Grindiability & Mill Shaft Power

(1)What is the relation between Bond Work Index &  Mill shaft power ?

For Ball Mill

For VRM shaft power

For Roller Press Shaft Power

What is the relation between Grindiability(KWh/t) of material with shaft power

for BM,RP,VRM in separate.

How can I calculate grindiability if I use to ball mills in series where part of the coarse of separator goes to small mill while the fresh feed with part of sep. coarse goes to big mill.

Close ckt with common separator

(2)IF Bond Index is 15.5 what will be the shaft power of ball mill & grindiability

raj