Electrical Conductivity Measurements in Ternary SiO2-PbO-CaO Slags

Currently, the valorization of slags from the lead production/recycling industry is difficult due to their high lead content. Moreover, lead is still mainly produced via blast furnaces which use cokes for heating and thus emitting a large quantity of greenhouse gasses. A potential solution for both issues is to change the production to a submerged electric arc furnace which relies on electricity for heat generation. The operation of this furnace is highly dependent on the slag's electrical conductivity and thus, knowledge of the dependency of this property as a function of the slag's composition is essential, but mostly lacking in literature. To obtain fundamental insights on this property as a function of slag composition, a simple ternary PbO-CaO-SiO2 system was studied wherein PbO was gradually replaced by CaO at a constant SiO2 content. The presented experimental results show a significant non-linear decrease in the electrical conductivity as a function of PbO by CaO substitution. This decrease cannot be predicted by the currently available electrical conductivity model based solely on the slag's degree of polymerization. Similarities between the observed trends in electrical conductivity due to this substitution and mixed-(earth) alkali slags/glasses may further prove that Pb2+ and Ca2+ exhibit a mixed modifier effect in the molten state.