(161a) The Development of a Correlation for Solid-Liquid Cloud Height in Mechanical Agitated Vessels

Agitated vessels containing mixture of solids and liquids can be characterized by a minimum suspension speed and a vertical solids distribution. In many cases the cloud height which is the visual demarcation between slurry and clear interface is a useful parameter for characterizing vertical distribution. The emphasis in these studies has been on the effect of physical properties: concentration, density and viscosity and the effect of scale up. Geometry has been fixed throughout.

This correlation is of a dimensionless cloud height which is normalized using the tank diameter. This work presents additional data at high particle densities and weight fractions. Based on this work it was found that the dimensionless cloud height as a function of solids weight fraction has two regimes. As the weight fraction is increased at a constant stirrer speed the cloud height initially shows a slight increase reaching a local maximum and then exhibits a drop in height. Based on this observation the cloud height correlation has been modified to predict this behavior.

The variables with the largest effect on cloud height are the equipment variables of impeller speed and diameter. The physical properties with the largest effect on cloud height are density and particle diameter.