Comparative investigation of coal- and oil-fired boilers based on emission factors, ozone and secondary organic aerosol formation potentials of VOCs.

ABSTRACT

Volatile organic compounds (VOCs) are the important precursors of the tropospheric ozone (O3) and secondary organic aerosols (SOA), both of which are known to harm human health and disrupt the earth's climate system. In this study, VOC emission factors, O3 and SOA formation potentials were estimated for two types of industrial boilers coal-fired boilers (n = 3) and oil-fired boilers (n = 3). Results showed that ∑VOCs concentrations were more than nine times higher for oil-fired boilers compared to those for coal-fired boilers. Emission factors of ∑VOCs were found to be higher for oil-fired boilers (9.26-32.83 mg-VOC/kg) than for coal-fired boilers (1.57-4.13 mg-VOC/kg). Alkanes and aromatics were obtained as the most abundant groups in coal-fired boilers, while oxygenated organics and aromatics were the most contributing groups in oil-fired boilers. Benzene, n-hexane and o-ethyl toluene were the abundant VOC species in coal-fired boiler emissions, whereas toluene was the most abundant VOC species emitted from oil-fired boilers. O3 and SOA formation potentials were found 12 and 18 times, respectively, higher for oil-fired than for coal-fired boilers. Total OFP ranged from 3.99 to 11.39 mg-O3/kg for coal-fired boilers. For oil-fired boilers, total OFP ranged from 36.16 to 131.93 mg-O3/kg. Moreover, total secondary organic aerosol potential (SOAP) ranged from 65.4 to 122.5 mg-SOA/kg and 779.9 to 2252.5 mg-SOA/kg for the coal-fired and oil-fired boilers, respectively.