TAILINGS
For processing about 85,000 tpd of copper tailings , 3 x 45 m DCTs were designed , sold and installed utilising the spiral inner blade technology . The Kazakhstan DCTs have been operating for several years now . “ Considerable issues were seen initially as very large , unbalanced loads have occurred , causing multiple serious mechanical issues . The loads seen are significantly different from those seen with conventional large high rate thickeners . Initial work focused on reducing / optimising the flocculant dosage which helped but didn ’ t solve the issues . Considerable mechanical reinforcements were installed , as well as armouring areas where abrasive wear was apparent . Current operation shows consistent ability to operate at the design 68 wt %. This compares with their Plant 1 High Compression designs achieving on average only about 61 wt %. Drive torques for these new DCTs are typically in the 5-15 % range , significantly lower than typical DCTs operating at high densities . The low operating torques should allow for long life for the rake drive and mechanism .”
Based on the results from the first installation , the northern Chile copper concentrator bought a spiral inner blade retrofit for one of their tailings thickeners which has been fabricated and installed and is expected to achieve similar operational benefits .
Stantec on turning mine waste into a revenue stream
IM recently spoke to Stantec ’ s Resa Furey , Director of Strategy and Market Development and Michael Stine , Senior Mineral Economist , regarding the tailings reprocessing world . They highlighted that mining companies regularly reprocess old tailings and waste materials as processing technologies and markets improve . With the increased focus on sustainability and market excitement for critical minerals , there is a new focus on turning Tailings Storage Facilities ( TSFs ) and waste rock into value .
Furey adds : “ How might these ‘ human-made mineral deposits ’ be turned into mines of tomorrow ? Re-using , recycling , re-mining and reprocessing the material in TSFs and mine waste piles is the ultimate circular economy – taking waste and transforming it into a primary product creates value . Valorisation – the process of turning mine waste into something that has value - allows mines to contribute to sustainability metrics while improving their bottom line . Despite the promise , we have yet to see valorisation adopted on a significant scale . What ’ s holding us back ?”
She argues that tailings and waste valorisation projects face similar technical and financial challenges as typical mining projects . Technical challenges are solvable with enough money , the right equipment , good engineering , and , most importantly , new technology . Like most projects , the real hurdle then is the business case .
Stine adds : “ Depending on the location of the mine waste , by-products ( materials you extract from the waste and now wish to monetise ) may lack proximity to a market . If there isn ’ t an adjacent , local market , transporting by-products may be too expensive . In the case of aggregate by-products , if the local market is already well supplied , then producing more probably won ’ t make economic sense . The geochemistry of the existing waste can present other challenges . Metals like arsenic or cyanide aren ’ t allowed in aggregates or environmental fill products . Removing them ( usually required to make the final product safe for reuse ) may be cost prohibitive and can kill ( financially ) the project .”
Furey and Stine also point out that reprocessing tailings to extract critical minerals , while potentially lucrative , can face challenges related to their product specifications and market size . Stine : “ Take the cases of antimony or bismuth . Markets for both are small and low volume with few buyers and sellers with established relationships . Market information – about supply , demand and specific chemical forms required by the end users – is closely held and can be hard to get . The form of these minerals in the TSF may also not be compatible
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