3360 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The pressure between the rolls is controlled between 90 and
150 bar.
HPGR is an excellent choice as a comminution alter-
native where the energy efficiency compared to conven-
tional crushers and mills is lower. Specific energy is the net
power draw per unit of throughput (typically 1.8 kWh/t
for pegmatite ore). Twenty years ago, the practical crush-
ing limit was P80 12.7 mm however with the advent of
HPGR we can crush to P80 8 mm or down to P80 1.7 mm
in close circuit with a screen. The significance of this for
Dense Media Separation (DMS) is very useful where the
crush size can be altered to match the crystal liberation size.
HPGR’s have been very successful in crushing with these
hard abrasive pegmatite ores for this reason.
ORE SORTING
Ore sorting based on colour differences works extremely
well sorting pegmatite from country rock which is usually
darker in colour. Ideally sorting jaw crushed rock is most
cost effective at around 150 mm. x-ray transmission sorting
can also be used and even with colour to achieve an opti-
mum outcome. X-rays are powerful and can penetrate the
rock up to 8 cm and give a better picture of the ore below
the surface. The microelectronics can make a decision to
accept or reject a rock based on the sensing and using an
air blast to change the trajectory of a rock. This has proven
to be very effective separating spodumene and basalt in
Australia at Galaxy, Pilbara Minerals and Mt Marion.
This is also described in a paper by Rohleder (2018), on
Keliber lithium ore project in Finland. It gives significantly
improved metallurgical results and reduces the need to
grind barren rock.
DENSE MEDIA
Spodumene ore can be concentrated in large particle size of
1–6 mm by a dense media separation (DMS) process. The
concentrate typically contains relatively large amounts of
impurities due to the incomplete liberation of spodumene
and the quite narrow density difference between spodu-
mene and gangue minerals. Ferrosilicon is used to create
the separation media of say 3.1, noting that spodumene has
a specific gravity (SG) of 3.2 and quartz has an SG of 2.7,
plagioclase and albite are 2.6. The fine ferrosilicon used to
create the slurry density of say 3.1 is recovered using mag-
nets for both the tailings and concentrate and recycled back
to the feed. In some cases, a coarse and fine dense media
cyclone circuit is used. The limit of this technology is prac-
tically 1 mm particle size.
HPGR has proven to be very good technology to
prepare the feed close circuited with a screen for DMS
processing. Provided the feed is deslimed, this is very effi-
cient separating technology for LPPO ores (Figure 3).
GRAVITY SEPARATION
Tantalum, niobium and tin are often associated with LPPO
deposits and due to their high SG are recovered using
spirals or centrifugal concentrators, such as the Knelson
Concentrator (Figure 4). The preference is to recover at the
coarsest possible size as recovery is reduced for lower par-
ticle sizes.
Heavy liquid separation is a very indicative test to pre-
dict likely gravity recovery from these ores.
Preconcentration and recovery of lithium minerals
using a Dyna Whirlpool processor was described by Lien
(1978).
MAGNETIC SEPARATION
Magnetic separation is used to separate hematite or magne-
tite from lithium concentrates. Iron is undesirable in spod-
umene concentrates affecting the downstream conversion
in a negative manner. Low intensity magnetic separation
(LIMS) has been used to remove magnetite from a lithium
ore followed by wet high intensity magnetic separation
(WHIMS) to produce a tantalite, niobite concentrate, and
tailings consisting of cassiterite.
REFLUX CLASSIFIERS
The Reflux Classifier (RC) was invented by Professor
Kevin Galvin of the University of Newcastle. The patented
REFLUX ® Classifier is one of our most advanced fine-par-
ticle, gravity-based separators, offering significant advan-
tages in capacity, adaptability and efficiency. Incorporating
the new “laminar high-shear-rate” mechanism, along with
other advancements, REFLUX Classifiers are both efficient
and compact (Figure 5). This, along with advancements in
channel spacing and width mean that REFLUX classifiers
are more efficient and more compact than competing fine
coal and mineral processing equipment.
RC testing on a surface sample of pegmatite ore,
involved cone crushing to –32 mm followed by a HPGR
crush to –3.35 mm and screened at 0.18 mm to simulate
the de-grit cyclone. The –3.35 mm +0.18 mm material was
then processed through an RC unit. The testing yielded an
overflow that was 31.5% of the mass, containing 14.1%
of the lithium and resulted in 49.9% mica removal. This
again demonstrated the ability to remove mica selectively
using an RC unit, however the lithium losses were higher
than desired.
The pressure between the rolls is controlled between 90 and
150 bar.
HPGR is an excellent choice as a comminution alter-
native where the energy efficiency compared to conven-
tional crushers and mills is lower. Specific energy is the net
power draw per unit of throughput (typically 1.8 kWh/t
for pegmatite ore). Twenty years ago, the practical crush-
ing limit was P80 12.7 mm however with the advent of
HPGR we can crush to P80 8 mm or down to P80 1.7 mm
in close circuit with a screen. The significance of this for
Dense Media Separation (DMS) is very useful where the
crush size can be altered to match the crystal liberation size.
HPGR’s have been very successful in crushing with these
hard abrasive pegmatite ores for this reason.
ORE SORTING
Ore sorting based on colour differences works extremely
well sorting pegmatite from country rock which is usually
darker in colour. Ideally sorting jaw crushed rock is most
cost effective at around 150 mm. x-ray transmission sorting
can also be used and even with colour to achieve an opti-
mum outcome. X-rays are powerful and can penetrate the
rock up to 8 cm and give a better picture of the ore below
the surface. The microelectronics can make a decision to
accept or reject a rock based on the sensing and using an
air blast to change the trajectory of a rock. This has proven
to be very effective separating spodumene and basalt in
Australia at Galaxy, Pilbara Minerals and Mt Marion.
This is also described in a paper by Rohleder (2018), on
Keliber lithium ore project in Finland. It gives significantly
improved metallurgical results and reduces the need to
grind barren rock.
DENSE MEDIA
Spodumene ore can be concentrated in large particle size of
1–6 mm by a dense media separation (DMS) process. The
concentrate typically contains relatively large amounts of
impurities due to the incomplete liberation of spodumene
and the quite narrow density difference between spodu-
mene and gangue minerals. Ferrosilicon is used to create
the separation media of say 3.1, noting that spodumene has
a specific gravity (SG) of 3.2 and quartz has an SG of 2.7,
plagioclase and albite are 2.6. The fine ferrosilicon used to
create the slurry density of say 3.1 is recovered using mag-
nets for both the tailings and concentrate and recycled back
to the feed. In some cases, a coarse and fine dense media
cyclone circuit is used. The limit of this technology is prac-
tically 1 mm particle size.
HPGR has proven to be very good technology to
prepare the feed close circuited with a screen for DMS
processing. Provided the feed is deslimed, this is very effi-
cient separating technology for LPPO ores (Figure 3).
GRAVITY SEPARATION
Tantalum, niobium and tin are often associated with LPPO
deposits and due to their high SG are recovered using
spirals or centrifugal concentrators, such as the Knelson
Concentrator (Figure 4). The preference is to recover at the
coarsest possible size as recovery is reduced for lower par-
ticle sizes.
Heavy liquid separation is a very indicative test to pre-
dict likely gravity recovery from these ores.
Preconcentration and recovery of lithium minerals
using a Dyna Whirlpool processor was described by Lien
(1978).
MAGNETIC SEPARATION
Magnetic separation is used to separate hematite or magne-
tite from lithium concentrates. Iron is undesirable in spod-
umene concentrates affecting the downstream conversion
in a negative manner. Low intensity magnetic separation
(LIMS) has been used to remove magnetite from a lithium
ore followed by wet high intensity magnetic separation
(WHIMS) to produce a tantalite, niobite concentrate, and
tailings consisting of cassiterite.
REFLUX CLASSIFIERS
The Reflux Classifier (RC) was invented by Professor
Kevin Galvin of the University of Newcastle. The patented
REFLUX ® Classifier is one of our most advanced fine-par-
ticle, gravity-based separators, offering significant advan-
tages in capacity, adaptability and efficiency. Incorporating
the new “laminar high-shear-rate” mechanism, along with
other advancements, REFLUX Classifiers are both efficient
and compact (Figure 5). This, along with advancements in
channel spacing and width mean that REFLUX classifiers
are more efficient and more compact than competing fine
coal and mineral processing equipment.
RC testing on a surface sample of pegmatite ore,
involved cone crushing to –32 mm followed by a HPGR
crush to –3.35 mm and screened at 0.18 mm to simulate
the de-grit cyclone. The –3.35 mm +0.18 mm material was
then processed through an RC unit. The testing yielded an
overflow that was 31.5% of the mass, containing 14.1%
of the lithium and resulted in 49.9% mica removal. This
again demonstrated the ability to remove mica selectively
using an RC unit, however the lithium losses were higher
than desired.
