Performance Improvement of a Boil-off Gas Re-condensation Process with Pre-cooling at LNG Terminals

Abstract

Since liquefied natural gas (LNG) is stored at a temperature of about -160°C under ambient pressure, it is unable to avoid unexpected generation of boil-off gas (BOG) from LNG storage tanks due to heat transfer from the surroundings to the cryogenic system. Reasonable and effective treatment of BOG, can not only reduce the waste of energy at LNG terminals, but also guarantee the safety and stability of the system. This paper puts up with a novel process to condense the double-stage pre-cooled and compressed BOG by means of heat transfer with LNG. With the aim of minimizing the total power consumption, Aspen HYSYS is employed to simulate and optimize the process. It is indicated that system performance has been improved in comparison with the direct compression process and the re-condensation process with single-stage pre-cooling. Engineering issues about this process are discussed, simultaneously.

Keywords

• boil-off gas, re-condensation, pre-cooling, thermodynamic analysis, process optimization

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