Lng system with optimized heat exchanger configuration

Abstract

The current invention provides a methodology and apparatus for the liquefaction of normally gaseous material, most notably natural gas, which reduces the number of process vessels required and/or reduces space requirements over convention apparatus.

1 . A process for liquefying natural gas, said process comprising:
 (a) cooling a natural gas stream in a first refrigeration cycle via indirect heat exchange with a first refrigerant; and   (b) downstream of step (a), cooling said natural gas stream in a second refrigeration cycle via indirect heat exchange with a second refrigerant,   wherein at least one of said first and second refrigerants is a pure component refrigerant,   wherein less than about 10 percent of the natural gas mechanical cooling duty of at least one of said first and second refrigeration cycles is provided by core-in-kettle heat exchangers.   
   
   
       2 . The process of  claim 1  wherein less than about 5 percent of the natural gas mechanical cooling duty of said first and second refrigeration cycles is provided by core-in-kettle heat exchangers. 
   
   
       3 . The process of  claim 1  wherein at least about 90 percent of the natural gas mechanical cooling duty of said first and second refrigeration cycles is provided by one or more plate-fin heat exchangers. 
   
   
       4 . The process of  claim 3  wherein said plate-fin heat exchangers are brazed aluminum plate-fin heat exchangers. 
   
   
       5 . The process of  claim 1  wherein said second refrigerant is a pure component refrigerant. 
   
   
       6 . The process of  claim 1  wherein said first and second refrigerants are both pure component refrigerants. 
   
   
       7 . The process of  claim 1  wherein said first refrigerant comprises predominately propane and said second refrigerant comprises predominately ethylene. 
   
   
       8 . The process of  claim 1  further comprising, downstream of step (b), cooling said natural gas stream in a third refrigeration cycle via indirect heat exchange with a third refrigerant. 
   
   
       9 . The process of  claim 8  wherein said third refrigerant is a pure component refrigerant. 
   
   
       10 . The process of  claim 8  wherein said third refrigeration cycle is an open refrigeration cycle employing a portion of said natural gas stream as said third refrigerant. 
   
   
       11 . The process of  claim 8  wherein said first, second, and third refrigerants are all pure component refrigerants. 
   
   
       12 . A process for liquefying natural gas comprising:
 (a) cooling a natural gas stream in a first refrigeration cycle employing a first refrigerant;   (b) downstream of step (a), cooling the natural gas stream in a second refrigeration cycle employing a second refrigerant;   (c) downstream of step (b), cooling the natural gas stream in a third refrigeration cycle employing a third refrigerant;   wherein said third refrigeration cycle is an open refrigeration cycle that uses a portion of said natural gas stream as said third refrigerant,   wherein at least about 90 percent of the combined natural gas mechanical cooling duty of said first, second, and third refrigeration cycles is provided by plate-fin heat exchangers.   
   
   
       13 . The process of  claim 12  wherein said cooling of steps (a), (b), and (c) is carried out without the use of any core-in-kettle heat or spiral wound exchangers. 
   
   
       14 . The process of  claim 12  wherein all of said cooling of steps (a), (b), and (c) is carried in plate-fin heat exchangers. 
   
   
       15 . The process of  claim 12  further comprising, cooling said natural gas stream via expansion in said third refrigeration cycle. 
   
   
       16 . The process of  claim 15  wherein the pressure of said natural gas stream is reduced by at least about 100 psi in said third refrigeration cycle. 
   
   
       17 . The process of  claim 15  wherein said natural gas stream enters said third refrigeration cycle at a pressure of at least about 400 psia, wherein the pressure of said natural gas stream is reduced by at least 250 psi in said third refrigeration cycle. 
   
   
       18 . The process of  claim 12  wherein said first refrigerant comprises predominately propane and/or propylene, said second refrigerant comprises predominately ethane and/or ethylene, and said third refrigerant comprises predominately methane. 
   
   
       19 . A process for liquefying natural gas comprising:
 (a) cooling a natural gas stream in a first methane heat exchanger via indirect heat exchange with at least one predominately-methane first refrigerant stream to thereby produce a first cooled natural gas stream;   (b) dividing said first cooled natural gas stream into a first refrigerant portion and a first product portion;   (c) expanding said first refrigerant portion to thereby produce a first expanded refrigerant portion; and   (d) using said first expanded refrigerant portion as at least a portion of said first refrigerant stream in said first methane heat exchanger.   
   
   
       20 . The process of  claim 19  wherein said first expanded refrigerant portion is not subjected to phase separation prior to being used as said first refrigerant stream in said first methane heat exchanger. 
   
   
       21 . The process of  claim 19  further comprising, cooling said first product portion in a second methane heat exchanger via indirect heat exchange with at least one predominately-methane second refrigerant stream to thereby produce a second cooled natural gas stream. 
   
   
       22 . The process of  claim 21  further comprising, dividing said second cooled natural gas stream into a second refrigerant portion and a second product portion. 
   
   
       23 . The process of  claim 22  further comprising, expanding said second refrigerant portion to thereby produce a second expanded refrigerant portion and using said second expanded refrigerant portion as at least a portion of said second refrigerant stream in said second methane heat exchanger. 
   
   
       24 . The process of  claim 23  wherein said second expanded refrigerant portion is not subjected to phase separation prior to being used as said second refrigerant stream in said second methane heat exchanger. 
   
   
       25 . The process of  claim 23  wherein said second expanded refrigerant portion is heated in said second methane heat exchanger to thereby produce a warmed second expanded refrigerant portion, wherein said process further comprises employing said warmed second expanded refrigerant portion as at least a portion of said first refrigerant stream in said first methane heat exchanger. 
   
   
       26 . The process of  claim 22  further comprising, expanding said second product portion to thereby produce a two-phase stream comprising a vapor third refrigerant portion and a liquid third product portion and using said third refrigerant portion as at least a portion of said second refrigerant stream in said second methane heat exchanger. 
   
   
       27 . The process of  claim 26  wherein said third refrigerant portion is heated in said second methane heat exchanger to thereby produce a warmed third refrigerant portion, wherein said process further comprises using said warmed third refrigerant portion as at least a portion of said first refrigerant stream in said first methane heat exchanger. 
   
   
       28 . The process of  claim 26  further comprising, expanding said third product portion to thereby produce an expanded final product stream comprising liquified natural gas and introducing at least a portion of said expanded final product stream into an LNG storage tank. 
   
   
       29 . The process of  claim 28  further comprising, removing vapors from said LNG storage tank and employing said vapors as at least a portion of said first and/or second refrigerant streams. 
   
   
       30 . The process of  claim 19  further comprising, prior to step (a) cooling said natural gas stream via indirect heat exchange with an initial refrigerant stream, wherein said initial refrigerant stream comprises predominately propane, propylene, ethane, and/or ethylene. 
   
   
       31 . The process of  claim 30  wherein said initial refrigerant stream comprises predominately propane. 
   
   
       32 . The process of  claim 31  further comprising, prior to step (a) cooling said natural gas stream via indirect heat exchange with intermediate refrigerant stream, wherein said intermediate refrigerant stream comprises predominately ethane and/or ethylene. 
   
   
       33 . A process comprising: gasifying LNG produced by the process of  claim 1 . 
   
   
       34 . A process comprising: gasifying LNG produced by the process of  claim 12 . 
   
   
       35 . A process comprising: gasifying LNG produced by the process of  claim 19 . 
   
   
       36 . A computer simulation process comprising: using a computer to simulate the process of  claim 1 . 
   
   
       37 . A computer simulation process comprising: using a computer to simulate the process of  claim 12 . 
   
   
       38 . A computer simulation process comprising: using a computer to simulate the process of  claim 19 . 
   
   
       39 . A facility for processing natural gas into producing LNG, said facility comprising:
 a first refrigeration cycle for cooling natural gas with a first refrigerant; and   a second refrigeration cycle for cooling said natural gas with a second refrigerant,   wherein at least one of said first and second refrigerants is a pure component refrigerant,   wherein at least one of said first and second refrigeration cycles does not comprise any core-in-kettle heat exchangers that are operable to significantly cool said natural gas.   
   
   
       40 . The facility of  claim 39  wherein said first and second refrigeration cycles do not comprise any core-in-kettle or spiral-wound heat exchangers that are operable to cool said natural gas. 
   
   
       41 . The facility of  claim 39  wherein said first and second refrigeration cycles include a plurality of plate-fin heat exchangers that are operable to cool said natural gas. 
   
   
       42 . The facility of  claim 39  wherein said first and second refrigerants are both pure component refrigerants. 
   
   
       43 . The facility of  claim 39  wherein said first refrigerant comprises predominately propane and/or propylene and said second refrigerant comprises predominately ethane and/or ethylene. 
   
   
       44 . The facility of  claim 39  further comprising, a third refrigeration cycle for cooling said natural gas with a third refrigerant. 
   
   
       45 . The facility of  claim 44  wherein said third refrigerant comprises predominately methane. 
   
   
       46 . The facility of  claim 44  wherein said third refrigeration cycle is an open refrigeration cycle. 
   
   
       47 . The facility of  claim 39  wherein said third refrigeration cycle includes a plurality of expansion devices for sequentially lowering the pressure of said natural gas, wherein said third refrigeration cycle employs less than three vapor/liquid separation vessels. 
   
   
       48 . The facility of  claim 47  wherein said third refrigeration cycle employs less than two vapor/liquid separation vessels.