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MEI Online: Commodities: Non-Metallic Ores: Diamond: Latest News: November 4th 2004


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:: Roller-supported Scrubbers for Processing Diamondiferous Materials

Bateman roller-supported scrubbers offer a cost-effective solution for production- or exploration-scale operations and in land- or marine-based processing facilities, where they are used to break down or wash off clay and other contaminants on the hard or crystalline minerals and rock, prior to processing to recover the diamonds.

The scrubbing action may also be used to break up mineral conglomerates by loosening the bonds between large particles resulting from salt precipitates and clay.

The capital cost of Bateman roller-supported scrubbers is as low as 50 % of traditional trunion-supported scrubbers because their horizontally rotating cylindrical shells are mounted on and driven by polyurethane-covered rollers. Besides capital cost, this concept significantly reduces the running costs, as the in- and output mechanisms are simple and the replacement of moving parts can be done within a few hours. Maintenance costs are thus low and confined to regular lubrication checks and occasional liner replacements.

Because they are easy to manufacture, the lead times are half of that for conventional scrubbers. In addition they can be installed within two to three days, due to the bolted assembly base frames.

The units can be mounted on a concrete or steel structure. The polyurethane-covered rollers, which ensure quiet, smooth operation, are coupled to either two or four electro-mechanical drives at the corners of the scrubber's base frame.

The internal surfaces of the shells have replaceable rubber linings fitted with lifters which cause the load to tumble when the cylinders rotate, dislodging contaminants which are carried away in the water overflow at the outlets. For each application, the liners and the size and arrangement of the openings in the feed and discharge endplates are specially designed to contain the appropriate amount of liquid within the shell. They are thus easy to fill and discharge. The discharge end can comprise either a bell-mouthed cone or a single or double trommel screen.

The reversible rotation and symmetrical design maximises liner life. The speed of rotation of the shells can be easily varied. Generally it is low, between 50 % and 60 % of the critical speed, but can be adjusted to improve agitation if the clay adheres strongly and is water resistant.

With all-steel construction and no cast components, the equipment is rugged and downtimes are short. The long-term rugged performance is maximised by utilising finite-element analysis during design to ensure the scrubber's charge and mass are adequately supported to minimise shell deflection and bending.

Correct alignment of the rollers is crucial to ensure trouble-free operation. All Bateman roller-supported scrubbers are trial erected and tested at the factory before dispatch to ensure correct operation.

During the past decade, Bateman has installed nearly 20 units on land-based or marine diamond processing plants, where they are used as scrubbers and ball mills. They process between 25 t/h and 700 t/h of dry material, with shell diameters from 0,8 m to 3,66 m, lengths from 1,5 m to 7,1 m and installed powers ranging from 22 kW to 440 kW.




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