Morphology change and carburization characteristic of iron ore-coal composite during reduction under a simulated condition of blast furnace

Ironmaking process by Blast Furnace (BF) method contributes about 70% of CO₂ emission and energy consumption in steel works. To aim at the sustainable development and environmental protection, decreasing CO₂ emission and energy consumption is always an indispensable task. Using iron ore-coal composite as the raw material of BF is a promising way to mitigate the above issue. In this study, we conducted an experiment procedure which is to simulate the reduction of an iron ore-coal composite travelling from the top zone to the cohesive zone of BF. Reduction behavior, morphology changes and carburization characteristic of the composites with the variables of C/O (Carbon to Oxygen) ratio were investigated. As C/O ratio was increased from 0 to 0.6, the reduction rate of composite was accordingly enhanced. It was found that the composite is swelling severely when C/O ratio was lower than 0.4. The swelling occurred in the temperature range from 800°C to 1 100°C which was just under the stage of reduction from wustite to iron. The composite is shattering obviously starting from 1 160°C when C/O ratio was higher than 0.4. It is because the remained free carbon is surplus in reduced iron, causing shattering and powdering. Hence, C/O = 0.4 was suggested to the composite for being charged into BF.