Modeling the environmental, health, and safety aspects of xylene isomer emission from storage tanks in petrochemical industries, Iran

The release of xylene isomers from storage tanks poses a significant threat to petrochemical industries, and their safe transportation and storage is a widely researched topic. This paper focused on modeling the environmental, health, and safety effects of P-xylene and O-xylene leakage from storage tanks via Areal Locations of Hazardous Atmospheres (ALOHA) and Wireless Information System for Emergency Responders (WISER). The meteorological data of the area, characteristics of the tanks, and the roughness of the land surrounding the tanks were used to run the ALOHA model. The dispersion distances of P-xylene and O-xylene toxic and flammable vapor clouds were estimated according to the Immediately Dangerous to Life or Health (IDLH) and lower explosive limit (LEL) criteria. Also, the levels of thermal radiation due to the burning of P-xylene and O-xylene were estimated. The results showed that in the cold seasons, the IDLH was a maximum distance of 62 m and 45 m for P-xylene and O-xylene, respectively. The LEL criteria were 10% with a magnitude of 1100 ppm for a maximum distance of 54 m and 35 m for P-xylene and O-xylene, respectively. The maximum distance of 20 m for O-xylene based on the results of the LEL criteria of 60% (6600 ppm) was attained in the warm seasons. They are potentially lethal within 60 s at 21 m (10.0 kW/m²) when burned. The WISER software predicted the protective distance for xylene isomers to be about 300 m. The results show that creating a protective zone around the P-xylene and O-xylene tanks with a radius of 54 m is necessary to reduce hazards.