Mass transfer in packed beds

Abstract

Although considerable work has been done on the problem of heat transfer radially in fixed beds through which gases are flowing, the data available for mass transfer are limited to one pipe size and one packing size and refer to average diffusivities for the entire bed. The present study was undertaken to determine: (1) diifusivities over a range of pipe and packing sizes and (2) the effect of radial position in the bed. Empirical correlations are then presented for both point Peclet numbers, which vary wit11 radial position, and average Pedet numbers for the entire bed.The variations in Peclet number with radius can be explained in terms of the corresponding variation in void fraction for 81% of the radius of the bed. A t modified Reynolds numbers above 40 to 100 the equation Pe = 8.0 + 100 ( 6 -6,) correlates the effects of pipe and packing size and radial position. At radial positions greater than 0.81 wall friction influences turbulence conditions and the Peclet number.

Preliminary Ion Exchange Modeling for Removal of Technetium from Hanford Waste Using SuperLig 639 Resin

“…Also shown in Dorweiler and Fahien (1959) performed similar experiments that agreed with Schwartz and Smith (1953) and went to flowrates as low as 30 cm/min. In a later study by Fahien and Smith (1955) significant radial effects were observed for column-to-particle diameters less than 20.…”

Diffusion Behaviors of He and CH4 in Air Flow through Packed Bed

“…10,11) The basic differential equation for mass transfer, which considers diffusion in the radial direction only and bulk flow in the axial direction, is written as Eq. (1) 6.…”

Mass Transfer in Low Velocity Gas Streams

“…Fahien (6) were found to increas~ with the particle diameter to duct ~iameter ratio and to be substantially independent of mass velocity for mass velocities above 500 lbs/hr/sq ft. Air from a high pressure. source was used as the bulk stream gas.…”

“…Under the rigid assumptions .that the mass transfer proces~ is, a function of, local flow conditions, Fahien · (6) .solved equatiqns 2 and 3 allowing both the total diffusivity, ~' arid the velocity, uz (or u), to vary with radial position. The solution is in terms of finite difference equations and may .…”