TAILINGS
Metso talks tailings treatment
IM caught up with Piia Suvio , Director / Head of Tailings & Water PG and Process Development at Metso , to talk through filtration and thickening trends & market changes and Metso ’ s innovations and solutions which are helping address them
Q There is a lot of talk in the industry about very large filters as well as smart filters to help reduce overall footprint for very high tonnage operations plus optimise the dewatering process - what is Metso ' s take on the importance of a ) scale and b ) digitalisation when it comes to filters ? A You are correct that one of the reasons that we are going towards bigger filters is the reduction of footprint ie the floor area required but it also means more water savings . The upscaling trend – and the move to filtered tailings in general - is happening but maybe not as quickly as we thought it would . We at Metso also think there remains a market for thickened or paste tailings and that is not going to change – there are project suited to both and there is room for both . Back to the point on larger filters – our focus model for high tonnage tailings applications is the Larox ® FFP3716 pressure filter which has a a 2,000 m ² filtration area . It has the biggest plate made of a monoblock in the market – competitor filters use two plates that are bolted together . The feeding shoe in competitor filters is usually in the middle of the plate meaning usually there is manual work to make the shoe holes in the filter cloths – ours does not have that need so saves a lot of time . The way our filter is configured also means we can transport it in a normal ocean container . On your last question on digitalisation , the new Larox FFP3716 filter also has local data collection , and we can use this for in-depth analysis , for example statistical process control to understand the process better . We also carry out automatic weighing of the material and are able to analyse specific gravity and how much water has been recovered . All this can be used to optimise the filter operation such as the length of cycle and optimal moisture content based on the downstream filter cake handling process .
Q Filtered tailings have been seen a more costly option compared to conventional or even thickened tailings , part of which is due to a perceived requirement for conveyors . Is that view justified in your opinion ? A We see actually that filtered tailings can be the most attractive option when all costs and risks are considered . Firstly , I think it is important to talk about the water factor and in particular factoring in the price of water . Filtered tailings allows you to capture more water than other methods . So from that standpoint , in arid mining regions like Chile , the economics of filtered tailings can be quite positive . Secondly , in some places the regulatory demand is guiding the industry towards filtered tailings . Filtered tailings also tends to mean space saving . When we look at tailings projects we tend to look at the whole minesite and whole life of mine including volumes , storage requirements , service needs , topography and hydrogeological factors – and in some of these cases filtered tailings do come out on top . Finally I would say there is not the same bias against conveyors as before due to mines looking to reduce any kind of diesel haulage anyway , and they are of course electric .
Q On thickeners , how important are aspects like pre-engineering eg in your HRT-S solution , as well as modularity eg in your scalable Filtration Plant Unit in being able to meet current and future dewatering demand in the mining industry ? A With the Filtration and Thickening Plant Units ( different types and sizes ), we have productised the whole Plant Unit , optimising every step that we can – this includes shortening the engineering , especially the basic engineering . We have also preselected components and auxiliaries and planned in detail where everythng will be produced to really streamline delivery schedules . We have also optimised material take offs for the plant steel structures . We have found that customers and EPCMs also really like this ‘ black box ’ thinking of a whole flange to flange plant unit , as they can just work around it and feel confident
Piia Suvio that the Plant Unit will perform . As you say they are also scalable so we can add as many as are needed to reach the required capacity . Underlying everything of course is our past experience .
Q Until recently , paste and thickened tailings were touted as the future , with filtered tailings more recently being highlighted . From Metso ' s point of view , what is the right answers in terms of when each technology should be used and how much of it comes down to things like customer preference and climate ? A Paste and thickened tailings can be the right way to go – but it comes with some complexity in terms of getting the rheology right – if it is genuine paste or just paste-like , you have to have pipeline expertise and for disposal having the right beach angles and stacked geometry , for example . Paste pumping can also be challenging . The way we see it is that there any many factors that influence the right route . It can be very project specific , such as the particular concentrator plant set-up . There is no one right way – decisions just need to be based on thorough testing and looking at the site-wide details . Of course , the customer attitude to capex and opex spend is a major factor as well . It is also worth noting that a lot of tailings projects are related to mines which are running out of time with their existing wet Tailings Storage Facility , and due to permitting or safety reasons cannot build a new one or do more raises . Some mines are also looking to use filtration to reprocess their existing legacy wet tailings ; while other like in the lithium industry want to reprocess tailings for remaining mineral content . Metso is working on several cases at study as well as delivery phases on all these types of scenarios for customers .
Q From a Planet Positive point of view how is Metso through its filters and thickeners ensuring that customers can maximise both water savings and reuse as well as energy savings ? A Water is a huge issue today and we have a lot of expertise in the water space . When we talk about dewatering , we want to ensure that the recovered water is handled in an optimal manner – where should or could it best be used or recycled , and do we have to treat that water . If it is being recycled to a specific plant process like flotation , we need to consider the water chemistry to see if that will have any impact . We can link water management in the process to overall production efficiency , including flotation yields and recoveries . Our big picture approach to tailings and water is one reason we are seen as a good and progressive partner by customers . With Planet Positive we compare our performance to any general accepted base performance in terms of water use and energy use , and then we look to quantify any benefits our approach is bringing with savings . With our thickeners we have optimised the flocculant use as well as the underflow densities with our advanced feedwell system . I would like to also mention that as the industry , including us , is looking at more use of fine and coarse particle flotation , we are focusing on what potential benefits the future flowsheet can bring from a tailings point of view .
62 International Mining | APRIL 2024