Removal of Impurities in Iron Ore by Na₂O-B₂O₃ Flux

Abstract

Removal of impurities in fine-grained iron ore with Na₂O-B₂O₃ flux and its mechanism have been investigated. The flux leaching method in which the oversaturated amount of powdery iron ore is treated with the flux has been used in the temperature range from 850 to 950°C. The recrystallization method has also been used in the temperature range from 1 400 to 1 450°C. The isolated impurities as well as those on the surface of ore particles were removed by the former method, while the inclusions present inside the particles together with the above-mentioned impurities were removed by the latter method. The high yield of iron oxide and the low content of impurities were obtained at the flux compositions of Na₂O·2B₂O₃ and 2Na₂O·5B₂O₃. The contents of Si, Al, Ca, Mg, Mn, and V decreased with increasing temperature from 850 to 1 450°C; these observations were explained by the break up of ore particles and the increase of the amount of recrystallized iron oxide. About 80% of iron oxide yield was obtained in both flux treatments by use of the Na₂O·2B₂O₃ flux.