FLOTATION TECHNOLOGY
FLSmidth combines the best of two
worlds
FLSmidth has recently released two major
products that advance flotation recovery. The
mixedROW Flotation System, which combines the
best attributes of two technologies to create
next-level results, is now ready to hit the market
along with a new Froth Recovery Upgrade Package.
“Flotation systems are a vital technology in
minerals processing and extraction. But despite
their overall effectiveness, particles of valuable
ore still get disposed of along with waste material.
Additionally, the energy consumption that flotation
systems require to function effectively is high. So
while flotation systems are necessary when
recovering ore, making them more sustainable and
energy-efficient has been a challenge.”
FLSmidth’s desire to improve and innovate has
led to the development of the mixedROW
Flotation System. It is a design that combines
two machines – nextSTEP forced air and WEMCO
self-aspirating technologies. “It provides the
solutions to challenges presented by older
flotation systems by combining these two cells to
produce a system that is much more than the
sum of their individual parts. In short, mixedROW
provides boosted productivity, a reduced
environmental footprint, and higher profits.”
The mixedROW Flotation System is the first of
its kind, as it exploits the characteristics of two
separate technologies at the same time. The
nextSTEP machines are placed at the beginning
of the row, where it can recover coarse material
using the least amount of energy possible.
Because of this positioning, the mixedROW
lowers energy consumption by between 15-40%,
and increases recovery by up to 5%.
The WEMCO machines are placed at the end of
the row, which increases both coarse and fine
particle recovery, as it is capable of treating a
wide range of particle sizes. The elevated rotor
position within the machine also reduced energy
consumption, as the froth only has a short
distance to travel.
“mixedROW also has the lowest head loss on
the market, as its carefully engineered system of
dart valves allows for efficient transfer of slurry
from one tank to another without significant
losses. mixedROW can be configured to suit
whatever the customer needs may be. It can be
adapted to whatever application it is needed for,
making it a highly flexible and effective
solution.”
Quite recently, flotation loses were commonly
50%, reaching as high as 90% for coarse
particles. Looking to resolve these substantial
losses, FLSmidth’s goal was to create a product
that allowed customers to have more control over
the froth recovery process. With this goal in
mind, the Froth Recovery Upgrade Package was
designed. It offers a range of equipment that has
30 International Mining | NOVEMBER 2019
been engineered to improve the productivity of
froth recovery, while minimising the losses of
valuable particles, saving costs overall.
The Froth Recovery Upgrade Package finds
solutions to flaws found in original froth recovery
technology. Features include:
n Actuators –control the position of the
improved dart valves inside the flotation cells.
n Level sensor – provides a new design with no
moving parts, that are used to sense slurry
levels accurately. FLSmidth offers the most
accurate technology on the market.
n Radial froth crowders – designed for greater
flexibility and control, they are used to reduce
top-of-froth surface area and to increase froth
movement to the nearest radial launder,
allowing for either deeper froth or faster froth
removal.
“The result of these newer and improved
designs is quicker reactions to flow and slurry
density changes, which dramatically boosts the
performance of flotation machines. All the
elements working together in combination with
radial froth crowders, means this package will
deliver better recovery at the same grade or
increased grade at the same recovery, making
this package better than the sum of all its parts.”
Outotec’s flash flotation successes in
Russia
Polyus is the largest gold producer in Russia and
one of the top ten gold miners globally with the
lowest cost position. Located in one of Russia’s
most prolific gold mining provinces, Olimpiada is
Polyus’ largest operation. The mine began
production in 1996 and currently accounts for
over a half of the company’s total gold output.
The ore mined at the site is processed at
three plants with a combined capacity of 13
Mt of ore annually.
Polyus has a long relationship with Outotec. To
date Outotec has modernised seven existing
thickeners and supplied a 30 m thickener and
automation equipment to their concentrator
plants. Outotec has also supplied leading-edge
automation and analysis technologies for Polyus
to help optimise their flotation circuit
further, including PSI 300i on-online analyser,
FrothSense froth imaging analysis camera,
LevelSense slurry/froth interface tool and an ACT
advanced control system.
SkimAir is designed for flotation in the
grinding circuit to process cyclone underflow
where heavy minerals concentrate. The SkimAir
unit reduces overgrinding of valuable mineral
particles, provides a more stable feed to
the conventional flotation circuit and improves
dewatering with coarser final concentrate.
Benefits include minimised loss of fines due to
overgrinding, improved overall recovery,
increased mill throughput and improved
dewatering. SkimAir technology also has a small
footprint and can deliver benefits such as lower
energy consumption in the downstream
conventional flotation circuit.
The SkimAir flash flotation project commenced
at Olimpiada in Autumn 2014 with pilot and
laboratory scale testwork. The first trial was
conducted at the Olimpiada ZIF-3 concentrator
(ZIF is a Russian acronym for gold recovery
concentrator). This concentrator has 3 mm
gravity circuit pre-screen underflow. In the trial a
side cut from this gravity circuit pre-screen
underflow was directed to a SkimAir 3 test unit.
“The results proved that the Olimpiada type
ore was suitable for the flash flotation
technology. The customer decided to proceed
with front-end-engineering of a full scale SkimAir
installation. Following the completion of this
front-end-engineering and based on the
promising pilot test results, Polyus ordered one
SkimAir 500 flash flotation cell in 2016. The cell
was installed in the Olimpiada ZIF-4 concentrator
on one of the parallel processing lines, enabling
comparison of lines with and without SkimAir.”
As part of the SkimAir scope, Outotec provided
a range of services to help Polyus achieve target
results. The services included full on-site cover
during installation for commissioning phase, as
well as ramp-up of the SkimAir unit to operating
mode and optimisation of process parameters.
The Olimpiada ZIF-4 concentrator has two
parallel process lines which process slightly over
1,000 t/h of crushed ore. Prior to the
implementation of the SkimAir flash
flotation cell, both processing lines consisted of
a SAG-ball mill grinding circuit. This SAG mill
discharge is screened with a 12 mm screen. The
screen overflow is crushed and recirculated back
to the SAG mill. The screen underflow is fed to a
gravity separation stage which is designed to
recover the gravity recoverable gold. The tails of
the gravity separation are pumped to
a secondary hydrocyclone, and these tails are
then fed to the ball mill.
The ball mill discharge is pumped with the
SAG mill discharge to the primary hydrocyclone.
Overflows of the primary and secondary
hydrocyclones are fed to two parallel
conventional flotation circuits. The
flotation concentrates are further treated in a
leaching circuit.
The SkimAir was installed in processing line
two of the grinding circuit. The SkimAir’s duty
was to process the gravity separation prescreen
underflow. The tails of the SkimAir were pumped
to the gravity separation, whilst the concentrate
went to a separate gravity separation stage. As
SkimAir was installed in just one of the two
parallel processing lines, it was easy to compare
performance between the lines with and without
SkimAir technology.