Ultrafine dry grinding and wet
For the production of fine particles in the submicron range far, without exception, the mill media with agitation in a liquid phase is a success. Submicron particle size of 100 microns few can be obtained either wet or dry, while over the millimeter-sized particles are mainly produced by dry grinding. The choice between dry and wet milling is influenced by several factors. The state of the raw material and downstream use, such as powder or paste determined the grinding process in many cases. Other topics such as the fineness of the product, the dispersion of chemical reactivity hazards and should be considered
The performance of the dry milling process has been extended to more subtleties in the past years, including improving technology classifier. However, technology such as plants has great potential to contribute to dry fine particles. One approach is remarkably high energy dry mills, which use very little means of grinding media similar well-known wet mills.
The grinding may appear in a different form, size, and a wide variety of materials. Stones, balls, rods, cylpebs, pearls and irregular grains are the most common forms. The range of media sizes were approximately 100 mm to 50 microns. With the rise of entry requirements on the physical properties of the media become important. Hardness, strength and Young's modulus, but also the thermal and chemical stability must be considered. The high-tech ceramic materials such as zirconia or silicon nitride are examples for the development of traditional media to the media Flintstone high performance.
Stress particles in the media mill is carried out by the impact forces, pressure and shear between the media grinding against each other and the parties mill. According to the mill, one of these stress forces can be dominant in the grinding mechanism.
Compared to the wet mills, the dry agitated media mills are usually operated in a vertical arrangement with the media pressure and a relatively low speed. Thus, the stress on the particles in these plants are mainly created by shearing and pressing forces. Tumbling ball mills can operate at different speeds, which has an influence on the part of the impact and shear stress. Mills in their high-frequency vibration is dominated by vertical mill, while the centrifugal plants are more likely to shear and pressure stressing. As tumbling ball mills, planetary mills media create different movements depending on the rotation of the drum and the center wheel.