CBMM

摘要

Companhia Brasileira de Metalurgia e Mineracao is part of the Moreira Salles Group, and its niobium mine and associated plant are situated near Araxa in Minas Gerais State, Brazil. The pyrochlore deposit is mined by the open-pit method, using no explosives. A conveyor belt 3.5km long transports the mineral ore from the mine to the concentration plant, which has installed production capacity of 84 000 tons per year. Processing is carried out by wet grinding, magnetic separation, desliming and flotation. Wet grinding separates out the pyrochlore crystals, and ore particles are reduced to less than 0.104mm. Magnetic separation is used to eliminate magnetite, a mineral with a high phosphorus content, and desliming removes fractions below 0.005mm in cyclones of 25mm. Flotation concentrates pyrochlore in tanks where pyrochlore particles are mixed with chemical reagents and trapped by air bubbles introduced at the bottom of the tank. The concentrate which thus floats contains 60 percent Nb_2O_5, and the underflow is transferred to a tailings disposal dam.