Influence of the Combination System of Wet Flue Gas Desulfurization and a Wet Electrostatic Precipitator on the Distribution of Polycyclic Aromatic Hydrocarbons in Flue Gas from a Coal-Fired Industrial Plant

Polycyclic aromatic hydrocarbons (PAHs) are one of the major contributors to toxic organic pollutants from coal combustion. In this study, the PAHs were sampled from a coal-fired industrial plant, and the influence of the combined wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) system on PAH concentration (both in gas and particulate phases) and distribution characteristics were studied using a gas chromatograph/mass spectrometer (GC/MS). The mass concentration of total PAHs in flue gas decreased from 9.429 to 3.728 μg/Nm3 after passing through the combined WESP and WFGD. Gas-phase PAHs accounted for the main portion of total PAHs in flue gas, of which four kinds of PAHs (naphthalene, acenaphthylene, acenaphthene, and fluorene) had shown to be the major compound. The combination of WFGD and WESP had a relatively better effect on the removal of gas-phase PAHs (more than 60%) than the particulate-phase PAHs (only about 20%). Conclusively, the removal efficiencies of two- and three-ring PAHs in two phases by the combined system were much better than those of PAHs with other ring numbers. However, the removal efficiencies of the four-, five- and six-ring particulate-phase PAHs were negative. The total toxic equivalents (TEQs) of PAHs emitted from the coal-fired industrial plant in this study were 0.1277 μg TEQ/Nm3, and five-ring PAHs made the biggest contribution.