Novel onboard ammonia cracker for light-duty automotive fuel cell vehicles†

Abstract

This work introduces an innovative onboard ammonia cracker module integrated with a 100-kW fuel cell system for light-duty automotive fuel cell vehicles. Utilizing a hollow fibre palladium membrane reactor (HFMR), two configurations are explored: a 3 × 3 simultaneous heating and cracking module and a 4 × 4 intermediate heating and cracking module. The 3 × 3 module, arranged in a serpentine configuration, exhibits superior performance with a calculated required volume of 8.9 liters, a total module area of 1.2 m² and a process thermal efficiency of 93.5%. Each reactor in this module operates isothermally at an exit temperature of 475 °C, achieving ammonia conversion rates that increase from 15.8% in the first reactor (R1) to an impressive 99.99% in the final reactor (R8), facilitated by in situ hydrogen removal through the palladium membrane. The steady-state analysis was carried out using Aspen Plus Software, and validated against experimental data from existing literature. The results demonstrated a high degree of agreement, confirming the model's capability to accurately predict system performance. For transient analysis, Aspen Plus Dynamics was employed to assess the system's responsiveness to varying driving conditions. Utilizing the Hyundai Nexo fuel cell car as a case study, the worldwide harmonised light vehicle test procedure (WLTP) was simulated, to model realistic driving cycles, allowing for a rigorous interrogation of the transient performance of the on-board ammonia cracker. Overall, this research establishes a 3 × 3 simultaneous heating and cracking HFMR module as the optimal configuration for on-board ammonia cracking for hydrogen production in fuel-cell vehicles, highlighting its operational efficiency and potential contribution to sustainable transportation solutions. Future research should focus on optimizing heat management and temperature control within the HFMR module, as well as enhancing transient response characteristics and ammonia safety, to boost system performance and support the wider implementation of hydrogen technologies in the automotive industry.