PLC controlled ladle tilter.

Converter-slag granulation plant for Impala Platinum

A plant to granulate 1 tonne/min of copper-nickel converter slag has been supplied to Impala Platinum Limited, Rustenburg, RSA. The plant, designed by BATEMAN, includes all the equipment required to handle the molten slag and granulate and dispose of it. The plant comprises a ladle tilter, laundergranulation system, cooling tower and dewatering ponds. Civil construction was undertaken by Bafokeng-Bateman.

The granulation of a slag in water is the proven way to produce a product for retreatment or disposal in the most economical, safe and environmentally friendly manner. This means that the granules must be large enough not to become an environmental hazard, yet small enough to be conveyed or trucked to the downstream processes. The BATEMAN-designed system not only produces the required product, but ensures the safe and effective granulation of a slag material known to react in a volatile way during granulation with water.

The process

Molten slag is tapped into ladles which are delivered by an overhead crane to the ladle tilter equipped with a PLC (programmable logic controller) system. The tilted ladle feeds the molten slag down a hot runner at a constant rate of 1 tonne/min and discharges it into jets of water in the granulation basin through a specially configured launder.

The granulated slag and granulation water are then transported down the launder to a dewatering pond where the slag settles out of the water. Between granulations, batches of the slag are removed by an overhead mechanical grab and stored in a dewatering bin from where it is loaded into trucks.

The cooling circuit comprises a 550 m³ dewatering pond and an 850 m³ cooling-tower pond, a suction chamber and a ranulation-water suction chamber. The modular evaporative-cooling tower cools the pond to the required temperature between granulation cycles and is extremely economical.

Plant features

Molten slag produced during converter processes involving coppernickel mattes has been found in many instances to be as reactive as the matte when brought into contact with water during subsequent granulation. The design of the system installed for Impala Platinum therefore has many safety features. The water-to-matte ratio and water pressure and temperature are accurately controlled. The flow of molten slag is held constant and the configuration of the water jet is maintained to ensure proper agitation of the granulation water. This effectively evacuates the hydrogen generated by the process and prevents sudden outbursts of energy.

Forty percent of the granulated slag produced is between 0,6 mm to 1,0 mm, an appropriate size fraction for reprocessing.

A closed system is used to mimimise the effluent from the plant and a minimum number of mechanical devices ensures minimal maintenance and operator involvement.

The design of the cooling tower takes into account the possibility of the formation of airborne fibrous strands (Angel’s hair) during the granulation of this type of slag, which could block the cooling towers. The cooling tower was designed jointly by BATEMAN and Evapco.

For more information, please contact

Dave Norval,
General Manager, Post Taphole Services, on +27-11-201-2300 or email posttaphole@batemanengineering.com

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