Page 365 - Air Pollution Control Engineering
P. 365
07_Chap_Wang.qxd 05/05/2004 4:20 pm Page 342
342 Lawrence K. Wang et al.
Solution
θ= tan −1 (88.2/U ) = 65.6°
flg
Example 3
Determine the flare height assuming the following system data are known for a steam-
assisted elevated flare system (see Fig. 1):
Flare gas flow rate = 36,200 scfm
Flare gas heat content = 300 Btu/scf
Flare tip diameter = 60 in.
Flare gas exit velocity = 40 ft/s
Solution
Using Eq. (7)
−3
H = (0.02185)(Q × h ) 1/2 − (6.05 × 10 )(D )(U )(cos θ)
flg flg tip flg
−3
H = (0.02185)(36,200 × 300) 1/2 − (6.05 × 10 )(60)(40)(cos 65.6°)
H = 66 ft
Example 4
Determine the flare cost (FC), the purchased equipment cost (PEC), the total capital cost
(TCC), and annual cost of the steam-assisted elevated flare system illustrated in Fig. 1 and
analyzed in Example 3. Assume that the March 1990 site preparation cost (SP) and building
cost (Bldg.) are $50,000 and $100,000, respectively.
Solution
1. Determine the flare cost (FC) using Eq. (9) because H is between 30 and 100 ft.
H = 66 ft.
FC = [78 + 9.14 (D ) + 0.749 (H)] 2
tip
FC = [78 + 9.14 (54) + 0.749 (66)] 2
FC = $386,000 March 1990 cost
2. Determine the purchased equipment cost (PEC). Assume auxiliary equipment costs (i.e.,
ductwork, dampers, and fans) estimated from another chapter of this handbook series
(22) are $10,000. The equipment cost EC is then $386,000 + $10,000 = $396,000. Next,
use Table 4 to obtain the purchased equipment cost, PEC, as shown follows.
The equipment cost (EC) = flare cost (FC) + auxiliary equipment cost
= $386,000 + $10,000
= $396,000 March 1990 cost.
The purchased equipment cost (PEC) = EC + 0.1 EC (instrumentation)
+ 0.03 EC (sales taxes)
+ 0.05 EC (freight)
= 1.18 EC
= 1.18 ($396,000)
= $467,000 March 1990 cost