:: Outokumpu’s World Class SAG Mill Design Answers Challenges of the Remote Congo

One of the latest string of grinding technology sales announced by Outokumpu Technology includes some highly innovative engineering built into one of the world’s largest dual pinion variable speed SAG mill drives.

The 32 ft diameter, 20 ft long SAG mill with 12,000kW of installed power is custom engineered for the remote and challenging conditions it will encounter at First Quantum Minerals’ Frontier project in the Democratic Republic of Congo.

This project, for which Outokumpu will also supply ball mill technology, is situated close to FQM’s $US200 million Kansanshi copper and gold mine in Zambia, where Outokumpu has recently supplied a comprehensive package of grinding, thickening and flotation technology.

Frontier’s new trunnion-supported SAG mill features variable speed capability, allowing greater production flexibility and the ability to cope efficiently with large ore variations. The advanced technology utilised in Frontier’s Hyper SER Drive^® ensures the mill can operate both above and below the synchronous speed of the motor.

This proven design ensures extremely high efficiency of the mill’s operation, allowing easy management of variable feed rate and feed competency. The design also facilitates optimised handling of any variations in ore, on both a daily basis and throughout the mine life of the orebody.

The variable speed also ensures optimised trajectory for the charge during mill operation, minimising unnecessary wear of the mill lining, explains Oskar Gustavson, global technology manager for grinding at Outokumpu.

"The beauty of this customised system is that it is designed for optimal operation and can cope with pretty much anything. This is critical especially at remote sites which can be prey to challenging situations such as voltage variations and thus unavoidable downtime. The Hyper SER Drive^® can transfer to fixed speed mode during under-voltages, then transfer back to variable speed when the supply voltage stabilises, ensuring no costly mill stops occur."

Frontier’s mill is fully customised to the project’s needs and uses the same drives as the two already installed at the nearby Kansanshi site. This facilitates benefits such as commonality of spares and services, also particularly critical for remote sites.