Power and Hydrogen Co-generation from Biogas

The present work investigates the implementation of molten carbonate fuel cells (MCFCs) for power generation from landfill biogas, coupled to the on-site production of hydrogen for vehicle-fueling purposes. The system modeling of the plant has been performed in steady-state conditions, with the aim of assessing the overall power efficiency. Because MCFCs are highly exothermic and their working temperatures (650 degrees C) are compatible to steam reforming, the syngas is produced directly inside the vessel containing the fuel cell stack, with the reaction being thermally self-sustained. Moreover, the high-temperature flue gases from the MCFC are expanded in a turbine, thus increasing the total power generated. Hydrogen is produced through a pressure swing adsorption system, whose feed can be from either the MCFC anode outlet or a split of the reformate before the anode inlet. The overall net power efficiency of the system is similar for both configurations, being 56 and 55%, respectively. However, other parameters apart from efficiency must be taken into account for the proper selection of the most suitable configuration, such as raw material consumption and system flexibility. The two options are evaluated and discussed on the basis of these considerations.