Aluminum Reduction Technology Joint Session with REWAS: Decarbonizing the Metals Industry: Sustainability Joint Session with REWAS
Sponsored by: TMS: Recycling and Environmental Technologies Committee, TMS: Aluminum Committee
Program Organizers: Mertol Gokelma, Izmir Institute of Technology; Stephan Broek, Kensington Technology Inc
Tuesday 8:00 AM
March 1, 2022
Room: 210C
Location: Anaheim Convention Center
Session Chair: Stephan Broek, Hatch
8:00 AM Introductory Comments
8:05 AM
Cooling of Pot Gas Enabling Carbon Footprint Reductions: Anders Sorhuus1; Håvard Olsen1; Mikkel Sørum1; Guillaume Girault2; 1REEL Norway AS; 2REEL
Several technologies for pot gas cooling have been developed over the past decade to address detrimental effects such as reduced filter bag life and increased stack emissions from the Gas Treatment Centres (GTCs). In this context, the REEL range of water-cooled pot gas heat exchangers, MHEX, IHEX and EHEX, have proven success in achieving the required gas cooling, providing at the same time GTC capacity improvements . These HEX technologies also allow significant reduction in the plant carbon footprint, either indirectly by utilization of waste heat replacing other carbon based energy sources, or directly by reducing carbon based electrical power consumption for operation of the main fans.Waste heat from the HEX may also enable carbon capture solutions (CCS) either as source of energy for CCS process, or as part of the process to concentrate the pot gas with the so called Pot Gas Recirculation (PGR) solution. Each solution will be discussed, and potential carbon reductions are estimated in the paper.
8:25 AM
Bus Bars FSW Repair during Full Operation of Alumina Electrolysis: Peter Brziak1; Gabriel Batista1; Oliver Rovný1; Vojtech Václav1; Rastislav Dankoviè1; 1Welding Research Institute
The electrolyser bus bars, as any other part of production process, need maintenance, repair, or replacement when necessary. To decrease the current loses caused by poor bus bars interconnections, the fusion welding is used widely. However magnetic field generated by DC current make fusion welding impossible when electrolysis is operating. On the other hand, even temporary electrolysis shut down brings along several problems when process is starting up again. Direct and indirect economical loses relate for example to an increased energy consumption and decreased remanet life of some components. The article deals with solid-state welding process fully convenient for weld repair in electrolysis hall during full operation of all electrolysers. Laboratory experiments followed by pilot repair welding during electrolysis operation employing portable welding device proved the expected weld quality mainly in terms of mechanical properties and resistivity.
8:45 AM
Stabilizing Electrolysis Cells with Oscillating Currents: Amplitude, Frequency and Current Efficiency: Ibrahim Mohammad1; Marc Dupuis2; Paul Funkenbusch1; Douglas Kelley1; 1University of Rochester; 2GeniSim Inc.
The metal pad instability (MPI) imposes a minimum electrolyte layer thickness for stable operation of aluminium electrolysis cells, which limits cells' energy efficiency. The MPI is a magnetohydrodynamic process that depends on a coupled resonance between hydrodynamic gravity wave modes, driven by the cell's electrolytic current, appearing as a circulating traveling wave that grows exponentially. Adding an oscillating current component, whose frequency is close to a low-frequency gravity mode instead excites standing waves that can prevent the MPI. Here, we show that the a minimum oscillation amplitude is required for preventing the MPI, but excessive amplitude causes a wave that shorts the cell. Proper oscillation frequency choice also impacts the stabilization effect. We also discuss the impact of exciting standing waves on the current efficiency of the cell. Applying oscillating currents could significantly increase the energy efficiency of Al cells without the need for expensive reconstruction, paving the way towards more efficient, low carbon Al production.