Influence of flue gas desulfurization (FGD) installations on emission characteristics of PM2.5 from coal-fired power plants equipped with selective catalytic reduction (SCR)

- Flue gas desulfurization increases primary PM2.5 emission from coal-fired power plants.
- Flue gas desulfurization increases NH4+ aerosol emission by converting unreacted NH3.
- Changes of PM2.5 in flue gas system of coal-fired power plants were measured.

Flue gas desulfurization (FGD) and selective catalytic reduction (SCR) technologies have been widely used to control the emissions of sulphur dioxide (SO2) and nitrogen oxides (NOX) from coal-fired power plants (CFPPs). Field measurements of emission characteristics of four conventional CFPPs indicated a significant increase in particulate ionic species, increasing PM2.5 emission with FGD and SCR installations. The mean concentrations of PM2.5 from all CFPPs tested were 3.79 ± 1.37 mg/m3 and 5.02 ± 1.73 mg/m3 at the FGD inlet and outlet, respectively, and the corresponding contributions of ionic species were 19.1 ± 7.7% and 38.2 ± 7.8%, respectively. The FGD was found to enhance the conversion of NH3 slip from the SCR to NH4+ in the PM2.5, together with the conversion of SO2 to SO42−, and increased the primary NH4+ and SO42− aerosol emissions by approximately 18.9 and 4.2 times, respectively. This adverse effect should be considered when updating the emission inventory of CFPPs and should draw the attention of policy-makers for future air pollution control.

The flue gas desulfurization (FGD) system could enhance conversion of NH3 slipped from selective catalytic reduction (SCR) to NH4+ in PM2.5, before the flue gas have been emitted into the atmosphere, and thereby increasing primary NH4+ aerosol emissions by approximately four times.144