XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2807
detachment efficiencies. This phenomenon is further exac-
erbated by excessive turbulence in the froth layer, a charac-
teristic typically associated with mechanical flotation cells.
The ever-increasing global demand for critical minerals
has necessitated the treatment of complex ore sources while
maintaining the quality of concentrate grade for down-
stream smelting and refinery operations (Ponomarenko et
al., 2021). These complex ore sources mostly require fine
grinding for liberation to improve the rejection of gangue
minerals. Thus, there is growing value in the development
of robust technologies and separation techniques for fine
particle flotation as a solution to bridging the demand-sup-
ply gap (Phiri et al., 2022). More so, the tailings materials
from existing dams that contain fine mineral and metal val-
ues can be reprocessed.
Current mechanical flotation cells have some limita-
tions that makes it difficult to achieve selectivity and min-
eral upgrade at high throughputs. For example, mechanical
flotation cells are operated at a high impeller speed to keep
the particles in suspension and promote collision between
the particles and bubbles. However, this approach can inad-
vertently trigger froth destabilization, consequently result-
ing in high entrainment of unwanted mineral particles and
a decrease in mineral grade (Subrahmanyam and Forssberg,
1988 Wang et al., 2016). Extensive research has been con-
ducted in recent years to develop flotation cells capable of
accommodating either high-turbulence conditions, a quies-
cent environment, or both conditions. The Reflux Flotation
Cell (RFC) is one such flotation cell. This novel device has
been used for both coarse and fine particle flotation (Chen
et al., 2022 Sutherland et al., 2020).
The RFC has three major features -a downcomer,
inclined channels, and a reverse fluidized bed (Figure 1).
The downcomer has a cylindrical cross-section consisting
of two parallel but opposite elongated narrow walls with
an annular porous section each known as sparger plates.
The sparger plates serve as an inlet for high-pressure or
compressed air into the feed slurry flowing at a high veloc-
ity between the two sparger plates. This creates a high feed
flux, compared to a conventional flotation cell (Chen et al.,
2022 Jiang et al., 2019) and generates a high shear rate in
the downcomer which subsequently leads to the produc-
tion of ultra-fine bubbles with high surface area flux. The
downcomer arrangement promotes a high collection effi-
ciency from frequent particle-bubble collisions.
The bubble-particle mixture and the pulp move to the
reversed fluidized bed region. This region is characterized
by a quiescent environment filled with bubbles (Cole et
al., 2020). However, unlike a conventional fluidized bed
where the particles are fluidized upwards, the RFC offers
a different twist with stream-rising bubbles being fluidized
via wash water addition and operating at a flooding point.
The separated bubbles move upwards to be collected by the
overflow launder without forming a froth first and reduce
the occurrence of particle detachment (Cole et al., 2021
Galvin and Dickinson, 2014 Parkes et al., 2022). The wash
water enables the desliming action in the fluidized bed.
The inclined channel, the third major component of
the RFC, utilizes the Boycott effect to curb the issue of
entrainment. The inclined channels have a relatively wide
gap (18–20 mm) between each other and are located at the
lower section of the fluidized bed. This location provides
an opportunity for entrained bubble-particle aggregates to
be separated from the gangue and excess wash water. The
separation process is enabled by the convection generated
at the surface of the inclined channels due to differences
in particle densities in the fluid. The particles with greater
Figure 1. A schematic diagram showing the components of
the Reflux Flotation Cell (Chen et al., 2022)
detachment efficiencies. This phenomenon is further exac-
erbated by excessive turbulence in the froth layer, a charac-
teristic typically associated with mechanical flotation cells.
The ever-increasing global demand for critical minerals
has necessitated the treatment of complex ore sources while
maintaining the quality of concentrate grade for down-
stream smelting and refinery operations (Ponomarenko et
al., 2021). These complex ore sources mostly require fine
grinding for liberation to improve the rejection of gangue
minerals. Thus, there is growing value in the development
of robust technologies and separation techniques for fine
particle flotation as a solution to bridging the demand-sup-
ply gap (Phiri et al., 2022). More so, the tailings materials
from existing dams that contain fine mineral and metal val-
ues can be reprocessed.
Current mechanical flotation cells have some limita-
tions that makes it difficult to achieve selectivity and min-
eral upgrade at high throughputs. For example, mechanical
flotation cells are operated at a high impeller speed to keep
the particles in suspension and promote collision between
the particles and bubbles. However, this approach can inad-
vertently trigger froth destabilization, consequently result-
ing in high entrainment of unwanted mineral particles and
a decrease in mineral grade (Subrahmanyam and Forssberg,
1988 Wang et al., 2016). Extensive research has been con-
ducted in recent years to develop flotation cells capable of
accommodating either high-turbulence conditions, a quies-
cent environment, or both conditions. The Reflux Flotation
Cell (RFC) is one such flotation cell. This novel device has
been used for both coarse and fine particle flotation (Chen
et al., 2022 Sutherland et al., 2020).
The RFC has three major features -a downcomer,
inclined channels, and a reverse fluidized bed (Figure 1).
The downcomer has a cylindrical cross-section consisting
of two parallel but opposite elongated narrow walls with
an annular porous section each known as sparger plates.
The sparger plates serve as an inlet for high-pressure or
compressed air into the feed slurry flowing at a high veloc-
ity between the two sparger plates. This creates a high feed
flux, compared to a conventional flotation cell (Chen et al.,
2022 Jiang et al., 2019) and generates a high shear rate in
the downcomer which subsequently leads to the produc-
tion of ultra-fine bubbles with high surface area flux. The
downcomer arrangement promotes a high collection effi-
ciency from frequent particle-bubble collisions.
The bubble-particle mixture and the pulp move to the
reversed fluidized bed region. This region is characterized
by a quiescent environment filled with bubbles (Cole et
al., 2020). However, unlike a conventional fluidized bed
where the particles are fluidized upwards, the RFC offers
a different twist with stream-rising bubbles being fluidized
via wash water addition and operating at a flooding point.
The separated bubbles move upwards to be collected by the
overflow launder without forming a froth first and reduce
the occurrence of particle detachment (Cole et al., 2021
Galvin and Dickinson, 2014 Parkes et al., 2022). The wash
water enables the desliming action in the fluidized bed.
The inclined channel, the third major component of
the RFC, utilizes the Boycott effect to curb the issue of
entrainment. The inclined channels have a relatively wide
gap (18–20 mm) between each other and are located at the
lower section of the fluidized bed. This location provides
an opportunity for entrained bubble-particle aggregates to
be separated from the gangue and excess wash water. The
separation process is enabled by the convection generated
at the surface of the inclined channels due to differences
in particle densities in the fluid. The particles with greater
Figure 1. A schematic diagram showing the components of
the Reflux Flotation Cell (Chen et al., 2022)