Critical thermodynamic evaluation of oxide systems relevant to fuel ashes and slags. Part 1: Alkali oxide–silica systems

The associate species model was applied to the thermodynamic representation of the liquid in oxide systems Na2O–SiO2 and K2O–SiO2. The available phase diagram and activity data were collected and evaluated for the purpose of improving the solution database. These new data for the liquid phase are compatible with data for the solid stoichiometric compounds from the FACT Pure Substance database. The phase equilibria calculated using the new optimised solution data show good agreement with the experimental points. Furthermore, the experimental activities are well reproduced. In contrast to other databases the new dataset allows the description of the whole composition range including the region near the pure alkali oxides.