Reduced flocculant consumption and improved operational performance are the results of a thickener upgrade at a large Australian gold mine. A leach feed thickener was creating a bottleneck in a gold mine in Western Australia. The installed thickener was a preinstalled ‘off-the-shelf’ product, neither supplied nor installed by FLSmidth. As the on-site maintenance contractor, the client asked FLSmidth’s team of specialists to assess the performance and offer a solution to improve productivity and overall performance. As a result, FLSmidth’s engineers identified several improvements to the thickener’s control set-up.
“The customer realised their feed system was under-sized and hampered by air entrainment. The density-reliant dilution system meant that the feed stream was not being diluted, resulting in high flocculant consumption, poor overflow quality and lower than desired underflow density,” explains Dane Smith, Dewatering Product Manager at FLSmidth.
Following test work, a process review and structural analysis of the bridge and thickener tank, the FLSmidth team recommended a combination of the E-DUCÒ feed dilution technology and the E-Volute™ feedwell. The E-DUCÒ system uses feed stream momentum to induce large volumes of feed dilution prior to the feedwell, thus optimising flocculation due to improved mixing profiles and residence times.
“The E-Volute feedwell is characterised by excellent feed stream energy dissipation, optimal mixing energy and shear profiles. Subsequently, it promotes even feed distribution into the thickener with minimal floccule breakage, therefore improving the overall sedimentation performance. Specialists at the FLSmidth Supercentre in Perth completed the project from on-site test work and inspection, to process and mechanical design, fabrication of all components, installation, and finally, commissioning. No other OEM has the ability to provide such a breadth and depth of service.”
“Having control of the project meant we could keep to the required tight delivery schedule, while remaining in control of quality and planning on-site. This ability helped to shave three full shifts off the installation, allowing the site to return to full production far earlier than they had thought possible,” says Smith.
Initial data analysis shows a reduction in flocculant dose of approximately 34% and an increase in underflow density by approximately 2 wt% during the first two months. As the plant continues to optimise the new system under FLSmidth’s recommended control setup, flocculent savings are maintained and underflow densities have increased up to 8 percentage points from 48 wt% to 56 wt% (6% on average), limited only by the rake drive torque.
In addition to the achieved flocculent savings, the increase in leach feed density reduced total volumes reporting to the CIL, the minerals recovery process, by around 16.5%. Decreasing cyanide and lime requirements while significantly increasing available leach residence time, promoting gold recovery. The results are such that the 34 m leach feed thickener with FLSmidth technology is producing higher densities than the 44 m tailings thickener with non-FLSmidth OEM technology.