Cold exergy recovery during LNG regasification through a closed Brayton cycle

The liquified natural gas (LNG) regasification process is a source of cold exergy capable of being recovered for the exploitation of energy conversion. This paper presents a novel power plant structure that makes use of the LNG regasification process to increase the energy and exergy efficiency. The power plant consists of a closed Brayton cycle (CBC) fuelled by the flue gas released by the natural gas, where the cold exergy of the LNG is used to cool the compressor intake to reduce the compression work. As alternatives, helium and nitrogen are proposed as working fluids for the Brayton cycle. The research study is centred upon energy and exergy analyses, focused on establishing the operating conditions of maximum efficiency and selecting the working fluid, which is best suited for the regasification process. The results show a relevant increase in the overall efficiency approaching 60.82, an exergy efficiency of 59.08% and a specific power of 1.746 MW/(kg/s LNG).

Keywords: CBC, closed Brayton cycle, cold exergy, energy efficiency, exergy efficiency, LNG regasification, liquified natural gas, energy conversion, flue gas, compressor intake cooling, power plants