Engineering Aspects of the Plant Design to Separate Volatile Hydrocarbons by Vapor Permeation

The paper deals with engineering aspects of the design of membrane systems for the separation and recovery of volatile hydrocarbons from off-gases. The membrane which is used for this application is a thin film composite membrane with an elastomeric selective top layer. This membrane has a high permeability for various hydrocarbon vapors and a low permeability for oxygen and nitrogen. The membrane configuration is a flat sheet membrane manufactured to an envelope with a round shape which is installed in the so-called GS module. The energy impact in accordance with the condensation mode and operating pressures is shown. Case studies on the influence of different process parameters, e.g., plant capacity, recovery rate, pressure ratio, stage cut and retentate concentration were carried out on the basis of given feed compressor and vacuum pump capacities. Finally, the investment costs of vapor recovery units in gasoline tank farms are discussed.