Method and apparatus for producing a cooled hydrocarbon stream

Abstract

A method and apparatus for cooling two or more liquefied hydrocarbon streams. First ( 30 ) and second ( 30 a ) liquefied hydrocarbon streams are provided and combined thereby providing a combined liquefied hydrocarbon stream ( 40 ). The combined liquefied hydrocarbon stream ( 40 ) is further cooled against a refrigerant thereby providing a further cooled liquefied hydrocarbon stream ( 50 ) such as liquefied natural gas (LNG).

1 . A method of producing a cooled liquefied hydrocarbon stream, the method at least comprising the steps of:
 (a) providing a first liquefied hydrocarbon stream by passing a hydrocarbon first feed stream through a first liquefying system having one or more cooling stages, at least one of which has a closed refrigerant circuit;   (b) providing a second liquefied hydrocarbon stream by passing a hydrocarbon second feed stream through a second liquefying system having one or more cooling stages, at least one of which has a closed refrigerant circuit;   (c) combining the first liquefied stream with the second liquefied stream to provide a combined liquefied stream; and   (d) further cooling the combined liquefied stream against a refrigerant to provide a cooled liquefied hydrocarbon stream.   
   
   
       2 . A method as claimed in  claim 1 , wherein each liquefying system comprises at least a first cooling stage followed by a second cooling stage. 
   
   
       3 . A method as claimed in  claim 2 , wherein the second cooling stage has said closed refrigerant circuit. 
   
   
       4 . A method as claimed in  claim 2 , wherein the first cooling stage is a pre-cooling stage, and the second cooling stage is a main cryogenic cooling stage. 
   
   
       5 . A method as claimed in  claim 1 , wherein the first and second liquefying systems have a common first cooling stage. 
   
   
       6 . A method as claimed in  claim 5 , wherein the common first cooling stage is a pre-cooling stage. 
   
   
       7 . A method as claimed in  claim 2 , wherein the refrigerant of the common first cooling stage or of each first cooling stage is a single component refrigerant. 
   
   
       8 . A method as claimed in  claim 7 , wherein the single component refrigerant is formed by propane. 
   
   
       9 . A method as claimed in  claim 2 , wherein the refrigerant of the second cooling stage is a mixed refrigerant. 
   
   
       10 . A method as claimed in  claim 1 , further comprising a step:
 (e) passing the further cooled liquefied hydrocarbon stream through an end-treatment stage.   
   
   
       11 . A method as claimed in  claim 10 , wherein the end-treatment stage comprises one or more separation steps. 
   
   
       12 . A method as claimed in  claim 1 , wherein the refrigerant in step (d) is a single component refrigerant. 
   
   
       13 . A method as claimed in  claim 12 , wherein the single component refrigerant is formed by nitrogen. 
   
   
       14 . A method as claimed in  claim 1 , wherein the refrigerant in step (d) is a mixed refrigerant. 
   
   
       15 . A method as claimed in  claim 1 , wherein the refrigerant in step (d) is natural gas. 
   
   
       16 . Apparatus for the production of a cooled liquefied hydrocarbon stream from two or more liquefied hydrocarbon streams, the apparatus at least comprising:
 a first liquefying system to provide a first liquefied hydrocarbon stream comprising at least two cooling stages, at least one of which has a closed refrigerant circuit;   a second liquefying system to provide a second liquefied hydrocarbon stream comprising at least two cooling stages, at least one of which has a closed refrigerant circuit;   a combiner to combine the first liquefied stream and the second liquefied stream to provide a combined liquefied stream; and   a further cooling stage arranged to cool the combined liquefied stream against a refrigerant to provide a cooled liquefied product stream.   
   
   
       17 . A method as claimed in  claim 3 , wherein the first cooling stage is a pre-cooling stage, and the second cooling stage is a main cryogenic cooling stage. 
   
   
       18 . A method as claimed in  claim 2 , wherein the first and second liquefying systems have a common first cooling stage. 
   
   
       19 . A method as claimed in  claim 3 , wherein the first and second liquefying systems have a common first cooling stage. 
   
   
       20 . A method as claimed in  claim 4 , wherein the first and second liquefying systems have a common first cooling stage.