Page 73 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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1 A /
. fJY
NTU Xc= f (242)
Xc jr-jr*
1 Y —Y*

At given initial and end concentration of the transferred component, the
number of theoretical stages in the column NTP in case of a linear equilibrium
equation can be calculated analytically. It is the quotient of division of the
number of transfer units NTU r to the number of transfer units of one theoretical
stage.

, NTUr_ (243 )
NTU
NTU Yc

For the packing height it can be written

H = NTP f .HETP . (244)

From Eqns. (210), (243) and (244) it follows:

¥
H = HTUyjmiy = HETP Y. , (245)

or

(246)
HETP Y = HTU Y.NTU Yc

I.e., the height equivalent to one theoretical stage HETP is equal to the
height of a mass transfer unit multiplied by the number of theoretical stages, or

(247)
HETP r=-^—NTU Yc
K G.a e

In case of a linear equilibrium according to Eq. (241), the number of
mass transfer units corresponding to one theoretical stage NTU Yc is not a