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:: Hillendale Cyclones
The use of cyclones to deslime the feed at the Hillendale Plant at Richards Bay has resulted in an increase in heavy minerals recoveries. This obviously had a positive financial implication for the plant.
Niel Lourens, technical manager for cyclones at Multotec Process Equipment, says that one of the main difficulties for Hillendale is that the sand being mined has a very high and varying slimes content, and this has an adverse affect on the efficiency of the spirals plant. "Excessive slimes entering the spiral circuit can cause a shift in the separation efficiency of the spirals. The separation densities also become difficult to control resulting in incorrect density cutpoints and an additional loss of valuable minerals," Lourens explains. "We were tasked with removing as much slimes as possible without losing any valuable mineral."
Extensive test work was undertaken on site by Multotec Process Equipment in order to find the most effective and efficient solution.
Lourens explains that the most appropriate solution for this application necessitated the implementation of a process whereby the fresh feed coming in to the plant was rerouted. Instead of going straight to the spirals plant the fresh feed is fed through the cyclones for upfront de-sliming. A holding tank on the underflow of the cyclones steadies the feed to the spiral plant.
A specific challenge was the development, by Multotec in conjunction with Ticor, of a control strategy to handle the varying slime content in the feed.
Careful analysis of the test results indicated a substantial increase in heavy mineral recoveries by de-sliming before the separation process. The prospect of better heavy mineral recoveries convinced the plant to implement this innovative solution.
The four clusters, with eight cyclones per cluster, were installed and commissioned some twelve months ago, and have been operating successfully since then. The cyclones, from the Multotec PC range are standard rubber lined units.
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