Validation of the Gravimetric Method to Properly Follow Alumina Dissolution in Cryolitic Bath

Alumina dissolution is now one of the greatest concerns about Hall-Héroult process optimization. To tackle alumina dissolution kinetics, a gravimetric method was developed. This method follows the apparent weight of an alumina sample while immersed in a cryolitic bath. Then, from the weight over time curve, it is possible to identify the forces acting on the sample especially the change of gravity and buoyancy forces. The experimental results obtained by this method were compared to four other values: namely the data found in the literature, values computed with a CFD model, the total mass loss of alumina disc samples over time and finally to a sample boundary displacement method. The boundary displacement and the CFD model have also demonstrated the strong dependence of the dissolution rate on the convection pattern around the sample.