Estimation of volatile organic compounds emissions from the fuel storage tanks using TANKS model and its distribution modeling by AERMOD model

Background & Volatile organic compounds (VOCs) significantly affect the chemistry of atmosphere and human health and petroleum storage has been identified as largest emitters of VOCs. With models of air pollution can model the concentration and distribution of VOCs from oil tanks. The aim of this study was to investigate and model of VOCs emissions from an oil tanks field in Iran using the TANKs 4.0.9d software and the distribution of these compounds in the study area using AERMOD model.
In this study, the rate and percentage of monthly emissions of VOCs from 22 oil storage tanks in 12 months year 2014(1392-1393) using the TANKS software were determined according to losses and tank type in Esfahan, Iran. Then, by using AERMOD model the maximum concentration of VOCs in the area with the surface of 10 × 10 km2 and with a network distance of 200m and then in the range of 50 × 50 km2 and with a network of 1000 m in the statistic period of 12 months and for a average time of 1, 3, 8 and 24 hours, one-month and one -year statistical period at the height of 1.5m of the Earth's surface was determined and the distribution of VOCs in the area was simulated and displayed by GIS software.
The results of TANKS software showed that the studied tanks were annually emitted 1485801.26 tons VOCs in which the tanks with external floating roof 99.98% and with fixed vertical roof 0.017% were contributed. The results of AERMOD software also indicated that maximum concentrations of VOCs occur in the area 10×10 km2 in cold seasons. This phenomenon is due to reduce of mixing depth and resulting in the formation of the inversion phenomenon.
This work can help plant engineers to decide on an appropriate strategy to control VOCs. Employing the tanks with fixed vertical roof and modification of operational pattern could lead to a reduction of VOCs emissions and eventually affect the economical, ecological and hygienic aspects.