2810 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
between pentlandite and quartz is observed when the pulp
density is increased from 0.1 to 17 wt.%. This suggests that
at relatively high densities, the RFC had a preferential bub-
ble-particle interaction affinity for pentlandite, with a cor-
respondingly high enrichment ratio. Dickinson and Galvin
(2014) suspected that high pulp densities could result in a
high effective volume fraction with preferential flotation of
minerals of interest. A high nickel enrichment ratio at low
density may have been the result of high water recovery,
which is less pronounced in the 17 wt.% pulp density tests.
Based on the response variables, the optimal pulp concen-
tration for pentlandite flotation using the RFC was deter-
mined to be 17 wt.%. However, the 2 wt.% pulp density
was used in subsequent experiments due to a limitation in
the available sample mass. Nonetheless, it was envisaged
that a reduction in the silica recovery at the 2 wt.% would
further improve the selectivity of the float at higher density.
Effect of Airflow Rate
Figure 4 shows the nickel recovery and grade under differ-
ent aeration conditions. It was observed that there was an
increase in nickel recovery with an increase in airflow rates.
This is attributed primarily to an increase in mass pull at
high air flow rates. Interestingly there was an increase in
enrichment ratio above an airflow rate of 6 L/min which
suggests a strong positive bias favoured the pentlandite
recovery (Cole et al., 2021). The highest nickel recovery
and enrichment ratio were achieved at an air flowrate of
8 L/min.
Effect of Wash Water Flow Rate
The influence of wash water flow rate on silica and nickel
recovery is shown in Figure 5. While there was a significant
increase in nickel recovery with an increase in wash water,
it was observed that there was a corresponding increase in
silica recovery. This indicates that the use of wash water has
the potential to influence the efficiency of the separation
processes. These results support the observation made by
Uçurum and Bayat (2007) where the optimum flotation
parameters included a relatively low wash water rate of 0.5
L/min but contradict the observations made by Parkes et al.
(2022) where 3 L/min wash water flowrate was adjudged
optimal to reduce silica entrainment. The high recovery of
ultrafine quartz was assigned to a high water recovery at high
wash water flow rates, and a resultantly high quartz enrich-
ment. It has been reported elsewhere that the entrainment
of fine particles has a strong correlation with water recovery
(Zheng et al., 2006). Although silica recovery was high with
increasing wash water, the calculated entrainment factor for
all conditions was below 0.15, with the highest being 0.13
at 3 L/min wash water flow. The optimum condition in
this study offers a caveat for the pseudo-continuous process
Figure 3. Cumulative nickel recovery and silica recovery under varying pulp densities, with the
feed rate of 6 L/min, airflow rate of 6 L/min, and wash water of 3 L/min
between pentlandite and quartz is observed when the pulp
density is increased from 0.1 to 17 wt.%. This suggests that
at relatively high densities, the RFC had a preferential bub-
ble-particle interaction affinity for pentlandite, with a cor-
respondingly high enrichment ratio. Dickinson and Galvin
(2014) suspected that high pulp densities could result in a
high effective volume fraction with preferential flotation of
minerals of interest. A high nickel enrichment ratio at low
density may have been the result of high water recovery,
which is less pronounced in the 17 wt.% pulp density tests.
Based on the response variables, the optimal pulp concen-
tration for pentlandite flotation using the RFC was deter-
mined to be 17 wt.%. However, the 2 wt.% pulp density
was used in subsequent experiments due to a limitation in
the available sample mass. Nonetheless, it was envisaged
that a reduction in the silica recovery at the 2 wt.% would
further improve the selectivity of the float at higher density.
Effect of Airflow Rate
Figure 4 shows the nickel recovery and grade under differ-
ent aeration conditions. It was observed that there was an
increase in nickel recovery with an increase in airflow rates.
This is attributed primarily to an increase in mass pull at
high air flow rates. Interestingly there was an increase in
enrichment ratio above an airflow rate of 6 L/min which
suggests a strong positive bias favoured the pentlandite
recovery (Cole et al., 2021). The highest nickel recovery
and enrichment ratio were achieved at an air flowrate of
8 L/min.
Effect of Wash Water Flow Rate
The influence of wash water flow rate on silica and nickel
recovery is shown in Figure 5. While there was a significant
increase in nickel recovery with an increase in wash water,
it was observed that there was a corresponding increase in
silica recovery. This indicates that the use of wash water has
the potential to influence the efficiency of the separation
processes. These results support the observation made by
Uçurum and Bayat (2007) where the optimum flotation
parameters included a relatively low wash water rate of 0.5
L/min but contradict the observations made by Parkes et al.
(2022) where 3 L/min wash water flowrate was adjudged
optimal to reduce silica entrainment. The high recovery of
ultrafine quartz was assigned to a high water recovery at high
wash water flow rates, and a resultantly high quartz enrich-
ment. It has been reported elsewhere that the entrainment
of fine particles has a strong correlation with water recovery
(Zheng et al., 2006). Although silica recovery was high with
increasing wash water, the calculated entrainment factor for
all conditions was below 0.15, with the highest being 0.13
at 3 L/min wash water flow. The optimum condition in
this study offers a caveat for the pseudo-continuous process
Figure 3. Cumulative nickel recovery and silica recovery under varying pulp densities, with the
feed rate of 6 L/min, airflow rate of 6 L/min, and wash water of 3 L/min