EFFECT OF FLUID MEDIUM DENSITY ON BALL MILL TORQUE, ENERGY-DISTRIBUTION AND GRINDING KINETICS

Dolomite was ground in a batch ball mill filled completely with fluids having densities ranging from nearly zero to almost 3000 kg/m**3. The measured power draft was in good agreement with the torque-arm model for tumbling mills, modified to account for buoyancy effects on the grinding charge. The results show that in the case of three liquid fluids the grinding path remains invariant even though the energy input is throttled significantly with increase in fluid density. Extrapolation to a hypothetical fluid of density equal to that of the grinding charge permits an approximate breakdown of the energy consumption pattern in the mill. There is a threshold power level below which hardly any grinding takes place. It further appears that the overall rate of grinding is a linear function of mill power rather than directly proportional to power.