XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2701
particles in the pulp phase, their role in recovering coarse
particles from the froth phase and their interactions at the
pulp-froth interface is not yet fully understood. Recently,
Jameson and Emer (2019) reported that certain bubble clus-
ters stuck beneath the froth phase, form a distinct layer of
bubble clusters below the froth. These clusters face difficul-
ties in rising within the froth. Consequently, this phenom-
enon adversely affects the recovery of coarse particles from
the froth phase, resulting in low froth recoveries Jameson
et al. (2020) suggested that the formation of a cluster layer
underneath the froth is likely due to insufficient buoyancy
possessed by the clusters, preventing their rise into the froth
phase, or the capacity of the froth to accommodate bub-
bles and particles is limited. However, it is still not clear
what the underlying mechanism is that impedes the move-
ment of these clusters into the froth phase, causing them to
remain stuck at the pulp-froth interface.
The objective of this study is to analyse the formation
of clusters beneath the froth phase and to investigate the
behaviour of bubble-particle clusters during the develop-
ment of the froth phase and its impact on the recovery of
coarse particles through the froth phase. The important
findings from this study are expected to lay the groundwork
for understanding the interactions between bubble-particle
clusters and the pulp-froth interface, as well as the transfer
of coarse particles from the pulp-froth interface to the cell
lip. These insights will ultimately contribute to improving
the recovery rate of coarse particles from the froth phase.
EXPERIMENTAL
Materials
Silica particles obtained from Boral Sands, NSW, Australia
were used for the experimentation. The particles were
cleaned using sodium hexa-metaphosphate to remove any
colloidal impurities attached to the silica. The detailed
procedure can be found in Bournival et al. (2015).
Dodecylamine (DDA) was used as a collector to enhance
the hydrophobicity of the particles and Methyl Isobutyl
Carbinol (MIBC) was used as a frother.
Flotation Tests and Froth Characteristic
Observation Tests
A column with 700 mm in height and 50 mm in diameter
was used. The experimental setup is illustrated in Figure 1.
Observations of froth characteristics and flotation tests
were conducted within this setup.
To observe the interaction of the bubble cluster at the
pulp-froth interface and the development of the froth phase,
four different experiments were conducted. The first experi-
ment was carried out in the absence of particles to observe
the development of the froth phase. The second experiment
was carried out using discrete coarse particles (–300 +100
µm). The third experiment was performed using fine par-
ticles (100 µm). The final experiment was carried out by
blending the coarse and fine particles in equal proportions.
Three flotation tests were conducted. The first test was
performed using –300+100 µm particles, and no froth phase
was allowed to form. Bubble clusters rising out of the pulp
overflowed as concentrate. In the second test, –300+100
µm particles were used again, but this time the froth phase
was allowed to build up. The distance from the cell lip to
the pulp level was set at 50 mm. For the third experiment,
a mixture of 50% of –100 µm and 50% of –300+100 µm
particles by weight was used. The froth depth, i.e., the dis-
tance from the cell lip to the pulp level was maintained at
approximately 150 mm. For each test, the flotation feed
(silica particles) of 100 gm was mixed with 1×10–5 M DDA
and conditioned for 5 minutes with a 35% w/w solid con-
centration. Subsequently, 20 ppm of MIBC was added
and conditioned for an additional 1 minute. The pulp was
Figure 1. Schematic of the experimental setup
particles in the pulp phase, their role in recovering coarse
particles from the froth phase and their interactions at the
pulp-froth interface is not yet fully understood. Recently,
Jameson and Emer (2019) reported that certain bubble clus-
ters stuck beneath the froth phase, form a distinct layer of
bubble clusters below the froth. These clusters face difficul-
ties in rising within the froth. Consequently, this phenom-
enon adversely affects the recovery of coarse particles from
the froth phase, resulting in low froth recoveries Jameson
et al. (2020) suggested that the formation of a cluster layer
underneath the froth is likely due to insufficient buoyancy
possessed by the clusters, preventing their rise into the froth
phase, or the capacity of the froth to accommodate bub-
bles and particles is limited. However, it is still not clear
what the underlying mechanism is that impedes the move-
ment of these clusters into the froth phase, causing them to
remain stuck at the pulp-froth interface.
The objective of this study is to analyse the formation
of clusters beneath the froth phase and to investigate the
behaviour of bubble-particle clusters during the develop-
ment of the froth phase and its impact on the recovery of
coarse particles through the froth phase. The important
findings from this study are expected to lay the groundwork
for understanding the interactions between bubble-particle
clusters and the pulp-froth interface, as well as the transfer
of coarse particles from the pulp-froth interface to the cell
lip. These insights will ultimately contribute to improving
the recovery rate of coarse particles from the froth phase.
EXPERIMENTAL
Materials
Silica particles obtained from Boral Sands, NSW, Australia
were used for the experimentation. The particles were
cleaned using sodium hexa-metaphosphate to remove any
colloidal impurities attached to the silica. The detailed
procedure can be found in Bournival et al. (2015).
Dodecylamine (DDA) was used as a collector to enhance
the hydrophobicity of the particles and Methyl Isobutyl
Carbinol (MIBC) was used as a frother.
Flotation Tests and Froth Characteristic
Observation Tests
A column with 700 mm in height and 50 mm in diameter
was used. The experimental setup is illustrated in Figure 1.
Observations of froth characteristics and flotation tests
were conducted within this setup.
To observe the interaction of the bubble cluster at the
pulp-froth interface and the development of the froth phase,
four different experiments were conducted. The first experi-
ment was carried out in the absence of particles to observe
the development of the froth phase. The second experiment
was carried out using discrete coarse particles (–300 +100
µm). The third experiment was performed using fine par-
ticles (100 µm). The final experiment was carried out by
blending the coarse and fine particles in equal proportions.
Three flotation tests were conducted. The first test was
performed using –300+100 µm particles, and no froth phase
was allowed to form. Bubble clusters rising out of the pulp
overflowed as concentrate. In the second test, –300+100
µm particles were used again, but this time the froth phase
was allowed to build up. The distance from the cell lip to
the pulp level was set at 50 mm. For the third experiment,
a mixture of 50% of –100 µm and 50% of –300+100 µm
particles by weight was used. The froth depth, i.e., the dis-
tance from the cell lip to the pulp level was maintained at
approximately 150 mm. For each test, the flotation feed
(silica particles) of 100 gm was mixed with 1×10–5 M DDA
and conditioned for 5 minutes with a 35% w/w solid con-
centration. Subsequently, 20 ppm of MIBC was added
and conditioned for an additional 1 minute. The pulp was
Figure 1. Schematic of the experimental setup