HIGH-TEMPERATURE CO SHIFT CONVERSION (HTSC) USING CATALYTIC MEMBRANE REACTORS

Models are developed for simulation of membrane reactors for the high temperature shift conversion of carbon monoxide (GO). Three configurat ions are considered in the analysis; the first employs a shell and tub e arrangement, where the catalyst is placed inside the tubes which hav e hydrogen-permeable walls. The second and third configurations make u se of an existing HTSC system plus membrane separation cells for remov al of hydrogen from the feed (second configuration) and from the feed and effluent reaction mixture leaving the first catalyst bed in the re actor (third configuration). For the first configuration, in situ reac tion and separation of hydrogen takes place. Accordingly, a shift from equilibrium occurs along the reactor length as a result of continuous removal of hydrogen present in the feed and formed during reaction. O n the other hand, a shift from equilibrium in the second and third con figurations relies on the use of separate membrane cells for hydrogen removal. CO conversions up to 0.99 are predicted in the first and thir d configurations which implies that the CO content in the effluent is below the maximum limit of 0.25 mole percent on a dry basis. Currently , this limit is achieved by use of both high and low temperature shift converters. This result suggests the possibility of the reconfigurati on of a conventional CO shift conversion system, where it is feasible, to eliminate the low temperature converter. Although both the first a nd third configurations meet the desired limit on CO content in the ef fluent, it is found that the amount of catalyst needed for the first c onfiguration is much larger (more than five times) than that of the th ird configuration.