6
can be concluded that changing pumping technology com-
bined with dewatering the tailings results in a 57% reduc-
tion in emissions. A 23% reduction is achieved when the
pumping system is solely upgraded with more efficient PD
pumping technology
Operational Costs
The operational costs of the three scenarios have been calcu-
lated using the results from the absorbed power and water
usage calculations. For the base case the unit costs of power
are taken at $0.10 per kWh and water costs are taken at
$1.00 per cubic meter. Maintenance costs including spares
and maintenance hours are estimated based on pump selec-
tion and empirical data of site and identical applications.
The emissions related to the absorbed power are included
at a tax rate of $30 per tonne CO2 as a base case. Pumping
costs in the current setup is approximately $0.80 per cubic
meter. Upgrading the pumping technology reduces oper-
ating costs by 13%. This impact is less than might be
expected based on the improved efficiency of applying a PD
pump. Although the total absorbed power is reduced by the
improved pump efficiency, the power required for thicken-
ing of the tailings does not change. Thickening makes up
approximately 15% of the power consumption therefore
the total reduction in absorbed power is dampened.
When the improved efficiency concurs with a reduc-
tion is total pumped volume the reduction in absorbed
power is maximised, provided that the thickened tailings /
paste can be pumped at lower flow velocity, thus avoiding
excessive pressure loss increases. To illustrate this relation-
ship the equation for the calculation of absorbed power is
given in equation 1.
*
P
Q p
h =(1)
In which P is absorbed power in kWh, Q is flow rate in
m3/h, p is pressure in kPa and η is pump efficiency.
Optimizing tailings dewatering by installing high-rate
or paste thickeners reduces the total volume of tailings
without a major increase in absorbed power for dewatering.
Increasing solids concentration of the tailings reduces
the operational costs by 61% compared to the current
situation. From Figure 6 it can be concluded that when
upgrading only pumping technology, the cost reduction
is driven by maintenance costs and absorbed power. Only
when increasing slurry density water costs decrease and the
reduction in operating costs is optimised.
Capital Costs
The capital costs required for the proposed upgrades
includes the replacement of the lower section of the pipeline.
Pumpstation 1, located at the processing plant at the start of
the pipeline, will be used to fit the new pumps. Upgrading
the current thickeners will be required to achieve a higher
solids concentration. An investment of approximately $20
Figure 4. Water balance of tailings
Figure 5. Emissions in tonnes CO2 per annum for each of
the considered scenarios
can be concluded that changing pumping technology com-
bined with dewatering the tailings results in a 57% reduc-
tion in emissions. A 23% reduction is achieved when the
pumping system is solely upgraded with more efficient PD
pumping technology
Operational Costs
The operational costs of the three scenarios have been calcu-
lated using the results from the absorbed power and water
usage calculations. For the base case the unit costs of power
are taken at $0.10 per kWh and water costs are taken at
$1.00 per cubic meter. Maintenance costs including spares
and maintenance hours are estimated based on pump selec-
tion and empirical data of site and identical applications.
The emissions related to the absorbed power are included
at a tax rate of $30 per tonne CO2 as a base case. Pumping
costs in the current setup is approximately $0.80 per cubic
meter. Upgrading the pumping technology reduces oper-
ating costs by 13%. This impact is less than might be
expected based on the improved efficiency of applying a PD
pump. Although the total absorbed power is reduced by the
improved pump efficiency, the power required for thicken-
ing of the tailings does not change. Thickening makes up
approximately 15% of the power consumption therefore
the total reduction in absorbed power is dampened.
When the improved efficiency concurs with a reduc-
tion is total pumped volume the reduction in absorbed
power is maximised, provided that the thickened tailings /
paste can be pumped at lower flow velocity, thus avoiding
excessive pressure loss increases. To illustrate this relation-
ship the equation for the calculation of absorbed power is
given in equation 1.
*
P
Q p
h =(1)
In which P is absorbed power in kWh, Q is flow rate in
m3/h, p is pressure in kPa and η is pump efficiency.
Optimizing tailings dewatering by installing high-rate
or paste thickeners reduces the total volume of tailings
without a major increase in absorbed power for dewatering.
Increasing solids concentration of the tailings reduces
the operational costs by 61% compared to the current
situation. From Figure 6 it can be concluded that when
upgrading only pumping technology, the cost reduction
is driven by maintenance costs and absorbed power. Only
when increasing slurry density water costs decrease and the
reduction in operating costs is optimised.
Capital Costs
The capital costs required for the proposed upgrades
includes the replacement of the lower section of the pipeline.
Pumpstation 1, located at the processing plant at the start of
the pipeline, will be used to fit the new pumps. Upgrading
the current thickeners will be required to achieve a higher
solids concentration. An investment of approximately $20
Figure 4. Water balance of tailings
Figure 5. Emissions in tonnes CO2 per annum for each of
the considered scenarios