Transfer Mechanism of Lanthanum from Rare Earth Containing Iron Ore to Pig Iron during the Blast Furnace Process

Abstract

Some iron ores are enriched with lanthanum element, for example, the Bayan Obo iron ore in China. The pig iron which used the Bayan Obo iron ore as the raw material was obtained from the blast furnace of Baotou Steel in order to research the transfer mechanisms of lanthanum from rare earth containing iron ore to pig iron during the blast furnace process. The thermodynamic process was calculated using the molecular-ion coexistence model. The slag-metal reactions of the hearth were carried out in the tube furnace. The morphology and phase structure in the pig iron were observed by SEM and XRD. The rule of lanthanum transfer was analyzed by physical and chemical analyses using ICP-MS. Fourier-transform infrared spectroscopy was used for analyzing the vibrations of functional groups. The results indicate that the La2O3 in the slag was reduced to LaC2 by carbon and then the LaC2 dissolved into the molten iron to form La. At last, coke which has the oxygen-containing functional groups (C-OH, C=O, and C-O-C) has capacity to absorb lanthanum that is dissolved in the molten iron during the blast furnace iron-making process, and increasing the lanthanum content in the slag leads to higher lanthanum concentration in the porous graphite phase of the pig iron. The coke is graphitized during the process and could remain in the pig iron as porous graphite phase which acts as the carrier of lanthanum.