CFD-guided catalytic combustion optimization of CH4/H2/NH3 blends using staged Ni-based catalysts: Insights into NOx mitigation and efficiency enhancement

The decarbonization of industrial combustion systems demands fuel strategies that reduce greenhouse gas emissions while maintaining high efficiency and operational stability. This study explores the catalytic combustion behavior of ternary CH 4 /H 2 /NH 3 fuel blends using high-fidelity Large Eddy Simulation (LES) integrated with a validated reduced chemical mechanism (51 species, 420 reactions). The focus is to overcome ammonia's inherent limitations: low reactivity, high ignition temperature (> 650 °C), and elevated NO x formation, by leveraging catalytic surface interactions. A novel staged catalyst configuration based on Ni-Cu/Fe 2 O 3 is proposed, with upstream NH 3 decomposition and downstream NO x reduction zones. Parametric simulations reveal that a 30:30:40 volumetric fuel blend (CH 4 :H 2 :NH 3 ) achieves optimal performance, yielding combustion efficiency above 97 %, NO x emissions below 30 ppm, and NH 3 slip under 15 ppm. Catalyst staging improves performance over uniform coating, reducing NO x by 79.3 % and NH 3 slip by 56.1 %. Stability maps indicate extended flame anchoring over a wide equivalence ratio range (0.65–1.1) and inlet velocities up to 25 m/s. A comprehensive reaction pathway analysis attributes 65 % of NO x to fuel NO, 25 % to thermal NO, and 10 % to prompt NO mechanisms. Catalytic activity proves most effective within the 550–650 K surface temperature window. The results highlight a scalable pathway for integrating catalytic combustion in low-carbon energy systems and establish a foundation for future experimental validation. This work offers practical insight for transitioning toward cleaner combustion technologies, particularly in ammonia-assisted hybrid fuels for advanced burners, reformers, and industrial heating applications. • LES of CH₄/H₂/NH₃ blends with Ni–Cu/Fe₂O₃ catalysts for catalytic combustion. • Staged catalyst reduces NOₓ by 79 % and NH₃ slip by 56 % vs. uniform coating. • Optimal 30:30:40 fuel blend gives 97 % efficiency, NOₓ <30 ppm, NH₃ slip <15 ppm. • Stable flame achieved for φ = 0.65–1.1 and inlet velocity up to 25 m/s. • Pathway analysis: 65 % fuel NO, 25 % thermal NO, 10 % prompt NO formation.