Gas and Alumina Distribution and Transport

In 2013 and 2014 the main modelling approaches were built-up, so the main focus of the BIA GADT project (219732/O30) in 2015 was to improve the performance and enable a smooth coupling between the different approaches. Following actions have being executed: ?IFE improved in 2015 the performance for the metal pad simulation approach. Integration of changing bath properties due to chemical reactions as well as bubble frat have been added, showing the strong impact of the bubble draft. ?The single anode bubble flow model at SINTEF was used in 2015 for investigating different anode design and derive integrated bubble draft and turbulent viscosity for the full cell bath flow model. The result data have been delivered to CSIRO to verify the bubble draft and turbulent viscosity. ?Additionally SINTEF has completed the measurement of anode wetting conditions at high temperature with industrial cryolite bath. ?The ICEM meshing approach for the full cell bath flow and alumina distribution model was improved by enhancements carried out from ANSYS Germany for better performance. ?CSIRO incorporated the integrated bubble draft and turbulent viscosity from the bubble flow model (SINTEF) into the bath flow model. The enhanced model was used to support set-up of plant measurements at Rheinwerk smelter in Germany. ?A PhD student was selected to carry out measurements on CO/CO2 diffusion in carbon and cryolite for understanding the bubble nucleation process. In 2015 the focus was on the CO/CO2 diffusion in carbon under consideration of carbon porosity, microstructure and Boudouard reaction. ?A summer student from NTNU worked during summer 2015 at Årdal metal plant to investigate several type of measurement that are being used to evaluate for instance bath properties, cell temperatures and side ledge profiles.

The GADT project is aiming at developing a calibrated mathematical model for the characterisation of bubble formation and alumina and gas bubble transport mechanism at the anode surface in an aluminum reduction cell. The project will be based on results f rom in-house Hydro projects as well as on results from the Research Council supported BIA-PI HCD and RENERGI-HAL UP projects. The project will be executed in close co-operation with the Norwegian R&D institutions SINTEF and IFE, as well as with the Austra lian R&D institute CSIRO. By being able to understand, describe and thereby control the gas and alumina behaviour at the anode surface it is expected that the distance between the anode and cathode can be reduced, reducing the ohmic drop with 100 mv and thereby save energy. The consquential energy reduction will be approx. 0,3 kWh/kg Al, equivalent to an energy consumption reduction of 360 GWh / year for the Norwegian smelters.