Economic evaluation of BOG management systems with LNG cold energy recovery in LNG import terminals considering quantitative assessment of equipment failures

Abstract

This study presents an economic evaluation for comparing two systems designed to manage boil-off gas (BOG) and to take advantage of liquefied natural gas (LNG) cold energy in LNG import terminals. The first system, called a BOG recondensation system, directly uses LNG cold energy by mixing BOG and LNG in the recondenser. The product of the system is natural gas (NG) obtained from the regasification process, and its required electricity must be purchased from the wholesale market. The other system is a BOG-fueled gas turbine cycle combined with a Rankine cycle. This system produces both NG and electric power. The gas turbine cycle uses BOG as the fuel for generating power, and its flue gas provides heat for the Rankine cycle in which the working fluid is used to recover LNG cold energy and cool the turbine inlet air. An exergy-based economic evaluation and a profitability comparison are employed to separately estimate the costs of each product generated by the systems and synthetically compare the economical preference between the two systems, respectively. The unavailability of the system provides the influence of equipment failure on the economic evaluation by estimating the costs and loss of profit caused by the unavailability. The results show that the BOG-fueled gas turbine cycle combined with a Rankine cycle is a better option than the recondensation system.