Kinetics of mass transfer of manganese and silicon between liquid iron and slags

Abstract

The kinetics of mass transfer of Mn and Si between liquid iron and slags were investigated in laboratory experiments at 1600°C in MgO crucibles with 1500 g iron and 250 g slag. Three different slags consisting of CaO‐MgO‐MnO‐SiO2, MgO‐MnO‐SiO2 and MgO‐MnO‐Al2O3‐SiO2 were used. The concentration‐vs.‐time curves, experimentally measured under defined flow conditions generated by gas stirring, were evaluated by application of a multi‐component transport model in order to obtain the mass transfer coefficients. The numerical values of the thus determined measured mass transfer coefficients were compared with values calculated by a theory of mass transfer at liquid‐liquid interfaces. The measured and theoretical values were in good agreement with each other in the case of reduction of MnO from the slag by Si in the metal, provided that the measurements had been carried out below a critical stirring intensity, above which metal droplets were emulsified in the slag. Experiments, where sulphur was dissolved in the metal melt and where the sulphur contents were systematically varied, showed no changes of the mass transfer coefficient in comparison to sulphur‐free melts. The experimental mass transfer coefficients for the reduction of silica from the slag by manganese in the metal were smaller than those calculated by the mentioned mass transfer theory. This could be explained by inhibition of surface renewal under the influence of solid reaction products precipitated at the interface.