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304 Membranes, Synthetic, Applications
FIGURE 14 Hydrogen recovery scheme in ammonia synthesis. [From R. Rautenbach and R. Albrecht (1985). Chem.-
Ing.-Tech. 57, 119–130.]
membranes to offer membrane systems for smaller users,
and have successfully engineered hybrid cryogenic and
PSA systems, which include membranes as an integral
component. Figure 16 illustrates the complementary roles
of different nitrogen- and oxygen-producing technologies
for different purity and capacity requirements.
A commercial nitrogen enrichment system is illustrated
in Fig. 17. Hollow-fiber membrane modules are connected
to a compressed air feed at 70–150 psi. The feed in usually
to the bore side of the hollow fibers. Oxygen (and water va-
por that may be present) permeate out of the fiber into the
FIGURE 15 Hydrogen recovery scheme in methanol synthesis. shell and exit at low pressure. Dry, nitrogen-enriched air