2704 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
particle size distribution carried by the bubble clusters to
the pulp-froth interface. Depending on the experimental
conditions, two distinguished phases of the froth can be
observed: one developed below the pulp surface, and another
developed above the pulp level, for example, as shown in
Figure 3. Hanumanth and Williams (1992) explained that
the former phase is the primary phase and the latter is the
secondary phase. Bubble-particle clusters reach the top of
the pulp level, accumulate, and form a phase adjoining the
liquid phase, which can be referred to the primary phase.
The froth developing on top of the primary phase is termed
as secondary phase. These two phases exhibit some distinct
properties. In the primary phase, the gas volume fraction is
relatively small, and the depth remains constant due to high
water content, preventing bubble coalescence. The particle
concentration is uniform in this phase. In contrast, the sec-
ondary phase has a relatively greater height that depends on
the distance from the froth to the cell lip. Drainage mecha-
nisms occur in the secondary phase, resulting in lower water
content. The particle concentration is also comparatively
lower in the secondary phase, and the size of the bubbles is
much larger than in the primary phase. With these experi-
ments, it can be concluded that fine particles helpdevelope
the secondary froth phase.
Flotation Results
Flotation experiments were carried out to assess the recov-
ery of coarse particles. Figure 4 illustrates the recovery
percentages for three different flotation experiments. The
rate of recovery was found to be highest when there was no
froth phase. This suggests that the absence of a froth phase
can significantly enhance the recovery of coarse particles.
This has also been observed by several other researchers (Soto
and Barbery, 1991 Mankosa et al., 2016 Kohmuench et
al., 2018). However, without the presence of a froth phase,
gangue and lightweight particles, which are elutriated out
of the fluidized bed due to their lower settling velocity than
the fluidization velocity, may enter the concentrate, dete-
riorating the concentrate grade. Therefore, the froth phase
is essential to restrict the flow of non-selected fine gangue
particles into the concentrate.
The recovery rate using the discrete coarse particles was
observed to be almost consistent and linear, meaning that
the particle concentration is similar in the concentrate. This
shows that the froth overflowed from the primary phase,
due to an increase in the gas volume over time, which over-
flows the froth phase. Note that, several experiments were
conducted, and it was found that when the distance from
the cell lip to the pulp level is high, the froth was unable to
overflow. Therefore, for this experiment, the distance from
the cell lip to the pulp was kept at 50 mm to allow the
froth to overflow. As discussed previously, with this particle
size range, the froth phase develops below the pulp surface,
and the froth height remains almost constant. In industries
using coarse particle flotation for phosphate and potash,
Figure 3. Froth phase with (a) coarse particles and (b) fine particles
particle size distribution carried by the bubble clusters to
the pulp-froth interface. Depending on the experimental
conditions, two distinguished phases of the froth can be
observed: one developed below the pulp surface, and another
developed above the pulp level, for example, as shown in
Figure 3. Hanumanth and Williams (1992) explained that
the former phase is the primary phase and the latter is the
secondary phase. Bubble-particle clusters reach the top of
the pulp level, accumulate, and form a phase adjoining the
liquid phase, which can be referred to the primary phase.
The froth developing on top of the primary phase is termed
as secondary phase. These two phases exhibit some distinct
properties. In the primary phase, the gas volume fraction is
relatively small, and the depth remains constant due to high
water content, preventing bubble coalescence. The particle
concentration is uniform in this phase. In contrast, the sec-
ondary phase has a relatively greater height that depends on
the distance from the froth to the cell lip. Drainage mecha-
nisms occur in the secondary phase, resulting in lower water
content. The particle concentration is also comparatively
lower in the secondary phase, and the size of the bubbles is
much larger than in the primary phase. With these experi-
ments, it can be concluded that fine particles helpdevelope
the secondary froth phase.
Flotation Results
Flotation experiments were carried out to assess the recov-
ery of coarse particles. Figure 4 illustrates the recovery
percentages for three different flotation experiments. The
rate of recovery was found to be highest when there was no
froth phase. This suggests that the absence of a froth phase
can significantly enhance the recovery of coarse particles.
This has also been observed by several other researchers (Soto
and Barbery, 1991 Mankosa et al., 2016 Kohmuench et
al., 2018). However, without the presence of a froth phase,
gangue and lightweight particles, which are elutriated out
of the fluidized bed due to their lower settling velocity than
the fluidization velocity, may enter the concentrate, dete-
riorating the concentrate grade. Therefore, the froth phase
is essential to restrict the flow of non-selected fine gangue
particles into the concentrate.
The recovery rate using the discrete coarse particles was
observed to be almost consistent and linear, meaning that
the particle concentration is similar in the concentrate. This
shows that the froth overflowed from the primary phase,
due to an increase in the gas volume over time, which over-
flows the froth phase. Note that, several experiments were
conducted, and it was found that when the distance from
the cell lip to the pulp level is high, the froth was unable to
overflow. Therefore, for this experiment, the distance from
the cell lip to the pulp was kept at 50 mm to allow the
froth to overflow. As discussed previously, with this particle
size range, the froth phase develops below the pulp surface,
and the froth height remains almost constant. In industries
using coarse particle flotation for phosphate and potash,
Figure 3. Froth phase with (a) coarse particles and (b) fine particles