Aluminum Reduction Technology Across the Decades: An LMD Symposium Honoring Alton T. Tabereaux and Harald A. Øye: Alton Tabereaux Honorary Session: Reduction Cell Operation and Process Control - Joint session with Aluminum Reduction Technology
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Arne Ratvik, SINTEF; Marc Dupuis, GeniSim Inc.; Kristian Etienne Einarsrud, Norwegian University of Science and Technology
Tuesday 2:00 PM
March 16, 2021
Room: RM 28
Location: TMS2021 Virtual
Session Chair: Marc Dupuis, GeniSim Inc.
2:00 PM
Introductory Comments: Aluminum Reduction Technology Across the Decades: An LMD Symposium Honoring Alton T. Tabereaux and Harald A. Øye: Marc Dupuis1; 1GeniSim Inc.
Introductory Comments
2:05 PM
Alton Tabereaux: A Humble Individual Who Dedicates His Lifetime to Aluminum - An Aluminum Legend of Our Time: Xiangwen Wang1; 1Alcoa Corp
Dr. Alton Tabereaux, retired from Alcoa a long time ago, never quits the industry. He continues to be active in smelting technology advancement, and in serving the aluminum industry and light metals community in particular. He is world renown not only for his technical contributions to aluminum smelting technology, equally important also for his dedication in teaching and training younger generations, providing consultancy and technical support to operations. He serves the light metal industry with unique technical background and knowledge skills in areas from environment protection, helping to stewardship government policies, to strengthening aluminum society. In this special tribute session, I am humbly honored to present and for us together to renew our learning of Alton and his major technical achievements – looking back from his very early career as a young scientist at Reynolds Metal Co to later becoming the world renown industry icon.
2:45 PM
Awakening of the Aluminum Industry to PFC Emissions and Global Warming: Alton Tabereaux1; David Wong1; 1Consultant
In the 1990s the global warming potential (radiative forcing) of atmospheric perfluorocarbon (PFC) led to an increase of public concern about the effects of their accumulation in the Earth’s atmosphere. At that time PFCs were only considered to occur during anode effects in the aluminum industry. In recent years, PFC emissions have also been found to occur during normal operation periods, specifically below the computer anode effect detection voltage and particularly in modern high amperage cells, thereby negatively impacting the development of accurate global PFC inventories. The most recent break-through in understanding has been the rediscovery of “co-evolution” of perfluorocarbon gases and carbon oxide gases during both normal operation and anode effects. Work is underway currently to develop strategies to stop unaccounted PFC emissions from occurring in industrial aluminum cells and to include their emission with the total amounts reported.
3:05 PM
Application and Adaptability of MHD Stability Computation for Modern Aluminium Reduction Cells at Extreme Conditions of Low ACD: Valdis Bojarevics1; Marc Dupuis2; 1University of Greenwich; 2GeniSim Inc.
Modern aluminium production cells are pushed to the limits of high amperage at the lowest possible energy consumption. The linear MHD stability theory conditions of small amplitude wave perturbation, fixed magnetic field and electric current distribution, neglect of the large horizontal circulation velocities is not valid in the large cells. The program MHD-VALDIS is specifically designed to perform the full magnetic field update at all time steps in an economic and efficient way. The additional Lorentz force from the interaction of the full time dependent vertical magnetic field Bz and the horizontal currents Jy in the liquid metal leads to possibility to discover new types of instabilities in the low ACD and low metal level situations. The analysis for a generic 500 kA cell is presented, demonstrating the limitations of the linear stability estimates and the full nonlinear time dependent modelling to permit MHD stability.
3:25 PM
Investigation of Cyclic Process Variations within Hall-Héroult Reduction Cells: Jayson Tessier1; Samuel Duplessis1; 1Alcoa
The hundreds of aluminum reduction cells within an aluminum smelter are typically operated in an individual fashion. It is known that reduction cells from a single potline can have different behavior and performance depending on their different lining design, historical performance and/or set points for bath chemistry, temperature and electrical resistance. The pot operational state is generally characterized by a limited set of pseudo real time indicators and different variables, such as bath chemistry or temperature, manually sampled at low frequency, where consecutive samples can be separated by a few days. Smelting operators have designed process control systems and reaction procedures to cope with process variations, while not always acknowledging the cyclic variations characterizing the pot state. This paper sheds some light on cyclic operation parameters variations and how it can impact negatively control actions taken by the control system or the pot operators.
3:45 PM
In Line Cell Position and Anode Change Effects on the Alumina Dissolution: Valdis Bojarevics1; 1University of Greenwich
The newly developed modeling technique is implemented into the specialized software to treat the industrial cell operation practices of the anode changes. Alumina feeding at regular intervals requires optimization for the feed amount and timing intervals in situations where the large scale MHD circulation experiences abrupt restructuring. The alumina particles of various sizes are traced accounting for their inertia, drag in the turbulent flow, the electrolyte layer deformed shape, and the electromagnetic force at the location. The large-scale circulation is essential to achieve the desired uniform alumina composition over the whole cell, while the local bubble evolution contributes to the turbulence level and the enhanced dissolution of the particles. Individual particles gradually dissolve in the dependence of the local turbulent diffusion and the instantaneous concentration level below the saturation. The newly developed modeling technique is applied to illustrate possible optimization of the cell performance at an arbitrary location in pot-line.
4:05 PM
History of Computer Control of Aluminum Reduction Cells: Vinko Potocnik1; Michel Reverdy1; 1Vinko Potocnik Consulting
Computer control of aluminum reduction cells started in the early 1960s, first for voltage control by anode beam movement. Next came alumina feeding control by cell resistance monitoring. Invention of point breaking/feeding in prebake cells, combined with continuous overfeeding and underfeeding of alumina, invented in the 1970s, brought alumina concentration to 2-3%, an optimum for cell performance until today. Bath chemistry also became computer controlled by automatic feeding of AlF3. From these fundamentals, as the computer speed and capacity increased, the computer control became more sophisticated and intelligent in reaction to alumina quality, cell conditions and cell operation routines, with the aim to achieve constant target parameters in every cell of a potline. Prediction and practical elimination of anode effects reduced PFC emissions to minimum, for cleaner environment. In this paper we trace the computer control from the beginnings to the most recent applications of artificial intelligence and Industry 4.0.
4:25 PM Question and Answer Period