Autogenous Grinding

a grinding process in which large pieces of the material to be ground—ores and rocks-serve as the grinding medium; the process is carried out in drum mills.

In autogenous grinding, a distinction is made between ore and ore-pebble grinding. Ore grinding is carried out in mills with a large diameter (up to 12 m) and short length (the ratio of diameter to length is approximately 3). Ore with pieces having dimensions up to 300 mm (sometimes, up to 600 mm) is loaded into the mill. If only a small amount of the large fraction is present in the ore, steel balls are added to the mill. In ore-pebble grinding, the ore pebble serves as the grinding medium. In dry autogenous grinding, air is blown continuously through the mill, thus removing the fine material. In wet autogenous grinding, the pulp is removed through a screen.

In comparison to grinding with steel rods or balls, autogenous grinding has the following advantages: (1) the crushing of the ore before milling is simplified and made less expensive, (2) the expenditure of steel rods or balls is eliminated or reduced, and (3) the technological efficiency for the concentration of some ores is improved as a result of less overgrinding of a valuable mineral. However, the output of a unit volume for autogenous mills is lower, and the energy expenditure for crushing and grinding one ton of ore is higher. In the USSR, autogenous grinding is used in the concentration of gold, diamond, and iron ores.