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Activated Carbon for Automotive Applications

1999; Elsevier BV; Linguagem: Inglês

10.1016/b978-008042683-9/50010-8

Philip J. Johnson, David J. Setsuda, R.S. Williams,

Atmospheric chemistry and aerosols

The generation of air pollutants, including volatile organic compounds (VOCs), from automotive vehicles was identified to come from two principal sources—vehicle exhaust emissions, and fuel system evaporative emissions. Evaporative emissions are defined as the automotive fuel vapors generated and released from the vehicle's fuel system because of the interactions of the specific fuel in use, the fuel system characteristics, and environmental factors. This chapter discusses the sources of evaporative emission. The application of activated carbon technology in automotive systems focuses on the control of evaporative emissions. Automotive evaporative emissions have been identified as a source of hydrocarbon (HC) compounds that can contribute to smog pollution. Both the environmental protection agency (EPA) and California Air Resource Board (CARB) have established regulations defining the levels of evaporative emissions that can be tolerated. These agencies have developed specific test procedures, which must be used to verify compliance with the established limits. The current requirements have led to the development of pellet shaped activated carbon products specifically for automotive applications. The adsorption of hydrocarbons by activated carbon is characterized by the development of adsorption isotherms, adsorption mass and energy balances, and dynamic adsorption zone flow through a fixed bed. A vehicle fuel vapor control system must be designed to meet both driving and refueling emission level requirements. Due to the nature of hydrocarbon adsorption, this emission control is a continuous operation. The reduced adsorption capacity at Onboard Refueling Vapor Recovery (ORVR) vapor generation rates requires increased efficiency in the canister design, in order to limit the effect on cost and performance of the evaporative control system.