Enhancement of iron ore sinter reducibility through coke oven gas injection into the modern blast furnace

Abstract

Energy network within the integrated steel works should be used more efficiency to reduce the energy consumptions and CO2 emissions. The injection of free resources of coke oven gas (COG), which is rich with hydrogen, into the modern blast furnace is one of such measures. In order to clarify the effect of COG injection on the reduction processes in the blast furnace; iron ore sinter was isothermally and nonisothermally reduced with different gas compositions at different temperature. The gas compositions were selected to simulate the conditions of middle (150 m3/tHM) and intensive (300 m3/tHM) injection of COG into the blast furnace. The results were compared to that obtained under typical blast furnace conditions without COG injection. The isothermal reduction at 900-1 200°C indicated the enhancement of the reduction rate as COG injection increased. The non-isothermal reduction indicated the efficiency of intensive injection of COG in decreasing the direct reduction from 50% to only 5% at 1 200°C. Reflected light microscopy, scanning electron microscopy and X-ray techniques were used to characterize the microstructure and the developed phases in the origin and reduced sinter. The rate controlling mechanism of sinter under different conditions was predicted from the correlation between apparent activation energy calculations and microstructure examination. © 2013 ISIJ.