Mine excursion
Koos Carstens, exploration manager at Bureau Veritas (on left),
and Gavin Hefer, commodities director at Bureau Veritas.
than what budding coal entrepreneurs
like to think. The team at the Bureau
Veritas Centurion laboratory does
just that: they dissect, examine, and
test for every possible property,
quality, weakness, and strength in
core samples that could affect the
reserves, resources, and operations
of a coal operation. Besides that,
they live and talk, well, coal.
Koos Carstens, exploration manager
at Bureau Veritas, brings what appears
to be a great chunk of charcoal to life
by explaining that it is coke, produced
from coking coal or metallurgical
coal in the laboratory itself. There
is a significant difference between
coking coal and thermal coal: they
are used in different applications
and the price differs substantially,
with coking coal fetching much
higher prices than thermal coal
on the commodities market.
Coking coal is used in the process
of creating coke that is necessary
for iron and steelmaking. Coke is
a porous, hard conglomeration of
concentrated carbon that is created by
heating bituminous coal without air to
extremely high temperatures. Thermal
coal, also known as steam coal, is
[14] MINING MIRROR MARCH 2018
used for power and heat generation.
In electricity generation, thermal
coal is ground to a powder and fired
into a boiler to produce heat, which
in turn converts water into steam.
“The Bureau Veritas Centurion
laboratory specialises in coking coke
analysis and we also produce coke
on a small scale,” says Carstens.
The laboratory boasts a 7kg coke
oven, in addition to CRI & CSR
testing capabilities and petrographic
testing. “We carry out coking coal
and thermal coal analysis in the
lab,” adds Carstens. Besides its
borehole testing facility in Centurion,
Bureau Veritas has another large,
world-class laboratory in Middelburg,
Mpumalanga. The Centurion lab also
hosts sink/float testing equipment
and can perform drop shatter, froth
flotation, and dry and wet tumble
testing. Moreover, Carstens, as
well as Gavin Hefer, commodities
director at Bureau Veritas, and their
team, are experts in the field and
can provide assistance with scoping
of exploration programmes.
“The Micum tumble test is
specifically for coke and gives us the
cold strength of the coke; that is,
how the coke would stand up to the
rigors of handling in the processes.
Using specific weights of either 25kg
or 50kg of coke, as determined by the
size distribution of the feed material,
the sample is subjected to tumbling
in a drum of specified dimensions for
100 revolutions, the size distribution
after tumbling is then determined, and
the M10 and M40 number reported.
To determine the hot strength of
the coke, we use the CRI & CSR
test: A portion of coke within a very
specific size range reacts at 1000°C
with CO₂ gas. The mass loss during
this period is the coke reactivity index
(CRI). The residue is then tumbled
in the CSR tumbler and the size
distribution determined. The oversize
after reaction is the coke strength
after reaction (CSR). These tests
determine whether the coke will be
able to carry the load under pressure
from the steel or iron, but also if it
would be reactive enough for the
reduction of the ore,” says Carstens.
The fields of coal
Most of the samples in the laboratory
are used to test for coking coal
properties. According to Hefer, a