Mixing Time in Refining Vessel Being Agitated by Gas

Abstract

Correlation between mixing time (τ) and applied power density (ε) for gas agitation is theoretically developed from the view point of transport phenomena and the theoretical results were confirmed by the water model experiments. Fluid motion in the vessel agitated by gas injection can be classified into two major flows. One is a flow predominated by viscous force, in which τ is in proportion to ε^-0.5 and τ does not depends on the vessel size. The other is a flow predominated by inertia force or turbulent viscous force, in which τ is in proportion to ε^-1/3 and τ is dependent on vessel size. In the latter flow, the evaluation of the mixing length (1) is essential.
Comparing gas agitation with mechanical agitation, the correlations between fluid velocity and applied power density are expressed by the identical formula.
Furthermore, the procedure for scale-up is presented on the basis of data obtained by the water model experiments.