SAG mill ball charge determination and its influence on mill drive requirements

In semi-autogenous grinding (SAG), the grinding mill inventory, (i.e. volume of total charge, volume of ball charge, etc.) is important in determining the optimum operating condition for maximum production (tph), minimum specific energy (kwh/t) or lowest cost ($/t). A two-dimensional graphical method is presented for determining the actual ball charge within the total charge when parameters such as total volume, power draw and total mill charge weight are known. This information can then be used to develop a ball addition program to maintain optimum operating conditions, and to present to the mill operator a graphical description of the effect of the composition of the mill contents on the mill drive system and motor.<>