FACTORS AFFECTING THE STICKING OF FINE IRON-ORES DURING FLUIDIZED-BED REDUCTION

Seven types of iron ores were reduced to iron phase in a laboratory fluidized bed at 900-degrees-C by N2-H-2 mixtures to examine the influence of ore type, reducing potential, and sulfur potential on sticking phenomenon and iron morphology in the bed. In case without H2S addition, five types of ores having low Al2O3 content sticked by mostly short iron whiskers and/or porous irons, while two types of ores having high Al2O3 content fluidized with plain irons on their surface. Increment of the reducing potential did not much change these microstructures besides reaching to higher reduction levels. Addition of H2S capable of forming FeS into the gas mixtures facilitated the appearance of coarse porous irons to keep fluidized until nearly complete reduction. The overall metallization process of an ore bed was estimated to proceed under the hydrogen gas supplying control with a high gas utilization. On the basis of the results obtained for 19 types of ores, including those employed in the previous tests, the sticking tendency is generalized in relation with factors such as iron morphology, surface energy of iron, and external shape of ore.