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Removal of alkali metals and alkaline earth metals from molten aluminum

  • US 4,470,846 A
  • Filed: 01/06/1983
  • Issued: 09/11/1984
  • Est. Priority Date: 05/19/1981
  • Status: Expired due to Term
First Claim
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1. A method of removing contaminant alkali metals and alkaline earth metals from aluminum by bringing the aluminum, in molten state having the contaminants dissolved therein, into contact with particulate aluminum-fluoride-yielding material, said method comprising:

  • (a) delivering said particulate material to the surface of a body of the molten aluminum contained in a vessel having a geometric axis,(b) stirring the molten body for creating and maintaining a vortex therein to draw the delivered particulate material into mixture with the molten aluminum, thereby to effect reaction of the particulate material with the dissolved contaminants, the stirring step being performed by rotating, in a plane of rotation and about an axis of rotation, an impeller having a plurality of blades immersed in the molten body,(c) continuing the stirring of the molten body until the content of said dissolved contaminants therein is reduced at least to a predetermined low level, and(d) separating the molten aluminum of the body from products of reaction of the contaminants with the fluoride;

    (e) wherein the vessel has a minimum internal diameter D, and is filled with the molten body to a height H, and the impeller has a diameter d and a blade height h, such that the ratio d/D is between 0.1 and 0.6 and the ratio h/H is between 0.1 and 0.7, D and d being measured in the plane of impeller rotation, and H and h being measured along the axis of impeller rotation.

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