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High-velocity Impact Breakage for Lower Energy Consumption in Dry Comminution by VeRo Liberator ® Technique

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The brief paper gives a summary of the working principle behind the break-through technology of the VeRo Liberator high velocity impact comminution system. Highly reduced energy consumption and more efficient breakage in the comminution of ores have been predicted based on theoretical modelling for some time. The VeRo Liberator achieves these goals and additionally operates dry and at very low noise levels. The market entry has now been achieved some 5 years after invention.
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334
Praxis und Wissen
© Springer-Verlag GmbH Austria, ein Teil von Springer Nature BHM, 163. Jg.(201 8), Heft 8
Online publiziert: 14. Juni 2018
Praxis und Wissen
High-velocity Impact Breakage
for Lower Energy Consumption
in Dry Comminution by VeRo
Liberator® Technique
The common and widespread applica-
tion of either traditional ball mills or
more modern SAG mills in the com-
minution of ores is characterised by
both technical and economic advan-
tages and disadvantages. The positive
aspects of great robustness and large
unit size of these techniques are incre-
asingly challenged by the highly in-
efficient, slow surface breakage, the
dependency on process water, and es-
pecially the high and wasteful energy
consumption. The inefficiency of SAG
mills stems from the fact that break-
age from a single impact is rare and
most particle collisions result in par-
tial abrasion only. According to Mor-
rison etal. (Minerals Engineering, 20,
3, 303–309, https://doi.org/10.1016/j.
mineng.2006.10.015) such low-veloci-
ty collisions do not exceed the speci-
fic elastic limit of the feed material and
numerous collisions are necessary to
result eventually in breakage. The in-
ternational mining industry has identi-
fied these ineffective characteristics as
systematic bottle necks to future, eco-
nomically as well as ecologically res-
ponsible and sustainable mineral pro-
cessing techniques.
The VeRo Liberator® (Fig. 1) solves
these problems by achieving a high-
ly efficient momentum transfer of the
kinetic impact energy into the materi-
al particle leading rather to breakage
and disintegration than to ineffective
conversion (and loss) of this energy
into heat. While a detailed descripti-
on of the VeRo Liberator® technique
and further references can be found
in Borg etal. 2018 (AT Mineral Proces-
sing, 59, 4, 66–80), in the present short
overview article a brief summary will
suffice.
The new comminution technique
offers innovative dry comminution
by mechanical high-velocity impact
crushing. Since the machine operates
in the high-speed comminution ran-
ge, this technique moves the breaka-
ge away from inefficient low-velocity
and low-energy surface breakage to
fundamentally more efficient impact
breakage. The VeRo Liberator® achie-
ves this fundamental „game-change“
by featuring a unique, vertical, quad-
ruple hollow axle system, which is to-
tally different from (single axle) verti-
cal shaft impact crushers. The hollow
axle system carries a large number
of special steel tools with a length of
up to one meter on three tool levels,
with the fourth level controlling the
air flow within the cylindrical commi-
nution chamber. Extremely high im-
pact speeds are achieved by the coun-
ter-rotation of the tool levels, each of
which can revolve with up to 1600 rpm
in a clockwise and anti-clockwise fa-
shion and thus against each other. The
feed material of up to 120 mm diame-
ter passes continuously and vertically
(gravitationally) from a feeding fun-
nel at the top through the comminuti-
on cylinder, typically within 0 to 25 se-
conds. During this quick pass through
the machine, each particle of the feed
material is hit by multiple impacts at a
high frequency before exiting through
a single bottom opening.
This innovative comminution pro-
cess results in high to extremely high
particle size reduction ratios such as
1:1000 for massive base metal sulp-
hide ores from Rio Tinto, Spain, and
up to 1:6250 for a natural diatomite-
limestone composite ore. The ener-
gy consumption for the comminuti-
on of a wide range of feed materials
from mines all over the world was 35
to over 50% lower compared to con-
ventional comminution systems, both
during in-house tests and tests carried
out by clients. The high-velocity im-
pact crushing process results also in
strongly improved particle liberation
because of the preferential breakage
along phase boundaries. This effect si-
gnificantly reduces incomplete partic-
le liberation, which is traditionally re-
sponsible for the subsequent loss of
commodity minerals during froth flo-
tation. Dry operation without process
water, very low operational noise le-
vels, scalability, modularity, and com-
paratively low wear on tools and li-
ners are additional advantages of the
VeRo Liberator® technique.
The operation principle of the VeRo
Liberator® is primarily based on the
efficient momentum transfer of the ki-
netic impact energy into the impacted
particles. There the shock wave trig-
gers the specific stimulation of the
various mineral components to res-
pond according to their specific elas-
ticity and compressibility moduli.
The differential stimulation results in
stress, building up particularly on pha-
se boundaries and resulting in breaka-
ge nucleation on and fracture propa-
gation along these boundaries. This
theoretical concept was originally pro-
posed based on empirical comminu-
tion test results. Subsequent dyna-
mic uni-axial load tests, followed by
Fig. 1 A prototype of the VeRo Liberator® fitted with conveyor belt and other accessories
335
Praxis und Wissen
BHM 163. Jg.(201 8), Heft 8 © Springer-Verlag GmbH Austria, ein Teil von Springer Nature
numerous high-velocity impact ex-
periments supported and even docu-
mented this working principle in high-
speed video footage (Fig. 2). Such a
style of breakage, caused by high-ve-
locity impacts, had already been the-
oretically predicted and numerically
modelled and visualised by Das and
Cleary in 2010 (Theoretical and Ap-
plied Fracture Mechanics, 53, 47–60)
and is shown in Fig. 3. The VeRo Libe-
rator® achieves this style of breaka-
ge, in which the larger portion of the
material is disintegrated from the ef-
ficient transfer of kinetic energy into
the material without physical contact
with the tools and liners. As a conse-
quence of this contactless disintegra-
tion, the size reduction and particle li-
beration are achieved at significantly
lower energy consumption and with
relatively low wear.
Anglo American has bought two
machines for full industrial-scale pi-
lot testing at their operation sites. An-
glo American supports the VeRo Libe-
rator® technique and is cooperating
closely with PMS GmbH to develop
the technique to further technical le-
vels. Advanced comminution testing
with other clients is currently ongoing.
Acknowledgements
Anglo American is gratefully ack-
nowledged for permission to publish
screen shots of the high-velocity im-
pact experiments and for fruitful dis-
cussions with the staff involved. We
thank Paul Cleary, CSIRO, Austra-
lia, for making the videos of numeri-
cal impact models available to us and
for constructive discussions at Com-
minution ’18. Rob Morrison and Adri-
an Hinde are gratefully acknowledged
for helpful questions and comments
which have improved our understan-
ding of the breakage mechanism.
Gregor Borg1, 2, Felix Scharfe1 and Christof
Lempp2
1 PMS GmbH, Abteistraße1, 20149 Hamburg,
Germany;
gregor.borg@geo.uni-halle.de
felix.scharfe@pms-hh.de
² Martin-Luther-Universität Halle-Wittenberg,
Von-Seck endorff-Platz3,
06120 Germany
Fig. 2 Video screen shots of high-velocity
impact experiments commissioned by Anglo
American, a) initial compression of frontal part
of ore sample (5 × 4 cm in size), b) disintegrati-
on of ore from efficient momentum transfer of
kinetic energy into the particle, c) expansion of
comminuted particle cloud. (Videos courtesy
of Anglo American)
Fig. 3 Video screen shots of numerical mo-
del of high velocity impact (velocity 75 m/s)
of spherical ore particle onto a plate, a) initial
impact with frontal compression, b) internal
breakage from momentum transfer of kine-
tic energy, c) disintegration and expansion.
(Composite image compiled from video provi-
ded by Paul Cleary, CSIRO)
... additional experimental studies on impact breakage included highspeed video footage of ore samples that were ballistically impacted onto a steel tool by a gas cannon. these high-velocity impact experiments have been commissioned by anglo american jointly with PmS Gmbh and anglo american granted permission to publish selected results from this study [16]. two sets of three consecutive images each from two tests at different impact speeds, one at sub-critical speed and one where major disintegration occurs, are shown in Figures 12a, b. the material tested is from a dense, hard, and tough magmatic platinum ore. the ores consist predominantly of pyroxene and plagioclase with minor chromite and sulphide minerals. ...
Article
Full-text available
Mining and mineral processing industry are under pressure from political and social stakeholders to deliver products more sustainably with a much smaller environmental impact. Technical innovations to achieve these goals include reduction in energy consumption, waterless mineral processing, coarse particle liberation, and safe dry stacking of tailings. Traditional, largely abrasional comminution in robust ball and SAG mills is known for its inefficiency with respect to breakage and energy consumption. Earlier theoretical predictions and numerical modelling postulated that more efficient impact breakage should occur at higher impact energies from higher operational velocities. The VeRo Liberator impact crusher operates in such a mechanical high-velocity regime and achieves very high particle size reduction ratios and degrees of particle liberation at very low energy consumption and without using process water. These step-changing comminution results are achieved from high frequency, high-velocity impacts with an efficient momentum transfer that leads to the effective disintegration of the feed material. The empirically tested results have been experimentally simulated and confirmed in static and dynamic uniaxial load tests and high-velocity impact gas cannon tests. The VeRo Liberator technology has currently achieved TRL 7 and several units operate currently at mining operations and test facilities in South Africa.
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