Maximizing haematite recovery within a fine and wide particle-size distribution using wet high-intensity magnetic separation
M Dworzanowski
The physical beneficiation of iron ore that has a wide particle-size distribution
is problematic, regardless of the process applied, whether dense
medium separation, gravity concentration, magnetic separation, or
flotation. The problem of particle size is further compounded when there is
a significant -10 µm fraction. Generally the approach to a wide particle-size
distribution is to split into narrower size ranges and treat each separately.
More often than not the -10 µm fraction is not treated but discarded. This
approach results in a more complicated and expensive flow sheet and the
loss of any potential value in the -10 µm fraction.
Wet high-intensity magnetic separation (WHIMS) bench-scale test
work was conducted on a haematite-rich material with a particle size of
-200 µm. What made this material different was that it contained a 60%
-10 µm fraction, hence discarding the -10 µm material was not an option.
The objective of the test work was to determine how to maximize the
recovery of the haematite across the full particle size range. Given the
unusual particle size distribution, it was concluded that WHIMS would be
the only practical beneficiation route. The -200 +10 µm and -10 µm
fractions were treated separately and together under varying WHIMS
conditions. For a given concentrate grade, the mass yield obtained was
greater when the total particle-size distribution was treated. The inferred
optimum conditions, using the same material, were tested on a pilot-scale
WHIMS and similar results were obtained.
Keywords: WHIMS, haematite recovery, particle size distribution, -10 µm fraction.