A Kinetic Model on Oxygen Transfer at a Steel/Slag Interface under Effect of Interfacial Tension

Abstract

A kinetic model was developed to predict the dynamic change of the oxygen content in the sub-interface region as well as the dynamic change of the interfacial tension between molten steel and slag. The dynamic steel/slag interfacial phenomena are very complex, where the combined effect of thermodynamics and kinetics on the interfacial tension needs to be accounted for. As a first step, the current model only considers the SiO 2 decomposition, oxygen adsorption and desorption at the steel/slag interface to realize the modeling of the dynamic change of the steel/slag interface phenomena. The oxygen desorption rate was derived based on the slope of the interfacial tension change over oxygen content. Specifically, the oxygen change with time in a sub-interface was predicted by the current model. The oxygen desorption rate was found to have an important influence on the dynamic change of the oxygen content in the sub-interface region. Furthermore, a low slag viscosity was found to increase the oxygen content at the interface due to the fast supply of SiO 2 from the slag bulk to the interface. In addition, the equilibrium constant for the oxygen adsorption at an interface due to the interfacial tension effect increases the oxygen content in the sub-interface region.

A Kinetic Model of Mass Transfer and Chemical Reactions at a Steel/Slag Interface under Effect of Interfacial Tensions

“…This dynamic change of the interfacial tension includes the following steps: i) an oxygen element transfer from the slag to the interface, ii) an oxygen element adsorption at the interface due to the interfacial tension, iii) an oxygen desorption from the interface to the steel bulk, iv) an oxygen reaction with the reductive elements, and v) the transfer and dissolution of the reaction products into a slag phase. Based on the above proposed mechanism, Ni et al 7) developed a kinetic model to describe this dynamic change of the interfacial tension, where the silica decomposition at the interface, the oxygen adsorption and desorption at the interface and the mass transfer in the steel and slag phase were considered. This model is different from some previously reported kinetic models [8][9][10] since the effects of the interfacial tension on both interfacial reactions and the transport of some interface active elements were considered.…”

“…Furthermore, the current model is not based on the mass flux balance assumption at the interface which commonly has been used in previous kinetic models. [8][9][10] In this paper, the new kinetic model was further developed based on the previous model developed by Ni et al 7) to include the aluminum reaction with oxygen in the interfacial region and the dissolution and transfer of the formed alumina to the slag phase. This aims to describe the dynamic behavior of the interfacial tension in a more realistic way, since reductive elements commonly exist in some steels.…”

“…At a steel/slag interface, chemical reactions are expected to be greatly affected by the interfacial tension as well as the adsorption of surfactant elements such as oxygen at the interface. In the previous model, 7) the issues such as the silica decomposition, the adsorption and desorption of a surfactant element at the interface and the element transport due to chemical potential difference have been considered. In this paper, the focus is on the influence of the reaction between the released oxygen from the SiO 2 decomposition and aluminum in steel on the dynamic change of the interfacial tension.…”

“…The whole dynamic process is described as below. Since the model information for parts 2.1, 2.5, 2.6 and 2.7 in the following have been described in detail in a previous study, 7) only the important information about these parts are introduced in this paper.…”

“…SiO 2 decomposition reaction can happen at the steel/slag interface as soon as the steel and slag is in contact with each other and when the oxygen chemical potential in steel is lower than the equilibrium value corresponding to the SiO 2 potential in slag. The SiO 2 decomposition rate at the interface has been described in detail in our previous study 7) and it can be expressed by the following equation:…”