1526 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
that passes through the wheels. The crushed rocks are then
sieved to obtain the percentage of fragments passing 1/10th
of the original particle size, the t10. These results together
with the measured energies are used in a fit to determine
the ore’s inherent breakage parameters, denoted as A and b
(Napier-Munn et al. 1996) shown in Equation 1.
t A^1 e
10 =--bEcs h (1)
Equipment Description
The principle of the method is illustrated in Figure 2, the
energy consumption per particle breakage event in the
Geopyörä test is determined through the momentum loss
from the pair of crushing wheels (Torvela, 2020). Once the
rock is released from the feed, the direct-drive system disen-
gages, allowing the wheels to idle. This makes the decelera-
tion of the wheels happen from interactions with the rock,
providing a direct measurement of the energy expended to
perform the actions of compression and fracture. To ensure
accuracy, losses due to mechanical friction, back electromo-
tive force (EMF), and similar machine-specific factors are
meticulously calibrated for each machine and factored into
the energy calculation to assure precise results (Bueno et
al. 2021).
Also shown in Figure 2 is the measurement of the force
by the Geopyörä, obtained by a loadcell that provides a
high sampling frequency of 5 kHz. When the force mea-
sured by the load cell in the event of a rock breakage hits
a determined threshold (Ft), the recording of force will
commence for a specific time duration (t1-t0) and the high-
est force peak within this timeframe (Fp) will be registered
by the device for that particle.
The standard testing procedure utilizes one narrow
rock size selected from lightly crushed drill core. Two dis-
tinct ranges of crushing energy are achieved by using two
different gaps between the crushing wheels. The measured
energy and breakage force for each particle provides a dis-
tribution of breakage energies for the 20 to 30 particles that
are tested. The progeny of each set of tests are sized on a
truncated set of screens, to provide the t10 value and per-
cent passing 150 µm. More detailed description of the test-
ing method is provided in [Bueno et al. 2021].
DEVELOPMENT
Database
The database is composed of 254 samples from nine dif-
ferent mineral deposits around the world tested with
Geopyörä, in addition to representative subsamples tested
on the SMC test, in a way that is possible to correlate
Geopyörä results with the industry standards, as well as
to adjust a constant factor to go from the Geopyörä Index
(GPI) to the Drop Weight Index (DWI). To ensure the
quality of the sample separation it is possible to demon-
strate the representativeness of the selection by comparing
the Specific Gravity (SG) results from both tests, as shown
by the parity plot in Figure 3.
Figure 1. Geopyörä breakage device
that passes through the wheels. The crushed rocks are then
sieved to obtain the percentage of fragments passing 1/10th
of the original particle size, the t10. These results together
with the measured energies are used in a fit to determine
the ore’s inherent breakage parameters, denoted as A and b
(Napier-Munn et al. 1996) shown in Equation 1.
t A^1 e
10 =--bEcs h (1)
Equipment Description
The principle of the method is illustrated in Figure 2, the
energy consumption per particle breakage event in the
Geopyörä test is determined through the momentum loss
from the pair of crushing wheels (Torvela, 2020). Once the
rock is released from the feed, the direct-drive system disen-
gages, allowing the wheels to idle. This makes the decelera-
tion of the wheels happen from interactions with the rock,
providing a direct measurement of the energy expended to
perform the actions of compression and fracture. To ensure
accuracy, losses due to mechanical friction, back electromo-
tive force (EMF), and similar machine-specific factors are
meticulously calibrated for each machine and factored into
the energy calculation to assure precise results (Bueno et
al. 2021).
Also shown in Figure 2 is the measurement of the force
by the Geopyörä, obtained by a loadcell that provides a
high sampling frequency of 5 kHz. When the force mea-
sured by the load cell in the event of a rock breakage hits
a determined threshold (Ft), the recording of force will
commence for a specific time duration (t1-t0) and the high-
est force peak within this timeframe (Fp) will be registered
by the device for that particle.
The standard testing procedure utilizes one narrow
rock size selected from lightly crushed drill core. Two dis-
tinct ranges of crushing energy are achieved by using two
different gaps between the crushing wheels. The measured
energy and breakage force for each particle provides a dis-
tribution of breakage energies for the 20 to 30 particles that
are tested. The progeny of each set of tests are sized on a
truncated set of screens, to provide the t10 value and per-
cent passing 150 µm. More detailed description of the test-
ing method is provided in [Bueno et al. 2021].
DEVELOPMENT
Database
The database is composed of 254 samples from nine dif-
ferent mineral deposits around the world tested with
Geopyörä, in addition to representative subsamples tested
on the SMC test, in a way that is possible to correlate
Geopyörä results with the industry standards, as well as
to adjust a constant factor to go from the Geopyörä Index
(GPI) to the Drop Weight Index (DWI). To ensure the
quality of the sample separation it is possible to demon-
strate the representativeness of the selection by comparing
the Specific Gravity (SG) results from both tests, as shown
by the parity plot in Figure 3.
Figure 1. Geopyörä breakage device