Sulphur control of blast furnace hot metal by manganese additions

Abstract

This investigation deals with experimental determination of solubility of sulphur in Fe-C-Mn melts in the temperature range of 1473 to 1673 K. Such temperatures occur during the transit of hot metal from the blast furnace to the mixer in a steel plant. Sulphur content of the metal decreases with an increase in manganese content of the metal at a constant temperature or with a decrease in the temperature at constant Mn level of the bath. Thermodynamic data are used to calculate the equilibrium value of sulphur as a function of temperature and Mn content. The activity of MnS is near unity in absence of any other desulphuring agent, but it decreases with addition of certain fluxes often needed to produce a liquid slag layer. Experiments are designed to study the effect of slag chemistry on sulphur content of the metal at various Mn levels. A mathematical model based on mass and enthalpy balances in the lower part of the blast furnace is developed to determine the required iron ore and coke rate at different manganese levels of the hot metal.