DRA was the EPCM contractor for the 12 million tonne per annum (mtpa) DMS project at Tati Nickel’s existing Phoenix mine, located 40 km northeast of Francistown in Botswana. The US$151m project began in August 2006 and was completed in December 2008, with the commissioning of the new primary gyratory crusher.
The new plant is sited within the existing concentrator complex and consists of a primary gyratory crusher, secondary and tertiary crushing and screening circuits, and associated materials handling systems, consisting of 42 conveyors. Over 950 tonnes of conveyor structural steel was designed and fabricated in India.
The crushed material, -25 mm in size, feeds the DMS section, built in four parallel modules, with a combined capacity of 1,600 tonnes an hour. By removal of the waste portion, a higher nickel grade product is fed into the existing milling circuit, thereby increasing the nickel concentrate volume processed through the existing concentrate plant.
Production at the Phoenix mine commenced in 1995 at 1.2 mtpa, using dry magnetic separation concentration due to lack of sufficient water. In 2000 a capital project was undertaken to increase tonnage and switch to the much more efficient conventional mill/flotation process. The 3.6 mtpa concentrator was commissioned in 2002. This included the construction of a 43 km water line from Shashe dam as well as an increased 20 MW power supply from Francistown. The concentrates are trucked 200 kilometres to the smelter at Selibe Pikwe.
The Phoenix deposit consists of high grade lenses of massive nickel/copper sulphides surrounded by disseminated low grade ore. It requires very selective mining and blending to avoid wide fluctuations in the feed grade to the concentrator. The new DMS plant contributes to grade stability and allows lower grades to be profitably mined.