Page 194 - Adsorption Technology & Design, Elsevier (1998)

180 Design procedures

10

Gases

ss.~-f ~ . . . . . . . .
_ ,,, / lJ]_
1.0

Pe'

_ S
0.1
S
S

I I I I .....
0.01
0.1 1.0 10 10 2 10 3 i0 4
Re
Figure 6.12 Variation of Peclet number with Reynolds number for axial dispersion
in both liquid and gas phase systems (adapted from Levenspiel 1972,
p. 282).

Consequently axial dispersion for porous particles may be important with
strongly adsorbed species under laminar flow conditions, even though it
may be insignificant for non-porous particles.

6.9 SCALE-UP AND PILOT-PLANT STUDIES

Several factors need to be taken into account when designing small-scale
experiments in order to obtain data for the design of full-size plant. Clearly,
it is necessary in the small-scale study to use the same fluid and adsorbent as
will be used in the full-scale plant. Special attention needs to be paid to the
choice of the length, diameter and flowrate in the small-scale experiments
since all can affect the hydrodynamics and the the dispersion characteristics.
The length of a bed is related to the cycle time and the product purity and so
a small-scale column should be long enough to retain several mass transfer
zone lengths. If a full-size design is to be based on analysis of the
breakthrough curve, it is also important to know that a constant pattern