The number of shafts at Obuasi gold mine in Ghana has been reduced
from nine to six, with the elimination of two more expected,
AngloGold Ashanti executive officer: Africa underground Robbie
Lazare tells Mining Weekly in an exclusive interview.
For what is a relatively small block of ground, Lazare points out
that there is considerable infrastructure, the nine shafts
previously serving a span of only eight reef kilometres.
Obuasi shafts are, howevesilver mine process plantr, not easily closed, as each has its own
electricity, water and ventilation systems that require complex
replanning.
But the benefit is lower operational costs, which, togmobile crusher priceether with
extensive recapitalisation of both equipment and infrastructure,
are helping to turn Obuasi around.
Recapitalisation has included investment in: • new trackless
egrinding machine stone sharpening and settingquipment, which is increasing production; • the equipping of
the Brown Sub-Vertical Shaft, which is providing access to an
additional block of ground; • the commissioning of a new
refrigeration plant at the Kwesi Mensah Shaft (KMS), which is
lowering working temperature; • the planned commissioning of
another refrigeration plant at the George Cappendell Shaft, which
will lower temperature before year-end; and • the construction
of a ramp, which is providing access to all mining blocks.
“There have also been marked improvements in terms of the
amount of backfill that we are placing, ensuring that we are mining
in the correct areas and reducing dilution to acceptable
levels,” says Lazare, who adds that special attention is
being paid to equipment availability and ore-reserve development.
At this point, cash costs an ounce need to be reduced by 10% or
$30/oz by year-end.
With the new ramp system, trackless equipment – which had
previously to be dismantled on surface and taken underground piece
by piece for reassembly – can now be driven down.
As AngloGold Ashanti finds that, in addition to safety
considerations, productivity can decrease by as much as 20% for
every de-grees rise above 28,5