Characteristics and dispersion modeling of vocs emission released from the tank farm of petroleum refinery complex

Abstract

Characteristics and dispersion modeling of VOCs emitted from the tank farm of petroleum refinery complex were evaluated in this study. Gas phase VOCs within aboveground storage tank from all types of petroleum raw materials and products were sampled by the Tedlar bags prior be transferred to 6-Liter evacuated canisters and analyzed to determine their types and concentrations using the Gas Chromatography Mass Spectrophotometer (GC/MS) in accordance with the US.EPA TO-15 compendium method. Results indicated that alkane was the dominant compound in which pentane is the major contributor in total VOCs. Fraction of the concentration of pentane in total VOCs was then used to estimate its emission for further used as an input to evaluate the ambient ground level concentration of pentane through the simulation of the AERMOD dispersion model. Predicted 1-hr average concentrations were calculated to the 5-minutes average using the concept of the peak to mean concentration with the objective to evaluate the extent and magnitude of odor impacts caused by pentane. Results indicated that the highest predicted concentrations of pentane within the modeling domain simulated under the existing operation of the refinery were exceeded their RfC and odor threshold. Alternative mitigation measures to reduce emission of pentane were evaluated and compared with the existing business as usual of the refinery. Results suggested that adding of the secondary seal to the floating roof of crude oil storage tank will be the most appropriate measure taking into consideration its success in decreasing both of the emission and ground level concentration of pentane as well as demonstrate as the cheapest capital cost per unit of ambient concentration reduction. This study highlights the important in elucidating the source-receptor relationship which will assist in quantification of the contribution of emission sources towards the ambient air concentrations. Effectiveness and appropriate of mitigation control scenarios to be applied for industrial air pollution management should be taking into consideration not only their success in emission control but also on their achievement in reducing level of pollutants in the environment.