Atritor has formed associations with companies who can provide leading edge technology in jet milling and classification. One such company has developed a spiral jet mill complete with a dynamic classifier with high performance potential. Tests on lactose to date have produced material with specific surface areas over 3.5m2/g. The development of the Pharmill® by the joint venture company Pharmill Technology Ltd (Atritor / PMT Jetmill - 50/50) is nearing completion with the first pharmaceutical company running tests on the unit in week 44, 2004.

As a definition generally this describes an impact mill, ie. a mill relying on particle collision with a driven high velocity rotor, combined with a variable speed (dynamic) classifier. The impact mill creates fine particles by attrition which are then presented on the air flow through the mill, to the internal classifier wheel. As described above, the classifier wheel allows the fine product particles to escape while rejecting oversize particles back to the impact zone to be re-milled.

Specific Energy variation is typically 50-200 kWh/t depending on fineness. A classic application for this type of mill, particularly the DCM type, is in the Pharmaceutical & Sugar Industry where a wide range of distributions down to d98 25 µm or finer can be produced. The machine can be fed directly with granular feed, and is often supplied with conditioned air or Nitrogen to avoid excessive temperatures and to protect against explosion.

In the last 10 years the pharmaceutical industry, particularly in Ireland, has welcomed the classifier mill as a replacement for the typical Impact Mill eg. pin mill which was quite adequate but, with greater demands for customised PSD products, the air classifier mill gives a wide range of possibilities between say d97's of 15 to150 microns.

In this atmosphere of flexibility and change, a technical and commercial advantage for suppliers and customers alike, other technologies should be examined for what they can offer. The Atritor Multirotor Cell Mill has, as its name suggests, the potential to run with a varied number of milling rotors and speeds to produce 'designer distributions'. Added to this an integral classifier is available which can either reject coarse particles back to the feed inlet or discharge this material as a separate product stream.

The Cell Mill is particularly useful for high turbulence drying with simultaneous milling or de-agglomeration and for resilient materials which benefit, from a size reduction point of view, from the large area of milling liner (grinding track) combined with the multi-celled (bladed) rotor and the long gap between the two. Its application for the drying and de-agglomeration of chemical precipitates is particularly effective with another €1m project for the CM1250-IC about to be commissioned in Europe (04.10.04).

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