Autogenous and Semi-Autogenous Mills
Disintegration and size reduction of some ores is possible in tumbling mills without the aid of grinding media. Grinding mills in which comminution takes place without grinding aids are known as Autogenous Grinding (AG) mills or Fully Autogenous Grinding mills (FAG). These mills use large lumps of rock as the grinding media. Mills that use intermediate size rock or pebbles as a grinding medium are also autogenous mills but are known as pebble mills. Mills that grind hard ores with fracture characteristics that do not lend themselves to fully autogenous milling are charged with a small amount of steel balls to assist in the size reduction. These are known as Semi-autogenous Grinding (SAG) mills, hi the mining industry all of these types of mills are in use. The disintegration and size reduction of ores in AG/SAG mills is brought about by a combination of impact, attrition and abrasion forces during mill rotation. Particles at the toe of the mill charge receive the maximum impact forc...