Method and apparatus for liquefying a hydrocarbon stream

Abstract

A method and apparatus for liquefying a hydrocarbon stream ( 10 ) such as natural gas. The method comprises the steps of: (a) compressing the hydrocarbon stream ( 10 ) using one or more compressors ( 12 ) driven by one or more steam turbines ( 14 ) to provide a compressed hydrocarbon stream ( 20 ); (b) heat exchanging the compressed hydrocarbon stream ( 20 ) against one or more refrigerant streams ( 40 ) to fully condense the compressed hydrocarbon stream ( 20 ) and provide a liquefied hydrocarbon stream ( 30 ) and one or more warmed refrigerant streams ( 50 ); (c) compressing at least one of the warmed refrigerant stream(s) ( 50 ) of step (b) using one or more compressors ( 18 ) driven by one or more gas turbines ( 22 ); and (d) at least partly driving one or more of the steam turbines ( 14 ) of step (a) using steam provided by one or more of the gas turbines ( 22 ) of step (c).

1 . A method of liquefying a hydrocarbon feed stream, the method at least comprising the steps of:
 heat exchanging a compressed hydrocarbon stream against one or more refrigerant streams to fully condense the compressed hydrocarbon stream and provide a liquefied hydrocarbon stream and one or more warmed refrigerant streams;   compressing at least one of said one or more warmed refrigerant stream(s) using one or more refrigerant compressors driven by one or more gas turbines;   driving one or more compressor-driving steam turbines, at least partly using steam provided by at least one of said one or more gas turbines; and   providing said compressed hydrocarbon stream by compressing a hydrocarbon feed stream using at least one or more feed compressors driven by said one or more compressor-driving steam turbines.   
   
   
       2 . A method as claimed in  claim 1 , wherein the heat exchanging of the compressed hydrocarbon stream against the one or more refrigerant streams involves any number of one to ten gas turbines. 
   
   
       3 . A method as claimed in  claim 1 , wherein the heat exchanging of the compressed hydrocarbon stream against the one or more refrigerant streams involves at least two cooling stages. 
   
   
       4 . A method as claimed in  claim 3 , wherein the at least two cooling stages comprise:
 a first cooling stage adapted to cool the hydrocarbon stream to form a cooled hydrocarbon stream at a temperature below 0° C. against at least one first refrigerant stream, which first refrigerant stream is compressed by a first refrigerant stream compressor driven by at least one gas turbine; and   a second cooling stage adapted to liquefy the cooled hydrocarbon stream from the first cooling stage.   
   
   
       5 . A method as claimed in  claim 4 , wherein liquefaction of the cooled hydrocarbon stream in the second cooling stage is carried out by two or more parallel liquefaction systems, each of which involves at least one second refrigerant stream that is compressed by a second refrigerant stream compressor driven by a gas turbine. 
   
   
       6 . A method as claimed in  claim 5 , wherein the refrigerant for each second refrigerant stream is a mixed refrigerant based on two or more components selected from the group comprising nitrogen, methane, ethane, ethylene, propane, propylene, butanes and pentanes. 
   
   
       7 . A method as claimed in  claim 4 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines. 
   
   
       8 . A method as claimed in  claim 1 , wherein said liquefied hydrocarbon stream flows at a rate that is less than or equal to the flow rate of the hydrocarbon feed stream being compressed with said one or more feed compressors. 
   
   
       9 . A method as claimed in  claim 1 , wherein the compressed hydrocarbon stream after it has been compressed using the at least one or more feed compressors driven by said one or more compressor-driving steam turbines, is not mixed with any compressed stream that has not been compressed with the at least one or more feed compressors driven by said one or more compressor-driving steam turbines. 
   
   
       10 . A method as claimed in  claim 1 , wherein exhaust steam provided by the one or more steam turbines at least partly provides heat for use in removal of acid gas components in the hydrocarbon feed stream prior to its compression. 
   
   
       11 . Apparatus for liquefying a hydrocarbon feed stream, the apparatus at least comprising:
 a liquefying system arranged to receive a compressed hydrocarbon stream, the liquefying system comprising one or more cooling stages involving one or more refrigerant streams, through which cooling stage(s) the compressed hydrocarbon stream passes to provide one or more warmed refrigerant streams and a liquefied hydrocarbon stream;   one or more refrigerant compressors driven by one or more gas turbines to compress at least one of the warmed refrigerant streams;   one or more compressors driven by one or more compressor-driving steam turbines; and   one or more heat exchangers and one or more water/steam streams to transfer heat provided by the one or more gas turbines to at least partly drive one or more of the compressor-driving steam turbines,   wherein the one or more compressors driven by the one or more compressor-driving steam turbines are hydrocarbon feed compressor(s) arranged to receive and compress a hydrocarbon feed stream to provide the compressed hydrocarbon stream.   
   
   
       12 . A method as claimed in  claim 2 , wherein the heat exchanging of the compressed hydrocarbon stream against the one or more refrigerant streams involves at least two cooling stages. 
   
   
       13 . A method as claimed in  claim 12 , wherein the at least two cooling stages comprise:
 a first cooling stage adapted to cool the hydrocarbon stream to form a cooled hydrocarbon stream at a temperature below 0° C. against at least one first refrigerant stream, which first refrigerant stream is compressed by a first refrigerant stream compressor driven by at least one gas turbine; and   a second cooling stage adapted to liquefy the cooled hydrocarbon stream from the first cooling stage.   
   
   
       14 . A method as claimed in  claim 13 , wherein liquefaction of the cooled hydrocarbon stream in the second cooling stage is carried out by two or more parallel liquefaction systems, each of which involves at least one second refrigerant stream that is compressed by a second refrigerant stream compressor driven by a gas turbine. 
   
   
       15 . A method as claimed in  claim 14 , wherein the refrigerant for each second refrigerant stream is a mixed refrigerant based on two or more components selected from the group comprising nitrogen, methane, ethane, ethylene, propane, propylene, butanes and pentanes. 
   
   
       16 . A method as claimed in  claim 5 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines. 
   
   
       17 . A method as claimed in  claim 6 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines. 
   
   
       18 . A method as claimed in  claim 13 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines. 
   
   
       19 . A method as claimed in  claim 14 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines. 
   
   
       20 . A method as claimed in  claim 15 , wherein each gas turbine compressing a refrigerant stream provides steam for use in driving one or more of the compressor-driving steam turbines.