On the suspension of large and dense solid particles in turbulent stirred vessels

Abstract

This work with the focus on large and dense particles aims to investigate the range of physical properties over which the 2015 Grenville, Mak, Brown correlation (referred to here as GMB) is valid for suspension of solid particles in liquid filled stirred tanks. The test particles were greater than 1000 μm in diameter (up to 10,000 μm) while the density difference ratio (ρs − ρl)/ρl between solid and liquid phase is beyond two (up to over 10). Two flat based vessels, 305 and 610 mm in diameter, were utilized, while the impellers used were a wide blade hydrofoil and a pitched blade turbine impeller with multiple diameters being tested in each scale. With the particle density and diameter represented by the Archimedes number, Ar, the results exhibit a subtle anomaly or slope change at Ar values around 104 which may be indicative of a change in the mechanism of suspending related to the ratio of particle response time to turbulence time scale. With respect to using the GMB correlation for industrial-scale agitator design, the use of exponent 0.5 on Ar looks justified. The test conditions within this study increase the range over which the GMB correlation is applicable by four orders of magnitude.