Fine sizing by Cyclosizer and micro-sieve

CIM Bulletin, Vol. 75, No. 839, 1982

J.A. FINCH and M. LEROUX, Department of Mining and Metallurgical Engineering McGill University, Montreal, Quebec

Sizing below 38 um (400 mesh) is an increasing requirement in mill testing laboratories. The Cyclosizer is gaining wide acceptance in this role. A recent alternative is to use electro-formed sieves (micro-sieves), which are available with openings down to 5 um. The advantage of micro-sieving is a cut size which is independent of mineral density, easier retention of the finest fraction and reduced purchase cost. A simple method of micro-sieving using an ultrasonic bath, which performs readily to 10 um, is described.A systematic study of Cyclosizing and micro-sieving is reported for three samples; silica, copper oxide and a lead concentrate. Micro-sieving gave comparable results. Comparison with a standard sizing method, the Sedigraph 5000D, revealed misplaced material in each fraction by both methods. The range for micro-sieving was from 20% to 60% depending on the sieve and material; for the Cyclosizer it was a consistent 40-50% for all cones and all materials. The Cyclosizer can be sensitive to feed mass and particle size for dense materials. It is recommended that for minerals of specific gravity greater than 5, no more than 35 g of -38 um be used.The disadvantage of micro-sieving is that it requires continuous operator attention and sieving time depends on sample mass. To fractionate 35 g—as used on the Cyclosizer and considered at reasonable mass for mill testing purposes—through 25-, 15- and 10-um sieves requires about 80 minutes.

Keywords: Milling, Testing, Sizing, Cyclosizers, Micro-sieves, Sedigraph, Silica flour, Copper oxide, Lead concentrate, Particle size.