Eddy-current separation of non-ferrous conductors and non-conductors: theory and initial experiments

The structure and principles of a basic, single magnetic field boundary, eddy current separation device for the removal of nonferrous conducting elements (objects) from nonferrous but otherwise mixed input streams are examined. The theoretical trajectories by which two model elements of circular and rectangular geometry pass through the device are derived, and the behavior of these elements under a wide range of system variables is examined. Initial experimental exploration supports the general theoretical conclusions. Analysis of the Lorentz force experienced by rectangular and annular conducting elements shows that this single boundary can produce a force that is up to four orders of magnitude larger than that previously reported for a multiple boundary permanent magnet system