Demagnetization of fine ferromagnetic materials

Analysis of the works on the magnetic separation of minerals in the
preparation of ores shows that this process has proven to be successful in
the extraction of valuable minerals from waste. As for the enriched product,
the primary separation (with the initial content of the valuable mineral α
<50%) gives a significant quality increase. Since the liberated valuable
mineral is not removed from further processing, the initial content of the
valuable mineral keeps increasing through the stages. On the other hand,
due to flocculation, the capture of the non-metallic phase also increases.
The probability of capture is proportional to the product of valuable (PM)
and non-valuable (1-PM) minerals content. Hereafter, without the use of
special methods, it is not possible to extract these particles from the mass of
the concentrate, since the probability of the removal of liberated nonmetallic
particles asymptotically tends to zero. Thus, it is theoretically
impossible to obtain pure magnetite concentrates by magnetic methods that
are currently used at iron ore preparation plants.
Production of pure concentrates requires reducing of all particles
to zero residual magnetization, i.e. they need to be demagnetized
before further non-magnetic separation.
Until now, there are no devices for complete demagnetization of
fine particles of the ferromagnetic material in the suspension
flow.
Demagnetization of such type can be carried out in highfrequency
magnetic fields with induction amplitude greater than
the residual magnetization of magnetite particles.
Demagnetization of ferromagnetic particles before their further
non-magnetic separation can provide indices of the concentrate
quality, close to the theoretically possible ones.