Physical and Chemical Characterization of Residual Oil-Fired Power Plant Emissions

Although the toxicity of oil combustion emissions is a significant public health concern, few studies characterize the emissions from plant-scale utility boilers firing residual oil. This study remedies that deficiency by diluting, sampling, and monitoring stack emissions from a 432 gigajoules (GJ) front-fired fossil fuel steam generator burning residual oil. Over a 3-day test period, continuous CO2, SO2, and NOx emissions monitoring confirms a steady fuel feed rate, high combustion efficiency (3.4 kg of CO2/kg of fuel oil burned), and evidence of a nocturnal soot-blowing event. The utility boiler emits fine aerosol (PM2.5) at a rate of 53 ± 2 μg/kJ (2 g/kg of oil burned). Vesicular coarse particles composed of C and S and spherical Al silicates with V and Ni inclusions are identified in a cyclone rinse using scanning electron microscopy and backscatter analysis. Ion chromatography results establish that the fine aerosol is predominantly sulfate (44% ± 0.2%, w/w) which is likely coordinated to transition metals. From thermal optical transmittance measurements, less than 1% (w/w) of the fine aerosol is surmised to be carbonaceous. Low emissions of particle-phase carbon and contaminants interfered with the gas chromatography−mass spectrometry (GC-MS) analysis of polcyclic aromatic hydrocarbons and certain other semivolatile organic compounds. However, trace levels of branched-, cyclic-, and n-alkanes and organic acids are observed in the particle emissions. Sterane and hopane molecules are below the picogram level GC-MS detection limits. Future research determining the individual organic species in the particles emitted from this source will require real-time single particle measurements. Finally, application of EPA methods TO-11 and TO-15 shows that the total volatile nonmethane organic gas emissions from the plant-scale boiler vary between 6 and 28 mg/kg of fuel oil burned; greater than 50% of this mass is ascribed to oxygenated matter.