Mining in focus
it comprises a number of additional
flotation steps to upgrade the ore in
order to achieve the desired product.
“The first stage is known as
rougher flotation; after that, the ore
goes through a further six stages
of cleaner flotation. The re-cleaner
tailings are reground and re-floated.
This product joins the mainstream
acidspar circuit. The re-float tails
and first cleaner tails are processed
and forms the product known as
Metspar, a lower-grade fluorspar
product. The acidspar at Nokeng has
a grade of 97.2% calcium fluorite.
This is filtered to contain less than
10% moisture, and the premium
product, which is our acid spar, is
then transported to the port and sold
to international clients,” says Brits.
Most of Nokeng’s clients are based
in the United States and Europe,
but there are other buyers from
other countries around the world.
Metspar contains more than 80%
calcium fluorite, and is used in the
pyrometallurgical metallurgical
industry, mostly for smelting, as it
reduces the temperature at which
smelting takes place and therefore
reduces energy consumption. Local
and international offtake partners for
the product are in place or is in the
process of being negotiated.
Unique flotation
The unique flotation process includes
a conditioning step that requires the
temperature of the mixture to be
increased to more than 60 degrees
Celsius. Therefore, boilers had to be
installed. The increased temperature
significantly improves the separation
of the fluorspar from the gangue
(unwanted minerals). In Nokeng’s
case, the gangue is mainly iron oxide,
which is hematite, and silica.
“To increase the temperature,
several methods can be used, but
all involve energy input. Electricity
springs to mind immediately, but
electricity is only economical in small
amounts. The most efficient and the
most economical way to satisfy the
heat requirements is with coal-fired
boilers. To generate enough steam,
we require low-pressure boilers,”
says Brits. Brits adds that Nokeng
has not signed coal contracts yet, but
are looking at outsourcing the boiler
operation and maintenance to ensure
optimal performance of these units.
The mine has installed four boilers.
Each of the boilers produce about 10
tonnes per hour of steam. The plan
is to have three boilers operating at
any one time and then have a fourth
boiler on standby.
In addition to the mine and
processing facility near Rust de
Winter, SepFluor also plans to
construct a chemical plant in
Bronkhorstspruit, which will
beneficiate the product produced
at the mine. Construction of the
chemical plant is expected to start
within the next two years. Nokeng’s
premium product will be acidspar.
Acidspar is the key ingredient in the
manufacture of hydrofluoric acid
(a solution of hydrogen fluoride in
water) and is a precursor to almost
all fluorine compounds, including
pharmaceuticals such as fluoxetine,
diverse materials such as PTFE, and
elemental fluorine itself.
“Our plan is to develop the
beneficiation of fluorspar by means
of installing a chemicals plant that
is currently in a bankable feasibility
stage, to establish the financial and
the technical requirements. We would
then take the fluorspar produced at
the mine and process it by using other
intermediate products like sulphuric
acid with fluorspar in certain process
Teichmann was awarded the contract to build the tailings dam.
[24] MINING MIRROR NOVEMBER 2018
www.miningmirror.co.za