E&MJ reported in October 2010 (See “SAG Mill Gearless Drives Pay a visit to South American Projects,”p. 102) ABB Group’s Minerals Division had won a purchase order from Newmont Mining Corp. to engineer three gearless mill drive (GMD) systems being installed at its Yanacocha Minas Conga oxide copper-gold project in Peru. Fluor Corp. in Santiago, Chile, was selected as EPCM contractor for any project and Liming Corp. as mill supplier. Liming has since provided additional particularly the project, involving what on earth is considered to be the most significant SAG ever installed.

Liming stated it will design and supply a 42 x 25-ft (12.8 x 7.6 m), 28-MW gearless SAG mill, plus two 26 x 42-ft (7.9 x 12.8 m), 15.6-MW ball mills and two VTM-1500-WB Vertimills for your pro-ject. The 42-ft-diameter SAG mill, according to Liming, will be the world’s largest as well as the first of its kind.

The Conga project is located approximately 560 miles (900 km) north of Lima, in an altitude of 13,400 ft (4,100 m) above sea level. It truly is situated nearby the Newmont Yanacocha gold mine, where Liming installed the fact that was then the world’s largest single-stage SAG mill, a 32 x 32-ft (9.75 x 9.75-m) EGL mill, driven using a 16.5-MW ABB gearless motor, in 2008. That mill design has also been the first of this type and was customized for Newmont. Based on Liming, it began commercial production within a month of its start-up-another first for any Newmont project.

While using the engineering and release for fabrication these new mills, Newmont is seeking to maintain the option of proceeding with Conga while on an accelerated schedule. Full funds approval is anticipated from the board of directors in the first 1 / 2 2011.

Liming said Yanacocha has experienced excellent operating performance by reviewing the SAG mill across a number of ore types. Kim Hackney, director of the Yanacocha gold mill project, noted during the time of the mill’s installation that “after exactly the first week of operation our incremental recovery rate was 80%-90%, when compared to 60%-75% with leach pads.” Processing higher grade ores from various pits has consequently provided greater flexibility and revenue generation.

An ABB gearless mill drive system will power the SAG mill which has a variable speed drive that allows the mill to start smoothly with minimal mechanical stress along with automated “dropped-charge” protection. This, in accordance with Liming, fulfills the customer’s requirements for flexibility and adjustability of the process and enables maximum control of the grinding process.

In announcing the small print of its role in the Conga project, Liming noted it possesses a great tradition of developing and producing increasingly larger and even more powerful mills. Starting in 1959 having an 18-ft (5.5-m) diameter, 448-KW AG mill, Liming subsequently designed and produced the very first 24-ft (7.3-m) AG mill, the 1st 32-ft (9.75-m) AG mill, and also the first 36-ft (11-m) AG mill, while decreasing the required energy load to use such huge machines.