Venting of Underground Storage Tanks Containing Ethanol-Gasoline Blends

Fugitive emissions of VOCs from gasoline marketing facilities are an energy, safety and environmental issue. All new vehicles made after the year 2000 must have an Onboard Refueling Vapor Recovery System (ORVR) which increase fugitive emissions of refueling stations because of interface between ORVR vehicles and gasoline station underground storage systems (UST). The increase of VOCs is attributed to ingestion of fresh air into the UST mixing with the gasoline causing an approximate 40% vapor growth. This growth increases UST pressure and vents VOCs into atmosphere. With recent federal initiatives for renewable energy, bio-ethanol may represent upwards of 30% of our fuel supply. Blending ethanol with gasoline would increase the evaporative emission of VOCs from UST as the vapor pressure of gasoline is elevated by the addition of ethanol. Further, ethanol absorbs water easily and water can cause ethanol to phase separate from gasoline. Therefore in any membrane venting process it is desirable for any water present to vent with the air and not stay with the fuel. Conventional VOC permeating membranes (silicone rubber) concentrate water and fuel together. This program develops a novel perfluoropolymer membrane that allows for rapid venting of air and water while retaining gasoline and ethanol in the UST. This membrane system will have chemical resistance to gasoline and ethanol and represent a simple single stage unit operation versus alternative technologies that are more complex.