Dispersion Modeling of Accidental Release of Propane and Butane: Case Studies of Some Locations in Lagos, Nigeria

This paper presents the study of the dispersion modeling of accidental release of propane and butane using three locations in Lagos as case studies. The first case scenario was an actual incident while the other two were hypothetical case scenarios. In this research work, the purpose is to predict and evaluate the dispersion behaviour of the accidental releases of propane and butane using the Areal Location of Hazardous Atmosphere (ALOHA) modeling software, developed and made freely available by the US Environmental Protection Agency (EPA), along with Google Earth Pro mapping software which is also freely available. The modelling approach is applied to three (3) different study areas in Lagos: Propane Tanker along Iju Ishaga Road, Butane Cylindrical Tank at ABC Refilling Plant along Ikorodu Road and Butane Spherical Storage Tank at XYZGas Terminal in Apapa. The overall modelling study is concentrated on three (3) different hazardous scenarios of interest – flammable area of vapour cloud, blast area from vapour cloud explosion (uncongested) and blast area from vapour cloud explosion (congested). The flammability (flash fire) and overpressure (blast force) hazards considered in this study were modeled using the aforementioned free software. Primarily, the threat zones generated by ALOHA for separate scenarios were mapped on their respective location maps in order to evaluate the location of the dispersion plumes. For the hypothetical release scenarios considered, the dispersion modeling results showed that the Case 3 (XYZGas LPG Terminal in Apapa) has the most impacted areas for the red, orange and yellow threat zones with respect to buildings, institutions, shops, companies, streets, roads, etc. For the first study area, the results predicted the reported impact of the damaging effects for the Scenario C release. For the second study area, the results show that no threat zones are generated for the uncongested overpressure of Secnario B release. The kind of analysis and results obtained from this study would prove beneficial to the emergency planners and responders such as Lagos State Emergency Response Agency specialized in these study areas to help minimize the impacts of these dangerous releases and plan for safety decisions and mitigation techniques to be implemented where appropriate.