MINERAL SEPARATION
that, according to the company, over 250 of
Multotec’s modified GV hydrocyclones have been
installed at the operation.
The right vibe
Cornwall, UK-based Holman-Wilfley Ltd is a leader
in the global gravity table marketplace, shipping
its products across the globe for the recovery and
concentration of minerals, and high value metals
from recycling processes.
The company says the “Holman option”
provides a unique design layout and separation
capability and, in competition with standard style
Wilfley options, has demonstrated higher
concentration and recovery of ultrafine minerals.
Around 80% of the company’s sales have gone
to overseas projects in the likes of Russia, South
Africa, Mozambique, Australia and Sri Lanka.
These are being used in applications such as
titanium-bearing heavy mineral sands, tantalum,
tin, tungsten, chromite and gold.
While new construction materials and
engineering techniques have contributed to
advancements in its shaking tables, the specific
separating method, based on known principles of
hindered settling, has remained a constant. “The
Holman mechanical features are robust and
operator friendly, well suited to the severe
operating conditions around the world
encountered in the mining and metal recycling
plants,” Holman-Wilfley told IM.
These shaking tables are often associated with
other gravity devices in flowsheets like spirals and
multi-gravity separators. The company claims,
though, that no recently developed technology
can match the enrichment ratios achieved by
gravity tables.
Such tables were historically associated with tin
and tungsten operations and, once again, it is
these metals that have come into focus for
Holman-Wilfley – both single and double deck
Holman tables have been commissioned in
tungsten/tin operations Europe in the last 12
months. Expanding on this, the company said
multiple Holman machine installations now form
an integral part of several new Spanish tungsten-
tin projects.
And Australia’s hard-rock lithium miners have
also sought Holman-Wilfley’s expertise, with the
shaking tables finding their way to several
spodumene operations in Western Australia where
the effective separation and recovery of valuable
tin and tantalum by-products can provide further
revenue.
Both chromite and gold operators have been on
the lookout for Holman shaking tables in the last
year. One table is in the process of being installed
in the Balkans to process chromite ore, while
small-scale gold operators in Sudan and Romania,
as well as large scale producers in Colombia and
Australia, have also installed them.
As an example of its shaking table success, a
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Holman-Wilfley customer recently suggested to
the company it had produced a daily record of 220
kg of smeltable gold directly from a single deck
Holman 8000.
Going to the poles
The discussion around magnetic separation in
mining often revolves around the protection of
downstream equipment, yet there is much more to
the technology, according to Jose Marin, Eriez’s
Director of Minerals and Materials Processing.
“Magnetic separation can be seen in many
places,” Marin told IM. “Many industrial minerals
are sold with a relatively low level of other gangue
minerals, or impurities. In order to meet the
product specifications, magnetic separation is an
indispensable part of the process.”
Besides the use of magnets in the crushing
circuit of a mine, a relatively low number of
mineral processing plants use “proper” magnetic
separation to help deal with the iron generated
from the wear and tear of balls and liners in ball
mills, Marin said.
“Essentially, the amount of the charge to a mill
is equivalent to the steel amount that is
introduced into the system,” he explained. “Plants
that do not use trunnion magnet systems or wet
drums on smaller mills have to deal with that
added gangue or impurity, typically in flotation or
gravity concentration.”
He provided an example here: a gold plant that