Characteristics of fixed beds packed with anisotropic particles—Use of image analysis

Abstract

Fixed beds of anisotropic particles are commonly involved in chemical engineering processes: beds of cylindrical catalyst pellets or beds of wood shavings in paper industry. The characterization of the spatial variations of their structural properties is of great importance for flow modelling purposes. In this work, we intend to produce new data concerning a bed of long cylinder ( h/d=5.29) and a bed of flat plates ( e/a=0.209). This study focuses on the characterization of top and bottom effects, as well as wall effects. The experimental procedure is based on the study of sections of packed beds consolidated with a resin. The captured images of successive transverse and longitudinal sections of the beds are treated and analysed, thanks to an image analysis software. The local variation of the voidage is determined in both the transverse and the longitudinal directions of the beds. Furthermore, mean intercept lengths and mean numbers of particles are measured and discussed. Concerning flat plates, an anisotropic ratio calculated from intercept measurements is compared to that previously obtained from pressure drop measurements. The main results of this work concern the enlightening of wall effects and end effects importance for the two studied beds compared to beds of spheres studied in the literature.