An attempt at optimizing the flow characteristics of blast furnace slag by Investigation with slag obtained from blast furnace of Rourkela steel plant, SAIL

Abstract

Due to the softening-melting of the burden in the cohesive zone of the blast furnace, the ore layer becomes compacted and the gas passes predominantly through the sandwiched coke layer known as coke slits. For improved productivity and reduced coke rate, it is required to minimize the size
and lower the position of the cohesive zone in the blast furnace. This work is designed by arriving at a slag composition through actual experimentations which will ensure the lowering of the cohesive zone of the blast furnace with simultaneous decrease in the difference between the softening temperature (ST) and flow temperature (FT) of the slag. Slag samples from SAIL, Rourkela were collected and their flow characteristics were measured using the heating microscope. With the same composition as obtained from the steel plant, a synthetic slag was
prepared in the laboratory using pure oxides, by another group. It was melted to 1600 °C and then water quenched to form the glassy state. Flow characteristics for the same were also determined. The flow characteristics data of Blast Furnace slag were compared with that obtained from synthetic slag. All the slag samples were sent to DISIR, Rajgangpur for slag analysis as well as to determine the mineralogical phases present in them, for which the slag
samples were heated to 1500 °C followed by slow cooling to convert them to crystalline form. Then, XRD analysis was done to determine the mineralogical phases. Finally, with relevant phase diagram study, we arrived at a composition which will ensure the lowering of cohesive zone.