Modeling of the GHG Reduction Potential of NH3 Dual-fuel Engines with Tailored Exhaust Gas Aftertreatment

Abstract The decarbonization of maritime transport necessitates the adoption of carbon-free fuels, with ammonia (NH₃) emerging as a promising candidate. However, its incomplete combustion, resulting in unburnt NH 3 , and the formation of nitrogen oxides (NOₓ) and nitrous oxide (N₂O), a potent greenhouse gas (GHG), pose significant challenges for emission control. To address these challenges, experimental kinetic data of Fe-BEA, Co-based, and Pt-based catalysts are incorporated into physico-chemical models. Model validation against the experimental data confirms the accurate prediction of NH₃, NOₓ, and N₂O conversion trends. The model is subsequently employed to design and optimize the Exhaust Aftertreatment System (EATS) layouts, including Selective Catalytic Reduction (SCR), SCR with Ammonia Slip Catalyst (ASC), and hybrid Co–Pt ASC configurations, across a range of engine-out NH₃/NOₓ ratios and combustion efficiencies. The results demonstrate that while NOₓ and NH₃ emissions can be effectively mitigated, N₂O formation in ASC-equipped systems constrains total GHG reduction to approximately 76% compared to conventional diesel operation. A hybrid ASC configuration combining Co and Pt catalysts successfully reduced N₂O selectivity, achieving up to 50% additional GHG reduction.