A
water/air model was developed to simulate the refining of molten aluminium by
the sparging of gas through an impeller. The optimal gas dispersion depends upon
selecting the correct gas rate for a given impeller rotational velocity to
prevent flooding or channelling. Correlations illustrating this flooding
behaviour exist for standard impellers within standard tank geometries. However
the validity of these correlations has not been substantiated for gas dispersion
in high temperature molten metals with non-standard tank and impeller
dimensions.
Metal
refining is most efficient when fine bubbles are generated and uniformly
distributed within the treatment tank. The application of some measuring
technique able to detect this distribution within a non transparent operating
treatment tank would be invaluable, enabling the optimisation of gas flow and
impeller speed.

A technique has been developed to measure the pressure
fluctuation levels at specific points in the water model. Comparison of these
pressure fluctuation data with photographic evidence obtained in the water model
suggests that the flow regime in the metal treatment unit may be determined
using this technique.