Aeris Resources Ltd (ASX:AIS, OTC:ARSRF) is making strong progress on a feasibility study for the 100%-owned Stockman Project in Victoria with metallurgical ‘proof of concept’ test-work improving overall recoveries for copper along with zinc and gold.
A modified flotation circuit has produced export-quality copper concentrate and bulk concentrate (copper-zinc-gold-silver) with significantly improved recovery of all metals.
In a highly encouraging development, metal leaching of bulk concentrate in an Albion Process™ indicates leach recoveries of +98% for copper and zinc.
Improved recoveries
The overall copper and zinc recoveries are now above 90% and gold recoveries have been significantly improved with opportunities to improve silver recovery identified.
This work provides the catalyst to improve Stockman Project economics by way of increased revenue from higher metal recoveries and a material reduction in physical plant footprint, capital, operating costs and carbon emissions of the ore processing plant.
Enhanced economics
Aeris’ executive chairman Andre Labuschagne said: “These latest metallurgical test-work results validate our view that the Albion Process has the potential to significantly enhance the overall economics of the Stockman Project.
"The plan is now to further study, engineer and complete detailed metallurgical test-work on the modified flotation flowsheet at the ore processing plant, producing an export quality copper concentrate and a bulk concentrate containing copper/zinc/gold/silver for further treatment.
"This will result in a simpler flowsheet for the ore processing plant, enhancing project economics through a smaller physical footprint, lower capital and operating costs and reduced carbon emissions (reduced energy consumption).
"The bulk concentrate will be processed through an offsite Albion Leach facility, producing saleable copper, zinc and precious metals products.
"The Albion Leach test-work results shows +98% recoveries of both copper and zinc from the bulk concentrate, bringing overall recoveries of these metals to >90%, whilst also significantly improving overall recovery of gold.”
Feasibility study work
This test-work follows a recommendation in the Stockman Project Feasibility Study that a modified flotation and metals leaching process be investigated.
An alternative processing route would replace the conventional selective flotation plant, which would have produced separate export quality copper and zinc concentrates, for metal recovery by smelting.
This conventional process would result in modest metal recoveries, require extensive use of reagents and high power consumption for fine grinding to liberate the copper and zinc minerals.
The high power consumption and mine’s isolation would require a diesel or gas power station, with attendant carbon emissions, at a significantly higher cost than grid power.
Alternative route
As a result, the alternative route investigation has conceptually tested the use of proven metal treatment technologies - the Jameson cell for improved froth flotation and the Albion Process for metal leaching.
This was designed to proof, at a laboratory scale, the improved metal recoveries and lower power and reagent consumption for the ore processing plant, through inclusion of an alternative processing route.
The investigation included a conceptual engineering design of a smaller, simpler and more sustainable (lower carbon emission) ore flotation processing plant, as well as the remote Albion Process leach plant.
With the success of this work, detailed test-work and Options Engineering of a simplified ore treatment and Albion processing plants can now proceed.
Engineering study
Results from the test work program have enabled an updated engineering study (conceptual) for the ore processing plant located at the mine and the offsite Albion Process plant.
The results from the latest and previous flotation tests have been used to simulate the use of Jameson cell flotation equipment in the ore processing plant. Simulation of Jameson cell performance from standard laboratory flotation test results is common practice.
The reason for engineering a Jameson cell-only flotation circuit is to significantly reduce the size of the ore processing plant at the mine, compared to a conventional sequential flotation layout.
A smaller plant footprint will reduce vegetation clearing, environmental offsets and land disturbance at the mine. The smaller plant will also benefit from lower capital for the building construction.
Yet to be determined are the power and carbon emission savings from running a smaller simpler flotation plant.
More sustainable project
The engineering study has recommended conceptual level flowsheets, equipment sizes and reagent consumption rates for the Albion Process plant. The fast kinetics of the leaching of the Stockman bulk concentrate allows for a modest size plant.
Further plant options including site layout, general arrangement and cost estimates require more work before public reporting. The final selection of the most likely intermediate products for copper and zinc metal will influence the plant design including further product refinement, as required.
From a plant location perspective, the concept is for the Albion plant to be remote from the mine site but within reasonable trucking distance.
The ‘proof of concept’ engineering and test-work for the modified flotation and Albion Process plant have proved that the Stockman Project offers material upside in metal recoveries and estimated project economics.
The Albion Process in combination with a simpler ore processing plant, either in a conventional or Jameson cell flotation configuration, will enable the development of a more sustainable project, resulting in significantly reduced carbon emissions and less land clearing impacts.
What comes next?
The next phase of test work and options engineering will focus on:
- Optimising the grind size, leaching chemistry and residence time to support the flotation plant and Albion Process plant design;
- Selection of intermediate copper and zinc products and marketing payability estimates; test further product refinement paths and value;
- Improved silver and gold recovery and saleable product pathways;
- Ore variability testing;
- Potential economic recovery of sulphur through the production of sulphuric acid (used in the leach process); and
- Updated estimation of capital and operating costs.