Surface miners boost bauxite in Guinea: technical innovation is helping Guinea to achieve more effective exploitation of its bauxite deposits, explains Kyran Casteel.(Mining)

THREE GERMAN SURFACE mining machines have flagged the kind of dynamic approach needed to boost the effectiveness of Guinea's bauxite and alumina industry. Since the early 1960s production has been substantial, sufficient to make Guinea the world's number-two bauxite exporter after Australia in 2003. The industry's earnings are crucial to the national economy. But reserves would allow significantly greater ore output, converting a higher proportion to alumina would increase revenues.

Following a major political shake-up in the mid-1990s, the Guinean government and its foreign partners in bauxite-alumina production looked at ways to restructure and re-invigorate the industry, starting with the three existing operating companies: CBG, in which the Halco consortium of Western aluminium groups was, and remains, the government's operating partner; and the smaller Friguia and Kindia mines.

Friguia, which was similarly structured to CBG but is now a effectively a partnership with Russian firm Russkiy Alumina (RusAl), incorporates a 600,000t/y alumina refinery, while the Ste des Bauxites de Kindia (SBK) was, and is, purely a mining company. RusAl has a 23-year lease to manage this operation for the government.

Innovative decision

Faced with a specific problem, it was the operators at Kindia who made the innovative decision to introduce the Wirtgen Surface Miner technique to the bauxite industry. At the Debele Mine, the Tsentralnaya ore body section (presumably named by Soviet engineers who assisted Guinea to start the operation) some ore pillars had been left in areas where blasting was impossible--in the vicinity of a generator substation and along a public road and a railway line. The bauxite reserves in these pillars were estimated to be around 89,000 t. Further locations with similar conditions had been identified. In 2000, the mine operator. Kompanyia Boksity Kindii Co Ltd. decided to purchase a Wirtgen Surface Miner 2100 SM for the blast-free removal of these sections. During October 2000 the 2100 SM started operating in the Tsentralnaya ore body and after approximately 3,000 working hours, this machine had mined 300,000t of bauxite and 25,000t of overburden.

In November 2001 the mine started up a second Wirtgen machine, this time a 2200 SM, in the Tsentralnaya ore body. After three months, i.e. approximately 900 working hours, the 2200 SM had mined 95,000t of bauxite and 20,000t of overburden.

In both cases the Wirtgen Surface Miners operated on narrow faces less than 100m to 160m in length and ranging from 35 to 55m wide. Standard road trucks with an average payload of 16t hauled the mined material from the Surface Miners out of the pit. Direct loading of the cut material facilitates the operational processes in open cut mining.