Selective Adsorption of Sodium Aluminum Fluoride Salts from Molten Aluminum

Technical Report · Thu Aug 16 00:00:00 EDT 2007

DOI:https://doi.org/10.2172/912665· OSTI ID:912665

Aubrey, Leonard S; Boyle, Christine A; Williams, Eddie M; DeYoung, David H; Smith, Dawid D; Chi, Feng

Aluminum is produced in electrolytic reduction cells where alumina feedstock is dissolved in molten cryolite (sodium aluminum fluoride) along with aluminum and calcium fluorides. The dissolved alumina is then reduced by electrolysis and the molten aluminum separates to the bottom of the cell. The reduction cell is periodically tapped to remove the molten aluminum. During the tapping process, some of the molten electrolyte (commonly referred as “bath” in the aluminum industry) is carried over with the molten aluminum and into the transfer crucible. The carryover of molten bath into the holding furnace can create significant operational problems in aluminum cast houses. Bath carryover can result in several problems. The most troublesome problem is sodium and calcium pickup in magnesium-bearing alloys. Magnesium alloying additions can result in Mg-Na and Mg-Ca exchange reactions with the molten bath, which results in the undesirable pickup of elemental sodium and calcium. This final report presents the findings of a project to evaluate removal of molten bath using a new and novel micro-porous filter media. The theory of selective adsorption or removal is based on interfacial surface energy differences of molten aluminum and bath on the micro-porous filter structure. This report describes the theory of the selective adsorption-filtration process, the development of suitable micro-porous filter media, and the operational results obtained with a micro-porous bed filtration system. The micro-porous filter media was found to very effectively remove molten sodium aluminum fluoride bath by the selective adsorption-filtration mechanism.

• Research Organization: SELEE Corporation
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: FC36-00ID13899
• OSTI ID: 912665
• Report Number(s): DOE/ID13899; TRN: US200801%%1134
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
ADSORPTION
ALLOYS
ALUMINIUM
CALCIUM
CALCIUM FLUORIDES
ELECTROLYSIS
ELECTROLYTES
FILTRATION
FLUORIDES
FURNACES
MAGNESIUM
REMOVAL
SODIUM
SURFACE ENERGY
selective adsorption
sodium aluminum fluoride
bath
salt
micro-porous
wetting
non-wetting
Na pickup
chiolite
cyrolite
filtration
interfacial surface energy
bed filter