Refining of metallurgical grade silicon

Details Refining of metallurgical grade silicon Refining of metallurgical grade silicon

C - Chemistry, Metallurgy

01

B

C01B 33/037 (2006.01) H01L 31/18 (2006.01)

Patent

CA 2393511

The invention relates to a method for purification of metallurgical grade silicon where a calcium containing compound is added to molten silicon prior to or after the silicon is tapped from the furnace. The silicon is cast and solidified at a relatively high cooling rate and the solidified silicon is crushed and subjected to a purification process consisting of two leaching steps. In the first leaching step the silicon is treated with an aqueous solution of FeCl3 or FeCl3 and HCl which causes disintegration of the silicon, and in the second leaching step the silicon is treated with an aqueous solution of HF or HF/HNO3. Calcium-containing compound is added to the molten silicon in an amount necessary to provide between 0.3 and 0.95 % by weight of calcium in the molten silicon and the weight ratio between Al and Fe in the molten silicon is regulated to between 0.5 and 2.0 by addition of aluminum to the molten silicon.

L'invention concerne un procédé de purification de silicium de qualité métallurgique, qui consiste à ajouter un composé au calcium à du silicium fondu avant ou après le récupération dans le fourneau. Le silicium est moulé et solidifié à un taux de refroidissement relativement élevé, puis broyé et purifié suivant deux étapes de lixiviation: on traite d'abord le silicium avec une solution aqueuse de FeCl3 ou FeCl3 et de HCl aux fins de désintégration, puis on traite le silicium avec une solution aqueuse de HF ou de HF/HNO3. Le composé au calcium est ajouté au silicium fondu en quantité nécessaire pour établir, en poids, entre 0,3 et 0,95 % de calcium dans ledit silicium fondu, et le rapport de poids entre Al et Fe dans le même silicium fondu est régulé entre 0,5 et 2 par adjonction d'aluminium au silicium fondu en question.

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