Tolu Minerals Ltd has passed another milestone on the path to restarting high-grade gold and silver production at the Tolukuma mine in PNG with final commissioning of the modular gravity recovery plant and testing underway.
Formal production and revenue generation will begin once final commissioning is completed with production targets for initial processing already prioritised.
This sees the progress to initial production gain momentum with Tolu targeting a monthly production rate of circa 2,000 ounces by the end of 2025.
Major milestone
Tolu Minerals MD & CEO Iain Macpherson said: “The commencement of final hot commissioning of the modular gravity gold plant is a major milestone in the development of Tolu and the return of Tolukuma mine to high-grade gold and silver production with commencement of revenue generation.
"The plant throughput and modular expansion capability is designed to match the mine’s production ramp-up schedule while enabling lower operating costs. Not only will it generate revenue, but it will also enable testing of more effective processing, including enhanced silver recovery.”
Plant during commissioning.
About the plant
As an integral component of the phased restart of the mine and acceleration towards initial production and revenue, Tolu procured and installed a modular, gravity gold recovery plant.
This will not only contribute to revenue by producing a gold/silver doré for sale but at the same time will allow advanced test-work on comminution performance and gravity recovery of gold and silver.
The modular plant was designed in conjunction with Appropriate Process Technologies (APT) in South Africa based on historical test-work and operating parameters from the 20-year period that Tolukuma mine operated as a high-grade gold and silver producer.
This plant, which was manufactured at APT and installed and cold commissioned during December 2024, features advanced gravity concentration technology.
Capacity is aligned with the planned mine production ramp-up while being significantly more power efficient than the existing higher throughput plant.
Modular plant general arrangement.
Towards restart
Cold commissioning with water only has been completed and hot commissioning with run of mine ore to assess the material flow, plant functionality and effective performance is well underway. This is projected to take up to 15 days before final certification of the plant is given for production to recommence.
Members of the Mines Inspectorate and APT commissioning engineers are supporting the process.
Training of management, operating and maintenance staff is also being undertaken whilst the commissioning engineers and inspectorate are on site.
The plant consists of five stages and two circuits - scrubber; crushing; hammer mill; gravity centrifugal concentration; upgrade shaking tables and smelting.
The scrubber underflow feeds the fines concentration circuit and the overflow feeds the coarse concentration circuit. The plant is currently being fed from stockpiled ore.
Tailings management
Tailings from this gravity recovery plant contain residual gold and is being stockpiled for retreatment once the existing leaching plant is recommissioned.
Management of the tailings incorporates the use of woven fabric tubes (geotubes) to enable rapid and efficient decanting of water. Initial capacity is 6 tonnes per hour, approximately 25% of the existing plant nameplate capacity.
Throughput will be ramped up during the year as the mine returns to production. The initial target is to achieve a monthly production rate approaching 2,000 ounces by the end of 2025.
"Industry-leading geotube technology is being deployed to temporarily store tailings to facilitate efficient and safe decanting of water and provide insight into the use of the technology as a potential long-term aide to tailings storage,” Macpherson added.