ORE SORTING
MineSense’s ShovelSense XRF solution has
been proven at Teck’s Highland Valley Copper
operation in British Columbia, Canada, where
the miner now has three systems up and
running in the pit (Credit: Teck Resources)
Re-think tank
The flowsheet evolution
With the mining industry re-thinking traditional processing
methods, a spot in the flowsheet appears to have opened for
ore sorting. Dan Gleeson speaks to some of the leading
technology providers in this space to find out how they intend
to fill this gap
hen last year Newcrest Mining
announced it intended to acquire 70%
of the Red Chris mine, in British
Columbia, Canada, the company stated within its
deal rationale that leveraging new technologies
such as mass sensing and ore sorting could
potentially turn the copper-gold operation into a
Tier One mine.
While few miners have been as upfront as
Newcrest in disclosing how such technology
could provide them with a competitive
advantage, it is certainly not the only company
considering the use of ore sorting.
In addition to numerous diamond, phosphate
and tungsten miners using sensor-based ore
sorting, the likes of Agnico Eagle Metals, Anglo
American, Hecla Mining, Silver Bear Resources
and Teck Resources have all come out in support
of the technology.
Whether it is bulk sorting, particle sorting or
some other way of separating ore from waste,
this is quite a turnaround for a group of
technologies that have been left out of the
process flowsheet for decades.
“It is slowly becoming clear that ore sorting
needs to be considered and evaluated as a key
potential unit process in the flowsheet,” Albert
du Preez, Senior Vice President of TOMRA Sorting
Mining, told IM. “You should evaluate it
appropriately as you would any other standard
mineral processing in the flowsheet.”
So, why has this only recently been
recognised? The answer is down to a
combination of factors.
First off – and a fact that is well documented –
miners are suffering from grade declines.
Companies are running to stand still when it
comes to retaining their ore grades. What was
viewed as an average grade copper discovery 15
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56 International Mining | MARCH 2020
years ago is today considered high grade. And
typically the lower the grade, the higher the
production cost per tonne of material
processed.
Water is another factor.
Related to declining grades, processing has
become more water intensive. This is a problem
in regions where drought conditions are
observed. And, even in regions where water is
not so scarce, the rise of social and
environmental concerns over water use has
increased the hurdles companies must jump over
to gain access to new water sources.
Energy prices and consumption are another
reason for the industry waking up to ore sorting’s
potential.
Comminution already accounts for close to 3%
of the world’s electrical energy use so anything
miners can do to reduce their power draw by
processing only ore, not waste, has a big impact
on achieving ambitious global climate change
goals. Miners are also addressing their power
draw needs in the face of soft prices for some
commodities.
Mining’s physical industrial footprint is also
part of this equation.
Whether it is tailings storage facilities, mineral
processing plants or open-pit mines, the need to
reduce mining’s footprint is constantly made
clear by NGOs at every AGM major mining
companies convene. The ability to produce more
metal within the same footprint is of significant
benefit when up against such pressure.
And, of course, the technology associated with
ore sorting has improved. With the advent of new
and more powerful sensors and analytical tools,
the accuracy, speed of ore detection and number
of minerals that can be ‘sensed’ has substantially
increased.
Traditionally when existing operations are set to
come to the end of their economic lives, an
expansion plan is tabled to increase throughput,
go underground, or mine a different orebody.
This normally involves a plant or fleet
expansion and, depending on the size of
operation, tens to hundreds of millions of dollars
of investment.
It is this scenario where ore sorting could
provide a much cheaper and efficient alternative,
according to Chris Beal, CEO of NextOre. Pursuing
such a solution can require a shift in mindset
from mining teams and engineers, however.
“In conventional mining, once it's on a truck or
in a bucket, the difference between one tonne of
ore in terms of its grade and the next tonne is
immaterial as, without a bulk sorting system,
there is no way to practically make any benefit
out of that,” he said.
Without a tool to accurately measure the grade
variation in ore following blasting and primary
crushing, miners have been left to assume the
rocks they feed through to the process plant are
homogenous. If metal production from the plant
happens to vary from week to week, they often
conclude that something must have gone wrong
downstream – an assumption often taken into
mine reconciliation meetings.
Beal, a mine engineer himself, said: “There
has not been a really reliable and accurate source
of the grade of material as it comes out of the
mine.”
Bulk samples and geological and grade control
work can be done at the face and in the pit, but
something that “covers 100% of the material and
is accurate to 0.01-0.02% is so outside of
business-as-usual for mining people that it is not
something they would consider in terms of
value”, Beal says.
In published data from Newcrest Mining’s
Ridgeway block cave mine (currently on care and
maintenance) – where ore was fed by a whole
grid of drawpoints to two different crushers,
through the crushers onto a single conveyor belt
– NextOre’s magnetic resonance (MR) technology
was able to show there was a considerable
amount of variability in the grade of the material
as it flowed past the on-belt magnetic resonance
analyser (MRA), according to Beal (see diagram,
right).
“For people to be able to watch in real time as
ore comes out of the mine and see the
statistically significant amounts of waste that are
being processed as ore as a result of the fact that