Method and apparatus for cooling a hydrocarbon stream

Abstract

A method of cooling a hydrocarbon stream such as natural gas from a feed stream ( 10 ), the method at least comprising the steps of: (a) passing the feed stream ( 10 ) and a first refrigerant stream ( 20 ) through a cooling stage ( 100 ) including one or more heat exchangers ( 12 a, 12 b ) to provide a cooled hydrocarbon stream ( 30 ); and (b) circulating the first refrigerant stream ( 20 ) around a first refrigerant circuit ( 110 ) which includes one or more compressors ( 14 ), one or more coolers ( 16, 18 ) after the compressor (s), and a refrigerant accumulator ( 22 ) after the cooler (s); wherein there are no further coolers between the refrigerant accumulator ( 22 ) and the heat exchanger or the first of more than one heat exchanger ( 12 a, 12 b ).

1 . A method of treating a feed stream comprising a hydrocarbon stream, the method at least comprising the steps of:
 (a) passing the feed stream and a first refrigerant stream through a cooling stage including one or more heat exchangers to provide a cooled hydrocarbon stream; and   (b) circulating the first refrigerant stream around a first refrigerant circuit which includes one or more compressors, one or more coolers after the compressor(s), and a refrigerant accumulator after the cooler(s);   wherein there are no further coolers between the refrigerant accumulator and the cooling stage.   
   
   
       2 . A method according to  claim 1  wherein the first refrigerant of the first refrigerant stream is a mixed refrigerant. 
   
   
       3 . A method according to  claim 1  wherein the cooling stage comprises two or three heat exchangers. 
   
   
       4 . A method according to  claim 3  wherein each heat exchanger involves a different first refrigerant pressure. 
   
   
       5 . A method according to  claim 1  wherein one or more of the heat exchangers,
 is or are spiral-wound or spool-wound heat exchanger(s).   
   
   
       6 . A method according to  claim 1  wherein the first refrigerant circuit comprises two coolers between the one or more compressors and the refrigerant accumulator. 
   
   
       7 . A method according to  claim 6  wherein the lattermost cooler in the first refrigerant circuit in the direction of the flow of the first refrigerant stream is larger than the first cooler after the compressor(s) in the direction of the flow of the first refrigerant. 
   
   
       8 . A method according to  claim 1  wherein the method comprises the further step of:
 (c) passing the cooled hydrocarbon stream through a second cooling stage comprising one or more heat exchangers through which a second refrigerant stream also passes, to provide a liquefied hydrocarbon stream.   
   
   
       9 . A method as claimed in  claim 8  to liquefy natural gas and provide a liquefied natural gas stream. 
   
   
       10 . A method as claimed in  claim 1  wherein the temperature of the first refrigerant stream outflowing the refrigerant accumulator is wholly or substantially equal to the temperature of the first refrigerant stream entering the first of one or more heat-exchanger(s) through an inlet. 
   
   
       11 . A method as claimed in  claim 1  wherein at least one of the heat exchangers of step (a) are tube-in-shell heat exchangers. 
   
   
       12 . A method as claimed in  claim 11  wherein partial condensation of the feed stream and any second refrigerant stream is carried out in at least one heat exchanger that has first refrigerant on the cold (shell) side of the heat exchanger, and different tube circuits for the feed stream and any second refrigerant stream located in the same shell. 
   
   
       13 . Apparatus for treating a feed stream comprising a hydrocarbon stream, the apparatus at least comprising:
 a first cooling stage including one or more heat exchangers through which the feed stream and a first refrigerant stream can pass; and   a first refrigerant circuit around which the first refrigerant stream circulates, the first refrigerant circuit having one or more compressors, one or more coolers after the compressor(s), and a refrigerant accumulator after the cooler(s),   
     wherein there are no further coolers between the refrigerant accumulator and the cooling stage. 
   
   
       14 . Apparatus according to  claim 13  wherein the first refrigerant circuit has two heat exchangers, one compressor, and sequentially a first cooler and a second cooler, which second cooler is larger than the first cooler. 
   
   
       15 . Apparatus according to  claim 13  further comprising:
 a second cooling stage to liquefy the cooled hydrocarbon stream of the first cooling stage to provide a liquefied hydrocarbon stream.   
   
   
       16 . A method according to  claim 1  wherein the first refrigerant of the first refrigerant stream is a mixed refrigerant comprising a mixture of gases selected from the group comprising nitrogen, methane, ethane, ethylene, propane, propylene, butane and pentane. 
   
   
       17 . A method according to  claim 2  wherein the cooling stage comprises two or three heat exchangers. 
   
   
       18 . A method according to  claim 17  wherein each heat exchanger involves a different first refrigerant pressure. 
   
   
       19 . A method according to  claim 1  wherein all the heat exchangers is or are spiral wound or spool-wound heat exchanger(s). 
   
   
       20 . A method according to  claim 2  wherein one or more of the heat exchangers is or are spiral-wound or spool-wound heat exchanger(s).