Integrated liquid recovery process in lng processes

Abstract

A method for obtaining a natural gas liquid (NGL) product from a liquefied natural gas (LNG) liquefaction facility including receiving a gas feed stream at an LNG facility having an NGL recovery unit integrated therein, cooling the gas feed stream via a demethanizer of the NGL recovery unit to separate a vapor from a liquid, transferring the vapor from the NGL recovery unit to an LNG liquefaction unit and transferring the liquid to a deethanizer within the NGL recovery unit for further cooling, and obtaining an ethane product and an NGL product from the cooled liquid.

What is claimed is: 
     
         1 . A method for obtaining a natural gas liquid (NGL) product from a liquefied natural gas (LNG) liquefaction facility, the method comprising:
 receiving a gas feed stream;   cooling the gas feed stream to separate a vapor from a liquid, the gas feed stream cooled using a demethanizer, the vapor including at least light hydrocarbon components, the liquid including NGL components;   transferring the vapor to an LNG liquefaction unit;   transferring the liquid to a deethanizer; and   obtaining an ethane product and an NGL product by cooling the liquid using the deethanizer.   
     
     
         2 . A system adapted to execute the method of  claim 1 , the system comprising:
 an LNG facility operable to condense the gas feed stream to an NGL product and an LNG product; and   a NGL recovery unit integrated into the LNG facility, the NGL recovery unit operable to switch between an ethane recovery operation and an ethane rejection operation to obtain the ethane product and the NGL product.   
     
     
         3 . The method of  claim 2 , wherein the ethane product includes a predetermined ethane to propane ratio. 
     
     
         4 . The method of  claim 2 , further comprising cooling, via the deethanizer, the liquid to a temperature sufficient to achieve a desired ethane to propane ratio when the NGL recovery unit is performing an ethane recovery operation. 
     
     
         5 . The method of  claim 4 , further comprising transporting the ethane product to a pipeline for distribution when the NGL recovery unit is performing the ethane recovery operation. 
     
     
         6 . The method of  claim 2 , further comprising cooling, via the deethanizer, the liquid to a temperature sufficient to reduce propane loss when the NGL recovery unit is performing an ethane rejection operation. 
     
     
         7 . The method of  claim 6 , further comprising transferring ethane obtained from the deethanizer into the LNG product when the NGL recovery unit is performing the ethane rejection operation. 
     
     
         8 . The method of  claim 6 , wherein a majority of ethane present in the gas feed stream is removed when the NGL recovery unit is performing the ethane rejection operation. 
     
     
         9 . The method of  claim 2 , wherein the NGL recovery unit can switch between an ethane recovery operation and an ethane rejection operation without changing equipment. 
     
     
         10 . The method of  claim 1 , further comprising separating the vapor from the demethanizer into a first vapor stream and a second vapor stream. 
     
     
         11 . The method of  claim 10 , further comprising:
 deep subcooling the first vapor stream; and   returning subcooled vapor to the demethanizer as a reflux stream.   
     
     
         12 . The method of  claim 10 , further comprising:
 expanding the second vapor stream via isentropic expansion in a turboexpander to partially liquefy the second vapor stream into a two-phase stream; and   returning the two-phase stream to the demethanizer as a top feed.   
     
     
         13 . The method of  claim 11 , further comprising adjusting the reflux stream to the demethanizer to optimize process efficiency. 
     
     
         14 . The method of  claim 1 , wherein a light hydrocarbon components transferred to the LNG liquefaction unit includes at least methane. 
     
     
         15 . The method of  claim 1 , wherein the NGL product obtained from the deethanizer includes propane and heavy hydrocarbon components (C6+). 
     
     
         16 . The method of  claim 1 , further comprising sending the NGL product to an NGL fractionation unit within the LNG liquefaction facility. 
     
     
         17 . The method of  claim 1 , wherein transferring the liquid to the deethanizer includes sending the liquid from one or more side reboilers to the deethanizer.