AG/SAG mills accomplish the same size reduction work as 2 or 3 stages of crushing and screening
The feed size for these mills is limited to the maximum size that can be practically conveyed and introduced into the large mill feed chutes. And the product of the large AG/SAG grinding is either a finished size ready of processing, or an immediate size for further grinding in a ball mill, pebble mill, or a VERTIMILL® or a stirred media detritor (SMD).
Simplifying wet grinding with Metso AG/SAG mills
AG/SAG mills are often the optimum solution for wet grinding (achieved in a slurry 50 to 80 percent solids). AG/SAG mills can accomplish the same size reduction work as two or stages of crushing and screening, a rod mill, and some or all of the work done by a ball mill. All because of the range of mill sizes available, AG/SAG milling extends itself to many applications.
While the optimum circuit design should be determined during testing of the ore, common flow sheets include:
- AG – SS (Single Stage)
- AG in closed circuit with a crusher
- AG with a crusher and a ball mill
- SAG – SS (Single Stage)
- SAG with ball mill/VERTIMILL®
AG/SAG mill drives
Mill motor gear drives can be offered for AG/SAG grinding mill as dual pinion drives with power deliver of up to 20 MW (2 x 10,000 kW), and this can be accomplished on mill sizes up to 36 ft in diameter. Gearless mill drive (GMD) technology has further expanded the use of large AG/SAG milling allowing Metso to produce the world's largest SAG mill of 42’ in diameter drawing power at 28 MW. Today, Metso is the world leading supplier of gearless AG/SAG mills operating globally.
- The mill shell actually becomes the rotating element of a Low Speed Syncronous (LSS) motor
- Mill speed is adjusted by changing the frequency of the current to the motor
- LSS motors and GMD motors can be used to inch the mill during plant down times to prevent lock charges, and to maneuver the mill for liner changes and other preventative maintenance.