Based on the positive results of the initial metallurgical test work programme in 2021, and mineralogical investigation, metallurgical consultants MJO Ingeniería y Consultores en Metalurgia SpA (MJO), Chile, have developed a number of metallurgical test work programmes designed to demonstrate that the Omitiomire chalcocite mineralisation is amenable to processing by chloride-curing, acid heap leach and Solvent Extraction/ Electro-Winning technology (SXEW).
This processing method accounts for 20% of worldwide copper production and is used to good effect in the arid regions of North America, Chile, Peru, and China.
Benefits of SX/EW:
- cost effective
- low-impact
- low water consumption
- high-purity cathode
April 2023
Phase 2 of the metallurgical test work programme, using full-height columns, demonstrated that 77% Cu recovery with 44kg/t acid consumption and a 300 day leach cycle was achievable using standard chloride and sulphuric acid leach. However, it was noted in this test work that nearly all the acid was consumed in the first metre of the column, while maintaining over 70% copper recovery in the subsequent metres. This lead to the development of the next phase of test work to develop a concept of high-Cu and low-acid solution in the leaching process.
October 2023
The Phase 3 metallurgical test work, using three mini-columns, demonstrated the technical feasibility of using a high-Cu low-acid leach solution to significant reduce the acid consumption to 10-15kg/t and reduce the leach time to estimated 200 days, while also increasing the recovery to 80%.
January 2024 – Ongoing
Phase 4 test work, currently being undertaken, is designed to develop the process further to BFS level of confidence with 10x full-height columns testing various leach conditions to optimise recovery, acid consumption and leach time.
The chalcocite portion of the mineralisation represents approximately 90% of the contained copper. The remaining copper oxide minerals are readily leached in dilute sulphuric acid alone.
The SX/EW plant is expected have a nominal capacity of 25-30,000tpa of copper cathode.
Omitiomire Project General Process Flowsheet