IM 2020 October 20 | Page 63

HIGH PROFILE
Reference : Cole , M . J ., Dickinson , J . E ., and Galvin , K . P ., Recovery and Cleaning of Fine Hydrophobic Particles using the Reflux™ Flotation Cell , Separation and Purification Technology , 240 116641 ( 10 pages ) 2020
wash water which allows us to control the underflow and overflow ; and that allows us to operate with very high wash water fluxes and very high gas fluxes , pushing us out into operating ranges that are not possible in open cell systems , when considering air and wash water fluxes , achieving simultaneously higher grade and higher recovery – shifting the grade recovery curve along with increasing the throughput of the equipment . A typical scale up factor for conventional equipment in benchtop kinetics tests is 2 to 2.5 times . For the RFC this is a number less than 1 , meaning you have a reduction in the flotation volume needed .”
Market potential
There is a big potential market across all the major flotation markets including , but not limited to , coal , gold tailings , graphite , iron ore , copper roughing , moly cleaning – where in every case the RFC is operating on the left hand side of the kinetics curve . “ We are seeing recoveries beyond what is possible in a conventional benchtop testing . In coal for example , the RFC performance is being predicted utilising a coal grain analysis method which gives the true ultimate flotation response . The RFC is operating on this curve , which is to the left of a traditional tree curve that is typically used to predict conventional flotation performance . That means in coal we are able to produce much lower ash product with very similar combustible recovery numbers than you would see with traditional coal flotation technologies . We are recovering
much more coal – meaning the RFC has huge potential in recovering coal fines from tailings streams or retreatment of already stacked tailings for example . Beyond this , we can also offload overloaded coal flotation circuits as the RFC is a high capacity machine with a small footprint .”
While coal has historically been the initial focus of the technology development recent testing in 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 retention time . “ In some cases we are producing not only a higher grade product at a higher recovery rate but also in a shorter timeframe .”
RFC versus other technologies
Comparing it with other hydraulic technologies like column flotation , in that case you have two types of sparging systems – one is air introductory only which is based at the bottom of the cell ; which has many similarities with conventional flotation . The other column flotation sparging
system is a recirculating pump which draws material from the base of the column and passes it through the contact area – “ in this respect there is a similarity with our RFC , except that the RFC sees the contact with the feed material where the concentration of the floatable material is at its highest in terms of the feed slurry , whereas in column flotation , the contact is usually with the tails of the column , where the floatable material concentration is at its lowest . The RFC ’ s method of contacting with the feed promotes the flotation kinetics better than with the tails .”
A comparison to the Imhoflot cell shows similarities in the initial first high intensity precontact step , but beyond this FLSmidth says the unique nature of the RFC segregation comes into play to bring performance well beyond what is possible with any other cell . All other flotation technologies also have froth recovery limitations – the RFC doesn ’ t really have a defined froth-pulp interface further promoting recovery .
Christodoulou adds : “ The unique nature of the design and use of the lamella plates means this isn ’ t something you can retrofit onto existing conventional cells . To start with we see RFC flotation being able to work to offload overloaded circuits in coal and base metal cleaner circuits , then start to replace column flotation circuits , and ultimately replace banks of open conventional cells , though there is still some way to go for full market acceptance before we get to that point .”
RFC site trials
A number of trials have already been carried out with a pilot scale system that is similar in scale to the lab scale system except that the pilot testing has been on a continuous basis using a continuous feed . In addition to the pilot , FLSmidth and the University of Newcastle are currently trialling a two metre RFC machine in an Australian coal application . This full-scale evaluation is set to be completed early 2021 .
The pilot site trials use a containerised test skid housed in a standard 20 ft shipping container . The test skid can be deployed quickly and can be commissioned in less than a week , with typical test programs wrapping up in four weeks or less . Utility and feed requirements are minimal with typical tests requiring less than 100 litres a minute of feed slurry . IM
Pilot site trials use a containerised test skid housed in a standard 20 ft shipping container . The test skid can be deployed quickly and can be commissioned in less than a week
OCTOBER 2020 | International Mining 59