A Thermodynamic Model for Evaluation of Mass Action Concentrations of Ce_2O_3-contained Slag Systems Based on the Ion and Molecule Coexistence Theory

摘要

According to the ion and molecule coexistence theory (IMCT) for molten slags and corresponding phase diagrams, a thermodynamic model for the evaluation of mass action concentrations (designated by N_i for structure unit i) for Ce_2O_3-Al_2O_3, CaO-Al_2O_3-Ce_2O_3 and CaO-Al_2O_3-SiO_2-Ce_2O_3 slag systems has been formulated. The results show that when the mole fraction of Ce_2O_3 is at 0.49 in the binary slag, the mass action concentration of Ce_2O_3 • Al_2O_3 achieves its maximum value 0.90. In a composition area of CaO/Al_2O_3 (mass fraction ratio) from 0.7 to 1.5 and Ce_2O_3 content (mass fraction) from 0 to 45% of the ternary slag at 1773 K, the results show that trends of calculated N_(Al_2O_3) are in good agreement with reported measured trends of a_(Al_2O_3). The iso-curves of N_(Ce_2O_3) and N_(CaO) are also drawn from the calculated results. A thermodynamic model of the equilibrium between 55.83%CaO-23%Al_2O_3-11.17%SiO_2-10%Ce_2O_3 quaternary slag and molten steel containing aluminum has been further discussed. Results indicate that certain content of Ce would be dissolved in steel, which increases with the increasing of temperature and aluminum content, and when the aluminum content is 0.02%, the corresponding cerium content is in the range of 1.87 to 13.30 ppm at 1873 K. In summary, using Ce_2O_3 to replace Al_2O_3 can effectively reduce N_(Al_2O_3), certain content of Ce can dissolved in steel.