FLOTATION TECHNOLOGY
The SFR the company says was developed by going back to the first principles of flotation and examining how best to optimise the various phases of flotation without preconceived constraints . The result is a machine that optimises the three stages of flotation within three separate zones , such that each zone is mutually exclusive from the requirements of the other zones . Froth drop back is minimal and tightly controlled . The constrained froth recovery zone allows for much better level control in a scavenger SFR , resulting in better recovery and upgrading .
Discussions with customers have often led first to a pilot using its innovative SFR pilot rig which was developed as an appropriate step between batchmode bench-scale testwork and continuous operation . The rig provides the demonstration of semi-continuous performance but using the small sample sizes typically available during the development phases of new Greenfields projects . The SFR rig operates in semi-continuous mode , utilising a single SFR stage fed with approximately 20 l / min of slurry feed . The tails after each pass through the SFR is collected and re-processed to emulate continuous performance .
The first major engagement with a large mining company was with Dundee Precious Metals . A 2012 mining study design for DPM ’ s Ade Tepe gold mine in Bulgaria ( Krumovgrad project ) incorporated a flowsheet developed from an extensive test program completed at SGS and a subsequent FLEET circuit modelling program . This specified the equipment required to achieve the predicted metal recovery for the two throughput options being considered for the project at that time . The first iteration of the plant design undertaken in 2012 incorporated the mining study conventional tank cell design for the flotation circuit , which was the base case for the first round of capital cost analysis . One of the subsequent trade-off studies included a layout comparison of the tank cells and at the time a new style of flotation cell , Woodgrove ’ s SRF . In parallel to the Ade Tepe test program , DPM had incorporated a production size unit of SRF cells into the Chelopech cleaner circuit in mid-2012 at that mine , also in Bulgaria . This offered some significant advantages over conventional ‘ tank ’ cell designs , including reduced floor area requirement , reduced circuit operating costs ( power and air demand ), together with some process advantages in most applications . Because of overall site layout restrictions space in the plant area was at a premium , and the study outcome confirmed some of the advantages claimed , but of particular importance to the project was the potential reduction in floor area ( approximately 30 % of the original flotation circuit footprint ), DPM elected to continue with the SFR approach and these units were incorporated in the final design . Chelopech completed the installation of an upgraded cleaner circuit ( second and third cleaners ) in their primary production circuit in mid- 2013 , and then installed a new recovery circuit for
Two Woodgrove Staged Flotation Reactors ( SFR ) on scalper circuit at Lundin Mining ' s Chapada operation
downstream recovery of pyrite from the cleaner tailings stream . This circuit is very similar in equipment sizing to the rougher circuit at Krumovgrad .
At Krumovgrad , the whole flotation plant was provided by SFR . The concentrate from the first stage of the rougher / scavenging flotation ( four units for each stage ) is sent for regrind in the tertiary grinding circuit ( to a P80 of 15 µ m ), and then cleaned in the first cleaner ( two units ) to produce final concentrate . Tails from the rougher circuit are scavenged and the concentrate recycled back to the rougher feed . Tails from the first cleaner are retreated in the cleaner / scavenger bank ( five units ), the tails from which return to the feed to the rougher . The scavenger cleaner concentrate will be recleaned in the second cleaner ( four units ) producing final concentrate , with the tails being recycled back to the feed of the cleaner / scavenger bank .
DPM has certainly been very happy with the technology . President Richard Howes has stated : “ We have proven it is a no brainer , and are the first company to use this on a broad basis … we will use it wherever we can as there are so many environmental and economic benefits to it .”
Things moved up a notch in the late 2010s . In 2017 the company signed a contract to supply 78 SFR cells to BHP ’ s Spence Growth Option copper mine expansion in Chile . SGO was developed to enable mining and processing the hypogene ore that lies below the current oxide and supergene deposit . The hypogene ore is processed through a new concentrator constructed close to the existing Spence oxide leaching facility .
The company also has extensive experience working with Vale in Brazil . At its Salobo II copper mine expansion which doubled throughput to 200,000 t / y , SFRs were installed on the rougher tailings . The concentrate from the SFRs reports to concentrate regrinding . SFR tailings gravitate to the tailings storage facility ( TSF ), while the concentrate advances to the regrinding circuit . This success came directly from a demonstration plant at Vale ’ s other major copper operation , Sossego .
At Lundin Mining ’ s Chapada copper-gold mine in
Brazil , the cyclone overflow from the concentrate regrind circuit flows to two SFR cleaner scalper cells . The concentrate from the SFR scalper cells is final concentrate grade and is pumped to the concentrate thickener . The cleaner scalper tailings are pumped to a bank of six 21.5 m 3 conventional cleaner flotation cells . The cleaner tailings are pumped to a bank of four SFR cleaner scavenger flotation cells . In 2019 , the operation added six Direct Flotation Reactors ( DFR ) as rescavengers were installed ( see below for DFR outline ).
At New Gold ’ s New Afton copper and gold mine in British Columbia , Canada , the tertiary grinding cyclone overflow flows by gravity into the rougher flotation circuit , which consists of two staged flotation reactor ( SFR ) cells in series followed by six 100 m3 flotation tank cells in series . The two SFRs were commissioned in Q2 2017 . The concentrate from the rougher flotation cells is collected in launders and flows by gravity to the regrind circuit ; the tailings from the final rougher cell are discharged into the tailings pumpbox .
Three SFR cells were also added to the head of cleaner flotation as part of the mill expansion project in 2015 to increase cleaner flotation capacity . The concentrate from these three cells is combined with the inline pressure jig final concentrate , third cleaner concentrate , and regrind Knelson concentrates to produce the final copper concentrate for dewatering . The SFRs were capable of achieving final concentrate grade in a single pass without the integration of recirculating loads , a strategy sometimes referred to pre-cleaning .
Aside from the SFR , the Direct Flotation Reactor ( DFR ) is a flotation cell that works on the principle of preventing the formation of a froth and froth slurry interface . Independent bubbles are removed from the collection zone in a gas phase / slurry phase . The flotation cell has a particle collection regime in the lower half of the vessel and the loaded bubbles are recovered at the top of the vessel . The complete unit is a pressurised system . The DFR has a very low footprint due to the absence of a froth phase .
In July 2020 , Copper Mountain Mining Corp said it had successfully installed and commissioned DFRs at its Copper Mountain mine in British Columbia on schedule and on budget . This represents the first stage of its mill expansion project which will bring plant capacity to 45,000 t per day from 40,000 t per day . The installation of the DFRs increases the efficiency and the capacity of the current cleaner circuit , which is expected to increase copper concentrate grade from about 25 % to 28 %, resulting in lower concentrate transportation , smelting and refining costs . Gil Clausen , Copper Mountain ' s President and CEO : " The DFRs have been commissioned and turned over to operations . This is a testament to the great work of our operating and projects team . The DFRs are a low capital , high return project and we are already seeing improved concentrate grades .”
IM
32 International Mining | NOVEMBER / DECEMBER 2020