Page 167 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

5.2 Absorption 141

the corresponding equilibrium mole fraction in the water exiting the bottom of the
tower is determined from the equilibrium line, Eq. (2)

x ¼ 0:0028
0
Then the corresponding minimum liquid-to-gas ratio is determined by substituting
these values into Eq. (5.35), together with x 1 ¼ 0, y 1 ¼ 0:05,

y 0 y 1
L
1 y 0 1 y 1 ¼ 21:67
¼

G x 0 x 1
min
1 x 1 x 1
0
Then the minimum operating line can be determined using Eq. (5.21)

L
y x 1 x y 1
L
þ ¼ þ

1 y G 1 x G
1 x 1
min min 1 y 1
In Fig. 5.6, the minimum operating line is defined as
Y ¼ 21:66X þ 0:053 ð3Þ
The actual operating liquid to gas ratio is 1.5 times of this liquid flow rate

L
L

G ¼ 1:5 G ¼ 32:49
min
Then we can determine the actual operating line using Eq. (5.21) again, with

x 1 ¼ 0, and y 1 ¼ 0:05, and L ¼ 32:49
G
min

y x 1 L x L y 1
þ ¼ þ

1 y 1 x 1 G 1 x G 1 y 1
Which leads to, in Fig. 5.6,
Y ¼ 32:49 þ 0:053 ð4Þ
All the three lines defined by Eqs. (1), (3) and (4) are shown in Fig. 5.6.
5.2.3 Height of the Packed Absorption Tower

Another engineering interest is the height of the tower, where the minimum liquid
flow rate is known. Referring to the same schematic diagram in Fig. 5.3, and the