Method and apparatus for purifying a silicon feedstock

Details Method and apparatus for purifying a silicon feedstock Method and apparatus for purifying a silicon feedstock

C - Chemistry, Metallurgy

01

B

C01B 33/037 (2006.01) C01B 11/00 (2006.01) C30B 29/06 (2006.01)

Patent

CA 2758563

The invention relates to a method for purifying a silicon feedstock in order to obtain silicon with a higher purity. According to the invention, the following steps are carried out: a) a plasma cone generated by a first non-transferred arc torch (6) is directed onto a solid wall (7) of a space having an outlet opening such that the impact of the cone against said solid wall (7) generates a homogeneous plasma flow; b) a silicon feedstock to be treated, consisting of particles and/or grains or crushed, is continuously injected into said homogeneous plasma flow; c) the whole consisting of the homogeneous plasma into which the crushed feedstock was injected is continuously directed from the outlet opening towards a crucible (1) comprising a means for heating and agitating said crushed feedstock in the molten state; d) once the entire crushed feedstock has been injected and a molten pool (13) has been formed in the crucible (1), the reactive plasma jet of at least one second non-transferred arc torch is directed towards the surface of said pool; e) the slag on the surface (17) of said pool is removed, and steps d) and e) are optionally repeated in order to evaporate at least some of the impurities of the pool brought to the surface (17) of said pool by agitation.

L'invention concerne un procédé de purification d'une charge à base de silicium pour obtenir du silicium de pureté supérieure. Selon l'invention, on réalise les étapes suivantes : a) on envoie un dard plasma généré par une première torche à arc non transféré (6) contre une paroi pleine (7) d'un volume ayant un orifice de sortie de sorte que l'impact du dard contre cette paroi pleine (7) génère un écoulement plasma homogène, b) on introduit de manière continue une charge à traiter à base de silicium constituée de particules et/ou de grains, ou broyée dans ledit écoulement plasma homogène, c) on dirige de manière continue l'ensemble formé par l'écoulement plasma homogène dans lequel a été introduite la charge broyée de l'orifice de sortie vers un creuset (1) comportant des moyens pour chauffer et brasser cette charge broyée à l'état fondu, d) l'intégralité de la charge broyée ayant été introduite et un bain de fusion (13) étant formé dans le creuset (1), on dirige le jet de plasma réactif d'au moins une deuxième torche à arc non transféré sur la surface de ce bain, e) on évacue le laitier présent à la surface (17) dudit bain, et on répète éventuellement les étapes d) et e) pour volatiliser au moins certaines des impuretés du bain amenées à la surface (17) dudit bain par brassage.

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