Experimental studies on improvement of efficiency of aluminium reduction cells

Experimental studies on improvement of efficiency of aluminium reduction cells

Funder

Rio Tinto Aluminium Pechiney

Collaborators

Rio Tinto Aluminium Pechiney

Team

Dr Alex Pedcenko, Dr Ijhar Rusli

Duration

September 2018 to January 2021


Project overview

This project targets one of the issues occurring during the production of primary Aluminium. Aluminium is produced by electrolysis in “Hall–Héroult process”, which is the major industrial process for aluminium smelting. It involves dissolving aluminium oxide (alumina, bauxite ore) in molten cryolite, and electrolysing the molten salt bath in a reduction cell.

On average it takes about 15 kWh of electricity to reduce one kilogram of aluminium from alumina. The amount of energy used by this process worldwide is huge, about 1011 kW/yr, nearly 50% of which are Joule losses in the electrolyte. Reducing electrolyte thickness (ACD) leads to huge energy savings, however after reaching a critical ACD (< 4 cm) two immiscible liquids (cryolite and molten Aluminium) start to produce instability at the interface, which manifest itself as a “rolling” surface wave, -- the result of electromagnetic force between huge anode current and background magnetic field, a.k.a. magnetohydrodynamic (MHD) instability.

Project objectives

Looking at the impact of different technological factors on the stability of a reduction cell.

During previous collaboration between Rio Tinto, Coventry and Warwick universities (2007-2013), a small laboratory model of the cell was created, which uses low melting point liquid metal alloy (In-Ga-Sn) to model liquid aluminium. Such “physical model” allowed the surface instability phenomenon occurring in aluminium electrolysers to be reproduced in laboratory experiment for the first time.

The current project is a continuation of these studies, exploring the influence of a different set of technological factors on the flow of liquid metal and the stability of its interface.

Impact

The results of these studies would allow Rio Tinto to reduce the number of very expensive tests on real electrolysers, and eventually to improve the operation of their plants. The ultimate goal in reducing the thickness of electrolyte without compromising the stability of the cell, will allow to save huge amount of energy worldwide and make aluminium production cheaper.

Outputs

Internal reports, subject to NDAs

Previous publications from these studies:

Pedcenko, A., Molokov, S., & Bardet, B. (2016). The Effect of “Wave Breakers” on the Magnetohydrodynamic Instability in Aluminum Reduction Cells. Metallurgical and Materials Transactions B, 48(1), 6-10. https://doi.org/10.1007/s11663-016-0840-5

Pedcenko, A., Molokov, S., Priede, J., Lukyanov, A., & Thomas, P. J. (2009). Experimental model of the interfacial instability in aluminium reduction cells. Europhysics Letters, 88(2), [24001]. https://doi.org/10.1209/0295-5075/88/24001 

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