Optimization of Combustion Conditions To Minimize Dioxin Emissions

Abstract

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) may enter an incinerator with the waste, be created in poor combustion or form in post-combustion zones under certain conditions of temperature and oxygen. Tests of MSW burning plants show a wide range of emissions of PCDD and PCDF. Diagnostic tests show the relationship between combustion conditions and the emission of PCDD/DF before and after emission controls. Mixing effectiveness, tightness of control, moisture, furnace and post-furnace temperatures, and the use of lime and reduced temperatures for acid-gas control all have an effect on emissions of trace organics. Carbon monoxide (CO), oxygen, moisture and furnace temperature have been found to be closely related to PCDD/PCDF emissions. By control of temperature and/or oxygen, and the use of CO as an indicator, it is possible to find and maintain optimum combustion conditions so as to minimize dioxins and furans. Plants having acid-gas controls reduce emissions below those achieved by good combustion alone.