In the process of primary copper smelting in flash smelting furnace (FSF), the ratio of iron to silica
(Fe/SiO2 mass ratio) primarily determines the slag viscosity and magnetite formation. Viscous slag
does not only cause difficulties in daily operation, such as in tapping, it also increases the copper
losses to slag. Thus, keeping the Fe/SiO2 mass ratio at the desired level is an important aspect of
FSF and slag cleaning furnace (SCF) operation.
In this study, the improvement of the Fe/SiO2 mass ratio was conducted in two steps: First, the
optimal Fe/SiO2 mass ratio was derived based on thermodynamic data. Based on this analysis,
appropriate control limits were determined. Second, this range of favourable Fe/SiO2 mass ratios
was implemented into operation by an advice-based control system, which suggests the addition of
silica based on the analysis of SCF slag. As this approach was successful, the same advice-based
control system principle was adapted for the coke addition to the SCF.
After testing the new advice-based control for several months, the production data confirm the
predictions by thermodynamics: since the prediction was implemented as an advisor, the copper and
magnetite content in SCF slag is significantly reduced and viscous slag is reported less often by
operations.