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MEI Online: Plant Operation News: Africa: May 23rd 2006


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:: Mintek Supplies Pilot Plant to Optimise Nickel Processing

On request from Nkomati, Mintek has supplied a pilot flotation plant to LionOre's Tati Nickel Mine Activox® Demonstration plant near Francistown in Botswana to demonstrate at pilot scale the operability of the process to refloat an Activox leach residue for the recovery of platinum group metals (PGMs) into a concentrate that will be toll smelted.

High grade nickel concentrate from African Rainbow Minerals (ARM) and LionOre's Nkomati Nickel Mine in Mpumalanga, which has a similar orebody in geology to the Phoenix nickel mine, was recently sent to Tati for testing and processing, using LionOre's proprietory Activox® leaching technology to optimise the processing of concentrate.

To demonstrate the refloat of the Activox® residue Mintek mobilised, installed and commissioned the plant on a turnkey basis and also supplied two metallurgists to assist in the installation and operation of the pilot flotation plant to demonstrate the process.

"The main aim of the project was to optimise operating conditions to produce sufficient "on grade"concentrate that would be used for downstream testwork and commercial purposes," said Mike Bryson, head of Mintek's Mineral Processing Flotation Group

Activox® is a medium-temperature, medium pressure process for the oxidation of sulfide minerals, which uses a combination of fine grinding followed by pressure oxidation under mild conditions. This non-smelting hydro metallurgical process, which is claimed to be technically very sound, has been successfully implemented at Tati and is said to hold great promise for the future.

Built at a total cost of US$11.5-million and with a treatment capacity of 8 t/day of concentrate, the Tati plant is capable of producing about 300 kg/day of nickel cathode and about 150kg/day of copper. In the Activox® process at Tati ultra fine grinding of the ore is followed by a low pressure, low temperature oxidative leach (1 000 kPa at 110 degrees C), to selectively dissolve the base metals from the sulfide concentrate. Nickel and copper are then separated, purified and recovered as metallic cathode via standard solvent extraction, electro-winning (SX-EW) technology, while cobalt is recovered as a carbonate by-product.

The Nkomati mine produces between 4 500 t and 5 000 t of nickel annually. By-products include 2800 t of copper, 22 000 oz of palladium and 7 000 oz of platinum. The mine's high grade nickel concentrate is sent to toll smelting and refining off site. Some of it is sent to BCL in Botswana and Impala in Springs for smelting, while a portion is shipped to Canada and Norway for refining.




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