Reaction Behavior of Iron Minerals and Metallic Iron Particles Growth in Coal-Based Reduction of an Oolitic Iron Ore

The reaction behavior of iron minerals and growth of metallic iron particles in coal-based reduction of an oolitic iron ore were investigated by X-ray diffraction (XRD) and scanning electron microscopy/enegry dispersive spectroscoy (SEMI EDS), respectively. The results show that, the reduction of iron minerals occurred in the sequence of Fe2O3 -> Fe3O4 -> FeO -> Fe. During the reduction, the main reducing reactions were indirect and the direct reactions that would also be crucial only occurred at the early stage. Because of high contents of SiO2 and Al2O3 in the ore, the solid phase reactions of FeO with SiO2 and Al2O3 took place. Small amounts of metallic iron (or FeO) were reduced from the ore in irregular shape and formed spherical particles when reduction time increased to 10 min. With reduction time increasing, the Fe diffused from small metallic particles toward the larger ones and coalesced with them. The whole reduction process could be analytically derived for the stages of chemical reaction, nucleation, and crystal growth.