Clariant is partnering with customers to develop and test special collectors to reduce ultrafine particle losses and to recover value from tailings. (Photo: Clariant)

A host of new technologies and designs are taking flotation performance to the next level

By Carly Leonida, European Editor

Flotation might be one of the longest standing techniques in beneficiation, but it’s certainly not standing still. Today, new cell designs and digitally enabled control and monitoring technologies are not only driving efficiencies in traditional applications, but also opening new ones that speak to miner’s ambitions to be profitable yet responsible providers of critical minerals and metals.

The recent MINEXCHANGE event in Salt Lake City, USA, in March (the SME Annual Conference & Expo) heralded the launch of two new FLSmidth products — the WEMCO II and the REFLUX Flotation Cell (RFC).

There are more than 40,000 WEMCO flotation cells installed at mining operations across the globe, and the WEMCO II builds upon this success, incorporating improvements to the WEMCO rotor and stator/hood to lower power consumption, while increasing air flow and slurry pumping. The results are better hydrodynamics and circulation, improved kinetics and performance, optimized energy efficiency and lower operating costs, and the ability to control air without an external air supply.

WEMCO, But Better

Dariusz Lelinski, FLSmidth’s global product line manager for flotation, spoke about the new design.

“WEMCO is the most popular flotation machine in the world,” he explained. “The rotor/disperser/hood design for conventional WEMCO machines had not been modified for a while, and we decided recently that it was a good time to improve it as we could see some real benefits.”

The goal of the WEMCO II project was to improve specific areas of the WEMCO and to make the new developments easy to retrofit into existing machines.

“We started with a brainstorming session with FLSmidth experts from many departments and came up with major project objectives and possible design changes,” Lelinski said. “In the next stage, we worked in two parallel paths: 3D printing of dozens of rotor/disperser concepts followed by tests in the laboratory environment (metallurgical performance) and making computational fluid dynamic (CFD) models of these concepts for hydrodynamic evaluation. Based on the results, the selected concepts were modified and tested more intensively.”

The best performing units were then tested at pilot scale — 1.5 m3 — in plant conditions using a distribution
box and two units — conventional
WEMCO and WEMCO II — for the best possible comparison. The top performing WEMCO II rotor/disperser/hood design was selected to be retrofitted into two WEMCO 1+1 cells in rougher duties, and two WEMCO SmartCell 250-m3 units in rougher and scavenger duties. These tests are now underway.

“Designing WEMCO II, we used our experience and lessons learned from the nextSTEP rotor/stator technology development to improve four selected areas: metallurgical performance, air control with the self-aspirated method of air induction, lower power consumption through more efficient slurry and air pumping, and reduction of the ‘WEMCO wave,’” Lelinski said. “We believe that a controlled wave is beneficial for froth recovery.”

WEMCO II is similar to the nextSTEP rotor/stator, which FLSmidth launched in 2015, as it has a new rotor design for more efficient pumping, and the disperser was replaced by a stator with blades. This results in smaller bubbles and better energy dissipation.

Lelinski added: “We also redesigned the WEMCO standpipe to stabilize the vortex and slurry surface. Of course, all these changes are unique and patent protected.”

It’s worth noting that WEMCO II is part of FLSmidth’s MissionZero initiative and can be combined with nextSTEP in one row — a concept called mixedROW. Lelinski said the combination of these two mechanisms gives the lowest energy consumption at the highest performance for any conventional flotation machines in a market.

WEMCO II components have been designed to be retrofitted to all existing WEMCO cells, which lowers the cost barrier for mines with an existing installed equipment base. As with the conventional WEMCO, WEMCO II is best suited to rougher applications where the recovery is the most important part of the performance; rotor placement at the top assures its advantage in this part of the flowsheet.

“We performed nine full WEMCO II versus conventional WEMCO pilot campaigns at the North American Cu-Mo Concentrator and are confident that it will also prove itself during full scale industrial tests,” Lelinski said. “Two concentrators were also selected — one in North America and one in South America — to test WEMCO II in both the WEMCO 1+1 and WEMCO SmartCell tanks. Agreements with these two companies are now signed; the mechanisms are scaled-up and are being manufactured at this moment.”

REFLUX Receives Official Launch

The REFLUX Flotation Cell (RFC) also had its official launch at MINEXCHANGE 2022. E&MJ readers will be familiar with the cell that was patented in 2011 by Professor Kevin Galvin at the University of Newcastle in Australia. FLSmidth has a longstanding relationship with the university and has served as the commercialization partner for various technologies developed there, including the REFLUX Classifier.

The RFC has now evolved from conceptual design to a full-scale industrial machine. Several laboratory and pilot test campaigns have been executed with results consistently showing high-grade recovery in a fraction of the footprint normally associated with open tank, traditional flotation.

FLSmidth described the RFC as “a ground-breaking technology that reduces plant footprint as well as water, air and energy requirements.” Aside from reducing capital expenditure by 35%, the RFC requires no direct power input, which can lower energy use in a flotation circuit by up to 60%. Improved kinetic efficiency reduces the amount of water used in the recovery process, and the nature of the technology also reduces the plant footprint, requiring less concrete for installation than traditional systems. Best of all, it has a wide range of applications and can be used in rougher, scavenger and cleaner roles across all minerals.

Lance Christodoulou, global product line manager for REFLUX Technologies, gave E&MJ the inside track.

“The RFC is essentially a staged flotation device where feed is pre-contacted in a sparger system, ensuring elevated collision and attachment rates,” he explained. “This contacted bubbly mixture is transported downward into the main chamber of the RFC where air fractions in the order of 45% are present. Consequently, this provides an order of magnitude greater bubble surface area for further collection of floatable material.”

The system is “frothless.” The bubbly mixture is transported to the overflow while being washed with fluidized water to produce high grade concentrates. The cell operates with a strong positive bias or downward volumetric flow, and the inclined channels allow for enhanced bubble-liquid segregation affording downward velocities in excess of bubble terminal rise rates. This enables the RFC to process feed fluxes much greater than the typical industrial limit of about 1 cm/second.

Christodoulou said: “The machine is not flux-curve constrained and can operate at feed and gas fluxes much higher than in conventional systems. The system allows for a shift in the grade recovery curve producing high grade product at high rates of recovery. It’s a highly efficient flotation system.”

The RFC has been successfully tested in various commodities, including copper, molybdenum, gold, iron ore, graphite and coal. Successful trials of a 2-m-diameter RFC are currently under way in Australia, and Christodoulou said metallurgical performance so far is reflective of expectations. Efforts are in progress to further push throughput and to optimize performance.

FLSmidth’s REFLUX Flotation Cell and WEMCO II on display at MINEXCHANGE 2022. (Photo: FLSmidth)

An FLSmidth-led mining and resource efficiency innovation project funded in part by EIT RawMaterials is also under way, which will see trials of an 850-mm-diameter unit in both copper and iron ore.

“Additionally, we are in the testing phase with another REFLUX technology called coarseAIR,” Christodoulou said. “This technology utilizes the highly efficient nature of the REFLUX classifier and expands it to coarse particle flotation (CPF).”

StackCell and HydroFloat Gain Momentum

The single biggest challenge in flotation is declining ore grades. To maintain production requires mines to process much larger volumes of material and, subsequently, produce larger volumes of waste (tailings), which must be stored. Flotation uses significant energy, water and equipment, and so the requirement for increased processing will drive the development of more efficient technologies.

Eriez’s StackCell and HydroFloat technologies are fast gaining a reputation as a frontrunner in this respect. Eric Wasmund, vice president of Eriez’s Global Flotation Business, gave E&MJ an update.

“The HydroFloat is now being accepted as a mature industrial technology by a number of mining companies, since the first commercial CPF plant at Cadia T3 in Australia was started in 2018,” he said. “Today, dozens of companies are conducting lab and pilot work to build business cases for implementing the HydroFloat into their projects or facilities.

“The industry is also accepting the idea that the StackCell can be a much more efficient mechanical cell and can transform the rougher flotation cell market where we currently have a few installations.”

A paper presented by Newcrest at the MillOps conference in Brisbane last year detailed the optimization of rougher cells at the Red Chris copper-gold mine in British Columbia, Canada. As part of the program, the miner conducted a pilot of six StackCells and compared their performance directly with that of conventional stirred tank cells. The results corroborated earlier work that showed the StackCell could achieve the same separation results in a working volume of 20%-25% of conventional units.

“Here you have a major mining company showing the benefits of the StackCell as a rougher, compared with the incumbent technology in a side-by-side comparison,” Wasmund said. “The Newcrest team has studied this under a very thorough metallurgical lens. It will be interesting to see what happens next.”

The StackCell product line has been recently re-engineered so that a single unit can process similar volumes as a 300-m3 cell, and the team will be commissioning some of these new units later this year.

Wasmund added: “With StackCell, we are seeing a strong interest in using this technology as roughers, which means cells in series, so we are focusing strongly on this application. For the HydroFloat, we are seeing great interest in tail scavenging, and that is because of the opportunity created by the inefficiency of conventional industrial flotation technology.”

CPF has only been available at an industrial scale for a relatively short period, but Wasmund said Eriez is starting to see some interesting applications and benefits come to light as customers begin to think creatively about how the HydroFloat technology can be used.

An Eriez Flotation Industrial HydroFloat CrossFlow copper installation. (Photo: Eriez)

“The first application was in ‘tail scavenging,’ which can recover lost ore in tails and decrease energy use by increasing the flotation feed size,” he explained. “But tail scavenging is essentially getting back some of the losses after the main problem has already occurred, and that problem is over-grinding.”

Over-grinding means using excessive power for grinding and dewatering, producing a tail that is less safe to store than it could be. Using the HydroFloat as an ore-sorter, coarse gangue rejection (CGR) can allow a reduction in secondary mill energy of 30%-50%, a reduction in conventional flotation capacity of 40% and the production of a coarse tail stream that is 2-3 times coarser.

Anglo American is looking at technology to combine this coarse stream with fine conventional tails to produce a stable dry stack that will be more environmentally friendly than conventional impoundments.

What’s next for Eriez? 

“We listen carefully to our customers about the challenges that they face. They understand the complexities and future direction of their businesses very well, and they point the direction to the type of ‘value-adding’ innovations or adaptations that we bring to the market,” Wasmund said. “One thing we have done is to increase the scale of the equipment we sell. Based on our understanding of the fundamental principles, we are now able to scale up our products to address our customer’s desire to include these in larger circuits.”

Jameson Cell Technology Extends to Concentrators

Of course, some mines will always be slower to evolve technologies, even to those that are shown to perform all duties at faster rates more effectively with a lower footprint and capital. The Jameson Cell is still perceived as “new” to some, even though the technology is now 30 years proven. 

“With increasingly complex orebodies adding challenges to the industry, it’s imperative to chase environmental, social governance (ESG) goals like smaller footprint and energy usage in order to make way for the increase in metal demand and decrease in viable mine grades,” said Glenn Stieper, technology manager for mineral processing at Glencore Technology.

The Jameson Cell was developed to overcome the design and operating inadequacies of conventional flotation cells and column cells. From its first installation, it has been continuously improved to make it easier to use and designs are now at Mark V.

“The beauty of the Jameson Cell is that, compared to alternative technologies, it has a higher carrying capacity allowing for a larger treatable tonnage, reducing its footprint,” Stieper said. “Tank volumes are also much smaller comparatively and process all sizes of ores. The Jameson Cell performs well in all duties with better grades and recoveries, and this allows for a reduction in energy usage. The decrease in moving parts also lowers hazard risks and increases the safety of on-site staff. We are constantly innovating our technologies so that clients stay on top of their ESG goals. This allows us to have a competitive edge.”

Glencore Technology can provide full concentrators through to flotation circuits and multiple cells, as well as (if necessary) the IsaMill for regrinding. Froth pumps can also be added to a conventional centrifugal concentrate pump for processing high froth-volume factor slurries.

“Having been developed originally in Australia, [froth flotation] is a technology the mining industry has been continuously innovating since its inception in the early 20th century,” Stieper said. “This includes ensuring the technology moves with the times and continually meets new ESG goals. An example of this is by producing more concentrate from the same orebody. We have also created new ways to ensure a smaller footprint and energy use.”

In line with this ambition, Glencore Technology has several exciting changes in the pipeline and in various stages of rollout.

The team recognized that the standard Jameson Cell design has unnecessary height requirements, which can be removed without compromising its performance or reliability. The new ERM-Less design takes several meters off the height, which results in further capital savings.

Stieper added: “We have kicked off a number of Jameson Cell retrofit projects investigating CPF applications, which will allow us to further innovate our technology, and we’ve also moved into more aggressive promotion of our Jameson Concentrator plants.”

Jameson Concentrators combine Jameson Cells into a complete flotation circuit without the need for less efficient and more costly conventional cells. When combined in this manner, Glencore Technology said the benefits to both the end client and environment are “substantial and will have a profound impact on the way we design concentrators in the future.”

“Our concentrators are extremely beneficial to those chasing smaller footprints, especially in colder or elevated climates,” Stieper said. “They have the ability to process the same or greater throughputs while using less energy input and equipment, without disrupting metallurgical performance. We are also finding increasing demand for all base metals (Cu, Pb, Zn, Ni, etc.) and gold. Our cells are also gaining momentum in niche markets like molybdenum and graphite.”

A new Jameson Concentrator is commissioned at Hudbay’s New Britannia operation in Canada. (Photo: Glencore Technology)

A new Jameson Concentrator has recently been commissioned at Hudbay’s New Britannia operation in Canada. The circuit encompasses several advantages over the alternative conventional circuit that was also considered. The new setup sees four Jameson Cells replacing 11 Tank Cells and has a 50% smaller footprint, requires 50% less power, and fewer spare parts than the conventional circuit and water commissioning was successfully completed in two days.

“Initial feed grades at New Britannia are significantly below the designed levels, but fit within the longer term mine plan,” Stieper said. “Due to the Jameson Cell’s ability to upgrade to such high levels, the client is extremely happy with their performance and especially their ability to deal with widespread ore variability. Feed grades are commonly in the range of 0.5% to 1% copper, whereas the design grade was 2.5%. Significantly higher talc and other highly floatable gangue minerals in the feed are challenges that the Jameson Concentrator is effectively dealing with.”

Jameson Cells have also recently been commissioned at Marcobre’s Mina Justa operation in Peru and Newcrest’s Cadia mine in Australia. At Mina Justa, preliminary results have shown that the Jameson Cell, in a cleaner scalper duty, produces copper grades between 60%-65% with recoveries more than 80%, greatly exceeding expectations. The Mina Justa team also found that the cell is recovering native copper at fine and coarse particle sizes, as well as copper oxide. This material had been previously deemed unrecoverable using conventional flotation cells.

Stieper added: “Cadia is currently coming toward the end of commissioning for its dedicated molybdenum flotation circuit, which consists of Jameson Cells in roughing and cleaning duties. The Jameson Cell molybdenum rougher was able to achieve grade and recovery targets on the first run of slurry commissioning, and the cleaners have achieved final concentrate molybdenum grade even with the regrind circuit yet to be in operation.”

FLSmidth’s coarseAIR Pilot Plant at the company’s metallurgical laboratory in Salt Lake City, U.S. (Photo: FLSmidth)

HOSTAFLOT for Safer, More Efficient Flotation

The other pieces of the puzzle are chemicals. Today’s flotation reagents are more highly customized than those used 10-20 years ago and are therefore much more efficient.

Wagner Silva, global head of technology for mining solutions at Clariant, joined the discussion. “Sustainability was not a factor 10-20 years ago, and currently it is a primary factor that customers are interested in,” he said. “Products such as xanthates, which were the industry standard 10-20 years ago, are increasingly being replaced by safer, more sustainable options such as Clariant’s HOSTAFLOT 7000.”

HOSTAFLOT 7000 has recently been used to replace a xanthate collector at a copper mine in South America and has helped to reduce the plant’s overall reagent consumption. It’s liquid, water-soluble and non-flammable properties are more favorable than those of the xanthate product and this, combined with stability even at high temperatures, plus its ability to reduce collector consumption by 40% have proven a winning combination.

The hazardous classification of xanthate collectors and difficulties with storage, handling and disposal, mean that many sulphide mining companies are facing increasingly difficult logistical challenges. For this reason, the mining operation was looking for a replacement to the potassium amyl xanthate collector it used to produce enriched copper and gold.

The company mines bornite and chalcocite as prominent copper-bearing minerals with chalcopyrite occurring in lower percentages. Gangue material is comprised of silicates and magnetite with a low carbonaceous content. The average mined copper grade is 0.7%-1%. Gold is also present in the ore at a feed grade of 0.5 g/t and is enriched through flotation.

The mined ore is processed through a primary gyratory crusher and secondary cone crusher circuits. It is further reduced by a high-pressure grinding roll and screened. The undersize material feeds a classification cyclone, which then sends the 150 Tyler Mesh fine fraction to flotation and the coarse fraction to ball mills.

Rougher flotation is completed in tank cells at 42% solids. The rougher concentrate goes through regrinding in vertical mills, which feed a cleaner bank. The rougher tailings are sent to the tailings dam. Using potassium amyl xanthate and dithiophosphate as collectors, the final concentrate had a copper grade of 40%, with 86%-88% copper recovery and 66%-68% gold recovery.

Clariant’s R&D team developed and tested several chemistries from the HOSTAFLOT collector series, using the customer’s ore as feed material. One of the chemistries developed, HOSTAFLOT 7000, exhibited excellent collector results in lab trials, and Clariant recommended it for validation tests at the customer’s facilities.

Laboratory trials conducted by the customer showed satisfactory results and approvals for an industrial trial were obtained. Clariant supplied 4 metric tons of HOSTAFLOT 7000 for the plant trials, which included four different time periods to ensure robustness toward ore variability.

During the plant trial start, HOSTAFLOT 7000 replaced the dithiophosphate collector and dosages were gradually increased to replace the xanthate. A 40% reduction of total collector consumption was achieved using HOSTAFLOT 7000 as the single collector replacement. As a side benefit to switching to HOSTAFLOT 7000, frother consumption decreased by 25%.

“Copper and gold metallurgical recoveries throughout the HOSTAFLOT 7000 trials were equivalent to that of the xanthate collector,” Silva said. “A reduction in reagent consumption proved that HOSTFAFLOT 7000 was a suitable replacement for potassium amyl xanthate.

“Since HOSTAFLOT 7000 met the mining operation’s objectives of achieving copper and gold target recoveries, while reducing overall collector and frother consumption, it is now the reagent of choice for the mine.”

Eriez’s HydroFloat is now being accepted as a mature industrial technology by a number of mining companies. (Image: Eriez)

Clariant Tackles Tailings

Clariant is also working on solutions to reduce the quantity of valuable minerals sent to tailings and to reprocess legacy tailings.

In September 2021, Clariant Mining Solutions launched its Tailings Management Program and opened a new global Competence Center for Tailings Treatment in Belo Horizonte, Brazil. This supports the industry in developing solutions for tailings treatment along four technical platforms: flotation, magnetic separation, dewatering and rheology modification.

“In order to float tailings, new flotation reagents are needed,” Silva said. “For example, slimes flotation requires tailor-made chemicals that allow increased dosages and particle hydrophobicity without affecting selectivity, froth stability and overall performance.”

To achieve this, Clariant’s application and development teams are partnering with customers to develop and test special collectors to reduce ultrafine particle losses and to recover value from tailings. Clariant has developed FLOTINOR 5530 specifically for ultrafine iron-ore reverse flotation, and flotation tests have shown that, although higher dosages of collector are required in comparison to tests with conventional flotation feed (with larger particles), tailings flotation with FLOTINOR 5530 yielded a 64% iron-grade concentrate with 30% better metallurgical recovery and half of the dosage compared with tailings tests with FLOTIGAM 7100. Additionally, it was possible to decrease the silica grade in the concentrate by increasing the FLOTINOR 5530 dosage without lowering metallurgical recovery below 40%.

Silva added: “The electrification of transportation is also driving the growth of battery minerals, including nickel and lithium, and Clariant has recently commercialized new collectors for these applications too.”