Novel design of LNG (liquefied natural gas) reliquefaction process

This paper presents an investigation of novel LNG reliquefaction process where the cold exergy of subcooled LNG is utilized to recondense the vaporized light component of LNG after it is separated from the heavier component in a phase separator. The regeneration of cold exergy is especially effective as well as important in thermodynamic sense when a cryogenic process is involved. To verify the proposed idea, we performed an experimental study by facilitating liquid nitrogen apparatus to mock up the LNG reliquefaction process. Subcooled liquid nitrogen is produced for a commercial transportation container with a house-made atmospheric liquid nitrogen heat exchanger and then, having subooled degree of up to 19 K, it simulates the behavior of subcooled LNG in the lab-scale reliquefaction experiment. Recondensation of the vaporized gas is possible by using the cold exergy of subcooled liquid in a properly fabricated heat exchanger. Effect of heat exchanger performance factor and degree of subcooling on recondensation portion has been discussed in this paper. It is concluded that utilizing pressurized subcooled liquid that is obtained by liquid pump can surely reduce the pumping power of the vaporized natural gas and save the overall energy expenditure in LNG reliquefaction process.

► We performed experiments with LN2 to mock up the new LNG reliquefaction process. ► Subcooled liquid goes to heat exchanger, heater, and phase separator. ► Reliquefaction occurs when vapor enters heat exchanger and verified by experiments. ► Reliquefaction ratio increases when subcooling degree or system pressure increases.