PRECONCENTRATION
Based on the outcome of test work, Cradle Arc
intends to move forward with a development
plan for the upgrades to the Mowana
processing plant, including a DMS plant
ILR cake; combined stage 2 and 3 gravity
concentrate as well as ILR cake wash solution.
The CIL circuit operates at 40 wt% solids with the
slurry residence time being 374 hours based on
CIL tank sizing.
Dense media separation
concentration can be deployed at Mowana on
all low oxide ores (those that contain less than
25% acid soluble copper)
The following key metrics were derived by the
company from the independent test work:
n A mass yield of 30-40%, and an expected
copper recovery of in excess of 85% can be
expected
n Mill feed grades in excess of 2% can be
expected, nearly double the current ROM
n An optimal crushing top size of 10-12mm
should be designed for with respect to the
upgrade project
n Good rejection of gangue minerals is achieved,
including carbon and silicon (with more than
75% being rejected).
Cradle Arc has received an independent test
report from SGS South Africa detailing analysis
sampling results and confirming the applicability
of Dense Media Separation (DMS) for its flagship
asset, Mowana copper mine in Botswana.
Accordingly, it remains the Board’s intention to
pursue a DMS installation in due course and
further updates will be provided as necessary as
the development plan for the upgrades to the
Mowana processing plant progresses.
n DMS identified as a low capex expansion
option to potentially increase production at
Mowana to approximately 22,000 t/y of
copper in concentrate
n DMS could increase throughput to
approximately 2.6 Mt/y with reduced cash Dense medium recovery
costs, leading to an increased NPV of up to
$245 million (from the current base case NPV
of $87 million)
n Test work has demonstrated that DMS pre- While the evolution of DMS technology has seen
various advances since the mid-1900s, there are
still a number of ‘fundamentals’ that will allow
users to reduce magnetite losses over the life of
a plant.
“Across the different processes, there are
basic principles that are common, such as the
use of drain and rinse screens to recover
magnetite from the product and reject streams,”
says Kim Schoepflin, CEO of Kwatani.
She says 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.
Schoepflin outlines the fundamentals to be
observed in restricting magnetite losses,
regardless of which screening arrangement is
chosen.
“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.”
She emphasises that the drain section, which
includes both static and vibrating screens, must
J U LY 1 1 ~ 1 3
h ot e l s an t i ago, c h i l e
th
5 International Seminar on
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executive committee
The preliminary program of the seminar
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40 International Mining | MAY 2018
chair
caius priscu co - organizer
césar pastén
Head of Mineral
Residue Facilities,
Anglo American Academic, AMTC,
Universidad de Chile
co - organizer
dirk van zyl co - organizer
gonzalo suazo
Professor, Norman
B. Keevil Institute,
University of British
Columbia, Canada Geotechnical Professor,
Universidad Técnica
Federico Santa María,
Chile