METHOD FOR RE-LIQUEFACTION OF BOIL-OFF GAS

摘要

A method for re-liquefaction of a stream of boil-off gas (12), wherein the boil-off gas is being cooled and liquefied in a closed-loop refrigeration system before being returned (13) to a storage vessel (20). The refrigeration comprises splitting a coolant stream (15) into a first stream (16) and a second stream (17) and isentropically expanding (8, 9) said first and second streams, and selectively heat exchanging (5, 6, 7) the streams before merging said first and second streams. With the invented method, complete re­liquefaction is achieved for a boil-off gas having up to 30% nitrogen by volume.