Dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials and its preparation method

Abstract

A dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials and its preparation method are disclosed, comprising: a reaction cylinder, a dynamic stirring mechanism, and a swirling gas distributor. The reaction cylinder is equipped with a solid material inlet, a gas outlet, and a heater. The dynamic stirring mechanism includes: a connecting seat, a stirring shaft rotating sealed within the connecting seat, a servo-driven geared motor driving the stirring shaft, and a stirring paddle fixed at the upper end of the stirring shaft. The swirling gas distributor includes a gas distribution sleeve coaxially arranged with the stirring paddle and a branch arm connected to the upper end of the gas distribution sleeve. The branch arm is inclined upward and its root is connected to the gas distribution sleeve. Detachable upper nozzles are spaced apart on the upper side wall of the branch arm, and detachable lower nozzles are spaced apart on the lower side wall of the branch arm. Gas outlet holes communicating with the distribution sleeve are evenly distributed around the circumference of the stirring shaft. A central shaft hole communicating with the gas outlet holes is provided in the stirring shaft. This invention can eliminate dead zones and improve the efficiency and quality of fluidized reaction.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation equipment technology, and in particular to a dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials and its preparation method. Background Technology

[0002] Silicon-carbon materials, with their ultra-high theoretical specific capacity of silicon (4200 mAh / g) and the excellent conductivity and volume stability of carbon materials, perfectly balance high energy density and cycle reliability. They not only reduce the volume expansion rate of silicon from 300% to below 50%, but also achieve an actual specific capacity of 1500-2500 mAh / g. They have become the core choice for the next generation of high-capacity lithium-ion battery anode materials and are regarded as key materials for promoting electric vehicle range to exceed 1000 kilometers and increasing the energy density of energy storage power stations by 50%. They have shown irreplaceable application prospects in the field of new energy.

[0003] In the industrial production of silicon-carbon materials, fluidized bed reactors combined with chemical vapor deposition (CVD) technology have become the mainstream technical approach due to their ability to achieve efficient gas-solid two-phase contact, continuous production, and uniform control of material properties. Compared to equipment such as fixed beds and rotary kilns, fluidized beds suspend and disperse carbon substrate particles through airflow, allowing them to fully react with silicon source (such as silane) and carbon source (such as acetylene) gases. The resulting silicon-carbon materials exhibit smaller coating thickness deviations, higher batch-to-batch capacity consistency, and higher daily capacity per unit, significantly reducing industrial production costs. Therefore, they are widely used in the large-scale production of silicon-carbon anodes and are rapidly iterated and upgraded to meet evolving process requirements.

[0004] However, during long-term operation of fluidized beds, engineering problems in the gas distributor region have consistently constrained material quality and production safety: in the CVD process of silicon-carbon preparation, silane ( High-temperature decomposition produces silicon particles and carbon sources (such as...) The cracking process generates carbon particles, which are ultrafine and easily deposited in the gas distributor channels. Initially, this leads to a reduction in channel cross-sectional area, a sharp increase in airflow resistance, and a deterioration in fluidization uniformity. After long-term operation, some channels become completely blocked, requiring shutdown for cleaning and resulting in energy loss. More importantly, the silicon and carbon layers deposited on the distributor surface are easily detached under the scouring or stirring action of the airflow, mixing into the silicon-carbon product and forming impurities. This leads to increased electrode interface impedance and shortened cycle life. In addition, differences in the thermal conductivity of local deposited layers can trigger a "hot spot effect," causing local temperatures to exceed the silane decomposition temperature. In extreme cases, this can lead to localized overheating within the reactor, posing a serious safety hazard.

[0005] To address the aforementioned issues, the commercially available and proven fluidized bed gas distributor employs a structure combining an annular inlet gas distributor with a bottom agitator. The annular slit design reduces the risk of channel blockage, while the agitator enhances gas-solid mixing through mechanical agitation, completely eliminating distributor blockage and significantly reducing product impurity content. However, practical experience shows that this structure still has limitations: the radial diffusion gradient of the annular inlet airflow is significant, resulting in suboptimal fluidization; furthermore, the fixed shear force of the agitator makes it unsuitable for silicon-carbon raw material particles with varying sizes, densities, and morphologies. With the increasing demand for high-capacity, long-cycle silicon-carbon materials and the growing urgency to improve the production capacity of single fluidized bed units, existing structures are no longer sufficient to meet the comprehensive requirements of "flow field uniformity, operational flexibility, and product adaptability." Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, which can effectively eliminate dead zones and ensure bed airflow density, and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, comprising: a reaction cylinder, a dynamic stirring mechanism, and a swirling gas distributor, wherein the reaction cylinder is provided with a solid material inlet, a gas outlet, and a heater;

[0008] The dynamic stirring mechanism includes: a connecting seat sealed at the bottom of the reaction cylinder, a rotating stirring shaft sealed in the connecting seat, a servo reduction motor that drives the stirring shaft, and a stirring paddle fixed at the upper end of the stirring shaft and located inside the reaction cylinder.

[0009] The swirling gas distributor includes a gas distribution sleeve coaxially arranged with the agitator and located below it, and a branch arm connected to the upper end of the gas distribution sleeve; the branch arm is inclined upward and its root is connected to the gas distribution sleeve; detachable upper nozzles are spaced apart on the upper side wall of the branch arm, and detachable lower nozzles are spaced apart on the lower side wall of the branch arm.

[0010] The stirring shaft has vent holes that are evenly distributed around its circumference and are connected to the gas distribution sleeve; the stirring shaft has a central shaft hole that is connected to the vent holes and is connected to the carrier gas source, silicon source process gas source and carbon source process gas source without interfering with the rotation of the stirring shaft.

[0011] Furthermore, in the aforementioned dynamic swirling fluidized bed for preparing silicon-carbon anode materials, the orifice diameters of the upper and lower nozzles in the swirling gas distributor range from 0.5 to 3 mm; the elevation angle between the upper nozzle and the horizontal line is 20° to 30°, and the depression angle between the lower nozzle and the horizontal line is 70° to 95°.

[0012] Furthermore, in the aforementioned dynamic swirling fluidized bed for preparing silicon-carbon anode materials, the stirring paddle of the dynamic stirring mechanism is a ribbon-frame composite structure. The ratio of the ribbon pitch to the diameter of the reaction cylinder is 1:1.2. The frame crossbar is perpendicular to the thread axis of the ribbon, and the gap between the frame crossbar and the inner wall of the reaction cylinder is ≤30mm. A radial shear flow is formed between the rotating support arm and the stirring paddle, which, together with the three-dimensional swirling field between the upper and lower nozzles, forms a composite dynamic steady flow field, enabling the material in the reaction cylinder to circulate axially.

[0013] Furthermore, in the aforementioned dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, the branch arms of the swirling gas distributor are evenly distributed in 4 to 8 groups along the circumference of the gas distribution sleeve. The axis of each group of branch arms forms an angle of 45° to 75° with the radial direction of the stirring shaft. The length of the branch arm is 1 / 3 to 1 / 2 of the diameter of the reaction cylinder, ensuring that the gas ejected from the upper nozzle covers more than 80% of the cross-section of the reaction cylinder.

[0014] Furthermore, in the aforementioned dynamic swirling fluidized bed for preparing silicon-carbon anode materials, a rotary joint is connected to the inlet end of the central shaft hole; the rotary joint is connected to a preheating furnace and a mixing tank in sequence through pipelines, and the mixing tank is connected to a carrier gas source, a silicon source process gas source and a carbon source process gas source, respectively.

[0015] Furthermore, in the aforementioned dynamic swirling fluidized bed for preparing silicon-carbon anode materials, the upper and lower nozzles are arranged alternately or aligned on the branch arm, and the elevation angle of the upper nozzle and the lower nozzle form a three-dimensional injection angle of 90° to 120°, so that the gas forms a spiral upward three-dimensional swirling field in the reaction chamber.

[0016] Furthermore, in the aforementioned dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, the reaction cylinder has at least two gas outlets, each equipped with a metal filter, a backflushing valve and a shut-off valve, a safety valve on the reaction cylinder, and a pressure gauge on the safety valve.

[0017] The method for preparing silicon-carbon anode materials uses the aforementioned dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, and its steps are as follows:

[0018] S1. Feeding and Pretreatment: Porous carbon particles with a particle size of 2-12 μm are added to the reaction cylinder through the solid material inlet. The static material level of the porous carbon particles is 2-4 times the inner diameter of the reaction cylinder. The solid material inlet is then closed. The dynamic stirring mechanism is started, and the stirring paddle rotates at a low speed of 10-20 r / min. At the same time, carrier gas is introduced through the cyclone gas distributor with an apparent gas velocity of 0.01-0.03 m / s to initially fluidize the porous carbon particles.

[0019] S2. Establish dynamic vortex: Gradually increase the speed of the agitator to 80-120 r / min, and simultaneously increase the carrier gas velocity to 0.04-0.12 m / s to form a stable vortex field; start the heater to make the temperature inside the reaction chamber reach 450-650℃ and maintain it for 10-30 min.

[0020] S3, Nano-silicon Deposition: Maintain stable swirling flow field parameters, open the silicon source process gas supply path, control the volumetric flow rate ratio of silicon source process gas to carrier gas to be 1:5 to 1:8, and adjust the overall apparent gas velocity to 0.04 m / s to 0.06 m / s; during the deposition process, the rotation speed of the stirring paddle is consistent with that of the stirring paddle in S2. Every 30 minutes, the rotation speed of the stirring paddle is finely adjusted by the servo reduction motor, with a speed adjustment range of ±10 r / min, to avoid local particle agglomeration. Stable operation for 4 to 8 hours yields silicon-carbon intermediate particles;

[0021] S4. Carbon Coating and Cooling: After adjusting the temperature inside the reaction chamber to the carbon coating temperature of 500-650℃, turn on the carbon source process gas and control the volumetric flow rate ratio of the carbon source process gas to the carrier gas to be 1:4-1:10. Adjust the overall apparent gas velocity to 0.035m / s-0.055m / s and reduce the stirring speed to 40-60r / min. Run the mixture stably for 2-6 hours to ensure that the carbon from the carbon source process gas is uniformly coated on the surface of the silicon-carbon intermediate particles. After completion, turn off the carbon source process gas supply, gradually reduce the stirring speed until it stops, and allow it to cool naturally to room temperature to obtain the silicon-carbon anode material.

[0022] Furthermore, in the aforementioned method for preparing silicon-carbon anode materials, in S2, the criteria for judging a stable swirling flow field are: bed pressure drop pulsation amplitude ≤ 5%, uniform air intake at the upper and lower nozzles, and air velocities at both the upper and lower nozzles controlled between 25 and 45 m / s.

[0023] Furthermore, in the aforementioned method for preparing silicon-carbon anode materials, in S3 and S4, the gas velocity ratio between the upper and lower nozzles of the swirling gas distributor is 1.2 to 1.5:1, which, combined with the shearing force generated by the rotation of the stirring paddle, ensures that the conversion rate of the silicon source process gas is not less than 95% and the conversion rate of the carbon source process gas is not less than 20%.

[0024] The advantages of this invention are as follows: the upwardly inclined branch arm and the upper and lower nozzles on the branch arm allow the gas to be injected in a rotating manner. The lower nozzle blows the airflow downwards to cover the lower part of the reaction cylinder, effectively eliminating the dead zone at the bottom of the reaction cylinder. The upper nozzle blows the airflow upwards. The gas ejected by the rotating upper and lower nozzles forms a three-dimensional swirling flow field. This three-dimensional swirling flow field causes the airflow to form a multi-directional flow, enhancing bed turbulence within the reaction cylinder and improving fluidization efficiency. Meanwhile, the rotating agitator and the branch arm form a radial shear flow, which, combined with the multi-directional airflow, forms a composite dynamic flow field, breaking down large agglomerates, improving the efficiency of breaking down residual agglomerates, and ensuring the fluidization effect of the particles. The centrifugal force generated by the rotating airflow... This allows the gas to diffuse along the inner wall of the reaction chamber, preventing excessively high gas velocities in the central region and avoiding dead zones on the side walls that could lead to uneven gas distribution. When using reaction chambers of different sizes, simply adjusting the number of branch arms according to the inner diameter of the chamber ensures a uniform bed gas flow density and guarantees the fluidization reaction effect. During silica deposition and carbon coating, a sudden increase in gas velocity generates strong shear force that directly impacts the deposits on the inner wall of the reaction chamber, breaking the adhesion layer between the deposits and the inner wall and peeling off the deposits. Simultaneously, a sudden increase in the rotational speed of the agitator disrupts the original flow field balance in the reaction chamber, generating vortices and further improving the efficiency of deposit peeling. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the dynamic swirling stirred fluidized bed used for preparing silicon-carbon anode materials according to the present invention.

[0026] Figure 2 yes Figure 1 A schematic diagram of the middle connector. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0028] like Figure 1 , Figure 2As shown, the dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to the present invention includes: a reaction cylinder 1, a dynamic stirring mechanism, and a swirling gas distributor. The reaction cylinder 1 is provided with a solid material inlet 11, a gas outlet, and a heater 12. The reaction cylinder 1 has no less than two gas outlets. A metal filter 13 is provided in the gas outlet. A backflow valve and a shut-off valve are provided on the metal filter 13. The heater 12 is any one or more combinations of an electric heating furnace, a flue gas jacketed heater, an infrared heater, or an inductively coupled heater. A safety valve 14 is provided on the reaction cylinder 1, and a pressure gauge 141 is provided on the safety valve 14. Porous carbon particles can be added to the reaction chamber 1 through the solid material inlet 11, and the carrier gas and residual process gas can be discharged through the gas outlet. The metal filter 13 can filter out solid particles. When one metal filter 13 becomes blocked, the shut-off valve of another metal filter 13 is opened and the shut-off valve of the blocked metal filter 13 is closed. The backflush valve of the blocked metal filter 13 is opened for backflush. During backflush, the same gas as the carrier gas needs to be used and the gas is preheated. When the pressure gauge 141 on the safety valve 14 detects that the pressure in the reaction chamber 1 is too high, the shut-off valves on all metal filters 13 are opened first to increase the gas output and reduce the pressure in the reaction chamber 1. If the pressure in the reaction chamber 1 is still too high, the safety valve 14 needs to be opened to release the pressure.

[0029] The dynamic stirring mechanism includes a connecting seat 2 sealed at the bottom of the reaction cylinder 1. The connecting seat 2 includes a cylindrical sleeve 21, an I-shaped sleeve 22, and a bracket 23. The cylindrical sleeve 21 has a connected bearing hole and a heat conduction hole 211. Two bearings and two skeleton oil seals are installed in the bearing hole, with the two skeleton oil seals respectively positioned at the upper and lower ends of the two bearings. The side wall of the cylindrical sleeve 21 has a heat conduction inlet 212 and a heat conduction outlet 213 connected to the heat conduction hole 211, and extends into the heat conduction hole. Thermocouple 214 in hot hole 211 has a bearing hole in I-shaped sleeve 22, and a bearing and oil seal are also provided in the bearing hole. Cylindrical sleeve 21 abuts against I-shaped sleeve 22 and is connected by bolts. A first sealing ring is provided between cylindrical sleeve 21 and I-shaped sleeve 22. I-shaped sleeve 22 abuts against bracket 23 and is connected by bolts. Stirring shaft 3 passes through cylindrical sleeve 21 and I-shaped sleeve 22 and extends downward into bracket 23. Stirring shaft 3 is connected to cylindrical sleeve 21 and I-shaped sleeve 22. The bearings and the skeleton oil seal in the sleeve 22 are connected. A second bevel gear 31 is provided on the stirring shaft 3 that extends into the bracket 23. A servo geared motor 231 is provided on the outer wall of the bracket 23. The output shaft of the servo geared motor 231 extends into the bracket 23. A first bevel gear 232 is provided on the output shaft. The first bevel gear 232 meshes with the second bevel gear 31. The servo geared motor 231 drives the first bevel gear 232, which in turn drives the second bevel gear 31 and the stirring shaft through gear transmission. The stirring shaft 3 rotates, and the cylindrical sleeve 21 in the connecting seat 2 is connected to the reaction cylinder 1. The connection structure is as follows: the bottom of the reaction cylinder 1 is an open structure, an upper flange 15 is provided on the outer side wall of the reaction cylinder 1, a U-shaped cover 215 is sealed and welded on the outer side wall of the cylindrical sleeve 21, and a lower flange 216 is provided on the outer side wall of the U-shaped cover 215. The upper flange 15 and the lower flange 216 are connected by bolts, and a sealing gasket is provided between the upper flange 15 and the lower flange 216 to improve the sealing performance and prevent leakage.

[0030] The upper end of the stirring shaft 3 extends out of the cylindrical sleeve 21 in the connecting seat 2 and then into the reaction cylinder 1. A stirring paddle 32 and a swirling gas distributor coaxially located below the stirring paddle 32 are fixedly installed at the upper end of the stirring shaft 3. The stirring paddle 32 is a spiral ribbon-frame composite structure. The spiral ribbon 321 in the stirring paddle 32 extends along the axial direction of the stirring shaft 3. The ratio of the pitch of the spiral ribbon 321 to the diameter of the reaction cylinder 1 is 1:1.2. The frame-type crossbar 322 in the stirring paddle 32 is perpendicular to the thread axis of the spiral ribbon 321. The gap between the frame-type crossbar 322 and the inner wall of the reaction cylinder 1 is ≤30mm. During rotation, the frame-type crossbar 322 can quickly cut off the arch bridge structure and quickly establish initial fluidization in the reaction cylinder 1. Moreover, it can trigger a strong radial jet through the edge effect to prevent agglomerates from appearing on the inner wall of the reaction cylinder 1. The spiral ribbon 321 generates axial thrust to ensure stable expansion of the bed. The swirling gas distributor includes a gas distribution sleeve 33. A ceramic sealing ring 331 is slidably engaged between the gas distribution sleeve 33 and the cylindrical sleeve 21 of the connecting seat 2. Four to eight sets of upwardly inclined branch arms 34, with their roots connected to the gas distribution sleeve 33, are evenly distributed around the circumference of the gas distribution sleeve 33. The axis of each branch arm 34 forms an angle of 45° to 75° with the radial direction of the stirring shaft 3. The length of the branch arm 34 is 1 / 3 to 1 / 2 of the diameter of the reaction cylinder 1. Several detachable upper nozzles 341 are spaced apart on the upper sidewall of the branch arm 34, with an elevation angle α of 20° to 30° between the upper nozzles 341 and the horizontal line. Several detachable lower nozzles 342 are spaced apart on the lower sidewall of the branch arm 34, with a depression angle β of 70° to 95° between the lower nozzles 342 and the horizontal line. The upper nozzles 341 and lower nozzles 342 are arranged alternately or aligned on the branch arm 34. In this embodiment, a staggered arrangement is preferred, so that a stable three-dimensional spray angle of 90° to 120° can be formed between the upper nozzle 341 and the lower nozzle 342. The nozzles 341 and 342 have the same orifice diameter, which is 0.5 to 3 mm. The upper nozzle 341 and lower nozzle 342 with corresponding orifice diameters can be replaced according to the material characteristics. Several air outlets 35 are evenly distributed around the circumference of the stirring shaft 3 and are connected to the distribution sleeve 33. A central shaft hole 36 connected to the air outlets 35 is provided in the stirring shaft 3. A rotary joint 37 is connected to the inlet end of the central shaft hole 36. The rotary joint 37 is connected to the preheating furnace 4 and the mixing tank 5 in sequence through pipelines. The mixing tank 5 is connected to the carrier gas source 6 and the process gas source respectively. The process gas source is divided into silicon source process gas source 7 and carbon source process gas source 8. The rotary joint 37 can prevent the pipeline from interfering with the rotation of the stirring shaft 3. The carrier gas from carrier gas source 6 can be mixed with the silicon source process gas from silicon source process gas source 7 and the carbon source process gas from carbon source process gas source 8 in mixing tank 5. The carrier gas, silicon source process gas and carbon source process gas can be preheated by preheating furnace 4, and then enter the reaction cylinder 1 through the central shaft hole 36, gas outlet 35, distribution sleeve 33, branch arm 34, upper nozzle 341 and lower nozzle 342 in stirring shaft 3.

[0031] The upwardly inclined branch arm 34 and its upper nozzle 341 and lower nozzle 342 enable gas to be injected in a rotating manner. The upper nozzle 341 is set at an elevation angle of 20°–30°, and the length of the branch arm 34 is set to 1 / 3–1 / 2 of the diameter of the reaction cylinder 1. This ensures that the gas ejected from the upper nozzle 341 covers more than 80% of the cross-section of the reaction cylinder 1. The lower nozzle 342 is set at a depression angle of 70°–95°, causing the airflow to rotate and cover the lower part of the reaction cylinder 1, effectively eliminating the dead zone at the bottom of the reaction cylinder 1. The upper nozzle 341 and lower nozzle 342... The ejected gas forms a three-dimensional cross-flow network, creating a spiral upward three-dimensional swirling flow field within the reaction cylinder 1. This enhances bed turbulence within the reaction cylinder 1 and improves fluidization efficiency. The rotating agitator 32 and the branch arm 32 form a radial shear flow, which, together with the three-dimensional swirling flow field between the upper nozzle 341 and the lower nozzle 342, forms a composite dynamic steady flow field. This ensures that the axial circulation rate of the material within the reaction cylinder 1 is ≥0.5 m / s. Simultaneously, the centrifugal force generated by the rotating airflow allows the gas to diffuse along the inner wall of the reaction cylinder 1. This avoids excessively high gas velocity in the central region and prevents dead zones from forming on the side walls of the reaction cylinder 1, thus preventing uneven gas distribution. If the size of the reaction cylinder 1 is increased, in order to ensure that there are no dead zones in the reaction cylinder 1 and to ensure uniform gas distribution, the number of branch arms 34 needs to be adjusted according to the size of the reaction cylinder 1. When the inner diameter of the reaction cylinder 1 is ≤1m, four sets of branch arms 34 are symmetrically arranged on the distribution sleeve 33. When the inner diameter of the reaction cylinder 1 is between 1 and 2m, six sets of branch arms 34 are evenly distributed around the circumference of the distribution sleeve 33. When the inner diameter of the reaction cylinder 1 is ≥2m, eight sets of branch arms 34 are evenly distributed around the circumference of the distribution sleeve 33. The more branch arms 34 there are, the greater the number of upper nozzles 341 and lower nozzles 342, the greater the rotation intensity of the ejected airflow, and the greater the turbulence range of the airflow, thereby ensuring that a uniform bed airflow density is maintained in the reaction cylinder 1.

[0032] The method for preparing silicon-carbon anode materials uses the aforementioned dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, and its steps are as follows:

[0033] S1. Feeding and Pretreatment: Porous carbon particles with a particle size of 2-12 μm are fed into the reaction cylinder 1 through the solid material inlet 11. The solid material inlet 11 is closed. The static material level of the porous carbon particles is 2-4 times the inner diameter of the reaction cylinder 1. The dynamic stirring mechanism is started, and the stirring paddle 32 rotates at a low speed of 10-20 r / min. At the same time, the carrier gas is introduced through the cyclone gas distributor with an apparent gas velocity of 0.01-0.03 m / s to initially fluidize the porous carbon particles. After the air in the reaction cylinder 1 is replaced, the preheating furnace 4 is started to heat the carrier gas to 300℃.

[0034] S2. Establish dynamic swirling flow: Gradually increase the rotation speed of the agitator 32 to 80-120 r / min, and simultaneously increase the carrier gas velocity to 0.04-0.12 m / s to form a stable swirling flow field. Start the heater 12 to make the temperature inside the reaction cylinder 1 reach 450-650℃ and maintain it for 10-30 min.

[0035] In this step, the criteria for judging a stable swirling flow field are: bed pressure drop pulsation amplitude ≤5%, uniform air intake of upper nozzle 341 and lower nozzle 342, and air velocity of upper nozzle 341 and lower nozzle 342 controlled between 25 and 45 m / s.

[0036] S3. Nano-silicon deposition: Maintain stable swirling flow field parameters, open the silicon source process gas supply 7 passage, allowing the silicon source process gas and carrier gas to mix in the mixing tank 5 to form a mixed gas. Control the volumetric flow rate ratio of the silicon source process gas to the carrier gas to be 1:5 to 1:8, and adjust the overall apparent gas velocity to 0.04 to 0.06 m / s. Controlling the apparent gas velocity within this range maintains a fluidized state, preventing the deposition or excessive entrainment of nano-silicon particles formed by the decomposition of the silicon source process gas at high temperatures. This ensures uniform suspension of nano-silicon particles, promotes gas-solid mass transfer, and reduces bubble coalescence, thereby improving the uniformity of nano-silicon deposition. The mixed gas of silicon source process gas and carrier gas is sprayed from the upper nozzle 341 and the lower nozzle 342 into the reaction vessel. In cylinder 1, the multi-directional airflow formed by the rotating gas, combined with the mechanical shear force of the stirring paddle 32, forms a three-dimensional swirling field that evenly disperses the mixed gas in the reaction cylinder 1, thereby ensuring the uniform dispersion of the silicon source process gas. The three-dimensional swirling field also improves the contact efficiency between the silicon source process gas and the carbon substrate material. The silicon source process gas is decomposed at high temperature to form nano-silicon particles. The nano-silicon particles are chemically vapor-deposited with the porous carbon framework to form silicon-carbon intermediate particles. During the deposition process, the rotation speed of the stirring paddle 32 is consistent with that of the stirring paddle 32 in S2. Every 30 minutes, the rotation speed of the stirring paddle 32 is finely adjusted by the servo reduction motor 231, with a speed adjustment range of ±10 r / min, to avoid local particle agglomeration and ensure stable operation for 4 to 8 hours.

[0037] In this step, the high temperature of the reaction cylinder 1 will radiate to the stirring shaft 3, causing the temperature of the stirring shaft 3 to rise. When the temperature of the stirring shaft 3 rises to 450-600°C, the silicon source process gas in the mixed gas passing through the central shaft hole 36 will undergo high-temperature cracking in the central shaft hole 36, which is easy to adhere to the side wall of the central shaft hole 36 and cause blockage. In order to prevent this from happening, heat transfer fluid needs to be introduced into the heat transfer hole 211 of the cylindrical sleeve 21. The heat transfer fluid enters the heat transfer hole 211 from the heat transfer inlet 212 and then exits from the heat transfer outlet 213 to form a circulating heat transfer. Thermocouple 214 monitors the temperature of the heat transfer fluid in real time and needs to ensure that the temperature of the heat transfer fluid is 300°C. This will ensure that the temperature of the stirring shaft 3 is maintained at 300°C, thereby preventing the silicon source process gas from undergoing high-temperature cracking in the stirring shaft 3.

[0038] S4. Carbon Coating and Cooling: After adjusting the temperature inside the reaction cylinder 1 to the carbon coating temperature of 500-650℃, turn on the carbon source process gas to mix the carbon source process gas and the carrier gas in the mixing tank 5 to form a mixed gas. Control the volume flow ratio of the carbon source process gas to the carrier gas to be 1:4-1:10, and adjust the overall apparent gas velocity to 0.035m / s-0.055m / s. Reduce the speed of the stirring paddle 32 to 40-60r / min and run it stably for 2-6 hours. In a stable three-dimensional swirling field, the carbon formed by the cracking of the carbon source process gas is uniformly coated on the surface of the silicon-carbon intermediate particles. After completion, turn off the carbon source process gas source, gradually reduce the speed of the stirring paddle 32 until it stops, and allow it to cool naturally to room temperature to obtain the silicon-carbon anode material.

[0039] In this step, heat transfer fluid is needed to continue to conduct heat to the stirring shaft 3 to prevent the carbon source process gas from undergoing high-temperature cracking in the stirring shaft 3. Reducing the rotation speed of the stirring paddle 32 can prolong the residence time of the porous carbon particles, making the reaction more complete.

[0040] In S3 and S4, the gas velocity ratio of the upper nozzle 341 and the lower nozzle 342 is 1.2 to 1.5:1. Combined with the shearing force generated by the rotation of the agitator 32, the conversion rate of the silicon source process gas is not less than 95%, and the conversion rate of the carbon source process gas is not less than 20%. Every 2 hours, the gas velocity of the mixed gas needs to be increased by 5% instantaneously and then maintained for 5 minutes. The high gas velocity can generate strong shearing force, which directly impacts the deposits on the inner wall of the reaction cylinder 1, destroys the adhesion layer between the deposits and the inner wall, and peels off the deposits. Moreover, the inclined airflow blown out by the upper nozzle 341 and the lower nozzle 342 can enhance local turbulence and improve the scouring coverage. At the same time, the agitator 32 increases the stirring speed by 30% within 3 to 5 seconds. The instantaneous increase in rotation speed can break the original flow field balance in the reaction cylinder 1, generate vortices, and further improve the efficiency of peeling off the deposits. In S3 and S4, when the pressure difference of the mixed gas in the pipeline is greater than 2 kPa, it indicates that a blockage has occurred in the path of the mixed gas. At this time, the process gas source is shut off, and then the flow rate of the carrier gas is increased instantaneously to flush the path of the mixed gas through the high gas velocity. In order to monitor the pressure difference in the pipeline, a pressure difference sensor needs to be installed in the pipeline. In order to increase the flow rate of the carrier gas instantaneously, an accumulator is generally installed in the pipeline to store the carrier gas. The installation of pressure difference sensors and accumulators in the pipeline are existing technologies and will not be described in detail here.

[0041] In this embodiment, the carrier gas is either nitrogen or argon; the silicon source process gas is any one or more of silane, silane, hexamethyldisilane, chlorosilane, and tetrafluorosilane; and the carbon source process gas is any one or more of methane, ethane, ethylene, acetylene, and propylene.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials, characterized in that, include: The reactor includes a reaction cylinder, a dynamic stirring mechanism, and a swirling gas distributor. The reaction cylinder is equipped with a solid material inlet, a gas outlet, and a heater. The reaction cylinder has at least two gas outlets, each equipped with a metal filter, a backflow valve and a shut-off valve, and a safety valve with a pressure gauge. The dynamic stirring mechanism includes: a connecting seat sealed at the bottom of the reaction cylinder, a rotating stirring shaft sealed in the connecting seat, a servo reduction motor driving the stirring shaft, and a stirring paddle fixed at the upper end of the stirring shaft and located inside the reaction cylinder. The stirring paddle of the dynamic stirring mechanism is a ribbon-frame composite structure. The ratio of the ribbon pitch to the diameter of the reaction cylinder is 1:1.

2. The frame crossbar is perpendicular to the thread axis of the ribbon. The gap between the frame crossbar and the inner wall of the reaction cylinder is ≤30mm. The swirling gas distributor includes a gas distribution sleeve coaxially arranged with the agitator and located below it, and a branch arm connected to the upper end of the gas distribution sleeve; the branch arm is inclined upward and its root is connected to the gas distribution sleeve; detachable upper nozzles are spaced apart on the upper side wall of the branch arm, and detachable lower nozzles are spaced apart on the lower side wall of the branch arm. The stirring shaft has vent holes that are evenly distributed around its circumference and are connected to the gas distribution sleeve; the stirring shaft has a central shaft hole that is connected to the vent holes and is connected to the carrier gas source, silicon source process gas source and carbon source process gas source without interfering with the rotation of the stirring shaft.

2. The dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to claim 1, characterized in that: The orifice diameter of the upper and lower nozzles in the swirling gas distributor ranges from 0.5 to 3 mm; the elevation angle between the upper nozzle and the horizontal line is 20° to 30°, and the depression angle between the lower nozzle and the horizontal line is 70° to 95°.

3. The dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to claim 1, characterized in that: The swirling gas distributor has 4 to 8 sets of branch arms evenly distributed around the circumference of the gas distribution sleeve. The axis of each set of branch arms forms an angle of 45° to 75° with the radial direction of the stirring shaft, and the length of the branch arm is 1 / 3 to 1 / 2 of the diameter of the reaction cylinder.

4. The dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to claim 1, characterized in that: A rotary joint is connected to the inlet end of the central shaft hole; the rotary joint is connected to the preheating furnace and the mixing tank in sequence through pipelines, and the mixing tank is connected to the carrier gas source, the silicon source process gas source and the carbon source process gas source respectively.

5. The dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to claim 1, characterized in that: The upper and lower nozzles are arranged alternately or aligned on the branch arm, and the elevation angle of the upper nozzle and the lower nozzle form a three-dimensional injection angle of 90° to 120°, so that the gas forms a three-dimensional spiral flow field in the reaction tube.

6. A method for preparing silicon-carbon anode materials, characterized in that: The steps of using the dynamic swirling stirred fluidized bed for preparing silicon-carbon anode materials according to any one of claims 1 to 5 are as follows: S1. Feeding and Pretreatment: Porous carbon particles with a particle size of 2-12 μm are added to the reaction cylinder through the solid material inlet. The static material level of the porous carbon particles is 2-4 times the inner diameter of the reaction cylinder. The solid material inlet is then closed. The dynamic stirring mechanism is started, and the stirring paddle rotates at a low speed of 10-20 r / min. At the same time, carrier gas is introduced through the cyclone gas distributor with an apparent gas velocity of 0.01-0.03 m / s to initially fluidize the porous carbon particles. S2. Establish dynamic vortex: Gradually increase the speed of the agitator to 80-120 r / min, and simultaneously increase the carrier gas velocity to 0.04-0.12 m / s to form a stable vortex field; start the heater to make the temperature inside the reaction chamber reach 450-650℃ and maintain it for 10-30 min. S3. Nano-silicon deposition: Maintain stable swirling field parameters, open the silicon source process gas supply path, control the volumetric flow rate ratio of silicon source process gas to carrier gas to be 1:5 to 1:8, and adjust the overall apparent gas velocity to 0.04 m / s to 0.06 m / s; during the deposition process, fine-tune the speed of the stirring paddle every 30 minutes through the servo reduction motor, with a speed adjustment range of ±10 r / min, to avoid local particle agglomeration, and run stably for 4 to 8 hours to obtain silicon-carbon intermediate particles; S4. Carbon Coating and Cooling: After adjusting the temperature inside the reaction chamber to the carbon coating temperature of 500-650℃, turn on the carbon source process gas and control the volumetric flow rate ratio of the carbon source process gas to the carrier gas to be 1:4-1:

10. Adjust the overall apparent gas velocity to 0.035m / s-0.055m / s and reduce the stirring speed to 40-60r / min. Run the mixture stably for 2-6 hours to ensure that the carbon from the carbon source process gas is uniformly coated on the surface of the silicon-carbon intermediate particles. After completion, turn off the carbon source process gas supply, gradually reduce the stirring speed until it stops, and allow it to cool naturally to room temperature to obtain the silicon-carbon anode material.

7. The method for preparing silicon-carbon anode material according to claim 6, characterized in that: In S2, the criteria for judging a stable swirling flow field are: bed pressure drop pulsation amplitude ≤ 5%, uniform air intake at the upper and lower nozzles, and air velocity at both the upper and lower nozzles controlled between 25 and 45 m / s.

8. The method for preparing silicon-carbon anode material according to claim 6, characterized in that: In S3 and S4, the gas velocity ratio between the upper and lower nozzles of the swirling gas distributor is 1.2 to 1.5:

1. Combined with the shearing force generated by the rotation of the stirring paddle, the conversion rate of silicon source process gas is not less than 95%, and the conversion rate of carbon source process gas is not less than 20%.

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