Slag Basicity: What Does It Mean?

The concept of “basicityBasicity” has been central to our understanding of slag chemistrySlag Chemistry for many decades. Traditionally, basicityBasicity has been connected to the level of networking present in a slag, acid slags having a great deal of networking and basic slag having less networking. Qualitatively, this approach provides quite reasonable explanations to the viscosityViscosity of slags, their general interaction with refractories and their ability to dissolve oxidised elements from the metalMetal/matte phase. Various quantitative measures of basicityBasicity have been proposed, such as optical basicityBasicity and the NBO/T ratio, and there have some successful attempts to link these measurements to important propertiesProperties. However, in general, these measures have not been successfully linked to common thermodynamicThermodynamic relationships (other than empirically) or direct measurements from the plant. In industry, weight ratio’s and empirical relationships dominate the control logic of the metallurgical processes. In this paper, we will review what is the current state of knowledge of “basicityBasicity”, recent research into connecting NBO/T ratios to quantitative measurements and thermodynamicThermodynamic quantities and propose a way forward towards a more rigorous and useful understanding of “basicityBasicity”.