2776 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
coalescence tendency in a rather quiescent condition (e.g.,
thinning of a horizontal foam film confined between two
air bubbles) (Wang and Yoon, 2009 Wang and Qu, 2012).
Control of bubble coalescence in flotation via externally
introducing dynamic effects provides a new way to improve
flotation process efficiency and smoothness.
The aims of the present paper are to provide a brief
review on the work of flotation process intensification using
low-frequency acoustic sound conducted at The University
of Queensland (Ng et al., 2020a, 2020b, 2021, 2022 Yang
et al., 2023a, 2024) and update readers with the latest test
results obtained at laboratory scale and pilot scale.
FLOTATION TESTS AT
LABORATORY SCALE
Figure2a shows the laboratory scale mechanical flotation
system, comprising a 1.5-liter bottom-driven mechanical
flotation cell with 11 cm of length, 11 cm of width, and
14.5 cm of height. An audio system comprising an under-
water loudspeaker, an amplifier, and a computer was used.
The underwater speaker was placed 0.5 cm above the rotor.
More details can be found elsewhere (Yang et al., 2023a).
Figure2b shows the laboratory scale column flotation sys-
tem, comprising a column with an inner diameter of 5 cm
and height of 150 cm. A loudspeaker that was positioned
above the column cell lip, and an amplifier were used to
adjust the sound frequency and amplitude. To minimise
the sound dissipation, a sound concentrating tube was con-
nected to the speaker. Further details are given elsewhere
(Ng et al., 2020a).
Figure 3 shows that while keeping sound amplitude
at 125 dB within a mechanical flotation cell, the pre-
ferred sound frequency for achieving a high flotation rate
a) b)
10-4 10-3 10-2 0.1
NaCl (M)
10-4 10-3 10-2 0.1
NaCl (M)
Figure 1. Tendency of bubble coalescence affected by fluid
flow condition: a) quiescent condition where the stability of
a horizontal foam film was measured, b) turbulent condition
where turbidity of the gas-liquid system with continuous
bubbling was measured
a)
Immersible
loudspeaker (IP 68)
Agitator
Air supply
Stereo
amplifier
Signal
generator
minimal
gap
Concentrate
b)
Source: Yang et al. 2023a, Ng et al., 2020a.
Figure 2. Laboratory scale experimental setups: a) loudspeaker placed (in slurry) within the mechanical flotation cell, b)
loudspeaker placed (in air) above the flotation column
coalescence tendency in a rather quiescent condition (e.g.,
thinning of a horizontal foam film confined between two
air bubbles) (Wang and Yoon, 2009 Wang and Qu, 2012).
Control of bubble coalescence in flotation via externally
introducing dynamic effects provides a new way to improve
flotation process efficiency and smoothness.
The aims of the present paper are to provide a brief
review on the work of flotation process intensification using
low-frequency acoustic sound conducted at The University
of Queensland (Ng et al., 2020a, 2020b, 2021, 2022 Yang
et al., 2023a, 2024) and update readers with the latest test
results obtained at laboratory scale and pilot scale.
FLOTATION TESTS AT
LABORATORY SCALE
Figure2a shows the laboratory scale mechanical flotation
system, comprising a 1.5-liter bottom-driven mechanical
flotation cell with 11 cm of length, 11 cm of width, and
14.5 cm of height. An audio system comprising an under-
water loudspeaker, an amplifier, and a computer was used.
The underwater speaker was placed 0.5 cm above the rotor.
More details can be found elsewhere (Yang et al., 2023a).
Figure2b shows the laboratory scale column flotation sys-
tem, comprising a column with an inner diameter of 5 cm
and height of 150 cm. A loudspeaker that was positioned
above the column cell lip, and an amplifier were used to
adjust the sound frequency and amplitude. To minimise
the sound dissipation, a sound concentrating tube was con-
nected to the speaker. Further details are given elsewhere
(Ng et al., 2020a).
Figure 3 shows that while keeping sound amplitude
at 125 dB within a mechanical flotation cell, the pre-
ferred sound frequency for achieving a high flotation rate
a) b)
10-4 10-3 10-2 0.1
NaCl (M)
10-4 10-3 10-2 0.1
NaCl (M)
Figure 1. Tendency of bubble coalescence affected by fluid
flow condition: a) quiescent condition where the stability of
a horizontal foam film was measured, b) turbulent condition
where turbidity of the gas-liquid system with continuous
bubbling was measured
a)
Immersible
loudspeaker (IP 68)
Agitator
Air supply
Stereo
amplifier
Signal
generator
minimal
gap
Concentrate
b)
Source: Yang et al. 2023a, Ng et al., 2020a.
Figure 2. Laboratory scale experimental setups: a) loudspeaker placed (in slurry) within the mechanical flotation cell, b)
loudspeaker placed (in air) above the flotation column