Page 48 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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C —C* k
L ° L «=^ s (134)
r p k

fc (135 )
C L~C Gi/m
c
Equation (134) gives the possibility to calculate the concentration at the
interface.
In a similar way from Eq. (130) and (131) the following expression can
be obtained;

N A=K L(C Lt-C L), (136)

K L= j ! l , (137)
_ JL _ _
k
m ck G

where C L is the concentration of the liquid bulk in equilibrium with the
concentration of the gas phase.
It is easy to see that:

(138)

In all cases when m c is a function of the concentration which is different
in the bulk of the fluid and at the interface, its value in the equations has to be
calculated as average.
From equation (133) it can be seen that in case of very soluble gases for
which m c tends to 0, KQ is practically equal to ko, that means the mass transfer
resistance of the liquid phase is to be neglected and the process is gas side
controlled. By analogy, from Eq. (137) it follows that for poorly soluble gases,
for which m c tends to infinity Ki is practically equal to fe. In that case the
process is liquid side controlled.
From Eqs.(6) and (8) it follows: