Individual Mineral Behaviour In A Closed Grinding Circuit

CIM Bulletin, Vol. 70, No. 787, 1977

J. A. Finch and O. Matwijenko, Dept. of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec

Individual mineral cyclone performance curves were determined for the four major minerals at two lead-zinc concentrators. Sizing was by screen and cyclosizer down to approximately 10 pm, with lead, zinc and iron assaying of each size fraction. The performance curves were similar in shape and located according to the mineral specific gravity, pm. The curves displayed a discontinuity at the fine end and a magnitude of short-circuiting of fines to the underflow which increased with pm. Mass fraction of water to the underflow was only a guide to this short-circuiting. Sharpness of separation seemed independent of pm. An inflection in the over-all performance curve was shown to be a consequence of the individual component mineral performance. A general relationship was observed showing that the flow regime of classification changed from laminar/ intermediate to turbulent with increasing cyclone feed size. Individual mineral size reduction for the four major minerals at one of the concentrators was also determined. Size reduction of the silica was greater than that of the galena, in contradiction to their accepted relative grind-ability. The observation did correlate with silica being much coarser than the galena in the feed to the ball mill. It is suggested that the silica acted as a buffer to the galena.
Keywords: Mineral processing, Grinding circuits, Cyclones, Lead, Zinc, Silica, Galena, Sullivan Concentrator, Pine Point Concentrator, Separation, Classification, Flotation, Ball mills.