Liquefied natural gas from rich natural gas

Abstract

Rich natural gas is dried in a water scavenger unit, and then purified in a refluxed absorber. The refluxed stream for the absorber is a stream of predominantly methane condensed by cryogenic refrigeration. The refluxed absorber is operated below the critical point of methane, to allow condensation to occur. Liquefied natural gas is condensed in a cryogenic box, and then further cooled. Natural gas liquid from the refluxed absorber is stabilized for storage and transport.

Having described my invention, I claim: 
     
         1 . A liquefied natural gas (LNG) system comprising:
 a water scavenger unit fluidly connected to a rich natural gas source conduit and adapted to produce a dry natural gas;   a refluxed absorber disposed downstream of said water scavenger unit to receive the dry natural gas and form a purified natural gas and a natural gas liquid (NGL);   a refrigeration unit disposed downstream of said refluxed absorber configured to receive the purified natural gas from said refluxed absorber;   a first separator disposed downstream of said refrigeration unit configured to receive a first liquid/gas mixture from the refrigeration unit and separate liquid and gas phases into a first separator liquid outlet and a first separator gas outlet, wherein the first separator liquid outlet is fluidly connected to the refluxed absorber and the first separator gas outlet is fluidly connected to the refrigeration unit;   a pressure reduction valve disposed downstream of said refrigeration unit configured to receive liquid from said refrigeration unit;   a second separator disposed downstream of said pressure reduction valve configured to receive a second liquid/gas mixture from said pressure reduction valve and separate the liquid and gas phases into a second separator liquid outlet and a second separator gas outlet; and   an NGL upgrader disposed downstream of said refluxed absorber receiving the NGL, configured to remove a stabilizer gas from a top of said NGL upgrader and a hydrocarbon liquid from a bottom of said NGL upgrader.   
     
     
         2 . The system of  claim 1 , wherein the water scavenger unit is a molecular sieve bed. 
     
     
         3 . The system of  claim 1 , wherein the refrigeration unit is a coldbox. 
     
     
         4 . The system of  claim 3 , wherein the first separator gas outlet is fluidly connected to the coldbox. 
     
     
         5 . The system of  claim 1 , wherein the refrigeration unit is a cooler. 
     
     
         6 . The system of  claim 1 , wherein the refluxed absorber does not have a reboiler. 
     
     
         7 . The system of  claim 1 , wherein the pressure reduction valve is a Joule Thompson valve. 
     
     
         8 . A process of producing liquefied natural gas from rich natural gas, comprising:
 reducing water from a rich natural gas to form a dry natural gas;   passing the dry natural gas through a refluxed absorber to form a purified natural gas and a natural gas liquid;   cooling the purified natural gas to form a first liquid/gas mixture;   separating the first liquid/gas mixture into a methane rich liquid and a further purified natural gas;   refluxing the methane rich liquid to the refluxed absorber;   stabilizing the natural gas liquid to form a fuel gas and a purified natural gas liquid;   cooling the further purified natural gas and expanding the further purified natural gas to form a second liquid/gas mixture; and   separating the second liquid/gas mixture to form a vent gas and the liquefied natural gas.   
     
     
         9 . The process of  claim 8 , wherein the refluxed absorber does not use a reboiler. 
     
     
         10 . The process of  claim 8 , wherein the dry natural gas is formed using a molecular sieve bed. 
     
     
         11 . The process of  claim 8 , wherein the stabilizing further includes a reboiler. 
     
     
         12 . The process of  claim 8 , wherein the rich natural gas and dry natural gas are provided at conditions of 500 to 650 psi and 60 to 100° F.