Alternative pre-cooling arrangement

Abstract

A natural gas liquefaction system, the system comprising a first precooling refrigeration system that accepts at least a natural gas feed stream, a second precooling refrigeration system that accepts at least a first refrigerant stream; and a cryogenic heat exchanger fluidly connected to the first precooling refrigeration system and the second precooling refrigeration system that accepts the natural gas feed stream from the first precooling refrigeration system and the first refrigerant stream from the second precooling refrigeration system to liquefy the natural gas feed stream, where the second precooling refrigeration system accepts only stream(s) having a composition different from the stream(s) accepted by the first precooling refrigeration system.

1 . A natural gas liquefaction system, the system comprising:
 a first precooling refrigeration system that accepts at least a natural gas feed stream;   a second precooling refrigeration system that accepts at least a first refrigerant stream; and   a cryogenic heat exchanger fluidly connected to the first precooling refrigeration system and the second precooling refrigeration system that accepts the natural gas feed stream from the first precooling refrigeration system and the first refrigerant stream from the second precooling refrigeration system to liquefy the natural gas feed stream,   
     wherein the second precooling refrigeration system accepts only stream(s) having a composition different from the stream(s) accepted by the first precooling refrigeration system. 
   
   
       2 . The system of  claim 1 , wherein the first refrigerant stream is a mixed refrigerant stream. 
   
   
       3 . The system of  claim 1 , wherein the first refrigerant stream comprises nitrogen, methane, ethane, and propane. 
   
   
       4 . The system of  claim 1 , further comprising a subcooler exchanger fluidly connected to the cryogenic heat exchanger, wherein the subcooler exchanger accepts a second refrigerant stream from the cryogenic heat exchanger to subcool the natural gas feed stream through indirect heat exchange. 
   
   
       5 . The system of  claim 1 , wherein the first precooling refrigeration system and the second precooling refrigeration system each comprise:
 at least one propane evaporator; and   a propane compressor fluidly coupled to the at least one propane evaporator and adapted to accept at least one propane vapor stream.   
   
   
       6 . The system of  claim 1 , wherein the first precooling refrigeration system and the second precooling refrigeration system are CO 2  refrigeration systems. 
   
   
       7 . The system of  claim 1 , wherein the first precooling refrigeration system comprises at least one heat exchanger that accepts at least two load streams. 
   
   
       8 . The system of  claim 5 , further comprising a first driver and a second driver, wherein the first driver drives the propane compressor of the first precooling refrigeration system, the propane compressor of the second precooling refrigeration system; and a first high pressure refrigerant compressor, and wherein the second driver drives a first medium pressure refrigerant compressor and a first low pressure refrigerant compressor. 
   
   
       9 . The system of  claim 5 , further comprising a first driver and a second driver, wherein the first driver drives the propane compressor of the first precooling refrigeration system and a first low pressure refrigerant compressor, and wherein the second driver drives the propane compressor of the second precooling refrigeration system and a first high pressure refrigerant compressor. 
   
   
       10 . The system of  claim 5 , further comprising a first driver and a second driver, wherein the first driver drives the propane compressor of the first precooling refrigeration system and the propane compressor of the second precooling refrigeration system and the second driver drives a first low pressure refrigerant compressor and a first high pressure refrigerant compressor. 
   
   
       11 . The system of  claim 10 , further comprising a third driver, wherein the third driver drives a second low pressure refrigerant compressor and a second high pressure refrigerant compressor. 
   
   
       12 . The system of  claim 8 , wherein the first driver and the second driver are gas turbines. 
   
   
       13 . The system of  claim 1 , wherein the cryogenic heat exchanger is a wound-coil heat exchanger. 
   
   
       14 . A method for liquefying natural gas, the method comprising the steps of:
 providing a natural gas feed stream;   providing a first refrigerant stream;   precooling in a first precooling refrigeration system at least the natural gas feed stream;   precooling in a second precooling refrigeration system at least the first refrigerant stream; and   vaporizing the precooled first refrigerant stream in a cryogenic heat exchanger to cool the precooled natural gas feed stream through indirect heat exchange,   
     wherein the second precooling refrigeration system precools only stream(s) having a composition different from the stream(s) precooled by the first precooling refrigeration system. 
   
   
       15 . The method of  claim 14 , wherein the natural gas feed stream and the first refrigerant stream are precooled to +60° F. to −100° F. 
   
   
       16 . The method of  claim 14 , further comprising providing a second refrigerant stream, wherein the second refrigerant stream is precooled in the first precooling refrigeration system or the second precooling refrigeration system and is vaporized to subcool the natural gas feed stream. 
   
   
       17 . The method of  claim 14 , wherein the first refrigerant stream is a mixed refrigerant stream. 
   
   
       18 . A natural gas liquefaction system for large capacity liquefaction plants, the system comprising:
 a first precooling refrigeration system that accepts one stream selected from the group consisting of:
 a natural gas feed stream, and 
 an at least one refrigerant stream; 
   a second precooling refrigeration system that accepts any remaining stream(s) not accepted by the first precooling refrigeration system and from the group consisting of:
 the natural gas feed stream, and 
 the at least one refrigerant stream; and 
   a cryogenic heat exchanger fluidly connected to the first precooling refrigeration system and the second precooling refrigeration system and adapted to accept the natural gas feed stream and the at least one refrigerant stream from the first precooling refrigeration system and the second precooling refrigeration system, wherein the at least one refrigerant stream is used to liquefy the natural gas feed stream,   
     wherein the second precooling refrigeration system accepts only stream(s) having a composition different from the stream(s) accepted by the first precooling refrigeration system. 
   
   
       19 . The system of  claim 18 , wherein the at least one refrigerant stream is a mixed refrigerant stream. 
   
   
       20 . The system of  claim 18 , wherein the at least one refrigerant stream comprises a first refrigerant stream and a second refrigerant stream.