Page 354 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Packed Towers 343

Hufton et al. [120] tested gauze type packing for large
E commercial units, which resulted in a scale-up procedure
9 that is too involved to reproduce here.
E
1
- 1. Estimate required packing height from Bravo, et al.
0
C
Y [ 1131 or manufacturer's information.
a
P
n 2. Calculate commercial scale HETP from Fair, et al.
92 [ 1081 and/or Hufton, et al. [ 1201.
2
v)
p!
n _. Mass and Heat Transfer in Packed Towers
0.0 0.50 1.00 1.50 2.00 2.50 3.00
Fs, (Wsec) Most packed towers axe used for mass transfer opera-
tions such as absorption, distillation, and stripping; how-
Figure 9-66. Representative pressure drop for Montz high-efficiency ever, there are other uses such as heat transfer quenching
structured packings (several designshtyles) for a sheet metal pack- and entrainment knockout.
ing. Performance can be accurately calculated by the manufacturer
(See Figures 9-6LL and 9-6MM). Used by permission of Nutter Engi- The usual packings and auxiliary features associated
neering Co., Harsco Corp., Bull. B-1 . Specifications and descriptions with these towers have been presented in connection with
used were in effect when this publication was approved for printing. pressure drop considerations.
Nutter Engineering reserves the right to discontinue models or Because the packed tower is a continuous contacting
options at any time, or change specifications, equipment or designs device as compared to the step-wise plate tower, perfor-
without notice and without incurring obligation. Using any of this
information for specific applications should be done in consultation mance capacity is expressed as the number of transfer
with Nutter Engineering personnel. units, N, the height of the transfer unit, H.T.C., and mass
transfer coefficients &a and ka. Figure 9-68 identifies
the key symbols and constant flow material balance.

Number of Transfer Units, NOG, NOL

The transfer of mass between phases in a packed tower
occurs either as essentially all gas film controlling, all liq-
uid film controlling, or some combination of these mech-
anisms (see Figure 9-69). To express the ease (low number
Ruhr Univ. Data*-Bochum, Germany
Chlorobenzene / Ethylbenzene System
25.0 - mmHg, W = 1
50

20.0
8
6 15.0
- Material Balance : Gm(y-yz) L(x-xz)
C
Y (Constant Gm and L)
0- 10.0
kl Operating Line : Gm(YI-Y)=Lm(XI-X)
I T
5.0
Packed
0.0
..
0.0 0.50 1.00 1.50 2.00 2.50 3.00 Height,
]
Dr. R. Bi//et 'I2
Fs = [T [Pv]
Y = y/(l-y)
Figure 9-67. Representative HETP for Monk high-efficiency struc-
tured packings (several designsktyles) for a sheet metal packing. x = x/(l-x)
Used by permission of Nutter Engineering Co., Harsco Corp., Bull. B- y = Y/(ItY)
1. Specifications and descriptions used were in effect when this pub- x = X/(ltX)
lication was approved for printing. Nutter Engineering reserves the
right to discontinue models or options at any time, or change speci-
fications, equipment or designs without notice and without incurring
obligation. Using any of this information for speck applications
should be done in consultation with Nutter Engineering personnel. Figure 9-68. Counter-cumnt packed tower symbols.