Ultrafine powder preparation and classification technology

There are many methods for preparing ultrafine powders, which are usually divided into chemical synthesis and physical crushing methods based on the principle of their preparation. The chemical synthesis method is to obtain powders through chemical reactions, from ions, atoms, etc. through nucleus formation and growth. The ultrafine powders prepared by the chemical method have the advantages of small particle size, narrow particle size distribution, good particle shape and high purity, but the disadvantages are low output, high cost and complex process; the physical crushing method is to crush the material by mechanical force.
The advantages of mechanical crushing are large output, low cost and simple process, which is suitable for large-scale industrial production. Moreover, the mechanochemical effect is produced during the crushing process, which can increase the activity of the powder. Among them, the roller press is used in combination with the ball mill, which can be applied to large-scale industrial production, and the product particle grading is good and the activity is high. The air flow mill is also widely used in some special fields due to its better product performance.

The classification of ultrafine powders is based on the different movement trajectories of particles of different particle sizes in the medium under the action of centrifugal force, gravity, inertial force, etc., so as to achieve the separation of particles of different particle sizes and enter their respective collection devices.
When using pulverizing equipment for ultrafine pulverization, the forces acting on different particles are not uniform, and often only part of the powder meets the particle size requirements. If the products that have met the requirements cannot be separated out in time, the materials will be over-crushed, and this part of the powder will also agglomerate due to the small particle size, thereby reducing the pulverization efficiency. Therefore, timely use of ultrafine classifiers to effectively classify the crushed products can avoid over-crushing of materials, improve pulverization efficiency and reduce energy consumption. Ultrafine grading is generally divided into dry and wet types according to the different media used. Wet grading uses liquid as the dispersion medium, with high grading accuracy and good uniformity. However, wet grading has a series of subsequent operation problems such as drying and wastewater treatment, which limits its development. Dry classification is to classify powders by gravity field, inertial force field or centrifugal force field, mostly pneumatic classification. With the extensive application of high-speed mechanical impact and air flow pulverizers, dry classification has also been vigorously developed.

With the continuous expansion of the application field of ultrafine powders, the performance requirements of ultrafine powders in various fields are getting higher and higher, and the traditional preparation methods can no longer meet the current technical requirements. This is mainly reflected in:
1) The traditional single ultrafine powder equipment has low production capacity, high energy consumption, low resource utilization, and easy to cause pollution.
2) The uniformity and dispersibility of the prepared ultrafine powders are poor, and the agglomeration problem is serious, which reduces the product performance.
3) The equipment technology is backward, the research progress of the crushing machinery theory is slow, and there is a lack of new equipment for independent innovation.
4) The scale of the enterprise is small, the systematization and automation level of the production line is low, and the industry lacks stamina.
To this end, our company has made a lot of improvements and innovations in the existing ultrafine powder preparation technology, and has also achieved some research results.