US4479871A — Process to separate natural gas liquids from nitr…

Claim 1

Independent Claim 264 words

A process for the separation of natural gas liquids from methane and nitrogen comprising: (1) partially condensing a feed stream having a pressure in the range of from 300 to 1500 psia and containing natural gas liquids, methane and nitrogen to produce a vapor stream A and a liquid stream B; (2) partially condensing stream A to produce a vapor stream C and a liquid stream D; (3) partially vaporizing stream B to produce a vapor stream E and a liquid stream F; (4) introducing streams D and F into a first demethanizer for separation into a methane-rich fraction and a bottom liquid containing natural gas liquids; (5) partially vaporizing said bottom liquid from the first demethanizer to produce a vapor stream G and a liquid stream H; (6) partially condensing streams C and E to produce a vapor stream I and a liquid stream J; (7) partially vaporizing stream J to produce a vapor stream K and a liquid stream L; (8) introducing stream L into a second demethanizer for separation into a methane-enriched fraction and a bottom liquid containing natural gas liquids; (9) partially vaporizing said bottom liquid from the second demethanizer to produce a vapor stream M and a liquid stream N; (10) introducing stream M into the second demethanizer; (11) introducing streams G and N into the first demethanizer; and (12) recovering stream H as product natural gas liquids whereby the presence of nitrogen and any changes which may occur in the concentration of nitrogen in the feed stream are prevented from having a significant impact in the hydrocarbon separation.

Claim 2

Dependent Claim 264 words

A process for the separation of natural gas liquids from methane and nitrogen comprising: (1) partially condensing a feed stream having a pressure in the range of from 300 to 1500 psia and containing natural gas liquids, methane and nitrogen to produce a vapor stream A and a liquid stream B; (2) partially condensing stream A to produce a vapor stream C and a liquid stream D; (3) partially vaporizing stream B to produce a vapor stream E and a liquid stream F; (4) introducing streams D and F into a first demethanizer for separation into a methane-rich fraction and a bottom liquid containing natural gas liquids; (5) partially vaporizing said bottom liquid from the first demethanizer to produce a vapor stream G and a liquid stream H; (6) partially condensing streams C and E to produce a vapor stream I and a liquid stream J; (7) partially vaporizing stream J to produce a vapor stream K and a liquid stream L; (8) introducing stream L into a second demethanizer for separation into a methane-enriched fraction and a bottom liquid containing natural gas liquids; (9) partially vaporizing said bottom liquid from the second demethanizer to produce a vapor stream M and a liquid stream N; (10) introducing stream M into the second demethanizer; (11) introducing streams G and N into the first demethanizer; and (12) recovering stream H as product natural gas liquids whereby the presence of nitrogen and any changes which may occur in the concentration of nitrogen in the feed stream are prevented from having a significant impact in the hydrocarbon separation.

Claim 3

Dependent Claim 12 words

The process of claim 1 wherein the feed stream additionally contains helium.

Claim 4

Dependent Claim 20 words

The process of claim 1 wherein the partial condensation of step (2) is carried out by turboexpansion of stream A.

Claim 5

Dependent Claim 21 words

The process of claim 1 wherein the partial vaporization of step (3) is carried out by valve expansion of stream B.

Claim 6

Dependent Claim 16 words

The process of claim 4 wherein partially vaporized stream B is heated after the valve expansion.

Claim 7

Dependent Claim 23 words

The process of claim 1 wherein said first demethanizer is operating at a pressure in the range of from 100 to 600 psia.

Claim 8

Dependent Claim 15 words

The process of claim 1 wherein the feed stream additionally contains hydrogen and/or unsaturated hydrocarbons.

Claim 9

Dependent Claim 30 words

The process of claim 1 wherein at least a portion of the methane-rich fraction from the first demethanizer is partially condensed and the liquid portion returned to said first demethanizer.

Claim 10

Dependent Claim 19 words

The process of claim 1 wherein the concentration of nitrogen in the feed stream is at least 10 percent.

Claim 11

Dependent Claim 24 words

The process of claim 1 wherein streams I and K are introduced into a nitrogen rejection unit for separation into nitrogen-rich and methane-rich streams.

Claim 12

Dependent Claim 14 words

The process of claim 10 wherein said nitrogen rejection unit is a double column.

Claim 13

Dependent Claim 14 words

The process of claim 10 Wherein said nitrogen rejection unit is a single column.

Claim 14

Dependent Claim 27 words

The process of claim 12 wherein said single column is driven by a heat pump employing a mixture of methane and nitrogen as the heat pump fluid.

Claim 15

Dependent Claim 34 words

The process of claim 1 wherein at least some of at least one of the methane-rich fraction from the first demethanizer and the methane-enriched fraction from the second demethanizer is recovered as product methane.

Claim 16

Dependent Claim 23 words

The process of claim 10 wherein at least some of the methane-rich stream from the nitrogen rejection unit is recovered as product methane.

Claim 17

Dependent Claim 20 words

The process of claim 1 wherein streams C and E are combined prior to the partial condensation of step (6).

Claim 18

Dependent Claim 161 words

A process for the separation of natural gas liquids from a feed stream having a pressure in the range of from 300 to 1500 psia and containing natural gas liquids, methane and not more than about 20 percent nitrogen comprising: (1) partially condensing said feed stream to produce a first vapor stream and a first liquid stream: (2) expanding to partially vaporize said first liquid stream; (3) heating said partially vaporized stream; (4) separating said partially vaporized stream into a second vapor stream and a second liquid stream; (5) partially condensing said first vapor stream to produce a third vapor stream and a third liquid stream; (6) introducing said second and third liquid streams into a demethanizer wherein they are separated into a methane-rich fraction and a bottom liquid containing natural gas liquids; (7) partially vaporizing said bottom liquid to provide vapor, for upflow through the demethanizer, and remaining liquid; and (8) recovering said remaining liquid as product natural gas liquids.

Claim 19

Dependent Claim 161 words

A process for the separation of natural gas liquids from a feed stream having a pressure in the range of from 300 to 1500 psia and containing natural gas liquids, methane and not more than about 20 percent nitrogen comprising: (1) partially condensing said feed stream to produce a first vapor stream and a first liquid stream: (2) expanding to partially vaporize said first liquid stream; (3) heating said partially vaporized stream; (4) separating said partially vaporized stream into a second vapor stream and a second liquid stream; (5) partially condensing said first vapor stream to produce a third vapor stream and a third liquid stream; (6) introducing said second and third liquid streams into a demethanizer wherein they are separated into a methane-rich fraction and a bottom liquid containing natural gas liquids; (7) partially vaporizing said bottom liquid to provide vapor, for upflow through the demethanizer, and remaining liquid; and (8) recovering said remaining liquid as product natural gas liquids.

Claim 20

Dependent Claim 22 words

The process of claim 17 wherein the partial condensation of step (5) is carried out by turboexpansion of the first vapor stream.

Claim 21

Dependent Claim 22 words

The process of claim 17 wherein the demethanizer is operating at a pressure in the range of from 100 to 600 psia.

Claim 22

Dependent Claim 31 words

The process of claim 17 wherein at least some of at least one of the second vapor stream, the third vapor stream and the methane-rich fraction is recovered as product methane.

Claim 23

Dependent Claim 35 words

The process of claim 17 wherein at least some of at least one of the second vapor stream, the third vapor stream and the methane-rich fraction is further separated into methane-richer and nitrogen richer fractions.

Claim 24

Dependent Claim 24 words

The process of claim 17 wherein the heating of step (3) is carried out by passing the partially vaporized stream against the feed stream.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-10-30	1988-04-30	1988-10-30	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-10-30	1992-04-30	1992-10-30	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-10-30	1996-04-30	1996-10-30	$7700.00	Window Closed / Lapsed

Process to separate natural gas liquids from nitrogen-containing natural gas

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