Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small. The feed of the ball mill contains grinding balls.
Autogenous mills, or AG mills, can accomplish the same size reduction work as two or three stages of crushing and screening. Often used in grinding at modern mineral processing plants, AG mills reduce the material directly to the desired final size or prepare it for the following grinding stages.
Autogenous mill and semi autogenous mill View into a SAG mill for wet grinding Autogenous and semi autogenous mills have been used for over 20 years for the coarse grinding of diverse ores .
In a autogenous mill the ore is fed directly into the mill from either the primary crusher or the mine itself. The size of the rock will be between four and eight inches. It will be this type of mill that will use a stock pile instead of a bin as fine ore storage. The feed is large enough that moisture and freezing wont bother it.
Figures 3a amp; 3b give the power for an autogenous mill. Figures 4a and 4b are for the same size mill with a ball charge of 6% of mill volume . In the above example the power was calculated for a 30% volume. However, with the same sheets the power can be determined for any volumetric loading from 15% to 35%.
Autogenous mills can be operated in tandem with secondary grinding mills or they can be operated as single stage mills in closed circuit with a classification or sizing device. If a critical size builds up in the charge of the autogenous mill, it is usually extracted through pebble ports and crushed for recycle.
AG mill is a medium free mineral grinding equipment. The raw ore and the coarsely crushed ore are directly fed into the AG mill. No other medium is involved in grinding. Only the impact between the ore is used for self grinding.
Crusher product is typical feed to a ball mill using large diameter balls but not much grinding of 20 25 mm ore can be accomplished in an autogenous mill.
Wet autogenous grinding is the most important comminution development for mineral dressing purposes since the breakthrough of the ball mill. The fundamental mechanisms of the process are imperfectly known and research in this direction will certainly further the use of the method materially.