(155d) New Correlation for Predicting Cloud Height in a Stirred Tank

The goal of the study was to obtain a cloud height correlation that included the effects of particle size, particle density, particle concentration, fluid density and viscosity, impeller speed, impeller size and tank diameter.  The laboratory scale study was conducted using a Plexiglas, flat bottom tank 28.3 cm diameter tank with a A310® impeller with 8.5 centimeter diameter.  The large scale studies were conducted at Philadelphia Mixing Solutions using a 0.61 m diameter tank and and impeller size of 0.2 m.  The particles that were suspended included urea formaldehyde, polyoxymethylene (acetal), melamine, sand, and aluminum with specific gravity values of 1.2, 1.4, 1.57, 2.6, and 2.7 respectively.  The particle sizes ranged from 0.15 to 9.4 mm. The cloud height was measured at different impeller speeds (measured in RPM) ranging from nearly just suspended speed (NJS) to 2355 RPM, the maximum speed of the equipment. The particle concentrations used within the tank were 1%, 2.5%, and 5% by weight.  The viscosity and density of the fluid was varied by using water and solutions of sugar and water.

It was determined that cloud height is dependent primarily on speed and  tank size with a lesser dependence on density difference, particle size and viscosity.  Concentration has a negligible effect on cloud height.