Aluminum Reduction Technology: Modelling and Cell Design, Potroom Operations
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Mark Dorreen, Light Metals Research Centre, The University of Auckland

Wednesday 2:00 PM
March 1, 2017
Room: 2
Location: San Diego Convention Ctr

Session Chair: Marc Dupuis, GeniSim; Olivier Martin, Rio Tinto

2:00 PM Introductory Comments

2:05 PM  
Improving the Understanding of Busbar Design and Cell MHD Performance: Alexander Arkhipov1; Abdalla Zarouni1; Amal Al Jasmi1; Vinko Potocnik1; 1Emirates Global Aluminium (EGA)
    Good busbar design is of paramount importance for aluminium reduction cell performance. Busbar design has tremendous impact on cell MHD-stability, without which it is difficult to achieve high current efficiency and low energy consumption since instabilities enhance the rate of back reaction and make pot control more difficult. Many aspects of busbar design and MHD-stability are still grey areas in which cell designers do not have full confidence because MHD criteria are still rather qualitative. EGA has developed cell design capabilities, including busbar design. During the last six years, EGA has developed about ten busbar designs for new and retrofit potlines. In some cases, the constraints led to sub-optimal busbar design for cell stability in practice. This experience enhanced our understanding of the busbar design, MHD modelling and measurements, which we share in this paper and discuss criteria for busbar temperature, current density and vertical magnetic field bias.

2:30 PM  
MHD of Large Scale Liquid Metal Batteries: Valdis Bojarevics1; Andrejs Tucs1; 1University of Greenwich
    Liquid Metal Batteries (LMB) are possible candidates for large-scale energy storage in a national energy grid. The attraction of LMB lies in the fast kinetics at liquid metal-electrolyte interfaces, while the major drawback is their operation sensitivity to liquid motion caused mainly by electromagnetic forces. The concept of LMB bears a close similarity to aluminium electrolytic production cells (AEC). The two liquid layer magnetohydrodynamic effects can be projected to the three liquid layer self-segregated structure of LMB. The trend for commercial AEC is to increase their size instead of operating a large number of parallel small ones. Our aim is to develop a numerical model for the three density-stratified electrically conductive liquid layers using 3d and shallow layer approximation accounting for specific MHD effects during periods of battery charge/discharge. A possibility to reuse infrastructure of an old AEC potline for a large scale LMB facility is discussed.

2:55 PM  
Low Energy Consumption Cell Designs Involving Copper Inserts and an Innovative Busbar Network Layout: Marc Dupuis1; 1GéniSim Inc
    Two innovations presented by the authors recently at ICSOBA conferences allow to very significantly reducing both the cathode and the busbar voltage drop [1,2]. This paper combines the usage of those two innovations with the usage on the new anode stub hole design presented at the Aluminiun of Siberia conference [3] to come up with a very low energy consumption cell design.

3:20 PM  
LES Turbulence Modeling Approach for Molten Aluminium and Electrolyte Flow in Aluminum Electrolysis Cell: Mounir Baiteche1; Seyed Mohammad Taghavi1; Donald Ziegler2; Mario Fafard1; 1Aluminium Research Center REGAL, University Laval; 2Alcoa Primary Metals, Alcoa Technical Center
    In the Hall-Héroult electrolysis cell for aluminum production, understanding hydrodynamic phenomena induced by the magnetic field is very important for process stability and performance in terms of aluminum production and energy efficiency of the cell. The study of these phenomena requires mathematical modeling of the flow of liquid aluminum and the electrolytic bath under the operational conditions of the cell. The problem involves solving two equations systems for two immiscible stratified fluids where the movement is primarily subject to the effects of gravity, pressure force, shear stresses and of course the electromagnetic forces. The characteristic length scale of flow is very different in the three directions of the cell geometry. Then the turbulence estimation for flow modeling is an arduous task. In this study, numerical investigations are made in order to investigate the applicability of Large Eddy Simulation turbulence models to represent well the magnetohydrodynamic turbulence in the electrolysis cell.

3:45 PM Break

4:00 PM  
Surviving an Extended Power Outage after a Break Down in the Sub Station: Till Reek1; Roman Düssel1; 1TRIMET Aluminium SE
    TRIMET Aluminium SE operates the Essen aluminium smelter with 3 potlines in Germany. On April 12th 2016 a smoke alarm in the substation triggered an emergency shutdown of the whole plant. The smoke alarm was caused by a short circuit on a 21kV bus bar. While potline 2 and 3 could be restarted within 2 hours, the damaged bus bar had to be removed, separating potline 1 from the redundant high voltage power supply and fixing it on a single 220kV transformer. When potline 1 was to be restarted, the 220kV transformer was found to have a faulty insulation. An emergency bus bar replacement was welded in place and potline 1 could be re-energized after 5 hours 50 minutes. Due to immediate steps taken in the pot rooms, any pot loss could be prevented and the potline was operating normally 12 hours later.

4:25 PM  
Retrofit of Damaged Corner Risers by Means of Bolted Connections: Andre Felipe Schneider1; Donald Ziegler2; Maxime Pouliot2; Daniel Richard1; Jason Robillard1; Jeremie Blais1; Olivier Charette1; Pouya Zangeneh1; 1HATCH Ltd.; 2Alcoa Primary Metals
    Unlike pot-to-pot cathode busbars, often protected by the potroom working floor (or gratings), risers are usually exposed to accidental collisions with pot tending machine tools, anode assemblies, crucibles and even heavy vehicles. The tap end corner risers of several pots located immediately after the passageways of the Baie-Comeau Smelter’s Potline D had been damaged throughout the years, which led to the mechanical failure of a considerable amount of the welded plates connecting said risers to the passageway liaison conductors. The retrofit of damaged pot-to-pot conductors is traditionally based on welding techniques, often requiring bypass bridges or potline shutdowns. In the fall of 2015, an integrated Alcoa-Hatch multidisciplinary team succeeded to safely replace one of these risers, without production downtime or auxiliary conductors, by resorting to bolted connections in lieu of standard welded joints. This unique piece of equipment has been operating consistently within target for about 10 months.