HIGH PROFILE
Testing in coal , copper , moly , gold , iron ore , and graphite applications have all produced similar results in terms of improved grade and recovery along with a reduction in required flotation
Flotation REFLUX™ revolution
Paul Moore spoke to FLSmidth ’ s Lance Christodoulou , Global Product Manager – Flotation , about the revolutionary REFLUX™ Flotation Cell ( RFC™ ) which is being developed together with the University of Newcastle & brings a unique design that is capable of achieving higher grades , recoveries and throughputs of any other flotation cell currently available
Development of the all new REFLUX Flotation Cell ( RFC ) has been an extension of the already established development partnership with the University of Newcastle , working closely with Professor Kevin Galvin , who is Director ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals . This partnership has already seen the successful development and commercialisation of the REFLUX Classifier ( RC™ ) with a similar commercialisation path being envisioned for the new REFLUX Flotation Cell .
Christodoulou says there is already an expansive database of supporting pilot-scale data and is working with clients to investigate suitability of the implementation of the technology into their flowsheets . These efforts can typically start off with lab scale testing with their ore followed by on-site pilot testing ultimately leading , in principle , to full scale installation . The lab scale work is possible either at the University of Newcastle or at FLSmidth in Salt Lake City . “ If that testing goes well then we would recommend onsite trials with our containerised pilot system which receives diverted continuous feed from the main process route . We have a number of these pilot units , which are available for on-site testing and can be shipped to test sites globally . We already have a fairly well developed set of models that will help predict how the RFC will fit into a flotation circuit in design and scale terms . We have existing data sufficient for high level technical studies such as feasibility work .”
Technology background
The RFC joins the wider suite of REFLUX technologies along with the REFLUX Classifier , which is a hydraulic classifier that separates particles using gravity , based on a difference in density or particle size . It combines a conventional fluidised bed separator with a set of parallel inclined plates that form lamella channels , and this lamella technology is what is implemented in the RFC . That said , the REFLUX Flotation Cell utilises flotation principles instead of gravity principles as with the RC™ .
Christodoulou told IM : “ You are essentially dealing with a form of staged flotation in that we take the feed and it makes contact with air in an environment where there is high energy density and high shear rates , effectively increasing the probability of collision and attachment to promote the kinetics of the system . The whole system we believe is unique in its design and mechanics . Once you have the contact occurring with the feed and air supply , this bubbly mixture is then passed down into a chamber which operates at a very high air fraction , much higher than anything currently available in the market and approaching what we would call flooding conditions .”
He adds : “ We control the operation of the equipment with a positive bias flow – which means a generally downward volumetric flow of material but because you are operating in these conditions , you start dragging this bubbly mixture down into the bottom of the device . In traditional open top flotation cells , this mixture would simply be pulled out of the bottom of the cell . With the RFC the lamella plates come into play – which , due to the Boycott effect , allows this bubbly mixture to segregate very efficiently , preventing any loss of air bubbles to underflow . This enhanced segregation capability allows us to operate at a very high air fraction and control what is coming out of the overflow in terms of volumetric flow rate – it allows us to control the bias of the system . Then , with the application of wash water , we are able to displace any material that is coming up in the remaining water present in the bubbly mixture to maximise control of the grade so we can achieve a very high quality product coming out of the overflow .”
FLSmidth says it has seen a good technology transfer of the RC in terms of the lamella plates , which enhances segregation , to implementation in flotation in the form of the RFC . In the RC the lamella plates allow for much higher separation efficiencies effectively producing a much steeper partition curve when considering density and sizing applications . In the RFC having this allows for advanced bubble slurry segregation , allowing the RFC to operate in higher air fractions with higher air flux and higher throughput . “ You have improved kinetics , improved grade and improved recovery all at the same time . In a normal flotation cell as you increase the gas flux , you start entering an operating condition where you lose the interface so there is no discernible difference between the pulp and the froth – so called flooded conditions . For example , if you run a conventional cell at the same gas fractions as we run the RFC , you start operating at flooded conditions which results in bubbles and pulp that contains valuable mineral being discharged out of the tails , so you aren ’ t effecting a very good separation or separation efficiency . In most open cell systems , you have an upper limit in terms of the bubble surface area flux that you can realistically operate at , even if you increase the gas flux or reduce the bubble diameter . The RFC lamella plates allow you to achieve the segregation and therefore operate with a smaller bubble diameter as well as higher superficial bubble surface area flux which then allows for better recoveries .”
The chamber operates at extremely high gas flux so a really high air fraction environment . “ We have enclosed the system and apply fluidisation
58 International Mining | OCTOBER 2020