Conceptual design and 4E analysis of an ammonia synthesis process integrating methane thermal decomposition and dual chemical looping

Ammonia has emerged as a promising hydrogen carrier and potential carbon-free fuel, increasing the demand for sustainable and energy-efficient production technologies. Conventional ammonia synthesis accounts for ∼1 %–2% of global energy use and 1 %–1.3 % of total greenhouse gas emissions, necessitating alternative approaches with lower environmental impacts. This study proposes an ammonia-production pathway that integrates methane thermal decomposition with a dual-chemical-looping system based on iron oxide (Fe₂O₃) and aluminum oxide (Al₂O₃). A comprehensive evaluation was conducted using energy, exergy, environmental, and economic (4E) analysis, benchmarked against conventional and single-looping processes. The results demonstrate that the proposed configuration improves the energy and exergy efficiencies by 8.4 % and 19.0 %, respectively, compared with conventional routes. Global warming potential was reduced by 15.85 kg CO₂-eq/kg NH₃. Furthermore, the levelized cost of ammonia decreased to 336.97 USD/t NH₃, representing a 60.9 % reduction. These enhancements are primarily attributed to the synergistic integration of thermal and material flows, along with valorization of the process byproducts. Sensitivity analyses verified the stability of the system performance under a range of technoeconomic conditions, including variations in carbon pricing, electricity costs, and hydrogen market dynamics. Overall, this study highlights the technical and economic viability of the dual chemical looping approach for low-emission ammonia production, offering a strategic alternative for transitioning toward sustainable energy systems.