Bridging the gap between solids suspension theory and equipment design

The aim of this research was to investigate the effect of equipment design on suspending solid particles in stirred vessels. We investigated and evaluated several improvements to the Grenville-Mak-Brown correlation for the just-suspended impeller speed with the goal of generalizing it. We present two new geometry-specific as well as generalized suspension correlations based on experiments made with 225 µm sand in water in four vessel geometries: cylindrical flat-based, cylindrical torispherical dish-based, square flat-based, and horizontally oriented cylindrical vessels. We also present novel experimental data for both a wide blade hydrofoil and a pitched blade turbine. We define a vessel sphericity parameter to generalize the various tanks into a single correlation permitting interpolation to other vessel types and sizes not tested. We further show how controlled particle settling can be used to transform a flat-based stirred vessel into an equivalent torispherical dish-based vessel to save energy.