Page 218 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

208

2
3
ensuring liquid superficial velocity in the packing from 5 to 200 m /(m h),
2
distributed in 923 drip points per m . The concentration of the NaOH in the
liquid phase was kept constant by feeding concentrated NaOH from a Mariott
vessel. The data for the effective surface area a e for all investigated packings
(Table 2) versus liquid superficial velocity L are represented in Figs. 18-21. The
comparison of the data for a e with the specific surface area a of the
corresponding packings shows that at the maximal investigated liquid
superficial velocity used for each of them a e is greater. Le. the ratio a/a at
sufficiently high liquid superficial velocity reaches values greater than 1. It
means that the effective surface of the drops and jets trickling in the free volume
of the packing is significant.

300

200
1

—
—
_~ •—— " -—1 - - —
*
— — —
•—• , 1 • RSR0.S
• RSR 0.7
100
1 I—-—"""" • RSR1
• RSR 1,5
80 , — — • — '
A RSR 2
* RSR 3
60
6 8 10 20 40 60 80 100 200 300
L k,nfl/(nfh)
Fig. 18. Effective surface area of the investigated metal RSR versus the liquid superficial velocity.
3
2
The data for metal RSR No 3, Fig. 18, show that even at 1=10 m /(m h)
the effective surface of this packing is some higher than its specific surface area.
3 2
At Z=200 m /(m h) its effective surface is more than two times higher than its
specific one. It must be mentioned that for the most of the packing types, Figs.
19, 20 and 22 for the smallest packing elements, the line in coordinates a e-f(L)
has greater angle of inclination. Probably it is connected with different
increasing of the area of jets and drops trickling in the packing void fraction s as
well as of the wetted surface area, with increasing of the liquid superficial
velocity. For the Ralu-Flow packing such a difference in the angle of inclination
is not observed.
The influence of the packing material on the effective surface area can
be seen in Figs. 23-25, where a comparison between the effective surface of
metal and plastic RSR with one and the same dimensions for each of the
materials is presented.