Membrane separations, multistage efficiency

Multistep and multistage membrane systems of the type shown in Figure 21.5 have been used to treat a number of vapor-gas streams. However, hybrid processes in which membrane separation is combined with another separation process, are attractive because they may enable each unit operation to operate in its preferred range, improving overall process efficiency. The most important of these hybrid processes is the combination of condensation under pressure with membrane separation, illustrated in Figure 21.6. In this process, a vapor-permeable membrane unit is combined with a vapor condensation-flash unit (Baker and Wijmans, 1994 Baker et al., 1998 Wijmans, 1993/1992). 

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