NEW EQUIPMENT
wasting material that we could not sell
without dredging the ponds and re-
processing it through the bucket wheel.
We knew that to grow the business
we had to find a more sustainable and
efficient washing solution.”
The limitations of bucket wheel
technology
Although bucket wheel technology
was widely used in its prime when
sand resources were abundant and
the price of construction materials
was high, it is now being replaced by
more advanced technology to address
shortcomings such as the difficulty to
control the volumes of water required
for accurate material classification due
to the limited capacity at the feed point.
Indeed, as bucket wheels struggle to
process sufficient volumes of water to
achieve the desired cut points, fines are
not efficiently removed and 100 to 300
micron fractions are lost to ponds or to
the water treatment phase along with
the overflow, making the sand product
coarser. To mitigate the risk of inaccurate
material classification, bucket wheels’
settings must be adjusted on a regular
basis. Diverting excess material to
settling ponds requires considerably more
space to accommodate the latter, and
classification efficiency decreases as the
proportion of fines in the feed material
grows. The time then required for clearing
out settling ponds to recover lost material
requires long periods of plant downtime.
Outside of the issue of high
maintenance costs for a restricted
throughput, the sand product typically
discharged from the Ground Breakers’
bucket wheel system contained
between 23% to 25% of moisture.
This high moisture content meant that
stockpiling the final product required
double – sometimes triple – handling
(to move the material to a separate
stockpile area).
The solution
Following a visit by CDE experts, Ground
Breakers’ feed material was tested at
CDE’s laboratory. Based on the analysis
results, CDE engineers established that
the customer could make significant
savings by adopting cyclone technology
to eliminate the loss of fines to ponds.
This would help to retain every valuable
grain of sand available in the system and
reduce the size of the settling ponds as
well as maintenance time. In addition,
CDE technology could add a plaster sand
product to the company’s offer, which has
higher commercial value than the river
sand currently processed.
After considering the site’s footprint
and the customers’ requirements, CDE
presented the Combo all-in-one wet
processing and water recycling system
as the most appropriate solution to the
customers’ requirements. The Combo
would allow them to produce two
high-quality sands simultaneously from
the raw feed including plaster sand and
river sand, for a much faster return on
investment. Incorporated cutting-edge
water management would ensure that
the final products would be dewatered to
services to other quarry operators keen
on using a standalone scalping screen to
repurpose spoils or site rubbles on their
sites as and when required rather than
incur transportation and input costs.
The challenge
To fully achieve the sustainable and
profitable vision of the company’s
owners, an upgrade of the existing bucket
wheel system was required to tackle the
loss of valuable materials to ponds and
excess moisture in the final products.
Janse van Vuuren and Meintjes explain,
“Our quarry site in Lanseria faced a lot of
challenges; we had limited water sources
and limited space to put up a proper
wash plant. Any silt dams we dug was
taking away valuable mining area.
“The market required a clean washed
concrete sand, and our bucket wheel was
not delivering a quality product. We also
lost a lot of fines to the settling ponds,
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Close-up view of material on screen.
JULY 2019
29