Publication Date

5-1-1999

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are environmental pollutants that have received considerable attention because of their carcinogenic and mutagenic effects. Due to the extensive amount of data suggesting the hazards of these compounds, 16 PAHs are on the Environmental Protection Agency (EPA) Priority Pollutant List. These compounds are often emitted into the atmosphere by way of combustion processes. Thus, analysis of these compounds during coal combustion is an important task. Three 1000-hour coal combustion burns were performed using the 0.1 MW (0.3 m) bench-scale Fluidized Bed Combustor (FBC) in the Combustion Laboratory at Western Kentucky University. The data for this thesis were collected from the second and third 1000-hour experiments. An in-situ sampling system was designed for 16 PAHs specified by EPA, which consisted of a glass wool filter, condenser, glass fiber filter, Teflon filter, and Tenax. The filters and Tenax were extracted by methylene chloride and hexane, respectively, followed by GC/MS analysis using the Selective Ion Monitoring (SIM) mode. The detection limits for each of the sixteen PAHs are as low as lppb. In this study, the effects of combustion temperature, combustion bed height, fluidizing velocity, excess air ratio, and the ratio of secondary air to primary air (air staging combustion) on the emissions of PAHs were studied. The results indicated that the emissions of PAHs in an FBC system were dependent on the combustion conditions. PAHs are mainly produced by incomplete combustion. Incomplete combustion results in larger PAHs with four or more benzene rings. High efficiency combustion results in smaller PAHs with two or three benzene rings.

Disciplines

Chemistry

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