OZ Minerals’ Carrapateena operation in South Australia is gaining momentum with its processing plant running in excess of nameplate through a cost-effective and efficient debottlenecking strategy.

The latest sign of this strategy taking shape comes in the form of the installation of a second HIGmill from Metso Outotec.

This high-intensity grinding mill has been installed in parallel to the existing mill at the copper-gold operation to increase regrind capacity for all ore types to maintain optimal concentrate grades, the company says.

“We selected HIGmills due to the simplicity of installation and the total cost of ownership,” the company told IM. “As both HIGmills are identical, this allows for commonality of spares and predictable operation.”

The initial processing plant at Carrapateena was designed to produce at a nameplate of 4.25 Mt/y, yet, through debottlenecking and continued process improvement, the plant has recently run at annualised run rate in excess of 5 Mt/y, the company said. This is also an increase on the 4.6 Mt/y processed in 2021.

Like other ‘connected’ equipment within the Carrapateena processing plant, the new HIGmill has been fully integrated into a SCADA system monitored by the control room. It can also be monitored remotely at OZ Minerals’ Adelaide remote operations centre, the company added.

Beyond debottlenecking, OZ Minerals is planning a major expansion at Carrapateena through the development of a block cave operation, which was signed off by the OZ Minerals Board in early 2021.

The expansion, which will involve converting the lower part of the current sub-level cave into a series of block caves, is expected to prolong operations at the copper-gold mine, while boosting production to 12 Mt/y. This will see average copper production come in at 110,000-120,000 t/y and gold output average 110,000-120,000 oz/y from 2026, compared with production of 55,262 t and 89,778 oz, respectively, in 2021.

Under the expansion project, the company is targeting block cave 1 to begin operations by 2026 and block cave 2 by 2038.

While the block cave is being established, a second process plant will be built in parallel to the existing one. Below surface, construction of the second crusher is expected to be completed towards the end of next year, and processing plant optimisation is ongoing. These will help produce a concentrate to be transported to port and subsequently to smelters by ships, the company told IM.