter, gravity can be used to allow some particles to settle before being discharged from the exhaust gas, thereby improving the purification level of the exhaust gas.

[0015] In some embodiments, the moving bed reactor device for producing granular silicon uses a filter made of one or more of the following materials: metal silicides, tungsten, niobium, tantalum, and alloys. The alloy contains one or more metallic elements selected from tungsten, niobium, and tantalum. These materials possess properties such as high temperature resistance, corrosion resistance, and good mechanical strength. This ensures the long-term stable operation of the filter in high-temperature, corrosive reaction environments.

[0016] In some preferred embodiments, the moving bed reactor apparatus for producing granular silicon has an exhaust gas outlet at the top of the reactor side.

[0017] Compared with the prior art, the advantages of this utility model are as follows: 1. Effectively avoids silicon deposition. By setting up a moving bed filter, the fine silicon powder in the reactor can be effectively reused, increasing production capacity while avoiding silicon deposition.

[0018] 2. High production capacity and low investment: The grown granular silicon seed crystals in the moving bed filter both continue to grow as seed crystals and serve as filler material within the filter to filter out granular silicon particles. No additional filler material is needed, enabling continuous production of granular silicon.

[0019] 3. The product has uniform size. By adjusting the airflow in the reactor, granular silicon can be deposited to the target size and then discharged. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the moving bed reactor device for producing granular silicon in a specific embodiment. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0022] See Figure 1 A moving bed reactor apparatus for producing granular silicon includes a reactor 1 and a filter 8 connected to each other. The reactor 1 has a silane gas inlet 2 and a hydrogen gas inlet 3 at its top, a product outlet 10 at its bottom, and a heating device 5 in the middle section of its internal side. The heating device 5 includes one or more of a resistance heater, an induction heater, and a microwave heater. A seed inlet 4 is located on the side of the reactor 1 above the heating device 5. A waste gas outlet 12 is located at the top side of the reactor 1. A granular silicon inlet 9 is located at the bottom side of the filter 8, connecting to the bottom side of the reactor 1. A granular silicon outlet 6 is located at the top side of the filter 8, inside the reactor 1 and above the heating device 5. An auxiliary carrier gas inlet 11 is located at the bottom of the filter 8, and a tail gas outlet 7 is located on its side. The auxiliary carrier gas inlet 11 is smaller than the granular silicon inlet 9. The tail gas outlet 7 is located in the lower section of the side of the filter 8. The filter 8 is made of one or more of a metal silicide, tungsten, niobium, tantalum, or an alloy, wherein the alloy contains one or more of the metallic elements tungsten, niobium, and tantalum.

[0023] The following is a specific operational example of the moving bed reactor device for producing granular silicon: Reactor 1 is preheated to 800-1200℃. Then, silane gas (trichlorosilane) and hydrogen gas are introduced into reactor 1 through silane gas inlet 2 and hydrogen gas inlet 3, respectively. Seed crystals are added to reactor 1 through seed crystal inlet 4. The temperature of the granular silicon seed crystals is maintained at 1000-1100℃ using heating device 5. At this temperature, hydrogen reduces trichlorosilane, and the resulting elemental silicon continuously deposits on the granular silicon seed crystals. The gradually growing granular silicon particles enter filter 8 through granular silicon inlet 9 and are blown upwards by auxiliary carrier gas inlet 11. The granular silicon particles in the filter act as filler to filter silicon powder particles. The filtered granular silicon particles are discharged from granular silicon outlet 6 and enter reactor 1. This process does not require additional filter filler. When the granular silicon reaches the process set size, it is discharged from the bottom product outlet 10. The filtered silicon powder particles can be discharged from granular silicon outlet 6 and then enter reactor 1 to continue to be deposited and grown as seed crystals.

[0024] This invention employs a reactor combined with a moving bed filter, offering significant advantages over traditional fluidized bed reactors. In a fluidized bed reactor, particles are in a state of vigorous fluidization. While gas-solid contact is sufficient, severe backmixing occurs, causing some particles to be discharged before reaching the target size, resulting in a wide product size distribution. Simultaneously, the high-speed airflow within the fluidized bed reactor easily causes violent collisions between particles and between particles and the reactor wall, leading to particle breakage and the generation of large amounts of fine silicon powder. This silicon powder not only affects product quality but also easily deposits within the reactor, reducing operating efficiency and increasing equipment maintenance costs. In contrast, the moving bed reactor device of this invention achieves precise particle control through the ingenious design of the moving bed filter. The granular silicon seed crystals in the moving bed filter serve both as seed crystals to promote particle growth and as a filter filler, eliminating the need for additional filter filler and reducing production costs. In a moving bed reactor, particles move downwards in a relatively orderly manner, resulting in more stable gas-solid contact and reduced backmixing. This allows the particles to grow within the reactor according to predetermined process conditions, producing uniformly sized granular silicon products. Furthermore, the moving bed filter effectively captures fine silicon powder, reintroducing it into the reaction system for reuse. This not only improves silicon utilization and increases production capacity but also avoids the impact of silicon deposition on reactor operation, ensuring long-term stable operation and achieving continuous production. It offers significant advantages such as high capacity and low investment.

[0025] Furthermore, it should be understood that after reading the above description of this utility model, those skilled in the art can make various alterations or modifications to this utility model, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A moving bed reactor apparatus for producing granular silicon, characterized in that, Includes an interconnected reactor (1) and filter (8); The reactor (1) is provided with a silane gas inlet (2) and a hydrogen gas inlet (3) at the top, a product outlet (10) at the bottom, and a heating device (5) in the middle section of the side; a seed inlet (4) is provided on the side of the reactor (1) above the heating device (5). The filter (8) has a granular silicon inlet (9) at the bottom side, which is connected to the bottom side of the reactor (1); the filter (8) has a granular silicon outlet (6) at the top side, which is inside the reactor (1) and located above or below the heating device (5); the filter (8) has an auxiliary carrier gas inlet (11) at the bottom and a tail gas outlet (7) on the side.

2. The moving bed reactor apparatus for producing granular silicon according to claim 1, characterized in that, The heating device (5) includes one or more of the following: resistance heater, induction heater, and microwave heater.

3. The moving bed reactor apparatus for producing granular silicon according to claim 1 or 2, characterized in that, The heating device (5) is inside and / or outside the reactor (1).

4. The moving bed reactor apparatus for producing granular silicon according to claim 1, characterized in that, The size of the auxiliary carrier gas inlet (11) is smaller than the size of the granular silicon inlet (9).

5. The moving bed reactor apparatus for producing granular silicon according to claim 1, characterized in that, The exhaust outlet (7) is located on the upper or lower side of the filter (8).

6. The moving bed reactor apparatus for producing granular silicon according to claim 1, characterized in that, The filter (8) is made of one or more of the following materials: metal silicide, tungsten, niobium, tantalum, and alloy. The alloy contains one or more of the following metal elements: tungsten, niobium, and tantalum.

7. The moving bed reactor apparatus for producing granular silicon according to claim 1, characterized in that, The exhaust gas outlet (12) of the equipment on the side top of the reactor (1).

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