The new greenfields smelter, pelletising and sintering plant for
SA Chrome and Alloys Limited has been commissioned as a lump-sum turnkey
project by BATEMAN at Boshoek, some 20 km north of Rustenburg, North
West Province, RSA. The first metal was tapped only 15 months from the
receipt of the order.
The plant has a design capacity of 235 000 t/yr of
saleable charge ferrochrome from a blended feed of lumpy chromite and
chrome concentrate. It consists of two 54 MVA closed submerged-arc furnaces
and a pelletising and sintering plant to process 520 000 t/yr of material.
The closed-furnace technology, a new but proven BATEMAN design featuring
Outokumpu pre-heating, is environmentally friendly. Smelting of chromite
during the production of ferrochrome can lead to the production of chromium
VI, which is highly toxic. However, the closed furnaces preclude the
ingress of air (oxygen) into the hot interiors, so that chromium VI
cannot be formed.
Outokumpu’s sintered-pellet smelting process
is proven technology. This process route improves chromium recoveries
by at least 15 % and consumes 25 % less energy than conventional open
or semi-closed furnaces, ensuring that SA Chrome will be the lowest-cost
chromium producer. The lower energy consumption also reduces the ecological
impact associated with fossil-fuel electrical energy generation.
Two ore types are processed in the plant, viz. a high-grade
LG6 and a lower-grade UG2 ore. The LG6 ore is brought by road from SA
Chrome’s Horizon mine, located some 40 km to the northwest of the
smelter. The UG2 concentrate, a discard product from platinum mining,
is purchased in terms of a 20-year agreement from Impala Platinum’s
nearby UG2 concentrator.
A blend of about 40 % LG6 ore and 60 % UG2 concentrate
is supplied to the furnaces to ensure a chrome-alloy product with a
minimum grade of about 51 %. This blend is milled with coke, filtered
to remove excess water, mixed with bentonite and pelletised. Green pellets
between 10 and 15 mm pass through drying, preheating, sintering and
cooling zones in the sintering furnace to ensure that they contain iron
in the ferric form which is more easily reduced, with a porous structure
and high-temperature strength to enhance the rate and uniformity of
reduction in the furnaces.
Stockpiled sintered pellets are mixed with other raw
materials and conveyed to the preheater above the furnace, where they
are heated to 600 °C by burning scrubbed gases from the furnace.
The use of preheated pellets as feed to the furnaces reduces power consumption
as well as reducing electrode consumption and maintenance, while increasing
the furnace capacity and ensuring its smooth operation.
BATEMAN also prepared the environmental impact study
for the project, was instrumental in preparing the bankable feasibility
study and facilitated the off-take agreement for the ferrochrome product.
These ensured that SA Chrome was able to raise the necessary equity
and loan finance for the project and arrange a five-year off-take agreement
with Thyssen Krupp in Germany for this ferrochrome output.
For more information, please contact George Farmer,
General Manager, Bateman Ferrous, on +27-11-899-2531 or email ferroalloys@batemanengineering.com
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