Flotation Taking its Coarse
By Eric Bain Wasmund, Eriez® Flotation Global Managing Director
Environmental Social and Governance (ESG) considerations are becoming more important for investors, governments and the global citizenry when it comes to resource extraction. Developing new technology that can improve the efficiency of mining and lower it’s environmental footprint is a key differentiator for technology providers and operators. Eriez® Flotation is very sensitive to responsible resource extraction and our vision is to be a world-leader in this area. This means developing and delivering flotation technology that has significant benefits in terms of reducing environmental footprint and intensity of water and energy use while improving separation efficiency so that more metal can be produced from a smaller resource. And we have found that the key success factor is collaborating closely with our customers to evaluate and demonstrate our new technology such as the HydroFloat® for coarse particle flotation and the StackCell® for reducing the energy and capital requirements for conventional mechanical flotation.
About eight years ago we began working with base-metal sulfide miners to see how the HydroFloat could be used in their mineral processing flowsheets. Two applications showed immediate promise. The first used the HydroFloat to scavenge the final tails of a conventional concentrator plant. We called this the tail scavenging application. The second used the HydroFloat as an ore sorter, by operating inside the mill circuit to reduce the grinding intensity and generate a coarse barren tail. We called this the coarse gangue rejection application.
The tail scavenging application was commercialized by Newcrest at their Cadia Valley Operation in 2018 and is now being developed at a number of other sites. From our experience, the HydroFloat can capture at least 60% of coarse tails. Because a conventional mechanical cell flotation plant is very inefficient in this range, that means a significant amount of the run of mine feed can be diverted from waste, often 4-6%. This is the business case for the tail scavenging application, in addition to the ability to process more feed because the grind size is increased. Coarse particle flotation can be added as a brown-field retrofit to any conventional flotation plant in the world. In fact, Anglo American has announced that they will be adding it on to their greenfield Quellaveco plant so that it will be ready at the start up.
The coarse gangue rejection application is being demonstrated at commercial scale now. This has the potential to unlock additional green benefits, and it is being studied by multiple mining companies. One example of this application is shown in the flow-sheet below. The secondary mill output goes to a 2-stage size classification system, shown here as cyclones where the fine stream reports to conventional flotation, the coarse stream reports back to the mill circulating load and the middling stream reports to the HydroFloat. This allows an increase in the grind size, reduction in power and generation of a coarse and fine tail. In a recent case-study, we showed the possibility of reducing the energy requirement of the secondary ball mill by 30-50%. Additionally, approximately 30% of the total mill feed can be removed from the circuit at a size 2-3 times coarser than the grinding end-point of conventional flotation. Finally, the capacity required for conventional flotation could be reduced by 40%.
Anglo American has begun examining novel ways to co-deposit the coarse and fine tails that are produced by coarse gangue rejection, and their technology may be able to reduce or eliminate wet storage facilities. This is extremely important in regions with scarce water supply like Chile, not to mention the risk factors associated with long-term storage of wet tails, that have led to several major disasters over the last decade. In fact, there are probably other flow-sheets and processes that can be developed around the HydroFloat, now that tail scavenging and coarse gangue rejection are becoming mainstream.
Coarse particle flotation using the HydroFloat is a breakthrough technology that allows miners to recover more metal, produce less waste, use less energy and water, and have safer tailings. Eriez is excited to be involved in this revolution and thankful for our partners who are turning coarse particle flotation into industrial practise and finding ways to create additional synergies and benefits for improving the resource extraction.
Eriez Flotation will be exhibiting at the Austmine Conference in Perth from 26-27 May at Stand #227, and also at the AusIMM Mill Operators Conference in Brisbane from 23-25 June at Stand #52. Please visit us to see our wide range of products, innovative solutions and leading-edge technologies for the mining and minerals processing industries.
For more information please go to www.eriezflotation.com, phone us on 03 8401 7400 or email [email protected].