Assessment of Pollutant Dispersion in Emergency Scenarios at an Oil Terminal: A Case Study Using the ALOHA Model

Abstract

This study assesses pollutant dispersion and associated safety impacts resulting from kerosene leakage at oil terminal facilities located in Bangkok and Samut Prakan, Thailand, using the ALOHA (Areal Locations of Hazardous Atmospheres) software to simulate vapor dispersion and fire scenarios. The assessment focused on evaluating the hazard distances of the Flammable Area of Vapor Cloud, Toxic Threat Zone, and Thermal Radiation from Pool Fire under different meteorological conditions. A total of ten simulation scenarios were simulated, consisting of seven scenarios in Bangkok (Scenario 1.1–1.7) and three scenarios in Samut Prakan (Scenario 2.1–2.3).

The results suggest that the flammable vapor cloud area remained relatively constant across all scenarios, hazard distances of approximately 22 m in Bangkok and 23 m in Samut Prakan. This finding suggests that kerosene has a low evaporation rate, causing the flammable vapor cloud to remain confined near the leakage source within the bund wall area and to be minimally influenced by meteorological conditions.

For the Toxic Threat Zone, Samut Prakan exhibited significantly greater impact distances than Bangkok. The AEGL-1 distances ranged from 55–60 m and AEGL-2 distances ranged from 24–26 m in Samut Prakan, whereas Bangkok showed AEGL-1 distances of 33–37 m and AEGL-2 distances of 22–23 m. These differences may be explained by the larger fuel storage capacity, larger tank dimensions, and greater containment areas in Samut Prakan, which may have promoted higher evaporation and vapor accumulation in the atmosphere.  

The assessment of Thermal Radiation from Pool Fire revealed substantially larger impact distances in Samut Prakan compared with Bangkok. Thermal radiation distances at 10 kW/m² were approximately 95–96 m in Samut Prakan and 63–64 m in Bangkok. At 5 kW/m², the distances were approximately 134–135 m in Samut Prakan and 90–91 m in Bangkok, while at 2 kW/m², the distances were approximately 208–210 m in Samut Prakan and 140–142 m in Bangkok. These results suggest that Thermal Radiation from Pool Fire may represents the most extensive hazard compared with the Flammable Area of Vapor Cloud and Toxic Threat Zone.

Overall, Samut Prakan exhibited greater hazard distances for all parameters than Bangkok, which may be associated with its larger storage tanks, greater fuel inventory, and larger containment areas, potentially resulting in larger fuel puddles and higher vapor generation. The findings also suggest that the dispersion behavior of kerosene in this study may resemble quasi-heavy gas behavior which may cause vapor clouds to accumulate near ground level and generate hazards primarily within the near-field region close to the leakage source. In contrast, the dominant hazard associated with the incident was Thermal Radiation from Pool Fire, which produced the widest impact area.