Control of Volatile Organic Compounds Emissions from Manufacturing

Footnotes for Table E-6
a Haste gas streams with lower heating values (LHV) of about 60 Btulscf or greater can attain 1600°F combustion temperatures without
additional fuel. Standard conditions for thermal incinerator design procedure are 32°F and 1 atm.
b(j: aux) = percentage of LHV per standard cubic foot of waste gas (from Table E-4) to be supplied by auxiliary fuel. Amounts
assigned based on a conservative approximation of curve in Figure 111-2 of Reference 10.
'NO additional fuel requirement for flare stability assumed for LHV >650 Btu/scf since 10% higher than LHV of coke oven gas,
which is about 590 Btu/scf.
d Tw.g. = inlet temperature of waste gas (frm Ch. 2 and Table E-4); C02, H20, N2, 9 = lb. of waste gas combustion products per
100 lb of waste gas from Table E-5. Relationship based on following assumptions: (1) no preheat so inlet temperature of natural
gas & dilution air assumed to be 60°F; (2) adequate unrequired oxygen in waste gas and in dilution air to combust small amounts
of auxilliary natural gas for flame stability at 18 percent excess air; (3) mean specific heats(^ ) in Btu/lb OF between 60°F and
P
1800°F of 0.270 for C02, 0.517 for H20, 0.269 for N2, 0.243 for 02, and 0.261 for air; (4) natural gas composition (vol.%)
of 92% CH4, 4% C2H6, 2% C3H8,and 2 percent N2 (NW = 17.40; LHV = 20,660 Btu/lb = 1000 Btu/scf). Therefore, for combustion of 1 malo
of natural gas on a mole basis:
m or simplifying and putting on a weight basis:
I
N
--1
(2.68 lb C02 + 2.11 1b H20 + 0.03 lb N2 + 0.68 lb 02)/lb natural gas;
(5) 4.51 1 b O2 in waste gas and dilution air used for combustion of 1 l b of natural gas; (6) energy balance:
-
90 LHVWeg. [I+(% aux/100)] I(wicpi) waste gas products (1800-TW.,.) + (1800-60){C( Hi c ~ ~ x ) (Xaux ? ~ LHVwSg,) LHVnag t
[Wkp)air - 4.51(~~)~ I), where TWsg, = inlet temperature of waste gas, W = weight c = mean spec~fic heats at constant pre;sure
P
(assuming same for temperature change of TWsg. to 1800°F as for 60°F to 1800°F since Tw.g generally about 60°F-100°F, and LHV
w.g.
and LHV
n.g.
= lower heating values of the waste gas and natural gas, respectively.
e[(1.06 + 2.04 + 0.02 + 0.37) lb-mole natural gas] x [(% aux)LHV w.g. ] Btu natural gas required1100 lb waste gas + (20,660 Btu n.g.1
lb n.g. x 17.4 lb n.g./lb-nole n.g.)
f (Qwag, prod, t Qnmg.prod. + Qdil air) lb-molesl(l00 lb w.g.) x (100 lb w.g.)/100 lb w.g. x Qweg. (lblhr) x (hrl60 min) x
359 scf at 32"F)Ilb-mole.
gQf.g.(scfm) x (0.75 sec) x (min/60 sec) x (1800 t. 460) "R/492"R x (1.05) design safety factor (Reference 12).
hIfVcc c. 35.7 ft3 (minimum comercially available sire13), must add air and redesign.
IfV > 7238 ft3(maximum shop-assembled unit14), larger units would require field fabrication; therefore, assume multiple
unittcof equal sizes.