MINE EXCURSION
Currently the mine is renting three excavators, six Articulated
Dump Trucks (ADTs) and a few water trucks.
An unconventional mine
Demaneng does not host a single, uniform ore body. It is not a
conventional mine and there are a number of mini pits on the
property between 60m to 120m deep. Afrimat utilises three
of these pits at any one time and blends the mined products.
This mining method calls for smaller equipment to be used at
several locations at different times, somewhat different from
conventional mega operations like a Sishen mine that employs
much larger equipment.
The blend from the different pits are fed into a primary crusher
(a Metso 120 Jawcrusher) from where it splits into a secondary
crusher (a Sandvik UH430) and a tertiary crusher (Osborn 44H).
From here the material splits into various slipping streams
and the fine ore component is split with a high frequency
screen into a -1mm fraction. Odendaal says they are currently
investigating other methods to do some ultra-fine beneficiation.
“We ultimately end up with a stock-pile of one and a half million
tonnes of unprocessed fines of less than 1mm which will
hold about 700 000t or 800 000t of sellable ore.
Dealing with challenges
Other major challenges on site,
according to Odendaal, was dealing
with the slimes and the lack of
available sub-surface water. “Water
is not readily available in the
area and 50% of our current
water supply is sourced from an
underground aquifer up to 180m
deep. The balance is purchased
commercially from the bulk
water supply scheme.
Odendaal, who has a lot of experience in managing quarries,
says the methods of mining a quarry and an open cast mine,
are usually the same. “Both involve drilling and blasting the
overburden and ore and disposing of it using specific mining
equipment. However, the difference between Demaneng
and any other quarry is that the ore body at this mine is a
sedimentary deposit in random pockets of dolomite. It is
therefore not uniform and sits in an erratic formation which
makes it necessary to follow the higher graded ore body, so
there are fewer consistent neat bench formations, haul roads
and ramps, and that is the most important difference,” says
Odendaal. Furthermore, quality control is an important function
when mining iron ore as the grade and quality are far less
predictable than in quarries where there are large benches
featuring the same quality of material. The quality control and
laboratory work is conducted as an in house function, affording
the mine speedy turnaround times and priority access to testing
which in turn speeds up accurate selective mining.
Despite the challenges, Demaneng has gone from strength
to strength. Odendaal says it has a lot to do with the fact that
the operations team at the mine doesn’t know when
to give up. “This attitude comes from the top
and filters through to the bottom, and it
works for us. The entire company works
together. Attacks the issues and finds
solutions. We also found ourselves
in the fortunate situation where
we managed to secure some
of the most competent
industry experts in iron ore
extraction and beneficiation,
which positively shortened
Afrimat’s learning curve
in the iron ore sector,
concludes Odendaal.
“One of the
optimisation projects
is to increase our own
mining fleet over the rental
equipment that we currently
employ to supplement
the mining.
Afrimat has secured 900 000 tonnes of export capacity per year from Transnet.
www. africanmining.co.za
African Mining Publication
African Mining
African Mining February 2020
21