Flotation at Impala Platinum's UG2 plant 

BATEMAN has supplied and commissioned 21 flotation cells to Impala Platinum Limited for the UG2 Ore Separation Project. The flotation circuit is successfully treating a combination of high- and low-grade UG2 ore to separate a platinum bearing concentrate from the gangue material containing chromite.

Although cost was the main deciding factor, the BATEMAN flotation cells were selected by Impala after taking into consideration the design features of the cells, which promised to overcome difficulties which had been encountered previously on other UG2-ore flotation circuits.

The circuit consists of four high-grade rougher cells with a 50 m 3 capacity, seven low-grade rougher cells (50 m 3 ), six low-grade cleaner cells (20 m 3 ) and four low-grade recleaner cells (10 m 3 ). BATEMAN supplied all the control equipment for the flotation circuits, including the level- and air-control instrumentation.

As with all BATEMAN flotation circuits, the cells as well as the feed and transition arrangements between adjacent cells were custom designed for this application. The first cell in each flotation bank has an integral feedbox, semi-circular in shape, which minimises the delivery distance into the cell. The feedboxes are sloped to ensure a continuous flow of material and a slotted inlet into the cell eliminates any chance of the inlet becoming blocked.

The level of the slurry in a cell is controlled by means of two actuated dart valves positioned internally to ensure that the area around the cell outlet is kept clear, thereby reducing the possibility of chokes. The discharge from the dart valves is through semi-circular dart boxes located under the cell. These boxes are sloped towards the outlet to maintain a sufficient flow into the following cell.

The design also permits efficient pumping through the rotor-stator combination without causing turbulence at the pulp-froth interface. Additionally, the mechanisms are able to suspend the chromite particles in a fluidised bed to ensure a satisfactory flow through the cell.

Target-plate and float-type level assemblies were also supplied, together with an ultrasonic-level detector for integration with the dart valve actuators. Flow meters and butterfly valves were fitted to control the air supply into the cells and four Roots-type blowers provide the air supply to the flotation circuit.

During commissioning, all of the cells were started up initially with water and air and then slurry was introduced. The circuit operated from the start without any problems. Once in operation, the level and air control was fine tuned in order to ensure optimum operation of the complete flotation circuit.

This project commenced in May 2000 and was completed in May 2001. Once steady state conditions were established, is was possible to commence maximising the performance of the circuit by optimising the control of the levels in the cells, the reagent additions and the air supply. Optimisation work is ongoing.

Please contact Craig Gilbert, Manager, Processing Technologies, on +27-11-201-2300 or email specialised@batemanengineering.com for more information.

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