Comparison of Coal- and Oil-Fired Boilers through the Investigation of Filterable and Condensable PM_2.5 Sample Analysis

Abstract

This study investigated the characteristics of both filterable fine particulate matter (FPM) and condensable particulate matter (CPM) emitted from coal-fired boilers (CFBs) and oil-fired boilers (OFBs) via field sampling. FPM and CPM samples were collected using USEPA Method 201A and Method 202, respectively. Mass concentrations and chemical compositions (including water-soluble ions, metal elements and carbon contents) of collected PM2.5 samples were analyzed. The results show that PM2.5 (FPM + CPM) emission concentrations for CFBs and OFBs are 20.2 ± 10.4 and 157 ± 82.7 mg/Nm3, respectively. In terms of the emission factor, emission of FPM from OFBs is 307.4 ± 50 g/kL of oil and from CFBs is 57.1 ± 13.8 g/t of coal. Significantly higher concentrations are emitted from OFBs than from CFBs due to the reason that better control devices are installed in most CFBs. The average CPM fraction constitutes 58.7 and 54.8% of PM2.5 for CFBs and OFBs, respectively, showing that CPM from the boilers contributes a significant fraction of PM2.5 emissions. FPM sample analysis reveals that SO42– is the primary characteristic of water-soluble ion and occupies 64.2 and 80.6% of total water-soluble ions for CFBs and OFBs, respectively. SO42– is a main contributor of ions, while NO3– follows. The species in CPM are dominated by water-soluble ions, including SO42–, NO3–, and NH4+. The results indicate that CPM is formed primarily by water-soluble ions. The results also show that organic carbon (OC) concentrations are predominant for CFBs, and elemental carbon (EC) is predominant for OFBs.