Integrated methods and configurations for propane recovery in both ethane recovery and ethane rejection

Abstract

A natural gas liquids (NGL) plant, the NGL plant comprising an absorber configured to provide an absorber overhead and an absorber bottoms, a stripper configured to produce a stripper overhead and a stripper bottoms, wherein the stripper is positioned downstream from the absorber and fluidly connected therewith such that the absorber bottoms can be introduced into the stripper, and a multi-pass heat exchanger configured to provide at least one reflux stream to the absorber, wherein the absorber and stripper are configured, in an ethane rejection arrangement, to provide the stripper overhead to a top of the absorber, and wherein the absorber and stripper are configured, in an ethane recovery arrangement, to provide the stripper overhead to a bottom of the absorber.

1 . A natural gas liquids (NGL) plant, the NGL plant comprising:
 an absorber configured to provide an absorber overhead and an absorber bottoms;   a stripper configured to produce a stripper overhead and a stripper bottoms, wherein the stripper is positioned downstream from the absorber and fluidly connected therewith such that the absorber bottoms can be introduced into the stripper; and   a multi-pass heat exchanger configured to provide at least one reflux stream to the absorber wherein the multi-pass heat exchanger is configured, in the ethane recovery arrangement, to provide at least two reflux streams to the absorber,   wherein the absorber and stripper are configured, in an ethane rejection arrangement, to provide the stripper overhead to a top of the absorber, and wherein the absorber and stripper are configured, in an ethane recovery arrangement, to provide the stripper overhead to a bottom of the absorber.   
     
     
         2 . (canceled) 
     
     
         3 . The NGL plant of  claim 1 , wherein the stripper is configured, in the ethane recovery arrangement, as a demethanizer to provide a stripper bottoms comprising less than 1 vol % methane, and the stripper is configured, in the ethane rejection arrangement, as a deethanizer to provide a stripper bottoms comprising less than 2 mole percent ethane. 
     
     
         4 . The NGL plant of  claim 1 , further comprising:
 a cold separator configured to separate a two-phase separator feed into a separator vapor and a separator liquid,   wherein the cold separator is fluidly connected with the absorber, wherein the cold separator is configured, in the ethane rejection arrangement, to route the separator vapor to the bottom of the absorber.   
     
     
         5 . The NGL plant of  claim 4 , wherein the cold separator is configured, in the ethane recovery arrangement, to pass a first portion of the separator vapor to the absorber through a first pass of the multi-pass heat exchanger, and to pass a second portion of the separator vapor to the bottom of the absorber. 
     
     
         6 . The NGL plant of  claim 5 , further comprising:
 an expander in fluid communication with a bottom portion of the absorber,   wherein the expander is configured, in the ethane rejection arrangement, to produce an expander discharge from the separator vapor, and   wherein the expander is configured, in the ethane recovery arrangement, to produce the expander discharge from the second portion of the separator vapor.   
     
     
         7 . The NGL plant of  claim 4 , wherein the cold separator is configured to pass at least a portion of the separator liquid through a second pass of the multi-pass heat exchanger prior to introduction into the stripper. 
     
     
         8 . The NGL plant of  claim 4 , wherein the cold separator is configured, in an ethane recovery arrangement, to pass a first portion of the separator liquid through a second pass of the multi-pass heat exchanger prior to introduction into the absorber, and to pass a second portion of the separator liquid directly to the stripper. 
     
     
         9 . The NGL plant of  claim 4 , wherein the multi-pass heat exchanger comprises a pass configured to chill a first portion of an NGL feed gas and provide at least a portion of the two-phase separator feed. 
     
     
         10 . The NGL plant of  claim 9 , further comprising a heat exchanger and propane chiller configured to chill a second portion of the NGL feed gas to provide at least another portion of the two-phase separator feed. 
     
     
         11 . The NGL plant of  claim 1 , further comprising:
 one or more residue gas compressors configured to compress the absorber overhead to produce a compressed residue gas,   wherein the NGL plant is configured, in the ethane recovery operation, to expand and pass a portion of the compressed residue gas via the multi-pass exchanger into a top of the absorber.   
     
     
         12 . A method of operating a natural gas liquids (NGL) plant to produce an NGL product, the method comprising:
 operating the NGL plant in an ethane rejection mode, wherein operating in the ethane rejection mode comprises:
 producing, with an absorber, an absorber overhead stream and an absorber bottoms stream, 
 introducing the absorber bottoms stream into a stripper; 
 producing, with the stripper, a stripper overhead stream and a stripper bottoms stream while operating the stripper at a higher pressure than the absorber, wherein the stripper bottoms stream comprises the NGL product; and 
 chilling the stripper overhead stream to produce a chilled stripper overhead stream; 
 passing the chilled stripper overhead stream to a top of the absorber to reflux the absorber; 
 separating an NGL feed into a separator vapor stream and a separator liquid stream; 
 expanding the separator vapor stream in an expander, 
 introducing the expanded vapor into a bottom of the absorber the absorber feed; 
 passing the separator liquid through a pass of a multi-pass heat exchanger; and 
 passing the separator liquid into the stripper downstream of the multi-pass exchanger, wherein the temperature of the separator liquid is increased in the multi-pass exchanger prior to introduction into the stripper; 
   operating the NGL plant in an ethane recovery mode, wherein operating in the ethane recovery mode comprises:
 producing, with the absorber, the absorber overhead stream and the absorber bottoms stream; 
 introducing the absorber bottoms stream into the stripper; 
 producing, with the stripper, the stripper overhead stream and the stripper bottoms stream, wherein the stripper bottoms stream comprises the NGL product; and 
   passing the stripper overhead stream to a bottom of the absorber.   
     
     
         13 . (canceled) 
     
     
         14 . The method of  claim 12 , wherein operating the NGL plant in the ethane recovery mode further comprises:
 separating an NGL feed into a separator vapor and a separator liquid;   expanding a first portion of the separator vapor in an expander and introducing the expanded vapor into a bottom of the absorber as the absorber feed;   chilling a second portion of the separator vapor to provide a chilled second portion of the separator vapor;   refluxing the absorber with the chilled second portion of the separator vapor;   compressing and heat exchanging the absorber overhead stream to produce a residue gas stream;   using a portion of the residue gas stream as reflux in the absorber after passage of the portion of the residue gas stream through a pass of a multi-pass heat exchanger; and   introducing the separator liquid into the stripper without passing the separator liquid through the multi-pass heat exchanger.   
     
     
         15 . The method of  claim 14 , wherein the first portion of the separator vapor is between 50 to 70 mole percent (mol %) of the separator vapor. 
     
     
         16 . A multi-pass heat exchanger configured to provide reflux to an absorber of a natural gas liquids (NGL) plant comprising the absorber and a stripper, wherein the NGL plant is configured to selectively operate in an ethane recovery arrangement or an ethane rejection arrangement, wherein the multi-pass heat exchanged comprises:
 a first pass fluidly connected with a separator liquid line of a cold separator, wherein the cold separator is configured to separate a separator liquid from a two-phase separator feed, wherein the first pass is configured, in the ethane rejection arrangement, to heat the separator liquid prior to introduction of the separator liquid into the stripper;   a second pass fluidly connected with the separator liquid line of the cold separator, wherein the second pass is configured, in the ethane recovery arrangement, to chill a portion the separator liquid prior to introduction of the portion of separator liquid into the absorber; and   a third pass fluidly connected with an overhead vapor from the stripper and the absorber, wherein the third pass is configured, in the ethane rejection arrangement, to chill the overhead vapor from the stripper prior to passing the overhead vapor to a top of the absorber.   
     
     
         17 . The multi-pass exchanger of  claim 16 , wherein the third pass is further fluidly connected with a separator vapor line of the cold separator, wherein the cold separator is configured to separate a separator vapor from the two-phase separator feed, wherein the third pass is configured, in the ethane recovery arrangement, to chill at least a portion of the separator vapor and pass the chilled separator vapor to the top of the absorber. 
     
     
         18 . The multi-pass exchanger of  claim 17 , further comprising:
 a fourth pass fluidly connected with a cooled high pressure residue gas line comprising an overhead product from the absorber, wherein the fourth pass is configured, in the ethane recovery arrangement, to chill at least a portion of the high pressure residue gas in the high pressure residue gas line and pass the chilled portion of the high pressure residue gas as reflux to the absorber.   
     
     
         19 . The multi-pass exchanger of  claim 18 , further comprising:
 a fifth pass fluidly connected with a feed gas line comprising a feed gas, wherein the fifth pass is configured to chill at least a portion of the feed gas prior to introduction of the portion of the feed gas to the cold separator;   a sixth pass a pass fluidly connected with a refrigerant line, wherein the sixth pass is configured to chill one or more fluids passing through the multi-pass heat exchanger; and   a seventh pass fluidly connected with an absorber overhead line, wherein the seventh pass is configured to provide heat exchange between an absorber overhead stream in the absorber overhead line with the one or more fluids passing through the multi-pass heat exchanger.   
     
     
         20 . The multi-pass heat exchanger of  claim 16 , wherein the multi-pass heat exchanger is configured, in the ethane rejection arrangement, to provide a single reflux stream to the absorber, and wherein the multi-pass exchanger is configured, in the ethane recovery arrangement, to provide two reflux streams to the absorber.