Abstract
Recovery of fine non‐ferrous metals from waste streams is a notoriously difficult problem in eddy current separation technology. Existing processes either have a low capacity or an incomplete recovery for particle sizes below 5 mm. In a new process, the particles are fed slightly wet to make them stick to the surface of the conveyor belt. The action of the magnet rotor makes the non‐ferrous particles tumble, so that they break loose from the belt and end up in front of the rotor. The new process combines a relatively high capacity with an almost complete recovery, even for heavy and poorly conducting non‐ferrous metals.
Highlights
Traditional eddy current separators have a problem in recovering non-ferrous particles with a diameter of less than 5 mm [1,2]
An interesting possibility is to use the Magnus effect, i.e. the force acting perpendicularly to the trajectory of a rotating body that is falling in a fluid. Since this force derives from the fluid around the particles, it is not necessary to feed in a monolayer and so the throughput can be as high as 6 t/h per metre of rotor width
In order to test the practical use of the separation concept, a number of experiments were conducted on a granular waste stream with a particle size between 2 and 6 mm
Summary
Traditional eddy current separators have a problem in recovering non-ferrous particles with a diameter of less than 5 mm [1,2]. An interesting possibility is to use the Magnus effect, i.e. the force acting perpendicularly to the trajectory of a rotating body that is falling in a fluid Since this force derives from the fluid around the particles, it is not necessary to feed in a monolayer (see [5] for an analysis of the need of monolayer feeding in traditional eddy current separation) and so the throughput can be as high as 6 t/h per metre of rotor width. Experiments by Zhang et al on a traditional eddy current separator show that this mechanism works well for non-ferrous particles with a granular shape, if all the particles are small enough to avoid domination of the linear eddy current force [2] This force is normally counteracting the effect of rolling, except when the rotor is above the conveyor belt, as in the design by MeierStaude et al [11]. We will give the theoretical background of the separation mechanism and report the results of experiments on an actual waste stream
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