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MODERN MINING
August 2015
PROCESSING
Vertical ring WHIMS machines
can boost chromite recovery
Below:
The Longi-Multotec verti-
cal ring WHIMS machine for
paramagnetic mineral
beneficiation.
According to Multotec Process Equipment, its vertical ring Wet High
Intensity Magnetic Separator (WHIMS) technology is proving
effective in recovering the fine chromite in Platinum Group
Metals (PGM) tailings.
T
he need exists to separate
platinum group metal rich
silica and chrome as the
first step in PGM benefici-
ation. The material is then
milled even finer and the platinum is
separated from the silica, commonly
using flotation. Tailings in South Af-
rican operations typically contain a
large portion of unrecovered chromite,
which can range from 8 to 20 % by mass
and 80 % passing 100 microns. While this is
fairly well liberated, with the minus 1 000 to
plus 115 microns being recovered by spirals,
to date there has been no proven technology
with which to recover the fine chromite.
Due to the fact that the chromite is paramag-
netic rather than ferromagnetic, a very high
force factor is required to attract this material.
The Longi-Multotec vertical ring Wet High
Intensity Magnetic Separator (WHIMS) now
offers PGM tailings operations the ability to
recover this chromite, says Willem Slabbert,
Application and Process Manager at Multotec
Process Equipment.
WHIMS is a well-known and proven tech-
nology across a range of commodity sectors
having been extensively used in haema-
tite beneficiation, in the recovery
of ilmenite in minerals sands
applications, in manganese benefi-
ciation, copper beneficiation and
pyrite scavenging. The applica-
tion for the recovery of chromite is
fairly new and Multotec is currently
involved in extensive test work.
Magnetic field intensity is measured
in Gauss and the field gradient is measured
in units of Gauss change per mm. The field
Above:
Slimes dam ultra fine chrome separated from PGM
containing silica with a Longi-Multotec vertical ring
WHIMS machine.