MAGNUS SEPARATION

Abstract

The Magnus effect, i.e., the lift force, which is observed when a spinning body moves through a fluid at right angles to its axis of rotation, can be used to separate metal particles from a mixture. The necessary selective rotation of the metal particles is brought about by the action of a fast-spinning magnet rotor, of the same kind that is used for eddy current separation. Experiments show that metal particles with screen sizes from 500 μm to 10 mm can be concentrated from a slurry fed on top of the rotor. A potential application of wet Magnus separation is the recovery of aluminum, copper, and zinc from the bottom ashes of (municipal) solid waste incinerators. Mixtures of a more narrow size range, from 500 μm to 2 mm, can also be treated dry. Dry Magnus separation may be interesting for the recovery of precious metals from dry alluvial deposits, as it combines high capacity with low cost.

Keywords:

• Metals
• Recycling
• Fluid mechanics

ACKNOWLEDGMENTS

The authors are grateful to Dr. A. Weisenborn of Shell for his overview of the literature on the Magnus effect and to Mr. P. A. C. M. Haeser for his experiments on the Magnus effect in air.