Characteristics of Fine Particulate Matter and Polycyclic Aromatic Hydrocarbons Emitted from Coal Combustion Processes

Characteristics and emission factors of condensable particulate matter (CPM) and filterable particulate matter (FPM_2.5) and polycyclic aromatic hydrocarbons (PAHs) (16 U.S. EPA PAHs and 15 + 1 EU PAHs) emitted from a coal-fired power plant (plant A) and a coal-fired boiler (plant B) in Taiwan were investigated via stack samplings. Removal efficiencies of CPM, FPM_2.5, and PAHs achieved with baghouse (BH) + seawater flue gas desulfurization (SWFGD) were also evaluated for plant A. Results indicate that CPM concentrations measured in plants A and B are 12.7 ± 1.44 and 28.0 ± 6.32 mg/Nm³, respectively, which are significantly higher than FPM_2.5 concentrations measured in two plants. The CMP/FPM ratios measured in plants A and B are 12.7 ± 1.44 and 28.0 ± 6.32, respectively. The organic content is the major contributor to CPM collected from plant A (90 ± 3.7%), while the inorganic content contributes 93 ± 2.4% of CPM collected from plant B. Furthermore, different compositions of soluble ion are found in CPM/FPM collected from the stacks of plants A and B. This difference might be attributed to different coal used, varying combustion efficiencies, and different removal efficiencies of organic and inorganic contents achieved with different air pollution control devices (APCDs) with different operating temperatures in plants A and B. The average PAH concentrations measured at stacks of plants A and B are 28.4 and 43.4 μg/Nm³, respectively. Gaseous PAHs predominate in terms of both mass and toxic equivalency (TEQ) concentrations, acounting for 99.5 and 96.0%, respectively. The 15 + 1 EU PAHs contribute 99.0 and 99.99% to total TEQ of gaseous and particulate PAHs, respectively. The removal efficiency of CPM achieved with BH and SWFGD of plant A is 38.3%, which is significantly lower than that of FPM_2.5 (99.8%) and PM (99.9%). The PAH removal efficiency achieved with APCDs in plant A increases as the ring number increases. The overall PAH removal efficiencies achieved with the APCDs of plant A are 89.8 and 94.3% based on mass and TEQ concentrations, respectively.