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Catalytic Oxidation 379

Table 4
Catalytic Incinerator System Design Variables
Required Temperature at Temperature at Space velocity Space velocity
−1
−1
destruction the catalyst bed the catalyst bed SV (h ) SV (h )
a
b
efficiency DE (%) inlet T (ºF) outlet T (ºF) Base metal Precious metal
ci co
95 600 1,000–1,200 10,000–15,000 c 30,000–40,000 c
98–99 600 1,000–1,200 d d
a Minimum temperature of combined gas stream (emission stream + supplementary fuel combustion
products) entering the catalyst bed is designated as 600ºF to ensure an adequate initial reaction rate.
b Minimum temperature of the flue gas leaving the catalyst bed is designated as 1000ºF to ensure an ade-
quate overall reaction rate to achieve the required destruction efficiency. Note that this is a conservative
value; it is in general, a function of the HAP concentration (or heat content) and a temperature lower than
1000ºF may be sufficient to achieve the required destruction level. The maximum temperature of flue gas
leaving the catalyst bed is limited to 1200ºF to prevent catalyst deactivation by overheating. However, base
metal catalysts may degrade somewhat faster at these temperatures than precious metal catalysts.
c The space velocities given are designed to provide general guidance not definitive values. A given
application may have space velocities that vary from these values. These values are quoted for monolithic
catalysts. Pellet-type catalysts will typically have lower space velocities.
d In general, the design of catalytic incinerator systems in this efficiency range is done relative to specific
process conditions.
Source: US EPA.

ensure that an adequate overall reaction rate can be achieved to give the desired DE
without damaging the catalyst, check whether T falls in the interval 1000–1200ºF.
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Then, check whether the reported value for SV is equal to or less than the value in Table
4. In some cases, it may be possible to achieve the desired DE at a lower temperature
level. If a permit applicant uses numbers significantly different from those in Table 4,
documentation indicating the rationale for this variance should accompany the applica-
tion. In this case, the permit values should take precedence over those values given in
Table 4. Otherwise, the applicant’s design is considered unacceptable. In such a case,
the reviewer may then wish to use the values in Table 4.

3. SUPPLEMENTARY FUEL REQUIREMENTS
Supplementary fuel is added to the catalytic incinerator system to provide the heat
necessary to bring the emission stream up to the required catalytic oxidation temperature
(T ) for the desired level of DE. For a given T , the quantity of heat needed is provided
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by (1) the heat supplied from the combustion of supplementary fuel, (2) the sensible heat
contained in the emission stream as it enters the catalytic incinerator system, and (3) the
sensible heat gained by the emission stream through heat exchange with hot flue gases. If
recuperative heat exchange is not practiced at a facility, then item (3) will be zero.
Because emission streams treated by catalytic incineration are dilute mixtures of VOC
and air, they typically do not require additional combustion air. For purposes of this
handbook, it is assumed that no additional combustion air is required if the emission
stream oxygen content is greater than or equal to 20%.
Before calculating the supplementary heat requirements, the temperature of the flue
gas leaving the catalyst bed (T ) should be estimated to ensure that an adequate over-
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all reaction rate can be achieved to give the desired DE without damaging the catalyst.