Page 155 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

5.1 Adsorption 129

M eq ¼ 0:01M eq;g=100 g ð5:12Þ

6
C 0 ¼ 10 q C ppmv ð5:13Þ
g
where the factor of 10 6 converts adsorbate concentration from ppmv to
3 3
m adsorbate per m of gas . q is not the density of the entire gas phase, but
g
3
rather that of the adsorbate ðkg/m Þ.
Example 5.2: Adsorption wave propagation speed calculation
Same as the parameters given in Example 5.1 above, in an automobile assembling
shop, the concentration of n-butanol (C 4 H 10 O) in the room air is 5 ppmv. The
3
density of n-butanol is 3.06 kg/m under standard condition. A carbon filter bed is
3
used for air cleaning, and the airflow rate is 0.1 m /s through the bed. The activated
carbon bed is manufactured in such a way that its bulk density of the activated
3 2
carbon is 400 kg/m . The cross-sectional area of the bed is 2 m . Estimate the
propagation speed of the adsorption wave.
Solution
From Example 5.1, we obtained

M eq;g=100 g ¼ 12:8 gram of C H 10 O per 100 gram of A:C:ð 4 Þ

Unit conversion gives

M eq ¼ 0:01M eq;g=100 g ¼ 0:128 kg VOC/kg ACð Þ
6 6 5 3
C 0 ¼ 10 q C ppmv ¼ 10 ð 3:06Þ 5 ¼ 1:53 10 ðkg VOC/m Þ
g
Then we can get the adsorption wave propagation speed as

QC 0
V az ¼
M eq q A
b
3
3
0:1m =sÞ 1:53 10 5 kg VOC/m
ð
¼ 3
2
0:0128 kg VOC/kg ACÞ 400 kg AC/m 2m Þ
ð
ð
6
ð
¼ 0:01494 10 ð m/sÞ ¼ 0:0538 mm/hÞ
5.1.5 Breakthrough Time
With the known wave propagation speed, we can easily predict the operating time
of a fresh column.