MINE EXCURSION
“At the moment we also have three products that we sell; a run-of-mine
sand that is not screened or washed and used as a filler sand; a run-of-
mine sand screened to 8mm, that contains 13% by volume passing 75μ;
and our main product being the 98% silica sand that is produced after
processing through the washplant. The current installed production
capacity is 30 000 tonnes per month. The mine’s standard grade of
product is delivered at -8mm /+75μ, carrying an average 2.4% of sub
75μ material, which allows our clients to receive a consistantly graded
product at volume, suitable for making high grade structural concrete,”
says Blackmore.
AST uses a dry mobile screen on site, a Chieftain CH2100 X power screen,
that produces four distinct sizes. Material larger than 13mm is ejected
as oversize, while the envelope between 10mm and 13mm is sold
as a G5 screened sand, and the material between 8mm and
10mm is sold as a finer screened sand. Everything less
than 8mm is put through the wash plant.
The CDE Evowash plant arrived in South
Africa in seven 40 foot containers from
Northern Ireland three years ago.
The plant comprises a hopper, feed
conveyor, washbox, vibrating screen,
sump, cyclone, and an Aquacycle.
Micromaterial of 75mm that is
ejected from the cyclone enters the
Aquacycle where it is bound with a
biodegradable poly-floculant, which
increases the density, allowing the
material to be disregarded as slimes
which are dried and stored for further
processing. The washplant recycles
90% of the water used in the washing
process, making for a much more environmentally-friendly process.
The discard from the washing process contains high concentrations of
Kaolin, which, according to Blackmore, can also be extracted and sold
as a primary product. However, this process will require an additional
extraction stage and processing plant.
Moving sand
When the mine initially started moving sand four years ago, it was a
greenfields project and an earthmoving exercise. Blackmore says they
used a Caterpillar D10 Dozer to push half a metre of overburden to
the perimeters to create the mine boundaries and the haul roads. The
top three meters of loose sand were then moved to create four big
stockpiles which was processed over two years. Today, a Caterplillar
330 LME excavates the blasted sandstone and a Bell
B30 Articulated Dump Truck is used to haul the
material to the mobile screen and wash plant.
Other equipment on site includes two
Komatsu WA380 Front End Loaders and
a Mercedes 18000 Water Bowser.
"A big challenge in the area
is the illegal mining of sand, for
which the Department of Mineral
Resources (DMR) is actively
working to prevent.
The blast, carried out by B&E
International, part of the Raubex
Construction group, made
more than 50 000 tonnes of
product available. According
to Blackmore, the company
drilled 301 holes in a week
with a burden of 3m with a
spacing of 4.2m. “Each hole
was drilled at an average
depth of 5m and we used 6.5t
of emulsion explosives,” says
The CDE Evowash comprises of a hopper, feed conveyor, washbox, vibrating
screen, sump, cyclone, and an Aquacycle.
20
African Mining September 2019
www. africanmining.co.za