The sulfur distribution ratio (Ls) is an expression of the amount of sulfur in slag to the amount of
sulfur in molten metal. The sulfide capacities calculated from Reddy-Blander (RB) model were used
to calculate the sulfur distribution ratio (Ls). A new Reddy model for sulfur distribution ratio (Ls) was
developed for modelling Ls for ironmaking, steelmaking, and secondary steelmaking conditions.
Besides calcium oxide, the major component in the ladle furnace (LF) slags is alumina. The Ls was
calculated for typical LF slags as a function of temperature and composition. The model calculated
Ls values are in good agreement with the experimental and industrial slags data. The extremely low
oxygen potential in these furnaces after fully-killed steel is favourable for desulfurisation.
For any given slag’s composition and temperature, its sulfide capacity can be calculated a priori. The
equilibrium sulfur distribution ratio between this slag and liquid metal in a particular vessel can also
be calculated a priori. The Ls for ladle furnace (LF) slags is about twice those for blast furnaces (BF)
slags and ten times those of basic oxygen furnace (BOF) slags. The desulfurisation of pig iron in BF
and desulfurisation of steel in LF during secondary steelmaking are recommended. Steel
desulfurisation in steelmaking furnaces is not effective. Since the model used to calculate the sulfur
distribution ratio (Ls) is a priori, it is a useful tool for the iron and steel makers in improving the product
quality and optimisation of the industrial furnace operations.