Aluminum Reduction Technology: Cell Technology and Operations
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Kristian Etienne Einarsrud, Norwegian University of Science and Technology; Stephan Broek, Kensington Technology Inc; Mertol Gokelma, Izmir Institute of Technology; Dmitry Eskin, Brunel University
Monday 2:00 PM
February 28, 2022
Room: 211A
Location: Anaheim Convention Center
Session Chair: Andre Felipe Schneider, Hatch
2:00 PM Introductory Comments
2:05 PM
Restart of Copper-insert Pots in EGA's High Amperage Potlines: Ali Jassim1; Pradeep Kalidindi1; Shaikha Al Shehhi1; Najeeba Al Jabri1; Abdallah Rahbar1; Nadia Ahli1; 1EGA
Good performance in pot preheat, start- up and early operation is key for pot life in long run. However, instances shall be encountered where few pots might need to be cut out earlier than expected potlife due to power outage or to abnormal pot condition in early operation or later. Copper-insert collector bars have become a requisite for lining design to improve energy efficiency. Restart experience of copper-insert pots is different than of pots with conventional steel collector bars. Experience in start-up of copper-insert pots is captured in detailed systematic procedures, such as collector bar resistance measurement, taken on cavity cleaned cathode, and pot restart economic study estimating the cost of restart and expected pot life to payback. Procedures detailing the activities and parameter changes required during pot cut-in, preheat control and stabilization period during early life are presented in this paper.
2:30 PM
Strategic Training and Development of Smelter Teams to Improve Business Outcomes: David Emerson1; Leo Ruffo1; Barry Sadler1; Dave Umbaugh1; 1SCCR Training & Development
Training and development of technical and operational staff are often undertaken as knowledge improvement exercises with success criteria based on information retention. A better approach is to strategically position training and development to balance resources, risk, and financial performance. This can be done by: (1) Using experienced smelter experts to review current plant performance and identify, then quantify, technical/ financial opportunities, (2) Aligning senior management on a strategy for organizational performance to deliver the critical business needs and opportunities, (3) Enhancing training materials with site information, (4) Interactive training to develop solutions/build confidence, (5) Developing and executing plans to deliver target outcomes, with all levels of management aligned, (6) Working with teams to clarify roles and accountabilities to embed gains, (7) Mentoring, coaching and providing expert, on-demand advice to develop capability, and (8) Sustaining improved performance by verifying individual/team results. This approach is demonstrated using working case information.
2:55 PM
Concentration Distribution of Carbon Particles in Aluminium Electrolysis Cells: Matthias Dechent1; 1Trimet Aluminium SE
Process control systems and process simulations of aluminium electrolysis oven performance generally assume a homogeneous electrolyte distribution. In reality, concentration gradients in the aluminium cells are common due to insufficient mixing. The distribution of carbon particles in the bath was compared between “clean” and “dusty cells”, which were defined as having dust in the tap hole and anode hole. Simultaneously, physical Anode-Cathode-Distance (ACD) measurements were conducted to study a possible association of the anode cathode distance and the local carbon content in the electrolyte.
3:20 PM Break
3:35 PM Student
Stabilizing a Low-dimensional Model of Magnetohydrodynamic Instabilities in Aluminum Electrolysis Cells: Ibrahim Mohammad1; Douglas Kelley1; 1University of Rochester
Aluminium (Al) is produced in electrolysis cells that contain two molten, broad and shallow layers, Al beneath cryolite (bath). A magnetohydrodynamic (MHD) instability known as the metal pad instability (MPI) has been a barrier for reducing anode-to-cathode (ACD) distance and thus decreasing electric losses. The MPI arises from the electromagnetic forces amplifying gravity waves with similar frequencies present at the Al-bath interface. Davidson and Lindsay suggested a mechanical model of the MPI in the form of a compound pendulum with a steady electric current running through it that, in the presence of a vertical magnetic field, couples the pendulum's motion in the two directions. We expand this model to test whether adding an oscillating (AC) current can stabilize the pendulum's motion and consequently have the potential to stabilize Al electrolysis cells. We show that AC current can indeed stabilize the motion, and that stability depends in a complicated way on AC amplitude and frequency.
4:00 PM
An Attempt to Estimate the Sulfuric Acid Dewpoint in the Flue Gas from Aluminium Electrolysis Cells: Asbjorn Solheim1; 1SINTEF Industry
The sulfuric acid dewpoint in the flue gas from aluminium electrolysis cells increases with increasing concentrations of sulfur dioxide and water vapour. This represents a potential problem in a future scenario with reduced air draught for increased carbon dioxide capture and heat exchangers for cooling or heat collection. A pragmatic model was derived, based on kinetics for the sulfur dioxide to trioxide conversion and models for estimating the temperature and air penetration into the flame. The results indicate that oxidation of carbon monoxide as well sulfur dioxide takes place mainly less than 10 cm above the crust opening. The dewpoint increases with decreasing current efficiency and with increasing area and diameter of the crust openings. In the base case, which was thought to be representative for a modern prebake cell, the dewpoint was 73 °C. The dewpoint may increase if sulfur trioxide is refluxed with the secondary alumina.