Methods for separating hydrocarbon gases

Abstract

A process for separating a hydrocarbon gas into a fraction containing a predominant portion of the methane or ethane and lighter components and a fraction containing a predominant portion of the C 2 or C 3 and heavier components in which process the feed gas is treated in one or more heat exchange, and expansion steps; partly condensed feed gas is directed into a separator wherein a first residue vapor is separated from a C 2 or C 3 -containing liquid; and C 2 or C 3 -containing liquids, at substantially the pressure of separation, are directed into a distillation column wherein said liquid is separated into a second residue is separated to recover a C 2 or C 3 -containing product.

1 . In a process for separating a hydrocarbon gas containing at least ethane and C 3  and heavier components into a fraction containing a predominant portion of the ethane and lighter components and a fraction containing a predominant portion of the C 3  and heavier components in which process
 (a) the feed gas is treated in one or more heat exchangers, and expansion steps to provide at least one partly condensed hydrocarbon gas, providing thereby at least one first residue vapor and at least one C 3 -containing liquid which liquid also contains lighter hydrocarbons; and   (b) at least one of the C 3 -containing liquids is directed into a distillation column wherein said liquid is separated into a second residue containing lighter hydrocarbons and a C 3 -containing product;   the improvement comprising   (1) cooling said second residue to partially condense it;   (2) intimately contacting at least part of one of said first residue vapors with at least part of the liquid portion of the partially condensed second residue in at least one contacting stage and thereafter separating the vapors and liquids from said contacting stage;   (3) supplying the liquids thereby recovered to the distillation column as a liquid feed thereto; and   (4) directing the vapors thereby recovered into heat exchange relation with said second residue from the distillation column, thereby to supply the cooling of step (1), and thereafter discharging said residue gases; the improvement further comprising:   (5) recovering a recycle gas stream from an expander-compressor or residue gas compressor;   (6) cooling and partially condensing the recycle stream in said one or more heat exchangers whereby the recycle stream is heat exchanged in a subcooler with gases from top of a light-ends fractionation column;   (7) expanding and feeding a cold reflux stream from the subcooler into a light ends fractionation column, wherein colder temperatures realized by the cold reflux stream improves the yield of ethane and heavier components.   
     
     
         2 . The process as claimed in  claim 1  wherein said contacting step (2) is carried out in a light end fractionation column which includes fractionation means for vapor/liquid counter-current contact and
 (i) wherein said partly condensed second residue is introduced into said light ends fractionation column above said fractionation means, whereby the liquid portion of it passes downwardly through said fractionation means; and 
 (ii) said at least part of one of said first residue vapors is supplied to said light ends fractionation column below said fractionation means, whereby the first residue vapor rises through said fractionation means in counter-current contact with the liquid portion of the partly condensed second residue. 
 
     
     
         3 . The process as claimed in  claim 2  wherein the fractionation means in said light ends fractionation column provide the equivalent of at least one theoretical distillation stage arranged to contact at least part of one of said first residue vapors with the liquid portion of the partly condensed second residue. 
     
     
         4 . The improvement according to  claim 1  wherein at least part of one of said first residue vapors are co-mingled with the liquid portion of the partially condensed second residue. 
     
     
         5 . The process as claimed in  claim 1  wherein at least part of one of said first residue vapors and are comingled with both the liquid portion and vapor portion of said partially condensed second residue. 
     
     
         6 . The process as claimed in  claim 1  wherein said recycle gas stream recovered is further fed through an expander/compressor discharge cooler or residue gas compressor discharge cooler prior to it being condensed in said one or more heat exchangers. 
     
     
         7 . The process as claimed in  claim 1  wherein said one or more heat exchangers receives additional gas and liquid flows to cool and partially condense the recycle stream. 
     
     
         8 . The process as claimed in  claim 7  wherein said additional gas and liquid flows are selected from the group consisting of inlet gas stream, liquid product stream, reboiler fluid stream, side heater fluid stream, refrigerant stream(s) and residue gas stream. 
     
     
         9 . The process as claimed in  claim 1  wherein said one or more heat exchangers is a plate-fin exchanger, shell and tube heat exchanger or coil wound heat exchanger. 
     
     
         10 . The process as claimed in  claim 1  wherein said expanding is through a flow control valve or turboexpander. 
     
     
         11 . The process as claimed in  claim 1  wherein said cold reflux stream is from a heavy ends fractionation column. 
     
     
         12 . In an apparatus for separating a hydrocarbon gas containing at least ethane and C 3  components into a fraction containing a predominant portion of ethane and lighter components and a fraction containing a predominant portion of the C 3  and heavier components in which apparatus
 (a) one or more heat exchange means and one or more expansion means are provided which are cooperatively connected to provide at least one partly condensed hydrocarbon gas, providing thereby at least one first residue vapor and at least one C 3 -containing liquid which liquid also contains lighter hydrocarbons and   (b) a distillation column connected to receive at least one of said C 3 -containing liquids which is adapted to separate the C 3 -containing liquids into a second residue containing lighter hydrocarbons and a C 3 -containing product;   the improvement comprising   (1) heat exchange means connected to said distillation column to receive said second residue and to partially condense it;   (2) contacting and separating means connected to receive at least part of one of the first residue vapors and at least part of the liquid portion of the partially condensed second residue and to comingle said vapor and liquid in at least one contacting stage, which means include separation means for separating the vapor and liquid after contact in said stage;   (3) said means (2) being further connected to supply the liquids separated therein to the distillation column as a liquid feed thereto, and   (4) said means (2) also being connected to direct the vapors separated therein into heat exchange relation with said second residue from the distillation column in said heat exchange means (1); the improvement further comprising   (5) Product cooler means connected to said distillation column to receive said second residue from said distillation column and to feed said second residue to said heat exchange means.   
     
     
         13 . The apparatus as claimed in  claim 12  wherein said contacting and separating means includes fractionation means for countercurrent vapor/liquid contact and wherein said means is connected to receive the portion of one of first residue vapors to be treated therein below said fractionation means and to receive the portion of said liquids from the partially condensed second residue to be treated therein above said fractionation means said fractionation means thereby being adapted so that the first residue vapors rise therethrough in countercurrent contact with partially condensed second residue. 
     
     
         14 . The apparatus as claimed in  claim 13  wherein said fractionation means includes vapor/liquid contacting means which are the equivalent of at least one theoretical distillation stage. 
     
     
         15 . The apparatus as claimed in  claim 14  wherein said contacting and separating means (2) comprise means for comingling at least part of one of said first residue vapors with the liquid portion of the partially condensed second residue. 
     
     
         16 . The apparatus as claimed in  claim 14  wherein said contacting and separating means (2) comprise means for comingling at least part of one of said first residue vapors with both the liquid and vapor portion of said partially condensed second residue. 
     
     
         17 . In a process for separating a hydrocarbon gas containing at least methane and C 2  and heavier components into a fraction containing a predominant portion of the methane and lighter components and a fraction containing a predominant portion of the C 2  and heavier components in which process
 (a) the feed gas is treated in one or more heat exchangers, and expansion steps to provide at least one partly condensed hydrocarbon gas, providing thereby at least one first residue vapor and at least one C 2 -containing liquid which liquid also contains lighter hydrocarbons; and   (b) at least one of the C 2 -containing liquids is directed into a distillation column wherein said liquid is separated into a second residue containing lighter hydrocarbons and a C 2 -containing product;   the improvement comprising   (1) cooling said second residue to partially condense it;   (2) intimately contacting at least part of one of said first residue vapors with at least part of the liquid portion of the partially condensed second residue in at least one contacting stage and thereafter separating the vapors and liquids from said contacting stage;   (3) supplying the liquids thereby recovered to the distillation column as a liquid feed thereto; and   (4) directing the vapors thereby recovered into heat exchange relation with said second residue from the distillation column, thereby to supply the cooling of step (1), and thereafter discharging said residue gases; the improvement further comprising:   (5) recovering a recycle gas stream from an expander-compressor or residue gas compressor;   (6) cooling and partially condensing the recycle stream in said one or more heat exchangers whereby the recycle stream is heat exchanged in a subcooler with gases from top of a light-ends fractionation column;   (7) expanding and feeding a cold reflux stream from the subcooler into a light ends fractionation column, wherein colder temperatures realized by the cold reflux stream improves the yield of ethane and heavier components.   
     
     
         18 . The process as claimed in  claim 17  wherein said contacting step (2) is carried out in a light end fractionation column which includes fractionation means for vapor/liquid counter-current contact and
 (i) wherein said partly condensed second residue is introduced into said light ends fractionation column above said fractionation means, whereby the liquid portion of it passes downwardly through said fractionation means; and 
 (ii) said at least part of one of said first residue vapors is supplied to said light ends fractionation column below said fractionation means, whereby the first residue vapor rises through said fractionation means in counter-current contact with the liquid portion of the partly condensed second residue. 
 
     
     
         19 . The process as claimed in  claim 18  wherein the fractionation means in said light ends fractionation column provide the equivalent of at least one theoretical distillation stage arranged to contact at least part of one of said first residue vapors with the liquid portion of the partly condensed second residue. 
     
     
         20 . The improvement according to  claim 17  wherein at least part of one of said first residue vapors are co-mingled with the liquid portion of the partially condensed second residue. 
     
     
         21 . The process as claimed in  claim 17  wherein at least part of one of said first residue vapors and are comingled with both the liquid portion and vapor portion of said partially condensed second residue. 
     
     
         22 . The process as claimed in  claim 17  wherein said recycle gas stream recovered is further fed through an expander/compressor discharge cooler or residue gas compressor discharge cooler prior to it being condensed in said one or more heat exchangers. 
     
     
         23 . The process as claimed in  claim 17  wherein said one or more heat exchangers receives additional gas and liquid flows to cool and partially condense the recycle stream. 
     
     
         24 . The process as claimed in  claim 23  wherein said additional gas and liquid flows are selected from the group consisting of inlet gas stream, liquid product stream, reboiler fluid stream, side heater fluid stream, refrigerant stream(s) and residue gas stream. 
     
     
         25 . The process as claimed in  claim 17  wherein said one or more heat exchangers is a plate-fin exchanger, shell and tube heat exchanger or coil wound heat exchanger. 
     
     
         26 . The process as claimed in  claim 17  wherein said expanding is through a flow control valve or turboexpander. 
     
     
         27 . The process as claimed in  claim 17  wherein said cold reflux stream is from a heavy ends fractionation column. 
     
     
         28 . In an apparatus for separating a hydrocarbon gas containing at least methane and C 2  components into a fraction containing a predominant portion of methane and lighter components and a fraction containing a predominant portion of the C 2  and heavier components in which apparatus
 (a) one or more heat exchange means and one or more expansion means are provided which are cooperatively connected to provide at least one partly condensed hydrocarbon gas, providing thereby at least one first residue vapor and at least one C 2 -containing liquid which liquid also contains lighter hydrocarbons and   (b) a distillation column connected to receive at least one of said C 2 -containing liquids which is adapted to separate the C 2 -containing liquids into a second residue containing lighter hydrocarbons and a C 2 -containing product;   the improvement comprising   (1) heat exchange means connected to said distillation column to receive said second residue and to partially condense it;   (2) contacting and separating means connected to receive at least part of one of the first residue vapors and at least part of the liquid portion of the partially condensed second residue and to comingle said vapor and liquid in at least one contacting stage, which means include separation means for separating the vapor and liquid after contact in said stage;   (3) said means (2) being further connected to supply the liquids separated therein to the distillation column as a liquid feed thereto, and   (4) said means (2) also being connected to direct the vapors separated therein into heat exchange relation with said second residue from the distillation column in said heat exchange means (1); the improvement further comprising   (5) Product cooler means connected to said distillation column to receive said second residue from said distillation column and to feed said second residue to said heat exchange means.   
     
     
         29 . The apparatus as claimed in  claim 28  wherein said contacting and separating means includes fractionation means for countercurrent vapor/liquid contact and wherein said means is connected to receive the portion of one of first residue vapors to be treated therein below said fractionation means and to receive the portion of said liquids from the partially condensed second residue to be treated therein above said fractionation means said fractionation means thereby being adapted so that the first residue vapors rise therethrough in countercurrent contact with partially condensed second residue. 
     
     
         30 . The apparatus as claimed in  claim 29  wherein said fractionation means includes vapor/liquid contacting means which are the equivalent of at least one theoretical distillation stage. 
     
     
         31 . The apparatus as claimed in  claim 30  wherein said contacting and separating means (2) comprise means for comingling at least part of one of said first residue vapors with the liquid portion of the partially condensed second residue. 
     
     
         32 . The apparatus as claimed in  claim 29  wherein said contacting and separating means (2) comprise means for comingling at least part of one of said first residue vapors with both the liquid and vapor portion of said partially condensed second residue.