Page 327 - Applied Process Design For Chemical And Petrochemical Plants Volume II

31 6 Applied Process Design for Chemical and Petrochemical Plants

available, the separation performance would be over this grid to keep the saddles from nesting at the
expected to be essentially identical to the existing first layer in the opening slots. It is preferable to have
tower (for the Intalox); (3) the production rate can them resting on a surface that cannot be blanked
be increased; (4) the flooding can be removed from easily.
present operations using the %in. Intalox or any of Select a 1-in. x 1-in. (center line) x 0.063-in. wire
the other packings, but note that the a/$ of the Berl cloth with voidage of 87.8%.
saddles is not as high as the 1-in. R. R. This might Combined voidage, support grid plus cloth:
mean less efficient contact, requiring more packing.
However, from Figure 9-42 note that for a given L'/G' = (0.575) (0.878) = 50.5%
the Berl saddles are from 1530% better wetted in any This should be satisfactory, but a value much lower
given packing volume. From Figures 9-43 and 9-44 the than this could not be tolerated.
comparative effective areas, a, indicate that the Berl Dump Intalox (or Berl) saddles into tower while
saddles have about the same area/ft3 as the existing tower is filled with water.
rings. Therefore, it appears that the flooding can be
and
stopped (lower a/~~) yet the contact can be as Example 9-5: Stacked Packing Pressure Drop
good, or maybe a little better than it was originally.
4. Check support grid voidage Consider the problem of drying air with sulfuric acid,
The packing support consists of a floor grating Example 9-6. If the mass transfer relations are evaluated, a
material with bar openings spaced to give 57.5% free reasonably good estimate of the new packed height can be
void area of cross-section. determined for using 2-in. stacked ceramic Raschig rings
To avoid the possibility of local flooding at the sup- in place of Intalox saddles. For the present, assume the
port, it would be well to place a heavy hardware cloth new required stacked height is 25 ft. Although the pres-
05 IN. 0ERLSIDDLES 1

0.a I.ON Rb8Cm IW8

q-
u - - I 1

aolL--J
0.5 IN. RASCHIG RINGS

loo
RATE.
GAS
0.
FT)
LBI(HR.XSO.
l.0-
FK)
G. GAS RATE. LB.I(HR.XX!. FT)
G. GAS RATE. LB.I(HR.XSQ FT.)
600
G.
GAS
L0JHR.XW.
RATE.
A. Total holdup in 0.5 inch 8. Total holdup in 1.0 inch loo C. Total holdup in 1.5 inch D. Total holdup in 0.5 inch 00
Raschig rings. Raschig rings Raschig rings Berl saddles
0.1
t 0.1
a
5
3 ona
$
P
1
3
1.0 IN. BERL SADDLES 1.OIN.CARKJN RINGS
0.01
100 600 1,000 Figure 9-42. Total hold-up for ceramic tower packings: air-water.
G. GAS RATE. LWHRYSO. FT.) G. GAS RATE. LB./[HRXSO. FT)
E. Total holdup in 1 .O inch F. Total holdup in 1.5 inch Used by permission of Shulman, H. L., Ullrich, C. F., and Wells, H.;
Berl saddles &M rjnes A.Cb.€, Jour., V. 1, No. 2 (1 955) p. 247; all rights reserved.