Page 254 - Air Pollution Control Engineering

05_chap_wang.qxd 05/05/2004 3:46 pm Page 233
Wet and Dry Scrubbing 233

Assume an adsorption factor of 1.6, then

1/AF = 1/1.6 = 0.63.
Use these values in Fig. 3 to determine N :
og
N =
og
B. With Eqs. (16), (17), and (15), H (height of gas transfer unit), H (height of liquid
G L
transfer unit), and H og (height of overall gas transfer) are determined. Packing con-
stants needed in Eqs. (16) and (17) are found in Tables 1 and 2.
b = c = d =
Y = s =

Also using Tables 3 and 4, the Schmidt numbers are
Sc = ________ Sc = _______
G L
Thus, the liquid flow rate is determined from Eq. (18).
L'' = L/A column (18)
L'' = lb/h-ft 2

From ref. 1, the solvent viscosity value is found:
µ '' = lb/h-ft 2
L
Now determine the values for H and H from Eqs. (16) and (17), respectively:
G L
d
c
H = [b(3600G area ) / (L'') ] (Sc ) 0.5 (16)
G
G
H = ft
G
s
H = Y (L''/µ '') (Sc ) 0.5 (17)
L
L
L
H = ft
L
Calculate H using Eq. (15) and an assumed value for AF of 1.6:
og
H = H + (1/AF) H (15)
og G L
H = ft
og
C. Equation (12) is now used to determine the height of the column:
Ht = N × H (12)
column og og
Ht = ft
column
D. Now use Eq. (19) to determine Ht
total
Ht = Ht + 2 + (0.25D ) (19)
total column column
Ht = ft
total
E. The volume of packing needed to fill the tower is determined from Eq. (20).
2
V = (π/4) (D ) (Ht ) (20)
packing column column
V = ft 3
packing
Example 7
A wet scrubber (packed tower; Fig. 1b) is proposed to treat Emission Stream 5 in Table 11.
With the results from Examples 3 and 5, the column height and packing volume are
determined using the procedure explained in Example 6.