Slag parameters and sulphur partition in blast furnace hearth: Ukrainian case and international comparison

Blast furnace ironmaking usually requires maintaining a reasonable level of hot metal desulphurization; therefore, knowledge of the complex interplay between physical properties and desulphurization potential of slag is essential for the holistic approach to the operation. Several models for predicting sulphur partition between slag and hot metal based on sulphide capacity estimation have been studied in application to the Ukrainian blast furnace. Influence of an optical basicity, as well as of CaO/SiO2 and MgO/Al2O3 ratios on sulphur partition between slag and hot metal, was analysed. Attainment of the equilibrium partition was estimated in connection with Si content in hot metal. International comparison of blast furnace slags was conducted involving data for 25 steelworks from 16 countries covering composition, physical properties and desulphurization potential. Approaches to optimization of slag composition are discussed, considering the tradeoff between enhancing slag's desulphurization capacity and keeping its physical properties favourable to smooth and productive operation.