REPROCESSING AND RETREATMENT
A new treatise
Over the past few decades, several innovative processes
have been commercialised that have allowed waste to
become valuable ore. Dan Gleeson examines the impact
these technologies are having on the reprocessing and
retreatment landscape
ining companies continue to look for
the low hanging fruit at their
operations, with many observing the
best way to get more metals or minerals out of
their landholdings is to reprocess or retreat
existing stockpiles or concentrate streams.
Such a strategy can increase mining
companies’ product yields and improve their
environmental footprint. It also costs very little
when compared with developing new orebodies.
The trick to successfully extracting value out
of these lower-grade operations is finding
equipment that can easily slot into a flowsheet
ahead of or after the processing plant.
It is these modular solutions that are making
a big difference in the current reprocessing and
retreatment sector.
M
Detox and more
A company offering such solutions is Jakarta-
and Perth-based GreenGold Engineering.
The company’s ReCYN™ process has a
unique selling point when it comes to the
detoxification of gold plant tailings, according to
CEO Malcolm Roy Paterson.
“The majority of other processes are negative
as there is a cost involved – you’re adding in
chemicals to destroy the free cyanide and metal
complexes; that is a cost,” he told IM.
“With the ReCYN resin process, we recover
the free cyanide and metal complexes –
effectively how we detoxify. We actually take it
(cyanide and metal) out of the tailings.”
This enables companies to recycle the cyanide
– cutting the amount they need to buy – and
further process the metals into a saleable form.
The latest company about to realise these
benefits is PT Agincourt Resources, which
signed an agreement with GreenGold for the
8 International Mining | MAY 2019
design and installation of a ReCYN module to
detoxify tailings and recover cyanide and copper
at its Martabe gold-silver operation in Sumatra,
Indonesia.
GreenGold will deliver the project with
preferred fabricators for specialist equipment
packages, the company said.
The contract comes after a 2018 Whittle
Consulting report said the “innovative resin-
bead absorbent” could reduce cyanide
consumption by 50% at the operation, in
addition to recovering the metal complexes
previously destroyed or sent to tails.
The consultancy said adopting the
technology could provide a $126.9 million
upside to the Martabe mine economics.
The Martabe mine has a resource base of
some 7.4 Moz of gold and 69 Moz of silver and,
according to Paterson, the ReCYN process will
enable the operation to recover a couple of
tonnes per day of copper and cyanide.
It will also provide the operation with further
benefits, Paterson said.
“One is the metal recovery – because they
can increase cyanide levels (thanks to the
recycling), they can get better metal recoveries,”
he said. “The other major benefit is the
operating costs have been reduced so they can
effectively bring down their cutoff grade and
increase their reserves.”
This will become even more telling as the
Martabe mine deepens, according to Paterson.
“As the Martabe operation gets deeper, they
encounter more copper and that would normally
be seen as uneconomic as they could not treat
it. But, with this process, it becomes a resource
or reserve. Using ReCYN will increase the
amount of ore they can treat.”
While detox applications will continue to
“With the ReCYN resin process, we recover the
free cyanide and metal complexes…We actually
take it (cyanide and metal) out of the tailings,”
GreenGold Engineering’s Malcolm Roy
Paterson says
make up the bulk of the ReCYN process’
demand, Paterson said there are many primary
gold operations that have an inherent “problem
copper” element.
He explained: “They have copper that is at a
level deemed too low to be a standalone copper
project but high enough to cause trouble.”
The company is working on two such projects
in Australia where the presence of copper is
making them uneconomic using the existing
flowsheet. “Using our process, we can turn
them around and make them economic,” he
said.
The Martabe installation is the company’s
third ReCYN installation; all of which are in
Indonesia. The first has been operating for
around six years and the second for around six
to 12 months, Paterson said.
He believes Martabe could be one of three or
four projects to be confirmed this year, with
another possible eight lined up for 2020.
“The technology is about at the state where it
is emerging. We don’t think it is going to take
off at a huge rate because of the conservatism
in the mining industry, but it has been gaining a
lot more interest of late,” he concluded.
Cutting gold losses
IM reported on Gekko and CSIRO’s OnLine Gold
Analyser (OLGA) in the same feature last year,
and it appears commercialisation of this real-
time analysis technology is edging closer.
OLGA is designed to measure gold content in
a slurry or solution stream, delivering an
updated sub-parts per million (ppm) Au
measurement every 10 minutes to enable real-
time monitoring and adjustment of process
systems to minimise gold losses.
Complementing Gekko’s existing Carbon
Scout measurement system, Gekko said OLGA
enhances its metallurgical accounting system,
which is currently under development in
collaboration with Rockwell Automation.
Greg Rasmussen, Gekko’s Vice President
North America, updated IM on developments
with OLGA.
“Working with CSIRO, the first OLGA module,
our Alpha version, was deployed to a site in
Australia,” Rasmussen said.
This unit was commissioned in December,
with Rasmussen admitting, “it has gone through
some start-up challenges, but with being
supported by Gekko and CSIRO personnel,
these challenges have been resolved and the
unit is working successfully”.
The main objective now for the Alpha site is