Aluminum Reduction Technology: Reduction Cell Technology and Development
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Jayson Tessier, Alcoa Corporation
Thursday 2:00 PM
February 27, 2020
Room: 6D
Location: San Diego Convention Ctr
Session Chair: Espen Tjonneland Wefring, Hydro Aluminium
2:00 PM Introductory Comments
2:05 PM
The Australian Energy Crisis: Its Impact on Domestic Aluminium Smelting and Potential Solutions: David Wong1; Alton Tabereaux2; Mark Dorreen1; 1University of Auckland; 2Consultant
Australia is facing an ongoing energy crisis, driven by a combination of reducing ‘base-load’ power generation (aging coal-fired stations shutting down), policy uncertainty and hence lack of investment in new base-load capacity, and the rapid uptake of variable wind and solar generation that has yet to be fully buffered by energy storage. The resulting national grid is susceptible to unexpected shocks (reduced energy output from wind/solar, extreme weather, failure in grid interconnectors) and high spot-pricing. Unsurprisingly, Australia’s aluminium smelters are facing immense challenges operating in this environment, with potline outages occurring multiple times in two smelters over the past 3 years. This article examines some of the impacts and explores some of the pathways and opportunities that smelters can use to survive, including power modulation and the provision of ‘demand-side’ response services to the national energy grid.
2:25 PM
Recycling of the Flue Gas from Aluminium Electrolysis Cells: Asbjorn Solheim1; Samuel Senanu1; 1SINTEF Industry
Recycling of the flue gas from aluminium reduction cells is a possible method for increasing the CO2 concentration, thereby enabling CO2 capture. The present paper represents a preliminary study concerning some of the consequences in the electrolysis cells. The energy balance in a hypothetic 400 kA cell was estimated, and it turned out that the heat flow into the superstructure could be kept constant by decreasing the thickness of the anode cover material even with a very hot gas. Recycling gives a higher amount of collectible heat from the cells, mainly because of higher temperature in the gas entering the cell. It will be advantageous to apply catalytic burning of CO to CO2, which represents considerable extra heat. Increased sulphuric acid dewpoint may represent a challenge. It is also necessary to assess the amount of hydrogen fluoride that re-evolves from the secondary alumina at high superstructure temperature.
2:45 PM
Utilization of Waste Heat for Pre-heating of Anodes: Martin Grimstad1; Kim Ronny Elstad2; Asbjørn Solheim3; Kristian Etienne Einarsrud1; 1Norwegian University of Science and Technology; 2Alcoa Mosjøen; 3SINTEF Industry
Carbon anodes are replaced on a regular basis in Hall-Héroult cells as they are consumed by electrochemical reactions. Upon insertion of new anodes, bath will freeze locally as a result of low bath superheat and comparatively low anode temperature, creating an insulating layer on the anode surface, thereby delaying further production. In the current work the potential for pre-heating anodes directly utilizing waste heat from off-gas and spent anode butts is investigated using a numerical model realized in COMSOL and industrial measurements at Alcoa Mosjøen. Anode core temperatures over 150 C and surface temperatures over 250 C were found when using butts as a direct heat source. Frozen bath samples from both pre-heated and regular anodes were collected and analysed using computer tomography (CT) in order to assess how various heating strategies influences frozen bath morphology.
3:05 PM
Toward Minimizing the of Co-evolution of PFC Emission in EGA Smelter: Najeeba Al Jabri1; Ali Jassim1; Daniel Whitfield1; Sergey Akhmetov1; Barry Welch2; 1EGA; 2Welbank Consulting Ltd
Primary aluminum smelters are known to be a dominate source for the PFC emission where changes in spatial condition of Hall-Héroult reduction cell would result to the co-evolution of CF_(4 ). EGA smelters has undergo through various process and design upgrade program, which resulted in allowing creeping amperage to meet production requirements. Increasing production output are usually associated with reduction in bath to amperage ratio while aiming to operate at low energy input target. Sequentially, the company has developed a special program to enhance its advance cell control logic to allow operating at higher anode current density while maintaining low PFC emission. This paper investigates major activities where the co-evolution of PFC emission was detected as anode setting activity and condition of operating at low alumina concentration in electrolyte. In-house developed individual anode current along with continuous monitoring of PFC emission in reduction cell were deployed to validate the study.
3:25 PM Break
3:40 PM Cancelled
Research and Application of Direct Welding Technology on Super Large Section Conductor: Xudong Wang1; Xiaoqiang Feng1; Yingwu Li1; 1Zhengzhou Jingwei Technology
This paper focuses on steel-aluminum welding technology and full-section vertical welding technology about large section works, mainly used in aluminum reduction. Direct welding between steel and aluminum would easily generate brittle chemical compound and form cracks in the joints. A research shows that proper transition layer metal and wettability condition for brazing filler metal, with heat input management during welding process can effectively restrain compound formation and improve cracks tendency as well. Through numerous tests, factors that influence compound formation have been found, through which we can get good welding joints with shear strength above 110Mpa. Considering current shortcomings of traditional repair methods about large section works during aluminum reduction, this paper also comes up with a vertical welding technology whose joints have equal property of base metal. It adapts to large section welding between steel and steel, aluminum and aluminum. Actual practise proves that it already has application condition.