Better Quality Through Finer Milling
Several years ago, Eirich Machines Inc., based in Hardheim, Germany, introduced a new agitated media mill* to improve the efficiency of fine grinding operations. The mill has since been successfully used to grind glazes, frits, pigments, ferrites and a variety of hard ceramic substances, such as heavy spar, feldspar and quartz, to sizes as small as D97≥30 mm with a relatively high throughput. However, in today’s ceramic industry, increasingly smaller particle sizes are required to further enhance product quality.
To overcome this challenge, Eirich engineers decided to team up with Noll GmbH in Bobingen, Germany. The resulting technology combines the proven design of the agitated media mill with an advanced dynamic classifier** capable of efficiently handling even the finest ceramic powders.
System OperationIn the new combined system, the product is fed to the mill and reduced in size by a stirred bed of ceramic beads that transfer the milling energy through shear, impact and attrition forces. The finely ground material rises to the top of the mill’s rotating pan and is drawn into a negative pressure (vacuum) air stream that passes along the new classifier’s specially designed classifying wheel. The small particles enter the wheel while the coarse and agglomerated fines continue down to the coarse classifier. Here, turbulent air forces break up the agglomerates and transport them back to the classifier. The remaining coarse material is fed back into the agitated media mill, completing the cycle (see Figure 1).
Proving the New TechnologyTo prove the new technology, Noll acquired an agitated media mill from Eirich for its toll processing subsidiary in Cologne, Germany, and began running performance tests on the combined system in December 2002. The system met with immediate success, using less energy and requiring less time to produce extremely fine particle sizes compared to more expensive jet milling technologies (see Table 1). It also generated a higher throughput of material and was able to process coarser feed materials. Additionally, since very little time was needed for the machine to produce stable results, and since no excess material was required for start-up and cleaning, much less waste material was generated during the grinding operation—a feature that is especially important for high-cost materials. As a result, the system cost less to operate than conventional technologies. Based on these results, Eirich recently began installing a combined system in its technical laboratory in Hardheim.
Tests with the new technology are ongoing, but preliminary results have shown that the system can successfully be used to grind and classify zirconium dioxide, zircon silicate, marmor, glazes/frits, aluminium oxide, calcium carbonate, and titanium dioxide minerals and pigments. Trials have also successfully been performed with other materials.
A Fine SolutionProducers who have previously milled their products to very fine particle sizes in large quantities by wet or dry ball milling or in smaller quantities using jet milling can now use this new dry system to save time, energy and processing costs. Because the system uses ceramic and polymer linings and construction parts, it is especially suited for the metal-free processing of ceramic raw materials, minerals, frits and glazes. Additionally, the specially designed classifier wheel allows for higher throughputs and sharper top cuts in the finest size range. Through this technology exchange, ceramic manufacturers can achieve new possibilities in powder processing.
References:*The MaxxMill®, developed and supplied by Eirich Machines Inc. (U.S.) and Maschinenfabrik Gustav Eirich GmbH & Co KG (Germany).
**The MultiNo®-SE, developed and supplied by Noll GmbH.
For more information:For more information about this combined milling/classifying system, contact:
• Maschinenfabrik Gustav Eirich GmbH & Co KG, Wallduerner Str. 50, 74736 Hardheim,