Optimise your thickener efficiency for
maximum pro tability
Once extracted from the ground, mined ore is subjected to a complex series of steps
before it can be converted into its purest state ready for use. The continual
improvement of these process steps is critical to on-going profitability of mine
operations.
A key step in most ore re ning operations is
the physical separation of process water
from the useful extract or tailings. e
optimisation of this process is critical for
several reasons:
1.
e availability of large volumes of
process quality water in South
Africa is always limited and
expensive making the use of
recycled water attractive.
2.
Energy and occulant costs is a
major contributor to process costs.
3.
In many cases, tailings can be reprocessed to extract ne traces of
precious metals. However, for this
to be economically viable the
water content of the tailings needs
to be minimised reducing the
energy and chemicals needed for
extraction to an absolute
minimum.
Page16
| May - June 2016
4.
Impure waste water can leach into
ground water and waterways
polluting water supplies. South
African regulations determine
acceptable levels of impurities that
can be discharged.
Large tanks, known as thickeners are used
to separate ne suspended mineral particles
from the process water, producing a stream
of clari ed water from the top of the
thickener over ow and a thick sludge of
settled solids (under ow) from the bottom.
Flocculants are mixed with the solid –
liquid suspension in the entry feedwell of
the thickener. e occulants aggregate the
ne particles, which speeds up settling of
the solids.
ickeners are used in many mineral
re ning processes, including alumina, gold,
nickel, mineral sands and coal washeries. In
fact, most minerals go through a solid –
| FMDZ
liquid separation in a thickener at some
point in their processing.
Most mining process operators agree that
one of their major challenges is to
accurately and reliably monitor the bed
level and bed mass of their thickeners
which in conjunction with other critical
process parameters allow the optimisation
of thickener efficiency.
Bed level:
e 'bed level' is the interface between the
aggregated solid material and the process
water. Incorrect measurements can lead to
water being drawn out through the
under ow, sludge spilling over in the
over ow or incorrect occulation. ere is
unnecessary expense involved in all cases
due to wasted occulent or reprocessing
costs.
Depending on the application conditions,
different techniques are employed to
determine a thickener's bed level: