(596h) Self-Sustained Hydrogen Production from Ammonia Decomposition

Ammonia is a promising carbon-free energy carrier that will enable safe and viable use of hydrogen as a clean and efficient energy source. A self-sustained system for hydrogen production from the thermal decomposition of ammonia with a catalyst is highly required in the countryside, remote or emergency areas where external heat is hardly supplied. Herein, a self-sustained, compact reactor for ammonia decomposition was fabricated to provide a continuous production of hydrogen. Once initiated, the system is fed only with pure ammonia that is fully decomposed by a Ru-based catalyst to hydrogen and nitrogen gas mixture (75% H₂ and 25% N₂). Part of the decomposition product is mixed with air and fed back to the reactor where hydrogen is catalytically oxidized in an optimized palladium hydrogen burner, providing the required energy for ammonia decomposition. Different configurations of the palladium catalyst were investigated to provide a uniform heat distribution in ammonia catalyst bed and a fast drainage of the produced water vapor. Self-sustained ammonia decomposition was successfully demonstrated for more than 6 h, with approximately 72% of the produced hydrogen recoverable, compared to the maximum of 80% predicted by ASPEN HYSY. Steady state operation revealed negligible NO_X concentrations in the exhaust. Ammonia preheating and reactor insulation greatly affected ammonia decomposition efficiency. This research work will provide insights into the development of self-sustaining ammonia decomposition systems equipped with hydrogen selective membranes for pure hydrogen extraction.