Page 325 - Applied Process Design For Chemical And Petrochemical Plants Volume II

314 Applied Process Design for Chemical and Petrochemical Plants

Gas Rate,ft./sec. 4. This bed should be in three sections (two might be
I .o IO acceptable under some circumstances, or if different
packing were used) thereby requiring two intermedi-
ate combined packing supports and redistribution
plates and one bottom support plate.
Estimate pressure drop per redistribution set-up or
support

= 1.0 in.
For two redistributors plus one support plate:
Total estimated pressure drop = (3) (1.0)
= 3 in. water

5. Total estimated pressure drop through packed por-
tion of tower:
Bed AP = 27.0
Internals =LO
30.0 in. water

Say, 30 to 35 in. water (this should be 30.0 d5-20%)
6. Estimated percent of flooding
Reading the abscissa of Figure 9-21C at value 0.0756
for ordinate at flooding line for dumped packing:
Gas Rate, lb./(Hr.)(sq.ft.) = 0.13
Plate: 7/32" 0 Holes
1/8" Tk. 43.2% Free Area Then, actual value of 0.0563 is:
0 0563
(100)
Figure 9-41. Flooding on perforated support plate. Used by permis- Percent of liquid flooding = - 43.3%
=
sion of Lerner, B. J. and Grove, C. S., Jr., Ind. Eng. Chem., V. 43, No. 0.13
1 (1 951), p. 21 6; all rights resewed.
Note that this rather low value will usually occur
when operating at the low L/G values due to the
greater operating spread between flooding and load-
(E)
( 29 ) (z) 1.732 lb/ft3 ing (see Figure 9-21C).
=
PG= 379 570 14.7
7. Estimated percent of loading (average)
PL = (62.3) (1.22) = 76.1 lb/ft3 Reading abscissa at 0.0756 for ordinate of line B gives
ordinate = 0.078
p = 2 cp at 104°F for liquid 72.1%
O
0563
(100)
=
a
F--= 137 Table 9 - 26A note range. Percent of flooding = - (not very precise)
0.078
E3 This is an acceptable value and should not be
2250 (
L 1.732 )'Ip exceeded except in known systems. It is preferable to
- bG /(PL - PG )I1/* =- = 0.07563 operate reasonably close to the loading condition for
G 4540 76.1 - 1.732
best efficiency of contact.
- (4540/3600)' (1.07)O" (137) As an alternate consideration, assume various pres
c2(A) p0.1 - sure drops/foot of packing (same) and determine
PG E3 (PL - PG) g, 1.732 (76.1 - 1.732) (32.2)
effect on calculated column diameter. Use the same
= 0.0563 input information as original stated conditions, then:
2. Locating 0.0756 and 0.0563 on Figure 9-21C reading
the intersection indicates a condition in the lower Assumed Pressure Drop, Calculated
loading region, and a pressure drop of approximately in. H?O/ft Column Diameter, ft
0.60 in. water/ft of packing. 0.25 5.22
3. Expected pressure drop through bed: 0.50 4.61
= (45 ft) (0.60) = 27 in. water, total 0.75 4.35