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MODERN MINING
May 2016
feature
CRUSHING, SCREENING
AND MILLING
R
hodes Nelson, MD of Multotec
Manufacturing, tells
Modern
Mining
that some iron ore mines
are focusing on increasing the
throughput volume because their
business model is based on the cent per ton
calculation. Other mines are using the differ-
ences in their geological resource characteris-
tics and therefore have to look at optimising
the product quality to create differentiation.
“The same is true in the diamond sector
where mines producing gem quality stones are
increasing throughputs to increase yields while
those producing industrial type application
diamonds are trying to reduce the cent per ton
model,” Nelson says.
He notes there has also been a major increase
in waste dumps being recycled across a range of
commodities. “This,” he explains, “is another
opportunity to squeeze volume out without
having to deal with the mining constraints and
allows miners to meet long term contractual
requirements.”
Although greenfield capital project plants
have largely dried up, there remain brown-
field opportunities within existing operations
– including the recycling of dumps – and these
present the need to optimise plants to adapt to
the changing throughput and grades required
by customers.
Market conditions coupled with the ongo-
ing drive to optimise minerals process plants
have led to a situation where the control of the
changes in the orebody is heightened more so
than in more economically relaxed times.
“This has made the selection of screen
media more important than ever to make sure
that it will fit into the ‘sweet spot’ for the plant
because of this variability. Add to this, the
sweet spot is a constantly moving target and
where, in previous years, a screen media solu-
tion supplied would have stayed in place for
extended periods, today this is no longer the
case,” says Roy Roche, Vice President Screen
Media at Multotec.
He cautions, however, that changing the
throughput on a screen is not the simple exer-
cise that many mines believe it is. “It requires
the input of skilled process engineers who can
recognise that there are a number of factors that
need to be considered.”
In previous years, there would probably
have been just one type of screen media on the
screen. This has changed dramatically in the
drive to optimise screening operations and has
led to increased innovation and out-of-the-box
thinking in terms of applying fit-for-purpose
solutions to screens. Roche says that in some
applications today there are up to nine types of
panels on a screen deck.
“Another example would be where a combi-
nation of compression moulded and injection
moulded rubber panels is used along with
diverters to ensure optimum throughput with
well over 95 % screening efficiency,” he says.
An example would be where specially engi-
neered screen panels which combine Hardox
®
embedded in rubber have been installed on the
feed sections of screens in an iron ore applica-
tion. These panels are capable of handling the
impact of the 600 mm top size. On the same
screen bed, high impact slotted skid bar pan-
els, known as Multotec Ratel panels, are used
to reduce channelling and ensure accurate cut
size while providing maximum screen panel
life. In this self-same screening application,
Correct screen media selection
now
Rhodes Nelson, MD of Multotec Manufacturing, and Roy
Roche, Vice President Screen Media at Multotec, inspecting a
newly designed screen panel.
Asset optimisation has always been a primary objective
for all mining houses – the more so in the present tough
conditions facing the mining sector. A major asset for
all mines, of course, is the minerals processing plant and
optimising its operation will vary from commodity to
commodity and frommine resource to mine resource,
with the selection of the correct screen media being an
important part of the process.