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Paste Supplement
underflow slurry. The
additionally captured water
reduces the amount of
water sent to tailings and
can be re-circulated in the
plant.
Recover even more
water with filter
presses
FLSmidth’s Evolute™ feedwell increases
mixing and aggregate growth
performance, and ultimately enhance
customers’ profitability. Great strides have been
made with innovations to the feedwell
apparatus. For decades, FLSmidth’s E-DUC® feed
dilution systems have resulted in significant
increases in equipment capacity as well as
improving flocculation and thickening efficiency.
When installed as an upgrade, the E-DUC has
been proven to increase the average daily
tonnage output, reduce flocculant consumption,
increase underflow density and improve overall
equipment performance.
FLSmidth engineers have designed and
constructed a new Evolute™ feedwell, a result
of years of laboratory, CFD (computational fluid
dynamics) and pilot scale development work. It
is designed to maximise the critical parameters
of “best practice” feedwell performance, and
incorporate all the benefits of both closed and
open bottom feedwells. The unique, full-shelfwidth entry of the Evolute™ feedwell system
allows for maximum residence time within the
feedwell, increasing mixing and aggregate
growth as well as reducing un-agglomerated
fines and un-absorbed flocculant. The involute
shape promotes even distribution of
agglomerated solids into the thickener,
minimising the risk of p oint loading of the
raking mechanism, and maximising settling
capacity of the thickener, whilst reducing
internal dilution within the feedwell.
For even more effective
tailings management,
filtration equipment options
can be installed at the end
of the mineral processing
line to further dewater
tailings prior to disposal and assist in the
recovery of water for re-use in the process.
Installing FLSmidth’s minerals pressure filters
after the tailings thickeners, increases the
efficiency of dewatering the remaining tailings
to create a filter cake that meets project
geotechnical requirements.
Depending on the mineralogy and particle
size distribution, the discharged cakes can be
sticky in nature or crumbly. The nature of the
discharged cake will significantly impact the
operation of the downstream material handling
equipment. Sticky cakes will plug transfer
chutes and stick to the conveyors and must be
avoided by proper design of the entire system.
Operational flexibility is needed as the
tailings filtration characteristics change over the
life of the mine. For these reasons, large modern
filter presses are becoming the equipment of
choice for high tonnage tailings dewatering
applications. Because some large mining
operations process over 100,000 dry tonnes of
tailings per day, FLSmidth’s newly designed
Colossal™ filter press has been engineered to
be twice the area as previous filter presses. The
Colossal filter utilises a rolling cross head with
up to 2,080 m2 of filtration area and up to 38.4
m3 volume in a single machine. One such filter is
currently being installed at a copper
concentrator in Chile for use in filtered tailings.
Adding the proven AFP high speed filter press
technology to the tailings equation allows for a
reduction of the number of filters required for
any given tonnage. The filtered dry tailings
concept means a mine site is able to operate
with much less external water compared with
similar concentrator plants. With the larger
Colossal filter even more water is captured for
recirculation at the plant.
Tailings storing and management
Having already mentioned the downside to
traditional tailings ponds, FLSmidth is educating
customers on the innovative solution of dry
stacking. The drier tailings produced by the
thickening and filtering processes can be
stacked and compacted by conveying and
spreading equipment in multiple lifts per pad,
taking up less than half of the area of a tailings
pond. This solution makes for a far more
environmentally friendly mining site. Mining
companies can stack and compact the tailings
and start the re-vegetation process much earlier.
The dry stacked tailings have the benefit of
being highly reusable, and can be contoured to
allow the stacks to blend in with the local
landscape. The area can then be replanted with
a native seed mixture as operations continue.
This supports and speeds up the environmental
reclamation process and expedites the re-vegetation
of the surrounding landscape. Upon completion,
the dry tailings storage pile eventually blends in
with the local terrain and surroundings.
Dry stacking has proven to be the safer and
more sustainable option, not only for the mine
site, but for neighboring communities, too. Local
community acceptance is a highly important
business factor for mining customers, who often
find it difficult to secure water rights for their
operations. IM
Dry tails can be stacked
and blended to the local
environment
Paste thickening
FLSmidth’s Deep Cone® paste thickeners can
accommodate up to 20 times the solids mass
flow and 10 times the hydraulic loading of
conventional thickeners. Paste thickeners
produce underflows concentrated to near their
limit of pumpability by increasing the underflow
solids concentration. The deep tank design
maximises pulp concentration, and produces
uniform, non-segregating, paste consistency
JUNE 2016 Supplement | International Mining P11