Two-phase electrolysis process: From the bubble to the electrochemical cell properties

During two-phase electrolysis for aluminium, fluorine or hydrogen production there are bubbles which are created at the electrode which imply a great hydrodynamic acceleration but also a quite important electrical field and electrochemical processes disturbance. This disturbance can lead to the modification of the local current density and to anode effects for example. There are also few local experimental measurements in term of chemical composition, temperature or current density because considered media are often very aggressive (high temperature, very strong reactivity). Then, the modelling and numerical simulation appears to be one important tool to understand and optimize associated processes, though the rigorous validation of numerical calculations is difficult. The goal of the present work is the modelling and the numerical simulation of the local gas production at an industrial scale vertical electrode. Because bubbles modify species, heat and electricity transport and are motion sources, there is a strong coupling between all these phenomena and between the bubble scale and the macroscopic one. Because bubbles are at the origin of all macroscopic disturbances. it appears necessary to investigate phenomenological laws at the bubble scale. The finite volume of the Fluidyn (R) and Fluent (R) software has been used. (C) 2007 Elsevier B.V. All rights reserved.