2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 7: Ionic Liquids & Energy Production
| Editors: | Kongoli F, Gaune-Escard M, Mauntz M, Rubinstein J, Dodds H.L. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 310 pages |
| ISBN: | 978-1-987820-30-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
< CD shopping page
Inert Anodes for Aluminium Electrolysis. A Sustainable Process?
Jomar Thonstad1;1NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY, Trondheim, Norway;
Type of Paper: Regular
Id Paper: 452
Topic: 13
Abstract:
In the present day, electrolytic process for aluminium production uses a fluoride electrolyte, in which alumina is dissolved. Having a carbon anode and a liquid aluminium cathode, CO2 is being evolved at the anode and aluminium is deposited at the cathode, according to the reaction:
½ Al2O3 + ¾ C = Al + ¾ CO2 which is operated at 960 °C.
Per each ton of aluminium produced, about 1.5 tons of CO2 are being emitted. Due to sulphurous impurities in the anode, the gas also contains SO2, COS, CS2, H2S.
By replacing the carbon anode by an inert, oxygen-evolving anode, the cell reaction will be:
½ Al2O3 = Al + ¾ O2
The exit gas will only be oxygen, together with some fluoride fumes.
To replace the carbon anode, inert anodes made of electronically conducting ceramics, cermets or metals (metal with oxide layer) can be used. All oxide materials have a finite solubility in the fluoride electrolyte, so that the anode will slowly dissolve, leading to contamination of the aluminium produced. To mitigate this problem, the electrolyte composition should be changed in order to lower the electrolyte temperature to about 800 °C. Various approaches on how to achieve that will be outlined.
Inert anode research is being conducted by major aluminium companies in USA, Russia and China and by research institutes and universities. Several cell designs have been proposed and tested. However, a major problem remains; metal contamination, and we are still searching for a final solution to this problem.
Keywords:
Electrochemical; Electrolysis; Oxygen; Technology;References:
[1] A.I. Belyaev and Ya. E. Studentsov, Legkie Metally 3 (1937) 17.[2] T.R. Beck, US Patent Appl. No. US 2003/0057102, March 27, 2003.
[3] T.R. Beck, US Patent 8,480,876 B2, July 9, 2013.
[4] T. Nguyen and V. de Nora, TMS Light Metals 2006, 385.