Effect of Water Vapor on O2− Content in Ironmaking Slag

In principle, slag basicity can be expressed as the concentration of free oxygen (O2−) in the slag system. This free oxygen content is equilibrated with different silicate anions in addition to other components in the silicate-based slags. X-ray photon spectroscopy (XPS) and scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS) were used to investigate the effect of water vapor on the free oxygen content in ironmaking slags. It was found that water in the gas atmosphere plays a significant role in the silicate anion equilibria. Water decreases the amount of free oxygen in the studied slags, with the free oxygen expressed as percentage of the total oxygen decreasing in the order of the following gas mixtures: CO+CO2 (44%, pH2O = 0 kPa) > CO+CO2+H2+H2O (41%, pH2O = 10.13 kPa) > H2+H2O (37%, pH2O = 14.19 kPa). The content of free oxygen ion affects the distribution of elements such as sulfur, phosphorus, and manganese. In addition, it affects the iron oxide content in the slag as well as the interaction between slag and furnace lining.