FLOTATION
concentrate, otherwise fluidisation will not function properly. So, the mechanical design of the equipment means that it dilutes the concentrate. So then that water needs to be removed from the concentrate for the concentrate to go to the grinding circuit and then return to the process. In our Sampo Cell, we don’ t have fluidisation water, we are just adding enough water for the flotation process, and the solid percentage that we are getting in the concentrate can go straight to the regrinding circuit. So we are skipping a dewatering stage. And on top of that we have a much simpler classification process when it is required, and often it is not required. These are simplifying the circuit a lot. And on top of that, treating that water from dewatering means additional equipment and additional cost and footprint in the plant.”
So where does Metso see the greatest initial potential? The demo plant is at a relatively small copper operation compared to the very large copper mines. Rinne:“ But we definitely wanted to test it with copper because if you look at the market potential for CPF, more than half of that will be for copper, as this is where the largest tonnages are processed and where the largest grinding circuits operate.”
Carvalho:“ In our opinion, if the biggest mines – both greenfield and brownfield- don’ t start using coarse particle flotation soon, they will not be in operation in the future, due to factors like low grades, comminution energy costs, limited space availability and water shortages, and crucially a move away from wet tailings storage.”
Where is Sampo to be installed to maximise results for the customer? Rinne:“ If the customers are looking for a big increase in plant capacity, then it must be in the beginning of the flowsheet. If they are looking to increase plant recovery or throughput, then it’ s in the end of the flowsheet for scavenging of tailings. Because tailings duty is the easier application at this stage, coarse particle flotation will first happen in plant capacity related use, and gangue rejection will happen in the medium term. It will also take time for the market to fully accept coarse flotation and to better understand the advantages but also the risks.”
Rinne and Carvalho said that in a tailings application, in most cases it will be possible to push more throughput as you can grind coarser with the existing grinding capacity. Some particles will be lost in normal flotation because there is insufficient liberation for recovery to occur in the main flotation circuit, but then in the scavenger or tailings stream Sampo will recover the remaining metal. Rinne:“ In most cases we will still be able to achieve at least 5-10 % capacity increase. In the industry already today, when the copper prices are high, mines already make more money by increasing throughput and decreasing recovery so there’ s a lot of opportunity for coarse flotation in these situations.”
Upfront, in the grinding circuit, there is potential to reject 50 % of the mass already before going to the final grinding stages. Carvalho:“ Even if we remove 30 % to 40 % of the total non-valuable mass at that point, we can create final tailings there already. So that is a game changer, not only for the potential capacity increase but because significantly coarser final tailings mean you can use a totally different approach to tailings processing, like dry stacking.”
Rinne:“ If you must classify the ore at the beginning of the circuit before CPF, it means that all the fines have to be separately processed in a conventional flotation circuit. If you, for example, have 20 % of the plant throughput going to the CPF, your gangue rejection is limited to what is going to the CPF. When feed classification is not required, the gangue rejection potential can be significantly greater, and it allows us to have a higher mass pull and achieve higher recovery. In all the gangue rejection applications we’ ve studied so far, we haven’ t needed classification at all.”
Metso did test work and simulation in a gangue rejection application without Sampo feed classification, where it was rejecting 45 %, which means Sampo had a 55 % mass pull, meaning you could increase the plant throughput by 82 %. Carvalho:“ So not classifying the feed has a huge impact in the potential of increasing the plant capacity. Practically speaking it is hard to increase a plant throughput by this order of magnitude in a brownfield situation but in a greenfield project, it means that the plant can process a much bigger tonnage of ore with a much smaller footprint.”
What does that plant look like from a comminution point of view? What type of comminution is ideal to maximise the potential of CPF? Rinne:“ In the gangue rejection upfront, the CPF will change the comminution strategy as well. The same equipment works, but we will target much bigger particle sizes, which will save grinding capacity or increase plant throughput. New Metso Loesche technology is also a very interesting alternative here. We will end up with a coarser first concentrate, and a Vertimill is then ideal for regrinding the CPF concentrate. All of this means a lot of saved cost and energy.”
FLS RFC continues to garner interest
Staying with innovative flotation cells, but for fine particle recovery, FLS says its REFLUX™ Flotation Cell( RFC™) radically alters perceptions of froth flotation performance. It operates at extreme levels of gas and feed flux, and fluidisation wash water to deliver up to tenfold higher throughput, with enhanced grade and recovery, all with a smaller plant footprint.
The high-shear pre-contacting spargers and inclined channels allow operation under air-flooded conditions, delivering high operational gas flux rates while reducing bubble size. This increases the available bubble surface area flux by a factor of four compared to traditional flotation cells, significantly increasing collision and attachment rates. Contact between bubbles and floatable materials occurs in a high shear rate environment, elevating recovery rates.
Lance Christodoulou, Global Product Director for REFLUX™ Technologies at FLS told IM:“ The RFC is a leading flotation technology but still relatively new in the industry. We are now seeing major interest because of its ability to shift the grade recovery curve and reduce the required flotation volume substantially, which has a significant CAPEX and OPEX impact. We’ re seeing improved performance versus conventional flotation in terms of both recovery and grade. This includes copper applications, where we completed trials with KGHM in a full-scale installation in Poland. This EIT RawMaterials funded project is now complete but now we have another major miner interested in using the full-scale cell we built for that work for moly flotation.”
In that specific application, FLS was able to reduce the required retention time by a factor of 10. So where the plant was utilising a retention time of 30 minutes, the RFC was able to achieve the same recovery and grade in 3 minutes.
International Mining | OCTOBER 2026