Chambishi Metals Opts for Atomisation 

The old smelter slag dumps at Chambishi near Kitwe, Zambia, contain valuable amounts of cobalt and copper. Anglovaal Mining (AVMIN) will recover the metal values using a pyrometallurgical process followed by hydro metallurgical separation of the cobalt and copper. The latter requires the metal to be supplied as a fine powder which can be quickly and easily dissolved for processing.


A CAD design rendering of the 500 kg/min atomiser and 145 kg/min pig caster to be installed at Chambishi Metals PLC, Zambia.

Atomisation AVMIN will use a DC arc furnace and a special control of the slag conditions to produce n iron-based melt with a sulphur content in the range of 1 to6 % and 10 to 20 % of cobalt and copper. An atomisation rather than a milling process will be used to reduce the melt to particles with a median size of about 0microns, as this alloy with it slow sulphur content cannot easily be milled to a fine enough powder.

BATEMAN, in association with Atomising Systems Limited (ASL) of Sheffield, UK, has designed a large capacity high-pressure water atomiser, rated at 30 t/h (500 kg/min) of molten alloy, to produce a slurry in water which can be pumped directly to the hydrometallurgical circuit. This will be achieved by pouring the molten alloy into high pressure water jets using a programmable logic controlled (PLC)hydraulic-ladle tilter of 15tonne capacity.

Atomisation has been widely used to process precious metal-bearing scrap, but this is believed to be the first time that it has been used on a large scale as the interface between the pyro- and hydrometallurgical circuits in a primary smelting operation. It is well suited to process mattes with a low surface tension and requiring lower pressures, and thus less energy and capital cost, than pure metals. Also, when the sulphur content drops below 10 %, mattes can no longer be milled easily and atomisation becomes more attractive.

With atomisation, outputs of over1tonne/min and high productivities in the range of 100 to 1000 t/yr are entirely practical. There are also far fewer wearing parts than in ball mills.

Ancillary post-taphole equipment
Besides the atomising plant, AVMIN has ordered other equipment from BATEMAN needed for the post-taphole processes, including a pig-casting machine and metal and slag-taphole clay guns and drills.

BATEMAN, in association with Ingotech, UK, will engineer and supply an integrated pig caster that will also be fed via the PLC ladle tilter which will be available in case of emergencies.

BATEMAN, in association with Paul Wurth of Luxembourg, has also designed and supplied fully automated clay guns and drills mounted on integrated carriages travelling on overhead suspended rails. They can serve multiple tapholes for slag and metal-alloy tapping.

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