Work out mill power requirement instantly with clear inputs, formula shown and shareable results.
Bond's law gives specific grinding energy as 10 x work index x (1/sqrt(P80) - 1/sqrt(F80)) in kilowatt-hours per tonne, with sizes in microns. Multiplying by throughput gives mill power. Comminution typically consumes 30-50% of a concentrator's total energy, so the work index and target grind size dominate operating cost.
Bond's law
W (kWh/t) = 10 x Wi x (1/sqrt(P80) - 1/sqrt(F80))
Mill power
Power (kW) = specific energy x throughput (t/h)
Energy scales with the inverse square root of product size, so halving P80 raises specific energy by about 41%. Grinding only as fine as liberation requires is a major cost lever.
It works well for conventional ball milling in the 100 micron to 10 mm range. Very fine grinding follows a different exponent, and SAG milling needs its own testwork and models.