Page 257 - Air Pollution Control Engineering

05_chap_wang.qxd 05/05/2004 3:46 pm Page 236
236 Lawrence K. Wang et al.

2
L'' = 1612 lb/h-ft (Example 7)
2
3600G = (3600)(0.34) = 1224 lb/h-ft (Example 7)
area
3
D = 0.071 lb/ft (Example 5)
G
3
D = 62.18 lb/ft at 85°F (Example 5)
L
Substituting these values into Eq. (21) to determine pressure drop (P ):
a
2
P = (g × 10 −8 [10 (r L"/D ) ) /D (21)
L ] (3600G
a area G
2
−8
P = (11.13 × 10 ) [10 (0.00295)(1612 ) / 62.18 ] (1224) / 0.071
a
−8
P = (11.13 × 10 ) [10 (0.07648) ] (1,498,176) / 0.071
a
−8
P = (11.13 × 10 ) [1.1926] (1,498,176) / 0.071
a
2
P = 2.78 lb/ft -ft
a
The total pressure drop through a packed tower or wet scrubber can then be calculated:
Ht = 23 ft (from Example 7)
column
P = P Ht (22)
total a column
P = (2.8)(23) = 64.4 lb/ft 2
total
P /5.2 = 12.4 in. H O
total 2
Example 10
In this exercise, the initial (capital) costs and operating costs of a wet scrubber are esti-
mated. These costs include initial cost of purchase as well as direct and indirect annual
costs (or total annual costs). Recovery credit is assumed to be negligible.
Solution
A. Total Cost of Absorption (Wet Scrubber) Systems
The cost of the absorption system can be found in Figure 7. The cost of packing
required to fill the tower is estimated using Table 2 with the volume of packing deter-
mined in the previous discussion. Likewise, secondary costs for related equipment
were also previously determined. Summation of these costs will determine the total
capital outlay needed for this wet scrubber.
1. Absorber tower cost = $
2. Packing cost = $
3. Auxiliary equipment cost = $
4. Equipment cost (EC) = 1 + 2 + 3 = $
The purchased equipment cost, PEC, is obtained from the equipment cost determined
above and the factors found in Table 6.
PEC = EC + instrumentation + taxes + freight charges
PEC = $
Total capital cost (TCC) is estimated using the above calculated PEC and the factors
found in Table 6.
TCC = 2.20PEC + SP + building cost
TCC = $
where SP is the site preparation cost ($).

B. Direct Annual Cost of a Wet Scrubber System (Absorber)
The total annual costs of a scrubber system include direct costs of power, solvent
(absorbent), labor, and so form. Additionally, indirect costs such as taxes, administra-
tive costs, insurance, and so on. must also be considered to fully appreciate the total
capital demanded to operate a scrubber system for a full year.