Metso has been selected to design and supply a 42 x 25 ft, 28 MW gearless SAG mill, plus two 26 x 42 ft, 15.6-MW ball mills and two VTM-1500-WB Vertimills for Newmont Mining Corp.’s Yanacocha Conga copper-gold project in Peru. The 42-ft-diam SAG mill is the world’s largest and is the first of its kind.

The Conga project is at its feasibility stage, and with the engineering and release for fabrication of these mills, Newmont seeks to maintain the option of proceeding with the Conga project with an accelerated schedule. Full funds approval is expected from the board of directors in the first half of 2011.

The Conga project is located approximately 560 miles north of Lima, at an altitude of 13,400 ft above sea level. It is situated near the Newmont Yanacocha gold mine, where Metso installed what was then the world’s largest single-stage SAG mill, a 32 x 32 ft EGL mill, driven by a 16.5-MW ABB gearless motor, in 2008. That mill design was also the first of its kind and was customized for Newmont. It was in commercial production within one month of its start-up - another first for a Newmont project.

Yanacocha has consistently seen excellent operating performance from the mill across a wide range of ore types. Plant availability has also been outstanding, with reliable operation a constant throughout the first two years of operation. Kim Hackney, project director of the Yanacocha gold mill project, noted at the time of the mill’s installation that “after just the first week of operation our incremental recovery rate was 80%-90%, compared to 60%-75% with leach pads.” Processing higher grade ores from various pits has consequently provided greater flexibility and revenue generation.

Metso is a frequent supplier of mills for Newmont and has a long and fruitful relationship with the company. According to Patricia Downing, project director for Conga, “Newmont is all about establishing long-term alliances with quality suppliers to ensure consistent results for its projects. The Conga project will benefit from the increased size and capacity of this Metso 42 ft SAG mill as it will contribute to stabilizing production in periods of harder ore.”

This project also reinforces Metso’s continued good relationship with ABB and provides the groundbreaking challenge of engineering the GMD system for the world’s first mill above 40 ft in diam.

The ABB gearless mill drive system will power the SAG mill with a variable-speed drive that allows the mill to start smoothly with minimal mechanical stress and with automated ‘dropped-charge’ protection. This fulfills the customer’s requirements for flexibility and adjustability of the process and enables maximum control over the grinding process.

For more information, visit www.metso.com.