On March 2, Metso Corporation and Loesche GmbH announced a landmark partnership agreement to introduce groundbreaking Metso Loesche vertical roller mill (VRM) dry grinding technology for a wide range of minerals processing applications. Now part of the Metso Plus offering, the Metso Loesche VRM can replace high-pressure grinding rolls (HPGR) and horizontal mills in primary and secondary applications and tertiary stirred mill applications, while at the same time simplifying the process and bringing savings in energy consumption and operating costs.
Christoph Hoetzel, Senior Vice President Grinding Business Line at Metso (left) with Managing Director of Loesche, Rüdiger Zerbe (right)
Downstream processes benefit from improved mineral liberation and steeper particle size distribution. Furthermore, advanced flow sheets incorporating coarse particle flotation, magnetic separation or other coarse beneficiation technologies can be facilitated, further reducing or even eliminating water consumption if fully dry processes are feasible.
The Metso Loesche VRM technology also features advanced wear materials to meet the demands of mineral processing applications and ensure high operating availability. Advanced process control is integrated to ensure optimum operation, easy stop-start, and rapid ramp up.
To get some more insight into the background of the partnership, and its potential in future flowsheets in mining, IM Editorial Director Paul Moore spoke to Managing Director of Loesche, Rüdiger Zerbe; and Christoph Hoetzel, Senior Vice President Grinding Business Line at Metso.
Q Loesche has a famous heritage in the cement sector but has been active in mining for some years – a good example being the Loesche Ore Grinding Plant (OGPmobile) deployed with New Steel for iron ore processing in Brazil. But this partnership with a global mineral processing technology company like Metso has the potential to bring Loesche Vertical Roller Mill (VRM) technology into mining at scale. Can you give some idea of the Loesche journey and indicate how significant a step is this?
RZ You are correct that we have been active in mining, and successfully, but our major business and what we are mainly known for, is the use of our VRM technology in limestone grinding for cement. Today we continue to offer I would argue the most advanced and efficient VRM solution in that industry. Our heritage goes back to 1906 with the very first Loesche mill patented in 1927. It featured a rotating grinding track that used centrifugal force to push the grinding stock outwards from the centre of the mill. The first four-roller mill went into operation in a plant near Naples in Italy in 1971 with a throughput of 214 t/h. With an increase in the size of the rollers and the grinding table, throughput of 425 t/h was achieved when the next generation was launched in 1975. In the 1990s, Loesche made another world record delivery with the sale of a 750 t/h raw material mill to a customer in Thailand. Moving to the 2000s, the Loesche Mill type LM 69.4 and LM 69.6 with product throughputs of up to 1200 t/h were sold to many customers. Sales of Loesche VRMs now exceed 2,400 units. But we also wanted to achieve the same success in mining where we believe the potential benefits are just as great – and Metso very much shared our vision on that, especially relating to efficiency and sustainability. The benefits are significant in mining – up to 40% energy savings, enabling fully dry and reduced-water processes and of course removing the need for grinding media. Efficient compressive grinding pressure and shear between the particles ensure that energy goes directly into breaking them apart, which reduces the amount of energy needed for grinding. The entire grinding system is under negative pressure, including the built‑in classifier which immediately removes fine material. This prevents overgrinding and avoids unnecessary internal recirculation. Together, these features allow for a very high reduction ratio, making single‑stage grinding possible and removing the need for multiple grinding and classification steps.
A potential system layout incorporating the Metso Loesche VRM
CH The world needs more resources, but the increased supply of mined materials must be done in a sustainable way. At Metso, we always keep an open mind on what is new and what has potential. We are already at the forefront of matching mineral processing technology combinations to get the lowest possible energy consumption and the highest availability, such as with our stirred milling range. Technology really can make a difference for our customers and the customers themselves are more open to new thinking for flowsheets. Today, the consideration of HPGRs – in our case the HRCe, is in most of the plant design conversations that we have with engineering houses and mining groups – we have sold a lot of them in recent years, and they are the right option in many cases. But there are always nuances – the HPGR is great when it comes to energy efficiency, but they do make the plant more complex than a conventional SAG and ball mill circuit. When we looked into what other technology could bring another alternative to the HPGR for certain projects, it was clear – vertical roller mills were the right option to eliminate some of the downsides of dry grinding systems. VRM plants bring many benefits such as simplified space, with its very compact layout, combined with energy efficiency and lack of water requirement. When we looked at the right VRM partner, Loesche was clearly the number one in the field and the inventor of the technology; so, for us this was a great match – and we are excited to move ahead with them.
Q What is the depth of the relationship commercially – will any requirement for Loesche VRM technology in the mining space now be handled jointly via this partnership and the Metso Loesche VRM? And are you defining mining as anything not cement related including industrial minerals for example? And will there be any design evolution of the Loesche VRM jointly between the two companies for the mining market such as to allow higher throughputs?
RZ Yes – the partnership will have exclusivity when it comes to mining projects which as you say encompasses the full suite of mining application. In terms of the design – we are talking about proven technology. That said, there will be step by step improvement and customisation based on the specific mining applications that arise, and this is what we are doing and will do jointly together.
CH Two other points – there are more than 2,400 Loesche VRMs working, and some of them already have very large throughputs as they are operating at some of the world’s leading and largest cement operations. In addition, in terms of our cooperation, this will include not only the VRM based grinding, but also holistically working together to make sure the Metso Loesche VRM works as part of the complete process flow from crushing to flotation to magnetic separation, because it will have a huge positive impact across the flowsheet. So, we will together fine tune the VRM grinding on a project-by-project basis, as we would do with all our 
mining projects anyway – but also look to optimise the overall VRM based process. At Metso we really see a lot of synergies between Metso and Loesche – another one could be looking at ways Loesche could benefit from our global manufacturing network to produce the VRM mill linings and components for example.
The Metso Loesche VRM classifier section
Q Can you go into the key benefits of the Metso Loesche VRM in mining in more detail?
RZ I think OPEX is an important one as well – the already mentioned savings of 40% in energy is a huge benefit – but also the lack of grinding media requirement is a major OPEX saving; and is much more sustainable as no steel balls need to be forged. As a dry process, or nearly dry in some cases, it can also have a major cost and sustainability in water scarce regions – where most of the largest copper mines are located, for example. In CAPEX terms, the VRM is probably comparable if you are taking just the equipment itself into consideration – but when you also look at its smaller footprint – this brings another cost advantage as well; and many mining projects are space limited, especially if it is a plant expansion on a brownfield site.
CH Thanks to its efficient grinding mechanism, the Metso Loesche VRM can deliver significantly improved mineral liberation which produces a steeper particle size distribution with minimal fines, and it reduces sulphide oxidation compared to traditional milling technologies. This enhanced liberation directly supports improved downstream recovery, enabling concentrators to extract more value from the same ore. As a result, VRM operations can achieve up to 7% better flotation performance and therefore better recoveries, translating into higher overall plant efficiency and increased profitability. No grinding media also means no introduction of impurities from the media.
Q At Metso you have a whole suite of grinding and milling technologies at your disposal – stirred mills, geared mills, gearless mills, HPGRs, Vertimills – where is the VRM niche or sweet spot and what would you say was an ideal VRM based project and when you would propose its use to a big EPCM for example?
CH At Metso we want to give the customer the best solution not just from a pure mineral processing point of view but also based on a holistic view of energy efficiency, wear part consumption, equipment availability and total installed cost– that is important for the TCO. So, taking all this into account we look to find the right combination of equipment for the project. And yes, that could be a Vertimill or an HPGR which we have included in some big contract wins in recent years. We want to overcome a bias that says that the most energy efficient plant is also a more expensive and more complicated plant to build. We always strive to make things more simple and not more complicated, so for example, while we offer primary, secondary and in some cases tertiary HPGRs – we don’t need to recommend complicated multi-stage HPGR processes, which in our view result in high cost and footprint as well as operational complexity. The simpler the process the easier it is to maintain in most cases – and the easier it is to achieve maximum availability. We have many recent cases where we have been successful with technology combinations achieving exactly this. And when a mining client is planning on a dry process, it is a no brainer to use this Metso Loesche VRM technology – for all the reasons we have given. Then there are the mentioned benefits in the downstream processes, so that is a complete game changer as well. So, we are excited to get this innovative technology into mining flowsheets as it fits our Metso philosophy perfectly.
The complete Metso Loesche VRM design
Q Mining groups and to some extent EPCMs are known for being conservative and opting to often stick with tried and tested conventional approaches. How will they be convinced?
RZ Mining needs to do things better than it has done in the past. And finance is part of that. A major challenge for mining customers today is first they need to get the project off the ground financially. So, they need to consider not just the process but the capital that is involved in all this. The Metso Loesche VRM offers a lot of advantages at less or similar CAPEX compared to conventional comminution circuits. Another aspect is that it is harder to find skilled people for roles in mineral processing operations – and that is not going to get any easier. The Metso Loesche VRM can be run autonomously or with a high degree of automation. The Metso Loesche VRM offers a compact footprint and simplicity in the flowsheet combined with the lack of grinding media, reduced energy costs, reduction or elimination of water and better performance of downstream steps.
CH Maintainability is another point I want to make – when we looked for a VRM partner, something that struck us was how much emphasis has been put onto the maintainability of this equipment by Loesche and the long history they have of operating often very large VRMs in the cement sector with minimal unscheduled downtime. From smaller up to large VRMs, Loesche is consistently delivering 50 to 60 mills every year. Plus, when we looked into some of the materials their VRMs were already handling – such as blast furnace slag, the abrasiveness of the material is not so much different to some of the more challenging mining applications that we could encounter – magnetite ores for example.
Q What convinced Loesche this was the right move into mining with Metso as the partner? And how will front facing sales work with mining customers?
RZ We talked with Metso for over a year quite intensively on this agreement and their commitment like us to sustainability really stood out. Not only that but it is clear in the market they are a leader not only in market share in many key areas but also in technological innovation and development – flotation being a great example in both fine and coarse particle flotation innovations they have developed. Additionally, as part of the negotiations we really experienced the teams on both sides working well together – they understand each other and we are already working like one organisation on this project. And finally, we are a family company and so we have a long-term vision – we are in this for the long haul, so we wanted a long term and committed partner – it was clear to us that Metso was offering us that.
CH As to the question on sales, Metso will take the lead with sales and contracts as well as the marketing – customers will still see us as their contact point just as they would with our other product lines. This also makes sense given our existing installed base in mining and our global network in mining hubs – including related to service and aftermarket. But in terms of the project based technical work and the wider flowsheet, Loesche will be a close partner and in that way, we will work as one team. Loesche retains the VRM IP and the equipment will also continue to be manufactured by Loesche – though there may be opportunities to carry out assembly and other works at global Metso centres, and to utilise Metso facilities for liner and component production as already stated. We are just starting on this journey so to some extent we will learn as we go, but this is the starting point.
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