Patent ID: RE39637

Claim:
A method for the liquefaction of a feed gas which comprises providing at least a portion of the total refrigeration required to cool and condense the feed gas by utilizing (a) a first refrigeration system comprising at least one recirculating refrigeration circuit, wherein the first refrigeration system utilizes two or more refrigerant components and provides refrigeration in a first temperature range; and (b) a second refrigeration system which provides refrigeration in a second temperature range by work expanding a pressurized gaseous refrigerant stream; wherein the first recirculating refrigeration system is operated by (1) compressing a first gaseous refrigerant; (2) cooling and at least partially condensing the resulting compressed refrigerant; (3) reducing the pressure of the resulting at least partially condensed compressed refrigerant; (4) vaporizing the resulting reduced-pressure refrigerant to provide refrigeration in the first temperature range and yield a vaporized refrigerant; and (5) recirculating the vaporized refrigerant to provide the first gaseous refrigerant of (1); wherein at least a portion of the cooling in (2) is provided by indirect heat exchange with one or more additional vaporizing refrigerant streams provided by a third recirculating refrigeration circuit system .