Page 89 - Adsorption Technology & Design, Elsevier (1998)
P. 89
86 Rates of adsorption of gases and vapours by porous media
assuming that equilibrium between adsorbate and adsorbent is maintained
(Ruthven et al. 1980).
Figure 4.8 shows some experimental uptake curves for the adsorption of
CO2 in a 5A zeolite which agree very well with equation (4.39) expressing
rates of adsorption limited by heat transfer.
1.o _
0.3
3
i
0.1-
-
-
f I, I I I I I I.
20 40 60 80 1 O0 120 140
0
t(s)
Figure 4.8 Experimental uptake curves for C02 on 5A zeolite demonstrating the
limiting behaviour of heat transfer control. Adsorption temperature
273 K. Figures on curves represent various adsorbate pressures which
relate to differing effective heat capacities. Curve l, 4.3 - 3.6 torr; curve 2,
20-17 torr; curve 3, 68 - 63 torr; curve 4, 234 - 204 tort.
4.3 EXPERIMENTAL MEASUREMENT OF DIFFUSION
COEFFICIENTS CONCOMITANT WITH ADSORPTION
It should be apparent from what has been discussed in the whole of Section
4.2 that adsorption rates depend explicitly on values of the diffusion
coefficient of the adsorbing fluid. A number of experimental techniques
have been developed for the measurement of diffusion coefficients, some of
which are outlined in the following Sections 4.3.1 to 4.3.4.
