Relation between Sticking and Metallic Iron Precipitation on the Surface of Fe₂O₃ Particles Reduced by CO in the Fluidized Bed

Abstract

The Fe₂O₃ particles (150–224 μm diameter) were reduced in a laboratory fluidized bed with CO–N₂ mixture gas at 700–900°C to investigate the relation between sticking and iron precipitation. As a result, the sticking tended to occur with acceleration of the reduction rate, judging from the fluidization time. The sticking depended strongly on the metallization ratio signifying the probability of iron-iron contact that estimated the contact area of precipitated iron when particles collide together, whereas the reduction degree had indirect influence on it. Many tiny iron grains with the diameter of approximately 20–40 nm were found on the surface of particles by SEM and EDS. According to theory of microcrystal melting point, the grains reached Tammann temperature easily, leading to higher surface energy of iron, producing higher adhesion force among the reduced particles.