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 plant for LNG liquefaction, the plant comprising:
 a natural gas feed stream;   a heat exchanger;   a first expander;   a first refrigerant compressor;   a second expander,   wherein the plant is configured such that the heat exchanger provides heat exchange between the natural gas feed stream and a compressed and cooled refrigerant stream to heat the compressed and cooled refrigerant stream,   wherein the plant is configured such that, after the heat exchange in the heat exchanger, the compressed and cooled refrigerant stream is split into a first refrigerant portion and a second refrigerant portion,   wherein the plant is configured such that the heat exchanger uses the second refrigerant portion to cool the natural gas feed stream,   wherein the second refrigerant portion is heated in the heat exchanger to produce a warmed refrigerant stream,   wherein the plant is configured such that the first expander expands the first refrigerant portion to produce an expanded first refrigerant stream portion,   wherein the plant is configured such that the heat exchanger uses the expanded first refrigerant stream portion to cool the natural gas feed stream,   wherein the expanded first refrigerant stream portion is heated in the heat exchanger to produce a first warm LNG vapor stream,   wherein the plant is configured such that the first refrigerant compressor compresses the first warm LNG vapor stream,   wherein the plant is configured such that the warmed refrigerant stream is expanded to produce an expanded second refrigerant stream portion,   wherein the plant is configured such that the heat exchanger uses the expanded second refrigerant stream portion, and   wherein the expanded second refrigerant stream portion is heated in the heat exchanger to produce a second warm LNG vapor stream.   
     
     
         2 . The plant of  claim 1 , wherein the plant is configured such that a volumetric flow ratio of the first refrigerant portion to the second refrigerant portion is 3:1. 
     
     
         3 . The plant of  claim 1 , further comprising a first compressor, wherein the plant is configured such that the second warm LNG vapor stream is compressed in the first compressor to produce a compressed second LNG vapor stream. 
     
     
         4 . The plant of  claim 3 , wherein the first compressor is mechanically coupled to the second expander. 
     
     
         5 . The plant of  claim 3 , further comprising a second compressor, wherein the plant is configured such that the compressed second LNG vapor stream is compressed in the second compressor to form a second LNG vapor stream. 
     
     
         6 . The plant of  claim 5 , wherein the second compressor is mechanically coupled to the first expander. 
     
     
         7 . The plant of  claim 5 , wherein the plant is configured such that the compressed second LNG vapor stream is cooled prior to compressing the compressed second LNG vapor stream in the second compressor. 
     
     
         8 . The plant of  claim 5 , further comprising a second refrigerant compressor, wherein the plant is configured such that the second LNG vapor stream is compressed with the second refrigerant compressor. 
     
     
         9 . The plant of  claim 8 , where the second refrigerant compressor forms a first stage in a refrigerant compressor system. 
     
     
         10 . The plant of  claim 9 , wherein the first refrigerant compressor forms a second stage or a third stage of the refrigerant compressor system. 
     
     
         11 . The plant of  claim 1 , wherein the plant is configured such that a gas stream from produced LNG is used in the heat exchanger for heat exchange with the natural gas feed stream. 
     
     
         12 . The plant of  claim 1 , further comprising:
 a compressor driver;   a waste heat exchanger; and   an expander,   wherein the plant is configured such that the first refrigerant compressor is driven with the compressor driver,   wherein the plant is configured such that a refrigerant stream is compressed and cooled to form the compressed and cooled refrigerant stream using the first refrigerant compressor;   wherein the plant is configured such that waste heat produced in response to driving the first refrigerant compressor is provided as a waste heat working fluid to in the waste heat exchanger;   wherein the plant is configured such that the waste heat working fluid is expanded, using an expander, to produce work, and   wherein the plant is configured such that the second warm LNG vapor stream is compressed using the work.   
     
     
         13 . The plant of  claim 12 , wherein the waste heat working fluid comprises a high-pressure hydrocarbon liquid relative to atmospheric pressure, wherein the plant is configured such that a high-pressure hydrocarbon liquid is vaporized and superheated using the waste heat to form a vaporized and superheated high pressure hydrocarbon, and wherein the plant is configured such that the vaporized and superheated high pressure hydrocarbon is directed to the expander. 
     
     
         14 . The plant of  claim 13 , wherein the compressor driver is a gas turbine, and wherein the plant is configured such that the waste heat is from a turbine exhaust. 
     
     
         15 . The plant of  claim 12 , wherein the waste heat working fluid is a high-pressure hydrocarbon fluid. 
     
     
         16 . The plant of  claim 1 , wherein the plant is configured such that the natural gas feed stream is liquefied in the heat exchanger to produce LNG. 
     
     
         17 . The plant of  claim 16 , further comprising a storage tank downstream of the heat exchanger, wherein the plant is configured such that the LNG is stored in the storage tank, wherein the plant is configured such that a gas stream from the storage tank is directed to the heat exchanger. 
     
     
         18 . The plant of  claim 16 , further comprising a third compressor and a compressor driver, wherein the plant is configured such that the gas stream from the heat exchanger is passed to the third compressor, wherein the plant is configured such that the gas stream is compressed in the third compressor into a fuel gas stream, and wherein the plant is configured such that the fuel gas stream is used in the compressor driver to drive the first refrigerant compressor. 
     
     
         19 . The plant of  claim 1 , wherein the heat exchanger is a cold box. 
     
     
         20 . The plant of  claim 1 , wherein the plant is configured such that the natural gas feed stream is treated to remove one or more components in a natural gas treatment system before the heat exchange between the natural gas feed stream and the compressed and cooled refrigerant stream.