Energy and exergy analyses of dual refrigerant system for liquefaction of natural gas

Abstract

Present study proceeds thermodynamic modelling, and analysis of dual refrigerant system for liquefaction of natural gas (LNG) that is one of the most important technologies in producing LNG. Using energy equations pressure, quality, enthalpy, entropy of natural gas and two refrigerants, i.e., methane and propane are specified. The effects of different cycle variables on the thermodynamic performance especially the coefficient of performance (COP) is studied. Using the second law of thermodynamic for the system components, the exergy destruction rates has been found. The exergy analysis results show that heat exchanger I (HX I), heat exchanger II (HX II) and turbine have the highest exergy destruction rate. Furthermore, results indicate that the total exergy destruction rate of studied cycle for generation of 1 kg/s LNG is 2,996 kW. Moreover, energy and exergy analysis show that important parameters such as propane mass flow rate has different effects on the COP and exergy destruction rate.