Page 386 - Air Pollution Control Engineering

08_chap_wang.qxd 05/05/2004 4:26 pm Page 361
Thermal Oxidation 361

Solution

The following are important elements of a calculation sheet for thermal incineration:
1. Data requirement for HAP emission stream characteristics:
1. Maximum flow rate, Q = scfm
e
2. Temperature, T = ºF
e
3. Heat content, h = Btu/scf
e
4. Oxygen content, O = %
2
5. Halogenated organics: Yes No
6. Required destruction efficiency, DE = %
2. In the case of a permit review, the following data should be supplied by the applicant:
Thermal incinerator system variables at standard conditions (77ºF, 1 atm):
1. Reported destruction efficiency, DE = %
reported
2. Temperature of emission stream entering the incinerator,
T = ºF (if no heat recovery)
e
T = ºF (if a heat exchanger is employed)
he
3. Combustion temperature, T = ºF
c
4. Residence time, t = s
r
5. Maximum emission stream flow rate, Q = scfm
e
6. Fuel heating value, h = Btu/lb
f
7. Combustion chamber volume, V = ft 3
c
8. Flue gas flow rate, Q = scfm
fg
It should be noted that (1) if dilution air is added to the emission stream upon exit from
the process, the data required are the resulting characteristics after dilution and (2) the
oxygen content depends on the oxygen content of the organic compounds (fixed oxygen)
and the free oxygen in the emission stream. Because emission streams treated by thermal
incineration are generally dilute VOC and air mixtures, the fixed oxygen in the organic
compounds can be neglected.
Example 2

Outline a step-by-step procedure for the determination of dilution air requirements,
combustion temperature, and residence time of a thermal incinerator.

Solution
1. Pretreatment of the emissions stream: dilution air requirements. Typically,
dilution will not be required. However, if the emission stream heat content (h ) is
e
greater than 176 Btu/lb or 13 Btu/scf with an oxygen concentration less than 20%,
the dilution airflow rate (Q ) can be determined using
d
Q = ( [ e ]
d
d h h ) −1 Q
e
Q = scfm
d
2. Design variables, destruction efficiency, and typical operational problems. Based
on the required destruction efficiency (DE), select appropriate values for T and t
c r
from Table 3.
T = ºF
c
t = s
r