Characteristics of PM and PAHs emitted from a coal-fired boiler and the efficiencies of its air pollution control devices
Creators: name: Chen, Tang-Wei
name: Chen, Jyh-Cherng
name: Liu, Zhen-Shu
name: Chi, Kai-Hsien
name: Chang, Moo Been
Publisher: name: Taylor & Francis
Year: 2021
Subjects: subject: Biophysics
subject: Biochemistry
subject: Space Science
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: FOS: Biological sciences
subject: 69999 Biological Sciences not elsewhere classified
subject: Inorganic Chemistry

description: Sampling and analysis of filterable particulate matter (FPM), FPM<sub>2.5</sub>, condensable particulate matter (CPM), polycyclic aromatic hydrocarbons (PAHs), sulfur oxides (SO<sub>x</sub>), and nitrogen oxides (NO<sub>x</sub>) emitted from a coal-fired boiler equipped with selective catalytic reduction (SCR)+ electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) + wet electrostatic precipitator (WESP) as air pollution control devices (APCDs) are conducted. The results show that NO<sub>x</sub> concentration emitted from the coal-fired boiler is 56 ± 2.17 ppm (with the NO<sub>x</sub> removal efficiency of 47.2%), which does not meet the best available control technology (BACT) emission standard (≤ 30 ppm). On the other hand, the WFGD adopted has a good removal efficiency for SO<sub>x</sub> and HCl. Both SO<sub>x</sub> and HCl emission concentrations are 99%. The FPM and FPM<sub>2.5</sub> emitted from the coal-fired boiler are 0.9 ± 0.06 mg/Nm<sup>3</sup> and 3, respectively. The overall removal efficiency of FPM achieved with ESP+WFGD+WESP+MGGH is 99.98%. However, high concentration of CPM (37.4 ± 6.3 mg/Nm<sup>3</sup>) is measured, which is significantly higher than FPM and FPM<sub>2.5</sub>. The concentrations of 27 PAHs at the WESP inlet and stack are measured as 667 ng/Nm<sup>3</sup> and 547 ng/Nm<sup>3</sup>, respectively while the removal efficiencies of gas- and solid-phase PAHs are 9% and 58%, respectively. The results show that APCDs adopted are not effective in removing PAHs (only 18%), and gas-phase PAHs contribute the most in the total PAH emission. In addition, the benzo(a)pyrene equivalent (BaP<sub>eq</sub>) concentration emitted from the stack is 28.8 ng-BaP<sub>eq</sub>/Nm<sup>3</sup>, and most of it is contributed by 4–6 ring PAHs with high toxic equivalent factors (TEFs). Furthermore, the emission factors of air pollutant emitted from coal-fired boilers equipped with different combinations of APCDs are compiled and compared. The results show that except for CPM and NO<sub>x</sub>, the emission factors of air pollutant calculated for this coal-fired boiler are lower if compared with other studies. <i>Implications</i>: Primary particles discharged from coal-fired processes include filterable particulate matter (FPM) and condensable particulate matter (CPM). PM<sub>2.5</sub> emissions would be greatly underestimated if CPM is ignored. Polycyclic aromatic hydrocarbons (PAHs) are semi-volatile organic compounds (SVOCs) formed by two or more fused benzene rings. PAHs have attracted much public attention because of toxicity and carcinogenicity. This study selects one coal-fired boiler with the best available control technology (BACT) to simultaneously measure the concentrations of PM, PAHs, and gaseous pollutants at the inlet and outlet of air pollution control devices (APCDs) to understand the efficacy of APCDs adopted and pollutant emission intensity.