Page 418 - Air Pollution Control Engineering

09_chap_wang.qxd 05/05/2004 5:01 pm Page 390
390 Lawrence K. Wang et al.

T = 600 + 50h (2)
co e
T = ºF
co
If T falls in the interval of 1000 –1200ºF, proceed with the calculation. If T is less than
co co
1000ºF, assume T is equal to 1000ºF and use the following equation to determine an
co
appropriate value for T ; and then proceed with the calculation:
ci
T = 1000 − 50h (3)
ci e
T = ºF
ci
(Note: If T is greater than 1200ºF, a decline in catalyst activity may occur as a result of
co
exposure to high temperatures.)
2. Use the following equation to determine supplementary fuel requirements:
e[
DQ Cp (11. T − T − 01. T )]
ci
r
he
e
air
Q =
f f[ T − )] (4)
Dh − 11. Cp ( ci T r
f
air
The values for the variables in this equation can be determined as follows:
Q Input data
e
D 0.0739 lb/ft 3
e
D 0.0408 lb/ft 3
f
h Assume a value of 21,600 Btu/lb (for natural gas) if no other informa-
f
tion available
C p air See Table 5 for values of C p air at various temperatures.
T Obtain value from part “a” above or from permit applicant.
ci
T For the no heat recovery case, T = T . For the heat recovery case, use the
he he e
following equation if the value for T is not specified:
he
T = (HR/10)T + [1 − (HR/100)]T (5)
he co e
Assume a value of 50% for HR if no other information is available.
T r 77ºF
Q = scfm
f
Example 7
Use the step-by-step procedure outlined in Example 6 to determine the flue gas flow rate
Q in scfm when a catalytic incinerator is selected to treat the HAP emission stream docu-
f
mented in Table 1.
Solution
Because the emission stream is dilute (h = 2.1 Btu/scf) and has an oxygen concentration
e
greater than 20%, Eqs. (2)–(4) are applicable.
1. Determine if T falls in the range 1000–1200ºF
co
T = 600ºF
ci
h = 2.1 Btu/scf (input data)
e
T = 600 + (50 × 2.1) = 705ºF
co
Because T is less than 1000ºF, use Eq. (3) to calculate a required value for T :
co ci
T = 1000 − (50 × 2.1) = 895ºF
ci