GPM Gold Project Armenia | Albion Process Case Study

How the Albion Process™ Quadrupled Gold Recovery

GeoProMining LLC, known as GPM, operates the Zod Gold Mine and Ararat Processing Plant in Armenia, producing gold and silver bullion. Their challenge was a common one in refractory gold processing - a large body of sulphide ore that their existing flowsheet could not treat economically. At their existing conventional Carbon in Leach (CIL) plant, the sulphide material from the Zod mine was achieving around 20-30% gold recovery. The value was there. The technology to unlock it was not.

The decision to install the Albion Process changed that, increasing recovery from sulphide concentrates from 20% to over 98%, exceeding both GPM's targets and the original design basis. The plant was commissioned in June 2014 and reached full capacity in three months.

The Challenge - Refractory Sulphide Gold at the Zod Mine

The Zod Gold Mine contained substantial sulphide ore that the existing flowsheet could not treat economically. In sulphide ores, gold is locked within the mineral lattice of iron sulphide and other sulphide minerals. Standard cyanidation, the basis of the CIL process, cannot access this gold without first oxidising the sulphide host minerals to liberate it.

GPM's existing CIL flowsheet was recovering only 20 to 30% of the gold in the sulphide material. The majority of the value was reporting to tailings. To extract that value, GPM needed to add an oxidative pre-treatment step before the CIL circuit.

In 2010, GPM approved a refurbishment project at the Zod Mine and Ararat Processing Plant. The scope included increased crushing capacity to handle the harder sulphide ore, a refurbishment and re-commissioning of the existing flotation plant, and the installation of a new Albion Process plant to oxidise the sulphide concentrate before it entered the CIL circuit.

The new flowsheet was configured so the CIL plant would treat both flotation tailings and the oxidised residue from the Albion Process.

The Solution - Albion Process Plant Design and Equipment Package

Glencore Technology provided a lump sum design and supply package for the Albion Process installation at GPM. The scope of supply covered the full grinding plant and oxidative leaching circuit.

The equipment package included:

• An M3000 IsaMill grinding package to finely grind the sulphide concentrate feed to the Albion Process

• Nine OxiLeach modular leach and slurry storage reactors forming the Albion Process leach train

• 54 HyperSparge oxygen injection spargers, designed to achieve supersonic injection of oxygen gas for improved reaction kinetics

• A 10-metre diameter high-rate thickener

• A 120 tpd oxygen plant

• A 140 tpd limestone grinding plant

All structural steel, piping, platforms, stairways and support structures were supplied by Glencore Technology, along with full civil and foundation design. Construction was carried out by GPM, with supervision provided by Glencore Technology.

The design basis for the Albion Process plant at GPM was oxidation of 100,000 tonnes per annum of concentrate, targeting overall production of 100,000 troy ounces of gold per year from concentrate and flotation tailings. The design recovery of gold from the Albion Process residue was 92%.

For details on how the oxidative leaching stage works within the Albion Process, see the technology overview.

The Results - Exceeding Design Targets Across Every Metric

The plant was commissioned in June 2014. Ramp-up occurred over the remainder of 2014, and the plant achieved full capacity within three months of commissioning.

The results exceeded GPM's targets and the original design basis across every key metric.

Recovery. The design recovery of gold from the Albion Process residue was 92%. The plant frequently achieves over 95% recovery. Overall plant-wide recovery was designed at 86%, but GPM typicallyachieves 88%.

Production volume. The plant was designed to treat 100,000 tpa of concentrate. It is, in fact, treating 120,000 tpa, with overall gold production of 120,000 troy ounces per annum.

Recovery from sulphide material. Recovery from sulphide concentrates increased from 20% to over 98%, more than quadrupling the result from GPM's original CIL-only flowsheet.

Stability under increased load. The gold recovery has remained stable even as throughput increased above design. Increased production normally places pressure on recovery as equipment is stretched. GPM have successfully maintained recovery above the design target using the Albion Process.

GPM are evaluating an expansion project comprising a second line of an Albion Process plant.