Analysis of Chlorine Gas Incident Simulation and Dispersion Within a Complex and Populated Urban Area Via Computation Fluid Dynamics

Document Type: Research Paper


1 Iranian Research Organization for Science and Technology - Chemical Technology Department

2 Department of Energy Engineering, Politecnico di Milano, Italy


In some instances, it is inevitable that large amounts of potentially hazardous chemicals like chlorine gas are stored and used in facilities in densely populated areas. In such cases, all safety issues must be carefully considered. To reach this goal, it is important to have accurate information concerning chlorine gas behaviors and how it is dispersed in dense urban areas. Furthermore, maintaining adequate air movement and the ability to purge ambient from potential toxic and dangerous chemicals like chlorine gas could be helpful. These are among the most important actions to be taken toward the improvement of safety in a big metropolis like Tehran. This paper investigates and analyzes chlorine gas leakage scenarios, including its dispersion and natural air ventilation  effects on how it might be geographically spread in a city, using computational  fluid dynamic (CFD). Simulations of possible hazardous events and solutions for preventing or reducing their probability are presented to gain a better insight into the incidents. These investigations are done by considering hypothetical scenarios which consist of chlorine gas leakages from pipelines or storage tanks under different conditions. These CFD simulation results are used to investigate and analyze chlorine gas behaviors, dispersion, distribution, accumulation, and other possible hazards by means of a simplified CAD model of an urban area near a water-treatment facility. Possible hazards as well as some prevention and post incident solutions are also suggested.


Main Subjects

[1] Lisi, R., Maschio, G., Milazzo, M. F. (2007). Terrorist actions in the transport of dangerous goods in urban
areas. In IChemE symposium series (No.153).

[2] Maschio, G., Milazzo, M. F. (2008). Risk evaluation of terrorist attacks against chemical facilities and transport systems in urban areas. In Resilience of Cities to Terrorist and other Threats (pp. 37-53). Springer Netherlands.

[3] Alalam News Network. (2014, June 13). News. Retrieved from Alalam News Network:

[4] The New York Times. (2007, February 22). World News. Retrieved from The New York Times:

[5] Tehran Province Water and Wastewater. (2014). News and event. Retrieved from Tehran Province Water and Wastewater:

[6] Gavelli, F., Bullister, E.,  Kytomaa, H. (2008). Application of CFD (Fluent) to LNG spills into geometrically complex environments. Journal of hazardous materials, 159(1), 158-168.

[7] Freeman, M., Spencer, R.,  Huber, A. (2013). Scientific Visualization for Micro-Scale Modeling of Airborne Pollution in Urban Areas.EPA. 

[8] Kashi, E., Shahraki, F., Rashtchian, D., Behzadmehr, A.(2009). Effects of vertical temperature gradient on heavy gas dispersion in build up area. Iranian journal of chemical engineering, 6(3), 26-45.

[9] Jam e Jam. (2012 Dec 16). Poisioned students with Chlorine in the swimming pool ( in persian). Retrieved from

[10] FardaNews. (2012, Jan 25). 11 Injured in Chlrone gas incident in Hootan Swimming pool in Tehran. Retrieved from

[11] Dunning, A., & Oswalt, J. (2015). Train wreck and chlorine spill in Graniteville, South Carolina: Transportation effects and lessons in small-town capacity for no-notice evacuation. Transportation Research Record: Journal of the transportation research board, 130-135.

[12] Dandrieux, A., Dimbour, J. P., & Dusserre, G. (2006). Are dispersion models suitable for simulating small gaseous chlorine releases?. Journal of loss prevention in the process industries, 19 (6), 683-689.

[13] Hanna, S. R., Hansen, O. R., Ichard, M., Strimaitis, D.(2009). CFD model simulation of dispersion from chlorine railcar releases in industrial and urban areas. A tmospheric environment, 43 (2),262-270.

[14] Gilfrin, P., Hatfield, E. (2005). Visualizing Sheffield 58 E. Kashi et al. / Advances in Environmental Technology 1 (2015) 49-58 City Hall Airflow. AEC Magazine, 23, 25-26.

[15] Qiao, A., Zhang, S. (2010). Advanced CFD modeling on vapor dispersion and vapor cloud explosion. Journal of loss prevention in the process industries, 23(6), 843848.

[16] World Weather. (2014). Tehran Monthly Climate Average. Retrieved from ttp://

[17] Info. (2010). Tehran City Information. Retrieved from. Retrieved from

[18] Municipality. (2012). Retrieved from

[19] Wolfram. (2014). average wind speed in Tehran.Retrieved from

[20] International Association of Oil and Gas Producers. (March 2010). Risk Assessment Data Directory; Consequence modelling. OGP.

[21] NORSOK Standard. (2001). Risk and emergency preparedness analysis. Norwegian Technology Standards Institution, Oslo, Norway.

[22] Chien, K. Y. (1982). Predictions of channel and boundary-layer flows with a low-Reynolds-number turbulence model. AIAA journal, 20(1), 33-38.

[23] Hoi, Y., Woodward, S. H., Kim, M., Taulbee, D. B., Meng, H. (2006). Validation of CFD simulations of cerebral aneurysms with implication of geometric variations. Journal of biomechanical engineering, 128(6), 844-851.

[24] Mirzaei, P. A., Haghighat, F. (2012). A procedure to quantify the impact of mitigation techniques on the urban ventilation.Building and environment, 47, 410-420.

[25] Carruthers, D. (2003). Handbook of Atmospheric Science:Principles and Applications.Blackwell.

[26] PBS. (2012). Inside Al Qaeda. PBS. Retrieved from