MINERAL SEPARATION
to extract even the finest of valuable
minerals means they are of the utmost
importance in today’s opex-focused
environment.
FLSmidth is aware of this given its
KREBS ® cyclones have been continually
optimised to do just this over its close
to 70-year existence as a technology.
FLSmidth’s SmartCyclone™ system
delivers when it comes to lowering
operating costs, increasing throughput
and reducing downtime for cyclone
circuits, according to the company,
improving cyclone overflow particle size
distribution, predicting and controlling
cyclone maintenance schedules and
optimising closed-circuit grinding
processes.
The company said: “This equates to monitoring
the performance of individual cyclones within a
circuit in real time, preventing unplanned
breakdowns from occurring and monitoring wear
rates while ensuring the cyclones are operating
optimally at all times. This translates into higher
efficiencies in the plant and, ultimately, higher
profitability.”
The SmartCyclone closed circuit grinding
optimisation system combines a variety of
FLSmidth patented technologies, including the
FLSmidth Krebs SmartCyclone wear detection
sensor technology and the Krebs patented roping
sensor technology (with patent-pending wireless
controller system). This technology immediately
identifies if a cyclone is malfunctioning, according
to the company.
The closed-circuit grinding optimisation system
also incorporates FLSmidth’s ECS/ProcessExpert ®
process control software with a new patent-
pending SmartWear™ cyclone maintenance
algorithm.
One of the largest benefits associated with this
software is the ability to develop a uniform
operation strategy that outlines the best way to
run a plant, according to FLSmidth. “Once this
strategy has been established, the necessity to
train new operators is reduced,” it says.
Cutting recirculation
Weir Minerals recently sought to optimise a
closed-circuit grinding process in the Philippines
with the use of its Cavex ® hydrocyclones.
According to the mineral processing company,
the installation of 19 Cavex 400CVX10 cyclones at
OceanaGold’s Didipio gold and copper mine led to
savings of more than $800,000/y through a
dramatic reduction in grinding circuit recirculation.
The Didipio mine has expanded throughput
over the last few years as it transitioned from open
pit to underground mining. This increased the
incumbent cyclones’ feed density beyond what
they could effectively manage, leading to a high
32 International Mining | MAY 2020
The SmartCyclone closed circuit grinding
optimisation system immediately identifies if a
cyclone is malfunctioning, according to
FLSmidth
circulating load, according to Weir.
The Cavex 400CVX10 hydrocyclones
significantly improved separation efficiency due to
their finely tuned spigot liner diameter and the
strength and corrosion resistance provided by its
cast housing, Weir said.
Thanks to these qualities, the introduction of
the cyclones reduced the circulating load from an
average of 620% to 374%, with the direct savings
in power consumption, ball consumption, cyclone
and pump maintenance costs exceeding
$815,000/y.
Gary Webb, Processing Manager, OceanaGold
Didipio project, said: “Having had good
performance from Cavex hydrocyclones at our New
Zealand sites (Macraes and Waihi), we were
confident that retrofitting a Cavex hydrocyclone
cluster at Didipio, with an increased number of
smaller cyclones than we had at the time, would
help reduce our problematic circulating load and
lever multiple benefits in doing so.
“The changeover to Cavex hydrocyclones has
exceeded our expectations, enabling higher
throughput and lower consumable costs without
being penalised in grind size.”
Mike Arakawa, Philippines Country Manager,
Weir Minerals, said the reduced circulation means
reduced power draw, fewer balls consumed and
less equipment wear; all of which creates a “more
sustainable mine”.
The performance of the cyclones is attributed to
the Cavex 360° laminar spiral inlet geometry
design, which provides a natural flow path into the
cyclone, Weir said. This shape allows the feed to
blend smoothly with rotating slurry inside the
chamber, reducing turbulence.
Slurry solution
In Zambia, Multotec has deployed an innovative
hydrocyclone solution of its own to allow a large
copper mine to develop, the South Africa-
based company says, a safe and cost-
effective tailings storage facility (TSF).
The planned TSF faced several specific
challenges, according to Frikkie Enslin,
Senior Applications Engineer responsible for
cyclones at Multotec. This included the
required throughput capacity and the area’s
flat topography. The mine’s process plant
pumps some 10,000 m³/h of tailings to the
TSF, requiring its final circumference to reach
about 19 km.
“The flat area around the mine meant
there was no suitable topography to provide
a natural dam,” Enslin says. “It was,
therefore, vital to create strong walls to retain
the slurry from the plant so that the integrity
of the TSF could be assured.”
Simple gravity separation and sun drying was
unable to create material firm enough to
constitute walls, according to Multotec, with, in
the early days of the plant’s operation, material
deposited by means of plain spigoting unsuitable
for walking on even after a month of drying in the
sun.
By contrast, Multotec’s 250 mm GV
hydrocyclones were able to deliver an underflow
discharge that could be walked on in just two
days, the company said. After a week, the material
could withstand the weight of an excavator.
The sheer volume of slurry being pumped into
the TSF, however, created its own challenge. The
cyclones had initially been mounted on metal
cradles, which were inundated within a couple of
hours. Extracting the cyclone and cradle from the
mud for the next placement was difficult and very
time consuming, according to the company.
“The customer needed a solution that would
keep the cyclone above the slurry level for longer,
and would be easier to move,” Enslin said. “To do
this, we designed a cyclone cradle that could be
attached to a long wooden pole, giving much
greater height, allowing the customer to leave the
cyclones in the same position for a much longer
time.”
Multotec’s used its in-house facilities to reduce
the weight of the cyclones, making them easier to
handle and manoeuvre, the company said.
“Constructed with a lighter metal, these tailor-
made units are industry leaders in terms of being
lightweight and are rubber-lined to ensure long
wear life,” Enslin said. “We also made some
innovative improvements to the vortex finders and
the cone sections, which are now metal spun.”
Other changes were made to speed up the
changing of a spigot and the moving of the
cyclones from one point on the TSF wall to the
next. The design now includes a threaded spigot
coupling and quick-release connections on the
cyclone.
The solution has been so successful to date