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DC-smelting study on nickel ore from Shevchenko, Kazakhstan

BATEMAN was contracted by Mintek to provide the engineering input to a prefeasibility
study for Oriel Resources plc on a ferronickel-process plant for the Shevchenko
project in Kazakhstan. The study was completed successfully.

BATEMAN handled the engineering design and costing of the process plant and became involved
in the project because of its previous experience on similar DC-arc smelting studies.

The processing tests, conducted by Mintek's Pyrometallurgical Division, were positive. Mintek
dried, calcined and smelted 6 t of the Shevchenko nickel ore in its 200 kVA DC-arc furnace at a
temperature of about 1 600°C at an average feed rate of 65 kg/h. Optimal conditions were achieved
when adding 4,5 % coal and 9 % magnesite flux to the furnace feed and yielded a crude ferronickel
product with in excess of 20% nickel with recoveries conservatively estimated at 89%.

As a result, Oriel Resources, which is listed on the London Stock Exchange, is considering a
definitive feasibility study on the project.

Smelting tests on Shevchenko nickel ore in Mintek's DC-arc furnace.

Ferrometals' Furnace 4 upgraded to 60 MVA

BATEMAN has completed an upgrade of Ferrometals' Furnace 4 (F4) in Witbank, RSA, for
Newsam Pty Ltd (a joint venture between Samancor and Poschrome) to increase the
furnace's production capacity from 100 000 t/yr of ferrochrome to 125 000 t/yr.

The project site work was undertaken during a shutdown of the plant from 30 June to 4 September
2003 and was finished four days ahead of schedule.

The upgrade and rebuild of F4 follows a similar upgrade of Furnace 5 at the same site during 2002
and involved the existing 48 MVA furnace being upgraded to a 60 MVA closed submerged arc
furnace. The nominal operating power is expected to be about 48-50 MW, with capability to
operate at a maximum of 52-55 MW.

The shutdown started with the demolition of the furnace (roof, shell and feed chutes) and removal
of the furnace burden. Civil work on the furnace supports started when the area had been cleared
and upgrade work commenced on the raw materials handling system at the same time.

The two closed furnaces at Ferrometals' site in Witbank, F4 and F5, share a common feed system.
The raw materials are fed to the furnaces' respective proportioning bunkers via a fines screen and
flopper gate system onto a series of conveyors. The raw material handling system was upgraded
by rearranging existing feeders and installing new vibrating feeders to increase feed capacity by 25 %.

After proportioning, an incline conveyor raises the material to the Outokumpu pre-heater. The feed
mixture is heated by furnace off-gas, mainly carbon monoxide (CO), before being choke fed into the
furnace via nine refractory lined chutes, which were also replaced during the shutdown.

The feed material is then smelted in the furnace, the main reaction being the reduction of chromite,
during which CO is generated. The furnace off-gas is removed by extractor fans and passes through
wet scrubbers for cleaning and cooling. The pre-heater consumes the CO gas for pre-heating and the
remainder of the gas is available in the network or it can be flared. In order to control the furnace
pressure, two new CO fans were installed to cope with the increased volumes of CO being generated
in the furnace. Knock-out separators were installed after the furnace venturi scrubbers to remove
remaining solid particles and moisture in the gas stream.

The furnace was replaced by a BATEMAN-designed furnace and roof. The shell diameter was
increased from 13 m to 13,7 m, incorporating a UCAR / BATEMAN Chill KoteTM lining. This
lining consists of conductive refractory on the cold face and insulating refractory on the hot face
in the metal and slag zone. This effectively increased the crucible diameter by more than 2 m.

Three 21 MVA transformers replaced the three 16 MVA transformers. The increased furnace power
input also necessitated an increase of the electrode pitch circle diameter (PCD).

The Chill KoteTM / freeze layer on the hot face of the refractory relies on adequate and continuous
cooling to ensure that the hot face temperature stays below the solidus temperature of the metal
and slag. A furnace refractory lining monitoring system was developed by Bateman and installed
to monitor refractory wear and Chill KoteTM / freeze thickness. Shell film cooling water is
collected in a tank from where it is redistributed to the header and tundish of the furnace shell.
A side-stream filter unit removes solids in the water.

Roof cooling is accomplished by a closed-circuit cooling-water system and dedicated cooling towers.

A single, main taphole was provided together with an emergency taphole above the main taphole at
an angle from the centre line, to be used for upset conditions.

Commissioning was a continuous process, signing off systems as they were completed by the
construction teams. Start-up was accomplished with no significant mechanical,
electrical or instrumentation malfunctions.

Pair of off-gas stacks from Furnace 4 and 5.

Inside the furnace during start-up.

Installation of one of the new 21 MVA transformers

 

 

 

 

 

 

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.

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