Aluminum is one of the main impurity elements in silicon.The method of removing aluminum contained in silicon by vacuum directional solidification has been widely applied for industrial polycrystalline silicon purification.The purification experiment was conducted in a 500 kg ingot furnace used in industrial production with the raw material of silicon whose purity and aluminum content were 99.98%and 1.54×10-6

respectively.The experimental results demonstrate that the aluminum removal effect exhibits obvious

where the aluminum content can be reduced to a lowest value of 2.8×10-8

and a removal efficiency of 98.2% can be reached.After analyzing the process of aluminum removal

it is considered that in the process of purification experiment by employing ingot furnace

the removal of aluminum impurity is mainly completed under the co-action of dephlegmation mechanism in the process of directional solidification purification and vacuum volatilization mechanism