XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2929
largely of the fluctuations that are typically experienced when
sampling streams on a concentrator at different times. Taken
these into account, the upgrade ratio (i.e., that between the
concentrate grade after 6 minutes of flotation and the calcu-
lated head grade) varied from 9.6 for the base case to 8.8 and
8.4 for the 5 and 10-pass scenario respectively.
The reason for the reduced kinetics and selectivity
that were being observed after the initial 5-pass peak is
still a matter of further research investigation, but based
on current understanding can most likely be ascribed to
the generation of slimes that passivate the valuable mineral
surfaces, or excessive temperatures that impact on reagent
activity. This appears to be a function of several variables,
including the type of ore and grade of the particular feed
(e.g., rougher, cleaner or tailings). Further work will also
include the measurement of bubble size distributions.
Rougher Scavenger Feed
The corresponding flotation results for the Rougher
Scavenger feed are shown in Figures 4 and 5. As the bank
had a residence time of 26 minutes, a reference rounded
residence time of 10 minutes was used to interpret the
results. The data at 10 minutes were calculated by linear
interpolation between the data points at 6 and 14 minutes
respectively.
As is evident from Figure 4, with the similar recovery
figures for corresponding concentrates, the kinetic results
were grouped much more tightly than those of the Rougher
feed. Compared to the baseline, a 5-pass preconditioning
with the Mach returned a slight recovery increase of 1.3%,
increasing to 2.6% after 15 passes, but at the expense of a
higher mass pull. Again, the increased kinetics after pre-
conditioning all but disappeared towards the latter stages
of flotation.
As was the case with the rougher feed, interpretation of
the grade-recovery data is complicated by the fact that the
calculated 4E head grades of the various Rougher Scavenger
feed samples varied quite substantially, from 3.21 g/t for
the baseline, to 4.8, 4.25 and 4.5 g/t for the 5, 10 and 15
pass samples respectively. Thus, as shown in Figure 5, whilst
the corresponding mass pulls were higher for the precon-
ditioning vs. that of the baseline, the increased head grade
resulted in slightly improved concentrate grades for the 10
and 15 pass scenarios after 10 minutes. Thus, the upgrade
ratio’s after 10 minutes of flotation were reduced from the
6.9 of the baseline to 6.3 for the 10-pass test, and lower for
the other two cases.
Cleaner Feed
Two sets of triplicate tests were conducted on the cleaner
feed slurry, the averaged results of the second set being used
for the analysis. Data from one of these were disregarded
due to high variances between the measured and calculated
4E grades. It should further be noted that the precondi-
tioning involved 10, 20 and 30 passes through the Mach
Reactor rather than the 5, 10 and 15 of the Rougher and
Rougher Scavenger tests. This was based on earlier expe-
rience both in laboratory tests and plant application on
-20
-10
0
10
20
30
40
50
-30 -20 -10 0 10 20 30
4E Recovery diff. (%)
0 Pass 5 pass 10 pass 15 pass
Figure 3. Grade-recovery differential profiles for the Rougher Feed
4E
Grade
d
iff .
(g/t)
largely of the fluctuations that are typically experienced when
sampling streams on a concentrator at different times. Taken
these into account, the upgrade ratio (i.e., that between the
concentrate grade after 6 minutes of flotation and the calcu-
lated head grade) varied from 9.6 for the base case to 8.8 and
8.4 for the 5 and 10-pass scenario respectively.
The reason for the reduced kinetics and selectivity
that were being observed after the initial 5-pass peak is
still a matter of further research investigation, but based
on current understanding can most likely be ascribed to
the generation of slimes that passivate the valuable mineral
surfaces, or excessive temperatures that impact on reagent
activity. This appears to be a function of several variables,
including the type of ore and grade of the particular feed
(e.g., rougher, cleaner or tailings). Further work will also
include the measurement of bubble size distributions.
Rougher Scavenger Feed
The corresponding flotation results for the Rougher
Scavenger feed are shown in Figures 4 and 5. As the bank
had a residence time of 26 minutes, a reference rounded
residence time of 10 minutes was used to interpret the
results. The data at 10 minutes were calculated by linear
interpolation between the data points at 6 and 14 minutes
respectively.
As is evident from Figure 4, with the similar recovery
figures for corresponding concentrates, the kinetic results
were grouped much more tightly than those of the Rougher
feed. Compared to the baseline, a 5-pass preconditioning
with the Mach returned a slight recovery increase of 1.3%,
increasing to 2.6% after 15 passes, but at the expense of a
higher mass pull. Again, the increased kinetics after pre-
conditioning all but disappeared towards the latter stages
of flotation.
As was the case with the rougher feed, interpretation of
the grade-recovery data is complicated by the fact that the
calculated 4E head grades of the various Rougher Scavenger
feed samples varied quite substantially, from 3.21 g/t for
the baseline, to 4.8, 4.25 and 4.5 g/t for the 5, 10 and 15
pass samples respectively. Thus, as shown in Figure 5, whilst
the corresponding mass pulls were higher for the precon-
ditioning vs. that of the baseline, the increased head grade
resulted in slightly improved concentrate grades for the 10
and 15 pass scenarios after 10 minutes. Thus, the upgrade
ratio’s after 10 minutes of flotation were reduced from the
6.9 of the baseline to 6.3 for the 10-pass test, and lower for
the other two cases.
Cleaner Feed
Two sets of triplicate tests were conducted on the cleaner
feed slurry, the averaged results of the second set being used
for the analysis. Data from one of these were disregarded
due to high variances between the measured and calculated
4E grades. It should further be noted that the precondi-
tioning involved 10, 20 and 30 passes through the Mach
Reactor rather than the 5, 10 and 15 of the Rougher and
Rougher Scavenger tests. This was based on earlier expe-
rience both in laboratory tests and plant application on
-20
-10
0
10
20
30
40
50
-30 -20 -10 0 10 20 30
4E Recovery diff. (%)
0 Pass 5 pass 10 pass 15 pass
Figure 3. Grade-recovery differential profiles for the Rougher Feed
4E
Grade
d
iff .
(g/t)