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Rotating magnetic field separation of minerals

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Allen, NR (1999) Rotating magnetic field separation of minerals. PhD thesis, University of Tasmania.

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Abstract

The behaviour of particles in a rotating magnetic field can be used as a basis for a new
mineral separation method, where particles are separated on the basis of their relative ability Ito
rotate in a rotating magnetic field. Both particle attraction and particle rotation separations
may be combined in a single separation process, to offer previously impossible magnetic
mineral separations, such as the separation of high-Mg ilmenites (picro-ilmenites) from other
ilmenites of the same magnetic susceptibility, or to produce separations which are more
precise than those currently available, such as the low-entrapment separation of magnetite or
monoclinic pyrrhotite.
Whereas mineral separation by particle attraction involves the use of material
properties such as the number of unpaired electron spins and their relative orientations,
separation by particle rotation adds the properties of magnetic anisotropy and such dynamic
magnetisation processes as domain wall velocity in ordered magnetic compounds. The use of a
continuously rotating magnetic field also generates eddy currents in particles, in proportion to
particle electrical conductivity, which allow conductive particles to be rotated by eddy current
effects, and extends the same separation process into the practical separation of small particles
of non-magnetic metallic compounds.
Particle rotational characteristics may be estimated using similar equipment to that
used for practical rotating field mineral separations, so that these characteristics may be readily
applied to practical separations. These estimations are presented in the form of a "rotation
index", which relates the actual particle rotation strength to the maximum possible rotation
strength indicated by particle magnetisation. Although the measurement of particle rotational
characteristics by these methods is only approximate, it is accurate enough to demonstrate the
presence of and estimate the magnitude of, such dynamic magnetisation processes as domain
wall velocities in small particles of natural ordered magnetic compounds.
Particle rotation by magnetisation is also shown as being able to cause particle
rotations for which the particle rotation axis is at right angles to the field rotation axis, and
which are of sufficient strength to play a part in a rotating magnetic field mineral separation
process.

Item Type: Thesis (PhD)
Keywords: Magnetic separation, Minerals
Copyright Holders: The Author
Copyright Information:

Copyright 1999 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:49
Last Modified: 11 Mar 2016 05:54
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