The performance in all media mills is dependent on using the correct media type, size and mill loading. New high performance beads have not only improved mill efficiency but also reduced wear on the beads and equipment. Improved performance and long life easily justify the higher costs associated with these higher performance beads.
Media available to meet all applications:
Glass - 2.5 sg
Zirconium Silica ER120 Zirpro - 3.8 sg
Cerium stabilized zirconia - Zirmil CE - 6.2 sg
Yttrium stabilized zirconia – Zirmil Y - 6.0 sg
YTZ – Tosoh 6.0 sg
Steel Balls - 7.2 sg
Media selection is based on the finest of particle required and viscosity of the product being milled. The smaller the bead the greater number of beads in a given volume and the greatest potential for yielding a very fine particle. With higher viscosity products the smaller bead may not be possible to use.
Considerations when selecting grinding media will have overlapping benefits.
1. Dispersion or de-agglomeration or the separation of bound aggregates or agglomerates that yield individual finite particles.
2. Milling and grinding where finite particles are reduced to a more desirable size.
3. Larger beads will have greater impact, which will accelerate reduction rates, while smaller beads, having a greater count per volume, providing excellent dispersion and particle polishing forces.
4.The rheological properties are considered. What bead mass is required to move media efficiently in the product being processed. High viscosity pastes will necessitate the need for heavier ceramic beads in larger sizes. Relatively thin or low viscosity (less than 5000 cps) can normally be dispersed using smaller and possibly less dense media. Bead density and agitator rotational speed can control product quality and possibly avoid over milling on shear sensitive products.
5. The composition of the bead is considered and abrasiveness of the product. Thin low viscosity, low solid materials that exhibit little or no lubricity or inter-particle hydraulic protection may have excessive media and component wear.
6. Product purity may dictate which media will be compatible.
New advances in ceramic grinding media provide many manufacturing benefits and justify the higher bead cost. Higher density, increased hardness, smoother surfaces, and uniform bead size provide long bead life and low wear on equipment. These characteristics will help when milling with smaller diameter beads, typically less than 1 mm diameter.
Contact EMImills to discuss your application and media selection. sales@EMImills.com
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