On the anode effect in cryolite-alumina melts—IV. Gas composition and faradaic efficiency

✍ Scribed by F. Nordmo; J. Thonstad

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 457 KB
• Volume: 30
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(85)80121-3

✦ Synopsis

The anode gas evolved during anode etIbct (AE) in NasAlF,-AlsO3 melts consists essentiahy of CO, CO, and CFI. The gas composition was found to be very sensitive to the ahunina concentration and to the AE voltage. In laboratory cells the CF, content ranged from 80 % in putSed cryolite to less than 1% at I2 wt. 0/O AlsGs. The CFA content showed a maximum at around 60V. 00 was the predominant gaseous species in alumina-containing melts, arxounting for more than 80% of the gas. Faraday's law was obeyed during AE The faradaicanodic current eilIciency with respect to 0 and F was 80-85 %, being similar to that observed during normal electrolysis The carbon consumption increased by 40% during AE, as reflected by the high CO contents. In industrial aluminium cells the CF, content during AE averaged 16 %, which is higher than expected for the given alumina concentration range.