Patent ID: 8181481

Claim:
A method of cooling a stream, wherein the stream is cooled in a heat exchanger train against a refrigerant fluid being cycled in a refrigerant circuit, the cycling of the refrigerant fluid comprising: (a) feeding a first refrigerant fluid into an axial compressor; (b) compressing the first refrigerant fluid in the axial compressor, thereby obtaining a compressed first refrigerant fluid; (c) feeding the compressed first refrigerant fluid at a first pressure level into a centrifugal compressor at a first inlet; (d) feeding a second refrigerant fluid at a second pressure level into the centrifugal compressor at a second inlet, the second pressure level being lower than the first pressure level; (e) compressing the compressed first refrigerant fluid fed in step (c) and the second refrigerant fluid fed in step (d) in the centrifugal compressor, thereby obtaining a compressed refrigerant fluid mixture; (f) cooling the compressed refrigerant fluid mixture obtained in step (e) in a heat exchanger against a cooler stream, thereby obtaining a cooled compressed refrigerant fluid mixture; (g) separating the cooled compressed refrigerant fluid mixture obtained in step (f) into at least two streams; (h) evaporating the at least two streams obtained in step (g) at different pressure levels in the exchanger train, in heat exchanging contact with the stream to be cooled thereby cooling the stream; and retrieving the first and second refrigerant fluids from the at least two streams evaporated in step (h).