### Evaluation of dry grinding using HPGR in closed circuit ...

The specific grinding energy of a 2.44 m interior diameter wet overflow ball mill is usually calculated using the Bond work index and Bond's third law equation : (3) W = 10 W i (P 80-0.5-F 80-0.5) where F 80 is the 80% passing size of the feed (μm), P 80 is the 80% passing size of the product (μm), W is the specific grinding energy (kW h/t ...