Reliquefaction of boil-off from pressure lng

摘要

A process is disclosed for reliquefying boil-off gas produced by pressurized liquid natural gas. In this process, refrigeration duty is provided to a heat exchanger by means of a refrigeration cycle. Pressurized natural gas is cooled by the heat exchanger and then expanded to a lower pressure to produce a liquid stream that is passed to a first phase separator. A boil-off vapor is passed through the heat exchanger and it is then compressed and cooled before being recycled back through the heat exchanger. The compressed, cooled boil-off gas is then expanded and passed to a second phase separator. A vapor stream produced by the second separator is removed from the process. A liquid stream produced by the second phase separator is passed to the first phase separator to produce a pressurized liquid having a temperature above about -112° C. and a pressure sufficient for the liquid to be at or below its bubble point.