XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3779
This included, modern and highly detailed finite element
analysis for rotating structures advanced system analysis of
the combined mill, ring motor, foundation, and soil sys-
tem coupled smooth particle hydrodynamics and discrete
element method evaluation of discharge capacity, and state-
of-the-art bearing technology.
WHY EVEN LARGER MILLS
Large mines need large grinding mills to capture the econo-
mies of scale that make ever declining head grades profitable
by running at increasingly higher throughput rates. The
existing well proven grinding mill systems can be divided
into two main categories: ring geared mills with RMD and
gearless mills with GMD.
• The current generation of 40 ft diameter SAG mills
with GMDs ranging from 20 to 28 MW are generally
suitable for single-line throughput in the range of 65
to 90 kt/d for typical copper porphyry deposits.
• The current generation of 38 ft diameter SAG mills
with either GMDs of 20 MW and more or RMDs
using twin up to 9 MW drives are generally suitable
for single-line throughput in the range of 40 to 55
kt/d for typical copper porphyry deposits.
There are many low-grade and high tonnage deposits that
are waiting for the next generation of grinding mills to arrive
in order to achieve the economies of scale necessary to mine
and process these deposits economically. An example large
copper porphyry project treating 120,000 tons per day of
feed can choose between a single line of GMD driven mills
or two lines of RMD driven mills.
Figure 1 demonstrates the throughput of a 44 ft SAG
and a 32 ft ball mill circuit processing the median “2008”
ore hardness published in Gaunt et al., 2014. A single line
Figure 1. One line with GMDs
This included, modern and highly detailed finite element
analysis for rotating structures advanced system analysis of
the combined mill, ring motor, foundation, and soil sys-
tem coupled smooth particle hydrodynamics and discrete
element method evaluation of discharge capacity, and state-
of-the-art bearing technology.
WHY EVEN LARGER MILLS
Large mines need large grinding mills to capture the econo-
mies of scale that make ever declining head grades profitable
by running at increasingly higher throughput rates. The
existing well proven grinding mill systems can be divided
into two main categories: ring geared mills with RMD and
gearless mills with GMD.
• The current generation of 40 ft diameter SAG mills
with GMDs ranging from 20 to 28 MW are generally
suitable for single-line throughput in the range of 65
to 90 kt/d for typical copper porphyry deposits.
• The current generation of 38 ft diameter SAG mills
with either GMDs of 20 MW and more or RMDs
using twin up to 9 MW drives are generally suitable
for single-line throughput in the range of 40 to 55
kt/d for typical copper porphyry deposits.
There are many low-grade and high tonnage deposits that
are waiting for the next generation of grinding mills to arrive
in order to achieve the economies of scale necessary to mine
and process these deposits economically. An example large
copper porphyry project treating 120,000 tons per day of
feed can choose between a single line of GMD driven mills
or two lines of RMD driven mills.
Figure 1 demonstrates the throughput of a 44 ft SAG
and a 32 ft ball mill circuit processing the median “2008”
ore hardness published in Gaunt et al., 2014. A single line
Figure 1. One line with GMDs