Longitudinal Dispersion in Packed Gas-Absorption Columns

Abstract

A Zft -L d, packed gas -absorption.column was constructed for the purpose of obtaining longitudinal mixing data on both the liquid and gas phases under nonabsorbing operating conditions.The equipment is described in detail and the operating procedure is given..The calculation of the liquid-phase Peclet number of an.early run is reported.-2-Kramers and Alberda, Carberry and Brtton, Jacques and Vermeulen, and Ebach and White 6 have determined values of the Peclet number for water flowing through beds of various packings over a wide range of Reynolds numbers, McHenry and Wilhelm, 7 and Robinson, 8 were among those who determined Peclet numbers for gas streams flowing through packed beds.These data indicate that the Peclet number in single-phase flow (a) is a function of Reynolds number, (b) has different values in laminar and turbulent flow, and (c) passes through a transition region with respect to Reynolds number, corresponding to the change from laminary to turbulent flow in the bed.Until recently there has been comparatively little work done on longitudinal dispersion intwo-phase systems.In the paper referred.toabove, Jacques and Vermeulen used a water-kerosene system to determine Peclet numbers in both phases in a packed extraction column.They found the Peclet numbers in two-phase flow to be equal to or less than the corresponding single-phase values in laminar flow.The twophase Peclet numbers obtained can be correlated in terms of the flow rates in the two phases.In a later report Jacques et al, present additional data that agree with.theirprevious results for two-phase Systems. 10 De Maria and White studied mixing in an air stream flowing through beds of various sizes of raschig rings irrigated by water.They found that the axial Peclet number of the gas flowing through wet packing was always less than that for dry packing.11 Recently Stemerding reported data on axial diffusion coefficients of the continuous water phase determined in an air-water system passing through a column packed with 13-mm raschig rings.He found the axial diffusion coefficient rather insensitive to liquid flow rate, and that it passed through a maximum value when plotted against increasing gas flow rate.The coefficients determined were in the range of 8 to 15 cm: /se.