Modeling Evaporation of Sb from Molten Fe–C–S Alloys for Sustainable Steelmaking Supported by Experiment and Mechanisms Analysis

Abstract

 Sb is one of the tramp elements that remain in molten steel during the steelmaking process. It is generally known to be difficult to remove it from the molten steel. In order to develop a feasible process to remove Sb from molten steel, the evaporation reaction of Sb from molten steel was investigated by high-temperature liquid–gas experiments using an electromagnetic levitation melting technique and kinetic analysis. The evaporation rate of Sb was measured by varying the flow rate of incoming gas (Q), temperature (T), initial C content ([pct C]\(_0\)), and initial S content ([pct S]\(_0\)) in molten Fe–C–S–Sb alloys. It was found that the evaporation rate of Sb accelerated by S due to the formation of the sulfide gas species (SbS(g)) and by C due to increasing the activity coefficient of Sb (\(f_{\textrm{Sb}}\)) and S (\(f_{\text {S}}\)). On the other hand, the evaporation rate of Sb decelerated by S due to the blocking of the molten steel surface. Based on the established mechanism, a model of Sb evaporation from molten Fe–C–S–Sb alloy was developed in the present study, which considers (1) actual evaporating species, (2) surface blocking by S using ideal Langmuir adsorption, and (3) effect of C and temperature on \(f_{\text {Sb}}\) and \(f_{\text {S}}\). With the established model, the extent of Cu, Sn, and Sb removal in the molten steel was assessed. It turned out that Cu has the fastest removal rate, followed by Sb, with Sn being the slowest for molten steel containing 0.1 pct C and 0.01 pct S at 1650 \(^\circ \)C.