(467g) Vortex Generation With Submerged Baffles: Comparison Of Two Scales

It is often desired in solid-liquid or gas-liquid applications of a stirred tank to use an upper located impeller and modified baffles to generate a stable vortex at the air-liquid interface to drawdown, wet, and incorporate floating solids or induce and disperse gas.  The vortex for such applications must be stable, and for significant gas incorporation, must be of the minimum depth of the upper impeller submergence.  To generate a centrally located stable vortex, partial baffles of standard width (T/10) can be terminated sub-surface at the location of the impeller.  This produces rotational flow in the upper region of the vessel allowing a stable vortex to form.  This configuration was tested in two scales, a 0.61m and 2m diameter tank, using Hydrofoils, Pitched Blade Turbines, and Six-Bladed Disc Turbine in impeller to tank diameter ratios of 0.3, 0.4, and 0.5.  The geometric factors of interest were the impeller types, D/T and baffle/impeller-liquid coverage (IBC). The comparison and correlation between the two scales will be discussed along with scale up strategies and process implications.