Summary
Silicon carbide micropowder is a kind of superhard material. It is widely used as an abrasive or filler in ceramic refining abrasives, resin polishing wheels and diamond polishing wheels. Due to its high hardness, high strength, good resistance to oxidation and wear resistance, SiC micropowder is also widely used in non-grinding applications such as refractory materials, functional ceramics and structural materials.
1. What is silicon carbide powder?
Silicon carbide powder is a superhard material, as an abrasive or filler which has been widely used in the ceramic abrasive grinding, polishing resin, and a diamond wheel polishing wheel and the like. Due to its high hardness, high strength, good resistance to oxidation and wear resistance, SiC micropowder is also widely used in non-grinding applications such as refractory materials, functional ceramics and structural materials.
Silicon carbide powder
Silicon carbide itself has a high hardness, and its particle size distribution must reach a limited range. It is very difficult for the pulverization and classification of silicon carbide micropowder, and with the development of industrial production, scientific and technological progress and increasing market demand, carbonization The production of silicon micropowders places higher demands on things such as high productivity, low energy consumption, narrow particle size distribution and low pollution.
2. What is airflow crushing and grading technology?
Airflow pulverization and grading technology is an ultra-fine pulverization technology that has developed rapidly in recent years. It has the advantages of large pulverization strength, fine particle size, narrow distribution, and low product pollution. It is prepared in medicine, chemical raw materials and special powders. The aspect has been widely used.
Chuyou QF series airflow mill (airflow mill)
(1) Airflow crushing
The principle of jet pulverization is to pulverize particles by impact collision, friction, and shear between particles or between particles and particles under the action of a high-speed air stream. Airflow crushing has the following characteristics:
1 high-speed airflow will produce high speed on the particles, the impact strength of the particles is large, and ultra-fine powders of micron or even sub-micron level can be obtained;
2 granule products have high purity and low pollution;
3 The obtained product has a narrow particle size distribution, a smooth particle morphology and good particle dispersibility;
4 The airflow from the nozzle is reduced due to the throttling effect and can be used to pulverize heat sensitive materials.
(2) Airflow classification
Principle of airflow classification: Under the action of fan suction, the material is moved from the lower end of the classifier to the classification zone with the ascending airflow at high speed. Under the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated and meet the particle size requirements. The fine particles are collected into the cyclone or the Dust Collector through the gap of the grading wheel blades. The velocity of the fine particles entrained in the coarse particles collides with the wall, and the velocity disappears along the wall of the cylinder to the secondary air outlet, and the strong flushing action of the secondary air makes the fine particles The coarse and fine particles are separated, the fine particles are raised to the classification zone for secondary classification, and the coarse particles are lowered to the discharge port for discharge.
Air classifier
Due to its simple structure, the jet mill has no moving parts such as cutters and grinding discs, and it can operate safely and smoothly with high degree of automation. However, it is generally believed that the shortcomings of the airflow pulverizing equipment are high energy consumption and low energy utilization rate. Therefore, the airflow pulverizing and airflow grading equipment are usually used in combination, or the airflow pulverizer is provided with an airflow classifier, and the airflow grading device timely pulverizes the airflow. Qualified particles are separated, reducing over-grinding, increasing equipment productivity and energy efficiency, which is the gas classification and classification technique.
3. Application of airflow pulverization and classification technology in the production of silicon carbide micropowder
At present, the airflow pulverizing and grading equipment is an irreplaceable ultra-fine processing equipment in the silicon carbide micropowder industry. Taking the airflow pulverizer and the grading system as an example, the airflow pulverizing and grading process is as follows:
Silicon carbide micropowder airflow pulverization and classification process
(1) Influence of grading wheel and system air volume on silicon carbide micropowder products
According to the classification principle, it is obviously necessary to increase the speed of the grading wheel. The grading wheel speed determines the size of the centrifugal force field, and the size of the system affects the resistance of the granule. May have large centrifugal forces and minimal resistance.
In order to obtain accurate grading of silicon carbide micropowder, it is uneconomical to simply increase the speed of the grading wheel. It is also necessary to reasonably control the ratio of the auxiliary wind to the main air volume. When the system is operated with relatively small air volume, the grading wheel speed is adjusted to change the particle size more. Be sensitive. However, the reduction of the total air volume will lead to a reduction in the amount of processing, which is obviously uneconomical. Therefore, the system should be weighed against the pros and cons and choose the best working condition parameters.
(2) Effect of feeding mode and dispersion of raw materials on product performance
Commonly used vibrating feeding and screw feeders not only have poor uniformity and serious wear of the parts, but also agglomeration and agglomeration directly affect the classification effect. In the production, the combination of vibrating feeder + closing fan + long tube gas conveying can be adopted to ensure that the powder entering the classification chamber is uniformly and quantitatively fed. The tertiary air introduced by the graded outdoor jacket further assists in the dispersion of the fine powder, which makes the production operation stable, the worker is easy to operate, and at the same time ensures the quality of the product. At the same time, ensuring the proper gas-solid concentration of the raw materials and good dispersion is the key to improving the classification efficiency.
(3) Product performance
The silicon carbide micropowder product produced by the jet mill and the classification system can fully meet the particle size distribution requirements of the fine powder products such as W14, W10, W7 and WS in the GB/T 2477-83 standard used in the abrasive industry in China, and it can be used in Japan. The particle size distribution requirements of F1000, F1200, F2000 and other products in the JIS 86001-1987 industrial standard for abrasive abrasives are 80%.
4. Combination of online intelligent detection system and airflow pulverization and grading technology
Online detection of intelligent airflow smashing system
With the development of the on-line particle detection method and automatic control system, it can be combined with the airflow pulverization and grading system to track and monitor the particle size of the material in real time. The product granularity of the whole pulverization process is continuously detected, monitored and displayed by the online detector. And record, the control system automatically adjusts the pulverization and grading process parameters according to the fluctuation of the granularity to maximize product quality and system performance.
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