FILTRATION & THICKENING
of suppliers also becomes a lot smaller due to the required interpretation of the material settling and compacting characteristics, especially for systems like CCD circuits that have multiple stages, where achieving a higher density underflow can reduce the number of stages.”
A notable order for FLS was for a new iron ore plant in India – where FLS is supplying a range of equipment, including eighteen 55 m diameter thickener mechanisms for different duties – for which the tanks will be concrete not steel. This raises a point – why are some thickeners supplied as steel tanks and some as concrete? From a cost perspective it is generally a lower price point for thickener tanks of this size to be built in concrete; but sometimes it depends on the costs for excavation and issues such as accessibility. For example, for a copper operation in Chile, FLS supplied one 55 m elevated bolted steel tank for the slimes thickening out near the deposition site but also a 55 m in-ground concrete tank with anchor channel bolted steel wall at the plant, which was for the flotation tailings. Gilbert:“ Part of the reason for this was that at the plant, ground conditions were such that it allowed for excavating out an in-ground tank but where the slimes thickener was located near to the deposition site, excavation costs were going to be way too high, so steel was the better option.”
Where does the top end in size currently lie?“ We have a number of projects right now where companies are looking at thickeners of around 65 metres in diameter. And the question always is, can you do a thickener with an elevated steel tank of that size? We’ ve actually done a 65 m tank in China, which today remains our largest elevated steel tank. But there’ s always a trade-off, as once you get to that size of elevated steel tank, it becomes extremely heavy, especially for high seismicity zones. And therefore, in a lot of instances, you maybe need to consider if it is cheaper to excavate and have a concrete tank- for which we have delivered thickeners up to 128 m in diameter. When it gets up to 70 metres with a steel tank, our opinion is you’ re likely always going to see lower cost with an in-ground concrete tank or anchor channel tank instead of an elevated steel tank, unless there are some extreme circumstances that dictate that an elevated steel tank is more cost effective.”
Gilbert added that when you look at high density or paste tailings- they are designed for a very high throughput tonnage, with a requirement for a high underflow percent solids, which typically demonstrates high yield stress, there are instances where the required torque you need on the thickener in combination with the throughput tonnage means you have to divide the thickening into two or even three smaller units. Currently FLS’ s most powerful drive delivers 16.3 MNm of torque with the C140P-6SD.
So what are FLS differentiators in the thickener market? Gilbert:“ Once you get into the handful of premium players, they are all quality options – but I would say that today we offer drives with up to 16.3 MNm of torque – so we could probably offer a single larger diameter thickener for a certain duty because of the torque requirement. Similar drives with a lower torque rating have also been used in the Alberta oil sands on 70 m diameter high-density thickeners for a number of years.”
Gilbert added:“ I would also say when it comes to high density and deep cone paste thickeners, we have a large and extremely varied proven installation list. There is a level of experience that comes with an installed base in knowing how to actually apply the technology and learning from operating installations.”
What about digitalisation and maintenance with regard to thickeners? Gilbert:“ We have capabilities to do this, but I would say when you look at real time prescriptive maintenance and monitoring, that thickeners are still lower on the priority list compared to for example, mills or screens or crushers, where you have a lot of vibration plus very high power inputs.” The FLS digital offer for thickeners includes AutoFloc closed-loop control to hold bed level, torque, clarity and underflow density as the feed changes, with PerformanceIQ ® connecting thickener and filter data.
Finally, retrofitting and upgrading remains an important part of the thickener market – and within FLS it is a substantial share of the thickening business. Gilbert:“ This includes upgrades of our own but also competitor machines in terms of a complete retrofit, but there’ s also many instances where a customer wants to repurpose the thickener for another duty or increase performance. For example, they want to see if they can get higher throughput based on modern feedwell and dilution technology, plus potential increase in drive torque due to increases in underflow solids concentration as a result of improved settling and compaction. The reason this is such a valuable part of the market is that it often allows them to increase the throughput at their plant within the existing footprint.”
FLS says that a combined E-Volute™ feedwell and E-DUC ® or P-DUC ® upgrade can deliver up to 46 % less water to tailings, up to 40 % less flocculant and payback inside a year, on any OEM’ s thickener. This work starts with an initial thickener audit- which is a comprehensive on-site evaluation of mechanical, structural, and process performance designed to identify bottlenecks, reduce flocculant consumption
& maximise underflow density or overflow clarity.
IM also caught up with Connor Frailey, Product Manager- AFP Filters at FLS. He says a filtered tailings circuit asks three things of its filter press: a cake dry enough to stack, the water back in the plant, and the availability to meet demand. The cake specification is set on the mine’ s own ore, in bench-scale test work at the FLS Minerals Testing and Research Center, and FLS has matched it at production scale, so what was designed is what runs.
The FLS AFP automatic filter press covers cake sizes from 900 to 2,500 mm, the 2,500 mm format holding up to 38 m ³ of cake at up to 15 bar. It returns up to 95 % of process water and runs at availability of up to 93 %: less fresh water bought in, more of the year filtering.
Frailey:“ That availability comes from the detail, and what was proven on the 2,500 mm format is cascading down the range. On the AFP2000, the media drapes over, so cloth changes pull no plates; flood washing directs water at the critical points of the plate; and cycle times stay low.”
The FLS IntelliPlate™ turbidity-detecting plate alarm system reads the filtrate leaving every chamber and alerts the operator to a torn cloth and the plate it is on, so the failure costs a cloth, not a damaged plate and an unplanned stop.“ Plates wear, and under plate exchange FLS ships a fresh pack and rebuilds the used ones at a service center, so the press stops for the change, not the rebuild.”
Frailey says FLS comes in at the flowsheet stage, alongside the operator and the engineers writing the design, and carries on through test work and commissioning into the running plant, optimising the cloth, the plates and the cycle, which is where the mine improves its cost per tonne.
Metso thickener and filter developments
Metso’ s filtration portfolio consists of 16 filter types and comprehensive services for various mining and industrial applications, with more than 5,000 installations globally, backed by the extensive know-how of Metso’ s Dewatering Technology Centre( DTC) and wide service network. The fully automatic Larox ® FFP( fast-opening filter press) pressure filters provide a reliable and optimised dewatering solution for concentrates, tailings and bulk applications. Larox ® FFP filters are part of the Metso Plus offering.
In April 2026, Metso received an order to deliver state-of-the-art filtration technology for Lloyds Metals & Energy Limited’ s’ iron ore concentrate filtration plants in Ghugus, Manikgarh, and Konsari in central India in the state of Maharashtra. The order value,
64 International Mining | OCTOBER 2026