摘要:
The present invention provides a method and apparatus (1) for producing a liquefied natural gas stream (100), wherein a natural gas stream (10) is cooled in a heat exchanger (2) against a refrigerant fluid being cycled in a refrigerant circuit (3). The cycling of the refrigerant fluid comprises: (a) feeding a first refrigerant fluid (20) into an axial compressor (5); (b) compressing the first refrigerant fluid (20) in the axial compressor (5), thereby obtaining a compressed first refrigerant fluid (30); (c) feeding the compressed first refrigerant fluid (30) at a first pressure level into a centrifugal compressor (6); (d) feeding a second refrigerant fluid (40) at a second pressure level being lower than the first pressure level into the centrifugal compressor (6); (e) compressing the compressed first refrigerant fluid (30) and the second refrigerant fluid (40) in the centrifugal compressor (6), thereby obtaining a compressed refrigerant fluid mixture (50); (f) cooling the compressed refrigerant fluid mixture (50) in a heat exchanger (13), thereby obtaining a cooled compressed refrigerant fluid mixture (60); (g) separating the cooled compressed refrigerant fluid mixture (60) into at least two streams; (h) evaporating the two streams obtained in step (g) at different locations of a heat exchanger (2) in heat exchanging contact with the natural gas stream (10) to be cooled; and (i) retrieving the first and second refrigerant fluids (20,40) from the two streams evaporated in step (h).