XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 255
mines (e.g., copper and nickel, lead and zinc, etc) but to
the authors’ knowledge, no such investigations have been
reported to date either.
Leaching
Microwave-induced fractures and enhanced liberation may
also promote greater exposure of phases that can be recov-
ered by gravity separation and leaching, for example during
gold processing, illustrated in Figure 9. Given the typi-
cally low head grades and fine gold grain sizes, association
with pyrite can aid in fracture formation, otherwise coarse
gold grains may be required to provide sufficient thermally
induced stresses.
In a recent unpublished study by Batchelor et al.
(2022), it was demonstrated that gold recovery during
leaching could be increased by 0.5% at a very fine nominal
plant grind size of approximately 20 µm and up to 1% at
70 µm, shown in Figure 10.
Perhaps the best way to save comminution energy is
not to grind ores to begin with. Microwave pre-treatment
for heap leaching operations may aid valuable mineral
exposure during crushing, where the fractures may be
initially exploited (Charikinya and Bradshaw 2017).
Alternately, microwave-induced fractures may enable leach
solution to penetrate the rocks, thereby requiring less to no
crushing. Typical heap leaching flowsheets are illustrated
in Figure 11. Induced-fracture networking and/or greater
exposure may enable higher ultimate values recovery and
also faster kinetics to aid initial pay back of expenditure.
There are few investigations in the published literature for
this application.
Giyani (2023) recently studied microwave pre-treat-
ment for heap leaching using X-ray computed tomography
and experimental leaching. Figure 12 illustrates the internal
fracture networking that may be observed for amenable ore
fragments. The author showed how induced fractures are
related to mineralogy, link sulphide grains through fracture
networking, allow leach solution to penetrate further into
the structure of ore fragments and may reduce the distance
of sulphide mineralisation to an exposed surface, thereby
being more readily available for leaching.
[a] [b]
Cyclone
Ball Mill
Screen
U/F
U/S
Gravity
Gravity Conc.
Flotation
O/F
Conc.
Leach
PLS
Tailings
Tailings
MW
ROM/Crush
SAG Mill
Cyclone
Ball Mill
Cyclone
O/F
O/F
Leach
PLS
Tailings
SAG Mill
MW
ROM/Crush
Figure 9. Typical leaching flowsheets with integrated microwave pre-treatment for [a] leaching of gravity tailings and flotation
concentrate, and [b] leaching of milled feed
O/S
Tailings
U/F
U/F
mines (e.g., copper and nickel, lead and zinc, etc) but to
the authors’ knowledge, no such investigations have been
reported to date either.
Leaching
Microwave-induced fractures and enhanced liberation may
also promote greater exposure of phases that can be recov-
ered by gravity separation and leaching, for example during
gold processing, illustrated in Figure 9. Given the typi-
cally low head grades and fine gold grain sizes, association
with pyrite can aid in fracture formation, otherwise coarse
gold grains may be required to provide sufficient thermally
induced stresses.
In a recent unpublished study by Batchelor et al.
(2022), it was demonstrated that gold recovery during
leaching could be increased by 0.5% at a very fine nominal
plant grind size of approximately 20 µm and up to 1% at
70 µm, shown in Figure 10.
Perhaps the best way to save comminution energy is
not to grind ores to begin with. Microwave pre-treatment
for heap leaching operations may aid valuable mineral
exposure during crushing, where the fractures may be
initially exploited (Charikinya and Bradshaw 2017).
Alternately, microwave-induced fractures may enable leach
solution to penetrate the rocks, thereby requiring less to no
crushing. Typical heap leaching flowsheets are illustrated
in Figure 11. Induced-fracture networking and/or greater
exposure may enable higher ultimate values recovery and
also faster kinetics to aid initial pay back of expenditure.
There are few investigations in the published literature for
this application.
Giyani (2023) recently studied microwave pre-treat-
ment for heap leaching using X-ray computed tomography
and experimental leaching. Figure 12 illustrates the internal
fracture networking that may be observed for amenable ore
fragments. The author showed how induced fractures are
related to mineralogy, link sulphide grains through fracture
networking, allow leach solution to penetrate further into
the structure of ore fragments and may reduce the distance
of sulphide mineralisation to an exposed surface, thereby
being more readily available for leaching.
[a] [b]
Cyclone
Ball Mill
Screen
U/F
U/S
Gravity
Gravity Conc.
Flotation
O/F
Conc.
Leach
PLS
Tailings
Tailings
MW
ROM/Crush
SAG Mill
Cyclone
Ball Mill
Cyclone
O/F
O/F
Leach
PLS
Tailings
SAG Mill
MW
ROM/Crush
Figure 9. Typical leaching flowsheets with integrated microwave pre-treatment for [a] leaching of gravity tailings and flotation
concentrate, and [b] leaching of milled feed
O/S
Tailings
U/F
U/F