Activity Model and Its Application in Quarternary System CaO-FeO-SiO2-WO3

The activity model of CaO-FeO-SiO2-WO3 quarternary system is built according to the coexistence theory of slag structure and the reduction thermodynamics of scheelite is discussed by using this model. The activities of SiO2 and WO3 decrease, while the activity of CaO increases with increasing the basicity of slag. Among SiC, carbon and silicon reactants, the reducing capability of SiC is the strongest, while that of carbon is the poorest at high temperature (about 1873 K). Increasing the content of silicon or carbon is beneficial for increasing the yield of tungsten. Oxidizability of slag has a significant effect on the yield of tungsten. Controlling basicity and oxidizability of slag can decrease the oxidation loss of tungsten.