Fundamental Understandings of the Causes and Consequences of Chemical, Electrical and Thermal Heterogeneities in Aluminium Electrolysis Cells

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The primary aluminium production industry is continuously trying to increase their production rate, with a reduction of their cost along with lower specific energy consumption. However, the stability of the process is becoming more and more sensitive to local variations within an electrolysis cell. These variations may be chemical (alumina distribution), thermal (energy level) or electrical (current distribution). Such imbalance lead to variations of the normal process conditions leading to negative consequences for the cell such as lower production rate, increase of energy consumption, sludge formation, or excessive production of greenhouse gases. The research program described in this proposal aims at enhancing and developing new modules for a numerical tool that would allow simulations of the heterogenous conditions in a cell and their potential consequences. The initial work on that mathematical model was performed by the applicant in previous research. The model allows the simulation of chemical and electrical variations in the cell, without any considerations for the thermal mechanisms. With this information's, the mathematical model has the ability to predict the onset of perfluorocarbon emissions during the electrolysis process. A good usage of this tool, with further refinements can provide solutions for multiple issues of the industry. There are numerous factors that play a major role in the cell heterogeneity that are not considered yet in the mathematical model. The research plan is developed with the vision to progressively introduce these elements in the model and reach more accurate prediction and pinpoint more detailed solutions to address the real conditions of industrial cells. The initial phase of the program (described in detail in this proposal) will target the thermal exchange occurring in the cell and couple the energy balance with the existing chemical and electrical modules. Further improvement, beyond the scope of this proposal will subsequently investigate the chemical, thermal and, electrical impact of operational events on the heterogeneity of the cell. A third phase will consider the impact of additives and more advanced themes such as anodic incidents and exchange mechanisms between the alumina metal pad and the electrolysis bath. The research program plan considered for the next five years includes the formation of a PhD student to integrate an energy balance into the mathematical model with indicators that can allow the evaluation of the level of severity of the imbalance observed. A master student is also considered to investigate the thermal consequences of low- and high-voltage anode effects. In both cases, the work performed will be based on theoretical concepts and experimental validation in a laboratory setup. Finally, a postdoctoral fellow will perform an extensive parametric study to pinpoint the main cause of the imbalance and propose potential and realistic solution for Canadian aluminium producers.