Volume 29: Closing Carbon Cycles – A Transformation Process Involving Technology, Economy, and Society: Part IV

Case Studies of Single Nitrogen Expander Liquefaction for FLNG WE Lin Chan, Ivan C.K.Tam, Arun Kr Dev

Abstract

Nowadays, global carbon dioxide emissions into the atmosphere have reached a historically high level due to carbon dioxide emissions. The current effort to change the alternative energy source of LNG fuel was found to be one of the cleanest fossil fuels due to lower carbon emissions to ease the rapid growth of carbon emissions.
LNG marine industry forecasts that the increasing demand for FLNG vessels will accelerate the development of gas resources, research work on the system process analysis and optimisation of the Liquefaction system. The rapid growth in equipment and processes of FLNG development is the response to the challenges due to weight and space limits.
One of the critical objectives onboard FLNG is to build the combined plant models of clean energy. The research boundary covers processes of LNG liquefaction, nitrogen separation and boil-off gas handling. BOG re-liquefaction will be used as a fuel gas supply system. BOG will also be converted to clean energy fuel such as hydrogen or ammonia for the main and auxiliary engines onboard.
A small-scale liquefaction process with a refrigerant cycle is proposed in this study to meet these FLNG challenges. The Brayton refrigeration (BR) cycle is found to be most suitable for FLNG vessels, among other refrigerant cycles. The BR cycle using nitrogen as a refrigerant and a single expander is the focus of this study [8].

Keywords FLNG, LNG; exergy, efficiency, liquefaction, cycle, regasification, pre-cooling