Experimental study and thermodynamic assessment of a bypass-enabled ammonia-fueled SOFC system

초록

Ammonia is a promising hydrogen carrier for solid oxide fuel cell (SOFC) power generation, but practical system-level operation remains insufficiently understood because most previous studies have focused on cell/stack tests or simulation based system analysis. In this study, an integrated ammonia-fueled SOFC system was experimentally constructed and thermodynamically assessed under a representative self-heated operating condition. The system consisted of an SOFC stack, ammonia cracker, catalytic burner, heat exchangers, air blower, and a bypass-enabled fuel-supply line designed to accommodate both cracked and direct ammonia feeding. Temperature and pressure were measured at the major component inlets and outlets, electrical and blower power were recorded, and exhaust NOx was monitored. Stream compositions were estimated using mass balance equations based on measured flow rates and reaction stoichiometry. The system gener-ated 1368.78 W of stack DC power and 1284.2 W of net power, corresponding to stack and system efficiencies of 58.70% and 55.07%, respectively. NOx emission was below the detection limits of the analyzer during the tested operating condition. Component-level energy and exergy analyses revealed that the cracker and burner unit was the dominant source of irreversibility, with an exergy destruction of 525.4 W, exceeding that of the SOFC stack at 309.5 W. In addition, the measured state points revealed nonnegligible hot box heat redistribution, including apparent heat gains in connecting streams, demonstrating that actual system behavior cannot be fully captured by simple component-wise heat loss assumptions. The results show that ammonia conversion and hot box thermal integration are key improvement targets for practical ammonia-fueled SOFC systems.

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