A zero CO2 emissions large ship fuelled by an ammonia-hydrogen blend: Reaching the decarbonisation goals

To reach the decarbonisation goals, a zero CO2 emissions large ship propulsion system is proposed in this work. The ship selected is a large ferry propelled by an internal combustion engine fuelled by an ammonia-hydrogen blend. The only fuel loaded in the vessel will be ammonia. The hydrogen required for the combustion in the engine will be produced onboard employing ammonia decomposition. The heat required for this decomposition section will be supplied by using the hot flue gases of the combustion engine. To address the issues regarding NOx emissions, a selective catalytic reduction (SCR) reactor was designed. The main operating variables for all the equipment were computed for engine load values of 25%, 50%, 75%, and 100%. Considering the lowest SCR removal rate (91% at an engine load of 100%), the NOx emissions of the vessel were less than 0.5 g/kWh, lower than the IMO requirements. An energy analysis of the system proposed to transform ammonia into energy for shipping was conducted. The global energy and exergy efficiencies were 42.4% and 48.1%. In addition, an economic analysis of the system was performed. The total capital cost (CAPEX) for the system can be estimated at 8.66 Meuro (784 euro/kW) while the operating cost (OPEX) ranges between 210 euro/MWh (engine load 100%) and 243 euro/MWh (engine load of 25%). Finally, a sensitivity analysis for the price of ammonia was performed resulting in the feasibility of reducing the operating cost to below 150 euro/MWh in the near horizon.