Upgrading of aluminum dross by selective comminution and sizing

CIM Bulletin, Vol. 80, No. 900, 1987

K.J. FAIR, J.M. TOGURI, H.W. SMITH, Department of Metallurgy and Materials Science, University of Toronto, Toronto, Ontario, and D.R. FRANCIS, Metals and Alloys Co. Ltd., Toronto, Ontario

Bench-scale batch milling and screening tests were carried out on secondary aluminum dross to produce an aluminum concentrate. To complement these tests, an analysis of a commercial plant was also performed by sampling dross at various stages in the plant's milling and screening circuit. These studies have indicated that benefits of increased capacity, grade and recovery of aluminum metal can be realized by addition of screens before the ball mill, longer grinding period and by grinding the smaller size fractions more efficiently. To test the predictions, a plant test was performed on the milling of 100 tons of secondary dross. The recycling of the large size fraction (+3/s in.) of aluminum dross through the impact mill rather than through the rate limiting ball mill resulted in a comparable aluminum grade. The ball milling of the-3/s in. + 10 mesh size gave a dross grade of71%Al.A lower feed rate to the ball mill resulted in a higher final grade. With minor modifications, secondary dross can be processed in 22% of the time it takes with the present circuit without a sacrifice in grade.

Keywords: Metallurgy, Aluminum dross, Milling, Grinding circuit, Comminution.