Kinetics of hot metal desulfurization using CaO–SiO₂–Al₂O₃–Na₂O–TiO₂ slag

Abstract

Kinetics of hot metal desulfurization were studied using CaO–SiO₂–Al₂O₃–Na₂O–TiO₂ slag in the range of 1400–1500 °C on a laboratory scale. The results of kinetic experiments indicate that the desulfurization rate increases as the temperature, Al₂O₃ content, Na₂O content, and TiO₂ content increase and basicity increases from 1.01 to 1.75, but decreases when basicity increases from 1.75 to 2.02. The melting effect of slag is promoted as the temperature, Na₂O content, and TiO₂ content increase and Al₂O₃ content increases from 12.13 to 17.17 mass%, but worsened as basicity increases and Al₂O₃ content increases from 17.17 to 22.27 mass%. A kinetic model of hot metal desulfurization has been developed to calculate the mass transfer coefficient and the mass transfer resistance of sulfur in slag. The mass transfer coefficient of sulfur increases as the temperature, Al₂O₃ content, Na₂O content, and TiO₂ content increase and basicity decreases. Total mass transfer coefficients of sulfur were in the range of (5.02–23.78) × 10⁻⁷ m s⁻¹. The activation energy was estimated to be 464.06 kJ mol⁻¹ at the temperature from 1400 to 1450 °C and 176.35 kJ mol⁻¹ at the temperature from 1450 to 1500 °C. The sulfur distribution at the slag–metal interface was observed using a mineral liberation analyzer. The result shows that the mass transfer of sulfur in slag is the controlling step at high temperature during the desulfurization process.