| Summary: | 碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 90 === Recently, the number of gasoline station is increased due to the strategy of government’s oil open market recently. Based upon the consideration of business, most of the gas stations are located at the crossroad with a heavy traffic or the district with a dense population. To bring more convenient to all people and obtain more revenue, therefore the neighborhood of gasoline stations, although they obtain some convenience, it is worthy to concern the public safety and healthy due to the air pollution from these gasoline stations. In addition, based on the statistical database of 1990, the total volatile organic compounds (VOCs) emissions from domestic gasoline stations is reach to 11,938 tons per year, approximate 7% of total VOCs emissions from stationary source. According to the above mentioned, this study plan to proceed the measurement of the VOCs concentration in ambient air at the gasoline station and released gasoline vapor from dispensing pistols during refueling period to understand the diffusive characteristics of VOCs. Furthermore, to better understand the compositions and characteristics of gasoline vapor inside the fuel tank, this study use steeliness canister simulate supplier of Chinese Petroleum Corporation (CPC) and Formosa Petroleum Corporation (FPC). By using different photochemical reactivity indication, such as maximum increased reaction (MIR), Propyl-Equivalent concentration (PEC) and photochemical ozone creation potential index (POCP), then the ozone formation potential of CPC and FPC can be estimated. Expected that these research results could be referred to revise the strategy of controlled VOCs emissions.
The results conducted in this study found that the concentrations of NMHC, MTBE and BTEX were affected strongly by the wind speed at ambient of gasoline station. While the wind speed is faster (station 1: average wind speed is 4.6 m/sec) and because of the released pollution concentrations are diluted into atmosphere, the measured concentration value of NMHC is lower (the concentration of NMHC between 0.5 ~ 1 ppm). When the wind speed is the lowest (station 3: average wind speed is 0.6 m/sec), the measured concentration of NMHC is the highest in pump island. It indicates that the gasoline dispensing pistols at the pump island is the major emission source of VOCs pollution. The concentration of toluene is the highest from the released MTBE and BTEX.
In measurement of gasoline dispensing pistols, the concentration of released gasoline vapor for unleaded gasoline 95 (average concentration is 4,110 ppm) is largest of all gasoline grades; the next is unleaded gasoline 92 (average concentration is 3,811 ppm). Totally, the concentration of released gasoline vapor without vapor recovery systems is 5 times higher than the equipment which have with vapor recovery systems. Practically, the results show the equipment with vapor recovery systems could reduce 80% gasoline vapor released to environment. Besides that, this study also discoveries that the tight contact between the gasoline dispensing pistols and the fuel tank would reduce the released level of gasoline vapor via research results during sampling procedure.
Simulation on composition and characteristics of gasoline vapor inside the fuel tank under temperature 20 to 35℃, based upon the 38 kinds of target compounds, the average released concentration of CPC (317 ± 141 mg/L ) is higher than the gasoline vapor by FPC ( average released concentration is 292 ± 168 mg/L). Comparison of the released alkanes, alkenes and aromatics characteristics for the same gasoline vapor, we found that the concentration of alkanes is the highest, and its average concentration is occupy 70% of the gasoline vapor and is higher than alkenes by 2 to 3 times. The released time of aromatics is very slow compared to alkanes and alkenes due to its large molecular. Its released concentration is increased with increased measurement time. In reaction properties of ozone photochemical focus on assessment of ozone formation potential via MIR and PEC, the offer amounts of FPC (ozone formation potential for MIR and PEC are 901 mg/L and 134 mg/L) for ozone formation potential are greater than CPC ones (ozone formation potential for MIR and PEC are 807 mg/L and 115 mg/L). However, the POCP is opposite to the above two index. Totally, the POCP of CPC (23,576 mg/L) is greater than FPC (22546 mg/L).
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