Decarbonization process for carbothermically produced aluminum
A method of recovering aluminum is provided. An alloy melt having Al 4 C 3 and aluminum is provided. This mixture is cooled and then a sufficient amount of a finely dispersed gas is added to the alloy melt at a temperature of about 700° C. to about 900° C. The aluminum recovered is a decarbonized carbothermically produced aluminum where the step of adding a sufficient amount of the finely dispersed gas effects separation of the aluminum from the Al 4 C 3 precipitates by flotation, resulting in two phases with the Al 4 C 3 precipitates being the upper layer and the decarbonized aluminum being the lower layer. The aluminum is then recovered from the Al 4 C 3 precipitates through decanting.
1. A method comprising:
(a) carbothermically preparing an aluminum alloy melt comprising Al 4 C 3 precipitates and aluminum metal;
(b) separating the aluminum metal from the Al 4 C 3 precipitates, wherein the separating step comprises:
introducing a gas into the aluminum alloy melt with a rotating disperser while the aluminum alloy melt is at a temperature of 700° C. to 900° C.;
tamping the Al 4 C 3 precipitates on the surface of the aluminum alloy melt to push the Al 4 Cl 3 precipitates below the surface, into the aluminum alloy melt; and
(c) recovering the aluminum metal from the melt.
2. The method of claim 1 , wherein recovering step (c) comprises:
decanting, sub-surface or vacuum tapping the aluminum to a receiver.
3. The method of claim 1 , wherein the gas is an inert gas.
4. The method of claim 3 , wherein the inert gas used is either argon or carbon dioxide.
5. The method of claim 3 , wherein the inert gas used is nitrogen.
6. The method of claim 1 , wherein the carbothermically preparing step (a) comprises:
cooling the aluminum alloy melt.
7. The method of claim 6 , wherein the cooling step comprises:
cooling the aluminum alloy melt to a temperature of 700° C. to 900° C.
8. The method of claim 6 , wherein the cooling step comprises:
adding solid or liquid aluminum to the aluminum alloy melt.
9. The method of claim 1 , wherein the introducing step comprises:
transporting the Al 4 C 3 precipitates towards a surface of the aluminum alloy melt.
10. The method of claim 1 , wherein, concomitant to the carbothermically preparing step (a), the temperature of the alloy melt is at least 2000° C.
11. The method of claim 1 , wherein the introducing step comprises:
flowing the gas at a rate of 5 cm 3 per min per cm 2 of crucible cross-sectional area.
12. The method of claim 1 , wherein the introducing step comprises:
rotating the rotating dispenser at 100 to 250 revolutions per minute.