4
spigotting. Additional future raises will be required to
accommodate tailings disposal. Within the scope of the
assessment two scenarios have been considered:
• Replacing the two centrifugal pumpstations with a
single PD pump station.
• Replacing the centrifugal pump stations with a single
PD pump station combined with improving tailings
dewatering (increase slurry density).
In the first scenario, the only change to the handling system
is the exchange of the centrifugal pumps with a single PD
pumping station. No changes to the tailings properties or
volumes are made. The comparison, therefore, is a trade-off
between pumping technologies.
Retrofitting the first pump station with PD pumps
makes the second pump station obsolete, which has several
operational advantages. The removal of the second pump
station eliminates the necessity to deliver the slurry flow at
a discharge pressure in excess of the required Net Positive
Suction Head (NPSHr). As a result, the total required head
for the single pump station is lower than the cumulative
head of the two pump stations (see Table 2). The required
head is nevertheless too high to allow for re-use of the entire
existing pipeline. As a consequence, the bottom section
of the pipeline requires an upgrade. The topography and
HGL for scenario 1 are given in Figure 2. The volumet-
ric throughput of the pipeline does not change as can be
seen from Table 1. The implication of the relatively large
flow is that four PD pumps will be required to handle the
total flow.
The benefits of applying PD pumping technology can
be optimized when the tailings are densified:
1. Reduced volumetric throughput results in the
need for fewer pumps.
2. Increased solids concentration might reduce the
critical flow velocity, resulting in lower friction
losses.
Dewatering
In the second scenario, the dewatering of the tailings is
improved. Settling test work indicated thickener perfor-
mance could be improved to produce a tailings underflow
of 65% solids concentration by weight.
In general, the overall tailings water recovery as a
percentage of the total water used in processing increases
from typically 50% to 60% for tailings disposal as a slurry,
60% to 70% for tailings disposal as a high-density slurry,
and about 80% for tailings disposal as a high slump paste
(Williams, 2014). The results of settling test work indicated
that a consistent solids concentration of 65% by weight is
achievable through thickening. Therefore, the lab results
are in line with the general theory.
In Table 1, the slurry properties and throughput for
the current and two upgrade scenarios are given. Figure 3
Figure 2. Topography and Hydraulic Grade Line (HGL) of Scenario 1: Single PD pump station, C
w 32%
Table 1. Slurry properties
Current PD PD +Dewatering
Solids throughput 969 t/h 969 t/h 969 t/h
Slurry Density (Sm) 1.270 t/m3 1.270 t/m3 1.787 t/m3
Solids Concentration (Cw) 32% 32% 65%
Volumetric throughput (Q) 2,384 m3/h 2,384 m3/h 834 m3/h
spigotting. Additional future raises will be required to
accommodate tailings disposal. Within the scope of the
assessment two scenarios have been considered:
• Replacing the two centrifugal pumpstations with a
single PD pump station.
• Replacing the centrifugal pump stations with a single
PD pump station combined with improving tailings
dewatering (increase slurry density).
In the first scenario, the only change to the handling system
is the exchange of the centrifugal pumps with a single PD
pumping station. No changes to the tailings properties or
volumes are made. The comparison, therefore, is a trade-off
between pumping technologies.
Retrofitting the first pump station with PD pumps
makes the second pump station obsolete, which has several
operational advantages. The removal of the second pump
station eliminates the necessity to deliver the slurry flow at
a discharge pressure in excess of the required Net Positive
Suction Head (NPSHr). As a result, the total required head
for the single pump station is lower than the cumulative
head of the two pump stations (see Table 2). The required
head is nevertheless too high to allow for re-use of the entire
existing pipeline. As a consequence, the bottom section
of the pipeline requires an upgrade. The topography and
HGL for scenario 1 are given in Figure 2. The volumet-
ric throughput of the pipeline does not change as can be
seen from Table 1. The implication of the relatively large
flow is that four PD pumps will be required to handle the
total flow.
The benefits of applying PD pumping technology can
be optimized when the tailings are densified:
1. Reduced volumetric throughput results in the
need for fewer pumps.
2. Increased solids concentration might reduce the
critical flow velocity, resulting in lower friction
losses.
Dewatering
In the second scenario, the dewatering of the tailings is
improved. Settling test work indicated thickener perfor-
mance could be improved to produce a tailings underflow
of 65% solids concentration by weight.
In general, the overall tailings water recovery as a
percentage of the total water used in processing increases
from typically 50% to 60% for tailings disposal as a slurry,
60% to 70% for tailings disposal as a high-density slurry,
and about 80% for tailings disposal as a high slump paste
(Williams, 2014). The results of settling test work indicated
that a consistent solids concentration of 65% by weight is
achievable through thickening. Therefore, the lab results
are in line with the general theory.
In Table 1, the slurry properties and throughput for
the current and two upgrade scenarios are given. Figure 3
Figure 2. Topography and Hydraulic Grade Line (HGL) of Scenario 1: Single PD pump station, C
w 32%
Table 1. Slurry properties
Current PD PD +Dewatering
Solids throughput 969 t/h 969 t/h 969 t/h
Slurry Density (Sm) 1.270 t/m3 1.270 t/m3 1.787 t/m3
Solids Concentration (Cw) 32% 32% 65%
Volumetric throughput (Q) 2,384 m3/h 2,384 m3/h 834 m3/h