3742 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Effect of Operating Variable on Product Blaine
Figure 7 shows that the products of grate discharge give
about 20% more Blaine units than overflow discharge.
Increasing the tonnage leads to decrease the Blaine as the
products become coarser. Also, it was observed that the per-
cent solids has a small effect on Blane.
Effect of Specific Energy on Product Blaine and
Product Size
Despite the increasing of the power when using the grate
discharge, the Blaine increases by about 6% for the same
specific energy compared to the overflow. However, com-
paring the product size, P80, it seems that overflow discharge
gives finer product compared to grate discharge product.
An optimization of the ball charge for the grate discharge
cases could improve the energy consumption (Figure 8).
CONCLUSIONS
It can be concluded that:
1. Compared to an overflow (high slurry level operat-
ing) ball mill, the experts have stated, and many
plant tests have shown, that a grate discharge (low
slurry level) ball mill draws significantly (10–20%)
more power per ton of grinding balls.
2. A grate discharge provides ball mill/circuit effi-
ciency at least equal to, but normally greater than,
an overflow ball mill.
3. There was no clear evidence found that shows a
decrease in overgrinding with grate vs. overflow
discharge.
4. The efficiency benefit of a grate discharge is small
for pilot test mills compared to the benefit often
seen in larger plant mills.
Figure 6. Effect of operating variables on product size (P80)
Figure 7. Effect of operating variables on Blaine
Effect of Operating Variable on Product Blaine
Figure 7 shows that the products of grate discharge give
about 20% more Blaine units than overflow discharge.
Increasing the tonnage leads to decrease the Blaine as the
products become coarser. Also, it was observed that the per-
cent solids has a small effect on Blane.
Effect of Specific Energy on Product Blaine and
Product Size
Despite the increasing of the power when using the grate
discharge, the Blaine increases by about 6% for the same
specific energy compared to the overflow. However, com-
paring the product size, P80, it seems that overflow discharge
gives finer product compared to grate discharge product.
An optimization of the ball charge for the grate discharge
cases could improve the energy consumption (Figure 8).
CONCLUSIONS
It can be concluded that:
1. Compared to an overflow (high slurry level operat-
ing) ball mill, the experts have stated, and many
plant tests have shown, that a grate discharge (low
slurry level) ball mill draws significantly (10–20%)
more power per ton of grinding balls.
2. A grate discharge provides ball mill/circuit effi-
ciency at least equal to, but normally greater than,
an overflow ball mill.
3. There was no clear evidence found that shows a
decrease in overgrinding with grate vs. overflow
discharge.
4. The efficiency benefit of a grate discharge is small
for pilot test mills compared to the benefit often
seen in larger plant mills.
Figure 6. Effect of operating variables on product size (P80)
Figure 7. Effect of operating variables on Blaine