XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3607
Stage 3: Chemical Liberation (Oxidative Leaching)
A leach residence time of 48 hours was selected, with lime
boil of the discharged leach residue. Reagent requirements
will include 2.8 tonnes per hour of limestone and 1.5
tonnes per hour of oxygen into the reactors. After oxidative
leaching approximately 96% of gold will be recoverable via
cyanide leaching, equating to an uplift in gold recovery of
76% (absolute) attributed to the Albion Process ™.
High Level Scenario Based Financial Analysis
Class 5 level estimates (± 45%, in alignment with AACE
Engineering Guidelines) were prepared for each plant stage.
Using these estimates, a high level economic analysis was
undertaken to investigate three potential scenarios for plant
design and construction for the case study presented above.
The three scenarios are:
• Scenario 1—Whole-of-plant concurrent design,
construction and commissioning
• Scenario 2—Stagewise plant implementation
• Scenario 3—Semi-stagewise plant implementation
(all stages commence concurrently, with commis-
sioning of flotation cells when ready while stages 2
and 3 continue to be constructed)
The following economic indicators have been used and dis-
cussed in the financial analysis.
Net Present Value (NPV) is the discounted value of
all future cash flows (both inflows and outflows) over the
life of the mining operation. The NPV serves as an indica-
tion as to the potential future profitability of an operation.
A positive NPV is indicative of a project being profitable,
whilst a negative NPV is indicative of overall net loss. The
formula used to calculate NPV for the current financial
analysis is as follows:
(NPV i)
CF
1
t
n
t
t
0
=+
=
/
where
CFt =net cash flow at time t
t =time of cash flow (10 years)
i =discount rate (10%)
Internal Rate of Return (IRR) is the discount rate at
which the cumulative present value of all future cash flows
is equal to the initial capital expenditure (that is NPV is
equal to 0). This is a useful way to estimate the profitability
of an operation, as an IRR higher than the discount rate
means value has been added, while an IRR lower than the
discount rate indicates value has been lost.
Payback Time (PBT) is the number of operational
years it takes for the present value of a project’s future
cash flows to equal the initial investment. Ultimately, the
shorter the PBT, the sooner an operation will begin gener-
ating profitable cash flows. Each mining corporation will
have its own threshold for what is considered acceptable
Table 2. ‘Maximum recovery’ concentrate for treatment in
Stages 2 and 3
Mineralogy
Pyrite %9.7
Arsenopyrite %5.9
Quartz %14.0
Muscovite %41.0
Chlorite %8.2
Dolomite %10.0
Grade
Au g/t 18.2
As %4.3
S %10.6
Figure 7. Oxidative leaching testwork—grind sensitivity results
Stage 3: Chemical Liberation (Oxidative Leaching)
A leach residence time of 48 hours was selected, with lime
boil of the discharged leach residue. Reagent requirements
will include 2.8 tonnes per hour of limestone and 1.5
tonnes per hour of oxygen into the reactors. After oxidative
leaching approximately 96% of gold will be recoverable via
cyanide leaching, equating to an uplift in gold recovery of
76% (absolute) attributed to the Albion Process ™.
High Level Scenario Based Financial Analysis
Class 5 level estimates (± 45%, in alignment with AACE
Engineering Guidelines) were prepared for each plant stage.
Using these estimates, a high level economic analysis was
undertaken to investigate three potential scenarios for plant
design and construction for the case study presented above.
The three scenarios are:
• Scenario 1—Whole-of-plant concurrent design,
construction and commissioning
• Scenario 2—Stagewise plant implementation
• Scenario 3—Semi-stagewise plant implementation
(all stages commence concurrently, with commis-
sioning of flotation cells when ready while stages 2
and 3 continue to be constructed)
The following economic indicators have been used and dis-
cussed in the financial analysis.
Net Present Value (NPV) is the discounted value of
all future cash flows (both inflows and outflows) over the
life of the mining operation. The NPV serves as an indica-
tion as to the potential future profitability of an operation.
A positive NPV is indicative of a project being profitable,
whilst a negative NPV is indicative of overall net loss. The
formula used to calculate NPV for the current financial
analysis is as follows:
(NPV i)
CF
1
t
n
t
t
0
=+
=
/
where
CFt =net cash flow at time t
t =time of cash flow (10 years)
i =discount rate (10%)
Internal Rate of Return (IRR) is the discount rate at
which the cumulative present value of all future cash flows
is equal to the initial capital expenditure (that is NPV is
equal to 0). This is a useful way to estimate the profitability
of an operation, as an IRR higher than the discount rate
means value has been added, while an IRR lower than the
discount rate indicates value has been lost.
Payback Time (PBT) is the number of operational
years it takes for the present value of a project’s future
cash flows to equal the initial investment. Ultimately, the
shorter the PBT, the sooner an operation will begin gener-
ating profitable cash flows. Each mining corporation will
have its own threshold for what is considered acceptable
Table 2. ‘Maximum recovery’ concentrate for treatment in
Stages 2 and 3
Mineralogy
Pyrite %9.7
Arsenopyrite %5.9
Quartz %14.0
Muscovite %41.0
Chlorite %8.2
Dolomite %10.0
Grade
Au g/t 18.2
As %4.3
S %10.6
Figure 7. Oxidative leaching testwork—grind sensitivity results