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Powder & Bulk Solids, May 2014

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28 M a y 2 0 1 4 TechnicalExclusive M Miniaturization of Particles by Jet Milling with Superheated Steam Micronization is the miniaturization of particles by jet milling with compressed air or other gas to a range of 2-200 microns (µm). For most dry grinding processes, 2µm is the practical limit of the technol- ogy. Nanonization is the miniaturization of particles by jet milling with superheated steam. By using super- heated steam as the grinding gas, a fluidized bed jet mill with this technology can produce dry powders with median particle sizes in the range of 130 nano- meters (nm), with 100% of the distribution finer than 400 nm. This technology represents a quantum leap in par- ticle size reduction by a dry grinding process and im- proves the jet milling process ten-fold. This technol- ogy uses steam to produce superfine particles; hence the new term – nanonization. A primary goal of size reduction to the nanometer range is to improve product performance. This is usually due to the increased surface area that will be created by grinding finer. However, the impetus to develop new products is also huge. Innovation has driven many ceramics industry researchers to look to nanoparticles – materials ground to 200 nm and finer in size – to enhance product performance or unlock new applications for ceramic materials. Production of nanoparticles using media milling was achieved many years ago, and the benefits are well documented. Nanoparticles are used to improve reactivity, provide increased surface area, and re- duce material consumption (particularly with rare and high-value ingredients). Media milling technology – the use of grinding beads (media) to break down larger particles into smaller ones — plays a significant role in many areas of ceramics processing. Media milling pro- cesses typically entail dispersing the materials into a suspension, using media mills for grinding or dis- persing, then drying the suspension to recover the nanoparticles (in many cases, the final product is used as a suspension or slurry, and the drying step can be avoided). Each successive process is energy intensive and can result in product contamination and wear on the equipment. These challenges have kept po- tential products from being produced in efficient commercial-scale manufacturing processes when a dry powder is ultimately needed. However, since dry processing was limited in its capacity to produce particles in the nanometer size range, wet processing was the only possibility. The demand for finer dry powder products in the submicron or nanometer scale has led to the devel- opment of a new technology that allows real com- minution in this range. Contrary to conventional dry fluidized bed jet mills, this new system uses superheated steam as the grinding gas. Superheated steam as the grinding gas in jet mills has been used for many decades in simple spiral or loop jet mills without an integrated air classifier. Until now it was not possible to produce a material with a well- defined upper particle size limitation. This new tech- nology provides a mill with an integrated air clas- sifier for the separation of the exact particle sizes, and hence the fineness of the product to be milled. "Nanonization" of solids in a dry process with a fluid- ized bed jet mill, with integral classification is now By Stephen Miranda, Netzsch Premier Technologies LLC Cross section of a fluidized bed jet mill ES425540_PB1405_028.pgs 04.18.2014 05:54 UBM black yellow magenta cyan

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