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Abstract

The cyclic water gas-shift reactor (CWGSR) is an alternative to the sequence of water gas shift reactors for the removal of carbon monoxide from reformate gases. It is based on the alternating reduction of a fixed bed of iron oxide using reformate gas and the subsequent re-oxidation of the iron with steam (Fig. 1). The gaseous product during the oxidation phase is a mixture of hydrogen and steam, which can be used in low temperature fuel cells.
In our contribution, we will present various results that are essential for the development of the CWGSR. With regard to the fixed bed material, we have developed a suitable mixture of metal oxides which combines high oxygen capacity, high catalytic activity and good stability properties. To validate the reactor concept experimentally, a tubular fixed bed reactor has been applied. It shows that the reactions occur in reaction zones which travel slowly through the reactor (Fig. 2). Their breakthrough behavior dominates the reactor dynamics. Based on these experimental results, we demonstrate a mathematical model for the detailed design of the reactor and show some results of a study that evaluates the performance of the CWGSR in systems employing PEMFCs or SOFCs or a combination of both against systems with conventional shift reactors.