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4.2 Design of Adsorption and Ion-Exchange Processes 325

The Reynolds number is 0.78, and the resin particles can be assumed to be spherical.
Then the most appropriate correlation is that of Chung (eq. (3.314)). The resulting particle
Peclet number is 0.51, and thus, the bed Peclet number is 114.93, which is f and airly high,
plug flow condition can be considered to take place.

Example 7
Murillo et al . (2004) studied the adsorption of phenanthrene (polycyclic aromatic hydro-
,
ix
carbon –PAH) from helium as carrier gas on a coke fed-bed adsorber at 150 °C. The
isotherm of the phenanthrene–coke system at 150 °C was found to be of Freundlich type
with Fr = 0.161 and K F = 1.9 (mol/kg)(m 3 /mol) 0.161 . The isotherm has been deried for v
phenanthrene concentrations between 1.71 10 4 and 1.35 10 2 mol/m 3 . Finally, the
icient,
f
average solid-phase diffusion coef calculated from seeral experimental runs, w v as
found to be 6.77 10 8 cm 2 /s.
Suppose that coke is available with particle density of 1 g/cm 3 and particle size of 1 mm.
The bed diameter is 0.2m, its height is 1 m, and the bed porosity is 0.5. The gas stream to
be treated is helium containing 4.74 10 3 mol/m 3 phenathrene.
Using the Miura–Hashimoto models, calculate the time needed to reach a breakpoint of
10% of the inlet concentration under a flow rate of 31,400 cm 3 /s.

Solution
The Reynolds and Schmidt numbers are

du ps
Re p 4.56

Sc 9.42
D f

Then, using the correlation of akao for gases (eq. (3.351)): W

1.1
2
Sh Sc Re 0.33 p 0.6 7.73
then
kd fp
Sh k 18.01 cm/s
f
D f

The solid side mass transfer coef icient is f

15 D 3
sb
ka su 2 0.000203 g/sc m
r
o