Grinding - Autogenous Mills
Autogenous Mills, How Do They Work?
Photo of Autogenous Mill at a copper mine. Autogenous Mills operate, mechanically, similar to the ball mill. They differ in the media they use to break or grind the ore. Autogenous Mills use large particles of ore instead of steel or other balls for grinding media. Autogenous mills use large pieces of ore as grinding media. The grinding is facilitated in autogenous mills by attrition with limited grinding by impact.
For an ore to successfully grind autogenously, the ore must be competent, and it must break along grain boundaries at the desired product size. Another requirement is that the finer sizes should break easily and should be removed from the mill, otherwise, there will be a critical size buildup. Autogenous grinding has two advantages, (1) it reduces metal wear and (2) eliminates secondary and tertiary crushing stages.
Thus it offers a savings in capital and operating costs. Autogenous mills are available for both wet and dry grinding. The diameter of autogenous mills is normally two to three times the length. The ore charge is usually 25 to 35% of the mill volume.Autogenous mills have grate discharges to retain the coarse grinding media in the mill.
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