Lng process for variable pipeline gas composition

Abstract

The invention relates to a system, method and apparatus for processing natural gas in an LNG facility. A natural gas feed is introduced into a heavies removal unit. The heavies removal system includes a heavies removal column and a distillation column. The heavies removal column and the distillation column are connected via a purge/recovery line. One or more components of the natural gas feed is purged from the heavies removal column to the distillation column via the purge/recovery line to obtain a specified concentration or concentration range of heavy components feeding into the distillation column.

1 . A method for processing natural gas in an LNG facility comprising:
 introducing a natural gas feed to a heavies removal unit, wherein the heavies removal system includes a heavies removal column and a distillation column, wherein the heavies removal column and the distillation column are fluidly connected; and   purging one or more components of the natural gas feed from the heavies removal column to a methane recycle stream via the purge/recovery line to obtain a specified concentration or concentration range of heavy components feeding into the distillation column.   
     
     
         2 . The method of  claim 1 , wherein the distillation column is a high pressure demethanizer. 
     
     
         3 . The method of  claim 1 , further comprising:
 adjusting rate of the purging based in order to adjust flow rate to the distillation column.   
     
     
         4 . The method of  claim 1 , wherein the LNG facility is configured for a cascade liquefaction process. 
     
     
         5 . The method of  claim 1 , wherein the heavies removal column is downstream of the distillation column. 
     
     
         6 . The method of  claim 1 , wherein the purging removes hydrocarbons having  6  or more carbons. 
     
     
         7 . A method for processing natural gas feed during natural gas liquefaction comprising:
 introducing the natural gas feed into a heavies removal unit, wherein the heavies removal system includes a heavies removal column and a demethanizer, wherein the heavies removal column and the demethanizer are fluidly connected and wherein the heavies removal column is downstream of the demethanizer;   determining composition of the natural gas feed before it is introduced into the demethanizer; and   purging one or more heavy components of the natural gas feed from the heavies removal column to a methane recycle stream via the purge/recovery line to reduce or increase concentration of heavy components feeding into the demethanizer.   
     
     
         8 . The method of  claim 7 , further comprising:
 adjusting rate of the purging in order to adjust flow rate to the distillation column.   
     
     
         9 . The method of  claim 7 , wherein the natural gas liquefaction is a cascade liquefaction process. 
     
     
         10 . The method of  claim 7 , wherein at least three pure refrigerants are used in the cascade liquefaction process. 
     
     
         11 . The method of  claim 10 , wherein the pure refrigerants include methane, ethane, ethylene, propane, or propylene. 
     
     
         12 . The method of  claim 7 , wherein the heavy components comprise carbon molecules having 6 or more carbon atoms.