Proposing a suitable slag composition by estimating the fusion behavior, viscosity and desulphurization ability for blast furnaces running with high alumina

Abstract

The present work was focused on identifying a suitable quaternary CaO-MgO-SiO2-Al2O3 high alumina slag for blast furnaces running with high alumina ores as an input raw material. These high alumina slags have inferior properties like high liquidus temperature, high viscosity and poor sulphur absorption capacity. These properties will hamper the working condition of the blast furnace as well as quality of hot metal produced. To overcome these issues, it is necessary to focus on selecting an appropriate slag composition having superior properties like, minimum difference between softening and flow temperature (ST & FT) (<100 °C), low liquidus temperature, good fluidity (i.e. viscosity <0.6 pas. at 1773 K) & high sulphur absorption capacity at 1773 K. In the current work various slag compositions having Al2O3 25–30 %, CaO/SiO2 ratio (0.8–1.6), and MgO (8–16 %) has considered for determining fusion temperature, viscosity and desulphurization ability of slag using high temperature microscope, viscometer and slag-metal Desulphurization experiments. It was found that slag with Al2O3 (30 %) and C/S ratio (1.2) coupled with MgO (12 %) is showing superior properties like low FT-ST (i.e. short slag) having viscosity 0.35 pas and Desulphurization ability of approx. 80 % at 1773 K which fulfills the necessary conditions for better working condition of the blast furnace.