The Mittersill mine in Austria is a complete outlier in the Western mining sector: a mine owned by a tungsten consumer on the edges of a national park with an openness to testing new mining equipment prototypes in a varied underground hard-rock setting.
Pulling up to the Wolfram Bergbau und Hütten AG-owned mine, in Salzburg, Austria, it looks more like a remote ski chalet within the Alps.
This is by design, as Stefan Eggenreich, Mine Manager, explains: “The agreement with the local authorities is that whatever surface infrastructure we have in place can be deconstructed and removed within a maximum of two months. The surface footprint, as a result, has to be minimal.”
The origins of the mine are on surface however, with an outcrop of scheelite discovered at a nearby peak on the mountain in 1967. An open-pit mine development followed, running from 1975-1984, with an underground mine commencing operations in 1978.
That underground mine has operated continuously since then aside from a two-year period in 1993-1995 where it was placed on care and maintenance due to subdued pricing for tungsten oxide (WO3).
With an average grade of 0.25% WO3, Mittersill is considered relatively high grade by European standards. The fact that the mine and concentrator can handle significant volumes of material over 500,000 t/y with a lean team of 94 employees highlights the efficiency of its tungsten operations. This workforce keeps the mine and plant running smoothly five days a week.
“The reality is that many of our mine personnel are able to carry out multiple jobs,” Eggenreich says. “We train them up and give them a skillset to make sure the critical functions of the mine can be covered with minimal people regardless of the pricing environment around us.”
Mittersill is a “large-scale operation” by Wolfram’s reckoning, with some 80 km of tunnels already developed – a number that is expanding by, on average, 2.4 km a year. Mining is carried out by methods such as sublevel caving and stoping, plus cut and fill methods, with some of the mined rock getting up to 350 MPa in terms of uniaxial compressive strength.
When IM visited the mine in mid-November, it could call on eight Sandvik loaders (LH517 and LH517is – one pictured below), two Sandvik DD422i development drills, one Sandvik DL432i production drill rig and one Sandvik DS411 bolting unit. Trucking is carried out by a local construction-focused contractor that supplies 30-40-t-payload trucks for the LHDs to load into. This included at least one ADT from Volvo (an A30G). Eggenreich explained that the company uses only a percentage of the LH517s at any one time, with the other loaders acting as back-up replacements should one go down.
Around 17 stopes, ranging from 20,000 t at the bottom end and 270,000 t at the top end, are in operation at any one time.
Mittersill conducts delayed backfilling of stopes amounting to some 100,000 t/y, 90% of this being “straight” backfill and the remainder being paste backfill. It consumes some 5,000 m of shotcrete a year, while placing 4,000 m of cable bolts and 4,000 Omega bolts into the tunnels as ground support.
The operation – which has two crushing and grinding plants currently – transports this material via a 3.2 km conveyor to the processing plant where a series of ore sorters and other processing equipment turn the ore into a saleable product.
Mittersill is already Europe’s biggest tungsten (scheelite) mine, contributing around 25-30% of European tungsten ore production, but Wolfram has plans to increase production volume further over the next five years.
Optimised underground handling
As mentioned, there are two crushing and grinding plants positioned underground at Mittersill: one that previously operated in an LKAB mine as long ago as the 1960s and one that has only just been commissioned.
To meet the challenges of deeper mining and longer transport routes, the company commissioned the latter – a state-of-the-art Sandvik processing plant – to enhance efficiency, reduce cost and support sustainability.
As the mine has developed and tungsten ore is extracted at greater depths, transporting materials uphill has become an increasingly difficult and costly feat. As a means of rising to the challenge, Wolfram constructed a cutting-edge crushing and grinding plant approximately 800 m below ground, to ensure optimised material handling and a reduced environmental footprint.
Eggenreich said: “Building this facility underground has been a game-changer for us. It aligns with our vision for sustainability as well as our commitment to operational excellence.”
The processing plant integrates equipment from Business Area Rock Processing at Sandvik including a CJ815 jaw crusher and CS840i cone crusher to ensure consistent particle reduction. These are complemented by reciprocating feeders and vibrating screens to efficiently transport and process raw ore, while heavy-duty hydraulic needle gates and a bunker system enhance safety and reliability. The plant is also fitted with remote controlled rock breakers for breaking up oversized material.
The crushed material is then lifted 300 m by a vertical conveyor, with Eggenreich mentioning that a Mincon RD3 raisebore was used to construct the vertical conveyor shaft.
“We also looked at a skip hoist system, but the vertical conveyor was so much lower in cost,” he said. “Now we have the new crushing system in place and can accurately predict the size of material being loaded onto this conveyor, this system is working very well for getting material to surface.”
The plan, he added, was for this plant to be remotely operated in the future.
Integrated innovation
Sandvik AB became the owner of the Mittersill mine in 2009 when it acquired Wolfram, effectively integrating a tungsten supply chain that sees concentrate from Mittersill turned into tungsten powder and eventually tungsten carbide for improving the life of drill bit threads on Sandvik drills and cutting tools for Sandvik Group.
“Considering how volatile the tungsten market is, belonging to Sandvik Group gives us a robust, stable platform to better manage risks and plan long-term operations,” Eggenreich says.
Lars Kröger, Key Account Manager & Sales Professional Underground Equipment, at Sandvik Mining, told IM: “Mittersill plays an essential role in supplying the Sandvik Group with tungsten, so it secures a certain amount of its tungsten need, and it is mined under the highest standards and does not need to be imported from overseas.
“Additionally, Mittersill is a perfect example of a modern, sustainable mine. The nature around doesn’t get threatened and you don’t notice there is a mine underground unless you were told otherwise.”
These credentials are important in a strategic commodity like tungsten.
Wolfram, itself, is the only integrated tungsten melting plant outside of Asia and Russia, and houses expertise spanning the entire production cycle, from mining scheelite ore to recycling tungsten-containing materials, ensuring a closed-loop supply chain.
It has set ambitious goals in the Strategy 2030 focusing on extending its recycling offer to support Sandvik’s target to increase waste circularity to 90% by 2030.
Innovation at Mittersill goes beyond the recycling methods used or the TOMRA Mining ore sorters and supplementary digital systems it has in the plant to identify economic levels of scheelite more accurately.
Mittersill has become a major test bed for Sandvik Mining to put its equipment through its hard-rock paces.
The variability that may make it hard to mine in a uniform manner acts as a great environment for vehicle testing, according to Kröger.
“As it is a hard-rock mine with different mining methods, like sublevel stoping, sublevel caving or cut and fill, it offers us a good variety of mining setups,” he said, providing a list of equipment such as a Toro
TH551 truck, DL432i production drill, DD212i development jumbo and MX650 hard-rock cutting machine. A Sandvik narrow-vein loader is also being lined up for a trial in the mine, while the Sandvik Tampere team are planning to visit to test out a new greasing system for the mine’s Sandvik DD422i.
All these vehicles are tested out by Sandvik within the normal production environment at Mittersill, providing the ideal equipment testing environment for accurate and valuable feedback for further development.
Wolfram explained: “Mittersill’s inhomogeneous geological environment provides a wide range of rock types and strengths – from talc-rich zones with a compressive strength of around 50 MPa, to quartz-rich units exceeding 300 MPa. This diversity ensures prototypes are tested under varied and challenging conditions.
“Additionally, the mine features long tramming distances with a 15% incline, where trucks must travel fully loaded uphill. These demanding haulage conditions create an excellent real-world environment for evaluating equipment performance and durability.”
Eggenreich (pictured below) says the operation is happy to support testing like this with accompanying Sandvik personnel, saying that machines tend to be trialled for upwards of six weeks at the mine.
He added: “We do our best to support this testing; in fact, we have a great challenge for the next-generation MX650 hard-rock cutting machine in mind already!”
While no battery-electric Sandvik equipment has yet been tested at Mittersill, IM was transported in an electric personnel carrier. And Eggenreich explained that all new working areas were being reinforced with new power supply to facilitate the use of battery-electric equipment in the future.
“We haven’t set a date for testing of such equipment, but we are preparing for the future,” he said. “Sustainability is a key metric for Wolfram at Mittersill, so we are exploring all options to reduce diesel particulate emissions.”
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