With worldwide LNG demand increasing rapidly, LNG liquefaction plants and liquefaction processes are highly valued industry. Recently, there has been an increase in research and development of LNG-FPSO technologies in offshore liquefied natural gas (LNG) service instead of land-based LNG plants. While onshore LNG facilities have traditionally focused on power efficiency as a key criterion for process design and equipment selection, offshore LNG would require not only power efficiency but also safety and compactness. A new natural gas liquefaction cycle is proposed in this paper. The proposed cycle uses non-flammable refrigerants. Several natural gas liquefaction cycles using non-flammable refrigerants are suggested and compared to the proposed cycle in this paper. The liquefaction cycles using nonflammable refrigerants have an advantage in the view point of safety in the LNG-FPSO environment. The structure of the proposed cycle consists of carbon-dioxide pre-cooled and nitrogen expander liquefaction cycle. The proposed liquefaction cycle has the safety advantage with high power efficiency, therefore the proposed cycle could be suitable for the LNG-FPSO liquefaction process.

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