Gas flow maldistribution in random packed beds of non-spherical particles – A CFD study

Abstract

In this work, gas maldistribution in random packings of cylinders and Raschig rings is studied with particle-resolved direct numerical simulation (PRDNS) employing a finite volume solver for Cartesian grids and the immersed boundary method for the treatment of complex geometries. The geometry of the random packed bed has been obtained in a separate simulation based on a sequential deposition of particles in a cylindrical column and a simplified mechanics with additional radial force allowing for higher packing densities. The first part of the work focuses on comparison of the packings of cylinders and rings with respect to their ability to distribute the flow uniformly over the cross-section of the column when the gas in the form of a narrow jet enters along the column axis and impinges on the bed directly. The second part is devoted to analysis of three different inlet configurations and their influence on gas maldistribution in the packing of Raschig rings. It has been found that the random packing of rings has comparable properties of flow uniformisation to the same arrangement of full cylinders with significantly lower pressure drop and much less pronounced effect of formation of localised jets at the bed outlet. Among the considered inlet configurations the most beneficial is the one in which the gas duct is tangential to the walls of the distribution chamber.