Chapter 19: New Metrics in Membrane Gas Separation

In this chapter, the potentialities of the membrane gas separation applications will be analyzed by introducing some new metrics specific for the GS field. Moreover, some guidelines useful for the identification of the separation processes most suitable for obtaining a specific product target also in dependence of the feed stream conditions will be proposed and discussed.

The hydrogen separation from refinery streams will be considered as case study so that proposing a comparison between the conventional separation operations, such as adsorption, absorption and cryogenic and the membrane GS, in terms of the productivity/size ratio, mass intensity and energy intensity. Some experimental results obtained using polyimide membranes will be also shown as an example to demonstrate how to use these metrics for real cases. Moreover, some further considerations related to the exergetic aspects to take into account in the process design phase will be highlighted considering the ethylene production cycle as a case study.