Page 350 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Packed Towers 339

Hatfield [114] describes the improvements in commer-
cial performance when Pall rings were replaced with
Goodoe@ packing.
1.0
Pressure drop through gauze and sheet metal struc-
? tured packings [115] applies for the region below the
8
. loading point and cannot predict the flood point because
s
0
l5
$ liquid holdup vs. gas velocity is not included. The latest
version of the equation is in Reference 108:
1.0
d 1
0.5
0
0.1 a1 0.3 ad 0.5 ab Re, = s u, Pg (9 - 73)
CAPACITY, C = Vs h
Figure 9-MA. Pressure drop comparison of Glitsch GridTM and Bal- U, = Ug/& sin 8 (9 - 76)
last@ rings at 10 gpm/ft2. Used by permission of Glitsch, Inc. Bull.
9-72. Frl= U12/(Sg) (9 77)
-
where C, = constant, value of 3.08 in Equation 9-74 recom-
mended for all structured packings similar to such
types as Flexipac 2@ and Gempak 2@. Note: Refer-
OS ence 108 provides values for other structured pack-
ing sizes and styles and wire gauze. Refer to manu-
facturer for confirmation.
0.5
where c, C&, C1, C2, C3 = correlation constants
Frl = liquid Froude number
g - gravitational constant
Reg - Reynolds number for gas
S - length of corrugation side
Up. = effective velocity of gas
Ug = superficial velocity of gas
0.2
U1 - superficial velocity of liquid
I I I I I I I I Ap - pressure drop per unit packed height
E = packing void fraction
8 = angle of flow channel (from
horizontal)
10 10 ao 40 50 60 70 p - viscosity
p = density
LIQUID RAT& O M . FT.
f (subscript) - flooding conditions
Figure 9-61 B. Capacity performance comparison for Glitsch-GridTM g (subscript) - gas
and Ballast@ rings. Used by permission of Glitsch, Inc. Bull. 9-72.
1 (subscript) - liquid
Billet [123] reports that metal gauze-type packing (such
as Gaodloe@) give better performance and lower costs for
1. Flooding: Empirical plots of data, as shown in Figures high vacuum distillations, particularly for thermally unsta-
9-62,9-63A, 9-63B, and 9-64. ble mixtures. This comparison was made against Pall rings.
2. Pressure drop: Generalized model of Bravo, et al. For the performance information referenced here, see
[ 11 11, in combination with Stichlman [ 1121. Pressure Figure 9-65 [ 1231.
drop at the flood point as a function of the flow para- For general references during vacuum operations:
meter at the flood point is given in Figure 9-62 [lo81
for several packings using the Stichlman model equa- 1. Due to the rapid decrease in specific efficiency with
tions for various system pressures [ 1081. increasing load, the optimum load factor is equal to a
3. Mass transfer: Generalized model of Bravo, et al.
[113], with discount factors for wetted surfaces. (tat catinued m page 342)