Disproportion reaction of silica in vacuum metallurgy of aluminum

The thermodynamic formation and disproportion reaction of sub silicon-oxide, in aluminum vacuum extraction with subfluride, was analytically studied by 'Substance Gibbs' Free Energy Functional Determinant' scheme. The results show that the pressure significantly affects the formation temperature of the sub silicon-oxide. For instance, at 100 kPa, the formation temperature is 1937 K;and at a pressure interval of 100Pa to 10Pa, the temperature ranges from 1463 K to 1352 K. At 150Pa and at 1450°C, 95.13% pure aluminum with 4.87% silica impurity can be obtained in vacuum extraction of aluminum with subfluride. The calculated results were found to agree very well with the experimental ones.