| The Hall-Heroult process, allowing the aluminium production by electrolysis, is very energy-consuming and polluting. The production efficiency of this process is called current efficiency and it is defined as the ratio between the real metal production and the theoretical metal production, obtained by Faraday's law. The Process Performance Technologies Company has developed a project in order to increase the current efficiency of the Hall-Heroult process. This project is divided in two distinct parts; one is the development of a control system and the other is the development of a statistical analysis system including a mathematical model of prediction of current efficiency.;The research work of this master's thesis, in collaboration with the company PPT, focuses on the mathematical model of prediction of current efficiency. The main objective was to validate and improve the model used by PPT. To achieve this goal, a broad literature search was conducted to compare the equation in the model of PPT to those found in the literature. On the other hand, a bank of empirical relations, presented in the literature, concerning the properties of the electrolyte was provided to the company. This bank will allow the user system to select the most appropriate equation for the kind of bath used.;A detailed study on one of the important parameters of the model, the ledge thickness, was also performed. The analysis of several thermal resistance models has led to the better understanding of the influence of bath-ledge heat transfer coefficient on the thickness of ledge. In addition, a series of numerical modelings, carried out with a commercial finite element program, have been conducted to study the behaviour of the ledge and also in order to obtain a generalized equation linking the heat loss and the ledge thickness. |
