Lean reflux process for high recovery of ethane and heavier components
First Claim
1. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
- a) deriving a top feed portion and a bottom feed portion to said lean reflux absorber by dividing a feed gas stream into a top feed portion, a bottom feed portion, and a first gas portion, and thereafter cooling and separating said first gas portion into a first liquid phase comprising condensed components and a main vapor portion;
b) condensing said top feed portion and thereafter introducing it to the top of said lean reflux absorber comprising one or more mass transfer stages;
c) introducing said bottom feed portion to said lean reflux absorber at a location below said condensed top feed portion;
d) rectifying within said lean reflux absorber to produce a lean vapor phase from an upper region of said lean reflux absorber, and a bottom fluid stream comprising the remaining components from the bottom of said lean reflux absorber;
e) condensing said lean vapor phase to form a lean reflux stream for top feed to said cryogenic distillation column;
f) expanding and lowering the pressure of;
(i) said lean reflux stream and supplying it as reflux to the top of said cryogenic distillation column, (ii) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (iii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the top reflux and at least the same as or above the first liquid phase, if present, and (iv) said first liquid phase, if present, and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, and g) recovering natural gas liquid product from the bottom of said cryogenic distillation column.
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Accused Products
Abstract
A simple, efficient, and cost effective process for separating components of a feed gas, e.g., containing methane and heavier hydrocarbons has been devised. First, feed gas is condensed to provide a vapor component and a liquid component. The vapor component is divided into at least a first, major portion a second portion, and a remaining portion. The second portion is directed to a lean reflux absorber, and the remaining portion is condensed and fed to the top of the lean reflux absorber. A bottom fluid stream, generally a liquid intermediate product, is recovered from the bottom of the lean reflux absorber, and lean vapor is recovered from the top of the lean reflux absorber. The liquid component, the first, major portion of the first vapor component, the liquid product from the bottom of the lean reflux absorber, and the lean vapor from the top of the lean reflux absorber are all fed to different feed points on a cryogenic distillation column. An optional cold side reboiler may be used to bring the cooling and heating curves into a more parallel relationship to improve process efficiency.
93 Citations
34 Claims
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1. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
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a) deriving a top feed portion and a bottom feed portion to said lean reflux absorber by dividing a feed gas stream into a top feed portion, a bottom feed portion, and a first gas portion, and thereafter cooling and separating said first gas portion into a first liquid phase comprising condensed components and a main vapor portion;
b) condensing said top feed portion and thereafter introducing it to the top of said lean reflux absorber comprising one or more mass transfer stages;
c) introducing said bottom feed portion to said lean reflux absorber at a location below said condensed top feed portion;
d) rectifying within said lean reflux absorber to produce a lean vapor phase from an upper region of said lean reflux absorber, and a bottom fluid stream comprising the remaining components from the bottom of said lean reflux absorber;
e) condensing said lean vapor phase to form a lean reflux stream for top feed to said cryogenic distillation column;
f) expanding and lowering the pressure of;
(i) said lean reflux stream and supplying it as reflux to the top of said cryogenic distillation column, (ii) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (iii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the top reflux and at least the same as or above the first liquid phase, if present, and (iv) said first liquid phase, if present, and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, and g) recovering natural gas liquid product from the bottom of said cryogenic distillation column. - View Dependent Claims (2, 3, 4, 8, 10, 31)
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5. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
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a) deriving a top feed portion and a bottom feed portion to said lean reflux absorber by an approach selected from the group consisting of;
(i) cooling and thereafter separating a feed gas stream into a first liquid phase comprising condensed components, and a cooled vapor phase and thereafter dividing said cooled vapor phase into a top feed portion, a bottom feed portion, and a main vapor portion;
(ii) cooling and thereafter dividing a feed gas stream into a top feed portion, a bottom feed portion, and a main vapor portion in the absence of liquid condensation during the cooling step;
(iii) dividing a feed gas stream into a top feed portion, a bottom feed portion, and a first gas portion, and thereafter cooling said first gas portion to provide a main vapor portion; and
b) condensing said top feed portion and thereafter introducing it to the top of said lean reflux absorber comprising one or more mass transfer stages;
c) introducing said bottom feed portion to said lean reflux absorber at a location below said condensed top feed portion;
d) rectifying within said lean reflux absorber to produce a lean vapor phase from an upper region of said lean reflux absorber, and a bottom fluid stream comprising the remaining components from the bottom of said lean reflux absorber;
e) compressing said lean vapor phase from an upper region of said lean reflux absorber to a higher pressure;
f) condensing said compressed lean vapor phase to form a lean reflux stream as top feed to the cryogenic distillation column;
g) expanding and lowering the pressure of;
(i) said lean reflux stream and supplying it as reflux to the top of said cryogenic distillation column, (ii) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (iii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the top reflux and at least the same as or above the first liquid phase, if present, and (iv) said first liquid phase, if present, and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, and h) recovering natural gas liquid product from the bottom of said cryogenic distillation column. - View Dependent Claims (6, 7, 32, 33)
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9. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
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a) deriving a top feed portion and a bottom feed portion to said lean reflux absorber by an approach selected from the group consisting of;
(i) cooling and thereafter separating a feed gas stream into a first liquid phase comprising condensed components, and a cooled vapor phase and thereafter dividing said cooled vapor phase into a top feed portion, a bottom feed portion, and a main vapor portion;
(ii) cooling and thereafter dividing a feed gas stream into a top feed portion, a bottom feed portion, and a main vapor portion in the absence of liquid condensation during the cooling step;
(iii) dividing a feed gas stream into a top feed portion, a bottom feed portion, and a first gas portion, and thereafter cooling said first gas portion to provide a main vapor portion; and
b) condensing said top feed portion and thereafter introducing it to the top of said lean reflux absorber comprising one or more mass transfer stages;
c) introducing said bottom feed portion to said lean reflux absorber at a location below said condensed top feed portion;
d) rectifying within said lean reflux absorber to produce a lean vapor phase from an upper region of said lean reflux absorber, and a bottom fluid stream comprising the remaining components from the bottom of said lean reflux absorber;
e) condensing said lean vapor phase to form a lean reflux stream for top feed to said cryogenic distillation column;
f) expanding and lowering the pressure of;
(i) said lean reflux stream and supplying it as reflux to the top of said cryogenic distillation column, (ii) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (iii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the top reflux and at least the same as or above the first liquid phase, if present, and (iv) said first liquid phase, if present, and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, and g) withdrawing at least a portion of liquid from said cryogenic distillation column at a point near the feed of the expander discharge;
h) heating said withdrawn liquid to provide cooling to a stream selected from the group consisting of said lean vapor phase, said top feed portion, said bottom fluid stream, or a combination thereof, and i) returning said heated withdrawn liquid to said cryogenic distillation column at a point below where it was withdrawn; and
j) recovering natural gas liquid product from the bottom of said cryogenic distillation column. - View Dependent Claims (34)
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11. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
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a) dividing a feed gas into a first gas fraction, and a second gas fraction;
b) compressing said second gas fraction to a pressure higher than that of said cryogenic distillation column to form a compressed gas stream;
c) cooling said compressed gas stream and thereafter dividing it into a bottom feed portion and a top feed portion;
d) further condensing said top feed portion and thereafter introducing it to the top of said lean reflux absorber comprising one or more mass transfer stages;
e) introducing said bottom feed portion to said lean reflux absorber at a location below said condensed top feed portion;
f) rectifying within said lean reflux absorber to produce a lean vapor phase from an upper region of said lean reflux absorber, and a bottom fluid stream from the bottom of said lean reflux absorber;
g) deriving a main vapor portion by an approach selected from the group consisting of;
(i) cooling said first gas fraction to partial condensation and thereafter separating it into a first liquid phase comprising condensed components, and a main vapor portion comprising predominantly volatile vapor components, and (ii) cooling said first gas portion to provide a main vapor portion in the absence of liquid condensation during the cooling step;
h) condensing said lean vapor phase to provide a liquid reflux stream as top feed to the cryogenic distillation column;
i) expanding and lowering the pressure of;
(i) said lean reflux stream and supplying it as reflux to the top of said cryogenic distillation column, (ii) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (iii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the top reflux and at least the same as or above the first liquid phase, if present, (iv) said first liquid phase, if present, and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, and;
j) recovering natural gas liquid product from the bottom of said cryogenic distillation column. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
(i) at least partially condensing said compressed gas stream to form a two-phase stream;
(ii) separating said two-phase stream into a cooled vapor stream, and into a cooled liquid stream;
(iii) dividing said cooled vapor stream into a top feed portion, and a bottom feed portion; and
(iv) expanding and lowering the pressure of said cooled liquid stream and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed.
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13. The process of claim 12 further comprising introducing at least a portion of said cooled liquid stream to a lower region of said lean reflux absorber.
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14. The process of claim 11 further comprising expanding said main vapor portion through an expander thereby providing further cooling prior to supplying it to said cryogenic distillation column.
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15. The process of claim 11 further comprising expanding said bottom feed portion through an expander thereby further cooling the stream prior to introducing it to said lean reflux absorber at a point below said condensed top feed portion.
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16. The process of claim 11 further comprising compressing said lean vapor phase from an upper region of said lean reflux absorber to a higher pressure prior to substantial condensation to provide a liquid reflux as top feed to the cryogenic distillation column.
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17. The process of claim 16, wherein said lean vapor phase is warmed prior to being compressed to a higher pressure.
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18. The process of claim 15 further comprising recovering expansion work from the expander and wherein said expansion work recovered is used to compress said lean vapor phase.
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19. The process of claim 11 further comprising cooling said bottom feed portion prior to introducing it to said lean reflux absorber.
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20. The process of claim 11 wherein said bottom fluid stream is further cooled prior to being expanded to said cryogenic distillation column to reduce vapor flashing upon expansion.
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21. The process of claim 11 further comprising:
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a) withdrawing at least a portion of liquid from said cryogenic distillation column at a point near the feed of the expander discharge;
b) heating said withdrawn liquid to provide cooling to a stream selected from the group consisting of said lean vapor phase, said top feed portion, said bottom fluid stream, or a combination thereof; and
c) returning said heated withdrawn liquid to said cryogenic distillation column at a point below where it was withdrawn.
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22. The process of claim 11 further comprising introducing at least a portion of said first liquid phase to said lean reflux absorber.
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23. A process for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column wherein its reflux components are cryogenically generated by a separate lean reflux absorber, comprising:
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a) deriving a bottom feed portion to said lean reflux absorber by an approach selected from the group consisting of;
(i) cooling said feed gas and thereafter separating it into a first liquid phase comprising condensed components, and a first vapor phase comprising predominantly volatile vapor components;
then dividing said first vapor phase into a main vapor portion, and a bottom feed portion;
(ii) dividing said feed gas into a first gas fraction and a second gas fraction and thereafter cooling said first gas fraction to form a bottom feed portion;
cooling said second gas fraction and separating it into a first liquid phase and a main vapor portion;
(iii) dividing said feed gas into a first gas fraction and a second gas fraction and thereafter compressing and cooling said first gas fraction to form a bottom feed portion;
cooling said second gas fraction and separating it into a first liquid phase and a main vapor portion; and
b) introducing said bottom feed portion to a lower region of said lean reflux absorber comprising one or more mass transfer stages;
c) removing a bottom fluid stream from the bottom of said lean reflux absorber;
d) expanding and lowering the pressure of;
(i) said bottom fluid stream and supplying it as a first middle feed to a middle region of said cryogenic distillation column at a point below top reflux, (ii) said main vapor portion and supplying it as a second middle feed to the middle region of said cryogenic distillation column at a point below the first middle feed, (iii) said first liquid phase and supplying it as a third middle feed to the middle region of said cryogenic distillation column at a point not higher than the second middle feed, e) removing cold residue gas from an upper region of said cryogenic distillation column;
f) drawing off a portion of said cold residue gas and compressing it to form a recycle residue gas;
g) condensing said recycle residue gas and thereafter introducing it to the top of said lean reflux absorber;
h) generating within said lean reflux absorber a lean vapor phase from an upper region thereof;
i) condensing said lean vapor phase to provide a liquid reflux and thereafter expanding and supplying it as reflux to the top of said cryogenic distillation column; and
j) recovering natural gas liquid product from the bottom of said cryogenic distillation column. - View Dependent Claims (24)
a) warming said cold residue gas to raise its temperature near ambient; and
b) compressing said warm residue gas to a higher pressure and drawing off a portion of said compressed residue gas as the recycle residue gas.
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25. In an apparatus for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column to produce a natural gas liquid product, the apparatus comprising:
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a) means for cooling and dividing said feed gas into a top feed portion, a bottom feed portion, and a main vapor portion;
b) means for condensing said top feed portion;
c) means for separation comprising one or more mass transfer stages, which receives said condensed top feed portion in a top region thereof, and said bottom feed portion in a lower region thereof;
wherein said means for separation produces a lean vapor phase essentially free of components to be recovered in said natural gas liquid product from the top region thereof, and a bottom fluid stream from the bottom region thereof;
d) means for condensing said lean vapor phase to form a lean reflux stream, which means may be the same or different as means for condensing b);
e) a cryogenic distillation column having a plurality of feed points and recovery stages, which receives the main vapor portion and the following reflux streams to enhance recovery efficiency;
(i) said lean reflux stream in the top of said cryogenic distillation column as a top reflux, and (ii) said bottom fluid stream in a middle region of said cryogenic distillation column as a middle reflux.
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26. In an apparatus for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column to produce a natural gas liquid product, the apparatus comprising:
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a) means for cooling and dividing said feed gas into a top feed portion, a bottom feed portion, and a main vapor portion;
b) means for condensing said top feed portion;
c) means for separation comprising one or more mass transfer stages, which receives said condensed top feed portion in a top region thereof, and said bottom feed portion in a lower region thereof;
wherein said means for separation produces a lean vapor phase essentially free of components to be recovered in said natural gas liquid product from the top region thereof, and a bottom fluid stream from the bottom region thereof;
d) a compressor for increasing the pressure of said lean vapor phase;
e) means for condensing said compressed lean vapor phase to form a lean reflux stream, which means may be the same or different as means for condensing b);
f) a cryogenic distillation column having a plurality of feed points and recovery stages, which receives the main vapor portion and the following reflux streams to enhance recovery efficiency;
(i) said lean reflux stream in the top of said cryogenic distillation column as a top reflux, and (ii) said bottom fluid stream in a middle region of said cryogenic distillation column as a middle reflux. - View Dependent Claims (27)
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28. In an apparatus for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column to produce a natural gas liquid product, the apparatus comprising:
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a) means for splitting the feed gas into a first portion of said feed gas and a remaining portion of said feed gas;
b) a compressor for increasing the pressure of the first portion of said feed gas;
c) means for cooling and dividing said compressed feed gas into a top feed portion, and a bottom feed portion;
d) means for cooling the remaining portion of said feed gas to produce a main vapor portion;
e) means for condensing said top feed portion;
f) means for separation comprising one or more mass transfer stages, which receives said condensed top feed portion in a top region thereof, and said bottom feed portion in a lower region thereof;
wherein said means for separation produces a lean vapor phase essentially free of components to be recovered in said natural gas liquid product from the top region thereof, and a bottom fluid stream from the bottom region thereof;
g) means for condensing said lean vapor phase to form a lean reflux stream, which means may be the same or different as means for condensing e);
h) a cryogenic distillation column having plurality of feed points and recovery stages, which receives the main vapor portion and the following reflux streams to enhance recovery efficiency;
(i) said lean reflux stream in the top of said cryogenic distillation column as a top reflux, and (ii) said bottom fluid stream in a middle region of said cryogenic distillation column as a middle reflux at a point below said top reflux.
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29. In an apparatus for recovering components of a hydrocarbon-containing feed gas via a cryogenic distillation column to produce a natural gas liquid product, the apparatus comprising:
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a) a compressor for increasing the pressure of a recycle residue gas from the top of said cryogenic distillation column;
b) means for cooling said compressed recycle residue gas to substantial condensation to provide a top feed portion;
c) means for cooling and dividing said feed gas into a main vapor portion, and a bottom feed portion;
d) means for separation comprising one or more mass transfer stages, which receives said condensed top feed portion in a top region thereof, and said bottom feed portion in a lower region thereof;
wherein said means for separation produces a lean vapor phase essentially free of components to be recovered in said natural gas liquid product from the top region thereof, and a bottom fluid stream from the bottom region thereof;
e) means for condensing said lean vapor phase to form a lean reflux stream;
f) a cryogenic distillation column having plurality of feed points and recovery stages, which receives said main vapor portion and the following reflux streams to enhance recovery efficiency;
(i) said lean reflux stream in the top of said cryogenic distillation column as a top reflux, and (ii) said bottom fluid stream in the middle region of said cryogenic distillation column as a middle reflux. - View Dependent Claims (30)
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Specification