A method and system for preparing silicon carbide micropowder

Abstract

This application provides a method and system for preparing silicon carbide micro powder. In this method and system, the pretreatment and crushing of silicon carbide raw materials facilitates the crushing process of a composite pulverizer. Under the mode of mechanical shear crushing as the main method and high-speed airflow assisted crushing, the operating current is 65-75A and the air volume is 40-50m³. 3 The coordinated setting of a speed of 2600-3300 rpm / min and a classifying rotation speed of 2600-3300 rpm / min ensures the stable production of silicon carbide micropowder with a median particle size (d50) strictly within a narrow range of 9.5-11.5 μm and a concentrated particle size distribution. Furthermore, the mechanical shearing pulverization-high-speed airflow assisted pulverization method reduces wear on the equipment, and all parts in contact with silicon carbide are made of non-metallic wear-resistant materials, eliminating the introduction of metallic impurities such as iron and chromium at the source. This ensures extremely high chemical purity of the silicon carbide micropowder while achieving high production volume.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide micro powder processing technology, and relates to a method and system for preparing silicon carbide micro powder. Background Technology

[0002] Silicon carbide possesses excellent properties such as high hardness, high thermal conductivity, and resistance to chemical corrosion, and is widely used in fields such as grinding and polishing, advanced refractory materials, and ceramic reinforcement.

[0003] Currently, the main methods for preparing silicon carbide micro powder are mechanical pulverization methods such as ball milling and vibratory milling. However, mechanical pulverization methods have the following drawbacks: (1) Equipment wear and pollution: Silicon carbide has extremely high hardness. Under long-term mechanical crushing, traditional steel grinding media and liners wear out severely, resulting in the mixing of metal impurities such as iron and chromium into the powder, reducing the purity of the product. (2) High energy consumption and low efficiency: Simple mechanical pulverization has low energy utilization and it is difficult to avoid the phenomenon of "over-pulverization", which generates a large amount of non-target fine powder, increasing the classification load and energy consumption. (3) Difficult particle size control: Pulverization and classification are mostly independent processes with long flow and easy fluctuations in particle size distribution. (4) Dust pollution: Traditional open or semi-open pulverization and screening processes are prone to dust emission, affecting the working environment. Although air jet mills can solve the above-mentioned wear and purity problems, the single-machine processing capacity is limited, and the requirements for feed particle size are strict, resulting in high operating costs.

[0004] Therefore, there is an urgent need for a silicon carbide micropowder preparation technology that can take into account high efficiency, high purity, excellent particle size control, and environmental friendliness. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for preparing silicon carbide micro powder, so as to solve the problem that the particle size distribution of silicon carbide micro powder prepared by existing methods is large.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this application provides a method for preparing silicon carbide micro powder, the method comprising: The silicon carbide raw material is crushed into silicon carbide particles with a particle size of ≤5mm and an elliptical or near-spherical particle ratio of ≥80%. The silicon carbide particles are crushed by collision under biaxial mechanical shearing and airflow, and then silicon carbide micro powder is obtained by vortex classification.

[0007] In a second aspect, this application provides a silicon carbide micro powder preparation system, implementing the preparation method in the first aspect; the preparation system includes: a pretreatment crusher, a composite pulverizer, a vortex air classifier, and a cyclone collector connected in sequence, and the composite pulverizer and the vortex air classifier are each connected to a fan.

[0008] The present invention has the following beneficial effects: (1) Pre-treatment and crushing of silicon carbide raw materials can produce silicon carbide particles with a particle size of ≤5mm and an elliptical or near-spherical particle ratio of ≥80%, which facilitates the crushing process of the composite pulverizer.

[0009] (2) Under the main mechanical shearing and crushing method with high-speed airflow as the auxiliary crushing method, the working current is 65-75A and the air volume is 40-50m³. 3 With the combined setting of speed and classification rotation speed of 2600-3300 rpm / min, silicon carbide micro powder with median particle size d50 strictly within the narrow range of 9.5-11.5 μm and concentrated particle size distribution can be stably obtained.

[0010] (3) Mechanical shearing and high-speed airflow assisted crushing reduces the wear on the equipment, and the parts in contact with silicon carbide are made of non-metallic wear-resistant materials, which eliminates the introduction of metal impurities such as iron and chromium from the source, and ensures the extremely high chemical purity of silicon carbide micro powder while achieving high output. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the silicon carbide micro powder preparation system provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the composite pulverizer provided in the embodiments of this application; Symbolic representation: 01-Pre-treatment crusher, 02-Composite pulverizer, 03-Vortex air classifier, 04-Cyclone collector, 05-Fan; 1-Shell, 2-Stirring shaft, 3-Air inlet nozzle, 4-Feed inlet, 5-Discharge outlet, 6-Filter screen, 7-Elastic support rod, 8-Cleaning mechanism, 9-Grinding chamber, 10-Air inlet, 11-Z-shaped lever, 12-Drive cylinder. Detailed Implementation

[0012] In a first aspect, embodiments of this application provide a silicon carbide micro powder preparation system. This system includes a pretreatment crusher 01, a composite pulverizer 02, a vortex air classifier 03, and a cyclone collector 04 connected in sequence. Both the composite pulverizer 02 and the vortex air classifier 03 are connected to a fan 05, as shown in the attached diagram. Figure 1 As shown.

[0013] In this embodiment, the pre-processing crusher 01 is a component for crushing silicon carbide raw materials. It can be crushed by a jaw crusher or a double roll crusher alone, or by connecting the jaw crusher and the double roll crusher in series, so as to crush the silicon carbide raw materials into silicon carbide particles with a particle size ≤5mm and an elliptical or near-spherical particle ratio ≥80%.

[0014] The composite pulverizer 02 is a component for pulverizing silicon carbide particles. It includes a housing 1, a stirring shaft 2 arranged parallel to the inside of the housing 1, an air inlet nozzle 3 communicating with the inside of the housing 1, and a feed inlet 4 and a discharge outlet 5, both located at the top of the housing 1, as shown in the attached diagram. Figure 2 As shown.

[0015] Specifically, the shell 1 is hollow, forming a grinding chamber 9. Two vertically parallel stirring shafts 2 are arranged inside the grinding chamber 9, each with multiple stirring blades. The mounting plane of the stirring blades forms a non-zero angle with the axis of the stirring shaft 2. Driven by a motor, the two stirring shafts 2 rotate relative to each other, thereby generating three-dimensional shearing and compressive forces on the silicon carbide particles through the stirring blades on the stirring shafts 2, achieving the grinding of the silicon carbide particles. Preferably, the mounting angle of the stirring blades is 15°.

[0016] The bottom of the housing 1 is provided with an air inlet 10, and multiple air inlet nozzles 3 are provided at the air inlet 10. The air inlet 10 is connected to the inside of the crushing chamber 9 and the high-pressure air intake device, so that the high-pressure air intake device can inject compressed air of 0.6-0.8MPa into the crushing chamber 9 through the air intake nozzles 3 to form a high-speed airflow. This high-speed airflow can form a high-speed airflow field in the crushing chamber 9, so that the silicon carbide particles can gain acceleration kinetic energy and achieve high-speed collision crushing between particles. Thus, while the stirring blades mechanically crush the silicon carbide particles, the high-speed airflow assists in crushing the silicon carbide particles, which greatly improves the crushing efficiency, reduces the direct force on the equipment, and extends the service life of the equipment.

[0017] In addition, a filter screen 6 is provided horizontally between the top of the stirring shaft 2 and the discharge port 5. The filter screen 6 is used to perform preliminary screening of the crushed material, so that silicon carbide micro powder with a particle size of less than 12μm is discharged with the airflow, while the coarser particles are retained in the crushing chamber 9 for further crushing.

[0018] To prevent the filter screen 6 from clogging, an elastic screening device is integrated at the discharge end. Specifically, this elastic screening device includes an elastic support rod 7 and a cleaning mechanism 8. The elastic support rod 7 is disposed outside the housing 1, with one end fixed to the outer wall of the housing 1 and the other end passing through the housing 1 and extending into the interior, connecting to the frame of the filter screen 6, thereby providing elastic support for the filter screen 6. The cleaning mechanism 8 is located at the end of the elastic support rod 7 after it passes through the housing 1. This cleaning mechanism 8 is located inside the housing 1, below the filter screen 6, and close to one side of the filter screen 6. Preferably, in this embodiment, the elastic support rod 7 is four stainless steel spring rods.

[0019] Specifically, the cleaning mechanism 8 includes a Z-shaped lever 11 and a drive cylinder 12. One end of the Z-shaped lever 11 is connected to the piston rod of the drive cylinder 12, and the other end is close to the frame of the filter screen 6. Driven by the drive cylinder 12, the Z-shaped lever 11 can swing periodically, such as 10 times per minute, and gently tap the frame of the filter screen 6 to generate micro-vibrations, thereby shaking off the attached particles and preventing the filter screen from clogging.

[0020] In this embodiment, a current control unit is provided on the housing 1, which is used to control the operating current of the motor to be stable at 65-75A. Furthermore, the components that come into contact with silicon carbide, such as the stirring shaft 2, stirring blades, filter screen 6, and classifying wheel of the vortex air classifier 03, are all made of tungsten carbide or engineering ceramics to improve wear resistance and service life, while preventing the introduction of metal impurities.

[0021] The vortex air classifier 03 is a component for screening silicon carbide micro powder, and its inlet is connected to the outlet 5 of the composite pulverizer 02. The vortex air classifier 03 adopts a commonly used vortex air classifier in this field, and its internal components include a classifying wheel and a speed regulating device for controlling the speed of the classifying wheel. An airflow of 40-50 m³ / h is introduced into the vortex air classifier 03. 3 A high-speed airflow of 2600-3300 rpm / min is used. The speed of the classifying wheel is infinitely adjustable within the range of 2600-3300 rpm / min by a speed regulating device to balance the centrifugal force and airflow drag force, thereby accurately separating silicon carbide micro powder of different particle sizes. Finally, silicon carbide micro powder with a median particle size d50 of 9.5-11.5 μm is collected by cyclone collector 04.

[0022] To provide high-speed airflow to the composite pulverizer 02 and the vortex air classifier 03, both are connected to a fan 05. Airflow controllers are installed between the composite pulverizer 02 and the fan 05, and between the vortex air classifier 03 and the fan 05. These airflow controllers control the amount of airflow entering the composite pulverizer 02 and the vortex air classifier 03, maintaining the system under negative pressure to ensure the effective conveying and classification of silicon carbide while preventing dust overflow.

[0023] Furthermore, a pressure sensor is installed at the air outlet of the cyclone collector 04. Based on the feedback from the pressure sensor, the air volume controller automatically adjusts the system inlet to a slight negative pressure of approximately -200Pa.

[0024] On the other hand, embodiments of this application also provide a method for preparing silicon carbide micro powder, the method comprising: S01: The silicon carbide raw material is crushed into silicon carbide particles with a particle size ≤5mm and an elliptical or near-spherical particle ratio ≥80% using a pre-treatment crusher 01. The crushed silicon carbide particles are then fed into a composite pulverizer 02. This particle size and shape of the silicon carbide particles facilitate the composite pulverizer 02 in pulverizing the silicon carbide particles into silicon carbide micro powder with a median particle size d50 of 9.5-11.5μm.

[0025] S02: The silicon carbide particles are crushed by collision under biaxial mechanical shearing and airflow, and then silicon carbide micro powder is obtained by vortex classification.

[0026] In the composite pulverizer 02, two parallel stirring shafts apply a three-dimensional biaxial mechanical shearing force to the silicon carbide particles to pulverize them. Simultaneously, a high-speed airflow is introduced into the composite pulverizer 02. Driven by this high-speed airflow, the silicon carbide particles collide with each other and with the stirring shafts, further pulverizing the silicon carbide particles and forming a gas-solid mixture. In this embodiment, the operating current of the biaxial mechanical shearing is 65-75A; the airflow volume of the high-speed airflow is 40-50m³. 3 / min, to form a stable gas-solid two-phase flow field.

[0027] During the process of crushing silicon carbide particles in the composite pulverizer 02, a filter screen 6 with a pore size of less than 12μm is set at the discharge port 5 to screen the crushed material so that the silicon carbide micro-pulverized airflow with a particle size of less than 12μm is discharged, while the larger silicon carbide particles remain in the composite pulverizer 02 for further crushing.

[0028] The gas-solid mixture formed in the composite pulverizer 02 is introduced into the vortex gas separator. The rotation speed of the classifying wheel in the vortex gas separator is adjusted to 2600-3300 rpm / min, and the air volume is adjusted to 40-50 m³ / min. 3 The flow rate is 9.5-11.5 μm to separate and collect silicon carbide micro powder with a median particle size d50 from the gas flow. Coarser or finer particles are discharged from the coarse powder port or secondary fine powder port of the vortex gas separator and can be recycled or used as different grades of silicon carbide micro powder as needed.

[0029] The preparation method of the present invention will be further explained and illustrated below through specific embodiments.

[0030] Example 1 This application provides a method for preparing silicon carbide micro powder, the method comprising: S101: The silicon carbide raw material is crushed into silicon carbide particles with a particle size of 4mm and an elliptical or near-spherical particle ratio of ≥80% by using a pre-treatment crusher 01, and the crushed silicon carbide particles are then fed into the composite pulverizer 02.

[0031] S102: Start the motor, control the operating current of the stirring shaft to 70A, and the airflow of the high-speed airflow to 45m³ / h. 3 The speed is adjusted to 3000 rpm / min to pulverize silicon carbide particles using the composite pulverizer 02. The gas-solid mixture containing silicon carbide micropowder, after preliminary classification by filter 6, is introduced into a vortex gas separator. The speed of the classifying wheel in the vortex gas separator is adjusted to 3000 rpm / min, and the air volume to 45 m³ / min. 3 The flow rate is increased to facilitate the separation and collection of silicon carbide microparticles with a median particle size d50 of 9.5-11.5 μm from the gas flow.

[0032] Example 2 This application provides a method for preparing silicon carbide micro powder, the method comprising: S201: The silicon carbide raw material is crushed into silicon carbide particles with a particle size of 3mm and an elliptical or near-spherical particle ratio of ≥80% by a pre-treatment crusher 01, and the crushed silicon carbide particles are then fed into the composite pulverizer 02.

[0033] S202: Start the motor, control the operating current of the stirring shaft to 65-75A, and the airflow of the high-speed airflow to 40m³ / h. 3 The speed is adjusted to 3300 rpm / min to pulverize silicon carbide particles using the composite pulverizer 02. The gas-solid mixture containing silicon carbide micropowder, after preliminary classification by filter 6, is introduced into a vortex gas separator. The rotation speed of the classifying wheel in the vortex gas separator is adjusted to 3300 rpm / min, and the air volume to 40 m³ / min. 3 The flow rate is increased to facilitate the separation and collection of silicon carbide microparticles with a median particle size d50 of 9.5-11.5 μm from the gas flow.

[0034] Example 3 This application provides a method for preparing silicon carbide micro powder, the method comprising: S301: The pre-treatment crusher 01 is used to crush the silicon carbide raw material into silicon carbide particles with a particle size of 2mm and an elliptical or near-spherical particle ratio of ≥80%, and the crushed silicon carbide particles are fed into the composite pulverizer 02.

[0035] S302: Start the motor, control the operating current of the stirring shaft to 65-75A, and the airflow of the high-speed airflow to 50m³ / h. 3 The speed is adjusted to 2600 rpm / min to pulverize silicon carbide particles using the composite pulverizer 02. The gas-solid mixture containing silicon carbide micropowder, after preliminary classification by filter 6, is introduced into a vortex gas separator. The speed of the classifying wheel in the vortex gas separator is adjusted to 2600 rpm / min, and the air volume is 50 m³ / min. 3 The flow rate is increased to facilitate the separation and collection of silicon carbide microparticles with a median particle size d50 of 9.5-11.5 μm from the gas flow.

[0036] After testing the silicon carbide micro powder prepared in Examples 1-3, the median particle size d50 of the silicon carbide micro powder was 9.5-11.5 μm, the particle size distribution was narrow, the Fe content was less than 120 ppm, the production efficiency was increased by about 40% compared with the traditional ball milling-classification process, and the energy consumption per unit product was reduced by about 25%.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing silicon carbide micro powder, characterized in that, include: The silicon carbide raw material is crushed into silicon carbide particles with a particle size of ≤5mm and an elliptical or near-spherical particle ratio of ≥80%. The silicon carbide particles are crushed by collision under biaxial mechanical shearing and airflow, and then silicon carbide micro powder is obtained by vortex classification.

2. The method for preparing silicon carbide micro powder according to claim 1, characterized in that, The operating current of the twin-shaft mechanical shear is 65-75A, and the airflow volume is 40-50m³. 3 / min.

3. The method for preparing silicon carbide micro powder according to claim 1, characterized in that, The vortex classifier operates at a speed of 2600-3300 rpm / min and an air volume of 40-50 m³ / min. 3 / min.

4. The method for preparing silicon carbide micro powder according to claim 1, characterized in that, The silicon carbide micro powder has a particle size of 9.5-11.5 μm.

5. A silicon carbide micro powder preparation system, characterized in that, The preparation method described in any one of claims 1-4 is implemented; the preparation system comprises: a pretreatment crusher (01), a composite pulverizer (02), a vortex air classifier (03), and a cyclone collector (04) connected in sequence, and the composite pulverizer (02) and the vortex air classifier (03) are respectively connected to a blower (05).

6. The silicon carbide micro powder preparation system according to claim 5, characterized in that, The composite pulverizer (02) includes a housing (1), a stirring shaft (2) arranged parallel inside the housing (1), an air inlet nozzle (3) communicating with the inside of the housing (1), and a feed inlet (4) and a discharge outlet (5) both located at the top of the housing (1); the two stirring shafts (2) rotate relative to each other; the stirring shaft (2) is provided with multiple stirring blades, and the mounting plane of the stirring blades forms a non-zero angle with the axis of the stirring shaft (2).

7. The silicon carbide micro powder preparation system according to claim 6, characterized in that, A filter screen (6) is provided between the top of the stirring shaft (2) and the discharge port (5); an elastic support rod (7) is provided on the outside of the housing (1), and the elastic support rod (7) extends to the top of the housing (1) and connects to the filter screen (6); a cleaning mechanism (8) is provided at the end of the elastic support rod (7) inside the housing (1), and the cleaning mechanism (8) is located below the filter screen (6).

8. The silicon carbide micro powder preparation system according to claim 7, characterized in that, The cleaning mechanism (8) includes a Z-shaped lever (11) and a drive cylinder (12) connected together. The end of the Z-shaped lever (11) is close to the filter screen (6) and periodically taps the filter screen (6).

9. The silicon carbide micro powder preparation system according to claim 7, characterized in that, The stirring shaft (2), the stirring blades, the filter screen (6), and the classifying wheel of the vortex air classifier (03) are all made of tungsten carbide or engineering ceramics.

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