Forward ultra-low emission for power plants via wet electrostatic precipitators and newly developed demisters: Filterable and condensable particulate matters

Abstract

Coal-fired power plants (CFPPs) install wet electrostatic precipitators (WESPs) or/and demisters as end control devices along with wet flue gas desulfurization (WFGD) systems to meet the ultra-low emission standards in China. This study comprehensively explores the influence of these end control devices on filterable particulate matter (FPM) and condensable particulate matter (CPM) emissions, based on field measurements and chemical analyses of collected samples. The field study was conducted in two typical CFPPs, one equipped with WESPs and the other with newly developed demisters (NDDs). With respect to FPM and filterable PM2.5, the WESP removal efficiency was 96 ± 3% and 92 ± 2%, respectively, and that of NDD was 62 ± 6% and 51 ± 5%, respectively. However, for some unconventional pollutants, the NDD removal efficiency was 60 ± 8% for CPM, which was higher than that of WESP (42 ± 10%); the removal efficiencies of HCl, SO3, and NH3 during the WESP were 78 ± 8%, 44 ± 11%, and 30 ± 5%, respectively, while they were 69 ± 16%, 58 ± 9%, and 60 ± 7%, respectively, when equipped with the NDD. Chemical composition analysis of the obtained samples revealed that the relative content of SO42− in FPM2.5 increased from 12–17% to 14–33% on using end control devices (WESP or NDD). Moreover, SO42− was the major ion component in CPM with relative ratios increasing from 15–35% to 21–59%. The mass ratio of FPM2.5 in FPMs, as well as the relative mass ratio of CPMs, in total particulate matter increased at the outlets of both control devices. The obtained results imply that both WESP and NDD effectively remove FPM and CPM to meet the ultra-low emission standards, respectively. Thus, more attention should be paid to emissions of CPM and FPM2.5 in pollution control technologies.