US Patent 8656733 Liquefaction method and system

Liquefaction using a closed loop refrigeration system, including compressing a gaseous refrigerant stream; cooling at least a portion of the compressed gaseous refrigerant stream in a first heat exchanger; expanding a first portion of the cooled, compressed gaseous refrigerant stream from the first heat exchanger to provide a first expanded gaseous refrigerant stream; cooling and substantially liquefying a feed gas stream to form a substantially liquefied feed gas stream in a second heat exchanger through indirect heat exchange against the first portion of the first expanded gaseous refrigerant stream; and further cooling a second portion of the cooled, compressed gaseous refrigerant stream from the first heat exchanger in a third heat exchanger by indirect heat exchange with a second portion of the first expanded gaseous refrigerant stream, wherein the first expanded gaseous refrigerant stream exiting the first expander is substantially vapor.