Cradle to grave
Fundamentals to
reduce magnetite losses
W
hile the evolution of dense
medium separation (DMS)
technology has seen
various advances since the mid-1900s,
there are still several ‘fundamentals’
that allow users to reduce magnetite
losses over the life of a DMS plant.
According to Kim Schoepflin, CEO
at Kwatani, principles such as the use
of drain and rinse screens to recover
magnetite from the product and reject
streams need to be adhered to.
“Furthermore, a concentration of
magnetite in the dilute medium must also be
achieved to give a suspension of high relative
density, or over dense, medium using wet
drum magnetic separators,” says Schoepflin.
“The feed arrangement onto the
screen must ensure that the full
width of the screen is utilised,” she
says. “Low feed velocities are also
critical, as this maximises the drainage
rate on sieve bends and multi-slope
screens,” adds Schoepflin.
She emphasises that the drain
section, which includes both static and
vibrating screens, must have sufficient
area to recover 95% of the medium
that is fed to it, and allowance must be
made for potential blinding which will
reduce the open area of the screen.
“It is vital to take the average particle
size and bed depth into account
when selecting the screen width,” says
Schoepflin. “Running at a high bed
depth will increase medium carry-over
from the drain to the rinse section,
and will also reduce the efficiency
of the rinse water in washing off the
medium which will lead to an increase
in magnetite losses,” adds Schoepflin.
Another important aspect to observe
is that sufficient rinse water must
be used to wash off the adhering
medium, without overloading the wet
drum magnetic separators. “Provision
must also be made at the end of the
screen – after rinsing – for the clean
coal and reject material to dewater
before it is discharged off the end of
the screen,” Schoepflin concludes.
A blast for the record books
Block preparation for the AXXIS record blast.
B
lasting and explosives company
BME has broken the world
record for the most electronic
detonators fired in a single blast.
The record breaking blast took place
last year at First Quantum’s Kansanshi
copper mine in North-Western
Zambia and was conducted in the
main pit of Kansanshi, which is the
largest copper mine in Africa by
copper production. It involved 6 690
electronic delay detonators (EDDs)
which was initiated using BME’s
Axxis digital initiation system.
According to Wayde De Bruin, area
manager for BME Zambia, all the holes
were single-primed with a set-up that
included nine different shots, 18 slave
blasting boxes and one master box.
“The blast moved about 455 000 bank
cubic metres (BCMs) and consumed
a total of 400t of emulsion explosives,
yielding an overall average powder
factor of 0.9kg per cubic metre,” says
De Bruin. “The blasts were offset to
keep the mass charge per delay to a
minimum; the highest timing recorded
on this blast was 6 520 milliseconds.”
BME’s Axxis global product manager,
Tinus Brits, highlights the company’s
technical ability to continually push
the boundaries through its innovations
and in-house research capacity.
“This blast follows previous records that
BME has achieved in the past with our