An attempt at optimizing the flow characteristics of blast furnace slag by investigation with synthetic slag prepared in the laboratory using pure oxides

Abstract

In the cohesive zone the ore layer becomes compacted due to softening-melting and the gas passes predominantly through the sandwiched coke layer (coke slits). Minimizing the size and lowering the position of the cohesive zone will improve productivity and decrease coke rate. This work is designed at 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 brought and their flow characteristics were measured under the heating microscope. With the same composition as obtained from the plant, a synthetic slag was prepared in the laboratory. It was melted to 1600 °C and then water quenched to form the glassy state. Flow characteristics for the same were also determined. In addition, all slag samples were sent to DISIR, Rajgangpur for slag analysis as well as to determine the mineralogical phases present in them. For this, they heated the slag samples 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. Moreover, flow characteristics data of synthetic slag was compared with that obtained from Blast Furnace slag.