Modeling of a solar steam reforming reactor

Chemical Energy Transmission Systems (GETS) are based on reversible endothermic and exothermic reactions. One of the essential tasks of a large scale solar energy utilization plant is the transmission of energy from the solar collector to the consumer. This can be accomplished through GETS, with a solar thermal process called SOLTHERM. In this process, the endothermic reaction product can be transported through pipelines to any destination, where the exothermic reverse reaction is made to proceed with the release of energy. The best reaction system for GETS is the endothermic methane-steam reforming reaction and the reverse exothermic methanation reaction. A two-dimensional pseudo-homogeneous model has been developed for a packed-bed methane-steam reforming reactor which uses a heat pipe as a flux transformer to distribute the heat collected by the solar receiver system to the chemically reacting system. This model is capable of obtaining temperature and conversion profiles and mole fractions of various system components at every length within the reactor. Various sensitivity studies are performed for variations in inlet gas temperature and inlet natural gas flow rate, Sensitivities to changes in the available rate equation and heat transfer correlations are evaluated. The effect of variations in the heat pipe temperature and inlet steam-methane ratio are also examined. Calculations are done to evaluate the minimum thermodynamic steam-methane molar ratio above which there is no risk of carbon formation, for various temperatures. This is combined with the predictions of the model to evaluate carbon formation potentials within the reactor for different inlet conditions. Operating conditions are suggested to avoid carbon formation.