Gas Processing Journal Vol. 7, No. 2, 2019, pp. 53-66 http://gpj.ui.ac.ir DOI: http://dx.doi.org/10.22108/gpj.2019.117376.1057 ___________________________________________ * Corresponding Author. Authors’ Email Address: A. R. Falsafi (alireza.falsafi@gmail.com), 2 A. Mohebbi (amohebbi2002@yahoo.com), 3 A. Baghaei (ali.baghaei@gmail.com) ISSN (Online): 2345-4172, ISSN (Print): 2322-3251 © 2020 University of Isfahan. All rights reserved Simulation of Flammable and Toxic Gases Released from Condensate Storage Tank in a Gas Plant Based on Elevation Change Alireza Falsafi 1,2 , Ali Mohebbi 1* , Ali Baghaei 1 1 Department of Chemical Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, Iran 2 National Iranian Gas Company (NIGC), South Pars Gas Complex (SPGC), Asaluyeh, Iran Received: 2019-05-31 Revised: 2019-12-12 Accepted: 2018-12-21 Abstract: The release of hydrocarbon and toxic vapor from atmospheric storage tanks is considered as a hazardous phenomenon in the chemical and process industries. Most often, detailed meteorological data for a particular location are unavailable, making the application of Pasquill’s atmospheric stability table the only choice for running simulations. The simulation of the flammable and toxic vapor release and cloud dispersion in South Pars, Iran in the 4 th Gas plant incident in 2012, is run by applying the PHAST 6.53.1s/w. Meteorological data extracted from Pasquill's stability table. A simple methodology is developed for assessing land elevation difference between release source and gas detectors the obtained results are validated against time and location of recorded alarms in the site. The atmospheric parameters applied in this simulation are compared with wind speed and sky cloudiness data received from the Iranian meteorological institute. The Pasquill's parameters applied in this simulation are verified against local meteorological recorded data. The results indicate that if the vapor cloud is close to the earth's surface before any major change in the land elevation, this change can be neglected. Sensitivity analysis reveals that there will be fewer consequences if atmospheric discharge direction has a vertical upward orientation. keywords: Gas Dispersion; Storage Tank; Consequence Simulation; Gas Plant; Flammable and Toxic Gases 1. Introduction Process and chemical facilities like refineries and petrochemical plants are known as high- risk industrial plants (Arunraj, Maiti, 2009). One of the important factors in determining the scale of the potential accident in these facilities is the availability of hazardous materials in the equipment that could be released on an incident (Khan, Abbasi, 1999; Aliso et al., 2014). The storage tanks of crude oil, fuels like gasoline, natural gas condensate and tanks containing toxic substances are the riskiest sources in the process industries. According to (Lees, 1996; Khan, Abbasi, 1999), 3.3% of the reported explosions in chemical industry occur in tank farms. The main cause of 17.8% of inferno in the chemical plants and related industries are the flammable liquid and gas overflow/release (Norstrom, 1982; Khan, Abbasi, 1999). The gasoline storage tank fire and explosion of Buncefield, England, 2005, fuel storage tank facility fire in Puerto Rico, USA 2009, and oil depot fire in Jaipur, India, 2009, all with severe human, environmental and economic consequences are some of the latest events reported due to hydrocarbon release from storage tanks (Gant, Atkinson, 2011; Joyce et al., 2018). A toxic material release from storage vessels in Bhopal, India in 1984 is still the worst tragedy of chemical plants with the most severe consequences (Khan, Abbasi, 1998; Rad et al., 2017). Despite the advancing knowledge on safety and technology applied in the construction of such facilities, such incidents occur is inevitable, thus the question: Have the consequences of possible major accidents on storage tanks containing toxic/flammable materials, and vapor dispersion been simulated and evaluated correctly to allow appropriate precautions to be considered in the design and construction