Mine excursion
having reached five million hours without a
lost time injury (LTI).
Looking ahead, Bushveld Minerals CEO
Fortune Mojapelo outlined plans to increase
the production capacity at Vametco. He
noted that the target is to increase the group’s
production by 10 000mtV in the medium
term, highlighting that its resource base was
continually growing through the combined
resources in the group.
The company has now set its sights on
growing its processing infrastructure, which
would enable it to process twice as much as
the current production levels. The crushing
and milling circuit has already been expanded
to process more ore. Developments on the
processing plant will give it the capacity to
process additional ore from both Vametco
and the Brits project.
Processing steps
oxide (MVO) for conversion. The vanadium
depleted solution is pumped to the sulphate
recovery plant.
Once AMV is reduced to MVO, the
vanadium falls in the +3-oxidation state. The
MVO is drummed and sealed when cool to
prevent re-oxidation. The product is black in
colour and has variations of brown. A bright
blue colour indicates that the product had
been exposed to oxygen before being cooled
off sufficiently. The MVO then becomes the
feedstock for the Nitrovan electrolytes.
More than a vanadium mine
Currently, Vametco only produces Nitrovan,
which is used to produce high-strength low-
alloy steel. “Having been an alloying element,
strengthening and toughening steel through
vanadium and nitrogen precipitation, you
end up getting the same yield strengths for
less vanadium input,” Steinberg explained.
The Nitrovan is a vanadium-nitrogen product
used to strengthen steel. The strengthening
mechanism allows steelmakers to use less
vanadium in high-strength low-alloy steels
and reduce vanadium costs by up to 40%.
“We make two Nitrovan products: a
Nitrovan 12® and a Nitrovan 16®,” Steinberg
explained. The difference between the two
is the nitrogen and carbon content in each.
With Nitrovan 12, there is 10–14% nitrogen
and a maximum of 10% carbon. Nitrovan 16
contains 14–19% nitrogen and no more than
6% carbon. Both have 76–81% of vanadium
and 0.15% aluminium.
After drilling and blasting, the ROM ore
goes through a three-stage crushing and
milling circuit. Through a grizzly screen,
the ore is separated to an oversize within
the 40mm and 150m range. Ore from the
150mm stockpile gets fed to the secondary
crusher.
In the milling section, the 10mm ore is
pulverised in ball mills and then fed to the
magnetic separators where the magnetic
portion is separated from the gangue. The
first concentrate from the magnetic separators
are fed to the secondary mills where it is
further grinded, then finally separated in
a magnetic separator. The concentrated
magnetite is fed to the kiln sections, where
the slimes and gauge will be pumped to the
tailings slimes dam. The water used in this
process is recovered and recycled in the plant.
“We utilise the well-established roast
leach process to extract the vanadium, at
about 1150°C to make it soluble in water,”
Steinberg noted. It then becomes possible to
separate the vanadium from the magnetite.
The solids in the scrubber liquor are settled
in a thickener, dewatered over a belt filter,
and returned to the kiln feed. The thickener
overflow is pumped to the line scrubber dams
for further settling before being reused in the
scrubbing circuit.
The kiln product is water-leached. The
solids are wet milled and washed in a
counter-current process over a large belt filter
and the magnetite tailings are disposed of in
a tailings dump. Aluminium sulphate and a
flocculent are used to desilicate and clarify
product liquor. The vanadium-bearing liquor
is pH adjusted with sulphuric oxide acid
before being pumped to the precipitation
plant. Some ammonium metavanadate
(AMV) sludge is re-dissolved in Vametco’s
plant using caustic soda.
Vanadium in the pregnant solution is
precipitated with ammonium sulphite to
form AMV. This is then dried in a rotary
calciner at a temperature that will retain the
ammonium. In the AMV, the vanadium is
in the +5-oxidation state. The dried AMV is
then forwarded to the modified vanadium
Vametco works with contractors from surrounding communities.
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APRIL 2019 MINING MIRROR [17]