Metso to Build Largest SAG Mill for Newmont’s Minas Conga Project
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 Metso Corp. as mill supplier. Metso has since provided additional particularly the project, involving what on earth is considered to be the most significant SAG ever installed.
Metso 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 Metso, 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 Metso 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 Metso, 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.
Metso 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 Metso, 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, Metso 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, Metso 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.
In 1986, Metso unveiled the first gearless SAG mill, that’s grown through stages of 38 ft (11.6 m) and 40 ft (12.2 m) about the size of the giant unit slated for Newmont. According to Randy Will, vp, capital mining sales-Americas, Metso looks forward to developing this new mill since the next standard range. “Con-
centrator plants keep getting larger and larger, and this new mill is a significant development for the future.
“A single line grinding circuit which has a 42-ft SAG mill permits much higher concentrator throughputs, as compared to using a dual line grinding circuit using two SAG mills,” Will said. “The capital financial savings using one line versus two are significant.” He noted the newest design will not compromise the original aspect ratio.
Will even pointed out Metso provides larger cone crushers and Vertimills. “This becomes more important for the reason that copper grades decrease. More ore needs to be processed to meet the equivalent of current copper production. That’s where customers need the increase in mill size that Metso are able to provide.”
New Ownership, Technology Developments in Sample Prep
In an industry which takes considerable pride to use ability to blast and move massive amounts of ore and rock inside surface and underground mining operations, it’s an easy task to overlook many of the more delicate technologies that play important roles while in the value chain from ore to finished product. Sample preparation is among one of those areas, and recent announcements within this sector illustrate the latest value and sophistication of the technology.
For example, FLSmidth announced on December 5 it had made an arrangement to acquire ESSA Australia Ltd. for as much as DKK 170 million ($30.9 million). ESSA makes a speciality of the design and manufacture of sampling and sample preparation equipment for the minerals and mining industry. According to FLSmidth, ESSA is active in many market segments including mineral sample preparation, laboratory equipment, industrial solids preparation, mineral sizing, metallurgical testing, run of mine sampling, replacement parts and maintenance, laboratory and sampling automation.
At a comparable time, Illinois, USA-based Buehler, a manufacturer of scientific equipment and supplies for material preparation and analysis, introduced its EcoMet 250 Pro grinder-polisher with AutoMet 250 power head. New capabilities include the ability to store and recall 32 sample preparation methods via touchscreen display controls, a Zaxis (Z-axis) function that removes material by depth as opposed to time and power head speed adjustments from 30 to 60 rpm.
Using the manufacturer, the EcoMet system’s programmable and adjustable functions increase consistency and repeatability, ensure better flatness and enable method optimization in comparison to manual grinding. An optional PriMet Pro modular dispensing satellite uses peristaltic pumps, not mist technology, to distribute lubricant, diamond and colloidal polishing suspensions. Controlled dispensing is claimed to supply repeatable results irrespective of the operator, and to lower consumables costs by preventing over-use.
Buehler’s Rick Wagner, manager of specialty market development, noted mineral preparation is frequently done by hand. “Minerals are extremely brittle, and they also can have distinctive hardness variations inside a sample,” he was quoted saying. “Testing and lab personnel believe they must have a ‘hand touch’ for the sample to prevent a pull-out or over-preparing it. Unfortunately, manually prepared samples frequently have planar issues and exhibit variations between samples.”
As it also allows manual sample preparation, the semi-automatic system provides several tools that guide increase quality. Variable speed adjustments give you the flexibility to custom tailor methods to the type and hardness of a mineral. Power head speeds greatly affect abrasive use. Higher speeds impact the abrasive aggressively, while slower speeds are gentler for the sample. The prior system operated at either 30 or 60 rpm, whereas the newest AutoMet 250 adjusts between 30 and 60 rpm in 10-rpm increments.
Semi-automatic material removal likewise helps ensure better flatness-critical when producing measurements-because it eliminates hand rocking. And, the Zaxis function enables targeting a specific plane. After determining the standard depth of cloth needed to be removed to reach the damage-free/stress-free section, personnel can program the EcoMet 250 Pro to clear out a specific amount of fabric, rather than programming it by time.
“In mineral preparation, samples are generally prepared to 30-micron thickness,” said Wagner. “The Zaxis function easily allows targeting that thickness. Then, once the sample approaches target thickness, the AutoMet 250 Pro single force sample holder accepts glass slide holders for your final polishing steps.”
Operating parameters, for example speed and force, are adjustable while in the preparation sequence. A pause function allows the operator to stop operation in a step, remove an example for examination, then complete that step another time.
Buehler also offers the EcoMet 250, a non-programmable grinder-polisher with push-button controls and digital readouts.
