SA Ferrochrome exceeds criteria
in performance tests
The newly installed furnaces and sintering plant at SA Ferrochrome
exceeded performance and design criteria in performance tests recently
completed by BATEMAN. In addition, following commissioning, monthly
targets were increased constantly.
This new greenfields installation for SA Ferrochrome
(Pty) Ltd was commissioned by BATEMAN as a lump-sum turnkey project
at Boshoek, some 20 km north of Rustenburg, North West Province, RSA,
towards the end of 2002. The plant has a design capacity of 235 000
t/yr of saleable charge chrome 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 chromite pellets.
The tests on the furnaces were conducted together
with Outokumpu during July 2003 and criteria in terms of both chrome
recovery and power consumption were exceeded during the seven-day trial.
Chromium recoveries in excess of 84 % were achieved on both furnaces
and the energy consumption was below 3 150 kW h/t. SA Ferrochrome is
currently achieving a constant throughput on both furnaces on an average
load of 46 MW each.
The pelletising and sintering plant from Outokumpu
also reached full production in January 2003, only four months after
commissioning, and was performance tested over a 72-hour period in April
2003. The plant reached a throughput of 85 t/h wet feed to the sinter
machine, thus exceeding the design capacity of 520 000 t/yr. Performance
criteria in terms of both plant throughput and quality of pellets were
achieved during the test period.
Two ore types are processed in the plant, 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 north west of
the smelter. The UG2 concentrate, a discard product from platinum mining,
is purchased in terms of a long-term 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 and was instrumental in preparing the bankable feasibility
study.
For further information, please contact Jurgens
van Tonder, General Manager – AC Furnaces, on +27-11-899-2363
or
Email acfurnaces@batemanengineering.com
Other articles on this project for SA Chrome can
be found in
Globe Nos 21, 29 and 31.
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