The Swedish city of Kiruna lies 90 miles north of the Arctic Circle and boasts the world’s largest underground iron ore mine. Writes David Shirres from Kiruna
On May 21, Swedish mining company Luossavaara-Kiirunavaara AB (LKAB) celebrated the opening of the mine’s newest production level in a glitzy ceremony 1,365 metres below ground.
Sweden’s Minister of Enterprise and LKAB’s contractors were invited to see the new level, which lies 320 metres below the existing chambers.
The project, which began in 2008, represents an investment of £1.24 billion and required the removal of 4.3 million cubic metres of rock.
The new level includes a locomotive workshop and is capable of producing 35 million tonnes of ore per year for the next 15 to 20 years.
Among the project’s suppliers was Bombardier, whose Interflo 150 system controls the rail network at the bottom of the mine.
The system is standard gauge, compared with 891mm gauge on the production level above. The new trains have 21 wagons and carry 650 tonnes of ore from the loading chutes to the crushing plant unloading station. Here the train is suspended on rollers as ore is dropped into 20 metre deep pits. The trains are hauled by locomotives supplied by German mining locomotive manufacturer, Shalke.
These 108 tonne, 900 kW locomotives are powered from a 750V dc catenary or by batteries. When the new level is fully operational in 2017 there will be 10 loaded train movements an hour between its 10 loading chutes and four crushing chutes on a 15 km rail network. Currently only three of the loading chutes are operational.
Bombardier’s Interflo 150 is a Communications Based Train Control (CBTC) system which maximises throughput by variable moving blocks.
It incorporates Automatic Train Protection and Automatic Train Operation to control the mine’s driverless trains – similar to the Cityflo 650 system that is to be installed on London Underground’s Sub Surface lines.
Interflo 150, however, includes features adapted for mining operations, in particular its automatic route setting, integration with loading and unloading, and compatibility with whatever radio system is used in the mine.
In an official announcement for the opening of the mine’s seventh main level, Hans Engberg, LKAB’s project manager, said: “This is an unusual project; partly due to its size, but also because it extends over such a long period.
“From the pre-project phase to completion, we’re talking 12 years. This has placed special demands on our organisation and planning.”
Speaking to Global Rail News, Engberg explained that a detailed study had shown that, of the various options, a railway was the most cost effective way to transport ore underground as it offered a high degree of automation. Standard gauge had been chosen to reduce spillage.
He also advised that conveyors were not used because they are best suited for the evenly graded material obtained after the crushing operation. In the Kiruna mine, the crushing plant was in stable rock one kilometre away from the mining face.
