Cobalt Blue Holdings Ltd (ASX:COB, OTC:CBBHF) is delivering strong progress in processing ore at the Broken Hill Cobalt Project (BHCP) for use in its Demonstration Plant at Broken Hill in Far West New South Wales, Australia.
Notably, the concentrator circuit has completed its first phase of test-work processing 500 tonnes of ore to produce 125 tonnes of concentrate.
This follows the completion of underground mining at the BHCP mine site southwest of Broken Hill with 4,500 tonnes of ore extracted.
Concentrator operations
In phase one, the focus was on gravity separation of cobalt-pyrite from the ore at the mine site. The ore was milled from 4mm top size to a target of 1.5mm top size using a roller mill and this simulated the use of a High Pressure Grinding Roll (HPGR) mill in the circuit.
The average grade of gravity circuit concentrate was 4,360 ppm.
Grade improvement
Commenting on the progress, Cobalt Blue’s CEO Joe Kaderavek said: “The 5x grade improvement from concentration is a key project enabler, with phase one of this large scale work continuing to confirm expectations.”
Pyrite concentrate.
Cobalt Blue expects a further 2,500-3,000 tonnes of ore to be concentrated over the next four weeks.
In phase two of the test-work program, a ball mill will be used to prepare finer feed material to the circuit (target p80 600-800 um).
Additionally, a float circuit will be used to recover the fine fractions of pyrite (90% are expected with these inclusions.
The company says these recoveries and upgrades are in line with its earlier technical studies.
Concentrate treatment
The treatment of cobalt-pyrite involves two key steps with the first being the conversion of pyrite into pyrrhotite and elemental sulphur, followed by the leaching of the pyrrhotite.
Solubilised cobalt is then recovered by precipitation as a mixed hydroxide with grades of 30% cobalt and 7% nickel (typical Pilot Plant results from 2021).
Commissioning of kiln with concentrate at the Demonstration Plant.
The Demonstration Plant kiln was successfully commissioned in September, with the first 5 tonnes of concentrate being processed. Feed rates to the kiln are 150-200 kilograms per hour.
Further work is ongoing to improve off-gas handling for recovery of the sulphur.
The next unit block for operations is the leach and mixed hydroxide precipitate (MHP) production circuits during October.