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On the Effective Collection Time in Conventional and
Intensified Flotation Devices
J. Yianatos, P. Vallejos
Department of Chemical and Environmental Engineering, Universidad Técnica Federico Santa María, Chile
ABSTRACT: To characterize the collection process in an industrial flotation device, a typical approach is the
kinetic modelling, assuming a first order process with a rate constant parameter (or rate constant distribution)
and a mean residence time (or residence time distribution). A common practice in conventional mechanical
cells and flotation columns is the use of the effective pulp residence time to estimate the rate constant. The
effective pulp residence time assumes the existence of an effective pulp volume, corresponding to the nominal
cell volume less the froth zone and the gas holdup in the pulp zone. On the other hand, the effective pulp
residence time includes the higher energy dissipation zone, near the rotor-stator, and the remaining pulp
volume, including the less intensive mixing conditions in the middle of the cell and the upper quiescent zone,
below the pulp/froth interface, for bubbles disengagement. This approach underestimates the actual collection
rate in industrial cells due to the overestimation of the effective time required for collection, generating larger
scale-up factors, even after correction of other hydrodynamic and froth effects. At present, there is agreement
that the main particles collection in mechanical cells occurs in the surroundings to the rotor-stator, where the
gas entering the pulp disperses in small bubbles in closer contact with the mineral particles. According to this
condition, new cells design considers an intensive contact zone for particles collection, with smaller volumes,
shorter times, and lower specific energy consumption. Thus, the collection zone operates independently of the
bubble disengagement zone, which can be either a concentric external volume or an independent device. In
this form, it allows for a better estimate of the effective residence time for collection, and the identification of
a proper collection rate constant. However, for the overall flotation process modelling, an additional residence
time is still required to complete the flotation separation process in the bubble disengagement zone and froth
separation zone. Each of these three sections has a specific recovery.
This paper presents the results of industrial measurements of pulp residence times and the estimation of the
effective collection times in conventional cells, and its comparison with the collection residence times of inten-
sified devices, such as pneumatic Jameson and RFC cells, and mechanical SFR and conventional cells. Results
allowed for evaluating a more realistic particles collection time, together with the overall pulp residence time in
flotation devices, to identify scale-up factors from testing at pilot or laboratory to industrial operations.
INTRODUCTION
The flotation process consists of two basic steps, the selec-
tive minerals collection (pulp zone) and the froth transport
(separation zone). The overall flotation recovery depends
on the recovery of the pulp and froth zones. On the other
hand, to evaluate the industrial flotation kinetics a com-
mon approach is to consider the whole process, including
all the inefficiencies related to the collection zone and froth
On the Effective Collection Time in Conventional and
Intensified Flotation Devices
J. Yianatos, P. Vallejos
Department of Chemical and Environmental Engineering, Universidad Técnica Federico Santa María, Chile
ABSTRACT: To characterize the collection process in an industrial flotation device, a typical approach is the
kinetic modelling, assuming a first order process with a rate constant parameter (or rate constant distribution)
and a mean residence time (or residence time distribution). A common practice in conventional mechanical
cells and flotation columns is the use of the effective pulp residence time to estimate the rate constant. The
effective pulp residence time assumes the existence of an effective pulp volume, corresponding to the nominal
cell volume less the froth zone and the gas holdup in the pulp zone. On the other hand, the effective pulp
residence time includes the higher energy dissipation zone, near the rotor-stator, and the remaining pulp
volume, including the less intensive mixing conditions in the middle of the cell and the upper quiescent zone,
below the pulp/froth interface, for bubbles disengagement. This approach underestimates the actual collection
rate in industrial cells due to the overestimation of the effective time required for collection, generating larger
scale-up factors, even after correction of other hydrodynamic and froth effects. At present, there is agreement
that the main particles collection in mechanical cells occurs in the surroundings to the rotor-stator, where the
gas entering the pulp disperses in small bubbles in closer contact with the mineral particles. According to this
condition, new cells design considers an intensive contact zone for particles collection, with smaller volumes,
shorter times, and lower specific energy consumption. Thus, the collection zone operates independently of the
bubble disengagement zone, which can be either a concentric external volume or an independent device. In
this form, it allows for a better estimate of the effective residence time for collection, and the identification of
a proper collection rate constant. However, for the overall flotation process modelling, an additional residence
time is still required to complete the flotation separation process in the bubble disengagement zone and froth
separation zone. Each of these three sections has a specific recovery.
This paper presents the results of industrial measurements of pulp residence times and the estimation of the
effective collection times in conventional cells, and its comparison with the collection residence times of inten-
sified devices, such as pneumatic Jameson and RFC cells, and mechanical SFR and conventional cells. Results
allowed for evaluating a more realistic particles collection time, together with the overall pulp residence time in
flotation devices, to identify scale-up factors from testing at pilot or laboratory to industrial operations.
INTRODUCTION
The flotation process consists of two basic steps, the selec-
tive minerals collection (pulp zone) and the froth transport
(separation zone). The overall flotation recovery depends
on the recovery of the pulp and froth zones. On the other
hand, to evaluate the industrial flotation kinetics a com-
mon approach is to consider the whole process, including
all the inefficiencies related to the collection zone and froth