Pan European Networks - Horizon 2020 - page 87

for this deposit in order to maintain the integrity of the graphite
while maximising grade. This is in an effort to preserve the
morphology of the native graphite in terms of size but also in
terms of bending, balling, encapsulating contaminants and the
minimisation of mechanically induced faults in the crystal
structure. For the larger sizes, these contaminants can be removed
by screening or by hand to achieve grades in excess of 99%.
Flotation can achieve the same results for the smaller sized, lower
grade material, with almost half the graphite floating without the
use of collector hydrocarbons. Similar techniques will work on
other vein type deposits, and other such specialised processing
plants are also being considered at a number of other locations.
Elcora can also work with graphite found within marbles,
weathered schist and gneisses and various other deposit types.
The company is actively pursuing the processing of other mines’
graphite products where such graphite meets our clients’
specifications, is amenable to our processes, and has not been
degraded by inappropriate mining methods.
The final purification stage, refining, typically involves final
liberation, additional physical separations and, possibly, the
application of hydrometallurgy, pyrometallurgy or gas reaction
technologies. The design and operation of this type of refinery
is both deposit and client specific and requires various
combinations of reaction circuits. Examples are the removal
of boron, sulphur, heavy metals, carbonates, mica, or
other contaminants.
As there is significant overlap in the requirements from one
deposit to another, or from one client to another, a central refinery
is being considered that has interchangeable process modules
and is highly instrumented for quality control purposes. These
circuits are designed to prevent inadvertent production of either
graphene oxides or sub-micrometre-sized contaminated
precipitates and to maintain the integrity of the complete graphite
crystal. Elcora is currently working towards agreements to feed a
refinery based in Port Elizabeth, South Africa, that will take
graphite from sources in southern Africa and ports on the Indian
Ocean in countries such as Madagascar and Sri Lanka.
Design and integration
The mining, processing and refining chains have been designed
and are integrated with each other to produce a consistent, high
quality, standardised graphite product that is suitable for high
yield graphene production. The flat aspect of the graphite product
means that minimal energy is needed for exfoliation and that
yields are maximal. The process involves the application of forces
that exploit the anisotropic characteristics of graphite to pull
single, or a few, layers of graphite from the parent graphite crystal,
as well as chemistry to provide the proper environment to ensure
that the graphene does not fold or reform into graphite while
maintaining the size of the graphene sheet.
The low energy levels also mean that the graphene size can be
increased compared to current methods, dependent upon the
characteristics of the suspending fluids, as the energy levels
used are significantly lower than those required to break the in-
plane crystal. This lower energy means that the process itself
causes minimal damage to the resulting graphene in terms of
crystal imperfections.
Elcora has also developed techniques to break the in-plane
crystals so that the graphene crystal surface area can be
controlled to sizes anywhere smaller than the source graphite. This
means that graphene size can be controlled from the upper size,
limited by the fluid, to the nanometre range. Elcora has been
developing the equipment, circuits and operating environment to
produce industrial scale quantities of graphene that are scalable
from kilogrammes per hour to many tonnes per hour. The intent is
to work with individual clients to determine the graphene
characteristics best suited for their products and to create a
custom process in a suitable location for their needs.
It is Elcora’s aim to work closely with clients in order to provide
them graphene, or high quality graphite, that is suitable for their
requirements. In the long term this will mean tailoring any point
on the supply chain to the production of suitable graphite, mining
for the source graphite, and processing and refining to control
contaminants and the graphene production process to determine
final sheet sizes and imperfections.
Troy Grant
tel :
+1 (902) 802-8847
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