Patent ID: 8464551

Claim:
A method of liquefaction using a closed loop refrigeration system utilizing substantially isentropic expansion of a gaseous refrigerant, the method comprising the steps of: (a) compressing a gaseous refrigerant stream in at least one compressor; b) cooling at least a portion of the compressed gaseous refrigerant stream in a first heat exchanger to below ambient temperature, thereby creating a compressed, cooled refrigerant stream; c) expanding at least a portion of the compressed, cooled refrigerant stream in a first expander to provide a first expanded gaseous refrigerant stream, wherein the first expanded gaseous refrigerant stream exiting the first expander is substantially vapor; d) 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 at least a first portion of the first expanded gaseous refrigerant stream; e) extracting a second portion of the first expanded gaseous refrigerant stream from the first portion of the first expanded gaseous refrigerant stream from an intermediate location of the second heat exchanger to balance a precooling section of the second heat exchanger; and, f) extracting at least a third portion of the first expanded gaseous refrigerant stream from the first portion of the first expanded gaseous refrigerant stream at the warm end of the second heat exchanger.