3602 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Stage 2: Mechanical liberation (Ultrafine Grinding)
Stage 2 involves the mechanical liberation of precious met-
als from the sulfide matrix. As the operation progresses from
selling a concentrate to producing all doré on site, the intro-
duction of a fine grinding stage may provide an economic
interim solution prior to further processing of the sulfide
minerals. For some concentrates, depending on the uplift
in gold recovery, sufficient liberation of gold from the sul-
fide matrix may be achievable through fine grinding alone,
as was the case for Kalgoorlie Consolidated Gold Mines
in Example 1 below .This example is described in further
detail in previous publications (Ellis, n.d.) (Anderson &
McDonald, 2016).
In the application of GT technologies, Stage 2 includes
the addition of an IsaMill ™ for ultra fine grinding, whereby
strain imparted on the mineral lattice increases activation
energy to facilitate leaching under atmospheric condi-
tions. Simultaneously, the increased surface area after fine
grinding enhances leach kinetics (Hu &Chen, 2004)
(Dakkoune, Bourgeois, Po, &Joulian, 2023 Pease, Young,
&Curry, 2005).
Effective ultrafine grinding (UFG) requires the instal-
lation of specific UFG mills in order to overcome the limi-
tations of conventional mills for fine grinding. Ultrafine
grinding mills use rotating stirrers within a stationary mill
shell and are therefore significantly more energy efficient
in achieving ultrafine grind sizes compared to conventional
mills (Ellis, n.d. Kumar, Sahu, &Tripathy, 2023). The
IsaMill ™ is a well-established, highly efficient fine grinding
mill capable of achieving the tight size distribution required
to enhance the rate of downstream chemical reactions
and ensure consistency in gold recovery in downstream
cyanide leaching.
—————
Example 1: Ultrafine Grinding (UFG) using the IsaMill
as a replacement for roasting—environmental and
economic benefits
Sources: (Ellis, n.d. Anderson &McDonald, 2016).
Opportunities to eliminate an existing roaster were inves-
tigated at Kalgoorlie Consolidated Gold Mines’s (KCGM)
refractory gold processing operation (Gidji Processing
Plant). Alternatives investigated as a part of the project
included:
• Considerations for an acid plant (capture of SO2
from the roaster for generation of sulphuric acid)
• Pressure oxidation
• Biological oxidation
• Ultra Fine Grinding (UFG)
Discounted cash flow economic analyses identified that the
option of an ultra finely ground concentrate directly fed to
the cyanide leach plant had the highest Net Present Value
(NPV) return of all proposed options, and for this reason
was further investigated.
Key design parameters for this project have been sum-
marised in Table E1.1.
The replacement of the roaster was via the installation
of an M3,000 IsaMill ™ designed to achieve P80 10 µm,
and later M10,000 IsaMill ™ designed to achieve a P80
12 µm. Replacing the roasters with fine grinding enabled
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 10 20 30 40 50 60 70 80 90 100
Au Recovery (%)
Figure 3. Grade recovery of Jameson rougher cell (CIS operation)
Au
Grade
(g/t)
Stage 2: Mechanical liberation (Ultrafine Grinding)
Stage 2 involves the mechanical liberation of precious met-
als from the sulfide matrix. As the operation progresses from
selling a concentrate to producing all doré on site, the intro-
duction of a fine grinding stage may provide an economic
interim solution prior to further processing of the sulfide
minerals. For some concentrates, depending on the uplift
in gold recovery, sufficient liberation of gold from the sul-
fide matrix may be achievable through fine grinding alone,
as was the case for Kalgoorlie Consolidated Gold Mines
in Example 1 below .This example is described in further
detail in previous publications (Ellis, n.d.) (Anderson &
McDonald, 2016).
In the application of GT technologies, Stage 2 includes
the addition of an IsaMill ™ for ultra fine grinding, whereby
strain imparted on the mineral lattice increases activation
energy to facilitate leaching under atmospheric condi-
tions. Simultaneously, the increased surface area after fine
grinding enhances leach kinetics (Hu &Chen, 2004)
(Dakkoune, Bourgeois, Po, &Joulian, 2023 Pease, Young,
&Curry, 2005).
Effective ultrafine grinding (UFG) requires the instal-
lation of specific UFG mills in order to overcome the limi-
tations of conventional mills for fine grinding. Ultrafine
grinding mills use rotating stirrers within a stationary mill
shell and are therefore significantly more energy efficient
in achieving ultrafine grind sizes compared to conventional
mills (Ellis, n.d. Kumar, Sahu, &Tripathy, 2023). The
IsaMill ™ is a well-established, highly efficient fine grinding
mill capable of achieving the tight size distribution required
to enhance the rate of downstream chemical reactions
and ensure consistency in gold recovery in downstream
cyanide leaching.
—————
Example 1: Ultrafine Grinding (UFG) using the IsaMill
as a replacement for roasting—environmental and
economic benefits
Sources: (Ellis, n.d. Anderson &McDonald, 2016).
Opportunities to eliminate an existing roaster were inves-
tigated at Kalgoorlie Consolidated Gold Mines’s (KCGM)
refractory gold processing operation (Gidji Processing
Plant). Alternatives investigated as a part of the project
included:
• Considerations for an acid plant (capture of SO2
from the roaster for generation of sulphuric acid)
• Pressure oxidation
• Biological oxidation
• Ultra Fine Grinding (UFG)
Discounted cash flow economic analyses identified that the
option of an ultra finely ground concentrate directly fed to
the cyanide leach plant had the highest Net Present Value
(NPV) return of all proposed options, and for this reason
was further investigated.
Key design parameters for this project have been sum-
marised in Table E1.1.
The replacement of the roaster was via the installation
of an M3,000 IsaMill ™ designed to achieve P80 10 µm,
and later M10,000 IsaMill ™ designed to achieve a P80
12 µm. Replacing the roasters with fine grinding enabled
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 10 20 30 40 50 60 70 80 90 100
Au Recovery (%)
Figure 3. Grade recovery of Jameson rougher cell (CIS operation)
Au
Grade
(g/t)