Assessment and modeling of Styrene and acrylonitrile in ABS unit of Tabriz Petrochemical Complex

Abstract

Introduction: The use of air pollution dispersing models are necessary to predict and estimate the rates of emission and patterns of dispersion to manage and decision making regarding air pollution controlling programs. Styrene (STM) and Acrylonitrile (ACN) are two major components in the streams of ABS plant of Tabriz Petrochemical Complex which is expected to be released to the atmosphere through various sources such as equipment leaks and tanks venting. This study was carried out to estimate the emission rates and predict patterns of dispersion of mentioned pollutants around an ABS plant in Tabriz petrochemical complex. Materials and methods: The major sources of air emissions in the ABS plant were identified using the study of PFD and P&ID documents of the plant and also several site visits. Then the emission rates from pumps and copmressors were estimated using the emission factors presented by USEPA. TANKS model was applied to estimate of emission rates from tanks and also Water9 model was used to estimte emission rates from the wastewater treatment palnt of ABS manufacture unit. In the last step, the estimated emission rates with meterlogical parametrs were used as the input of Industrial Source Complex Short-Term Version 3 (ISCST3) and AERMOD models to predict the ground level concentration of STM and ACN around the ABS plant. A GPS was used to locate the emission sources. Results: The results showed that the maximum level of STM was 646 µg/m3 which is below the Reference Concentration (Rfc). In the case of ACN the maximum level of estimated concentration was 272 µg/m3 which is higher than Rfc. Investigation of emission rates indicated that compressors, pumps and tanks have significant role in emission of pollutants, respectively. The concentration distribution profiles of ACN and STM resulted from AERMOD model indicted that the concentration of STM was lower than EPA Reference Concentration (RfC) however, the higher concentration of ACN (higher than Rfc) occurred nearII the WWTP as well as the neighbor ambient. The results showed that for differnet average times, the maximum concentration of ACN was higher than STM which is due to higher emission rate of ACN in comparion with STM. The disperssion patterns of pollutants indicated that maximum 1 hr average of ACN and STM were 1233 and 574 µg/m3 repectively. Conclusion: The existence of ACN and STM around the ABS plant and exposure of workers to these pollutants can lead to negative effects on respiratory and neurological systems of persons and also can cause cancer. So this is important that appropriate measures be considered to reduce air emission from the differnt emission sources of ABS plant such as WWTP, pumps, comperresors, tanks and etc.