MINERAL PROCESSING
THICKENER UPGRADE: WHERE FINANCIAL AND SUSTAINABILITY OVERLAP UPGRADING THE THICKENERS AT ONE OF AUSTRALIA’S LARGEST GOLD PRODUCERS NOT ONLY BOOSTED THE MINE’S BOTTOM LINE, BUT IT ALSO REALISED IMPORTANT SUSTAINABILITY BENEFITS, AS THE FLSMIDTH TEAM BEHIND THE PROJECT EXPLAINS.
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hickeners are a ubiquitous feature at mineral processing facilities and have been for many decades. And in an industry where the lifetime of major equipment is often measured in decades, they are particularly long lived. FLSmidth – whose association with thickeners goes back more than a century via the Dorr-Oliver and EIMCO brands that it acquired in 2007 – has many systems still operating at Australian mines that were installed in the 1960s, while a couple date back as far as the 1930s and 1940s. In addition to its role in the production of target minerals, thickeners play an important part in mine water management and recycling: areas of focus in today’s mining industry where sustainability is becoming an ever more pressing dayto-day concern. This is particularly true of mines in regions of high water stress, which is how the World Resources Institute categorises most of Australia. With thickeners infrequently replaced, improving the performance of existing installations is key to meeting the industry’s changing sustainability and performance goals, according to FLSmidth Australia’s head of mining David Williams. “Thickener technology is constantly evolving. Refurbishing and retrofitting therefore helps to ensure the ongoing integrity, reliability and productivity of existing machinery with the latest advances in thickener technology,” Williams said. “At FLSmidth, we combine years of engineering expertise to offer a complete service package – from equipment and process evaluation to tailored upgrades, including complete new mechanisms, feed systems and new drives.” FLSmidth’s experience and technology range is comprehensive, including the world’s largest and highest-capacity bridge and columnmounted thickeners.
THE 44-METRE THICKENER WAS FITTED WITH A P-DUC MECHANISM AND E-VOLUTE FEEDWELL TO IMPROVE THROUGHPUT AND UNDERFLOW DENSITY ACROSS A RANGE OF FEED CONDITIONS.
Not keen to rest on its laurels, however, the company is always looking forward. Its research and development model integrates the evaluation of new technologies and concepts with continuous review and update of existing products. “Our efforts focus on the development of solutions that combine high performance, reliability and availability with minimal environmental impact, in line with our MissionZero goal to reduce the water use and footprint of mining operations,” Williams said. Among the latest developments in thickener technology offered by FLSmidth are its E-Volute feedwell and E-DUC and P-DUC feed dilution systems. “The E-Volute feedwell is the result of many years of development work, including CFD modelling, at the laboratory and pilot scale,” FLSmidth global product line manager for thickening Fred Schoenbrunn said. “The result is an involute design with sloped tapering shelf and sloped inner shelf, which promote superior energy dissipation in the feed AUSTRALIANMINING
stream, optimal mixing and improved shear profiles to ensure thickener performance and efficiency.” According to Schoenbrunn, this provides a range of benefits including: • increased retention time in the feedwell • maximised solids throughput • reduced shear rates and minimised flocculant consumption • increased flocculation efficiency • even distribution of feed slurry/solids • enhanced settling rates and increased equipment capacity • optimised underflow solids • minimised short circuiting • reduced overflow solids. Supporting the work of the E-Volute feedwell are the E-DUC and P-DUC feed dilution systems, both of which are designed to ensure even distribution of flocculated solids in the feed before it reaches the E-Volute feedwell. “The E-DUC system is appropriate for applications that require consistently large volumes of feed dilution, whereas the P-DUC system incorporates a variable speed drive that
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allows for variable dilution flowrates in applications where large variations in feed flow or density are expected,” Schoenbrunn said.
Case study: Feed system retrofit at an Australian gold operation
FLSmidth has supported thickener performance upgrade at one of Australia’s largest gold mines for several years. When the mine first approached the engineering company, it was operating third-party 34m diameter leach feed and 44m diameter tailings thickeners, and nameplate capacity was 700 tonnes per hour (tph). “We initially upgraded the leach feed thickener, installing an E-DUC dilution system and E-Volute feedwell,” FLSmidth regional product line manager for dewatering Anson Gilbert said. “This increased leach feed thickener underflow density from 48 per cent to 54 per cent solids at 850tph of feed solids, resulting in significant savings in both lime and cyanide consumption, as well as increasing carbon in leach (CIL) residence times.
