Method and apparatus for liquefying hydrocarbon streams

Abstract

A method of cooling at least two hydrocarbon streams such as natural gas, the method at least comprising the steps of: (a) providing at least first and second hydrocarbon streams ( 20, 20 a ); (b) passing the first hydrocarbon stream ( 20 ) through one or more first heat exchangers ( 12, 14 ) to provide a first cooled hydrocarbon stream ( 30 ); and (c) passing the second hydrocarbon stream ( 20 a ) through one or more second heat exchangers ( 12 a , 14 a ) to provide a second cooled hydrocarbon stream ( 30 a ); wherein a refrigerant circuit ( 100 ) provides cooling to the first heat exchanger (s) ( 12, 14 ) and the second heat exchanger (s) ( 12 a , 14 a ).

1 . A method of liquefying at least two hydrocarbon streams, the method at least comprising the steps of:
 (a) providing at least first and second hydrocarbon streams;   (b) passing the first hydrocarbon stream through one or more first heat exchangers to provide a first cooled hydrocarbon stream;   (c) passing the second hydrocarbon stream through one or more second heat exchangers to provide a second cooled hydrocarbon stream; and   (d) subsequently liquefying said first and second cooled hydrocarbon streams;   wherein a refrigerant circuit provides cooling to the one or more first heat exchangers and the one or more second heat exchangers, by passing separate streams of refrigerant through the one or more first heat exchangers of step (b) and through the one or more second heat exchangers of step (c), and subsequently compressing the refrigerant streams and commonly cooling the compressed refrigerant streams in one or more common coolers.   
     
     
         2 . A method as claimed in  claim 1 , wherein step (b) comprises passing the first hydrocarbon stream through 2, 3, 4 or 5 first heat exchangers; and wherein step (c) comprises passing the second hydrocarbon stream through 2, 3, 4 or 5 second heat exchangers. 
     
     
         3 . A method as claimed in  claim 1 , wherein said subsequently compressing the refrigerant streams comprises separately compressing each separate stream of refrigerant. 
     
     
         4 . A method as claimed in  claim 3 , further comprising combining the separately compressed streams of refrigerant prior to said commonly cooling in said one or more common coolers. 
     
     
         5 . A method as claimed in  claim 1 , wherein the passing of steps (b) and (c) forms part of a first cooling stage, and wherein the subsequently liquefying of step (d) comprises further cooling said first and second cooled hydrocarbon streams in a second cooling stage. 
     
     
         6 . A method as claimed in  claim 1 , wherein the first and second cooled hydrocarbon streams in step (d) are liquefied as separate streams. 
     
     
         7 . A method as claimed in  claim 1 , wherein the first and second hydrocarbon streams are feed streams. 
     
     
         8 . Apparatus for liquefying at least two hydrocarbon streams, the apparatus at least comprising:
 one or more first heat exchangers to cool a first hydrocarbon stream and to provide a first cooled hydrocarbon stream;   one or more second heat exchangers to cool a second hydrocarbon stream and to provide a second cooled hydrocarbon stream;   at least one liquefaction system arranged to liquefy said first and second cooled hydrocarbon streams; and   a refrigerant circuit comprising at least two separate streams of refrigerant one of which to provide cooling to the one or more first heat exchangers and the other one of which to provide cooling to the one or more second heat exchangers; at least one compressor for compressing the refrigerant streams; and one or more common coolers for commonly cooling the compressed refrigerant streams.   
     
     
         9 . Apparatus as claimed in  claim 8 , further comprising a stream splitter to divide a feed stream into at least the first and second hydrocarbon streams. 
     
     
         10 . Apparatus as claimed in  claim 8 , further comprising at least one separate compressor in each of the separate streams of refrigerant. 
     
     
         11 . Apparatus as claimed in  claim 10 , further comprising a combiner arranged downstream of the separate compressors and upstream of the one or more common coolers for combining the separate compressed refrigerant streams. 
     
     
         12 . A method of liquefying at least two hydrocarbon streams, the method at least comprising the steps of:
 (a) providing at least first and second hydrocarbon streams;   (b) passing the first hydrocarbon stream through one or more first heat exchangers to provide a first cooled hydrocarbon stream;   (c) passing the second hydrocarbon stream through one or more second heat exchangers to provide a second cooled hydrocarbon stream; and   (d) subsequently liquefying said first and second cooled hydrocarbon streams;   wherein a refrigerant circuit provides cooling to the one or more first heat exchangers and the one or more second heat exchangers, by passing separate streams of refrigerant through the one or more first heat exchangers of step (b) and through the one or more second heat exchangers of step (c), separately compressing each separate stream of refrigerant after passing through the at least one or more first heat exchangers and respectively the at least one or more second heat exchangers, and combining the compressed separate streams of refrigerant.   
     
     
         13 . Apparatus for liquefying at least two hydrocarbon streams, the apparatus at least comprising:
 one or more first heat exchangers to cool a first hydrocarbon stream and to provide a first cooled hydrocarbon stream;   one or more second heat exchangers to cool a second hydrocarbon stream and to provide a second cooled hydrocarbon stream;   at least one liquefaction system arranged to liquefy said first and second cooled hydrocarbon streams; and   a refrigerant circuit comprising at least two separate streams of refrigerant one of which to provide cooling to the one or more first heat exchangers and the other one of which to provide cooling to the one or more second heat exchangers and at least one separate compressor in each of the separate streams of refrigerant and a combiner arranged downstream of the separate compressors for combining the compressed separate streams of refrigerant.   
     
     
         14 . A method as claimed in  claim 2 , wherein step (b) comprises passing the first hydrocarbon stream through two first heat exchangers; and wherein step (c) comprises passing the second hydrocarbon stream through two second heat exchangers. 
     
     
         15 . A method as claimed in  claim 2 , wherein said subsequently compressing the refrigerant streams comprises separately compressing each separate stream of refrigerant. 
     
     
         16 . A method as claimed in  claim 14 , wherein said subsequently compressing the refrigerant streams comprises separately compressing each separate stream of refrigerant. 
     
     
         17 . A method as claimed in  claim 15 , further comprising combining the separately compressed streams of refrigerant prior to said commonly cooling in said one or more common coolers. 
     
     
         18 . A method as claimed in  claim 16 , further comprising combining the separately compressed streams of refrigerant prior to said commonly cooling in said one or more common coolers. 
     
     
         19 . A method as claimed in  claim 2 , wherein the passing of steps (b) and (c) forms part of a first cooling stage, and wherein the subsequently liquefying of step (d) comprises further cooling said first and second cooled hydrocarbon streams in a second cooling stage. 
     
     
         20 . A method as claimed in  claim 3 , wherein the passing of steps (b) and (c) forms part of a first cooling stage, and wherein the subsequently liquefying of step (d) comprises further cooling said first and second cooled hydrocarbon streams in a second cooling stage.