A novel inert alloy electrodes for aluminium smelting

Completed

Energy Efficiency(Industry)

Basic and strategic applied research

PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials)

Not Cross-cutting

Professor A Jha
Institute of Materials Research
University of Leeds

3

Carbon Trust

01 December 2003

30 November 2004

12 months

£99,870

Yorkshire & Humberside

Professor A Jha, Institute of Materials Research, University of Leeds

The objective of the project is to develop alloy-based inert anodes for the smelting of aluminium that will eliminate the emission of perfluoro-carbons (PFCs) and greenhouse gases like CO2.

Primary aluminium is produced via the electrolytic smelting of refined aluminium oxide. When aluminium oxide is dissolved in liquid cryolite electrolyte in a Hall- Heroult Cell at ~950 C, the alumina dissociates into Al3+ and O2- ions. Electricity flowing through the cell causes Al3+ ions to migrate to a wettable cathode, where they are reduced to pure aluminium, and O2- ions to a carbon anode where they are oxidised to oxygen. At the temperatures involved, this oxygen combines with the carbon in the anode to produce CO2, a greenhouse gas, and the electrode is also consumed. It is also a characteristic of the cell that on start-up PFCs are emitted. Researchers at the University of Leeds have identified an inert alloy that can replace carbon as the anode material in aluminium smelting, thereby avoiding direct CO2 emissions. These alloys have the correct properties of physical stability, high temperature corrosion resistance and high electrical conductivity required in the cell.However, before the aluminium industry can consider these substitute materials, there needs to be a fundamental understanding of the electrochemical properties of these materials. Moreover, the electrodes' actual performance in electrolysis cells need to be validated in the lab. With funding from the Carbon Trust researchers will be able to do this. They will optimise the alloy system, so as to optimise the required physical properties, and carry out real electrolysis validation tests. Assuch, this work will raise the credibility of the replacement materials and aid their adoption within the primary aluminium producing community. Adopting these anodes would lead to CO2 savings other than those directly associated with electrolysis. It is estimated that lower energy consumption in fabrication of the electrodes, compared with their carbon counterparts, and a lower electricity consumption in the cell during electrolysis will yield a 63% reduction in CO2 emissions among UK primary aluminium smelters

01/01/07