SAM semi-autogenious and autogenious mills

Comminution in autogenous or semi-autogenous mills relies on the self-grinding action of the material. As the mill rotates, the feed material is lifted by the shell lining, and due to gravity, it falls down, resulting in material impact and breakage. This self-grinding process occurs in autogenous mills.

When ore properties are inadequate for autogenous grinding, the addition of steel grinding media compensates in semi-autogenous mills. The media replaces larger rocks, enabling impact breakage and achieving the desired comminution in a flexible and versatile manner.

AG/SAG mills are commonly characterized by a large mill diameter and short length, resulting in a high aspect ratio. This configuration offers benefits for achieving high throughput and coarser product fineness. The larger diameter generates the required breakage energy for efficient comminution. Following AG/SAG milling, the product is often passed on for further processing in ball mills to achieve the desired final particle size and product specifications. Typical length to diameter ratio of such AG/SAG mills is approx. 0,5.

In certain situations where a finer product is desired and a longer residence time in the mill is necessary, the ore can be processed in a single-stage AG/SAG mill. This is achieved by utilizing longer mills with a low aspect ratio. These mills have length to diameter ratios typically in the range of 1 or higher, often referred to as "square" mills.