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382 Lawrence K. Wang et al.

emission stream temperature, and level of heat recovery, supplementary heat requirements
may be zero when heat recovery is employed.
Calculate T using the following expression if the value for T is not specified:
he he
T = (HR/100)T + [1 − (HR/100)]T (5)
he co e
where HR is the heat recovery in the heat exchanger (%) and, T is the emission stream
e
temperature (ºF).

4. ENGINEERING DESIGN AND OPERATION
4.1. Flue Gas Flow Rates
To calculate the quantity of catalyst required and cost of a catalytic incinerator, the
flow rates of the combined gas stream entering and leaving the catalyst bed have to be
determined. Equation (6) can be used to determine the inlet gas flow rate:

Q = Q + Q + Q (6)
com e f d
where Q is the flow rate of the combined gas stream entering the catalytic bed
com
(scfm), Q is the flow rate of the emission stream (scfm), Q is the natural gas flow rate
e f
(scfm), and,Q is the dilution air requirement (scfm).
d
The flue gas volume change across the catalyst bed as a result of the catalytic oxida-
tion of the HAP in the mixed gas stream is usually small, especially when dilute emission
streams are treated. Therefore, the flow rate of the combined gas stream leaving the cat-
alyst bed is approximately equal to the flow rate of the flue gas entering the catalyst bed
at standard conditions:

Q = Q (7)
fg com
where Q is the flow rate of the flue gas leaving the catalyst bed (scfm).
fg
When calculating costs, a minimum Q of 2000 scfm is typically used in catalytic
fg
incinerator design. Therefore, if Q is less than 2000 scfm, assume Q equals to 2000
fg fg
scfm in cost calculations.
In some instances, operating costs are determined based on the actual flue gas flow
rates. In these cases, the following equation can be used to convert standard condition
flow rate (scfm) to actual flow rate (acfm):

Q = Q [(T + 460)/537] (8)
fg,a fg co
where Q is the flue gas flow rate at actual conditions (acfm).
fga
4.2. Catalyst Bed Requirement
The total volume of catalyst required for a given DE is determined from the design
space velocity as follows:

V bed = 60 Q com (9)
SV
3
where V is the volume of thecatalyst bed required (ft ).
bed