Page 233 - Air Pollution Control Engineering

05_chap_wang.qxd 05/05/2004 3:46 pm Page 212
212 Lawrence K. Wang et al.

Table 4
Schmidt Numbers for Compounds in Water at 68°F and 1 atm
Solute a Sc b Solute a Sc
L L
Oxygen 558 Glycerol 1400
Carbon dioxide 559 Pyrogallol 1440
Nitrogen Oxide 665 Hydroquinone 1300
Ammonia 570 Urea 946
Bromine 840 Resorcinol 1260
Hydrogen 196 Urethane 1090
Nitrogen 613 Lactose 2340
Hydrogen chloride 381 Maltose 2340
Hydrogen sulfide 712 Mannitol 130
Sulfuric add 580 Raffinose 2720
Nitric acid 390 Sucrose 2230
Acetylene 645 Sodium chloride 745
Acetic acid 1140 Sodium hydroxide 665
Methanol 785 Carbon dioxide c 445
Ethanol 1105 Phenol c 1900
Propanol 1150 Chloroform c 1230
Butanol 1310 Acetic acid d 479
Allyl alcohol 1080 Ethylene dichloride d 301
Phenol 1200
a Solvent is water except where indicated.
b Sc = µ /P D , where µ and P are the viscosity and density of the liquid, respectively, and D is the
L L L L L L L
diffusivity of the solute in the liquid.
c Solvent is ethanol.
d Solvent is benzene.
Source: ref. 13.

2.4.4. Packed Tower (Wet Scrubber) Operation and Maintenance
As previously mentioned, the pressure drop (head loss) through a packed tower (see
Fig. 1b) has a major impact on the economics of a tower. When in the design phase, the
most accurate pressure drop data for a given packing should be provided by the packing
supplier. However, for the purpose of a general example, the following is a relatively
accurate correlation:
P = ( −8 )[ ( rL D L ) G ) 2
′′
a g × 10 10 ](3 600, area D G (21)
2
where P is the pressure drop (lb/ft -ft) and g and r are the packing constants from
a
Table 5 (4).
The total pressure drop through a packed tower (see Fig. 1b) wet scrubber is
P = P Ht (22)
total a column
The fan power requirement, F (in kWh/yr), is calculated as follows:
p
F = 1.81 × 10 −4 (Q )(P )(HRS) (23)
P e,a total
where F is the fan power requirement (kWh/yr), Q is the actual emission stream flow
P e,a
rate (acfm), P is the system pressure drop (in. H O), and HRS is the system operating
total 2
hours per year (h/yr).