Two 22.5MW gearless mill drives – thought to be the world’s most powerful – are to be installed at a copper mine in northern Sweden, under a $27m contract placed with ABB by the Boliden mining company.

The two 11.6m autogenous mills, due to come into operation at Boliden`s Aitik mine at the end of 2009, will each be able to grind 2,200 tonnes of copper ore every hour, doubling the mine’s capacity to 36 million tonnes per year, and extending its life until at least 2025.

Autogenous mills use large pieces of ore to grind down smaller pieces in a large rotating drum, until the ore is reduced to small particles. Each of  the ring motors that will drive the Aitik mills will be 20m high.