Systems and Methods for LNG Refrigeration and Liquefaction

Abstract

A LNG liquefaction plant system includes concurrent power production, wherein the refrigeration content of the refrigerant or SMR is used to liquefy and sub-cool a natural gas stream in a cold box or cryogenic exchanger. For concurrent power production, the system uses waste heat from refrigerant compression to vaporize and superheat a waste heat working fluid that in turn drives a compressor for refrigerant compression. The refrigerant may be an external SMR or an internal LNG refrigerant working fluid expanded and compressed by a twin compander arrangement.

What is claimed is: 
     
         1 . A LNG liquefaction plant system comprising:
 a cryogenic exchanger including multiple stages of heat exchange and configured to receive a refrigerant working fluid for the multiple stages of heat exchange ;   a compressor assembly including a compressor driver coupled to at least a first compressor;   a waste heat recovery unit including a waste heat working fluid and a heat exchanger, the waste heat recovery unit configured to receive a waste heat from the compressor driver to transfer heat to the waste heat working fluid via the heat exchanger; and   an expander configured to receive the heated waste heat working fluid and thereby drive a second compressor of the compressor assembly.   
     
     
         2 . The LNG liquefaction plant system of  claim 1 , further comprising a natural gas treatment system coupled before the cryogenic exchanger. 
     
     
         3 . The LNG liquefaction plant system of  claim 1 , further comprising:
 a storage tank to receive LNG from the cryogenic exchanger;   a LNG vapor conduit coupled to the storage tank to direct a LNG vapor from the storage tank to the cryogenic exchanger;   a compressor to receive the LNG vapor from the cryogenic exchanger and compress the LNG vapor into a fuel gas stream; and   a fuel gas conduit to coupled to the compressor driver to direct fuel gas stream to the compressor driver.   
     
     
         4 . The LNG liquefaction plant system of  claim 1 , wherein the compressor driver is a gas turbine and the waste heat is a turbine exhaust. 
     
     
         5 . The LNG liquefaction plant system of  claim 1 , wherein the refrigerant working fluid is an external single mixed refrigerant. 
     
     
         6 . The LNG liquefaction plant system of  claim 1 , wherein the waste heat working fluid is a high pressure hydrocarbon liquid to be vaporized and superheated in the heat exchanger by the compressor drive waste heat in an organic Rankine cycle. 
     
     
         7 . The LNG liquefaction plant system of  claim 6 , wherein the composition of the high pressure hydrocarbon is adjustable based on ambient temperature. 
     
     
         8 . The LNG liquefaction plant system of  claim 2 , further comprising a conduit coupled between a waste heat working fluid conduit and the natural gas treatment system to provide a component extracted from a natural gas stream to the waste heat working fluid. 
     
     
         9 . The LNG liquefaction plant system of  claim 1 , wherein the refrigerant working fluid is an internal LNG refrigerant working fluid, and further comprising:
 an expander configured to expand the internal LNG refrigerant working fluid for the multiple stages of heat exchange.   
     
     
         10 . The LNG liquefaction plant system of  claim 9 , further comprising a second expander for multi-stage expansion of the internal LNG refrigerant working fluid. 
     
     
         11 . The LNG liquefaction plant system of  claim 10 , wherein each of the expanders include compressors coupled thereto for multi-stage expansion and compression of the internal LNG refrigerant working fluid. 
     
     
         12 . The LNG liquefaction plant system of  claim 10 , further comprising a conduit split disposed before the expanders to provide a first portion of the internal LNG refrigerant working fluid and a second portion of the internal LNG refrigerant working fluid at a ratio of  3 : 1 . 
     
     
         13 . The LNG liquefaction plant system of  claim 9 , wherein the internal LNG refrigerant working fluid is a LNG vapor or boil off gas. 
     
     
         14 . A method for LNG liquefaction comprising:
 providing a natural gas feed stream;   providing a compressed and cooled refrigerant stream;   producing an expanded refrigerant stream in response to the heat exchange;   compressing the expanded refrigerant stream into a compressed and cooled refrigerant stream;   producing waste heat in response to the compression;   providing the waste heat to a waste heat working fluid for waste heat exchange;   driving compression of the expanded refrigerant stream in response to the waste heat exchange; and   liquefying the natural gas feed stream in response to heat exchange to produce LNG.   
     
     
         15 . The method of  claim 14 , further comprising:
 directing a gas stream from the produced LNG; and   using the gas stream for heat exchange to supplement the natural gas feed stream to LNG liquefaction.   
     
     
         16 . The method of  claim 14 , further comprising:
 vaporizing and superheating a high pressure hydrocarbon liquid using exhaust from a gas turbine; and   directing the vaporized and superheated high pressure hydrocarbon liquid to an expander that drives a compressor shaft.   
     
     
         17 . The method of  claim 14 , further comprising providing an external SMR to multiple stages of heat exchange in a cold box 
     
     
         18 . The method of  claim 14 , further comprising providing an internal LNG refrigerant working fluid to multiple stages of heat exchange in a cold box. 
     
     
         19 . The method of  claim 18 , further comprising, after flowing through the cold box, splitting a stream of the internal LNG refrigerant working fluid into first and second stream portions. 
     
     
         20 . The method of  claim 19 , further comprising expanding the first and second stream portions with a twin compander arrangement prior to directing the first and second stream portions back into the cold box, and compressing at least one of the first and second stream portions with the twin compander arrangement after flowing the first and second streams through the cold box and before flowing the first and second stream portions to a refrigerant compressor.