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354 Lawrence K. Wang et al.

Table 3
Thermal Incinerator System Design Variables
Nonhalogenated stream Halogenated stream
Required
destruction Combustion Residence Combustion Residence
efficiency temperature time temperature time
(DE) (%) T (ºF) t (s) T (ºF) t (s)
c r c r
98 1600 0.75 2000 1.0
99 1800 0.75 2200 1.0
Source: ref. 4.

DE, appropriate values for T and t can be selected from Table 3. For more information on
c r
temperature requirements versus destruction efficiency, consult Appendix D of ref. 7.
Because the performance of a thermal incinerator is highly related to the combustion
chamber and outlet gas temperature, any thermal incinerator system used to control
HAPs should be equipped with a continuous-temperature-monitoring system. Most
vendors routinely equip thermal incinerators with such a system (5). However, some
older units may not have a continuous-temperature-monitoring system. In this case, a
retrofit installation of such a system should be requested.
In addition to temperature and residence time, good mixing of the gas streams is
essential for proper operation. Unfortunately, mixing cannot be measured and quanti-
fied during design calculations. Typically, mixing is adjusted and improved during the
start-up period of an incinerator. It is ultimately the responsibility of the operator to
ensure correct operation and maintenance of a thermal incinerator after start-up.
In a system evaluation, if the design values for T and t are sufficient to achieve the
c r
required DE (compare the design values with the values from Table 3), the system
design is considered acceptable. If the reported values for T and t are not sufficient,
c r
the design may be corrected by using the values for T and t from Table 3. (Note: If the
c r
DE is less than 98%, obtain information from the literature and incinerator vendors to
determine appropriate values for T and t .)
c r
Table 4 contains theoretical combustion chamber temperatures for 99.99% destruc-
tion efficiencies for various compounds with a residence time of 1 s. Note that the
theoretical temperatures in Table 4 are considerably lower than those given in Table 3.
This difference is because the values in Table 4 are theoretical values for specific com-
pounds, whereas the values given in Table 3 are more general values designed to be
applicable to a variety of compounds. Therefore, values in Table 3 are conservatively
high. Table 4 is provided to indicate that certain specific applications may not require
as high a combustion chamber temperature as those given in Table 3. Because the val-
ues given in Table 4 are theoretical, they may not be as applicable in the system design
as the values in Table 3.
As a practical matter, a specific temperature to provide a specific destruction effi-
ciency cannot be calculated a priori. Typically, incinerator vendors can provide general
guidelines for destruction efficiency based on extensive experience. Tables 3 and 4
are presented to show a range of differences between theoretical and general values.
In essence, these tables are used as a substitute for design equations relating destruction