On the influence of particle shape and process conditions in the pressure drop and hydrodynamics in a wall-effect fixed bed

摘要

A low tube-to-particle diameter ratio (d(t)/d(e,p)) fixed bed, packed with spherical and nonspherical catalyst supports, was used to investigate pressure drop at varying temperature (298-673K) and inlet pressure (245-294kPa). The d(t)/d(e,p) ranged from 3 to 6, namely, a large wall-effect fixed bed, with an average void fraction between 0.38 and 0.61. These conditions pertain to multitubular fixed-bed reactors used for exothermic reactions. The pressure drop was notably influenced by the particle size and morphology as well as temperature. The use of particles with d(t)/d(e,p)5 and relatively large bed void fractions (0.55) appeared suitable for pressure drop control. The fluid velocity profiles were calculated by applying the Navier-Stokes-Darcy-Forchheimer equation computing the respective permeability parameters with refitted state-of-the-art pressure drop correlations. The fluid flow exhibited different velocity zones across the fixed bed, the highest velocity zone being located near the reactor wall. The axial velocity component was influenced by the catalyst morphology, as well as temperature and inlet pressure.