Abstract

In spite of the vast amount of research regarding the operation of blast furnace, the gas composition change in a single charge material layer in a blast furnace is not an extensively studied research area. Iron-bearing material and coke are charged in turn as layers into the blast furnace as raw material. With no percolation of layers taken into account, the composition of gas varies in turn in the blast furnace shaft, losing its reducing potential in an iron-bearing material layer and being reformed in a coke layer.

In this paper, the effect of reactions in sinter, pellet and coke layers on the gas composition between the blast furnace top and the cohesive zone has been discussed. The gas was analysed on-line on multiple heights of a tube furnace loaded with a material bed of 1.0 m in height and uniformly heated at a rate of 2°C/min or 3°C/min up to 1100°C or 1200°C. As a result, the H₂–H₂O gas composition change occurred in a higher temperature than the CO–CO₂ change in sinter, pellet and coke beds. This led to a conclusion that the reduction of iron oxides by hydrogen and gasification of coke by water vapour started in somewhat higher temperatures than the reactions with carbonaceous gas components. Additionally, olivine pellets were more reducible in moderate temperatures compared with sinter and the utilisation rates of CO and H₂ gases rose higher in a pellet bed than in a sinter bed, mainly due to the higher hematite percentage in pellets.