Page 152 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

126 5 Principles for Gas Separation

Table 5.4 (continued)
Formula Name a b d
C 2 H 5 NO N-Methylformamide 1.23333 0.21723 –
C 2 H 5 NO 2 Nitroethane 0.44968 0.49708 −0.04612
Ethane −2.40393 0.68107 −0.01925
C 2 H 6
C 2 H 6 O Ethanol −0.51153 0.67525 −0.04473
C 2 H 6 OS Dimethyl sulfoxide 1.24042 0.31302 −0.04768
Source [16]. More data can be found in Table A.6

to use these values, the unit of M eq;g=100 g must be (g adsorbate/100 g adsorbent) and
C ppmv in ppmv.
2
For many engineering processes, the last term d log C ppmv is negligible, and
10
a simplified formula can be used for estimation with a reasonable accuracy. For
adsorbate concentrations lower than 50 ppmv, the error is less than 5 %.
Example 5.1: VOC adsorption using AC
In an automobile assembling shop, the concentration of n-butanol (C 4 H 10 O) in the
3
room air is 5 ppmv. The density of n-butanol is 3.06 kg/m under standard room air
conditions. A carbon filter bed is used for air cleaning, and the airflow rate is
3
0.1 m /s through the filter. Determine
a. the adsorption capacity of the activated carbon filter,
b. the total carbon mass needed for the bed, assuming the working adsorption
capacity is 40 % of the maximum potential and the bed service life is one year.

Solution
a. From Table 5.4, we have the adsorption constants of C 4 H 10 O:

a ¼ 0:89881; b ¼ 0:32534; d ¼ 0:03648

Then Eq. (5.9) leads to
2
log M eq;g=100 g ¼ a þ blog C ppmv þ d log C ppmv
10
10
10
2
5
¼ 0:89881 þ 0:32534log ðÞ 0:03648 log ðފ ¼ 1:1084
5
½
10
10
M eq;g=100 g ¼ 10 1:1084 ¼ 12:8 gram of C H 10 O per 100 gram of carbonÞ
ð
4
b. The total amount of n-butanol passing through the carbon bed in 1 year is
3
3
m air m n bu kg
m ¼ QCq g t ¼ 0:1 0:000005 3:05 ð365 24 3600Þ s
3
3
s m air m n bu
¼ 48:1kg