Thursday, 8 September 2011

Flotation plant control

The Applications and Plant Practice Symposium at Flotation ’11 has a number of papers relating to the control of flotation circuits, using machine vision, electrical resistance tomography and acoustic emissions.

One of the conference delegates, Trevor Yeomans, of Silver Standard Resources, Canada, notes, in LinkedIn’s Froth Flotation group, that such control techniques, and traditional methods such as froth depth and aeration rate, are typically used on rougher-scavenger circuits and asks would it not be more effective in cleaner circuit control, where the flowrates are more variable in the short term and the economic value of producing a more consistent concentrate quality is likely to be higher than increasing rougher recovery.

Trevor’s question has lead to some interesting comments. Jorge Ganoza of Bear Creek Mining Company, Peru, argues that the role of the cleaner circuit is to reject gangue minerals and liberate valuable minerals to produce marketable concentrates. The quality of the rougher concentrate has an impact on the cleaner circuit, as a high grade rougher concentrate facilitates the operation of the cleaners

Francois du Plessis, of Blue Cube Systems, South Africa, who will also be at the conference in November, states that stabilising the primary rougher concentrate grade should be a first priority, as grade stability is improved to the cleaners, which in turn gives a more consistent product grade quality, and maximises overall recovery. Although cleaner banks determine the product quality, they cannot recover what has been lost through primary flotation. However rapid process control is already being used at various sulphide flotation plants on the final concentrate banks, to prevent incurring smelter penalties.

The latest issue of International Journal of Mineral Processing (Volume 100 Nos. 3-4, 2011) contains a paper by Shean and Cilliers, which reviews froth flotation control.

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