Methods and apparatus for liquefaction of natural gas and products therefrom

Abstract

A method for cooling natural gas with a refrigerant, one non-limiting embodiment which includes: (A) compressing and cooling the refrigerant to a first pressure to form a compressed refrigerant; (B) splitting the compressed refrigerant into a first stream and a second stream both at the first pressure; (C) cooling the first stream to form a cooled first stream; (D) expanding the cooled first stream to a first expansion pressure to form an expanded first stream; (E) compressing the second stream to a second pressure higher than the first pressure, forming a higher pressure second stream; (F) cooling the higher pressure second stream to form a cooled second stream; (G) expanding the cooled second stream to a second expansion pressure to form an expanded second stream; and, (H) Cooling the natural gas with the expanded first stream and expanded second stream, forming a cooled natural gas stream.

1 . A method for cooling natural gas with a refrigerant, the method comprises:
 (A) Compressing and cooling the refrigerant to a first pressure to form a compressed refrigerant;   (B) Splitting the compressed refrigerant into a first stream and a second stream both at the first pressure;   (C) Cooling the first stream to form a cooled first stream;   (D) Expanding the cooled first stream to a first expansion pressure to form an expanded first stream;   (E) Compressing the second stream to a second pressure higher than the first pressure, forming a higher pressure second stream;   (F) Cooling the higher pressure second stream to form a cooled second stream;   (G) Expanding the cooled second stream to a second expansion pressure to form an expanded second stream; and,   (H) Cooling the natural gas with the expanded first stream and expanded second stream, forming a cooled natural gas stream.   
     
     
         2 . The method of  claim 1 , wherein prior to step (H) the natural gas is first pretreated to remove at least one selected from the group consisting of non-hydrocarbon impurities, nitrogen, carbon dioxide, hydrogen sulfide, carbonyl sulfide, mercaptans water, and helium. 
     
     
         3 . The method of  claim 1 , wherein prior to step (H) the natural gas is first pretreated to reduce the quantity of C6+ hydrocarbon components. 
     
     
         4 . The method of  claim 1 , wherein in step (B) the refrigerant is split into a third or more streams. 
     
     
         5 . The method of  claim 1 , wherein at least one of the first expansion pressure or the second expansion pressure is less than 1.18 MPa. 
     
     
         6 . The method of  claim 1 , wherein the natural gas is split into multiple portions, each portion cooled in parallel with the other portions. 
     
     
         7 . The method of  claim 1 , wherein a portion of the cooled natural gas stream is used to pretreat the natural gas. 
     
     
         8 . The method of  claim 1 , wherein in step (H) there is formed a heated first stream, a heated second stream, the method further comprising combining, compressing and cooling the heated first stream and the heated second stream to form the refrigerant for use in step (A). 
     
     
         9 . A method for cooling natural gas with a refrigerant, the method comprises:
 (A) Compressing and cooling the refrigerant to a first pressure to form a compressed refrigerant;   (B) Splitting the refrigerant into a first stream and a second stream both at the first pressure;   (C) Cooling the first stream to form a cooled first stream;   (D) Expanding the cooled first stream to a first expansion pressure to form an expanded first stream;   (E) Compressing second stream to a second pressure higher than the first pressure forming a higher pressure second stream;   (F) Cooling the higher pressure second stream to form a cooled second stream;   (G) Expanding the cooled second stream to form a expanded second stream at a second expansion pressure; and,   (H) Cooling the natural gas with the expanded first stream and the expanded second stream to form a cooled natural gas stream, wherein the natural gas is at a pressure of at least 5.5 MPa;   wherein at least step (H) is carried out in at least one aluminum plate heat exchanger.   
     
     
         10 . The method of  claim 9 , wherein in step (H) the pressure is at least 6 MPa. 
     
     
         11 . The method of  claim 9 , wherein prior to step (H) the natural gas is first pretreated to remove at least one selected from the group consisting of non-hydrocarbon impurities, nitrogen, carbon dioxide, hydrogen sulfide, carbonyl sulfide, mercaptans water, and helium. 
     
     
         12 . The method of  claim 9 , wherein prior to step (H) the natural gas is first pretreated to reduce the quantity of C6+ hydrocarbon components. 
     
     
         13 . The method of  claim 9 , wherein in step (B), the refrigerant is split into at least the first stream, the second stream and a third stream. 
     
     
         14 . The method of  claim 9 , wherein at least one of the first expansion pressure or the second expansion pressure is less than 1.15 MPa. 
     
     
         15 . The method of  claim 9 , wherein the aluminum plate heat exchanger comprises multiple cores operating in parallel and the natural gas is split into multiple portions, each portion cooled in one of the cores. 
     
     
         16 . The method of  claim 9 , wherein a portion of the cooled natural gas stream is used to pretreat the natural gas. 
     
     
         17 . The method of  claim 9 , wherein in step (H) there is formed a heated first stream, a heated second stream, the method further comprising combining, compressing and cooling the heated first stream and the heated second stream to form the refrigerant for use in step (A). 
     
     
         18 . A method for cooling natural gas with a refrigerant, the method comprises:
 (A) Compressing and cooling the refrigerant to a first pressure to form a compressed refrigerant;   (B) Splitting the refrigerant into a first stream and a second stream both at the first pressure;   (C) Cooling the first stream to form a cooled first stream;   (D) Expanding the cooled first stream to form an expanded first stream at a first expansion pressure;   (F) Compressing second stream to a second pressure higher than the first pressure forming a higher pressure second stream;   (G) Cooling the higher pressure second stream to form a cooled second stream;   (H) Expanding the cooled second stream to the expansion pressure to form a expanded second stream; and,   (H) Cooling the natural gas with the cooled first stream and the cooled second stream to form a cooled natural gas stream, wherein the natural gas is at a pressure less than 5.5 MPa;   wherein, step (H) is carried out in at least one heat exchanger selected from the group comprising a spiral wound heat exchanger, a printed circuit heat exchanger and a spool wound heat exchanger.   
     
     
         19 . The method of  claim 18 , wherein in step (H) the pressure is less than 5 MPa. 
     
     
         20 . The method of  claim 18 , wherein in step (H) the pressure is less than 4.5 MPa. 
     
     
         21 . A method for cooling natural gas with a refrigerant, the method comprises:
 (A) Compressing and cooling the refrigerant to a first pressure to form a compressed refrigerant;   (B) Splitting the compressed refrigerant into a first stream and a second stream both at the first pressure;   (C) Cooling the first stream to form a cooled first stream;   (D) Expanding the cooled first stream to a first expansion pressure to form an expanded first stream;   (E) Compressing the second stream to a second pressure higher than the first pressure, forming a higher pressure second stream;   (F) Cooling the higher pressure second stream to form a cooled second stream;   (G) Expanding the cooled second stream to a second expansion pressure to form an expanded second stream; and,   (H) Cooling the natural gas with the expanded first stream and the expanded second stream forming a heated second stream;   wherein at least one of the first expansion pressure and the second expansion pressure are less than 1.18 MPa.   
     
     
         22 . The method of  claim 9 , wherein at least one of the first expansion pressure or the second expansion pressure is less than 1.17 MPa. 
     
     
         23 . The method of  claim 9 , wherein at least one of the first expansion pressure or the second expansion pressure is less than 1.16 MPa. 
     
     
         24 . A method for processing natural gas comprising:
 (A) Providing a first natural gas vapor stream to a fractionation tower;   (B) Providing a second natural gas stream to the fractionation tower as a reflux stream; and,   (C) Separating the first natural gas vapor stream into a heavy component liquid stream and a light component vapor stream.