Recovery of solid oxide fuel cell waste heat for hydrogen release from liquid organic hydrogen carriers
Stefan Pappler, Tobias Mader, Marco Blasius, Timo Gräser, Timo Rüde, Michael Geißelbrecht, Antje Seitz, Stefanie Wahl, Peter Wasserscheid
Abstract
This study deals with a new technology for off-grid power supply that combines endothermal hydrogen release from liquid organic hydrogen carriers (LOHC) with waste heat recovery from a solid oxide fuel cell (SOFC) system. Our work is based on a pre-commercial SOFC system developed for power and heat supply from natural gas, hydrogen or mixtures thereof. Three research needs for a better integration of SOFC waste heat into a hot gas-heated hydrogen provision from the LOHC compound perhydro benzyltoluene (H12-BT) were identified: i) The applied configuration of the precommercial SOFC unit provides its exhaust gas at too low temperature; ii) There is a lack of detailed knowledge about the heat transfer characteristics in gas-heated LOHC dehydrogenation units; iii) For the use of CH 4 /H 2 gas mixtures as fuel for the SOFC system, the thermodynamic potential of using CH 4 as purge gas in the LOHC dehydrogenation process has not yet been explored. In this study, we address these three aspects by redesigning the internal heat recovery system of the SOFC system for increasing the temperature level of the waste heat stream to 400 °C. We demonstrate experimental results from a hot air-heated H12-BT dehydrogenation unit operating with and without CH 4 purge gas and take the additional waste heat production from the H 2 /CH 4 co-fueling into account. Overall, our findings show a significant technical potential for combining SOFC operation with hydrogen provision from LOHC systems without auxiliary heating (except for start-up).