Claims
- 1. A method of processing spent aluminum pot liner containing carbon, cyanide compositions, fluorides and inorganic oxides, comprising mixing the spent aluminum pot liner with iron oxide, forming an agglomerated material from the mixture of spent aluminum pot liner and iron oxide, heating the mixture of agglomerated material in a furnace in a reducing environment to form a molten material, oxidizing carbon in the pot liner and reducing the iron oxide to produce iron and a slag substantially free of cyanide and fluorides and off-gases including carbon oxides and fluorine, and treating the off-gases containing carbon oxides and fluorine to remove fluorine therefrom.
- 2. The method of claim 1, wherein the oxidation and reduction steps occur at temperatures in the furnace sufficient to destroy substantially all the cyanide compositions in the spent aluminum pot liner.
- 3. The method of claim 2, wherein furnace temperatures are in a range of about 1,350° to about 1,650° C.
- 4. The method of claim 2, wherein the off-gases are passed to a thermal oxidizer to oxidize organics which may have formed and remaining cyanide compounds, and to convert substantially any CO to CO2 in the off-gases.
- 5. The method of claim 4, wherein the off-gases from the thermal oxidizer is contacted with a liquid hydroxide to form a fluoride and remove substantially all the fluorine from the off-gases.
- 6. The method of claim 5, wherein the liquid hydroxide is NaOH.
- 7. The method of claim 1, wherein the iron oxide is selected from the group consisting of mill scale, blast furnace sludge, grinding swarf, and iron ore.
- 8. The process of claim 1, wherein at least some of the inorganic oxides in the spent aluminum pot liner are glass formers.
- 9. The method of claim 8, wherein at least some glass formers are added to the molten material and the glass formers are selected from the group consisting of coal boiler fly ash, coal boiler bottom ash, electric utility neutralization sludge, spent refractories and lime.
- 10. The method of claim 9, wherein the glass formers are selected from the group consisting of CaO, SiO2, Fe2O3, Al2O3, and MgO.
- 11. The method of claim 1, wherein the furnace is operated substantially free of air.
- 12. The method of claim 1, wherein the spent aluminum potliner has carbon present in the range of from about 12 percent by weight to about 50 percent by weight of the potliner and the agglomerated material has potliner present in the range of from about 21 percent by weight to about 46 percent by weight and iron oxide present in the range of from about 37 percent by weight to about 71 percent by weight.
- 13. A method of processing spent aluminum pot liner containing carbon, cyanide compositions, fluorides and inorganic oxides, comprising crushing the spent aluminum pot liner and adding iron oxide to form an agglomerated material, forming the agglomerated material into a molten material in an electric arc furnace having electrodes submerged in the molten material to provide a reducing environment during the furnace operation, operating the electric arc furnace in a reducing environment, oxidizing the pot liner while reducing the iron oxides to produce iron and a slag substantially free of cyanide compositions and fluorides and off-gases including carbon oxides and fluorine, and treating the off-gases in an air pollution control system and afterburner and a scrubber to produce NaF, water and a gas vented to the atmosphere free of cyanide compositions, fluorine and CO.
- 14. The method of claim 13, wherein the electric arc furnace is operated at a temperature above about 1,350° C.
- 15. The method of claim 13, wherein the agglomerated material is formed from spent aluminum pot liner and iron oxide crushed to pass through a 12 mesh screen.
- 16. The method of claim 13, wherein the spent aluminum potliner has carbon present in the range of from about 12 percent by weight to about 50 percent by weight of the potliner and the agglomerated material has potliner present in the range of from about 21 percent by weight to about 46 percent by weight and iron oxide present in the range of from about 37 percent by weight to about 71 percent by weight.
- 17. The method of claim 16, wherein the agglomerated material contains about 36% by weight spent aluminum pot liner and 52% by weight iron oxide.
- 18. The method of claim 17, wherein agglomerated material includes about 7% by weight glass formers.
- 19. The method of claim 18, wherein the agglomerated material includes about 5% by weight binder.
- 20. The method of claim 19, wherein the binders are selected from the group consisting of bentonite, Portland cement and mixtures thereof.
CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant to a contractual relationship between the inventors and the U.S. Department of Energy (DOE).
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
5286274 |
Lindkvist et al. |
Feb 1994 |
A |
5496392 |
Sims et al. |
Mar 1996 |
A |
5558690 |
Hnat et al. |
Sep 1996 |
A |
5711018 |
Hittner et al. |
Jan 1998 |
A |