Mixing Time of Refining Vessels Stirred by Gas Injection
1983 Volume 23 Issue 1 Pages 43-50
Details
1983 Volume 23 Issue 1 Pages 43-50
Correlation between mixing time (τ) and mixing 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 depend 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(l) is essential.
Comparing gas agitation with mechanical agitation, the correlation between fluid velocity and e are expressed by the identical formula. A formulation evaluating mixing power density is derived through a thought experiment.
Furthermore, the procedure for scale-up is presented on a basis of data obtained by the water model experiments.
