Page 154 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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Chapter 3

Industrial packings

The most important part of a column is its packing. In this chapter the
industrial packings for column apparatuses are considered. Some experimental
data for their performance characteristics are presented and equations for
calculating these values are given. A comparison between some important
packings is also presented. The chapter is written based on the data published in
the literature including the prospectuses of some producers of highly effective
packings. The investigations of Billet and his team [94,170-174,177, 223, 231-
238] and these of the author's team are largely used.

3.1. Requirements of the mass transfer theory to the packing form
From economical point of view the good packing must insure low
capital investments and low operating costs. The capital investments are
connected with the intensity of the mass transfer processes in the packing, the
operating costs - first of all with its pressure drop. As a measure of the mass
transfer intensity, the quantity of substance transferred in a unit of packing
volume per unit of time can be used. The possibility to increase this quantity is
easy to be seen from the basic equation of mass transfer in packed bed columns,
Eq. (136), in Chapter 1, written again below.

G = K Ga eV pA G=K la eV pA l, (1)

where G is the quantity of the transferred substance per unit of time, Kcsnd K L -
the overall mass transfer coefficients for gas- and liquid-side controlled mass
transfer, a e- the effective packing surface area, V p- the packing volume, AQ and

A L- the driving forces of the mass transfer process calculated by the
concentration of the gas, respectively of the liquid phase.
From the equation follows that to increase the value of G for a unit of
packed volume Vp, at least one of the values Kg (or K L), a e, and A G (or A L) must
be increased.