Abstract

In the present study, the researchers used an integrated approach composed of response surface analysis (RSM) and MPACT model to predict fatality rates caused by benzene emitted from floating-roof tanks. RSM scenarios were configured in Expert Design (version 7.0) software using the central composite design (CCD) method and five variables of wind speed, relative humidity, atmospheric temperature, failure diameter, and emission height were considered. Continuous Pasquill–Gifford Gaussian model was used to estimate the results of the RSM scenarios. The response values were considered for exposure concentrations above 50 ppm (slight damages), 150 ppm (moderate damage), and 1000 ppm (high damage). The analysis of individual and social risks for each scenario was done using the MPACT model in SAFETI program (version 8.22) by providing two variables of population characteristics and the frequency of tank wall failure. The results showed that atmospheric temperature, wind speed, failure diameter, and emission height have positive effects on the dispersion of the cloud of toxic benzene vapor with a concentration of 1000 ppm. Intolerable individual risk distances were estimated to be lower for indoor environments than for outdoor. Maximum distances of intolerable individual risks for the worst-case scenarios were estimated up to 2500 m from the emission point, which resulted from exposure to a concentration of 1000-ppm benzene. Results regarding the estimation of social risks showed that over 1600 fatalities should be expected under the worst-case scenarios. The three factors of high temperature, low wind speed, and low emission height play a major role in the occurrence of scenarios with the highest fatalities. High wind speed and high emission height were the most important factors in most scenarios with zero fatalities rate. Generally, the findings of this study show the necessity to provide an emergency response plan in the studied industry in both autumn and winter due to low wind speed. However, the coupling of the developed statistical models based on regional meteorological conditions with the MPACT model can help researchers to design an emergency response plan to deal with leakage incidents in petrochemical industries.

Introduction

The introduction outlines the growing concern about chemical emissions, particularly benzene, from petrochemical storage tanks. It reviews past chemical accidents, emphasizes the risks of toxic vapor dispersion, and highlights the need for proactive risk assessment. The authors identify limitations in previous studies and justify the use of response surface methodology (RSM) and the MPACT model for a more accurate risk analysis.

Materials and Methods

This section explains the characteristics of benzene and the petrochemical facility under study. It describes how five variables (wind speed, temperature, failure diameter, emission height, and humidity) were modeled using central composite design (CCD) in RSM. The SAFETI software and MPACT model were used to simulate benzene dispersion and assess individual and social risks under different scenarios.

Results and Discussion

The results show how each variable influences the dispersion of benzene vapor clouds and the extent of individual and social risk zones. The study found that higher temperature and lower wind speed increase the danger zone. Several worst-case scenarios are identified, with potential fatalities exceeding 1,600 people in some cases. Statistical models are validated, and the results emphasize the importance of emission height and wind conditions.

Conclusions

The study concludes that benzene emissions from storage tanks pose serious risks to both workers and surrounding populations. It stresses the value of combining meteorological modeling and statistical analysis to predict toxic dispersion. Emergency response plans should prioritize low-wind periods, especially in autumn and winter, to minimize risk.