First Mining Drc-Zambia July/Aug 2019 First Mining DRC-ZAMBIA July-August 2019 digital | Page 14

PRODUCT
Even cleaner coal with
Multotec’s X10 spiral
M
ultotec Gravity Division has taken
‘low cut’ spiral technology to the
next level with its new SX10 low
density spiral. This further extends the
benefits this innovation offers in fine coal
beneficiation.
According to Multotec Technology
Manager Faan Bornman, the Multotec
SX10 low density spiral’s reduced cut
point of 1,55 g/cm3 delivers considerable
advantages over the cut points of
between 1,6 and 1,8 g/cm3 typically
achieved in the industry today.
The result, he says, is a cleaner coal
with less waste being achieved in a
single stage. This saves on capital costs
as no further spiral stages are required
for cleaning down the line. The approach
taken with the Multotec SX10 spiral
is to remove the gangue, or mineral
containing particles, from the trough in
two off-takes.
The first off-take removes ash. This
opens up the available separation
surface of the spiral, allowing the
remaining material to separate more
easily, separating clean coal from less-
clean coal.
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“The low density spiral is essentially a
primary and secondary stage on one
centre column,” Bornman says. “Rejects
are discarded into the centre column and
the remaining product is repulped before
being sent to a secondary off-take.”
Facilitating the two off-takes is a longer
spiral on the Multotec SX10. This
increases the residence time and gives
the particles sufficient time to separate.
Depending on the setting of the product
box splitters, this new spiral has the
ability to produce a thermal coal and a
coking coal on one spiral. Bornman says
this was proven through test work done
in the USA. The two offtakes enable the
removal of most of the gangue leaving a
middlings and cleaner coal products to
be collected at the dart splitters.
Experimental work was carried out using
coal from two South African collieries
and the unit has also undergone site
test work in the USA. Promising results
were obtained leading to the first order
for Multotec SX10 spirals from a North
America-based mine.
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