XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 625
Coarse Particle Comminution and Size Classification
There are a few coarse comminution options to replace ball
milling including coarse stirred mills and the HPGR (Paz
et al., 2023 Gagnon et al., 2023). A recent study to replace
ball mills with the HPGR showed energy savings of 62%
for the HPGR and a 54% savings when comparing the
ball mill and HPGR circuits (MacIver et al 2023). Swiss
Tower Mill Minerals developed coarse stirred mill which
was adapted from their fine/ultrafine grinding application
(Erb et al., 2015). These vertical stirred mills are currently
capable of processing mill feed top size of 4 mm, which
is suitable to process HPGR close circuit product with a
screen aperture size of 4 mm (Vijfeijken et al., 2023). For
the purpose of this study, coarse stirred mill grinding is
selected with consideration of simplifying size classification
and water recovery. HPGR product reports to hydrocy-
clones to remove fines ahead of coarse particle stirred mill-
ing. The stirred mill is operated in open circuit and the
product is combined with the cyclone overflow, which then
feeds to the coarse particle flotation circuit.
Coarse Particle Flotation—Coarse Waste Rejection
Recent advances in coarse particle flotation create oppor-
tunities for early-stage waste rejection at a relatively coarse
grind size and a reduction in comminution energy it
also allows easy recycling of water within the process. A
range of technologies have been developed including the
Hydrofloat, NovaCell, Reflux Flotation Cell, and CoarseAir
Flotation Cell (Anzoom et al., 2024). Newcrest’s Cadia
Mine installed the Hydrofloat to recover coarse middling
particles that report to fine comminution and final clean-
ing stages of flotation followed by thickening and filtration.
The mass pull assumption for the Hydrofloat operation
in the future flowsheet is estimated upon the relationship
between upgrade ratio and mass pull (Arburo et al., 2022).
Dewatering Coarse Flotation Tailings
Coarse particle flotation rejects a tailings stream that is
diverted away from fine grinding and thereby reduces
energy consumption. The coarse tailings can also be dewa-
tered using technologies such as dewatering screens and
screw classifiers such that recovered water can be recycled
and re-used. A test program conducted on a BC copper ore
showed that high frequency dewatering screens (Derrick
screen) can reduce water contents to about 12.5% and that
screw classifiers designed for water recovery can reduce
water contents to as low as 8% (Saud, 2021). The water,
still containing some fine particles, reports to the hydrocy-
clone ahead of coarse grinding. The coarse particle flotation
concentrate then reports to the regrind stirred mill circuit.
The coarse particle flotation tailings sand, with a P80 of
~2mm, can be utilized for tailings dam construction, used
for other construction projects, or co-disposed with the
dewatered fine tailings.
Regrind Stirred Milling
Coarse particle flotation concentrate is combined with
the primary hydrocyclone fines and sent to a secondary
hydrocyclone circuit ahead of regrind stirred mill grinding.
Either vertical or horizontal stirred mills are operated in
open circuit to liberate the copper minerals ahead of cleaner
flotation. The quantity of material reporting to rougher
flotation feed was reduced by rejection of materials dur-
ing BOS, and Particle Sorting. However, the coarse par-
ticle flotation mass yield is higher to ensure copper recovery
is maintained. Although fluidized stirred media mills are
considered more energy-efficient than conventional ball
mills, leading to additional savings in specific energy con-
sumption, the overall installed and operating power for the
regrind circuit in the future flowsheet is still higher than
that of conventional regrind circuits. This is attributed
to the higher regrind mass throughput rate due to higher
rougher mass pull and increased grindability due to pres-
ence of harder and competent copper-bearing particles.
This higher regrind power requirement is more than offset
by the reduced primary grinding requirements.
Fine Particle Flotation
Conventional fine particle flotation is conducted with
mechanical and column flotation cells creating a final con-
centrate and a fine particle tailings stream. Advances in flo-
tation technologies claim to increase flotation selectivity and
recovery as well as reduce energy usage. Examples of high
intensity flotation technologies including Staged Flotation
Reactors (SFR), Direct Flotation Reactors (DFR), Jameson
cells, and Stack Cells (Araya, 2024). For the purpose of this
study, no significant differentiation with respect to water
usage and energy was considered.
Tailings Thickening and Filtration
To increase the recovery and recycling of process water, the
fine tailings are thickened, and pressure filtered reducing
the water content to less than 15%. The dewatered tailings
are transported to a storage facility. An additional benefit
is that the dewatered tailings are physically stable reducing
the risks associated with tailings dam failures. Studies have
shown that the specific energy consumption for the tail-
ings filtration process is in the order of 0.1–2.0 kWh/t, but
this can vary widely based on factors such as the moisture
content of the tailings, the filtration method (e.g., pressure
Coarse Particle Comminution and Size Classification
There are a few coarse comminution options to replace ball
milling including coarse stirred mills and the HPGR (Paz
et al., 2023 Gagnon et al., 2023). A recent study to replace
ball mills with the HPGR showed energy savings of 62%
for the HPGR and a 54% savings when comparing the
ball mill and HPGR circuits (MacIver et al 2023). Swiss
Tower Mill Minerals developed coarse stirred mill which
was adapted from their fine/ultrafine grinding application
(Erb et al., 2015). These vertical stirred mills are currently
capable of processing mill feed top size of 4 mm, which
is suitable to process HPGR close circuit product with a
screen aperture size of 4 mm (Vijfeijken et al., 2023). For
the purpose of this study, coarse stirred mill grinding is
selected with consideration of simplifying size classification
and water recovery. HPGR product reports to hydrocy-
clones to remove fines ahead of coarse particle stirred mill-
ing. The stirred mill is operated in open circuit and the
product is combined with the cyclone overflow, which then
feeds to the coarse particle flotation circuit.
Coarse Particle Flotation—Coarse Waste Rejection
Recent advances in coarse particle flotation create oppor-
tunities for early-stage waste rejection at a relatively coarse
grind size and a reduction in comminution energy it
also allows easy recycling of water within the process. A
range of technologies have been developed including the
Hydrofloat, NovaCell, Reflux Flotation Cell, and CoarseAir
Flotation Cell (Anzoom et al., 2024). Newcrest’s Cadia
Mine installed the Hydrofloat to recover coarse middling
particles that report to fine comminution and final clean-
ing stages of flotation followed by thickening and filtration.
The mass pull assumption for the Hydrofloat operation
in the future flowsheet is estimated upon the relationship
between upgrade ratio and mass pull (Arburo et al., 2022).
Dewatering Coarse Flotation Tailings
Coarse particle flotation rejects a tailings stream that is
diverted away from fine grinding and thereby reduces
energy consumption. The coarse tailings can also be dewa-
tered using technologies such as dewatering screens and
screw classifiers such that recovered water can be recycled
and re-used. A test program conducted on a BC copper ore
showed that high frequency dewatering screens (Derrick
screen) can reduce water contents to about 12.5% and that
screw classifiers designed for water recovery can reduce
water contents to as low as 8% (Saud, 2021). The water,
still containing some fine particles, reports to the hydrocy-
clone ahead of coarse grinding. The coarse particle flotation
concentrate then reports to the regrind stirred mill circuit.
The coarse particle flotation tailings sand, with a P80 of
~2mm, can be utilized for tailings dam construction, used
for other construction projects, or co-disposed with the
dewatered fine tailings.
Regrind Stirred Milling
Coarse particle flotation concentrate is combined with
the primary hydrocyclone fines and sent to a secondary
hydrocyclone circuit ahead of regrind stirred mill grinding.
Either vertical or horizontal stirred mills are operated in
open circuit to liberate the copper minerals ahead of cleaner
flotation. The quantity of material reporting to rougher
flotation feed was reduced by rejection of materials dur-
ing BOS, and Particle Sorting. However, the coarse par-
ticle flotation mass yield is higher to ensure copper recovery
is maintained. Although fluidized stirred media mills are
considered more energy-efficient than conventional ball
mills, leading to additional savings in specific energy con-
sumption, the overall installed and operating power for the
regrind circuit in the future flowsheet is still higher than
that of conventional regrind circuits. This is attributed
to the higher regrind mass throughput rate due to higher
rougher mass pull and increased grindability due to pres-
ence of harder and competent copper-bearing particles.
This higher regrind power requirement is more than offset
by the reduced primary grinding requirements.
Fine Particle Flotation
Conventional fine particle flotation is conducted with
mechanical and column flotation cells creating a final con-
centrate and a fine particle tailings stream. Advances in flo-
tation technologies claim to increase flotation selectivity and
recovery as well as reduce energy usage. Examples of high
intensity flotation technologies including Staged Flotation
Reactors (SFR), Direct Flotation Reactors (DFR), Jameson
cells, and Stack Cells (Araya, 2024). For the purpose of this
study, no significant differentiation with respect to water
usage and energy was considered.
Tailings Thickening and Filtration
To increase the recovery and recycling of process water, the
fine tailings are thickened, and pressure filtered reducing
the water content to less than 15%. The dewatered tailings
are transported to a storage facility. An additional benefit
is that the dewatered tailings are physically stable reducing
the risks associated with tailings dam failures. Studies have
shown that the specific energy consumption for the tail-
ings filtration process is in the order of 0.1–2.0 kWh/t, but
this can vary widely based on factors such as the moisture
content of the tailings, the filtration method (e.g., pressure