Phase implementation of natural gas liquid recovery plants

Abstract

Embodiments relate generally to systems and methods for operating a natural gas liquids plant in ethane rejection and in ethane recovery. A natural gas liquid plant may comprise an absorber configured to produce an ethane rich bottom stream and an ethane depleted vapor stream; a stripper fluidly coupled to the absorber configured to, during ethane rejection, fractionate the ethane rich bottom stream from the absorber into an ethane overhead product and a propane plus hydrocarbons product, and configured to, during ethane recovery, fractionate the ethane rich bottom stream into an ethane plus NGL stream and an overhead vapor stream; and an exchanger configured to, during ethane recovery, counter-currently contact the ethane rich bottom stream from the absorber with the ethane depleted vapor stream from the absorber, thereby heating the vapor stream and chilling the ethane rich bottom stream before the ethane rich bottom stream is fed to the stripper.

What is claimed is: 
     
         1 . A natural gas liquid plant configured to operate in either ethane rejection or ethane recovery, the plant comprising:
 an absorber configured to produce an ethane rich bottom stream and an ethane depleted vapor stream;   a stripper fluidly coupled to the absorber,
 wherein the plant is configured such that, during ethane rejection, the stripper fractionates the ethane rich bottom stream from the absorber into an ethane overhead product and a propane plus hydrocarbons product, and 
 wherein the plant is configured such that, during ethane recovery, the stripper fractionates the ethane rich bottom stream into an ethane plus natural gas liquids (NGL) stream and an overhead vapor stream; and 
   an expander configured to, during ethane recovery, expand a vapor portion of a feed gas to the plant, wherein the plant is configured such that, during ethane recovery, the expanded stream is fed to the absorber.   
     
     
         2 . The plant of  claim 1 , further comprising one or more separators, wherein the plant is configured such that, during ethane rejection, a first portion of a feed stream is passed from the one or more separators to the stripper. 
     
     
         3 . The plant of  claim 2 , wherein the plant is configured such that, during ethane recovery, the first portion of the feed stream is passed to the stripper. 
     
     
         4 . The plant of  claim 1 , further comprising an exchanger, wherein the plant is configured such that, during ethane rejection, the exchanger counter-currently heat exchanges the ethane rich bottom stream from the absorber with the ethane depleted vapor stream from the absorber, thereby heating the vapor stream and chilling the ethane rich bottom stream. 
     
     
         5 . The plant of  claim 4 , wherein the plant is configured such that, during ethane rejection, the exchanger is passed from the exchanger to the stripper. 
     
     
         6 . The plant of  claim 1 , further comprising an exchanger, wherein the plant is configured such that, during ethane rejection, the ethane overhead product from the stripper is directed to the exchanger. 
     
     
         7 . The plant of  claim 1 , further comprising an exchanger, wherein the plant is configured such that, during ethane rejection, the exchanger chills the ethane overhead from the stripper. 
     
     
         8 . The plant of  claim 1 , further comprising an exchanger, wherein the plant is configured such that, during ethane rejection, the exchanger chills the ethane rich bottom stream from the absorber. 
     
     
         9 . The plant of  claim 1 , further comprising an exchanger, wherein the plant is configured such that, during ethane recovery, the exchanger receives a second portion of the feed stream. 
     
     
         10 . The plant of  claim 9 , wherein the plant is configured such that, during ethane recovery, the exchanger chills the second portion of the feed stream and passes the second portion of the feed stream to the absorber. 
     
     
         11 . The plant of  claim 1 , wherein the expanded vapor stream from the expander to the absorber provides increased chilling to the absorber when compared with the plant during ethane rejection. 
     
     
         12 . The plant of  claim 1 , wherein the ethane rich bottom stream that is fed to the stripper provides increased chilling to the stripper when compared with the plant during ethane rejection. 
     
     
         13 . The plant of  claim 1 , wherein, during ethane recovery, the overhead vapor stream from the stripper is fed to the bottom of the absorber for reabsorption of the ethane content. 
     
     
         14 . The plant of  claim 1 , wherein, during ethane recovery, the ethane plus natural gas liquids stream from the stripper contains about 1 mole % methane content. 
     
     
         15 . The plant of  claim 1 , wherein, during ethane rejection, the stripper functions as a deethanizer. 
     
     
         16 . The plant of  claim 1 , wherein, during ethane recovery, the stripper functions as a demethanizer. 
     
     
         17 . The plant of  claim 1 , wherein the plant produces at least 95% propane recovery during ethane rejection. 
     
     
         18 . The plant of  claim 1 , wherein the plant produces at least 95% propane recovery during ethane recovery. 
     
     
         19 . The plant of  claim 1 , further comprising a Joule Thompson valve, wherein the plant is configured such that, during ethane rejection:
 the ethane overhead product is received by the Joule Thompson valve from an exchanger to reduce a pressure of the ethane overhead product to form an absorber feed; and   the absorber feed stream that is passed from the Joule Thompson valve to the absorber.   
     
     
         20 . The plant of  claim 19 , further comprising a second Joule Thompson valve, wherein the plant is configured such that, during ethane rejection:
 a first portion of the feed stream is received by the second Joule Thompson valve to reduce a pressure of the first portion of the feed stream; and   the first portion of the feed stream is passed from the second Joule Thompson valve to the absorber.