Field Measurements on the Emission and Removal of PM2.5 from Coal-Fired Power Stations: 3. Direct Comparison on the PM Removal Efficiency of Electrostatic Precipitators and Fabric Filters

Abstract

This contribution reports direct comparison of the particulate matter (PM) removal efficiencies of electrostatic precipitators (ESPs) and fabric filters (FFs) installed in two 300 MW coal-fired power station units that are equipped with identical boilers and DeNOx units. Field PM measurements were carried out at the horizontal ducts at the inlets of the DeNOx units, as well as the inlets and outlets of the two dust collectors when the two boilers burned the same coal under identical combustion conditions. The PM and total fly ash were collected via a low-pressure impactor (LPI) and/or a smoke analyzer. The collected samples were then subjected to analysis for chemical composition and morphology using an X-ray fluorescence (XRF) probe and a field emission scanning microscope with an energy-dispersive X-ray analyzer (FESEM-EDX). The results show that both the ESPs and the FFs can effectively capture PM, with a PM2.5 collection efficiency of 99.63% and 99.95%, respectively. For the PM with similar properties, the collection efficiencies in the FFs are only marginally higher than those in the ESPs. The most notable discrepancies between the fractional PM removal efficiencies of ESPs and FFs are observed for PM in the size range 0.3–2 μm. The PM removal performance of both the ESPs and the FFs is related to particle size. At 0.3–2 μm, the performance of the ESPs is more sensitive to particle size than the FFs. The PM collection efficiency of the FFs is inversely related to particle size, and the capture of PM around 0.4 μm is slightly weak, most likely due to the transition of capture mechanisms from impaction to Brownian diffusion.