Page 276 - Air Pollution Control Engineering

05_chap_wang.qxd 05/05/2004 3:50 pm Page 255
Wet and Dry Scrubbing 255

of 50 wk/yr. Additionally, it is assumed that the factory uses the scrubbing system
3 to 8 hr shift, 5 d a week.
P = P = 47 in. H O (Example 14)
total v 2
HRS = annual operating = (3 shifts/d) (8 h/shift) (5 d/wk) (50 wk/yr) = 6,000 h/yr
−4
F = 1.81 × 10 (Q )(P )(HRS) (23)
p e,a total
F = 1.81 × 10 −4 (110,000)(47)(6,000)
p
6
F = 5.61 × 10 kWh/yr
p
b. The annual electric cost (AEC) with UEC equal to $0.059 kWh is determined
using Eq. (25):
AEC = (UEC)(F ) = $0.059(F ) (25)
p p
6
AEC= $0.059 (5.61 × 10 ) = $331,000/yr
2. The cost of scrubbing liquor (most likely water) is given by
WR = 0.6(Q ) HRS (31)
e,a
8
WR = 0.6(110,000)(6,000) = 3.96 × 10 gal/yr
The annual water cost [equals ASC in Eq. (27)] is obtained by multiplying the yearly
water requirement by the unit water cost [equals USC in Eq. (27)] found in Table
17. The USC cost water is assumed to equal $0.20 per 1,000 gal.
ASC = (USC) (ASR) (27)
8
Annual water cost = ($0.20 /1000 gal) (3.96×10 )
Annual water cost = $79,200/yr
3. Annual operating labor costs are estimated by assuming that for every 8-h shift the
Venturi scrubbing system is operated, 2 h are required to operator the wet scrubber.
With labor cost at $12.96/h (see Table 7)

Annual operating labor hours = (2 h/shift) (3 shifts/d) (5 d/wk) (50 wk/yr)
Annual operating labor hours = HRS = 1,500 h/yr
Annual operating labor cost = ($12.96/h) HRS = ($12.96/h) (1,500)=
$19,400/yr

Supervisor labor cost is estimated at 15% of operator labor cost (see Table 7).
Annual supervisor labor cost = (0.15) (annual operating labor cost)
Annual supervisor labor cost = (0.15)($19,400) = $2910/yr
4. The Annual maintenance labor cost is estimated by assuming that for every 8-h
shift the scrubbing system is operated, 1.0 h is required to maintain the wet scrub-
ber. The maintenance labor cost is based on a rate of $14.26 per hour (see Table
17). This cost is determined as follows:
Annual maintenance labor hours = (1 h/shift) (3 shifts/d) (5 d/wk)(50 wk/yr)
Annual maintenance labor hours = HRS = 750 h/yr
Annual maintenance labor cost = ($14.26 /h) HRS = ($14.26 /h)(750)
Annual maintenance labor cost = $10,695 or $10,700/yr
5. The annual maintenance materials cost is estimated by assuming it is equivalent to
100% maintenance labor cost. This cost is determined as follows:
Annual maintenance materials cost = (100%) (annual maintenance labor cost)
Annual maintenance materials cost = (1.0)($10,700) = $10,700/yr