ISSN:
0001-1541
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Forced-convection mass transfer at the metal/bath interface during aluminum reduction from cryolitic melts was studied under reproducible convective conditions. A film of molten aluminum on a rotating molybdenum cylinder was the cathode. Concentration overpotential measured as a function of rotation rate, current density, and bath composition was converted to concentration differences between the bulk and the metal surface. Chosen as the basis for calculation of a mass transfer coefficient was the concentration of aluminum fluoride given by: \documentclass{article}\pagestyle{empty}\begin{document}$$ C_{{\rm AlF}_{\rm 3} } = \frac{{2\rho (100 - Al_2 {\rm O}_3 \% - {\rm CaF}_2 \% - IMP\%)}}{{100M_{{\rm AlF}_3} (CR + 2)}} $$\end{document} where the amounts of indicated compounds are in weight percent, IMP designates impurities, M is molecular weight, ρ is the density of the melt, and CR is the cryolite ratio, the ratio of moles NaF to moles AlF3. Agreement with a correlation for mass transfer to a rotating cylinder allowed the calculation of effective diffusivities for aluminum fluoride species, in alumina-saturated melts, of: 11.1 ± 1.1 × 10-5 cm2/s at 1.8 CR; 11.4 ± 1.7 × 10-5 cm2/s at 2.3 CR; 5.4 ± 0.8 × 10-5 cm2/s at 3.0 CR; and 4.4 ± 0.9 × 10-5 cm2/s at 4.0 CR.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/aic.690341008
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