Alumina Solubility and Diffusion Coefficient of the Dissolved Alumina Species in Low-Temperature Fluoride Electrolytes

作者：Frazer E J^*; Thonstad J

来源：Metallurgical and Materials Transactions B-Process Metallurgy and Materials Processing Science, 2010, 41(3): 543-548.

DOI：10.1007/s11663-010-9360-x

The solubility of alumina was measured by rotating an alumina cylinder (similar to 500 rpm) in a high-purity melt for similar to 3 to 6 hours, crushing and sampling the frozen melt, and determining the oxygen content in a Leco analyzer. The alumina solubilities determined were as follows: (1) 3.2 +/- 0.3 wt pct in NaF-AlF(3) eutectic at 1023 K (750 degrees C); (2) 3.0 +/- 0.3 wt pct in NaF-AlF(3)-CaF(2) (5 wt pct) at 1023 K (750 degrees C); and (3) 5.2 +/- 0.5 wt pct in a KF-AlF(3) eutectic at 1003 K (730 degrees C). The alumina solubility in the KF-AlF(3) eutectic was 2 wt pct more than in the sodium analogue, offering the possibility of operating a low-temperature aluminum smelting cell without the need for an alumina slurry. The diffusion coefficient of the dissolved alumina species was determined in the NaF-AlF(3) eutectic at 1023 K (750 degrees C) using the rotating disc method and applying the Levich equation. Through a limited range of rotation rates, the system seemed to be mass-transfer controlled, and the diffusion coefficient was estimated to be in the range 1.8 to 2.2 x 10(-6) cm(2) s(-1). This value is about five times lower than the values encountered at traditional aluminum smelting temperatures (similar to 1233 K (960 degrees C)) and would result in relatively low mass transfer coefficients.

• 出版日期2010-6
• 单位CSIRO