Energy, exergy and economic analysis of offshore regasification systems

Abstract

Energy, exergy and economic analysis are proposed herein to evaluate regasification systems in Floating Storage Regasification Units (FSRUs). Three regasification systems typical in these types of vessels are considered: seawater system, open loop propane system and closed loop water-glycol system. The energy and exergy analyses were performed using the Engineering Equation Solver (EES), while Suite AspenONE programmes were used for the economic assessment. The exergy analysis provides a better understanding of the components of physical exergy (thermal and mechanical exergy) in order to define an exergy efficiency applicable to any liquefied natural gas (LNG) regasification system or FSRU. The results obtained prove the seawater regasification system to be most efficient from an energy and exergy standpoint. The specific energy consumption and exergy efficiency for this system are 227.33 kJ/kg and 50.00%, respectively. On the other hand, the open loop propane regasification system is most cost-effective for an LNG price between 1.32 and 11 USD/MMBtu. The vast amounts of destroyed exergy in the regasification process of current systems was also demonstrated and hence the need to develop new, more efficient configurations that could exploit the cold energy of LNG.