2710 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
depth method as outlined in the experimental section.
These were then plotted against the froth retention time
(FRT) for each experimental condition (Figure 2). Froth
retention time, in its simplest form is calculated by dividing
the froth depth by the superficial gas velocity. In this case
FRT was varied by varying the froth depth. The superficial
gas velocity was maintained constant. Figure 2 shows that
there is considerable variation in the relationship between
froth recovery and froth retention time depending upon
the different conditions of pulp solids concentration and
amount of ultrafine material present. However, both of
these factors affect the froth stability. It is possible to have
different froth recoveries for the same froth retention time if
the froth stabilities are different. Consider a full-scale flota-
tion bank with all cells operating at the same conditions of
froth depth and superficial gas velocity. The froth recoveries
will be different for each cell, depending on the amount
and type of material that is being introduced to the froth.
To account for the effect of the froth stability on the
froth recovery, froth retention times were divided by the
froth stability. This resulted in the experimental data points
(from the iron ore example in Figure 2) falling onto a com-
mon line as shown in Figure 3 (grey squares). Equation 2
can be fitted to the data, which returns a beta value of 2.4.
A similar study was conducted using a copper- and
nickel-containing PGM ore. However, in this instance a
methodology was attempted to minimise the effort spent
on conducting time-consuming froth recovery tests. In this
case, only three froth recovery values were determined using
the variable froth depth method and these were plotted
against the froth retention time, corrected for froth stabil-
ity, as shown in Figure 3 (blue triangles, Cu, and orange
circles, Ni). Froth recovery and beta values for copper and
nickel were very similar, which lends credibility to the data
as one would expect froth characteristics to be the similar,
irrespective of pulp zone behaviour, particularly in an ore
that is strongly dominated by gangue flotation. The value of
beta for this ore was higher than for the iron ore. A higher
beta value implies a stronger dependence on the froth reten-
tion time and froth stability. That is, froth recovery will
decrease more quickly as the froth retention time increases
or froth stability decreases. This difference between these
two beta values is consistent with the fact that the iron ore
is a bulk float, with between 10% and 30% of the solids
mass being recovered to the concentrate, which stabilises
the froth, while the solids recovery in the Cu-Ni ore was
between 1% and 16%. Particle size and hydrophobicity
also play a role in determining the froth behaviours.
Figure 4 shows the data from the iron ore example
where froth recovery calculated using Equation 2 versus
the froth recovery measured using the method of variable
froth heights (Equation 4) for every condition. This shows
that there is reasonable correlation between them, with an
R2 of 0.67. This implies that a simple froth stability test
will give sufficient information to calculate froth recovery
as long as the measurement can be calibrated by the beta
value. Currently, this would need to be done by one of the
other methods of determining froth recovery, such as the
variable depth method. The benefit of being able to use a
froth stability measurement once it is calibrated, is the ease
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 20 40 60 80 100
FRT (s)
Figure 2. Froth recovery as a function of the froth retention time (FRT) for the reverse flotation
of an itabirite iron ore under varying conditions of fines contents and solids concentrations
Froth
recovery
(-)
depth method as outlined in the experimental section.
These were then plotted against the froth retention time
(FRT) for each experimental condition (Figure 2). Froth
retention time, in its simplest form is calculated by dividing
the froth depth by the superficial gas velocity. In this case
FRT was varied by varying the froth depth. The superficial
gas velocity was maintained constant. Figure 2 shows that
there is considerable variation in the relationship between
froth recovery and froth retention time depending upon
the different conditions of pulp solids concentration and
amount of ultrafine material present. However, both of
these factors affect the froth stability. It is possible to have
different froth recoveries for the same froth retention time if
the froth stabilities are different. Consider a full-scale flota-
tion bank with all cells operating at the same conditions of
froth depth and superficial gas velocity. The froth recoveries
will be different for each cell, depending on the amount
and type of material that is being introduced to the froth.
To account for the effect of the froth stability on the
froth recovery, froth retention times were divided by the
froth stability. This resulted in the experimental data points
(from the iron ore example in Figure 2) falling onto a com-
mon line as shown in Figure 3 (grey squares). Equation 2
can be fitted to the data, which returns a beta value of 2.4.
A similar study was conducted using a copper- and
nickel-containing PGM ore. However, in this instance a
methodology was attempted to minimise the effort spent
on conducting time-consuming froth recovery tests. In this
case, only three froth recovery values were determined using
the variable froth depth method and these were plotted
against the froth retention time, corrected for froth stabil-
ity, as shown in Figure 3 (blue triangles, Cu, and orange
circles, Ni). Froth recovery and beta values for copper and
nickel were very similar, which lends credibility to the data
as one would expect froth characteristics to be the similar,
irrespective of pulp zone behaviour, particularly in an ore
that is strongly dominated by gangue flotation. The value of
beta for this ore was higher than for the iron ore. A higher
beta value implies a stronger dependence on the froth reten-
tion time and froth stability. That is, froth recovery will
decrease more quickly as the froth retention time increases
or froth stability decreases. This difference between these
two beta values is consistent with the fact that the iron ore
is a bulk float, with between 10% and 30% of the solids
mass being recovered to the concentrate, which stabilises
the froth, while the solids recovery in the Cu-Ni ore was
between 1% and 16%. Particle size and hydrophobicity
also play a role in determining the froth behaviours.
Figure 4 shows the data from the iron ore example
where froth recovery calculated using Equation 2 versus
the froth recovery measured using the method of variable
froth heights (Equation 4) for every condition. This shows
that there is reasonable correlation between them, with an
R2 of 0.67. This implies that a simple froth stability test
will give sufficient information to calculate froth recovery
as long as the measurement can be calibrated by the beta
value. Currently, this would need to be done by one of the
other methods of determining froth recovery, such as the
variable depth method. The benefit of being able to use a
froth stability measurement once it is calibrated, is the ease
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 20 40 60 80 100
FRT (s)
Figure 2. Froth recovery as a function of the froth retention time (FRT) for the reverse flotation
of an itabirite iron ore under varying conditions of fines contents and solids concentrations
Froth
recovery
(-)