(626e) Staged Membrane Systems for Hydrogen Recovery from H2/CO2 Mixtures

Steam reforming of various hydrocarbon feeds is the primary source of industrial hydrogen. The reforming process produces a stream containing primarily hydrogen and carbon dioxide which requires subsequent purification.

A variety of membrane separation processes are being considered for this separation. This work addresses the potential of polymeric membranes for hydrogen recovery. For most binary gas pairs, polymeric materials permeate one species preferentially over the over. However, for hydrogen-carbon dioxide materials are available that are selective for either hydrogen or carbon dioxide.

One may envision a number of different staging configurations based on these materials. For example, four different two-stage configurations exist in which each stage permeates either hydrogen or carbon dioxide. Moreover, one could use a single stage in which both types of membranes are intermingled ? an internally staged configuration.

The performance of these configurations is evaluated theoretically for recovering 90% of the hydrogen from a gas stream containing 40%-60% hydrogen. The internally staged configuration produces the highest purity product. However, a two-stage configuration in which each stage preferentially permeates hydrogen performs nearly as well. Moreover, this two-stage design does not utilize inter-stage compression ? the permeate pressure is reduced in two steps to its final, lowest value. The results are used to evaluate the economics of hydrogen recovery with polymeric membranes.