System and Method for the Production of Liquefied Natural Gas

Abstract

A system and method for producing liquefied natural gas are provided. The method may include compressing a process stream containing natural gas in a compression assembly to produce a compressed process stream. The method may also include removing non-hydrocarbons from the compressed process stream in a separator, and cooling the compressed process stream with a cooling assembly to thereby produce a cooled, compressed process stream containing natural gas in a supercritical state. The method may further include expanding a first portion and a second portion of the natural gas from the cooled, compressed process stream in a first expansion element and a second expansion element to generate a first refrigeration stream and a second refrigeration stream, respectively. The method may further include cooling the natural gas in the cooled, compressed process stream to a supercritical state with the first and second refrigeration streams to thereby produce the liquefied natural gas.

We claim: 
     
         1 . A system for producing liquefied natural gas, comprising
 a compressor configured to compress a process stream containing natural gas from a natural gas source to a compressed process stream;   a cooling assembly comprising one or more heat exchangers in thermal communication with the compressed process stream, the cooling assembly configured to cool the natural gas in the compressed process stream to supercritical natural gas;   a turbo-expander fluidly coupled with the cooling assembly and configured to expand a first portion of the supercritical natural gas to generate a first refrigeration stream;   an expansion valve fluidly coupled with the cooling assembly and configured to expand a second portion of the supercritical natural gas to generate a second refrigeration stream;   a first heat exchanger fluidly coupled with the turbo-expander and configured to cool the supercritical natural gas with the first refrigeration stream; and   a second heat exchanger fluidly coupled with the expansion valve and configured cool the supercritical natural gas with the second refrigeration stream.   
     
     
         2 . The system of  claim 1 , further comprising a separator fluidly coupled with the compressor, the separator configured to receive the compressed process stream and at least partially separate water and carbon dioxide from the natural gas in the compressed process stream. 
     
     
         3 . The system of  claim 2 , wherein the cooling assembly further comprises a mechanical chiller fluidly coupled to the one or more heat exchangers, the mechanical chiller configured to provide a refrigerant to the one or more heat exchangers to cool the natural gas in the compressed process stream. 
     
     
         4 . The system of  claim 3 , further comprising:
 an internal combustion engine configured to combust a portion of the natural gas from the natural gas source to generate mechanical energy; and   a generator operatively coupled with the internal combustion engine and configured to convert the mechanical energy to electrical energy to drive the mechanical chiller.   
     
     
         5 . The system of  claim 1 , wherein the compressor comprises a plurality of compressor stages. 
     
     
         6 . The system of  claim 5 , wherein a compressor stage of the plurality of compressor stages is configured to compress the second refrigeration stream. 
     
     
         7 . The system of  claim 5 , further comprising an additional compressor fluidly coupled to a compressor stage of the plurality of compressor stages and configured to compress the first refrigeration stream. 
     
     
         8 . The system of  claim 7 , wherein the turbo-expander is operatively coupled with the additional compressor. 
     
     
         9 . A system for producing liquefied natural gas, comprising
 a compressor configured to compress a process stream containing natural gas from a natural gas source to a compressed process stream;   a separator fluidly coupled with the compressor, the separator configured to receive the compressed process stream and at least partially separate water and carbon dioxide from the natural gas in the compressed process stream;   a cooling assembly comprising a mechanical chiller in thermal communication with the compressed process stream and configured to cool the natural gas in the compressed process stream to supercritical natural gas; and   a liquefaction assembly comprising a plurality of heat exchangers in fluid communication with the compressor, the liquefaction assembly configured to cool the supercritical natural gas to liquid natural gas.   
     
     
         10 . The system of  claim 9 , wherein the liquefaction assembly further comprises a turbo-expander fluidly coupled with the cooling assembly and configured to expand a portion of the supercritical natural gas to generate a refrigeration stream. 
     
     
         11 . The system of  claim 10 , wherein at least one heat exchanger of the plurality of heat exchangers is configured to cool the supercritical natural gas with the refrigeration stream. 
     
     
         12 . The system of  claim 9 , the liquefaction assembly further comprises an expansion valve fluidly coupled with the cooling assembly and configured to expand a portion of the supercritical natural gas to generate a refrigeration stream. 
     
     
         13 . The system of  claim 12 , wherein at least one heat exchanger of the plurality of heat exchangers is configured to cool the supercritical natural gas with the refrigeration stream. 
     
     
         14 . The system of  claim 9 , further comprising one or more heat exchangers in thermal communication with the compressed process stream and fluidly coupled with the mechanical chiller, the one or more heat exchangers configured to receive a refrigerant from the mechanical chiller to cool the natural gas in the compressed process stream. 
     
     
         15 . The system of  claim 9 , further comprising:
 an internal combustion engine configured to combust a portion of the natural gas from the natural gas source to generate mechanical energy; and   a generator operatively coupled with the internal combustion engine and configured to convert the mechanical energy to electrical energy to drive the mechanical chiller.   
     
     
         16 . A system for producing liquefied natural gas, comprising
 a compressor configured to compress a process stream containing natural gas from a natural gas source to a compressed process stream;   a separator fluidly coupled with the compressor, the separator configured to receive the compressed process stream and at least partially separate water and carbon dioxide from the natural gas in the compressed process stream;   a cooling assembly comprising one or more heat exchangers in thermal communication with the compressed process stream, the cooling assembly configured to cool the natural gas in the compressed process stream to supercritical natural gas; and   a liquefaction assembly comprising a plurality of heat exchangers in fluid communication with the compressor, the liquefaction assembly configured to cool the supercritical natural gas to liquid natural gas.   
     
     
         17 . The system of  claim 16 , wherein the cooling assembly further comprises a mechanical chiller fluidly coupled to the one or more heat exchangers, the mechanical chiller configured to provide a refrigerant to the one or more heat exchangers to cool the natural gas in the compressed process stream. 
     
     
         18 . The system of  claim 16 , wherein the liquefaction assembly further comprises:
 a turbo-expander fluidly coupled with the cooling assembly and configured to expand a first portion of the supercritical natural gas to generate a first refrigeration stream; and   an expansion valve fluidly coupled with the cooling assembly and configured to expand a second portion of the supercritical natural gas to generate a second refrigeration stream.   
     
     
         19 . The system of  claim 18 , wherein the liquefaction assembly further comprises:
 a first heat exchanger fluidly coupled with the turbo-expander and configured to cool the supercritical natural gas with the first refrigeration stream; and   a second heat exchanger fluidly coupled with the expansion valve and configured cool the supercritical natural gas with the second refrigeration stream.   
     
     
         20 . The system of  claim 16 , further comprising a letdown valve fluidly coupled to the liquefaction assembly, the letdown valve configured to decrease a pressure and maintain a temperature of the liquid natural gas flowing therethrough.