FLOTATION
Coarse and fine
Flotation technology is evolving fast , and the coming years will see greater adoption of newer designs in the latest future flowsheets – Paul Moore reports
Flotation continues to be the workhorse of mineral separation across the mining sector . While almost all of this remains tank cell based mechanical flotation , the playing field is changing – in part due to mining companies wanting to reduce the need for fine grinding and therefore save energy costs , but also to be able to better recover metals from tailings streams . Enter coarse particle flotation , ( CPF ) or sometimes just referred to as coarse particle recovery ( CPR ). What started out mainly in the potash and phosphate sector is now becoming established in the all important copper mining sector . And not only that , the largest mineral processing technology and conventional flotation providers know its potential and importance , so are coming up with their own CPF solutions , despite it having been advanced to date by smaller or more focused players . At the other end of the particle scale , new technologies are also allowing recovery of more valuable fine particles which can be lost in other flotation cells .
One of the focused CPF players is Eriez – its coarse particle flotation technology , HydroFloat , is able to float material and recover it at a much coarser particle size . As started , grinding has always been required to reach very fine sizes for conventional flotation – if you can now float say a copper particle at 600 microns instead of 150 microns , then the amount of grinding you have to do is greatly reduced .
HydroFloat technology was proven in lab work then pilot plants , and today is being adopted in the industry . IM spoke to Eric Bain Wasmund , Vice President , Global Flotation Business at Eriez : “ What we ’ ve found is that its introduction is following a market by market trend in mining – it began to be used widely first in the phosphate and potash industry , such as at Mosaic ’ s South Fort Meade Mine and at PotashCorp ’ s Aurora beneficiation plant amongst others , but then we almost had to start again to prove the technology in copper in the early 2010s and now iron ore in the 2020s .”
This was driven by increasing awareness in the copper sulphide world that a significant fraction of semi-liberated coarse ore was not being floated in conventional concentrator plants and was instead accumulating in tailing dams around the world . Today , after many demonstration installations at sites like El Soldado & Mogalakewna and Kennecott , HydroFloat has finally reached widespread acceptance in copper applications .
To give two examples , Newmont ’ s Cadia Valley in NSW now processes 100 % of its copper-gold tailings through a CPF circuit featuring the Eriez HydroFloat , which represented the first commercial operation . The team at Newcrest ( now Newmont ) really did their homework and were the first to commercialise CPF in sulphide flotation . The Eriez and Newcrest technical teams worked together for years . Later , a HydroFloat coarse particle flotation plant was engineered and built later in 2019-2022 to process the full Anglo American Quellaveco copper tailings stream in Peru . That plant began commissioning in Q4 2023 . The Anglo El Soldado plant is a ‘ Coarse Gangue Rejection ’ circuit ,
where the HydroFloat receives as its feed , mill circuit output prior to conventional flotation and produces a coarse , barren tailings . Wasmund : “ The Cadia Valley plant and the Quellaveco plant are brownfield installations that scavenge
Eriez Hydrofloat has now been deployed at more than 20 sites globally
tailings at the end of the flowsheet , recovering coarse gold and copper sulphide composite particles that were formerly being lost . It also allows you to increase the grind size - allowing the comminution circuit to achieve higher throughput .”
Today , Wasmund said that Eriez has more than 20 CPF installations around the world when you factor in all commodities as well as the demo plants , and each of these installations has multiple HydroFloat units . So what is next ? In addition to phosphate / potash and copper sulphide minerals , there are now a number of other studies and projects using the Eriez HydroFloat for coarse gangue rejection of silica in iron ore flotation . Wasmund : “ Quebec Iron Ore has been working with Eriez and BBA to develop an innovative direct reduction iron ore ( DRI ) quality production process for the Bloom Lake mine that equally will increase DRI iron ore recovery , minimise energy consumption as well as reagent consumption . This process utilises energy-efficient tower mills in combination with split-feed flotation using HydroFloat CPF and conventional flotation technologies .”
In doing so , direct reduction pellet feed ( DRPF ) quality iron ore is produced with more than 1 % SiO2 at nearly two times the target grind size and with improved global iron recovery compared to conventional milling and flotation processes . The coarser concentrate generated through this process also improves product material handling , storage , and transport with reduced dust generation and improved moisture control as compared to finer concentrate from the conventional DRPF quality iron ore process . Iron ore is actually potentially an even bigger market than copper .
But Wasmund says to see HydroFloat in its most ideal context you also have to accept that its true potential will come with outside the box thinking on the whole flowsheet . “ It is important to remember that this is not a retrofit or ‘ drop-in ’ replacement of an existing bit of equipment – it is not a mechanical flotation cell – you have to rethink the flowsheet . So we are working with partners , including engineering companies and others to commercialise entirely new flowsheets . We are thinking about where you do flotation , how do you do it , what do you have to do to the ore to prepare for it , how do you handle the tails . We also have a consortium at the University of Queensland where a group of the top Tier 1 mining companies are working with us on the adoption and perfection of the right flowsheets for this CPF technology .”
If you can grind coarser , you can scavenge current tails and get some of the coarser copper particles that were missed with conventional
International Mining | OCTOBER 2024