XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2873
including drag force, lift force, virtual mass force and tur-
bulent dispersion force were included to better simulate
phase interactions.
The simulation for each condition was run until reach-
ing an equilibrium at around 15 s. To ensure a fully equi-
librium stage, the results at 35 s of simulation were reported
in this study.
RESULT AND DISCUSSION
RFC Flotation Tests
Chalcopyrite flotation was first performed with the baseline
operating condition, indicated for test 1 in Table 1, opti-
mized for coal flotation in the RFC. The flotation results
were then compared to those obtained from coal flotation
with the same baseline condition, which were reported in
the previous study (Chen et al., 2023). In these two sets
of flotation, the only difference was chalcopyrite which
replaced coal at the same feed grade. Table 2 shows the
comparison.
From Table 2, it can be found that chalcopyrite flo-
tation produced a much higher gangue (quartz) recovery
at around 11.5% compared to 3.2% produced from coal
flotation. The increased gangue recovery in chalcopyrite
flotation indicated an increase in gangue entrainment. As
mentioned, the increased particle density increases the den-
sity of particle-bubble aggregates, which slows down the
rising velocity of these aggregates and increases the gas hold
up in flotation cells (Yianatos and Levy, 1989). In flota-
tion cells, the entrainment is caused by the rising motion
of bubbles, which create an upward drag on the surround-
ing liquid and solid to transport them to flotation concen-
trates. Hence, the increased gas hold up will lead to higher
entrainment.
To reduce gangue entrainment in chalcopyrite flota-
tion, chalcopyrite flotation was conducted at different
gas fluxes and wash water fluxes. The results are shown in
Table 3. The baseline flotation results were also included for
comparison.
The results from tests 1, 2 and 3 showed that as the
gas flux was reduced by 50% from the baseline, the gangue
recovery increased from 11.5% to 13.5%. In contrast, when
the gas flux was increased by 20% from the baseline, the
gangue recovery dropped to 10.5%. This is different from
the previous studies on coal flotation in the RFC showing
that reducing gas flux reduces the gangue entrainment by
lowering the number of bubbles transporting the entrained
particles (Dickinson et al., 2015). It is likely that the higher
density of chalcopyrite changed the air fraction and liquid
motion in the reverse fluidized bed and then the gangue
entrainment. This aspect was studied through the CFD
simulation in the following section. Meanwhile, different to
gangue recovery, chalcopyrite recovery increased as the gas
flux increased. This is in consistent with the previous obser-
vation in coal flotation. The increased gas flux provides a
greater surface area flux for the attachment of hydrophobic
particles (Jiang et al., 2019). With the increased chalcopy-
rite recovery and decreased gangue recovery at the highest
gas flux (test 3), chalcopyrite grade was increased to 21.2%,
about 10% higher than the baseline condition.
From tests 1, 4 and 5, it can be found that increas-
ing wash water flux decreased gangue recovery. As the
wash water flux was increased by 10% and 30% from the
baseline, the gangue recovery was reduced to 10.4% and
10.3%, respectively. This observation is consistent with the
observation in coal flotation. Increasing wash water flux
promotes the fluidization of the uprising bubble stream,
Table 1. Operating conditions tested in this study
Condition
Pulp Density
(wt%)
Gas Flux in
Downcomer
(cm/s)
Feed Flux in
Downcomer
(cm/s)
Wash Water flux
in Cell (mm/s)
Tailing
Discharge Rate
in Cell (mm/s)
1 (Baseline) 2 36.99 36.99 4.66 13.34
2 (Low gas) 2 18.50 36.99 4.66 13.34
3 (High gas) 2 44.39 36.99 4.66 13.34
4 (High wash water 1) 2 36.99 36.99 5.13 13.34
5 (High wash water 2) 2 36.99 36.99 6.06 13.34
6 (High gas and high wash water 1) 2 44.39 36.99 5.13 13.34
7 (High gas and high wash water 1) 2 44.39 36.99 6.06 13.34
Table 2. Coal and chalcopyrite flotation results with the
baseline condition optimized for coal flotation in the RFC
Test Sample
Gangue
Recovery (%)
Valuable
Recovery (%)
Valuable
Grade (%)
Coal 3.2 71.3 72.8
Chalcopyrite 11.5 87.0 11.1
including drag force, lift force, virtual mass force and tur-
bulent dispersion force were included to better simulate
phase interactions.
The simulation for each condition was run until reach-
ing an equilibrium at around 15 s. To ensure a fully equi-
librium stage, the results at 35 s of simulation were reported
in this study.
RESULT AND DISCUSSION
RFC Flotation Tests
Chalcopyrite flotation was first performed with the baseline
operating condition, indicated for test 1 in Table 1, opti-
mized for coal flotation in the RFC. The flotation results
were then compared to those obtained from coal flotation
with the same baseline condition, which were reported in
the previous study (Chen et al., 2023). In these two sets
of flotation, the only difference was chalcopyrite which
replaced coal at the same feed grade. Table 2 shows the
comparison.
From Table 2, it can be found that chalcopyrite flo-
tation produced a much higher gangue (quartz) recovery
at around 11.5% compared to 3.2% produced from coal
flotation. The increased gangue recovery in chalcopyrite
flotation indicated an increase in gangue entrainment. As
mentioned, the increased particle density increases the den-
sity of particle-bubble aggregates, which slows down the
rising velocity of these aggregates and increases the gas hold
up in flotation cells (Yianatos and Levy, 1989). In flota-
tion cells, the entrainment is caused by the rising motion
of bubbles, which create an upward drag on the surround-
ing liquid and solid to transport them to flotation concen-
trates. Hence, the increased gas hold up will lead to higher
entrainment.
To reduce gangue entrainment in chalcopyrite flota-
tion, chalcopyrite flotation was conducted at different
gas fluxes and wash water fluxes. The results are shown in
Table 3. The baseline flotation results were also included for
comparison.
The results from tests 1, 2 and 3 showed that as the
gas flux was reduced by 50% from the baseline, the gangue
recovery increased from 11.5% to 13.5%. In contrast, when
the gas flux was increased by 20% from the baseline, the
gangue recovery dropped to 10.5%. This is different from
the previous studies on coal flotation in the RFC showing
that reducing gas flux reduces the gangue entrainment by
lowering the number of bubbles transporting the entrained
particles (Dickinson et al., 2015). It is likely that the higher
density of chalcopyrite changed the air fraction and liquid
motion in the reverse fluidized bed and then the gangue
entrainment. This aspect was studied through the CFD
simulation in the following section. Meanwhile, different to
gangue recovery, chalcopyrite recovery increased as the gas
flux increased. This is in consistent with the previous obser-
vation in coal flotation. The increased gas flux provides a
greater surface area flux for the attachment of hydrophobic
particles (Jiang et al., 2019). With the increased chalcopy-
rite recovery and decreased gangue recovery at the highest
gas flux (test 3), chalcopyrite grade was increased to 21.2%,
about 10% higher than the baseline condition.
From tests 1, 4 and 5, it can be found that increas-
ing wash water flux decreased gangue recovery. As the
wash water flux was increased by 10% and 30% from the
baseline, the gangue recovery was reduced to 10.4% and
10.3%, respectively. This observation is consistent with the
observation in coal flotation. Increasing wash water flux
promotes the fluidization of the uprising bubble stream,
Table 1. Operating conditions tested in this study
Condition
Pulp Density
(wt%)
Gas Flux in
Downcomer
(cm/s)
Feed Flux in
Downcomer
(cm/s)
Wash Water flux
in Cell (mm/s)
Tailing
Discharge Rate
in Cell (mm/s)
1 (Baseline) 2 36.99 36.99 4.66 13.34
2 (Low gas) 2 18.50 36.99 4.66 13.34
3 (High gas) 2 44.39 36.99 4.66 13.34
4 (High wash water 1) 2 36.99 36.99 5.13 13.34
5 (High wash water 2) 2 36.99 36.99 6.06 13.34
6 (High gas and high wash water 1) 2 44.39 36.99 5.13 13.34
7 (High gas and high wash water 1) 2 44.39 36.99 6.06 13.34
Table 2. Coal and chalcopyrite flotation results with the
baseline condition optimized for coal flotation in the RFC
Test Sample
Gangue
Recovery (%)
Valuable
Recovery (%)
Valuable
Grade (%)
Coal 3.2 71.3 72.8
Chalcopyrite 11.5 87.0 11.1