Design and Motor Rating Calculations for Ball Mill

In continuation to our earlier post on Efficient grinding system for Bauxite in Alumina refinery, we will discuss the methodology along with design calculations for sizing of Ball mill including the estimated motor rating with reference to a known mill operative in identical process conditions.The cross section of a typical Ball mill has been shown below just to have the physical feel of the main components of Ball mill and movement of grinding media inside in running condition. I am thankful to my friend who has developed this animation for schematic cross section of the ball mill in operation

Schematic Cross section of Ball mill in Operation

It is evident from the above schematic diagram that size reduction of bauxite takes place due to impact action of balls and rubbing action of particles as well. The actual operating rotational speed of ball mill is controlled at around 65 to 80% of the critical speed of the mill derived on the basis of effective diameter of the mill as elaborated below. We have already discussed about the material of construction for ball mill liner and balls used as grinding media. We are presenting here the systematic approach to work out the dimensions (Diameter and Length) and motor rating of ball mill for successful operation for a typical capacity Alumina refinery as given below

The above mathematical model has been developed by the author based the personal experience and expertise acquired in the field of Bauxite and Alumina. All out efforts have been put to present the calculations in simplified manner for easy understanding by one and all related to the subject. Hope, you will appreciate our attempts in preparing the concise and systematic derivations for such a complicated topic. Please put your views / remarks / suggestions / comments, if any, for further improvement.