High-temperature beneficiation of a tantalum-niobium concentrate by selective ferroalloying

CIM Bulletin, Vol. 78, No. 874, 1985


A low-grade concentrate from the Crevier Township, Quebec, containing 1.8% Ta2O5 and 13.7% Nb2O5 was reduced with carbon at 1600"C, and niobium and tantalum were selectively absorbed in liquid iron. To slag off the zirconia-rich gangue, some silica and lime were added as flux. Metallic iron was added in such a way that the combined contents of TaC and NbC did not exceed 20% in the ferroalloy. Up to 95% of the niobium, and up to 80% of the tantalum contained in the concentrate were recovered in the metal. The ferroalloy was ground finely and dissolved in 2 wt % sulphuric acid to leach out iron and silicon preferentially. The insoluble residue consisted principally of NbC and TaC, the calcination of which yielded an enriched concentrate comprising 80% Nb2O5 and 8% Ta2O5. The insoluble residue could also be chlorinated to obtain an impure liquid of NbCls and TaCl5. Process variables and their effects are discussed in terms of higher metal recoveries in the smelting.
Keywords: Pyrometallurgy, Smelting, Leaching, Calcination, Niobium, Tantalum, Ferroalloys.