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31 8 Applied Process Design for Chemical and Petrochemical Plants

some packings with physical data Tables 9-1 through 9-14 Area Table 9-34
of sphere = x (diameter)2. Static Hold-up in Random Packing

For liquids other than water [36,40]: PackingNominal Static Water Hold-up, 4,
0.78 (:) Size, In. Ft3/F$ Packing
hl=h, (pL)'.'(?) (9 - 55) Raschig rings (unglazed porcelain)
?4 0.0325
1 0.0150
where hl = liquid hold-up, ft3/ft3 packed tower volume 1% 0.0089
PL = liquid viscosity, centipoise 2 0.0038
p~ = liquid density, lb/ft3 Berl saddles (unglazed porcelain)
o = surface tension, dynes/cm
?4 0.0317
1 0.0110
Values of exponent n are given in Figure 945. 1% 0.0052
Total liquid hold-up in packed bed, ht = static hold-up, Raschig rings (carbon)
h,, plus operating hold-up, ho [64, 661. 1 0.0358
The static hold-up is independent of liquid and gas 1% 0.0200
rates, since it represents the liquid held in the packing 2 0.0150
after a period of drainage time, usually until constant By permission of The American Institute of Chemical Engineers, Shul-
weight of material is received. This requires approximate man, H. L. et al., Cha. Engx Jour: Vol. 1, No. 2,247 (1955) and ibid, p.
ly 1 hour for a 10-in. dia. x 36-in. packed height tower. 259 (1935), Ref. 64 and 66, all rights reserved.
Table 9-34 adequately summarizes the data.
Total hold-up, ht, of water is represented for Raschig
rings and Berl saddles [66]. Table 9-35
Total HOld-Up Constants
ht = a L'f3/Dp2 (9 - 56)
Packing
P = YDpe ~ ~
Porcelain Raschig ring 2.25 x 0.965 0.376
Constants are given in Table 9-35. Carbon Raschig ring 7.90 x 0.706 0.376
Figures 942 A, B, C, D, E, F present the graphical inter- Porcelain Berl saddles 2.50 x 0.965 0.376
pretation of the total hold-up equation. These are more Porcelain, In. Equivalent Spherical Dia., Ft

?4 R. R. 0.0582
1 R. R. 0.1167
1% R. R. 0.1740
2 R. R. 0.238
!4 Berl saddle 0.0532
1 Berl saddle 0.1050
1% Berl saddle 0.153
Carbon, In.
1 R R. 0.1167
1MR. R 0.178
2RR 0.235
By permission of The American Institute of Chemical Engineers, Shul-
man, H. L. et al., Chem. En@ Jour Vol. 1, No. 2,247 (1955) and ibid, p.
259 (1955), Ref. 64 and 66, all rights reserved.

convenient to apply where the system fits (or nearly fits)
Liquid Rate, Ids./(Hr.) (sq.ft.1
' the curves.
These data are valuable for determining the total weight
Figure 9-45. Liquid hold-up variation of surface tension exponent of liquid held in the packing, and also the void fraction, in
with liquid rate. Reproduced by permission of the American Institute
of Chemical Engineers; Jesser, B. W., and Elgin, J. C. 7ians. A.6Ch.E. an operating column. E is the void fraction of the dry pack-
.-
V. 39, No. 3 (1 943) p. 295; all rights resewed. ing minus the total hold-up, h,.