Stefano Carletti, Giovanni Di Nicola, Giorgio Passerini

Evaluation of fugitive emissions of hydrocarbons from a refinery during a significant pollution episode

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Abstract

Hydrocarbons and other Volatile Organic Compounds (VOC) a central role in the formation of ground level ozone, photochemical oxidants. High levels of photochemical smog and the related smog episodes are harmful to the ecosystem. Although allowed concentration levels are higher, there are also public health concerns about exposure to hydrocarbon vapors themselves. The main anthropogenic VOC sources are road traffic, the production and use of solvents and oil refineries. On August 2000 several pollution episodes occurred nearby Ancona. Data acquired at monitoring stations showed very high levels of Hydrocarbons that were almost certainly due to fugitive emissions from an oil refinery located at short distance. Such emissions are always difficult to quantify. However, the simplest inventory methodology combines the crude oil throughput of refinery with a single emission factor, for fugitive process-emissions. The aim of this study was to quantify “a posteriori” the fugitive emissions of hydrocarbons from the oil refinery during the significant pollution episodes. We applied a regulatory air dispersion model, namely AERMOD, to simulate the concentrations of Non Methane Hydrocarbons during August 2000 and to assign reliable fugitive emissions at API refinery. Dispersion models are deterministic models, based upon physical theories, that use source emission data, meteorology, and topography to create maps of pollutant concentrations. Such maps can be used to predict source-specific exposures. For this study, we focused on the oil refinery and its power plant, both located in Falconara Marittima (nearby Ancona, Central Italy) but we also considered all the main roads as line sources, while both combustion and other emissions sources were introduced as area sources. The modeling system run about 30 times using different emission values. The results showed that fugitive emissions of VOCs in the refinery might have been, on August 2000, several times higher than those estimated by the refinery Company. Besides the obvious issues deriving from every emission underestimate, the VOC miscalculation in Falconara refinery may have fouled models so to misjudge ozone dynamics nearby.

Keywords:Volatile Organic Compounds; ozone; AERMOD; oil refinery.