While all of these processes exist in mining around the world - this is the first time they have been brought together in an innovation that is unlocking cobalt from pyrite in these steps:
Ore is crushed to approx. 1 mm, and a pyrite concentrate is recovered using a combination of gravity and flotation unit operations.
The pyrite concentrate is thermally treated under an inert atmosphere to produce artificial pyrrhotite (calcine) and elemental sulphur. The sulphur is condensed from the kiln off-gas and turned into solid prills.
The pyrrhotite is forwarded to a low-temperature, low-pressure autoclave for leaching. The leach residue is removed by filtration and further processed for sulphur recovery by remelting. The leach solutions are advanced through various minor metals removal steps (precipitation, ion exchange, and solvent extraction) to remove iron, copper, zinc, manganese. The cobalt and nickel are precipitated as a mixed-hydroxide (MHP) intermediate.
The MHP is then refined for production of high purity cobalt sulphate heptahydrate. The target recovery from ore to product for cobalt is 85–90%.