Effect of Alkaline / Alkaline-Earth oxides on Viscous Behavior of Iron-making Slag system

摘要

Viscosity is the physical property of most interest to the majority of industrial processes. It is an important rheological parameter to be considered in dealing with fluid flow behavior and in understanding the hydrodynamics and the kinetics of reactions. Also, the rate of reactions between metal and slag can be determined by continuous measurement of the viscosity of composition. Moreover, viscosity is an indispensable quantity to predict other important transport coefficients, such as diffusivities, thermal conductivities and surface tensions of molten metals and slags. Thus, the viscosity is one of the most important factors to understand the thermodynamic properties of molten slag not only in the metallurgical community but also in chemical geology. Recently, BF operation in the ironmaking process includes the use of low grade iron sources and the pulverized coal injection, which have lead the increase of Al2O3 in the typical iron-making slag system. Due to the amphoteric behavior of Al2O3, it would be necessary to have a new perspective for estimating the effects of major elements such as CaO, SiO2, MgO and FeO significantly affecting on the viscous behavior of slag in the iron-making process. Although the alkaline oxide such as Na2O, K2O accompanied with low grade material sources can also affect the viscosity and thus impact the stability of the BF operation, relatively little has been known for the effect of alkali oxides (Na2O, K2O) on the viscous behavior under conditions of high Al2O3 concentrations. Furthermore, the contributions of Na2O and K2O toward the ionic charge compensation effect and structural changes in the BF type slags have not yet to be fully understood. The focus of present study is to understand the effect of not only major elements such as CaO, MgO but also alkaline oxide on the viscous behavior of iron-making slag system. To better understanding the viscous behavior, structural changes has been estimated using by Fourier Transform Infrared (FT-IR) spectroscopy, where the original Darken's excess stability function and ionic charge compensation effect was introduced in order to understand the thermo-physical phenomena. In addition, some effort has been also attempted to verify the relationship among the viscosity, primary phase and critical temperature.