Fluidized bed reactor and method for producing granular polysilicon

Abstract

The application discloses a fluidized bed reactor and method for preparing granular polysilicon, which comprises a fluidized bed inner shell, a heating device, a gas phase inlet device and a cooling jacket. The top of the fluidized bed inner shell is provided with a seed crystal inlet and a gas phase outlet, and the bottom is provided with a discharge port and a spouting gas inlet. The inside of the fluidized bed inner shell is provided with a spouting pipe which is connected with the spouting gas inlet. The heating device is arranged at the lower part of the fluidized bed inner shell and outside the fluidized bed inner shell. The gas phase inlet device is connected with the lower part of the fluidized bed inner shell and is arranged above the heating device. The cooling jacket is arranged at the lower part of the fluidized bed inner shell and is arranged above the gas phase inlet device. The application can make the fluidized bed wall temperature of the reaction zone lower than the reaction temperature of the material in the reaction zone, thereby avoiding problems such as deposition on the fluidized bed wall.

Description

Technical Field

[0001] This invention belongs to the field of polycrystalline silicon technology, specifically relating to a fluidized bed reactor and method for preparing granular polycrystalline silicon. Background Technology

[0002] Polycrystalline silicon mainly comes in two forms: rod-shaped polycrystalline silicon produced by bell-type reduction furnaces and granular polycrystalline silicon produced by fluidized bed reactors. Both are produced using CVD (chemical vapor deposition) processes, where silane, trichlorosilane, or dichlorosilane gaseous components undergo thermal decomposition at the gas-solid interface to generate solid deposits. The difference lies in the deposition process: rod-shaped polycrystalline silicon is produced by depositing trichlorosilane or dichlorosilane onto thin rod-shaped polycrystalline silicon cores in a bell-type reduction furnace, resulting in rod-shaped polycrystalline silicon of a certain diameter; while granular polycrystalline silicon is produced by depositing silane, trichlorosilane, or dichlorosilane onto the surface of small silicon particles in a fluidized bed reactor, resulting in spherical polycrystalline silicon particles of a certain size.

[0003] Currently, polycrystalline silicon is mainly N-type polycrystalline silicon, with a purity of 99.9999999~99.999999999%. The introduction of any impurity may cause the product to be unqualified. Furthermore, the vapor deposition process requires reaction on a high-temperature solid surface, so its heating method is crucial.

[0004] The production process of granular polycrystalline silicon involves accumulating a certain amount of silicon particles inside a fluidized bed reactor. A gaseous material is introduced at the bottom of the reactor, causing the silicon particles to fluidize under the influence of the gas. Simultaneously, the gaseous material comes into full contact with the surface of the silicon particles and undergoes thermal decomposition to form solid deposits. However, the silicon particles in the fluidized state are discontinuous, making it impossible to use the resistance heating method employed in the production of rod-shaped polycrystalline silicon, which involves heating a high-purity silicon core in a reduction furnace by applying electricity. Furthermore, to ensure the purity of the polycrystalline silicon, it is also impossible to install a heating device inside the fluidized bed reactor.

[0005] Currently, in the production process of granular polysilicon, fluidized bed reactors in the industry employ external heating. This involves placing an isolation layer between the material and the heating device to prevent contamination. External heating devices primarily include electric heating and electromagnetic induction heating. Electric heating uses a resistance heating device directly outside the isolation layer. Heat is conducted to the isolation layer via convection or radiation, and then to the silicon particle bed inside the fluidized bed. Electromagnetic induction heating, on the other hand, involves placing an induction layer outside the isolation layer, in close contact with it. An electromagnetic induction heating coil is placed outside the induction layer. During heating, the coil first generates an electromagnetic induction effect in the induction layer, producing heat. The heated induction layer then conducts the heat to the isolation layer via convection or radiation, and then to the silicon particle bed inside the fluidized bed. Therefore, regardless of whether it's electric heating or electromagnetic induction heating, the heat must first reach the isolation layer before being transferred to the silicon particle bed inside the fluidized bed via radiation or convection. However, in actual operation, these two heating methods have at least the following shortcomings:

[0006] 1) The temperature of the isolation layer wall in the fluidized bed reactor is always slightly higher than the temperature of the silicon particles in the silicon particle bed. When the gaseous material in the bed comes into contact with the silicon particles and reacts, thermal decomposition reaction will also occur and deposit on the isolation layer wall in the reaction zone of the fluidized bed reactor. As the fluidized bed reactor continues to operate, the deposited layer on the isolation layer wall in this area will become thicker and thicker, resulting in the inner diameter of the reaction zone becoming smaller and smaller. Eventually, the inner diameter of the reaction zone will be too small to produce.

[0007] 2) The isolation layer wall in the reaction zone of the fluidized bed reactor thickens due to deposition, while the remaining low-temperature areas do not thicken. This results in inconsistent thickness of the isolation layer wall in different areas of the fluidized bed reactor. During equipment operation, internal stress may be generated, leading to wall damage and requiring emergency shutdown and maintenance of the fluidized bed reactor. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a fluidized bed reactor and method for preparing granular polycrystalline silicon, which can make the temperature of the fluidized bed wall in the reaction zone lower than the reaction temperature of the material in the reaction zone, thus avoiding problems such as deposition on the fluidized bed wall.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0010] According to a first aspect of the present invention, a fluidized bed reactor for preparing granular polycrystalline silicon is provided, comprising a fluidized bed shell, a heating device, a gas phase inlet device, and a cooling jacket, wherein:

[0011] The top of the fluidized bed inner shell is provided with a seed crystal inlet and a gas phase outlet, and the bottom is provided with a discharge port and a jet gas inlet. The inside of the fluidized bed inner shell is provided with a jet pipe, which is connected to the jet gas inlet to introduce jet gas and form an intermediate jet flow zone.

[0012] The heating device is located at the lower part of the inner shell of the fluidized bed and outside the inner shell of the fluidized bed, and is used to heat the seed crystal and silicon particles.

[0013] The gas phase inlet device is connected to the lower part of the fluidized bed inner shell and is located above the heating device. It is used to introduce gas phase material to form a peripheral bubbling fluidization zone.

[0014] The cooling jacket is located at the lower part of the fluidized bed inner shell and above the gas phase inlet device. It is used to cool the wall of the reaction zone of the fluidized bed inner shell so that the temperature of the fluidized bed wall in the reaction zone is lower than the reaction temperature of the material in the reaction zone.

[0015] Optionally, the bottom of the lower part of the fluidized bed inner shell is a conical structure, and the angle between the conical surface and the horizontal line is greater than or equal to the angle of repose of the material inside the fluidized bed inner shell.

[0016] Optionally, the gas phase inlet device includes a gas phase inlet, a gas phase distribution chamber, and gas phase nozzles; the gas phase inlet passes through and is connected to the inner shell of the fluidized bed, the gas phase distribution chamber is located inside the inner shell of the fluidized bed and is connected to the gas phase inlet; the gas phase nozzles are evenly distributed in the upper part of the gas phase distribution chamber and are vertically upward.

[0017] Optionally, the upper surface of the gas phase distribution chamber is an inclined plane, and the angle between the inclined plane and the horizontal line is greater than or equal to the angle of repose of the material in the inner shell of the fluidized bed.

[0018] Optionally, there can be multiple gas phase inlets, which are divided into multiple rings and evenly distributed in a ring shape.

[0019] Optionally, the upper edge of the nozzle is positioned 50-300 mm higher than the outlet position of the lowest ring of gas phase nozzles.

[0020] Optionally, the ratio of the diameter of the spout to the average diameter of the silicon particles does not exceed 50, the ratio of the diameter of the spout to the inner diameter of the fluidized bed shell is 0.05 to 0.5, and the ratio of the height of the silicon particle bed in the reaction zone to the inner diameter of the fluidized bed shell is 0.5 to 10.

[0021] Optionally, a fluidized bed outer shell is provided outside the inner shell of the fluidized bed, and the heating device and cooling jacket are located between the outer shell of the fluidized bed and the inner shell of the fluidized bed.

[0022] Optionally, the fluidized bed shell includes a top, a bottom, and a lower portion, and the fluidized bed inner shell includes a top, a bottom, and a lower portion; the lower portion is located within the bottom of the outer shell, forming the bottom of the fluidized bed; the lower portion is located within the lower portion of the outer shell, forming the lower portion of the fluidized bed; the top is located within the top of the outer shell, forming the top of the fluidized bed; the bottom and lower portion of the inner shell are fixedly connected, and the top and lower portion of the fluidized bed are connected via flanges.

[0023] Optionally, an insulation layer is provided in the gap between the outer shell and the inner shell of the fluidized bed.

[0024] Optionally, the fluidized bed shell is made of one of carbon steel, stainless steel, titanium alloy, or nickel-based alloy, and the fluidized bed inner shell is made of one of high-purity quartz, silicon carbide, silicon nitride, or silicon.

[0025] According to a second aspect of the present invention, a method for preparing granular polycrystalline silicon is also provided, which employs the fluidized bed reactor for preparing granular polycrystalline silicon as described above, the steps of which include:

[0026] Seed crystals are added to the inner shell of the fluidized bed and stacked to form a silicon particle bed until the silicon particle bed reaches the upper edge of the nozzle.

[0027] The jetting gas is introduced to form an intermediate jetting zone in the silicon particle bed. At the same time, heating begins and cooling medium is introduced into the cooling jacket.

[0028] Seed crystals are continuously added. When the silicon particle bed height reaches a preset position, and the silicon particle bed material temperature in the reaction zone of the fluidized bed reaches a first preset temperature while the fluidized bed wall temperature in the reaction zone remains at a second preset temperature, gaseous material is introduced. This causes the silicon particles above the gas nozzle to move and reach a fluidized state, forming a peripheral bubbling fluidized zone. The second preset temperature is lower than the first preset temperature.

[0029] High-temperature silicon particles are ejected upwards by the jetting gas in the central jetting zone and fall into the surrounding bubbling fluidized zone. The silicon particles in the surrounding bubbling fluidized zone move and contact with each other, transferring heat and raising the temperature of the material in the reaction zone to the first preset temperature. The gaseous material decomposes and deposits on the surface of the silicon particles, and the silicon particles gradually grow. During this process, unreacted gaseous material and jetting gas are discharged from the gas phase outlet. Some silicon particles continue to be suspended and deposited in the surrounding bubbling fluidized zone, while other silicon particles fall into the heating zone at the bottom of the fluidized bed shell and are heated to the third preset temperature. Some of the heated silicon particles are carried upwards by the jetting gas and fall into the surrounding bubbling fluidized zone to continue the reaction. The remaining silicon particles are discharged from the outlet after being driven by the jetting gas, resulting in granular polycrystalline silicon product.

[0030] Optionally, the gaseous material is a mixture of one of silane, trichlorosilane, or dichlorosilane with hydrogen or nitrogen, and the agitator gas is hydrogen or nitrogen.

[0031] Optionally, the inlet velocity of the gaseous material is 1~20m / s, and the inlet velocity of the jetting gas is 2~40m / s.

[0032] Optionally, the first preset temperature is 500~1100℃.

[0033] Optionally, the second preset temperature is 300~1050℃, and is at least 50℃ lower than the reaction temperature of the materials in the reaction zone.

[0034] Optionally, the third preset temperature is 550~1300℃, and is at least 50℃ higher than the reaction temperature of the materials in the reaction zone.

[0035] Optionally, the pressure in the inner shell of the fluidized bed is 0~1 MPaG.

[0036] Optionally, the seed crystals can have a grain size of 200~4000μm.

[0037] Optionally, the particle size of the granular polycrystalline silicon product is 600~6000μm.

[0038] Beneficial effects:

[0039] The fluidized bed reactor and method for preparing granular polycrystalline silicon of the present invention achieves separation of the heating zone and the reaction zone inside the fluidized bed by setting heating devices, gas inlet devices, and cooling jackets at different positions in the inner shell of the fluidized bed. At the same time, by setting a jet pipe to introduce jet gas, the silicon particles are circulated between the heating zone and the reaction zone. Thus, while ensuring the reaction temperature of the material in the reaction zone, the cooling jacket can keep the temperature of the fluidized bed wall in the reaction zone lower than the reaction temperature of the material in the reaction zone. This avoids problems such as deposition on the fluidized bed wall and the resulting wall damage, extends the service life of the fluidized bed reactor, and reduces production costs. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a fluidized bed reactor for preparing granular polycrystalline silicon in an embodiment of the present invention.

[0041] In the diagram: 1-Jet gas inlet; 2-Discharge port; 301-Bottom of outer shell; 302-Lower part of outer shell; 303-Top of outer shell; 4-Heating device; 501-Gas phase inlet; 502-Gas phase distribution chamber; 503-Gas phase nozzle; 6-Cooling jacket; 701-Bottom of inner shell; 702-Lower part of inner shell; 703-Top of inner shell; 8-Lower flange; 9-Upper flange; 10-Gas phase outlet; 11-Seed crystal inlet; 12-Insulation layer; 13-Jet pipe. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0043] In the description of this invention, it should be noted that the terms "above" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of the description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] It is understood that, without conflict, the various embodiments and features in the embodiments of the present invention can be combined with each other.

[0047] It is understood that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, while the parts unrelated to the present invention are not shown in the drawings.

[0048] To address the issues of deposition on the fluidized bed wall (i.e., the isolation layer wall) in the reaction zone of fluidized bed reactors during the current production of granular polycrystalline silicon, this invention provides a fluidized bed reactor for preparing granular polycrystalline silicon, comprising a fluidized bed inner shell, a heating device, a gas phase inlet device, and a cooling jacket, wherein:

[0049] The top of the fluidized bed inner shell is provided with a seed crystal inlet and a gas phase outlet, the bottom of the fluidized bed inner shell is provided with a discharge port and a jet gas inlet, and the inside of the fluidized bed inner shell is provided with a jet pipe connected to the jet gas inlet for introducing jet gas to form an intermediate jet flow zone in the silicon particle bed of the reaction zone of the fluidized bed inner shell.

[0050] The heating device is located at the lower part of the inner shell of the fluidized bed and outside the inner shell of the fluidized bed. It is used to heat the seed crystals and silicon particles that fall into the heating zone at the lower part of the inner shell of the fluidized bed.

[0051] The gas phase inlet device is connected to the lower part of the fluidized bed inner shell and is located above the heating device. It is used to introduce gas phase material to form a peripheral bubbling fluidization zone around the central jet flow zone.

[0052] The cooling jacket is located at the lower part of the fluidized bed inner shell and above the gas phase inlet device. It is used to cool the wall of the reaction zone of the fluidized bed inner shell so that the temperature of the fluidized bed wall in the reaction zone is lower than the reaction temperature of the material in the reaction zone.

[0053] Furthermore, the present invention also provides a method for preparing granular polycrystalline silicon, which employs the fluidized bed reactor described above for preparing granular polycrystalline silicon, and the steps include:

[0054] Seed crystals are added to the inner shell of the fluidized bed and stacked to form a silicon particle bed until the silicon particle bed reaches the upper edge of the nozzle.

[0055] The jetting gas is introduced to form an intermediate jetting zone in the silicon particle bed. At the same time, heating begins and cooling medium is introduced into the cooling jacket.

[0056] Seed crystals are added continuously. When the silicon particle bed height reaches a preset position, and the silicon particle bed material temperature in the reaction zone of the fluidized bed reaches a first preset temperature while the fluidized bed wall temperature in the reaction zone remains at a second preset temperature, gaseous material is introduced. After being evenly distributed in the gas distribution chamber, the gaseous material is ejected from the gas nozzle, driving the silicon particles above the nozzle to move into a fluidized state, forming a peripheral bubbling fluidized zone. The second preset temperature is lower than the first preset temperature. High-temperature silicon particles carried upwards by the jetting gas in the central jetting zone fall into the peripheral bubbling fluidized zone and interact with the surrounding bubbling fluid. In the reaction zone, silicon particles move and contact each other, transferring heat and causing the temperature of the material in the reaction zone to reach the first preset temperature. The gaseous material decomposes and deposits on the surface of the silicon particles, and the silicon particles gradually grow. During this period, unreacted gaseous material and jet gas are discharged from the gas phase outlet. Some silicon particles continue to be suspended and deposited in the surrounding bubbling fluidized zone, while other silicon particles fall into the heating zone at the bottom of the inner shell of the fluidized bed and are heated to the third preset temperature. Some of the heated silicon particles are carried upward by jet gas and fall into the surrounding bubbling fluidized zone to continue the reaction. The remaining silicon particles are discharged from the outlet after being driven by jet gas, resulting in granular polycrystalline silicon products.

[0057] The fluidized bed reactor and method for preparing granular polycrystalline silicon of the present invention achieves separation of the heating zone and the reaction zone inside the fluidized bed by setting heating devices, gas inlet devices, and cooling jackets at different positions in the inner shell of the fluidized bed. At the same time, by setting a jet pipe to introduce jet gas, the silicon particles are circulated between the heating zone and the reaction zone. Thus, while ensuring the reaction temperature of the material in the reaction zone, the cooling jacket can keep the temperature of the fluidized bed wall in the reaction zone lower than the reaction temperature of the material in the reaction zone. This avoids problems such as deposition on the fluidized bed wall and the resulting wall damage, extends the service life of the fluidized bed reactor, and reduces production costs.

[0058] Example 1

[0059] like Figure 1As shown, this embodiment discloses a fluidized bed reactor for preparing granular polycrystalline silicon, including a fluidized bed shell, a heating device 4, a gas phase inlet device, and a cooling jacket. The top of the fluidized bed shell is provided with a seed crystal inlet 11 and a gas phase outlet 10, while the bottom of the fluidized bed shell is provided with a discharge port 2 and a jet gas inlet 1. A jet pipe 13 is located at the center of the fluidized bed shell, and the jet pipe 13 is fixed to the lower part of the fluidized bed shell by a bracket. Furthermore, the inlet end of the jet pipe 13 is connected to the jet gas inlet 1, and the outlet end of the jet pipe 13 is vertically upward for introducing jet gas, forming an intermediate jetting zone in the silicon particle bed of the reaction zone within the fluidized bed shell. Heating device 4 is located at the lower part of the fluidized bed inner shell and outside the fluidized bed inner shell. It is used to heat the seed crystals and silicon particles falling into the lower part of the fluidized bed inner shell. Gas phase inlet device is connected to the lower part of the fluidized bed inner shell and is located above heating device 4. It is used to introduce gas phase material to form a peripheral bubbling fluidized zone around the central jet zone. Cooling jacket 6 is located at the lower part of the fluidized bed inner shell and above gas phase inlet device. That is, heating device 4, gas phase inlet device, and cooling jacket 6 are arranged sequentially from the bottom of the lower part of the fluidized bed inner shell upwards. Cooling jacket 6 is used to cool the wall surface of the reaction zone of the fluidized bed inner shell so that the temperature of the fluidized bed wall surface of the reaction zone is lower than the reaction temperature of the material in the reaction zone.

[0060] The upper edge of the nozzle is 50-300mm higher than the lowest outlet position in the gas phase inlet device (i.e., the outlet position of the lowest ring of gas phase nozzle 503 in the following text) to prevent the material height from exceeding the upper edge of the nozzle during feeding and falling into the nozzle, which would increase the nozzle air resistance and make it difficult to start up.

[0061] In some embodiments, the ratio of the diameter of the spout 13 to the average diameter of the silicon particles in the silicon particle bed formed in the fluidized bed reactor does not exceed 50, for example, it can be 10, 20, 30, 40, etc., but is not limited thereto. The ratio of the diameter of the spout 13 to the inner diameter of the fluidized bed shell is 0.05 to 0.5, for example, it can be 0.1, 0.2, 0.3, 0.4, etc., but is not limited thereto. The ratio of the height of the silicon particle bed in the reaction zone to the inner diameter of the fluidized bed shell is 0.5 to 10, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, etc., but is not limited thereto. By controlling the ratios within the above specific ranges, a spouting effect can be ensured, thereby enabling the material to be carried by the spouting gas from the spout and through the silicon particle bed.

[0062] In some embodiments, the bottom of the inner shell of the fluidized bed is a conical structure, and the angle between the conical surface and the horizontal line is not less than the angle of repose of the material (i.e., silicon particles in the silicon particle bed) inside the inner shell of the fluidized bed, that is, greater than or equal to the angle of repose of the material. The angle of repose of the material is determined based on actual material measurements, and will not be elaborated here. This conical structure prevents silicon particles from remaining at the bottom of the cone, causing them to move downwards under gravity. This, combined with the action of the bottom jet gas, carries smaller silicon particles upwards, allowing them to fall into the surrounding bubbling fluidization zone for further reaction. Larger silicon particles, whose gravity is greater than the upward force generated by the jet gas, cannot be carried away and are ultimately discharged from the outlet at the bottom of the fluidized bed reactor.

[0063] In some embodiments, the gas phase inlet device includes a gas phase inlet 501, a gas phase distribution chamber 502, and gas phase nozzles 503. The gas phase inlet 501 passes through and is connected to the inner shell of the fluidized bed, and the gas phase distribution chamber 502 is fixed inside the inner shell of the fluidized bed and connected to the gas phase inlet 501. Preferably, there are multiple gas phase nozzles 503, which are evenly and fixedly distributed in the upper part of the gas phase distribution chamber 502 and vertically upward, to ensure that the gas phase material is more uniformly ejected after passing through the gas phase nozzles, thereby driving the silicon particles above the nozzles to move to a fluidized state and forming a peripheral bubbling fluidized zone around the central jet zone.

[0064] In some embodiments, the upper surface of the gas phase distribution chamber 502 is an inclined plane, and the angle between the inclined plane and the horizontal line is not less than the angle of repose of the material (i.e., silicon particles in the silicon particle bed) in the fluidized bed shell, that is, greater than or equal to the angle of repose of the material.

[0065] In some embodiments, there may be multiple gas phase inlets 501 and gas phase distribution chambers 502. For example, there may be multiple gas phase inlets 501, which are divided into multiple rings and evenly distributed in a ring shape. Furthermore, the gas phase inlets 501 may be equipped with flow meters to ensure that the gas phase material can enter each gas phase distribution chamber 502 evenly and finally enter the gas phase nozzle 503 evenly, thus ensuring the stability of the fluidized bed.

[0066] In some embodiments, a fluidized bed outer shell is provided outside the inner shell of the fluidized bed. The fluidized bed outer shell serves a protective function, ensuring that gas leakage is prevented when the inner shell of the fluidized bed is damaged, thus guaranteeing the absolute safety of the equipment. The heating device 4 and the cooling jacket 6 are both located between the fluidized bed outer shell and the inner shell of the fluidized bed.

[0067] Specifically, the fluidized bed outer shell includes a top shell 303, a lower shell 302, and a bottom shell 301, while the fluidized bed inner shell includes a top shell 703, a lower shell 702, and a bottom shell 701. The bottom shell 701 is located within and fixed to the bottom shell 301, forming the bottom of the fluidized bed. The lower shell 702 is located within and fixed to the lower shell 302 by a support, forming the lower part of the fluidized bed. The top shell 703 is located within and fixed to the top shell 303, forming the top of the fluidized bed. The bottom shell 701 and the lower shell 702 are fixedly connected, as are the bottom shell 301 and the lower shell 302. The top of the fluidized bed is provided with an upper flange 9, and the lower part of the fluidized bed is provided with a lower flange 8; the top and lower parts of the fluidized bed are connected via the upper flange 9 and the lower flange 8. Seed crystal inlet 11 and gas phase outlet 10 are disposed on the top of the fluidized bed, wherein the gas phase outlet 10 is preferably located at the center of the top of the fluidized bed, and the seed crystal inlet 11 is located at the periphery of the top of the fluidized bed. Discharge outlet 2 and jet gas inlet 1 are disposed on the bottom of the fluidized bed and are located at the center of the bottom of the fluidized bed, and the discharge outlet 2 is located at the periphery of the jet gas inlet 1.

[0068] In some embodiments, an insulation layer 12 is also provided in the gap between the fluidized bed outer shell and the fluidized bed inner shell.

[0069] In some embodiments, the fluidized bed shell is made of one of the following metal materials: carbon steel, stainless steel, titanium alloy, nickel-based alloy, etc., and the fluidized bed inner shell is made of one of the following non-metallic materials: high-purity quartz, silicon carbide, silicon nitride, silicon, graphite, etc.

[0070] In some embodiments, the heating device 4 may employ electric heating or electromagnetic induction heating, but is not limited to these. When electromagnetic induction heating is used, the induction layer should be fixed to the surface of the fluidized bed inner shell.

[0071] Example 2

[0072] This embodiment 2 discloses a method for preparing granular polycrystalline silicon, which uses the fluidized bed reactor for preparing granular polycrystalline silicon described in embodiment 1, and the steps include:

[0073] Seed crystals are added to the fluidized bed inner shell from the seed crystal inlet 11 at the top of the fluidized bed inner shell. The added seed crystals accumulate at the bottom of the fluidized bed inner shell to form a silicon particle bed layer until the silicon particle bed layer reaches the upper edge of the nozzle 13.

[0074] Initially, jet gas is introduced into the jet gas inlet 1. After passing through the inner shell of the fluidized bed, the jet gas is discharged from the gas phase outlet 10 at the top, forming an intermediate jet jet zone in the silicon particle bed. At the same time, the heating device 4 starts heating and introduces cooling medium into the cooling jacket 6.

[0075] Seed crystals are added continuously. When the height of the silicon particle bed reaches the preset position, and the temperature of the silicon particle bed material in the reaction zone of the fluidized bed reaches the first preset temperature and the temperature of the fluidized bed wall in the reaction zone is maintained at the second preset temperature, gaseous material is introduced into the gas inlet 501. After being evenly distributed through the gas distribution chamber 502, the gaseous material is sprayed out through the gas nozzle 503, which drives the silicon particles above the gas nozzle 503 to move to the fluidized state, forming a peripheral bubbling fluidized zone. The second preset temperature is lower than the first preset temperature.

[0076] After being ejected upwards by the jetting gas in the central jetting zone, the high-temperature silicon particles are finally scattered like a fountain and fall into the surrounding bubbling fluidized zone. The silicon particles in the surrounding bubbling fluidized zone interact and transfer heat, raising the temperature of the material in the reaction zone to the set reaction temperature (i.e., the first preset temperature). The gaseous material ejected from the gaseous nozzle 503 comes into full contact with the silicon particles in the surrounding bubbling fluidized zone. The gaseous material decomposes and deposits on the surface of the silicon particles, causing them to gradually grow. During this process, unreacted gaseous material and jetting gas are discharged from the gaseous outlet. Some silicon particles (smaller ones) continue to be suspended and deposited in the surrounding bubbling fluidized zone, while other silicon particles (larger ones) are pushed downwards by gravity. The silicon particles move downwards and fall to the upper part of the gas distribution chamber. Under the action of gravity, they continue to move downwards along the upper slope and fall into the heating zone at the bottom of the fluidized bed inner shell. The silicon particles in the heating zone are heated by the heating device 4 to ensure that the temperature of these silicon particles reaches the third preset temperature when they reach the bottom of the fluidized bed inner shell. At this time, some of the smaller silicon particles are carried by the jet gas into the jet pipe 13 and move upwards to enter the surrounding bubbling fluidized zone again to continue the reaction and transfer heat to the silicon particles in the surrounding bubbling fluidized zone. After being carried by the jet gas, the remaining larger silicon particles are discharged from the discharge port at the bottom of the fluidized bed inner shell and enter the downstream process, thereby preparing granular polycrystalline silicon products.

[0077] In some embodiments, the gaseous material is a mixture of one of silane, trichlorosilane, and dichlorosilane with hydrogen or nitrogen, wherein the hydrogen or nitrogen does not participate in the reaction but is used only as an auxiliary gas to establish the fluidization state of the silicon particles, and is then discharged from the gas phase outlet.

[0078] In some implementations, the jetting gas is hydrogen or nitrogen, and it does not participate in the reaction but is only used to move the silicon particles.

[0079] In some implementations, the inlet velocity of the gaseous material is 1~20 m / s, and the inlet velocity of the jetting gas is 2~40 m / s. This parameter range ensures that the silicon particles above the gaseous nozzle reach a fluidized state, resulting in better fluidization.

[0080] In some embodiments, the temperature of the jetting gas and the temperature of the material in the reaction zone (i.e., the first preset temperature, which is the reaction temperature required by this method) are 500~1100℃. The specific temperature can be adjusted according to the selection of the gas phase material. For example, when silane is used, the first preset temperature is relatively low, which can be 500℃; when trichlorosilane is used, the first preset temperature is relatively high, which can be 1080℃, but it is not limited to this.

[0081] In some embodiments, the fluidized bed wall temperature and the temperature of the introduced gaseous material in the reaction zone are 300~1500°C, that is, the second preset temperature is 300~1500°C, and the fluidized bed wall temperature and the temperature of the introduced gaseous material in the reaction zone are at least 50°C lower than the reaction temperature of the material in the reaction zone.

[0082] In some embodiments, the material temperature in the heating zone (i.e., the third preset temperature) is 550~1300°C, and is at least 50°C higher than the reaction temperature of the material in the reaction zone.

[0083] In some embodiments, the pressure in the reaction zone within the fluidized bed shell is 0~1 MPaG, preferably 0.1~0.6 MPaG.

[0084] In some embodiments, the seed crystals added to the seed crystal inlet 11 have a particle size of 200~4000μm.

[0085] In some embodiments, the particle size of the granular polycrystalline silicon product discharged from outlet 2 is 600~6000μm.

[0086] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A fluidized bed reactor for preparing granular polycrystalline silicon, characterized in that, This includes the fluidized bed inner shell, heating device, gas phase inlet device, and cooling jacket; The top of the fluidized bed inner shell is provided with a seed crystal inlet and a gas phase outlet, and the bottom is provided with a discharge port and a jet gas inlet. The inside of the fluidized bed inner shell is provided with a jet pipe, which is connected to the jet gas inlet for introducing jet gas to form an intermediate jet flow zone. The heating device is located at the lower part of the inner shell of the fluidized bed and outside the inner shell of the fluidized bed, and is used to heat the seed crystal and silicon particles. The gas phase inlet device is connected to the lower part of the inner shell of the fluidized bed and is located above the heating device. It is used to introduce gas phase material to form a peripheral bubbling fluidized zone. The cooling jacket is located at the lower part of the fluidized bed inner shell and above the gas phase inlet device. It is used to cool the wall of the reaction zone of the fluidized bed inner shell so that the temperature of the fluidized bed wall in the reaction zone is lower than the reaction temperature of the material in the reaction zone. The gas phase inlet device includes a gas phase inlet, a gas phase distribution chamber, and gas phase nozzles. The gas phase inlet passes through and is connected to the inner shell of the fluidized bed. The gas phase distribution chamber is located inside the inner shell of the fluidized bed and is connected to the gas phase inlet. There are multiple gas phase nozzles, which are evenly distributed in the upper part of the gas phase distribution chamber and are vertically upward.

2. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 1, characterized in that, The bottom of the lower part of the fluidized bed inner shell is a conical structure, and the angle between the conical surface and the horizontal line is greater than or equal to the angle of repose of the material inside the fluidized bed inner shell.

3. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 1, characterized in that, The upper surface of the gas phase distribution chamber is an inclined plane, and the angle between the inclined plane and the horizontal line is greater than or equal to the angle of repose of the material in the inner shell of the fluidized bed.

4. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 3, characterized in that, There are multiple gas phase inlets, which are divided into multiple rings and are evenly distributed in a ring shape.

5. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 4, characterized in that, The upper edge of the nozzle is 50-300 mm higher than the outlet position of the lowest ring of the gas phase nozzle.

6. The fluidized bed reactor for preparing granular polycrystalline silicon according to any one of claims 1 to 4, characterized in that, The ratio of the diameter of the ejector pipe to the average diameter of the silicon particles does not exceed 50, the ratio of the diameter of the ejector pipe to the inner diameter of the fluidized bed shell is 0.05~0.5, and the ratio of the height of the silicon particle bed in the reaction zone to the inner diameter of the fluidized bed shell is 0.5~10.

7. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 6, characterized in that, The fluidized bed inner shell is provided with a fluidized bed outer shell, and the heating device and the cooling jacket are both located between the fluidized bed outer shell and the fluidized bed inner shell.

8. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 7, characterized in that, The fluidized bed outer shell includes a top, a bottom, and a top, while the fluidized bed inner shell includes a top, a bottom, and a top. The bottom of the inner shell is located within the bottom of the outer shell, forming the bottom of the fluidized bed; The lower part of the inner shell is located within the lower part of the outer shell, forming the lower part of the fluidized bed; The top of the inner shell is located within the top of the outer shell, forming the top of the fluidized bed; The bottom of the inner shell is fixedly connected to the lower part of the inner shell, and the top of the fluidized bed is connected to the lower part of the fluidized bed via a flange.

9. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 8, characterized in that, A heat insulation layer is also provided in the gap between the outer shell and the inner shell of the fluidized bed.

10. The fluidized bed reactor for preparing granular polycrystalline silicon according to claim 9, characterized in that, The outer shell of the fluidized bed is made of one of carbon steel, stainless steel, titanium alloy, and nickel-based alloy, and the inner shell of the fluidized bed is made of one of high-purity quartz, silicon carbide, silicon nitride, and silicon.

11. A method for preparing granular polycrystalline silicon, characterized in that, It employs the fluidized bed reactor for preparing granular polycrystalline silicon as described in any one of claims 1 to 10, and the steps include: Seed crystals are added to the inner shell of the fluidized bed and stacked to form a silicon particle bed until the silicon particle bed reaches the upper edge of the nozzle. The jetting gas is introduced to form an intermediate jetting zone in the silicon particle bed. At the same time, heating begins and cooling medium is introduced into the cooling jacket. Seed crystals are continuously added. When the silicon particle bed height reaches a preset position, and the silicon particle bed material temperature in the reaction zone of the fluidized bed reaches a first preset temperature while the fluidized bed wall temperature in the reaction zone remains at a second preset temperature, gaseous material is introduced. This causes the silicon particles above the gaseous nozzle to move and reach a fluidized state, forming a peripheral bubbling fluidized zone. The second preset temperature is lower than the first preset temperature. High-temperature silicon particles are ejected upwards by the jetting gas in the central jetting zone and fall into the surrounding bubbling fluidized zone. The silicon particles in the surrounding bubbling fluidized zone move and contact with each other, transferring heat and raising the temperature of the material in the reaction zone to the first preset temperature. The gaseous material decomposes and deposits on the surface of the silicon particles, and the silicon particles gradually grow. During this process, unreacted gaseous material and jetting gas are discharged from the gas phase outlet. Some silicon particles continue to be suspended and deposited in the surrounding bubbling fluidized zone, while other silicon particles fall into the heating zone at the bottom of the fluidized bed shell and are heated to the third preset temperature. Some of the heated silicon particles are carried upwards by the jetting gas and fall into the surrounding bubbling fluidized zone to continue reacting. The remaining silicon particles are discharged from the outlet after being driven by the jetting gas, resulting in granular polycrystalline silicon product.

12. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The gaseous material is a mixture of one of silane, trichlorosilane, and dichlorosilane with hydrogen or nitrogen, and the jetting gas is hydrogen or nitrogen.

13. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The flow rate of the gaseous material is 1~20m / s, and the flow rate of the jetting gas is 2~40m / s.

14. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The first preset temperature is 500~1100℃.

15. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The second preset temperature is 300~1050℃, and is at least 50℃ lower than the reaction temperature of the material in the reaction zone.

16. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The third preset temperature is 550~1300℃, and is at least 50℃ higher than the reaction temperature of the material in the reaction zone.

17. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The pressure inside the fluidized bed shell is 0~1 MPaG.

18. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The seed crystals have a particle size of 200~4000μm.

19. The method for preparing granular polycrystalline silicon according to claim 11, characterized in that, The particle size of the granular polycrystalline silicon product is 600~6000μm.

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