Article ID: ISIJINT-2020-063
As an innovative route to mitigating CO2 emissions in ironmaking, increasing the hydrogen reduction in a blast furnace is promising. One possible method is the shaft injection or blast tuyere injection of coke oven gas (COG) with its hydrogen concentration enhanced by steam-reforming methane and tar. Therefore, the reduction behavior of sintered ores in a blast furnace by injecting reformed COG was investigated using a softening-melting tester and counter-current reaction simulator (BIS). The shaft injection of reformed COG promoted the reduction and improved the permeability of the ore layer, particularly in the wall area of the blast furnace. An injection rate larger than 200 Nm3/t-HM was required for reformed COG for a limiting intermediate distribution ratio of injection gas lower than 20% in a large blast furnace. Unchanged shaft temperature and increased hydrogen reduction were observed during the shaft injection of hot reformed COG in the BIS test. The water-gas shift reaction below the temperature of the thermal reserve zone was insignificant even for the shaft injection of reformed COG. As for tuyere injection, direct reduction was decreased by increasing the injection rate of reformed COG from tuyere. The injection of COG with or without reforming from tuyere reduced the carbon consumption of the blast furnace by 10 kg/t-HM. The influence of the composition of COG on carbon consumption was insignificant. Direct observation of hydrogen reduction revealed a decrease in flooding molten slag in the upper coke layer during reduction, thus explaining the improved permeability of the ore layers.