Sticking behavior caused by sintering in gas fluidisation reduction of haematite

Abstract

The sticking of haematite and iron powder during the fluidisation process was investigated using a visual fluidised bed reactor. The results showed that the amount of iron needed to stick decreased with increasing fluidisation temperature. Owing to no iron whisker formation in the experiments, the sticking phenomenon was discussed in the special case where iron morphology was dense or porous, and much attention should be paid to the effect of sintering of iron–iron contact on sticking, especially, surface nano-/microstructures of fresh iron that caused an increase in particle cohesiveness and sticking tendency. It was assumed that haematite covered with iron transformed into cohesive particles that self-agglomerated above minimum sintering temperature. Owing to the interface reaction induced, the sticking temperature of haematite was always lower than that of iron powder in the same size ranges. On the basis of sintering with surface diffusion mechanism, the tendency of sticking was enhanced by reduction reaction through reinforcing mass transfer on particle surface. Therefore, when iron whiskers were suppressed, sticking phenomenon was viewed as the agglomeration fluidisation among cohesive particles under sintering action.