Dual mixed refrigerant cycle for gas liquefaction

摘要

A pressurised gas (102), especially natural gas is liquefied using two heat exchangers (104, 122) in each of which is provided by a mixed refrigerant (110, 124) which is vaporised at a respective essentially constant pressure. Feed precooling and high level liquid refrigerant subcooling and, preferably also low level refrigerant precooling are effected in the first heat exchanger (104) against vaporising low level refrigerant. Preferably, hydrocarbons of more than 3 or more than 4 carbon atoms are removed (116) by distillation (106) and subsequent fractionation (114) of natural gas cooled in the first heat exchanger (104). The process and apparatus of the invention are especially well-suited for installation on ships(including barges) and offshore platforms.