The Knelson Concentrator: Application and Operation at Rosebery
S. Poulter, C. Fitzmaurice, G. Steward
Presented at 5th Mill Operators Conf. Oct. 1994 Roxby Downs, Australia
October 22nd, 1998
Rosebery has a long history as a base metals sulphide mine. Copper, lead and zinc concentrates are produced for sale. Silver values have always been high in the lead concentrate, while gold has historically been seen as a bonus in both the copper and lead concentrates.
During the late 1980s, a concerted effort was made to improve the recovery of gold liberated in the grinding circuit by the installation of a conventional gravity circuit. Spirals and tables were employed in this circuit which treated a bleed stream from the tertiary cyclone underflow. The conventional gravity circuit operated successfully for a number of years. The circuit required significant operator attention, adjusting cutters, unblocking and cleaning feed splitters, in order to produce a quality product. Recovery of gold to dore via the gravity plant was on average less than ten per cent of the gold in feed. The unit recovery of the gravity plant was found to be very poor.
It had now become clear that to improve gold recovery prior to flotation we must target the primary cyclone underflow stream. This stream was known to contain particulate free gold. The Knelson Concentrator was chosen to recover this gold for a number of reasons:
- The Knelson Concentrator can accept feed and recover gold across the full size range from two millimeter to two microns.
- The Knelson Concentrator is not reliant on operator attention to achieve results.
- The Knelson Concentrator was small and compact, and could be installed easily and relatively cheaply into the primary grinding circuit.
A Knelson Concentrator was installed to recover liberated gold from the grinding circuit. The successful operation not only lifted the gold recovery but also reduced the operating requirements of this section of plant. The manual discharging Knelson is attended to for one hour three times per day, while the recovery of gold to dore is increased from 15 per cent to 30 per cent. Consistent performance from the Knelson enabled the conventional gravity plant to be decommissioned during February 1993.
Rosebery must now be considered a zinc/gold mine, with 65 per cent income generated from zinc and 14 per cent generated from gold.
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