TAILINGS EQUIPMENT
beneficial in areas where water is in short
supply or very expensive; when re-circulated
water is not suitable for reuse in a plant; where
ponds are located on minable reserves; or
where ponds must be reduced in size due to
permitting issues.
“High-rate thickeners separate liquids from
solids using hindered settling. Rotating rake arms
collect settled sludge and move it toward the
centre discharge cone. They use minimal amounts
of polymers/chemicals in order to drop the solids,
making it environmentally friendly. Deep cone, or
paste, thickeners are meant to achieve the
highest solids concentrations possible through
gravity separation. The resulting mud, or paste, is
often so dense that no further separation of water
and solids can be achieved. Pastes are then
moved to impoundment structures or processed
further through filter presses. Fed from the top,
deep cone thickeners initially rely on the process
of free-settling. After the fines reach a certain
point in the process, they continue to thicken
through hindered settling. Depending on the
characteristics of the material a deep cone
thickener can be designed with no moving parts
or with pickets (rakes) that rotate slowly to create
channels in the mud, releasing water.”
Filter presses are ideal for producers looking
to reduce or eliminate settling ponds, as well as
those unable to receive permitting for new
ponds. “They provide producers with a drier
product than traditional belt presses, centrifuges
or screw presses. Filter presses can also help with
reclamation or reducing transportation and
disposal costs of waste products.”
Recessed plate or membrane filter presses
create a chamber for dewatering slurry without
trapping cakes. This allows dewatered cakes to
be discharged more easily than with traditional
plate and frame presses. Recessed plates
dewater using hydraulic pressure created from
feed pumps, while membrane plates are
designed to squeeze the cake once the chamber
is full of slurry. The filter press then produces a
dry, drip-free cake. This fully-automated system
does not require operator assistance and in most
cases, no additional chemicals are needed.
Filter presses are frequently categorised into
two main styles each with their own advantages
and disadvantages:
n Overhead Beam – Denoting a press in which
the filter plates hang from overhead beams
No parts on the sides of the press,
providing unobstructed access to change
filter cloths on the press without plate
removal.
Much wider plate openings often
exceeding 3 ft (0.9 m) between the plates,
creating more movement to aid cake
release, while also allowing easier access
for cloth washing and inspection.
Dynamic loads are typically isolated from
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the beams of the press using tension
shafts in various configurations.
n Side Beam – Denoting a press in which the
filter plates are supported by beams running
along the side of the press.
Easier to implement shaking systems for
applications requiring shaking systems
Lower upfront cost
Less access to plates for cloth washing and
inspection. Automatic wash systems
should be considered more heavily with
side beam style presses due to limited
plate access.
McLanahan concludes: “Tailings management
is an extremely important part of any mineral
processing. Although not always thought of as
the cleanest or easiest part of the planning, a
well thought out tailings management plan can
lead to higher recovery, reusable water, better
access to resources and higher ROI. Thickeners
are the start of the tailings management process
and can be selected in a variety of styles. Each
style has similarities, but produces a different
style of tailings. Thickeners can also be followed
by recessed plate filter presses, which can help
sites eliminate ponds and impoundment
structures altogether. Producers should make
sure to contact a manufacturer that is
knowledgeable in testing and verifying results to
ensure tailings management solutions fit the
needs of their processing facility.” IM