System and method for liquefaction of natural gas

Abstract

Systems and methods are provided for the production of liquefied natural gas. At least one of the systems may include a plurality of compression assemblies in fluid communication with a precooler assembly. One compression assembly may be a part of a precooling loop and may include at least one compressor driven by a variable or fixed speed motor. Another compression assembly may be part of a liquefaction loop and may include at least one pair of compressors, each compressor driven by a respective turbine. The liquefaction loop may be fluidly coupled to a main heat exchanger utilized to liquefy at least a portion of a feed gas stream containing natural gas flowing through the main heat exchanger, thereby producing liquefied natural gas.

1 . A liquefaction system comprising:
 a first heat exchanger configured to receive a natural gas stream from a natural gas source and cool at least a first portion of the natural gas stream to liquefied natural gas;   a first compression assembly fluidly coupled to the first heat exchanger and configured to circulate a first refrigerant through the first heat exchanger to cool the first portion of the natural gas stream to the liquefied natural gas, the first compression assembly comprising
 a plurality of first refrigerant compressors configured to compress the first refrigerant; and 
 a plurality of turbines configured to drive the plurality of first refrigerant compressors; 
   a precooler assembly fluidly coupled to the first compression assembly and the first heat exchanger and configured to cool the natural gas stream and the first refrigerant compressed by the plurality of first refrigerant compressors prior to the natural gas stream entering the first heat exchanger, the precooler assembly comprising a plurality of chillers configured to transfer thermal energy from the first refrigerant and the natural gas stream to a second refrigerant; and   a second compression assembly fluidly coupled to the precooler assembly and comprising
 a plurality of second refrigerant compressors configured to compress the second refrigerant and circulate the second refrigerant to the plurality of chillers; and 
 a plurality of drivers, each driver coupled to at least one of the second refrigerant compressors and configured to drive at least one of the second refrigerant compressors; and 
   wherein the first refrigerant is a single mixed refrigerant;   the plurality of first refrigerant compressors comprises six first refrigerant compressors;   the plurality of turbines comprises six turbines, each turbine being coupled to a respective first refrigerant compressor; and   at least one turbine is an aeroderivative gas turbine, and at least one other turbine is an industrial gas turbine, wherein the first compression assembly in particular further comprises three intercoolers, each intercooler of the three intercoolers fluidly coupling two first refrigerant compressors of the six refrigerant compressors.   
     
     
         2 . The liquefaction system of  claim 1 , wherein each driver of the plurality of drivers is a fixed speed motor or a variable speed drive. 
     
     
         3 . The liquefaction system of  claim 1 , wherein:
 the plurality of second refrigerant compressors comprises two or four second refrigerant compressors; and   the plurality of drivers comprises two or four drivers, respectively, each driver being coupled to a respective second refrigerant compressor.   
     
     
         4 . The liquefaction system of  claim 1 , wherein: the second refrigerant comprises propane;
 the plurality of chillers comprises four chillers; and   each second refrigerant compressor comprises four stages, each stage of the second refrigerant compressor being in fluid communication with a respective chiller of the four chillers.   
     
     
         5 . The liquefaction system of  claim 1 , wherein the second compression assembly further comprises a plurality of aftercoolers, each aftercooler fluidly coupling a respective second refrigerant compressor with a respective chiller of the plurality of chillers. source, comprising: 
     
     
         6 . A method for producing liquefied natural gas from a natural gas source, comprising:
 feeding at least an initial portion of a natural gas stream to a plurality of chillers;   compressing a second refrigerant in at least one second refrigerant compressor, the at least one second refrigerant compressor driven by a variable speed drive or a fixed speed motor;   compressing a single mixed refrigerant in a plurality of first refrigerant compressors, each of the plurality of first refrigerant compressors being driven by a respective turbine,   transferring thermal energy from the single mixed refrigerant and the initial portion of the natural gas stream to the second refrigerant in the plurality of chillers; and   feeding a first portion of the single mixed refrigerant and a first portion of the initial portion of the natural gas stream to a first heat exchanger to cool at least a fraction of the first portion of the natural gas stream flowing therethrough to thereby produce a first portion of the liquefied natural gas;   wherein at least one turbine of the plurality of turbines is an aeroderivative gas turbine, and at least one other turbine of the plurality of turbines is an industrial gas turbine; and   an intercooler fluidly couples at least two first refrigerant compressors of the plurality of first refrigerant compressors.   
     
     
         7 . The method of  claim 6 , wherein compressing the second refrigerant in at least one second refrigerant compressor further comprises compressing the second refrigerant in a plurality of second refrigerant compressors, and each second refrigerant compressor is driven by a respective variable speed drive.