Method and apparatus for the liquefaction of natural gas

Abstract

A method for the liquefaction of natural gas, comprising: taking unpurified natural gas from a gas well; pre-treating the gas for removing impurities; performing a first compression stage; performing a first heat exchange stage; performing a second compression stage; performing a second heat exchange stage; performing a third compression stage; performing a third heat exchange stage; performing an additional regeneration heat exchange stage; performing a first main independent heat exchange cycle; performing a second main heat exchange cycle; passing the gas through a Joule-Thomson valve; sending the liquefied gas to storage; injecting the portion of the gas in the gaseous state into the second main heat exchange stage; and the remaining gas in the gaseous state is injected into the first main heat exchange stage.

I Claim: 
     
         1 . A method for the liquefaction of natural gas, comprising:
 taking unpurified natural gas from a gas well;   pre-treating the gas for removing impurities:   performing a first compression stage;   performing a first heat exchange stage;   performing a second compression stage;   performing a second beat exchange stage;   performing a third compression stage;   performing a third heat exchange stage;   performing an additional regeneration heat exchange stage;   performing a first main independent heat exchange cycle;   performing a second main heat exchange cycle;   passing the gas through a Joule-Thomson valve;   sending the liquefied gas to storage;   injecting the portion of the gas in the gaseous state into the second main heat exchange stage; and the remaining gas in the gaseous state is injected into the first main heat exchange stage,   
     
     
         2 . The method for the liquefaction of natural as in accordance with  claim 1 , wherein during the pretreatment stage, carbon dioxide and/or nitrogen is removed from the natural gas. 
     
     
         3 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the first compression stage the natural gas is compressed from 10/11 bar to around 30/35 bar. 
     
     
         4 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the first heat exchange stage the temperature of the gas is reduced from 140/150° C. to 40/45° C. 
     
     
         5 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the second compression stage the natural gas is compressed from around 30/35 bar to around 90/95 bar. 
     
     
         6 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the second heat exchange stage the temperature of the gas is reduced from 140/150° C. to ° C. ° C. 
     
     
         7 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the third compression stage the natural gas is compressed from around 90/95 bar to around 245/250bar. 
     
     
         8 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the third heat exchange stage the temperature of the gas is reduced from 140/145° C. to 40/45° C. 
     
     
         9 . The method for the liquefaction of natural gas in accordance with chum  1 , wherein during the additional regeneration heat exchange stage the temperature of the gas is reduced from 40/45° C. to 7/10° C. 
     
     
         10 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein the first main independent heat exchange cycle is an isobaric cycle to reduce the temperature of the gas from 7/10° C. to −40/−45° C. 
     
     
         11 . The method for the liquefaction of natural gas in accordance with  claim 1 , wherein during the second main beat exchange isobaric cycle the temperature of the gas is reduced from −40/−45° C. to −75/−80° C. 
     
     
         12 . The method for the liquefaction of natural vas in accordance with  claim 1 , wherein the gas is passed through a Joule-Thomson valve reducing its temperature to −150/−155° C. and reducing its pressure to 2 bar. 
     
     
         13 . A method for the liquefaction of natural gas, comprising:
 taking unpurified natural gas from a gas well;   pre-treating the gas for removing impurities;   performing a first compression stave for compressing the natural gas from around 10/11 bar to around 30/35 bar (and in which the temperatures rise from 30/35° C. to 140/150° C.);   performing a first heat exchange stage for cooling down the temperature of the gas from 140/150° C. to 40/45° C.;   performing a second compression stage for compressing the natural gas from around 30/35 bar to around 90/95 bar (and during which the temperatures rise from 40/45° C. to 140/150° C.);   performing a second heat exchange stage for cooling down the temperature of the gas from 140/150° C. to 40/45° C.;   performing a third compression stage for compressing the natural gas from around 90/95 bar to around 245/250 bar (and during which the temperatures rise from 40/45° C. to 140/145° C.);   performing a third heat exchange stage for cooling down the temperature of the gas from 140/145° C. to 40/45° C.;   performing an additional regeneration heat exchange stage to cool down the temperature of the gas from 40/45° C. to 7/10° C.;   performing a first main independent heat exchange cycle to cool down the temperature of the gas from 7/10° C. to −40/−45° C. while pressure is kept at 250 bar;   performing a second main heat exchange cycle to cool down the temperature of the gas from −40/−45° C. to −75/−80° C. while pressure is kept at 250 bar;   passing the gas at 250 bar and −75/−80° C. through a Joule-Thomson valve allowing the stream to expand thereby reducing its temperature to −150/−155° C. and reducing its pressure to 2 bar;   sending the portion of the gas already liquefied to storage:   injecting the portion of the gas in the gaseous state into the second main heat exchange stage (to help in the cooling process described above, increasing its temperature from −150/−155° C. to −60/−65° C. , and the remaining gas in the gaseous state at −60/−65° C. is injected into the first main heat exchange stage to help in the cooling process described above:   
     
     
         14 . A method for the liquefaction of natural gas, comprising:
 a pre-treating step for removing impurities such as carbon dioxide, nitrogen, etc., from the natural gas flow taken from a source of unpurified natural gas;   a first compression stage for compressing the natural gas from around 11 bar to around 33 bar, and in which the temperatures rise from 36° C. to 148° C.;   a first heat exchange stage for cooling down the temperature of the gas from 148° C. to 40° C.;   a second compression stage for compressing the natural gas from around 33 bar to around 95 bar, and in which the temperatures rise from 40° C. to 148° C.;   a second heat exchange stage for cooling down the temperature of the gas from 149° C. to 40° C.;   a third compression stage for compressing the natural gas from around 95 bar to around 250 bar, and in which the temperatures rise from 40° C. to 136° C.;   a third heat exchange stage for cooling, down the temperature of the gas from 136° C. to 40° C.;   at 250 bar, a new heat exchange stage that is part of a regeneration cycle cools down the temperature of the gas from 40° C. to 7° C.;   a first main independent heat exchange cycle cools down the temperature of the gas from 7° C. to −47° C., while pressure is kept at 250 bar;   a second main heat exchange cycle cools down the temperature of the gas from −47° C. to −77° C. while pressure is kept at 250 bar:   at 250 bar and −77° C., the gas passes through a Joule-Thomson valve allowing the stream to expand thereby reducing its temperature to −151° C. and reducing its pressure to 2 bar;   at −151° C. and 2 bar, a portion of the mass of gas is liquefied and sent to storage and the portion of the mass of gas remains in the gaseous state and is injected into the second main heat exchange stage to help in the cooling. process described above, increasing its temperature from −151° C. to −60° C.; and the remaining gas in the gaseous state at −60° C. is injected into the first main heat exchange stage to help in the cooling process described above.