Influence of mixing coal composite iron ore hot briquettes on blast furnace simulated reaction behavior in a packed mixed bed

Abstract

For iron making processes which need decreasing CO2 exhaust, coal composite iron ore hot briquette (CCB) is promising. This agglomerate contains coal with iron ore by utilizing the thermal plasticity of coal, where, carbonaceous material and iron ore are closely adjoined at the micro level, and which enables reactions to proceed from lower temperatures and finish earlier. In this study, we assumed mixed charging of CCB in ore bed aiming at improvements of permeability and gas utilization and performed high temperature reaction tests under load simulating blast furnace conditions using mixed samples consisted of iron ore mini pellet and briquette. As a result, gasification and reduction in mixed bed were accelerated around 910°C to 1 000°C. This reaction acceleration was presumed to derive from mutual acceleration between gasification in briquette and indirect reduction in pellet. However, if the residual carbon in briquette is consumed completely by gasification, reduction is possibly delayed through the deterioration of permeability by sintering of pellet and briquette. It was also found that increase of reduction gas flow rate prevented the residual carbon in briquette from being consumed and accelerated reduction by sustaining the role of briquette as a spacer. And it was found that lowering thermal reserve zone temperature aggravated reducibility of pellet and delayed reduction of mixed bed. Moreover, it was found that shrinkage behavior of the bed had strong relation to amount of residual carbon in briquette and reduction behavior of pellet. © 2011 ISIJ.