Process for producing liqefied natural gas from high co2 natural gas

Abstract

A process for producing LNG from high CO 2 natural gas. The process includes: separating methane from a hydrocarbon stream containing CO 2 to produce a methane-depleted hydrocarbon stream; subjecting the methane-depleted hydrocarbon stream to at least one separation process; and feeding at least one recycle stream from the at least one separation processes into the step for separating methane. The at least one separation process is selected from the group consisting of deethanizing, depropanizing, debutanizing and CO 2 separating.

1 ) A process for producing LNG from high-CO 2  natural gas, comprising the steps of:
 separating methane from a hydrocarbon feed stream containing CO 2  to produce a methane-depleted hydrocarbon stream;   subjecting the methane-depleted hydrocarbon stream to at least one separation process to produce a hydrocarbon recycle stream; and   combining the hydrocarbon recycle stream with the hydrocarbon feed stream prior to separating methane from the hydrocarbon feed stream,   
       wherein the at least one separation process is selected from the group consisting of deethanizing, depropanizing, debutanizing and CO 2  separating. 
     
     
         2 ) The process according to  claim 1 , wherein the step of separating methane comprises:
 conducting a full liquid reflux on the separated methane vapor product.   
     
     
         3 ) The process according to  claim 1 , wherein the step of separating methane comprises:
 scrubbing and removing aromatics and heavy hydrocarbons from the hydrocarbon stream containing CO 2 .   
     
     
         4 ) The process according to  claim 1 , further comprising the step of:
 passing the methane to a liquefaction process.   
     
     
         5 ) The process according to  claim 1 , further comprising the step of:
 passing the methane to a main cryogenic heat exchanger of a liquefaction plant.   
     
     
         6 ) The process according to  claim 1 , wherein the hydrocarbon recycle stream comprises fractionated gas components passed from the at least one separation process. 
     
     
         7 ) The process according to  claim 1 , wherein the hydrocarbon recycle stream comprises a hydrocarbon stream from a front slug catcher. 
     
     
         8 ) The process according to  claim 1 , wherein the methane contains less than about 100 ppm CO 2  and less than about 3 ppm H 2 S. 
     
     
         9 ) The process according to  claim 1 , wherein the step of separating the methane from the hydrocarbon stream is conducted at a pressure in the range of about 38 to about 45 bar, and at a temperature in the range of about −91° C. to about −84° C. 
     
     
         10 ) The process according to  claim 1 , wherein the deethanizing is conducted at a pressure in the range of about 35 to about 44 bar, and at a temperature in the range of about 4, C at about 35° C. 
     
     
         11 ) The process according to  claim 1 , wherein the depropanizing is conducted at a pressure in the range of about 17 to about 27 bar, and at a temperature in the range of about −2° C. to about 67° C. 
     
     
         12 ) The process according to  claim 1 , wherein the debutanizing is conducted at a pressure in the range of about 6 to about 12 bar, and at a temperature in the range of about 40° C. to about 78° C. 
     
     
         13 ) The process according to  claim 1 , wherein the step of CO 2  separating is conducted at a pressure in the range of about 28 to about 32 bar, and at a temperature in the range of about −6° C. to about −2° C. 
     
     
         14 ) The process according to  claim 1 , wherein the step of subjecting the methane-depleted hydrocarbon stream to at least one separation process comprises blending back at least one principal overhead product with the methane for heating value adjustment. 
     
     
         15 ) The process according to  claim 1 , wherein the step of subjecting the methane-depleted hydrocarbon stream to at least one separation process comprises feeding at least one principal overhead product stream to a fractionation train. 
     
     
         16 ) The process according to  claim 1 , wherein the step of subjecting the methane-depleted hydrocarbon stream to at least one separation process comprises feeding a principal overhead product of ethane and carbon dioxide to an azeotrope separation process. 
     
     
         17 ) The process according to  claim 1 , wherein the step of subjecting the methane-depleted hydrocarbon stream to at least one separation process comprises removing H 2 S via adsorption from the methane-depleted hydrocarbon stream. 
     
     
         18 ) The process according to  claim 17 , wherein the step of removing H 2 S is conducted at a pressure in the range of about 1.7 to 27 bar, and at a temperature in the range of about −2° C. to 67° C. 
     
     
         19 ) The process according to  claim 1 , wherein the step of subjecting the methane-depleted hydrocarbon stream to at least one separation process comprises membrane-separating CO 2  from the methane-depleted hydrocarbon stream. 
     
     
         20 ) The process according to  claim 19 , wherein the step of membrane-separating CO 2  is conducted to produce a stream containing about 98 vol % CO 2 .