(163e) Toward 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. The first thing noted was the insensitivity to physical properties. It is shown that the minimum suspension speed is not a correlating or normalizing variable. It was also shown that the relation between cloud height and speed was independent of whether the speed was above or below the minimum suspension speed. The appropriate normalizing value for cloud height was the tank diameter not the liquid level. Detailed studies were made of the effect of viscosity and concentration to confirm the weak functionalities. At lower concentrations there is no effect of concentration on cloud height.

The mechanism seems to be one of turbulent dispersion in the upper part of the vessel.