Influence of Reduction Condition on the Morphology of Newly Formed Metallic Iron During the Fluidized Bed Reduction of Fine Iron Ores and its Corresponding Agglomeration Behavior

摘要

The fine iron ores from Chile are reduced in a laboratory fluidized bed at 973-1173 K with CO-H-2-CO2 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/Fe1-xO 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 CO2 in CO makes the fibrous iron shorter and sparser, especially when the content of CO2 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 + CO) >= 30%, by volume).