8
that limits mill speed and power draw. An optimized
liner design is presented with a shallower lifter face
angle allowing a higher mill speed with new liners
increasing the breakage rates, thus, throughput is
increased [12].
Figure 11 provides an example of a mismatch
between liner design and performance objective.
The operating data shows the ramp up profile of the
installed bi-directional liner design with steep face
angles. The red line highlights the potential mill
speed ramp up profile to maximize power draw and
throughput. An example of bi- and unidirectional
liner designs are shown in Figure 12.
• Grate discharge and pumping capacity
Slurry pooling decreases throughput in two ways
due to a decrease in power draw associated with the
shift in center of mass and a decrease in energy trans-
ferred to the rock due to the cushioning effect of
the high slurry level [16]. Large-diameter SAG mills
equipped with a radial pulp lifter design are likely to
experience incomplete discharge and slurry backflow
into the mill. The backflow of slurry can accelerate
grate wear and increase the likelihood of slurry pool-
ing. The general strategy to increase flow through the
discharge system, described by Chandramohan et al
[3], is as follows:
– The mill speed dictates the flow rate through the
discharge grates and pumping chamber. Higher
mill speeds decrease the flow through the grates
due to a reduction in effective open area and
increases the flow through the pumping chamber.
To increase flow, decrease the SAG mill speed,
increase the slurry density and/or increase the mill
filling.
– Physical design changes to the discharge system
are required for highly constrained slurry flow.
Increasing the grate open area and converting from
radial to curved pulp lifters increases the slurry dis-
charge rate.
Figure 10. Current (left) and optimized (right) for
throughput lifter face angle [11]
Figure 11. Increased potential of a unidirectional liner design
that limits mill speed and power draw. An optimized
liner design is presented with a shallower lifter face
angle allowing a higher mill speed with new liners
increasing the breakage rates, thus, throughput is
increased [12].
Figure 11 provides an example of a mismatch
between liner design and performance objective.
The operating data shows the ramp up profile of the
installed bi-directional liner design with steep face
angles. The red line highlights the potential mill
speed ramp up profile to maximize power draw and
throughput. An example of bi- and unidirectional
liner designs are shown in Figure 12.
• Grate discharge and pumping capacity
Slurry pooling decreases throughput in two ways
due to a decrease in power draw associated with the
shift in center of mass and a decrease in energy trans-
ferred to the rock due to the cushioning effect of
the high slurry level [16]. Large-diameter SAG mills
equipped with a radial pulp lifter design are likely to
experience incomplete discharge and slurry backflow
into the mill. The backflow of slurry can accelerate
grate wear and increase the likelihood of slurry pool-
ing. The general strategy to increase flow through the
discharge system, described by Chandramohan et al
[3], is as follows:
– The mill speed dictates the flow rate through the
discharge grates and pumping chamber. Higher
mill speeds decrease the flow through the grates
due to a reduction in effective open area and
increases the flow through the pumping chamber.
To increase flow, decrease the SAG mill speed,
increase the slurry density and/or increase the mill
filling.
– Physical design changes to the discharge system
are required for highly constrained slurry flow.
Increasing the grate open area and converting from
radial to curved pulp lifters increases the slurry dis-
charge rate.
Figure 10. Current (left) and optimized (right) for
throughput lifter face angle [11]
Figure 11. Increased potential of a unidirectional liner design