In April 2003 plant upgrades in the Low Grade' Cadia Hill circuit were undertaken in order to improve concentrate quality and metal recoveries from the flotation circuit. The major changes involved:
circuit reconfiguration to allow all concentrates to be reground to less than 38 m prior to final cleaning;
increasing ball charge in the regrind mill to fully utilise all of the installed power;
desliming of the cleaner scavenger concentrate to improve the circuit water balance; and
the inclusion of a gravity concentrator in the regrind circuit to recover more free gold to bullion.
Once the flotation circuit had stabilised under the new operating conditions concentrate launder modifications and increased froth crowding on the scavenger flotation cells permitted the introduction of stronger collectors without compromising concentrate quality or circuit stability.
Twelve months on, the copper concentrate grade has increased by two per cent and metal recoveries increased by three per cent and seven per cent for copper and gold respectively. The project capital outlay of approximately $2.0 million has been repaid in less than three months. This paper will review the project from the design, construction and commissioning perspective as well as the subsequent debottlenecking exercise that was required to eventually yield the full benefits of this upgrade.