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388 Lawrence K. Wang et al.

7. Flow rate of combined gas stream entering the catalyst bed, Q =
com
scfm
8. Dilution airflow rate, Q = scfm
d
9. Catalyst bed requirement, V bed = ft 3
10. Fuel heating value, h = Btu/lb
f
The following should be noted:
1. If dilution air is added to the emission stream upon exit from the process, the HAP emis-
sion stream characteristics data required are the resulting characteristics after dilution.
2. The oxygen content listed above depends on the oxygen content of the organic com-
pounds (fixed oxygen) and the free oxygen in the emission stream. Because emission
streams treated by catalytic incineration are generally a dilute VOC and air mixture,
the fixed oxygen in the organic compounds can be neglected.
3. If no supplementary fuel is used, the value for the temperature of combined gas stream
entering the catalyst bed will be the same as that for the emission stream.
Example 2

Summarize the air dilution requirements for possible pretreatment of the emission stream
to a catalytic incinerator (oxidizer).
Solution

For emission stream treatment by catalytic incineration, dilution air typically will not be
required. However, if the emission stream heat content is greater than 135 Btu/lb or 10
Btu/scf for air plus VOC mixture or if the emission stream heat content is greater than 203
Btu/lb or 15 Btu/scf of inert gas plus VOC mixture, dilution air is necessary. For an emis-
sion stream that cannot be characterized as air plus VOC or inert gas plus VOC mixtures,
assume that dilution air will be required if the heat content is greater than 12 Btu/scf. In
such cases, refer to

Q = [(h /h ) − 1]Q (1)
d e d e
Q = scfm
d
Example 3

A HAP emission stream documented in Table 1 is to be treated by a catalyst incinerator. A
few important influent flue gas data are as follows:
Maximum flow rate, Q = 20,000 scfm
e
Temperature, T = 120ºF
e
Heat content, h = 24.8 Btu/lb or 2.1 Btu/scf
e
Oxygen content, O = 20.6%
2
Based on the control requirements for the emission stream, the required destruction
efficiency DE = 95%.
Determine the air dilution requirement.
Solution
The air dilution requirements for possible pretreatment of the specific emission stream to
a catalytic incinerator are presented in Example 2.
Because the heat content of the emission stream (h ) is 2.1 Btu/scf (or 24.8 Btu/lb), no
e
dilution is necessary.