Modeling the Transient Response of Heat Exchange Reformers

AIChE shall not be responsible for statements or opinions contained in papers or printed in its publications. One method of producing hydrogen for fuels cells is the steam reforming of conventional hydrocarbons, an established refinery process. It has been proposed to carry out this process in a heat exchange reformer – a reformer that has a flow configuration analogous to a heat exchanger. The catalyst, in the form of a conventional pellet, is usually placed in the tubes of the reformer and a hot gas (i.e. from a combustor) or effluent from another process is circulated in the shell side. Key design objectives of the Heat Exchange Reformer are a high, steady state, thermal efficiency and a compact unit both in volume and mass. It is well known that many applications of fuel cells require transient operation which requires that the production of hydrogen rich feed also varies. Otherwise excess hydrogen is generated and not consumed, leading to a significant loss in overall energy efficiency. The implication is that the transient response of the heat exchange reformer also needs to be considered in its design. In this work, the transient response of a simplified heat exchange reformer is modeled. The geometry of the reformer is two concentric cylinders, filled with conventional pellet catalyst, a common design element in many heat exchang