Study on the effective distribution coefficient of impurity separation in the preparation of high purity aluminum

Abstract

Effective distribution coefficient (ke) plays an important role in zone melting purification but has never been systematically calculated as an important parameter. A novel analysis method for impurity separation separating from Al using determination of impurities (Si, Fe, Cu, Zn) content and calculation of ke has been investigated. Experimental results show that the impurity separation effect was significantly improved due to the ke closely approximating the equilibrium distribution coefficient (k0) via optimization of purification times and speed of the melting zone. When the times of purification were increased from 15 to 20 times, the ke values of Si, Fe, Cu, and Zn at the sample (No. 3) were 0.603, 0.702, 0.364, and 0.502, respectively. Correspondingly, the removal rate of impurities of Si, Fe, Cu, and Zn increased by 6.25%, 1%, 10.49%, and 27.58%, respectively. The effect on the ke of Cu and Fe is more significant at the sample (No. 3) when the melting zone speed is changed. The removal rates of Fe and Cu in the sample are 99.0% and 94.75% when the melting zone speed was 1/3 mm/min, and, correspondingly, the removal rates of Si and Zn were 81.7% and 88.51%, respectively. The Al content at sample position No. 3 is more than 999994.59 ppm when the sample was purified 15 times at a speed of 0.5 mm/min, which meets the standard of 5N high purity aluminum.