Simulation-Based Analysis of the Effects of Alternative Fuel Properties on the Operating Characteristics of Marine Fuel Supply Systems

Existing liquefied petroleum gas (LPG) fuel supply systems are considered for conversion to alternative marine fuels, but the effects of fuel properties on their operating conditions have not been quantified. This study determined how the operating conditions and equipment loads of an existing 200 kW-class LPG fuel supply system change when ammonia, methanol or ethanol is used. With the system configuration kept the same, steady-state simulations were performed with Aspen HYSYS, and the model was compared with operating data of the system with LPG. Under the LPG operating conditions, ammonia did not remain liquid at the high-pressure pump suction (vapor fraction 0.935); raising the low-pressure section from 10 to 11 barg kept it liquid with a pressure margin of 0.57 bar. Methanol and ethanol remained liquid even at a service tank pressure of 2 barg. The pump power scaled with the reciprocal of the liquid density and the heat duties with the liquid heat capacity; the heat duties of ammonia were 1.7–2.1 times those of LPG at equal mass flow rate and 1.6–2.4 times at equal heat input. Similar vapor pressures therefore do not guarantee phase stability, and the results provide property-based guidelines for fuel conversion.