XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3707
Grinding Media. The Red Chris concentrator from
Newmont in Canada consists of a SABC circuit followed
by flotation. The SAG and ball mill are both equipped
with dual pinion variable low-speed mill drives 2 × 5.25
MW installed power on the SAG mill and 2 × 6.7 MW on
the ball mill. The ball mill was overloaded with a too high
ball charge level, just in order to achieve maximum power
draw and significant potential energy savings possible by
lower mill speed were presented (Nadolski at al. 2019): “By
changing the size of make-up media, ball mill power draw was
estimated to reduce by approximately 21% through slowing
down of the mill (with the existing variable-frequency drive
[VFD]) while maintaining grind size.”
Fluctuating Power Draw. When a plant with fixed
speed ball mills is operating well and pushing tonnage at
or over the original design value, it can be challenging to
maintain a constant ball mill power draw at a high level.
This has different reasons, such as the status of the mill lin-
ers and lifters, challenges to maintain the correct ball mill
filling level, and fluctuating slurry densities. This can then
result into a wide variation of ball mill power draw (refer to
Figure 8), as was observed at Hudbay Minerals’ Constancia
Source: Mejia and Klein 2019
Figure 6. Fluctuating shoulder location as liners wear
Source: Mejia and Klein 2019
Figure 7. Ball mill operating work index increases with liner wear
Grinding Media. The Red Chris concentrator from
Newmont in Canada consists of a SABC circuit followed
by flotation. The SAG and ball mill are both equipped
with dual pinion variable low-speed mill drives 2 × 5.25
MW installed power on the SAG mill and 2 × 6.7 MW on
the ball mill. The ball mill was overloaded with a too high
ball charge level, just in order to achieve maximum power
draw and significant potential energy savings possible by
lower mill speed were presented (Nadolski at al. 2019): “By
changing the size of make-up media, ball mill power draw was
estimated to reduce by approximately 21% through slowing
down of the mill (with the existing variable-frequency drive
[VFD]) while maintaining grind size.”
Fluctuating Power Draw. When a plant with fixed
speed ball mills is operating well and pushing tonnage at
or over the original design value, it can be challenging to
maintain a constant ball mill power draw at a high level.
This has different reasons, such as the status of the mill lin-
ers and lifters, challenges to maintain the correct ball mill
filling level, and fluctuating slurry densities. This can then
result into a wide variation of ball mill power draw (refer to
Figure 8), as was observed at Hudbay Minerals’ Constancia
Source: Mejia and Klein 2019
Figure 6. Fluctuating shoulder location as liners wear
Source: Mejia and Klein 2019
Figure 7. Ball mill operating work index increases with liner wear