3772 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
size to 20 mm top-up size increased the shear power by
16%. The effect seems to be less in 0.3 m diameter mill,
where changing from 60 mm to 20 mm increased the shear
power by 6%. Figure 4 shows the power distribution data
from mills of the same aspect ratio (D/L). By comparing
data presented in Figure 3 and 4, it becomes evident that
the mill length has marginal effect on the distribution of
power between impact and shear events.
Figure 5 and 6 show the distribution of shear power
across different energy levels in a 1.8 m × 0.3 m and 0.6 m
× 0.3 m (D×L) mills. It is evident in Figure 5 and 6 that
reducing the ball top-up size shifted the collision energy
at which peak power occurs towards lower energy levels,
that is, the collision environment described by shear shifted
from being dominated by high-energy collisions to being
dominated by low-energy collisions. E.g., in a 1.8 m Ø
mill, the collision energy at which peak power occurs shifts
from 2×10–2 J to 5×10–4 J by changing from 60 mm top-
up size to 20 mm top-up size. This trend is evident on the
energy spectra from the other mills simulated.
Figure 6 shows that reducing ball top-up size results on
a notable increase on the peak power. E.g., the peak power
increases by 40% when the ball top-up size is changed from
60 mm to 20 mm. The increase in the peak power observed
is a result of a narrow spread of the effective energies dis-
sipated by smaller balls, as opposed to the wide spread of
the effective energies dissipated by large balls. The effect
appears to be reduced in larger mills. These observations
Figure 4. Effect of ball size on the distribution of collision power
Figure 5. Effect of ball size on energy spectra from the 1.8 m Ø mill
size to 20 mm top-up size increased the shear power by
16%. The effect seems to be less in 0.3 m diameter mill,
where changing from 60 mm to 20 mm increased the shear
power by 6%. Figure 4 shows the power distribution data
from mills of the same aspect ratio (D/L). By comparing
data presented in Figure 3 and 4, it becomes evident that
the mill length has marginal effect on the distribution of
power between impact and shear events.
Figure 5 and 6 show the distribution of shear power
across different energy levels in a 1.8 m × 0.3 m and 0.6 m
× 0.3 m (D×L) mills. It is evident in Figure 5 and 6 that
reducing the ball top-up size shifted the collision energy
at which peak power occurs towards lower energy levels,
that is, the collision environment described by shear shifted
from being dominated by high-energy collisions to being
dominated by low-energy collisions. E.g., in a 1.8 m Ø
mill, the collision energy at which peak power occurs shifts
from 2×10–2 J to 5×10–4 J by changing from 60 mm top-
up size to 20 mm top-up size. This trend is evident on the
energy spectra from the other mills simulated.
Figure 6 shows that reducing ball top-up size results on
a notable increase on the peak power. E.g., the peak power
increases by 40% when the ball top-up size is changed from
60 mm to 20 mm. The increase in the peak power observed
is a result of a narrow spread of the effective energies dis-
sipated by smaller balls, as opposed to the wide spread of
the effective energies dissipated by large balls. The effect
appears to be reduced in larger mills. These observations
Figure 4. Effect of ball size on the distribution of collision power
Figure 5. Effect of ball size on energy spectra from the 1.8 m Ø mill