CONTINUOUS CUTTING has been delayed by COVID-19 . Delivery to Lucky Friday is expected in 2022 .”
There is also a possibility that the 40V may be used in combination with a new drilling and blasting method the Lucky Friday team has been testing , which , Hecla says “ controls the seismicity of the mine by blasting larger areas ”.
Either of these methods – or a combination of the 40V and the new drill and blast process – could potentially increase its tonnes per day by 30-40 %, approaching the limit of its milling capacity , Hecla previously said .
Marcus Eklind , Epiroc Global Business Line Manager – Mechanical Rock Excavation , told IM that the machine in question was currently in storage in Sweden awaiting shipment to the US .
One of the subsystems that has been redesigned following testing in Sweden at Epiroc ’ s Kvarntorp facility in 2020 is the dust suppression module . This new addition – which is likely to be used in future Mobile Miner machines – boosts the capacity by 50 %, improving the working environment for operators , as well as reducing the occurrence of maintenance issues that could arise from excess dust ingress .
The Mobile Miner 22H Epiroc has manufactured , meanwhile , is in South Africa awaiting clearance on a second trial with Anglo American Platinum . It was previously tested at the Twickenham PGM mine in Limpopo Province , South Africa , where it advanced at over 10 m / d in 140-150 MPa UCS rock . The mine was placed on care and maintenance before the trial could be concluded .
The low-profile machine , suitable for applications when a tunnel as low as 2.2 m is required , has been refurbished to suit the new application at one of Anglo Platinum ’ s underground PGM mines . It is currently at Epiroc ’ s Jet Park facility .
“ Discussions are ongoing about how to deploy the machine at a test site ,” Eklind said .
Both these machines – the 40V and the 22H – have been equipped for specific applications , which required some tailoring of the cutting components .
“ We are developing a modular system so when we are up and running , in terms of more orders , we will be able to produce these cutting segments much quicker and at a lower cost than currently ,” Eklind said . “ While there are geological similarities between many deposits – silver-lead mines , for example – that is not the case in South Africa ’ s Merensky Reef . Hence , we must adapt the machine to ensure best performance .”
Beyond the two machines the company has built , Eklind said Epiroc has registered much interest for its mechanical rock excavation philosophy which , with its steel disc cutting technology , is reminiscent of traditional TBM development .
“ The majority of companies we speak to are looking for a 5 x 5 m machine , which would effectively be a 50V machine ,” he said . “ There is one mining company and one underground storage facility company that we are exploring options with more specifically . The latter is looking at a very specific machine to cut a very specific profile to fit their needs .”
He expanded on this intriguing application : “ They are less interested in the productivity of the machine and more the quality and ‘ surface ’ the machine creates and the lack of damage to the surrounding rock compared with traditional drill and blast techniques .”
The mining company – a base metal-focused firm – is considering use of a rock excavation machine for infrastructure purposes , which is different to the two ongoing trial projects Epiroc is engaged with .
“ If you look at mechanical rock excavation , in general , the machines have applications in waste rock or infrastructure , or ore ,” he said . “ They are not constrained by application .”
Adapting the TBS
It is a long time since Rio Tinto sold off the Mobile Miner TBS Tunnel Boring System originally built to support the miner ’ s future block caving plans by Atlas Copco Rock Drills ( today Epiroc ).
Sweden-based contractor Bergteamet AB became the owner of this machine – able to continuously make reinforced tunnels with a size of 5.5 m x 5.5 m , down to a radius of 65 m and with a flat floor – in August 2017 .
The TBS , previously rebranded by Epiroc as the Mobile Miner 55V , is now being leased to Dividend Industries AB , with former Berteamet CEO , Urban Holmlund , through his company , UHKAB , responsible for harmonisation of technology and applications being researched by Dividend Industries .
Dividend Industries is a capital and human aggregation of businesses focused on engineering , the building industry and building materials , food processing industries , wood and furnishing , specific products and services .
Its plans for the TBS are tied to the work it is carrying out with Sweden ’ s Uppsala University , Slovakia-based renewable energy-focused company VUNAR and other partners on “ cost effectively penetrating the Earth ’ s crust at depths of up to 3,500 m underground ”.
President Alexander Zvrskovec confirmed to IM that the company has plans to use the TBS in two potential applications in Sweden and Slovakia under the group ’ s wide remit .
It is preparing work on a deep mining project in Slovakia , with the help of the country ’ s Technical University of Košice , and a deep geothermal application in either Sweden or Slovakia .
“ In both cases , we will work in either granite or granodiorite ,” Zvrskovec said , adding that the UCS of the rock the company is evaluating is around 160-240 MPa .
The TBS , with steel disc cutting technology , has been designed for mechanical excavation and has been developed for deep mine infrastructure , but Zvrskovec and the Dividend team also see the potential for the machine incorporating electro pulse technology for rock breakage in the future .
“ We are also developing a powerful electro pulse generator with a service interval longer than 4,000 working hours and a new kind of electric pulse , which could be submerged in tap water instead of present insulation liquids ,” he said .
“ Our ambition is also to test the electro pulse head on the 55V machine and compare its performance with the base cutting method ,” he explained .
“ We have measured electrical consumption for disintegration of 1 cu . m of granite and the electricity consumption is circa-5 kWh . If we can prove such low electricity draw , it will be a paradigm change for both the mining industry and for future deep geothermal energy plans ”
Zvrskovec and Dividend Industries are set to show off these plans – and more – at the Expo 2020 Dubai in January when it will present in the ‘ Global Goals ’ theme week .
The TBS , with steel disc cutting technology , has been designed for mechanical excavation and has been developed for deep mine infrastructure , but the Dividend team also see the potential for the machine incorporating electro pulse technology for rock breakage in the future
IM
NOVEMBER / DECEMBER 2021 | International Mining 75