XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2793
Whether or not added NPs can improve coarse particle
recovery remains an open question. However, the results
presented in this study suggest that ultrafine particles
can, under certain conditions, reduce the total amount of
particles that a single bubble can transport into the froth
phase. However, taking into account the residence time of
the bubbles in an industrial flotation cell, it is possible that
the amount of particles attached to a single bubble never
reaches the maximum value, which means that this mecha-
nism does not affect the overall yield.
CONCLUSIONS
The presence of NPs at the interface strongly influenced
the distribution of GBs on a bubble surface. A gap/void
forms between the GBs, which reduces their packing den-
sity. The effect is more pronounced for pre-compressed
bubbles, where the dense NP layer on the bubble surface
almost completely prevents the attachment of the GBs. It
is observed that the addition of NPs significantly increases
the attachment rate of GBs, both by decreasing their pack-
ing density and by increasing their attachment probability.
REFERENCES
S. Farrokhpay, L. Filippov, and D. Fornasiero, “Flotation
of Fine Particles: A Review,” Mineral Processing
and Extractive Metallurgy Review, vol. 42, no.
7, pp. 473–483, 2021, ISSN: 15477401. doi:
10.1080/08827508.2020.1793140.
Z. Aktas, J. Cilliers, and A. Banford, “Dynamic Froth
Stability: Particle Size, Airflow Rate and Conditioning
Time Effects,” International Journal of Mineral
Processing, vol. 87, no. 1, pp. 65–71, 2008, ISSN:
0301-7516. doi: 10.1016/j.minpro.2008.02.001.
J. Pease, D. Curry, and M. Young, “Designing Flotation
Circuits for High Fines Recovery,” Minerals Engineering,
vol. 19, no. 6, pp. 831–840, 2006, Selected papers
from the Centenary of Flotation Symposium, 5–9
June 2005, Brisbane, Australia, ISSN: 0892-6875. doi:
10.1016/j.mineng.2005.09.056.
N. Barbian, E. Ventura-Medina, and J. Cilliers, “Mineral
Attachment and Bubble Bursting in Flotation Froths,”
in Proceedings of Centenary of Flotation Symposium,
Brisbane, Australia, 2005.
T. S. Horozov, “Foams and Foam Films Stabilised by Solid
Particles,” Current Opinion in Colloid and Interface
Science, vol. 13, no. 3, pp. 134–140, 2008, ISSN:
13590294. doi: 10.1016/j.cocis.2007.11.009.
E. S. Basheva, P. A. Kralchevsky, K. D. Danov, K. P.
Ananthapadmanabhan, and A. Lips, “The Colloid
Structural Forces as a Tool for Particle Characterization
and Control of Dispersion Stability,” Physical Chemistry
Chemical Physics, vol. 9, no. 38, pp. 5183–5198, 2007.
E. Dickinson, “Food Emulsions and Foams: Stabilization
by Particles,” Current Opinion in Colloid &Interface
Science, vol. 15, no. 1, pp. 40–49, 2010, ISSN: 1359-
0294. doi: 10.1016/j.cocis.2009.11.001.
S. Yang, R. Pelton, A. Raegen, M. Montgomery, and K.
Dalnoki-Veress, “Nanoparticle Flotation Collectors:
Mechanisms Behind a New Technology,” Langmuir,
vol. 27, no. 17, pp. 10438–10446, 2011, ISSN:
07437463. doi: 10.1021/la2016534.
S. Ata, “Coalescence of Bubbles Covered by Particles,”
Langmuir, vol. 24, no. 12, pp. 6085–6091, 2008,
ISSN: 07437463. doi: 10.1021/la800466x.
B. Albijanic, O. Ozdemir, A. V. Nguyen, and D. Bradshaw,
“A Review of Induction and Attachment Times of
Wetting Thin Films Between Air Bubbles and Particles
and Its Relevance in the Separation of Particles by
Flotation,” Advances in Colloid and Interface Science,
vol. 159, no. 1, pp. 1–21, 2010, ISSN: 00018686. doi:
10.1016/j.cis.2010.04.003.
A. V. Nguyen, D.-A. An-Vo, T. Tran-Cong, and G. M.
Evans, “A Review of Stochastic Description of the
Turbulence Effect on Bubble-Particle Interactions in
Flotation,” International Journal of Mineral Processing,
vol. 156, pp. 75–86, 2016, In Honor of Professor
Heinrich Schubert on his 90th birthday, ISSN: 0301-
7516. doi: 10.1016/j.minpro.2016.05.002.
M. Eftekhari, K. Schwarzenberger, A. Javadi, and K.
Eckert, “The Influence of Negatively Charged Silica
Nanoparticles on the Surface Properties of Anionic
Surfactants: Electrostatic Repulsion or the Effect of
Ionic Strength?” Physical Chemistry Chemical Physics,
vol. 22, no. 4, pp. 2238–2248, 2020.
M. Eftekhari, K. Schwarzenberger, P. Schlereth, and K.
Eckert, “Dynamics of Particle Attachment in a Model
Stirred Cell: A New Technique to Characterize and
Quantify Particle Floatability,” Minerals Engineering,
vol. 210, p. 108643, 2024, ISSN: 0892-6875. doi:
10.1016/j.mineng.2024.108643.
M. Eftekhari, K. Schwarzenberger, S. I. Karakashev, N. A.
Grozev, and K. Eckert, “Oppositely Charged Surfactants
and Nanoparticles at the Air-Water Interface: Influence
of Surfactant to Nanoparticle Ratio,” Journal of Colloid
and Interface Science, vol. 653, pp. 1388–1401, 2024.

Previous Page Next Page

Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2793
Whether or not added NPs can improve coarse particle
recovery remains an open question. However, the results
presented in this study suggest that ultrafine particles
can, under certain conditions, reduce the total amount of
particles that a single bubble can transport into the froth
phase. However, taking into account the residence time of
the bubbles in an industrial flotation cell, it is possible that
the amount of particles attached to a single bubble never
reaches the maximum value, which means that this mecha-
nism does not affect the overall yield.
CONCLUSIONS
The presence of NPs at the interface strongly influenced
the distribution of GBs on a bubble surface. A gap/void
forms between the GBs, which reduces their packing den-
sity. The effect is more pronounced for pre-compressed
bubbles, where the dense NP layer on the bubble surface
almost completely prevents the attachment of the GBs. It
is observed that the addition of NPs significantly increases
the attachment rate of GBs, both by decreasing their pack-
ing density and by increasing their attachment probability.
REFERENCES
S. Farrokhpay, L. Filippov, and D. Fornasiero, “Flotation
of Fine Particles: A Review,” Mineral Processing
and Extractive Metallurgy Review, vol. 42, no.
7, pp. 473–483, 2021, ISSN: 15477401. doi:
10.1080/08827508.2020.1793140.
Z. Aktas, J. Cilliers, and A. Banford, “Dynamic Froth
Stability: Particle Size, Airflow Rate and Conditioning
Time Effects,” International Journal of Mineral
Processing, vol. 87, no. 1, pp. 65–71, 2008, ISSN:
0301-7516. doi: 10.1016/j.minpro.2008.02.001.
J. Pease, D. Curry, and M. Young, “Designing Flotation
Circuits for High Fines Recovery,” Minerals Engineering,
vol. 19, no. 6, pp. 831–840, 2006, Selected papers
from the Centenary of Flotation Symposium, 5–9
June 2005, Brisbane, Australia, ISSN: 0892-6875. doi:
10.1016/j.mineng.2005.09.056.
N. Barbian, E. Ventura-Medina, and J. Cilliers, “Mineral
Attachment and Bubble Bursting in Flotation Froths,”
in Proceedings of Centenary of Flotation Symposium,
Brisbane, Australia, 2005.
T. S. Horozov, “Foams and Foam Films Stabilised by Solid
Particles,” Current Opinion in Colloid and Interface
Science, vol. 13, no. 3, pp. 134–140, 2008, ISSN:
13590294. doi: 10.1016/j.cocis.2007.11.009.
E. S. Basheva, P. A. Kralchevsky, K. D. Danov, K. P.
Ananthapadmanabhan, and A. Lips, “The Colloid
Structural Forces as a Tool for Particle Characterization
and Control of Dispersion Stability,” Physical Chemistry
Chemical Physics, vol. 9, no. 38, pp. 5183–5198, 2007.
E. Dickinson, “Food Emulsions and Foams: Stabilization
by Particles,” Current Opinion in Colloid &Interface
Science, vol. 15, no. 1, pp. 40–49, 2010, ISSN: 1359-
0294. doi: 10.1016/j.cocis.2009.11.001.
S. Yang, R. Pelton, A. Raegen, M. Montgomery, and K.
Dalnoki-Veress, “Nanoparticle Flotation Collectors:
Mechanisms Behind a New Technology,” Langmuir,
vol. 27, no. 17, pp. 10438–10446, 2011, ISSN:
07437463. doi: 10.1021/la2016534.
S. Ata, “Coalescence of Bubbles Covered by Particles,”
Langmuir, vol. 24, no. 12, pp. 6085–6091, 2008,
ISSN: 07437463. doi: 10.1021/la800466x.
B. Albijanic, O. Ozdemir, A. V. Nguyen, and D. Bradshaw,
“A Review of Induction and Attachment Times of
Wetting Thin Films Between Air Bubbles and Particles
and Its Relevance in the Separation of Particles by
Flotation,” Advances in Colloid and Interface Science,
vol. 159, no. 1, pp. 1–21, 2010, ISSN: 00018686. doi:
10.1016/j.cis.2010.04.003.
A. V. Nguyen, D.-A. An-Vo, T. Tran-Cong, and G. M.
Evans, “A Review of Stochastic Description of the
Turbulence Effect on Bubble-Particle Interactions in
Flotation,” International Journal of Mineral Processing,
vol. 156, pp. 75–86, 2016, In Honor of Professor
Heinrich Schubert on his 90th birthday, ISSN: 0301-
7516. doi: 10.1016/j.minpro.2016.05.002.
M. Eftekhari, K. Schwarzenberger, A. Javadi, and K.
Eckert, “The Influence of Negatively Charged Silica
Nanoparticles on the Surface Properties of Anionic
Surfactants: Electrostatic Repulsion or the Effect of
Ionic Strength?” Physical Chemistry Chemical Physics,
vol. 22, no. 4, pp. 2238–2248, 2020.
M. Eftekhari, K. Schwarzenberger, P. Schlereth, and K.
Eckert, “Dynamics of Particle Attachment in a Model
Stirred Cell: A New Technique to Characterize and
Quantify Particle Floatability,” Minerals Engineering,
vol. 210, p. 108643, 2024, ISSN: 0892-6875. doi:
10.1016/j.mineng.2024.108643.
M. Eftekhari, K. Schwarzenberger, S. I. Karakashev, N. A.
Grozev, and K. Eckert, “Oppositely Charged Surfactants
and Nanoparticles at the Air-Water Interface: Influence
of Surfactant to Nanoparticle Ratio,” Journal of Colloid
and Interface Science, vol. 653, pp. 1388–1401, 2024.

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2794
Turbulence Measurement Techniques for Multiphase Flows in
Mechanical Flotation Cells
Weiguo Xie
Department of Chemical Engineering, University of Minnesota Duluth, USA
Eiman Amini
ORICA Limited, Brisbane, Australia
ABSTRACT: Turbulence is an important factor affecting flotation performance. It affects air dispersion, particle
suspension, bubble-particle collection interactions, and entrainment of fine particles. However, quantifying
turbulence in multiphase flows has always been an enormous scientific challenge. In this paper, many turbulence
measurement techniques will be reviewed and compared including Laser Doppler Anemometry (LDA), Particle
Image Velocimetry (PIV), Positron Emission Particle Tracking (PEPT), Constant Temperature Anemometer
(CTA), Piezoelectric Vibration Sensor (PVS), and Electrical Resistance Tomography (ERT). The turbulence
profile obtained from measurement techniques can lead to better process knowledge and control of multiphase
flows in mechanical flotation cells.
Keywords Turbulence Measurement Techniques Multiphase Flows, Mechanical Flotation Cells
INTRODUCTION
Turbulence was first introduced by William Thomson in
1887 (Schmitt, 2017). Despite its paramount importance in
our lives, turbulence remains “the most important unsolved
problem of classical physics” according to the American
Nobel Prize Laureate for Physics Richard Feynman (Eames
and Flor, 2011). Turbulence is an important factor affecting
flotation performance in mineral processing. It affects air
dispersion, particle suspension, bubble-particle collection
interactions, and entrainment of fine particles (Fallenius,
1987 Schubert, 1999 Nguyen &Schulze, 2004 Evans et
al., 2008). Quantification of turbulent flows requires the
measurement of the fluctuating transport properties (mass,
constituent’s phase, heat, momentum, and energy) at a
high spatial and temporal resolution. Measurements of the
transition to turbulence in multiphase flows have long been
problematic. The environment inside multiphase flows is
highly aggressive, abrasive, and opaque. Most of the tra-
ditional fluid measurement techniques cannot be applied
(Xie, et al., 2016). For example, the flotation cell is often
treated as a “black-box” because we can only see the froth
surface (e.g., in Figure 1), making it challenging to obtain
information about the underlying slurry.
In this paper, many turbulence measurement tech-
niques will be reviewed and compared. Some of the mea-
surement techniques that have been used for the study of
fluid characteristics are described below. Optical techniques
such as Laser Doppler Anemometry (Tiitinen, et al., 2003
Kyselaa et al., 2013) and Particle Image Velocimetry (Baldi,
et al., 2002 Darabi, et al., 2017) can produce accurate mea-
surements with high spatial and temporal resolution, but

Previous Page Next Page

Extracted Text (may have errors)

2794
Turbulence Measurement Techniques for Multiphase Flows in
Mechanical Flotation Cells
Weiguo Xie
Department of Chemical Engineering, University of Minnesota Duluth, USA
Eiman Amini
ORICA Limited, Brisbane, Australia
ABSTRACT: Turbulence is an important factor affecting flotation performance. It affects air dispersion, particle
suspension, bubble-particle collection interactions, and entrainment of fine particles. However, quantifying
turbulence in multiphase flows has always been an enormous scientific challenge. In this paper, many turbulence
measurement techniques will be reviewed and compared including Laser Doppler Anemometry (LDA), Particle
Image Velocimetry (PIV), Positron Emission Particle Tracking (PEPT), Constant Temperature Anemometer
(CTA), Piezoelectric Vibration Sensor (PVS), and Electrical Resistance Tomography (ERT). The turbulence
profile obtained from measurement techniques can lead to better process knowledge and control of multiphase
flows in mechanical flotation cells.
Keywords Turbulence Measurement Techniques Multiphase Flows, Mechanical Flotation Cells
INTRODUCTION
Turbulence was first introduced by William Thomson in
1887 (Schmitt, 2017). Despite its paramount importance in
our lives, turbulence remains “the most important unsolved
problem of classical physics” according to the American
Nobel Prize Laureate for Physics Richard Feynman (Eames
and Flor, 2011). Turbulence is an important factor affecting
flotation performance in mineral processing. It affects air
dispersion, particle suspension, bubble-particle collection
interactions, and entrainment of fine particles (Fallenius,
1987 Schubert, 1999 Nguyen &Schulze, 2004 Evans et
al., 2008). Quantification of turbulent flows requires the
measurement of the fluctuating transport properties (mass,
constituent’s phase, heat, momentum, and energy) at a
high spatial and temporal resolution. Measurements of the
transition to turbulence in multiphase flows have long been
problematic. The environment inside multiphase flows is
highly aggressive, abrasive, and opaque. Most of the tra-
ditional fluid measurement techniques cannot be applied
(Xie, et al., 2016). For example, the flotation cell is often
treated as a “black-box” because we can only see the froth
surface (e.g., in Figure 1), making it challenging to obtain
information about the underlying slurry.
In this paper, many turbulence measurement tech-
niques will be reviewed and compared. Some of the mea-
surement techniques that have been used for the study of
fluid characteristics are described below. Optical techniques
such as Laser Doppler Anemometry (Tiitinen, et al., 2003
Kyselaa et al., 2013) and Particle Image Velocimetry (Baldi,
et al., 2002 Darabi, et al., 2017) can produce accurate mea-
surements with high spatial and temporal resolution, but

2792 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
DISCUSSION ON APPLICABILITY IN
FLOTATION PROCESSES
Figure 8 shows the ratio of the number of attached GBs to
a single bubble in the NPs system to the water system, as a
function time. The values are calculated from slightly modi-
fied version of Equation 1 with KNPs=40, Kw=4, ΘNPs =0.5,
and Θw =0.8. The modification is needed to translate the
surface coverage values to number values, NπR A
p
2 H =.
As can be seen, the number of attached GBs in the
NPs system is initially greater than that in the water sys-
tem. After some time, however, this changes and the num-
ber of GBs in the water system exceeds the number of
GBs in the NP system. It can be concluded that whether
NPs can increase the final recovery in the flotation cell by
these specific mechanisms, i.e., increasing the attachment
probability and decreasing the packing density, depends on
the residence time of the bubble in the flotation cell.
Based on the reported results, it seems that NPs can
increase the attachment probability and thus attachment
rate of the GBs. However, it is not clear if this effect is
caused by the NPs attachment to the GBs as reported by
Yang et al. (Yang et al. 2011), or the change in pH and
ionic strength due to the co-ions of added NPs and surfac-
tants. Moreover, the possibility of surfactant rearrangement
between NPs and GBs cannot be excluded, which means
that GBs can be made more hydrophobic by the surfac-
tant molecules transferred from the surface of the NPs to
the surface of the GBs. Therefore, further experiments such
as SEM, zeta potential and contact angle measurements
are required to properly evaluate the effect of NPs on the
dynamics of particle attachment.
Figure 7. Snapshots to illustrate the packing density of GBs (3gr of 66 µm GBs, conditioned with 0.006
CMC CTAB, and stirred at 400 rpm) on bubble surface for NPSCs (2.0 wt.% NP9 +0.3 CMC CTAB)
that is compressed to from 2.5 mm to 1.5 mm in diameter, following a 1000 s waiting time
Figure 8. N /N
NPSCs
GBs
w
GBs as a function of time. The curves are calculated from Eq. 1 with
K
NPSCs =40, K
w =4, and Θ
NPSCs =0.5, and Θ
w =0.8

Previous Page Next Page

Extracted Text (may have errors)

2792 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
DISCUSSION ON APPLICABILITY IN
FLOTATION PROCESSES
Figure 8 shows the ratio of the number of attached GBs to
a single bubble in the NPs system to the water system, as a
function time. The values are calculated from slightly modi-
fied version of Equation 1 with KNPs=40, Kw=4, ΘNPs =0.5,
and Θw =0.8. The modification is needed to translate the
surface coverage values to number values, NπR A
p
2 H =.
As can be seen, the number of attached GBs in the
NPs system is initially greater than that in the water sys-
tem. After some time, however, this changes and the num-
ber of GBs in the water system exceeds the number of
GBs in the NP system. It can be concluded that whether
NPs can increase the final recovery in the flotation cell by
these specific mechanisms, i.e., increasing the attachment
probability and decreasing the packing density, depends on
the residence time of the bubble in the flotation cell.
Based on the reported results, it seems that NPs can
increase the attachment probability and thus attachment
rate of the GBs. However, it is not clear if this effect is
caused by the NPs attachment to the GBs as reported by
Yang et al. (Yang et al. 2011), or the change in pH and
ionic strength due to the co-ions of added NPs and surfac-
tants. Moreover, the possibility of surfactant rearrangement
between NPs and GBs cannot be excluded, which means
that GBs can be made more hydrophobic by the surfac-
tant molecules transferred from the surface of the NPs to
the surface of the GBs. Therefore, further experiments such
as SEM, zeta potential and contact angle measurements
are required to properly evaluate the effect of NPs on the
dynamics of particle attachment.
Figure 7. Snapshots to illustrate the packing density of GBs (3gr of 66 µm GBs, conditioned with 0.006
CMC CTAB, and stirred at 400 rpm) on bubble surface for NPSCs (2.0 wt.% NP9 +0.3 CMC CTAB)
that is compressed to from 2.5 mm to 1.5 mm in diameter, following a 1000 s waiting time
Figure 8. N /N
NPSCs
GBs
w
GBs as a function of time. The curves are calculated from Eq. 1 with
K
NPSCs =40, K
w =4, and Θ
NPSCs =0.5, and Θ
w =0.8