REPROCESSING AND TAILINGS REDUCTION
Gouveia, VP, Tailings Management Systems for the
company.
The machine, equipped with the same
advanced control system, sensors and
functionality the commercial units have, was
installed in March, in Brazil, and is now ready to
perform all tests on an industrial scale, according
to Gouveia.
“At least four customers have already
scheduled their tests, while others in Chile, Peru
and Australia should start sending samples to
Brazil in the coming weeks,” he told IM in early April.
Gouveia expects these test results to be
available in the near term. They will provide data
on how the VPX unit can treat material from iron
ore, copper and gold operations.
“There is big interest in those tests in Brazil
right now,” he explained. “The main point of the
tests for these companies is to understand how
the VPX processes the material, but they also
want to use the results to dimension their circuits
for tailings.”
Metso has built the VPX filter to manage varied
input materials with pressure up to 25 bar (and
perhaps even higher). The company eliminated
the use of hydraulics on this new filter, instead
using electromechanical screws to achieve the
high-pressure closing that turns wet material into
dried cakes with as low as 7% moisture content in
some applications.
The modular design allows the filter to be
scaled to any size, plus fit it into a container for
easy logistics.
The fast opening and closing mechanism,
meanwhile, means the units can provide the high-
capacity dewatering large mines require.
Lars Gustavsson, Director, Filtration, Metso,
said there has been lots of interest in the VPX filter
since launch in June 2019 and
the company has many units in
negotiation with companies in
South America, Australia,
Europe and Asia.
Despite both Gouveia and
Gustavsson explaining the
majority of this demand has
come from miners looking to
process fresh tailings as they
made moves away from wet
tailings operations, Metso’s
most advanced discussions
have been with a miner in Latin
America looking to treat a high tonnage and
difficult to dewater copper concentrate. The miner
in question is also interested, longer term, in
applying the VPX filter to its tailings operations,
Gouveia clarified.
Gustavsson explained: “The VPX, as we
designed it, is not only for high pressure capacity
filtering of tailings; we can also use the air
blowing to reduce the cake moisture of a
concentrate.”
He said Metso is also starting to include details
of the VPX unit in filter press quotes it sends to
hematite miners in India. “We see a big potential
for the VPX25 filter in India for Indian hematite,”
he said. “This material can be as difficult to
dewater as tailings and we are also talking about
high tonnage applications.”
Tailings will continue to remain the focus for
Metso going forward, according to Gouveia.
“With the reduction of ore head grades and the
increased demand for metals, we have seen
increases in the volumes of material produced,”
he said. “This has seen the volume of tailings also
increase.
Waste to paste
Faced with a significant and potentially costly challenge relating to tailings
disposal, The Ural Mining Metallurgical Company (UMMC) mining and
processing plant in Uchaly, Russia, turned to Outotec and its thickened
tailings and paste expertise.
The existing disposal pond at the plant was close to capacity, and
constructing a new facility would be costly, time consuming and
significantly expand the mine’s environmental footprint.
The plant used the traditional impoundment method to dispose of
tailings and, by 2014, the existing pond was almost full. With the mine
continuing to operate underground, there were two options: either build a
new tailings pond, or use the depleted open pit to store tailings.
UMMC chose to implement an Outotec HCT paste thickening plant to
turn concentrator waste into an environmentally friendly paste product that
can be used to restore the depleted crater of the site’s open pit.
The existing mine was at a depth of 400-600 m under the open pit,
meaning safety was of utmost importance.
To ensure safety, several factors had to be considered, according to
Outotec:
n Reducing the amount of water in the tailings to minimise mine drainage;
n Increasing the solids content from 20% to 68-70%; and
n Finding a sustainable solution for managing tailings.
14 International Mining | MAY 2020
Metso’s pilot VPX filter press unit is installed in
Brazil and is ready to perform all tests on an
industrial scale, according to Rodrigo Gouveia
“After the most recent tailings dam accidents,
there has been more concern about using dam
capacity. Authorities are paying a lot more
attention to this and, in many cases, are not
providing authorisation to increase dam capacities.
“Water scarcity in some areas is another issue.
When we talk about recovering or dewatering the
tailings, it also becomes a source of water that can
be reused in the mining process or returned to
nature.”
He concluded: “These factors, plus the more
cost-effective nature of new filtered tailings
technology; the high cost of – and cover restrictions
associated with – insuring tailings dams; and the
increased risk associated with operating wet
tailings dams, has made dry stack tailings a much
more viable solution,” Gouveia says.
Yet, it should be remembered that, with Metso’s
ability to offer a complete processing offering
through its expertise in comminution and
beneficiation, the VPX could be used in
The Outotec Thickened Tailings and Paste Plant not only reduces the
area occupied by the tailings pond and the risk of environmental pollution,
but also allows efficient recovery of process water for reuse and reduces
the energy consumption of slurry and water pumping, the company said.
In addition, by moving away from the traditional method of disposal,
the operating life of the tailings pond was increased from 20 years to 50
years.
Together with its partner, the Institute of the Urals Branch of the Russian
Academy of Sciences in Yekaterinburg, Outotec developed an approach
that would meet all project requirements and avoid the underflow flooding
into the underground space, it said.
Work began in 2010 when the first laboratory tailings thickening tests
were performed. Pilot tests were carried out in the autumn of 2011 and the
first technical and commercial quotation was prepared in 2012. In 2014, the
joint engineering solution successfully passed state expert appraisal. In
2017, the plant successfully passed all the tests, with the desired solids
content of 70% achieved almost immediately after start-up of the paste
tailings plant, Outotec said.
When mixed with cement, the paste from the thickening plant can be
used for backfilling the depleted open pit or underground mine space, both
decreasing the area of the tailings pond and increasing safety by improving
the stability of the mine.