2430 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Then, the residence time of pulp circulating through the
impeller was 2.2 s, but considering the pulp circulates five
times through the impeller before leaving the cell, the total
mean residence time was around 11 s. This finding con-
firms that the expected residence time for particles collec-
tion in mechanical flotation cells are quite lower from the
pulp residence time. Consequently, the use of the pulp resi-
dence time significantly underestimates the flotation rates
for kinetic characterization.
INTENSIFIED FLOTATION CELLS
In the last decades, industrial flotation circuits have incor-
porated a new generation of reactor-separator flotation
machines also called intensified flotation cells (Wills and
Finch, 2016 Hassanzadeh et al., 2022a, 2022b). In this
classification, it is the Jameson cell, in which the down-
comer represents the effective collection zone where par-
ticles collection mainly occurs and the feed pulp energy
is mostly dissipated, creating an efficient contact between
pulp and bubbles that are entrained downwards (Garay
and Catalán, 2020 Glencore Technology, 2023). In addi-
tion, using downcomer, there is the Imhoflot cell (Wills
and Finch, 2016), the reflux RFC cell (Cole et al., 2021
Galvin, 2023) and the Concord cell (Jameson, 2018 Yañez
et al., 2024), among others.
An alternative approach for intensified mechanical
contact cell, is the Stage Flotation Reactor SFR, in which
the particle collection unit (PCU) is a smaller and bounded
collection zone whose product discharge to a bubble dis-
engagement unit (BDU), before entering to the final
pulp/froth separation unit (Swedburg and Samuels, 2016
Woodgrove, 2023). Other mechanical alternative is the
StackCell, where particles collection occurs in a smaller
volume (aerator reactor) located inside the conventional
separator tank (Meléndez, 2023).
In the new devices, the collection will occur e.g., in
the downcomer of pneumatic cells (Jameson, 2010 Galvin,
2023), or in the PCU of a SFR cell (Woodgrove, 2023),
where the system provides the greater energy dissipation. In
all cases, after the intensive contact unit a quiescent zone is
required for the bubble-particle aggregates disengagement
from the pulp to enter the pulp-froth interface. In this case,
it is possible to associate the collection residence time with
the time the pulp circulates through the intensive contact
zone, e.g., the downcomer in a Jameson cell or a Reflux
Column, or the PCU in a SFR cell.
a. Jameson cell
Estimation of Downcomer Residence Time
(Effective Collection)
The ratio between the total volume of downcomers (col-
lection zone) and the total cell volume is around 15–16%.
To provide an effective operation the volumetric flow-
rate in the downcomer is typically around 1.6–1.7 times
the fresh feed. Considering a standard feed flowrate of
1200 m3/h, the nominal cell residence time would be
around 4.5 min in the largest device (Glencore Technologies,
2023). Now, for a recycling ratio of 1.65, the residence time
in the collection zone (downcomer) would be around 25.7
seconds. Then, assuming 50% gas holdup in the collection
zone, the collection time would be around 12–13 seconds.
b. Stage Flotation Reactor SFR Cell
Estimation of PCU Residence Time
(Effective Collection)
The volume of the particles collection unit (PCU) relative
to the total cell volume is around 19–22%.
For a nominal pulp residence time in the whole cell
of around 2.3 min, the pulp residence time in the PCU is
around 26–30 seconds. Then assuming a 35% gas holdup
in the PCU the effective collection time would be around
17–20 seconds.
In this type of cells, there is a single pass of particles
through the collection unit PCU, with no recycle from the
bubbles disengagement unit (BDU) and separation zones.
c. Reflux Flotation Column (RFC)
Estimation of Downcomer Residence Time
(Effective Collection)
In a pilot RFC cell, the volume of the downcomer relative
to the total cell volume is around 2–3% (Cole et al., 2021).
In this cell, the effective downcomer residence time in the
system ranged between 0.5–2.2 s, while the cell residence
time was between 19–87 s. Other pilot study on RFC, using
very fine hydrophobic coal particles with low ash, showed
downcomer residence times of less than 1 second (Jiang et
al., 2019). The RFC cell has a separation zone including a
fluidized upper section provided with strong water flowrate
to reduce entrainment and a bottom section with parallel
inclined channels, which favour the bubbles and tailings
separation. Thus, the system allows for increasing pulp and
gas flowrates, providing shorter contact times.
Table 1 shows a summary of estimation on effective
collection residence time in intensified flotation cells,
Then, the residence time of pulp circulating through the
impeller was 2.2 s, but considering the pulp circulates five
times through the impeller before leaving the cell, the total
mean residence time was around 11 s. This finding con-
firms that the expected residence time for particles collec-
tion in mechanical flotation cells are quite lower from the
pulp residence time. Consequently, the use of the pulp resi-
dence time significantly underestimates the flotation rates
for kinetic characterization.
INTENSIFIED FLOTATION CELLS
In the last decades, industrial flotation circuits have incor-
porated a new generation of reactor-separator flotation
machines also called intensified flotation cells (Wills and
Finch, 2016 Hassanzadeh et al., 2022a, 2022b). In this
classification, it is the Jameson cell, in which the down-
comer represents the effective collection zone where par-
ticles collection mainly occurs and the feed pulp energy
is mostly dissipated, creating an efficient contact between
pulp and bubbles that are entrained downwards (Garay
and Catalán, 2020 Glencore Technology, 2023). In addi-
tion, using downcomer, there is the Imhoflot cell (Wills
and Finch, 2016), the reflux RFC cell (Cole et al., 2021
Galvin, 2023) and the Concord cell (Jameson, 2018 Yañez
et al., 2024), among others.
An alternative approach for intensified mechanical
contact cell, is the Stage Flotation Reactor SFR, in which
the particle collection unit (PCU) is a smaller and bounded
collection zone whose product discharge to a bubble dis-
engagement unit (BDU), before entering to the final
pulp/froth separation unit (Swedburg and Samuels, 2016
Woodgrove, 2023). Other mechanical alternative is the
StackCell, where particles collection occurs in a smaller
volume (aerator reactor) located inside the conventional
separator tank (Meléndez, 2023).
In the new devices, the collection will occur e.g., in
the downcomer of pneumatic cells (Jameson, 2010 Galvin,
2023), or in the PCU of a SFR cell (Woodgrove, 2023),
where the system provides the greater energy dissipation. In
all cases, after the intensive contact unit a quiescent zone is
required for the bubble-particle aggregates disengagement
from the pulp to enter the pulp-froth interface. In this case,
it is possible to associate the collection residence time with
the time the pulp circulates through the intensive contact
zone, e.g., the downcomer in a Jameson cell or a Reflux
Column, or the PCU in a SFR cell.
a. Jameson cell
Estimation of Downcomer Residence Time
(Effective Collection)
The ratio between the total volume of downcomers (col-
lection zone) and the total cell volume is around 15–16%.
To provide an effective operation the volumetric flow-
rate in the downcomer is typically around 1.6–1.7 times
the fresh feed. Considering a standard feed flowrate of
1200 m3/h, the nominal cell residence time would be
around 4.5 min in the largest device (Glencore Technologies,
2023). Now, for a recycling ratio of 1.65, the residence time
in the collection zone (downcomer) would be around 25.7
seconds. Then, assuming 50% gas holdup in the collection
zone, the collection time would be around 12–13 seconds.
b. Stage Flotation Reactor SFR Cell
Estimation of PCU Residence Time
(Effective Collection)
The volume of the particles collection unit (PCU) relative
to the total cell volume is around 19–22%.
For a nominal pulp residence time in the whole cell
of around 2.3 min, the pulp residence time in the PCU is
around 26–30 seconds. Then assuming a 35% gas holdup
in the PCU the effective collection time would be around
17–20 seconds.
In this type of cells, there is a single pass of particles
through the collection unit PCU, with no recycle from the
bubbles disengagement unit (BDU) and separation zones.
c. Reflux Flotation Column (RFC)
Estimation of Downcomer Residence Time
(Effective Collection)
In a pilot RFC cell, the volume of the downcomer relative
to the total cell volume is around 2–3% (Cole et al., 2021).
In this cell, the effective downcomer residence time in the
system ranged between 0.5–2.2 s, while the cell residence
time was between 19–87 s. Other pilot study on RFC, using
very fine hydrophobic coal particles with low ash, showed
downcomer residence times of less than 1 second (Jiang et
al., 2019). The RFC cell has a separation zone including a
fluidized upper section provided with strong water flowrate
to reduce entrainment and a bottom section with parallel
inclined channels, which favour the bubbles and tailings
separation. Thus, the system allows for increasing pulp and
gas flowrates, providing shorter contact times.
Table 1 shows a summary of estimation on effective
collection residence time in intensified flotation cells,