Method for adjusting heating value of lng

Abstract

Systems and methods for adjusting the heating value of liquefied natural gas (“LNG”) are provided. LNG can be apportioned into at least two portions. A first portion can be warmed to provide a vapor-liquid mixture which can be separated in a first separator to provide a first vapor and a first liquid. The first liquid can be separated to provide ANGL and a second vapor. The first vapor can be compressed and mixed with the second vapor to provide a first effluent. At least a portion of the first effluent can be used to heat the first portion. At least a portion of the first effluent can be used as a first reflux in the first separator. At least a portion of the first effluent can be mixed with a second portion of the LNG to provide an adjusted LNG.

1 ) A method for adjusting the heating value and Wobbe index of liquefied natural gas, comprising:
 apportioning liquefied natural gas at a first temperature into at least a first portion and a second portion;   heating the first portion to provide a first vapor-liquid mixture having a second temperature;   selectively separating, under a first reflux, the first vapor-liquid mixture to provide a first vapor and a first liquid;   compressing at least a portion of the first vapor comprising methane to provide a compressed vapor;   selectively separating the first liquid to provide a second vapor comprising methane and a second liquid comprising NGL; and   combining the second vapor and the compressed vapor to form a first effluent.   
     
     
         2 ) The method of  claim 1 , further comprising combining the second portion of the liquefied natural gas with the first effluent to provide a first product. 
     
     
         3 ) The method of  claim 2 , further comprising vaporizing the first product. 
     
     
         4 ) The method of  claim 1 , wherein the second vapor is expanded and the first vapor is compressed using a turboexpander. 
     
     
         5 ) The method of  claim 1 , wherein at least a portion of the first effluent is used as a heat transfer fluid to warm the first portion of the liquefied natural gas. 
     
     
         6 ) The method of  claim 1 , wherein the first reflux comprises at least a portion of the first effluent. 
     
     
         7 ) The method of  claim 1 , wherein the first temperature is −160° C. or lower. 
     
     
         8 ) The method of  claim 1 , wherein the second temperature is greater than −160° C. and less than −88° C. 
     
     
         9 ) A method for adjusting the heating value of liquefied natural gas comprising:
 apportioning the liquefied natural gas at a first temperature into a first portion and a second portion;   heating the first portion to provide a first intermediate at a second temperature;   heating the first intermediate to provide a first vapor-liquid mixture at a third temperature;   selectively separating the first vapor-liquid mixture to provide a first vapor and a first liquid;   selectively separating the first liquid to provide a second vapor and a natural gas liquid product;   cooling and selectively separating the first vapor to provide a third vapor and a second liquid;   compressing the third vapor to provide a compressed vapor;   combining the second vapor and the compressed vapor to provide a first effluent; and   cooling the first effluent.   
     
     
         10 ) The method of  claim 9 , further comprising combining the second liquid and the second portion of the liquefied natural gas to provide a second effluent. 
     
     
         11 ) The method of  claim 9 , further comprising combining the second effluent with the first effluent to provide a first product. 
     
     
         12 ) The method of  claim 11 , further comprising vaporizing the first product. 
     
     
         13 ) The method of  claim 9 , wherein at least a portion of the first vapor is used as a heat transfer fluid to warm the first portion of the liquefied natural gas feed. 
     
     
         14 ) The method of  claim 9 , wherein at least a portion of the first effluent is used as a heat transfer fluid to warm the first intermediate. 
     
     
         15 ) The method of  claim 9 , wherein the first temperature is −160° C. or lower. 
     
     
         16 ) The method of  claim 9 , wherein the second temperature is greater than −160° C. and less than −88° C. 
     
     
         17 ) The method of  claim 9 , wherein the third temperature is greater than −160° C. and less than −88° C. 
     
     
         18 ) A system for adjusting the heating value and Wobbe Index of liquefied natural gas, comprising:
 a heating zone for increasing the temperature of at least a portion of a liquefied natural gas above the boiling point of methane and below the boiling point for C 2  and heavier hydrocarbons;   a first separation zone having an essentially liquid methane first reflux for separating the vaporized methane from liquid C 2  and heavier hydrocarbons;   a second separation zone for separating residual methane from the liquid C 2  and heavier hydrocarbons to provide an NGL liquid product and a methane rich effluent; and   a mixing zone for mixing a bypassed portion of the liquefied natural gas and the methane rich effluent to provide an adjusted liquefied natural gas product having a heating value suitable for pipeline transfer.   
     
     
         19 ) The system of  claim 18 , wherein the heating zone comprises an interchanger for exchanging heat between the methane rich first effluent and the liquefied natural gas.