Control of dioxin, furan, and mercury emissions from municipal waste combustors

摘要

There is a significant public and scientific concern over the potential risks of air pollution emissions from municipal waste combustors (MWCs). The primary pollutants of concern are polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs), and mercury (Hg). Depending on the composition of the waste and the technologies used, PCDD/PCDF emissions may range from less than 1.0 to more than 20 000 ng/dscm. Hg concentrations in MWC flue gas may range from less than 200 to more than 1000 μg/dscm. Trace organic emissions are dependent on the combustion and flue gas cleaning technologies employed and the conditions at which they are operated. Good combustion practice and dry scrubbing techniques employing fabric filter (FF) bag houses can be used to reduce average PCDD/PCDF emissions to less than 20 ng/dscm. Dry scrubbers in combination with electrostatic precipitators (ESPs) are less effective, resulting in typical PCDD/PCDF emissions of less than 75 ng/dscm. Powdered activated carbon can be injected into the flue gas to reduce Hg emissions from spray dryer (SD)/FF and SD/ESP systems to less than 0.08 mg/dscm. It can also be used to improve PCDD/PCDF capture in these systems. This article provides an overview of MWC air pollution control technologies and applicable Federal air emission control requirements. Knowledge concerning PCDD/PCDF formation is summarized, and data are provided on the performance of combustion and flue gas cleaning techniques used to control PCDD/PCDF emissions. The fundamental Hg properties which affect capture in flue gas cleaning equipment are discussed, and the results of carbon injection control tests are summarized.