Phase III Advanced Anodes and Cathodes Utilized in Energy Efficient Aluminum Production Cells
During Phase I of the present program, Alcoa developed a commercial cell concept that has been estimated to save 30% of the energy required for aluminum smelting. Phase ii involved the construction of a pilot facility and operation of two pilots. Phase iii of the Advanced Anodes and Cathodes Program was aimed at bench experiments to permit the resolution of certain questions to be followed by three pilot cells. All of the milestones related to materials, in particular metal purity, were attained with distinct improvements over work in previous phases of the program. NiO additions to the ceramic phase and Ag additions to the Cu metal phase of the cermet improved corrosion resistance sufficiently that the bench scale pencil anodes met the purity milestones. Some excellent metal purity results have been obtained with anodes of the following composition: Further improvements in anode material composition appear to be dependent on a better understanding of oxide solubilities in molten cryolite. For that reason, work was commissioned with an outside consultant to model the MeO - cryolite systems. That work has led to a better understanding of which oxides can be used to substitute into the NiO-Fe2O3 ceramic phase to stabilize the ferrites and reduce their solubility in molten cryolite. An extensive number of vertical plate bench electrolysis cells were run to try to find conditions where high current efficiencies could be attained. TiB2-G plates were very inconsistent and led to poor wetting and drainage. Pure TiB2 did produce good current efficiencies at small overlaps (shadowing) between the anodes and cathodes. This bench work with vertical plate anodes and cathodes reinforced the importance of good cathode wetting to attain high current efficiencies. Because of those conclusions, new wetting work was commissioned and became a major component of the research during the third year of Phase III. While significant progress was made in several areas, much work needs to be done. The anode composition needs further improvements to attain commercial purity targets. At the present corrosion rate, the vertical plate anodes will wear too rapidly leading to a rapidly increasing anode-cathode gap and thermal instabilities in the cell. Cathode wetting as a function of both cathode plate composition and bath composition needs to be better understood to ensure that complete drainage of the molten aluminum off the plates occurs. Metal buildup appears to lead to back reaction and low current efficiencies.
- Research Organization:
- Alcoa Technical Center/Aluminum Company of America (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FC07-98ID13666
- OSTI ID:
- 794978
- Report Number(s):
- DOE/ID/13666; TRN: US200211%%80
- Resource Relation:
- Other Information: PBD: 5 Nov 2001
- Country of Publication:
- United States
- Language:
- English
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