Page 74 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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function of the concentration and for every concrete case is a constant
depending on the slope of the equilibrium straight line and the slope of the
working straight line.
In Fig. 11 taken from Stringle and Rukovena [43], a principle diagram
of HETP as a function of the vapour capacity factor C$ (called also entrainment
parameter) is presented. This factor is introduced instead of the gas velocity to
account for the effect of vapour and liquid density.

c =- 0.S (248)
s

ft

I
a.
FLOOD POINT
§
93
IS
CD
Q A B
G MEC POINT, Cscl
i
§ SYSTEM BASE HETP
3

EFFICIENT CAPACITY
Vapour Rate, Cs

Fig. 11, Height equivalent to a theoretical plate [43, page 145]).

The figure is given for constant reflux ratio, i.e. in case when the liquid
rate increases in direct proportion to the vapour velocity. The region from point
B to the loading point C exhibits constant separation efficiency typical for the
packings. As C s increases further, the vapour rate becomes great enough to
begin to interact with the liquid phase. This interaction increases the interfacial
area beyond point C which leads to increasing of the packing efficiency too.
The increasing continues to the point E where HETP has a minimum. The