Slag Electrical Conductivity and Its Effect on Mass Transport and Interfacial Reaction Kinetics

Abstract

Pyrometallurgical refining typically involves slag–metal reactions which are commonly controlled by transport of reactants in the slag or metal phase. For the simplicity of analysis, mass transport in slag is generally treated on a phenomenological basis as transport of molecules. Although this approach works well for many of the reaction systems over narrow ranges of conditions, it can fail when extrapolated over a wide range of conditions. In many refining processes, transport of oxygen in slag determines the kinetics of major reactions. Transport of oxygen in slag is strongly influenced by the electrical conductivity of slag. Whilst this has been well understood since the 1950s, there have been relatively few attempts to quantify the effects of slag electrical properties on the refining kinetics. Herein, an overview is presented focusing on the electrical properties of slags and their effects on the transport kinetics in steelmaking reactions. An analysis is conducted based on a modified version of the approach taken by Wagner to describe oxygen transport in solid oxides. Data from the literature including work from the authors’ laboratory is discussed in an evaluation of literature oxygen transport in CaO–SiO2–FetO, CaO–SiO2–Al2O3–FetO, and PbO–Fe2O3 slags.