Optimisation of slag composition (MgO and Basicity) to operate 20% alumina in Blast Furnace slag

Abstract

Blast furnace (BF) operation depends on the smooth upward movement of gas and its pressure drop. The slag properties like viscosity affects the gas flow inside the furnace. It is well-known that Al2O3 contributes to the increase of slag viscosity. For smooth BF operation, the maximum limit of Al2O3 in the Indian BF slag is around 18.5%. Higher Al2O3 contents make tapping of the BF slag difficult. In the present work, FACTSAGE calculations were carried out to estimate the viscosity and melting temperature of 20% Al2O3 slag varying MgO% between 7 and 13 and basicity (B2, defined as wt% CaO/wt % SiO2) between 0.9 and 1.2 to find an optimum MgO% and basicity for easy tapping of the slag. The results of the calculations provide three combinations of MgO (12,12.5,13%) and B2 (0.95) of slag for operating 20% Al2O3 in slag which were validated through experimental studies involves the inclined plane test, hot stage microscopy and X-ray diffraction.