Tw

Temperature:

Tp = Waste gas from process

Tw = Waste gas leaving heat exchanger or entering combustion chamber Taf = Auxiliary fuel Ta = Combustion air TE = Flue gas

Ts = Flue gas leaving heat exchanger or stack temperature

FIG. 5.21.4 Schematic diagram of incinerator system.

is a comprehensive review that includes regulatory aspects, current practice, technology, emissions and their measurements, control parameters, performance indicators, and risk assessment.

In thermal incinerators, Tw is usually below 1000-1100°F (to avoid preignition); as Tw increases, auxiliary fuel requirements can decrease. For a system with a recuperative heat exchanger, Tw can be calculated as follows:

where ^ represents the efficiency of the heat exchanger (see Figure 5.21.2). Standard heat transfer texts provide the equations for estimating ^ as well as the requisite material and energy balances.

If the wastes to be destroyed contain chlorine, higher temperatures may be required, and APCD needs increase, specifically the necessity to control HCl emissions. In addition, the PIC mix is more complex when organochlorine compounds are present and may require the application of Appendix VIII compound sampling techniques. Dempsey and Oppelt summarize these methods in a table.

CEMs are often used (or are required) for combustion gas components such as CO, CO2, O2, NOx, and THC, one or more of which serves as a performance indicator. Again, if chlorinated compounds are combusted, continuous monitoring of HCl can be necessary. The methodology is the same as for CO and CO2, namely NDIR. Nitrogen-containing compounds can form NOx, S-con-taining compounds lead to SO2 and perhaps some SO3, P-containing compounds lead to P2O5 (a highly corrosive compound), and Br-, F-, and I-compounds form the corresponding acids.

Gaseous hazardous waste can lead to higher molecular weight PICs; for example, the combustion of methyl chloride (while yielding mainly CO2 and HCl) can also lead to species such as chloroethanes and chlorobenzenes.

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