Helium Recovery From Natural Gas Integrated With NGL Recovery

Abstract

The invention relates to a process for producing a helium-enriched vapor stream, a methane-enriched vapor stream, and a liquid stream enriched in hydrocarbons heavier than methane from a pressurized, multicomponent, multiphase stream comprising methane (C 1 ), helium (He) and hydrocarbons heavier than methane (C 2+ ). The process includes cooling the multiphase stream to produce at least one vapor stream enriched in helium and at least one liquid stream, withdrawing at least a portion of the at least one vapor stream as a helium-enriched product stream, passing at least a portion of the at least one liquid stream to a demethanizer, withdrawing from the demethanizer a vapor enriched in methane (C 1 ), and withdrawing from the demethanizer a liquid enriched in hydrocarbons heavier than methane (C 2+ ).

1 . A process for producing a helium-enriched vapor stream, a methane-enriched vapor stream, and a liquid stream enriched in hydrocarbons heavier than methane from a pressurized, multicomponent, multiphase stream comprising methane (C 1 ), helium (He) and hydrocarbons heavier than methane (C 2+ ), the process comprising the steps of:
 (a) cooling the multiphase stream to produce at least one vapor stream enriched in helium and at least one liquid stream;   (b) withdrawing at least a portion of the at least one vapor stream as a helium-enriched product stream;   (c) passing at least a portion of the at least one liquid stream to a demethanizer;   (d) withdrawing from the demethanizer a vapor enriched in methane (C 1 ); and   (e) withdrawing from the demethanizer a liquid enriched in hydrocarbons heavier than methane (C 2+ ).   
     
     
         2 . The process of  claim 1  wherein the step of cooling the feed stream is carried out using one or more heat exchangers. 
     
     
         3 . The process of  claim 1  further comprising, after cooling the multiphase stream, passing the cooled multiphase stream to a phase separator which separates the cooled feed stream into the at least one vapor stream and the at least one liquid stream. 
     
     
         4 . The method of  claim 3  further comprising withdrawing the at least one liquid stream from the phase separator and passing the at least one liquid stream to a flow regulating device and thereafter passing at least a portion of the at least one liquid stream to the demethanizer. 
     
     
         5 . A process for producing a helium-enriched vapor stream, a methane-enriched vapor stream, and a liquid stream enriched in hydrocarbons heavier than methane (C 2+ ) from a pressurized, multicomponent, multiphase feed stream comprising methane (C 1 ), helium (He) and hydrocarbons heavier than methane (C 2+ ), the process comprising the steps of:
 (a) passing the feed stream into a first phase separator to produce a first vapor phase and a first liquid phase;   (b) withdrawing the first vapor phase from the first phase separator;   (c) separating the first vapor phase into a second vapor phase and a third vapor phase;   (d) cooling the second vapor phase by indirect heat exchange in a heat exchanger;   (e) expanding the cooled second vapor phase to produce a reduced-pressure vapor phase and reduced-pressure liquid phase, and passing the reduced-pressure vapor and liquid phases to a second phase separator;   (f) withdrawing from the second phase separator a helium-enriched vapor phase;   (g) withdrawing liquid from the second phase separator and passing the withdrawn liquid to a first flow regulating device;   (h) passing the liquid from the flow regulating device to a demethanizer;   (i) expanding the third vapor phase of step (c) to produce a reduced-pressure vapor phase and reduced-pressure pressure liquid phase, and passing the reduced-pressure vapor and liquid phases to the demethanizer;   (j) withdrawing liquid from the first phase separator and passing the withdrawn liquid to a second flow regulating device;   (k) passing the liquid from the second flow regulating device to the demethanizer;   (l) withdrawing from the demethanizer a vapor enriched in methane (C 1 ); and   (m) withdrawing from the demethanizer a liquid enriched in hydrocarbons heavier than methane (C 2+ ).   
     
     
         6 . The process of  claim 5  wherein the first flow regulating device is an expansion device. 
     
     
         7 . The process of  claim 6  wherein the expansion device is a J-T valve. 
     
     
         8 . The process of  claim 6  wherein the expansion device is a turboexpander. 
     
     
         9 . The process of  claim 5  wherein at least one of the first flow regulating device or the second flow regulating devices is a flow regulating pump. 
     
     
         10 . The process of  claim 5  wherein the second flow regulating device is an expansion device. 
     
     
         11 . The process of  claim 10  wherein the expansion device is a J-T valve. 
     
     
         12 . The process of  claim 10  wherein the expansion device is a turboexpander. 
     
     
         13 . The process of  claim 10  wherein the second flow regulating device is liquid regulator. 
     
     
         14 . A process for separating a feed stream comprising methane (C 1 ), and hydrocarbons heavier than methane, and helium into a gas fraction containing substantially all the methane, a liquid fraction containing a large portion of the hydrocarbons heavier than methane, and a helium-enriched fraction, the process comprising the steps of:
 (a) providing the feed stream at a temperature sufficiently low for feed stream to be multiphase;   (b) passing the multiphase feed stream of step (a) to a phase separator produce a first vapor stream and a first liquid stream;   (c) passing the first liquid stream to a first flow regulating device;   (d) passing the liquid from the first flow regulating device to a demethanizer;   (e) passing a first fraction of the first vapor stream to an expander device to lower the pressure of the first fraction, thereby cooling the first fraction of the vapor stream to produce a second multiphase stream;   (f) passing the second multiphase stream to the demethanizer;   (g) passing a second fraction of the first vapor stream to a heat exchanger to cool the second fraction of the first vapor stream to a lower temperature, thereby producing a cooled stream and passing the cooled stream to an expander device thereby producing a third multiphase stream;   (h) passing the third multiphase stream of step (g) to a separator to produce a helium-enriched vapor stream and a second liquid stream;   (i) passing the second liquid to a second flow regulating device;   (j) passing the second liquid from the second flow regulating device to the demethanizer;   (k) withdrawing a vapor stream from the demethanizer enriched in methane; and   (l) withdrawing a liquid stream from the demethanizer enriched in hydrocarbons heavier than methane.   
     
     
         15 . The process of  claim 14  wherein the first flow regulating device is an expansion device. 
     
     
         16 . The process of  claim 15  wherein the expansion device is a J-T valve. 
     
     
         17 . The process of  claim 15  wherein the expansion device is a turboexpander. 
     
     
         18 . The process of  claim 14  wherein the first flow regulating device is a cryogenic pump. 
     
     
         19 . The process of  claim 14  wherein the second flow regulating device is an expansion device. 
     
     
         20 . The process of  claim 19  wherein the expansion device is a J-T valve. 
     
     
         21 . The process of  claim 19  wherein the expansion device is a turboexpander. 
     
     
         22 . The process of  claim 14  wherein the second flow regulating device is a cryogenic pump. 
     
     
         23 . A process for separating a feed stream comprising methane, hydrocarbons heavier than methane, and helium into a gas fraction rich in methane, a liquid fraction rich in hydrocarbons heavier than methane, and vapor fraction rich in helium, the process comprising the steps of:
 (a) providing the feed stream at a temperature sufficiently low for the feed stream to be multiphase;   (b) passing the multiphase stream of step (a) to a first separator produce a first vapor stream and a first liquid stream;   (c) passing the first liquid stream to a first flow regulating device;   (d) passing the liquid stream from the first flow regulating device to a second separator to produce a first helium-enriched vapor stream and a second liquid stream;   (e) passing the second liquid stream to a second flow regulating device;   (f) passing the second liquid stream from the second flow regulating device to a demethanizer;   (g) passing a first fraction of the first vapor stream to an expansion device, thereby cooling the first fraction to produce a cooled stream;   (h) passing the cooled stream of step (g) to a third separator to produce a vapor stream and a third liquid stream;   (i) passing the third liquid stream to a third flow regulating device;   (j) passing the third liquid stream from the third flow regulating device to the demethanizer;   (k) passing a second fraction of the first vapor stream to a heat exchanger to cool the second fraction a lower temperature, and thereafter passing the cooled second fraction to an expander device to further cool the second fraction;   (l) passing the cooled second fraction from the expander device of step (k) to a fourth separator to produce a helium-enriched vapor stream and a fourth liquid stream;   (m) passing the fourth liquid stream to a fourth flow regulating device;   (n) passing fourth liquid stream to the demethanizer;   (o) withdrawing a vapor stream from the demethanizer enriched in methane;   (p) withdrawing a liquid stream from the demethanizer enriched in hydrocarbons heavier than methane.   
     
     
         24 . The process of  claim 23  wherein at least one of the first, second, third and fourth flow regulating devices is an expansion device. 
     
     
         25 . The process of  claim 24  wherein the expansion device is selected from a J-T valve or turboexpander. 
     
     
         26 . The process of  claim 23  wherein at least one of the first, second, third, and fourth flow regulating devices is a cryogenic pump. 
     
     
         27 . A process for separation of hydrocarbons to separate a feed stream containing at least methane, a hydrocarbon less volatile than methane, and helium, into a residue gas enriched with methane and lean in the hydrocarbon less volatile than methane, a heavier fraction lean in methane and enriched with the hydrocarbon less volatile than methane, and a fraction enriched in helium, the process comprising the steps of:
 (a) providing a feed stream that is partly condensed;   (b) separating the feed stream into a vapor and a first liquid;   (c) passing the liquid separated in step (b) to a first flow regulating device;   (d) passing the liquid from the flow regulating device to a distillation column;   (e) dividing the vapor obtained in step (b) into a first portion and a second portion;   (f) expanding a first portion of the vapor separated in step (b), thereby producing a second reduced pressure stream, and passing the second reduced pressure stream to the distillation column;   (g) cooling the second portion of the vapor separated in step (b) in a heat exchanger and expanding the cooled second vapor portion, thereby partly condensing the cooled second vapor portion;   (h) separating partly condensed, cooled second vapor portion of step (g) into a helium-enriched stream and a second liquid;   (i) passing the second liquid separated in step (h) to a second flow regulating device;   (j) passing second liquid from the second flow regulating device to the distillation column; and   (k) recovering from the distillation column a vapor stream enriched in methane and a liquid enriched in hydrocarbons less volatile than methane.   
     
     
         28 . A process for separating a natural gas stream comprising methane, hydrocarbons heavier than methane, and helium into a gas fraction rich in methane, a liquid fraction rich in hydrocarbons heavier than methane, and vapor fraction rich in helium, the process comprising the steps of:
 (a) providing the natural gas stream at a temperature sufficiently low for the natural gas stream to be multiphase;   (b) passing the natural gas stream of step (a) to a first phase separator to produce a first vapor stream and a first liquid stream;   (c) passing the first liquid stream to a first flow regulating device;   (d) passing the liquid stream from the first flow regulating device to a demethanizer;   (e) passing the first vapor stream to an a first heat exchanger, thereby cooling the first vapor fraction to produce second multiphase stream;   (f) passing the second multiphase stream of step (e) to a second phase separator to produce a second vapor stream and second liquid stream;   (g) passing the second liquid stream to a second flow regulating device;   (h) passing the second liquid from the second flow regulating device to the demethanizer;   (i) passing the second vapor stream to a second heat exchanger, thereby cooling the second vapor fraction to produce third multiphase stream;   (j) passing the third multiphase stream of step (i) to a third phase separator to produce a third vapor stream that is enriched in helium and a third liquid stream;   (k) passing the third liquid stream to a third flow regulating device;   (l) passing the third liquid from the third flow regulating device to the demethanizer;   (m) withdrawing a vapor stream from the demethanizer enriched in methane; and   (n) withdrawing a liquid stream from the demethanizer enriched in hydrocarbons heavier than methane.