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330 Chapter 6

will be larger than calculated above. The number of equilibrium stages is now
3.727.

4
1.919xl0 (18) ( 0.07395 V' 5
———————— ———— | =4.181
98.39(84.94) I 62.00 )

From Equation 6.23.6, the tray spacing is 1.5 ft (0.467 m), and from Equa-
tion 6.23.4, k, equals 0.018 m/s (0.05906 ft/s). Because there is no information on
foaming for this system, select the lower value of k v for a foaming liquid. This
choice results in a larger column diameter than for a nonfoaming liquid. From
Equation 6.23.5,

0 2
k v = 0.75 (0.018) (69/20) ' = 0.01729 m/s (0.05673 ft/s)
Thus, from Equation 6.23.3, the maximum air velocity,

5
v v = 0.01729 [ (62.0 - 0.07395) / 0.07395 ] °' = 0.5003 m/s (1.641 ft/s)
v s= 0.9(1.641)= 1.477ft/s (0.4502m)

From Equation 6.23.1, the revised cross-sectional area for the column,
4.023xl0 4 1
2
2
A = ————— ——— = 7.566 ft (0.7029 m )
3600 1.477

From Equation 6.23.2, the revised column diameter,

( 4 (7.566) V- 5
D= ————— =3.321ft (0.9484m)
I n )

Allowing for a safety factor of 15%, obtained from Table 6.30, the column
diameter is 3.579 ft (1.091 m). Next, round the column diameter off to the nearest
six inches, which is 3.0 ft (1.219 m). Because the diameter is greater than 2.5 ft
(0.762 m), select a tray column.
Now, complete the calculation for the column height. The column height is
determined by the number of actual trays and the tray spacing plus the height of a
section above the top tray and an additional section below the bottom tray. The
actual number of trays equals the number of equilibrium stages divided by the
column efficiency. The column efficiency is given by Equation 6.21.10T. There is
no data for stripping a water solution in Figure 6.17. Bravo [58] states that tray

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