The fine iron ores from Chile are reduced in a laboratory fluidized bed at 973-1173 K with CO-H 2 -CO 2 mixtures to investigate the influence of reduction condition on the morphology of newly formed metallic iron and its corresponding agglomeration behavior. The results reveal that the addition of H 2 in CO accelerates the moving rate of the Fe/Fe 1-x O interface and increases the amount of the iron nucleus formed during the initial reduction period, which induce the transformation of iron morphology from fibrous to dense. The presence of CO 2 in CO makes the fibrous iron shorter and sparser, especially when the content of CO 2 is 30% (by volume), the iron appears as "cactus-like." The increase of reduction temperature makes the fibrous iron stronger and more active. The sticking index indicates that the long and strong iron whiskers are prone to form stable agglomerates even at a low metallization degree, but the dense iron trends to behave separate. Furthermore, based on the precipitation mechanism of iron proposed by the authors, it is manifested that the agglomeration behavior of the fine iron ores could be controlled by pre-reduction in H 2 -rich reducing gas (H 2 /(H 2 þ CO) ! 30%, by volume).

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This paper contrastively investigated the reduction behavior of raw and oxidized vanadium titanium magnetite ore (RVTM and OVTM) in a bubbling fluidized bed at 800°C under 75%N 2 -25%H 2 , and systematically revealed the relationship between the structure, phases change, MgO migration behavior and the reduction performance. Microstructure observations suggest that oxidization conditions greatly affect structural evolution, phase transformation of Fe-Ti oxides, and migration of MgO in OVTM. The reduction results indicated that the average metallization degree enhanced by 8-10% as the OVTM ore had high oxidization degree. When the RVTM ore was treated at 800°C, the reduction rate increased with the increase of oxidization degree, no significant difference was observed among these oxidized samples due to their similar internal and surface structure. However, the reduction rate of OVTM at 950°C depended on the oxidization time. The reduction rate of OVTM oxidized at 950°C for 2 h was faster than the one for 1 h, which was attributed to the better exsolution of MgO and the formation of bigger pores, even though both samples were fully oxidized and Fe 2 TiO 5 formed in the oxidization process.