Method For the Liquefaction of a Hydrocarbon-Rich Stream

A method for the liquefaction of a hydrocarbon-rich stream, wherein the hydrocarbon-rich stream to be liquefied is heat exchanged against a refrigerant, the method at least comprising the steps of:

• (a) evaporating a liquid refrigerant using heat from the hydrocarbon-rich stream, thereby obtaining an evaporated refrigerant;
• (b) compressing the evaporated refrigerant, thereby obtaining a compressed refrigerant;
• (c) cooling the compressed refrigerant against ambient thereby fully condensing the compressed refrigerant;
• (d) expanding the fully condensed compressed refrigerant thereby forming said liquid refrigerant;
• wherein, before expanding in step (d), the fully condensed compressed refrigerant is further sub-cooled by indirect heat exchange against an auxiliary refrigerant being cycled in an auxiliary refrigerant cycle comprising an auxiliary compressing step followed by drawing heat from the fully condensed compressed refrigerant for its further sub-cooling,
• wherein the auxiliary refrigerant is selected to have a higher bubble point temperature than the liquid refrigerant when determined under equal-pressure condition.