The separator in which the diamonds are separated from the grease. The diamonds are retrieved through the three tapping valves on the left.

The coarse grease belt, moving from left to right. The diamond concentrate is dropped onto the belt at the far left side of the picture. Because of their surface properties, the diamonds adhere to the surface of the grease while the waste material is washed off the angled belt. The grease layer with the diamonds is scraped off the belt after it has passed over the end pulley and is collected in the separator.

Trial erection at the factory of HC van Wyk's grease-recovery plant. The plant is built into seven special (Hi-Cube) containers.

Grease-belt system for HC van Wyk's diamond-recovery plant

A fully automated, hands-off final diamond-recovery plant comprising two grease belts has been installed for HC van Wyk Diamante at Wouterspan, about 180 km from Kimberley in the Northern Cape, RSA. A fines grease belt treats concentrate less than 12 mm in size and a coarse grease belt concentrate between 12 and 30 mm in size.

Grease belts are particularly suited for the efficient recovery of smaller diamonds and are recommended for diamonds with low luminescence (i.e. Type II diamonds). Compared with X-ray recovery, grease belts handle higher tonnages of concentrates at lower capital and operating costs, albeit with lower yields. The level of operator skill required is also lower as there is no need for maintenance by highly skilled technicians and electricians.

Specially formulated grease is applied to the moving belts and well-scrubbed diamond concentrate is dropped onto the grease belts. The waste material is washed off the belt, while the diamonds adhere to the grease. The diamonds and the layer of grease are scraped off the moving belt and dropped into hot water in the separator tank. The grease melts and floats on top of the water, while the diamonds in the grease are released and sink to the bottom of the water in the tank and are collected at the tapping valves.

The molten grease floats over a weir in the separator tank into another vessel where any remaining waste is removed from the molten grease. The cleaned grease is then transferred by air pump to a heat exchanger which chills the grease to a temperature at which it has a paste-like consistency so it can be applied to the moving belt again.

The recovery plant is built into five containers, which were transported by road to site after the trial assembly and testing of the plant in the factory near Pretoria, RSA. Two additional containers were also supplied to accommodate belts to be added in the future.

The containers are thermally insulated to permit the working conditions inside the containers to be maintained at a comfortable level, despite the extreme fluctuations of the outside temperatures, ranging from freezing during the nights to well above 40°C during the day.

The order for this lump-sum turnkey project was received in September 2005 and the plant was commissioned successfully in March 2006.

For further details, please contact either Robert Abate, General Manager, Modular Plants, or Neels van Niekerk, Project Manager,
on +27-11-899-9111 or email modular@BatemanEngineering.com.

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