Aluminum Reduction Technology: Environment & Modelling
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Pierre Marcellin, Rio Tinto; Stephan Broek, Kensington Technology Inc
Thursday 8:30 AM
March 23, 2023
Room: 30E
Location: SDCC
Session Chair: Hervé Roustan, Rio Tinto
8:30 AM Introductory Comments
8:40 AM
Fundamentals of Pot Ventilation in Aluminum Smelters: Diego Oitaben1; Samaneh Poursaman1; Stephen Lindsay1; 1Hatch
The gases generated at the electrolytic cells (or pots) of modern aluminum smelters are collected with a network of ducts that connect each of the pots to a scrubber in order to keep the overall emissions to targets that are below regulatory limits. This pot ventilation has also an effect on the cell thermal balance and minimizes the exposure of workers to the pollutants from the pots.This paper explains the fundamentals of this ventilation process and describes a simplified approach for a quick verification of the gas flow at each pot. The paper also proposes a procedure for balancing the pot flows, which is the most basic practice for an optimum performance of the pot ventilation system.
9:05 AM
Evaluation of Methodologies for Assessment of SO3 Concentration in Industrial Off-gas: Thor Anders Aarhaug1; Ole Kjos1; Morten Isaksen2; Jan Olav Polden2; 1Sintef; 2Hydro Aluminium
Assessment of acid dew point in industrial off-gas has become increasingly important with strategies for heat recovery and use of more concentrated gas compositions. Several approaches to acid dew point assessment makes use of glassware not compatible with the high fluoride concentrations found in unfiltered gas. In this work, a new and simplistic approach to acid dew point assessment is evaluated side by side with conventional methodology. The new approach captures SO3 in the gas as sulfate onto solid NaCl trap. Interference from SO2 is avoided since it passes through the NaCl trap unreacted. The trap is then dissolved in water for direct analysis of the by ion chromatography. The importance of isokinetic sampling was evaluated, and no significant difference in results was observed. This suggests that the acid droplets are small. The method is shown to be promising for acid dew point assessment in industrial off-gas.
9:30 AM
Mathematical Modelling of the Desulfurization of Electrolysis Cell Gases in a Low Temperature Reactor: Arash Fassadi Chimeh1; Duygu Kocaefe1; Yasar Kocaefe1; Yoann Robert2; Jonathan Bernier2; 1University of Quebec at Chicoutimi; 2Rio Tinto
SO2 is one of the main sources of acid rain and air pollution. Use of powdered alkaline sorbents is an effective means of removing SO2. This semi-dry process is more economical and efficient than wet or dry desulfurization processes. The reaction between the sorbent (hydrated lime, Ca(OH)2) and SO2 is dominated by the adsorption process. In this study, a mathematical model has been developed to simulate the lab-scale desulfurization reactor employed for the low temperature gases containing low SO2 concentration coming out of the electrolysis cells used for aluminum production. A parametric study was carried out in order to examine the effects of certain parameters, such as inlet SO2 concentration and sorbent flowrate on the desulfurization efficiency. The model and some of the results will be presented in this article.
9:55 AM Break
10:10 AM
Recent Improvements to a Mathematical Model Replicating the Wave and Stream at the Bath-metal Interface: Thomas Richer1; Lukas Dion1; Laszlo Kiss1; Sébastien Guérard2; Jean-françois Bilodeau2; Guillaume Bonneau1; Martin Truchon1; 1GRIPS; 2Rio Tinto
A mathematical model has been developed to reproduce the tridimensional interface between bath and metal in an electrolysis cell. In the last year, the mathematical model has been adapted to consider alumina rafts movements in tridimensional coordinates. Among the geometrical challenges inherent to such improvement, it was necessary to properly introduce concepts such as “stream”, “interfacial forces”, and “buoyancy force”. Hence, the model uses interfacial phenomena to reproduce the movement of alumina raft at the bath-metal interface. The potential of such tracking is shown under different cell condition. In order to achieve an accurate reproduction of real cell condition, it is necessary to validate the correct behavior of the model following these recent changes. This paper detail the scope of the modifications applied to the model, the validation steps necessary to assure an appropriate level of reliability and show the raft tracking potential for industrial application.
10:35 AM
Numerical Investigation of the Thermal, Electrical and Mechanical Behaviour of Aluminum Reduction Cell during Preheating Phase: Simon Tremblay1; Daniel Marceau1; Rohini-Nandan Tripathy2; Antoine Godefroy3; Duygu Kocaefe2; Sébastien Charest3; Jules Côté3; 1University of Quebec-Chicoutimi; 2University Research Centre on Aluminium (CURAL) - Aluminium Research Centre (REGAL) - University of Québec at Chicoutimi; 3Aluminerie Alouette Inc.
Preheating of electrolysis cell using coke bed is a delicate process, which has a significant impact on the cell life. A successful preheating is considered by many factors such as: the final cathode surface temperature, the heat-up rate, the anodic current distribution and the temperature distribution (to reduce the risk of damage of the cathode/lining materials). Therefore, a better understanding of the cell behaviour is required to optimize this critical phase. In this work, electrical, thermal and displacement data have been measured on a cell during its preheating. Those measurements were then used to calibrate a ¼ cell model developed using ANSYS™, including a transient thermo-electro-mechanical weakly coupled analysis. The results obtained are in agreement with in situ measurements and allow a better understanding of the anodic current distribution, cathode surface temperature, baking level of ramming paste and stress distribution in the cathode/lining, which are critical information for further optimization.
11:00 AM
Simplified 3D MHD Model for Quick Evaluation of Aluminium Electrolysis Cell Design: Ievgen Necheporenko1; Alexander Arkhipov1; Abdalla Zarouni1; 1Emirates Global Aluminium
A mathematical model coupling 3D electrical currents distribution, magnetic field fluxes and magnetohydrodynamic behaviour of aluminium electrolysis cell is presented. COMSOL Multiphysics® is used as a software tool for the development of the present model. Implementation of electrical current carrying busbars by using line conductors and evaluation of the MHD with the help of the shallow water equations method allow for a quick and robust parameters estimation. Sensitive modelling details parameterization and automated report generation features of the model provide an easy-to-use solution for design preliminary evaluation.The modelling results obtained using the developed tool were compared with the results from the modelling software used before and validated according to the measurements. Several simulation scenarios are presented in this paper showing the capability of the developed model to estimate the influence of the aluminium design cell constituent parts on the MHD behaviour of the pot.