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MEI Online: Plant Operation News: Africa: January 27th 2004


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:: Tati Nickel

Tati Nickel ore is known to be within the top ten percent of the most abrasive ores in the world, and equipment and products used in this environment need to be capable of withstanding the harsh operating conditions.

It is significant then that Multotec products are being used in a number of applications at Lion Ore’s Tati Nickel mine, and according to Spike Taylor, of Multotec, most were selected for their cost effectiveness and wear characteristics.

Commenting on the process itself, Taylor says that following an evaluation of the ore type at Lion Ore’s Tati Nickel it was determined that the current fashion of using a SAG mill/ball mill would not have been suitable because of the high Bond Work Index. This resulted in the plant being designed as a conventional crushing and screening plant followed by a primary ball mill and secondary ball mill.

Multotec Polypunch panels were selected for use on the Multislope screens at Tati Nickel, and Taylor explains that these screening panels were developed specifically for abrasive applications where high impact and high sliding abrasion is present.

The laser cut perforated Polypunch panels incorporate a VRN 500 screening surface, and the rigid and strong nature of the steel makes it possible to have a strong panel with sufficient open area to provide required capacity. In addition to this increased open area, the low friction of the steel plate allows material to flow more easily down the screen increasing efficiencies and reducing wear.

Multotec Rubber provided thick bolt-down rubber impact panels for the feed area of the screen to ensure a good life at the impact point. Heavy-duty modular cast polyurethane panels were used for the bottom bed with slots for the feed slopes. This combination of materials construction and aperture shapes and sizes results in a hybrid screening surface customised for life and efficiency.

Taylor explains that the slots at the feed slope allow contact time for the particles, and the square apertures on the discharge slope for an accurate cut point. To date the panels have been achieving a good life in this application.

The two tertiary Multislope screens were initially installed using injection moulded panels, however the severity of the application resulted in these panels being changed to cast polyurethane panels with skid bars. This change, according to Taylor, has increased the life five-fold.

Two trommel screens fitted with Multotec Manufacturing’s well proven modular panel system were supplied. Taylor says that while there were initial mass balance problems due to excessive scats, this has been solved by changing the aperture size and using the proven staggered scroll layout on the primary ball mill.

The primary ball mill is in a closed circuit with three vibrating screens equipped with Multotec injection moulded panels. In addition to changing the aperture size to achieve the correct mass balance, these panels have been fitted with deflectors to prevent tram lining of particles down the solid borders of the panels.

Multotec Process Equipment supplied two clusters of cyclones to Tati Nickel. The secondary ball mill is in closed a circuit with a cluster of loose rubber liner cyclones where “tell-tale” weep holes provide an indication of when the rubber liners need changing. The other cluster of cyclones has been installed on the flotation circuit. This simple modification to the cyclone design has provided both maintenance and process personnel with a simple, yet cost effective means of reducing maintenance costs without compromising cyclone efficiency.

The provision of accurate metallurgical data for the feed to the milling section has been facilitated through the installation of a Multotec cross-belt hammer sampler. Slurry sampling systems were also installed in the milling and flotation sections to provide representative sampling and enable accurate mineral balances.

Both Multotec Rubber and Multotec Wear Linings are working together to solve the wear problems on this plant. Rubber wear plates have been installed on the primary section where the rubber can absorb the impact of the large particles.

In addition to this, Multotec low friction loading points have been used under the primary stock pile discharge areas to protect the conveyor and provide ease of maintenance. Multotec loading points combine the use of low friction polyethylene with the shock absorbing qualities of rubber in an engineered system that provides an impact reducing flat surface.

Multotec Wear Linings is providing ceramic linings for the milling section to provide a long life due to the extremely abrasive wear conditions that are being experienced. The company conducted a wear audit which focuses on identifying problem areas and providing solution not only using superior wear resistant materials, but redesigning the chutes, transfer points or sumps to eliminate excessive wear, spillage or hang ups.




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