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Grinding of waste paper and rice hulls for use as reinforcing plastics fillers was studied using Szego Mills SM-220 and SM-320 in open circuit grinding as well as in combination with a high capacity classifier. Depending on how the fibres and the plastic are compounded, properties of the composite may or may not depend on particle size. Nevertheless, it is necessary to get the fibres below some top size and into a suitable shape for better handling during storage and feeding and later moulding. Szego Mill products are easier to feed and handle, compared to those from a hammer mill, for example. Particle size distribution, bulk density and flowability of the products were determined after open circuit grinding under different conditions and after classification. Bulk density of newsprint triples when the top size of the particles decreases from 3 mm to 425 μm. Flowability on a volumetric basis remains almost constant and, hence, the mass flow rate depends only on changes of bulk density. Capacity and specific energy consumption of grinding depend strongly on particle size distribution in the feed and the desired top size of the product. A production rate of 220 kg/h was reached while reducing newsprint particle size from 3000 μm to |
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