Nancy Bartels is Control's managing editor. You can her at
[email protected] or check out her
Google+ profile.Some 50 km north of the Arctic Circle in the Lapland region of Sweden is a giant hole in the ground. It's 3 km long, 1.5 km wide, and 250 m deep. This is the
Aitik copper mine. About 15 km from the town of Gällivare, it is one of the largest open pit mines in Europe.
Owned by the Boliden Group, which operates mines and smelters in Sweden, Finland, Norway and Ireland, the mine recently completed a massive expansion and modernization project. The price tag for Aitik's upgrade was $790 million, but it's enabled the mine to double its production capacity, extend its life until 2030 and add molybdenum to its list of metals produced.
Aitik's ore is not especially high-grade. It's 0.25% copper, 0.1 g gold per ton and 2 g of silver per ton, but still worth the investment in digging it up. It's not just the market value of the minerals that makes the investment worthwhile. The upgrades Boliden has installed are expected to reduce life-of-mine cash costs from $0.80 per pound to $0.43 per pound, and have raised production rates from 4.3 tons per man hour to 5.5 tons per man hour. Efficient, trouble-free operation is crucial to Aitik's long-term success.
Crush, Shake, Stir
The Equipment List
The modernization project at Aitik is appropriate to the size of the mine itself. ABB has provided:
- 650 motors for conveyors, pumps, fans, crushers, grinders and process equipment
- 230 drives and variable-speed drives to control the electric motors
- Two 22.5-MW, gearless mill drives to power grinding mills
- Two 2 x 5-MW, dual-pinion drive systems for ring-gear mill drive (RMD) mills
- Four 1.4-MW, permanent-magnet motors for slurry pumps
- Process control system (Extended Automation System 800xA)
- 23 distribution transformers for drive systems
- Three 80 MVA power transformers for substation
- Gas-insulated switchgear (170 kilovolt) for substation
- Harmonic filter system for the complete plant
- 201 cubicles of low-voltage switchgear (400-690 volts) for distribution of power across the site.
Once a week at Aitik, a blast produces enough ore for the operation to process 106,000 tons each day. The unprocessed ore is loaded onto 100-ton trucks, which deliver it to a crusher deep in the pit. The crusher reduces the ore to 30-cm boulders, which are then transported by underground conveyors to a storage area above ground. From there, a 7-km conveyor moves the rock at 4 m/s to the concentrator plant, where two 22.5-MW gearless mills grind it down to sand at the rate of 4400 tons per hour.
Then the sand goes into flotation tanks filled with reagents, foaming agents, compressed air and chalk, where 500,000 liters of water are added each hour. This treatment separates out the valuable copper, gold and silver ore, which floats to the top. The resulting chalcopyrite concentrate, which is 25% copper, is then transported by train to Boliden's smelter in Rönnskär, 400 km away.
An operation this size has a lot of equipment to be maintained. In addition to the new concentrator, surface crusher and the 7-km conveyer between them, the site has pipelines to its water reclamation stations, pumping stations, a welding shop, a truck garage, administration buildings and a recycling station.
The operation is controlled by a System 800xA from ABB, and to support maintenance of the facility, designers integrated a Maximo enterprise asset management (EAM) system from IBM with it.
Finding Faults