Natural gas liquids (NGL) stabilization process

Claim 2

A process for stabilizing natural gas liquid (NGL) containing C 3+ hydrocarbons, comprising the following steps: (a) subjecting a raw NGL stream to phase separation by pressure reduction, thereby producing a stabilized NGL stream and a gas stream; (b) cooling said gas stream, thereby removing a portion of said C 3+ hydrocarbons as a liquid condensate from said gas stream, and leaving a non-condensed stream; (c) subjecting said non-condensed stream to membrane separation, thereby producing a product gas stream enriched in methane compared with said non-condensed stream, and a heavy stream enriched in C 3+ hydrocarbons compared with said non-condensed stream; (d) returning said heavy stream to bring said heavy stream into equilibrating contact with said raw NGL stream in step (a).

Claim 3

The process of claim 1, wherein said equilibrating contact is achieved in one theoretical partitioning stage.

Claim 4

The process of claim 1, wherein said equilibrating contact is achieved in multiple theoretical partitioning stages.

Claim 5

The process of claim 1, wherein said phase separation step (a) is carried out in a demethanizer column.

Claim 6

The process of claim 1, wherein said phase separation step (a) is carried out at a pressure of at least about 50 psia.

Claim 7

The process of claim 1, wherein said phase separation step (a) is carried out at a pressure of at least about 100 psia.

Claim 8

The process of claim 1, wherein said phase separation step (a) is carried out at a pressure of at least about 150 psia.

Claim 9

The process of claim 1, wherein said phase separation step (a) is carried out at a pressure of at least about 200 psia.

Claim 10

The process of claim 1, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream prior to passing said raw NGL stream into a phase separation vessel.

Claim 11

The process of claim 1, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream in a motionless mixer.

Claim 12

The process of claim 1, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream in an eductor.

Claim 13

The process of claim 1, wherein said equilibrating contact is achieved by running said heavy stream in countercurrent absorption/stripping contact against at least a portion of said raw NGL stream.

Claim 14

The process of claim 1, wherein said phase separation step (a) is carried out in a demethanizer column, and wherein said equilibrating contact is achieved by introducing said heavy stream into said demethanizer column.

Claim 15

The process of claim 1, wherein said membrane separation step (c) is carried out using a membrane selective for said C 3+ hydrocarbons over methane.

Claim 16

The process of claim 1, further comprising returning said liquid condensate to said phase separation step.

Claim 17

The process of claim 1, wherein said membrane separation step (c) removes at least about 10 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 18

The process of claim 1, wherein said membrane separation step (c) removes at least about 50 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 19

The process of claim 1, wherein said membrane separation step (c) removes at least about 90 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 20

The process of claim 1, further comprising compressing said gas stream prior to said membrane separation step (c).

Claim 21

The process of claim 1, further comprising compressing said gas stream prior to said cooling step (b).

Claim 22

The process of claim 1, further comprising passing said product gas stream to a gas pipeline.

Claim 23

The process of claim 1, wherein said phase separation step (a) is carried out in two sub-steps at progressively lower pressure, producing a first gas stream and a second, lower pressure gas stream, and wherein said cooling step (b) and said membrane separation step (c) are carried out on at least one of said first and second gas streams.

Claim 24

The process of claim 22, wherein at least portions of said first and second gas streams are combined for treatment in said membrane separation step (c).

Claim 25

The process of claim 1, wherein said cooling is achieved at least in part by heat exchange against said product gas stream.

Claim 26

The process of claim 1, wherein said cooling is achieved at least in part by heat exchange against said heavy stream.

Claim 27

A process for stabilizing natural gas liquid (NGL) containing C 3+ hydrocarbons, comprising the following steps: (a) subjecting a raw NGL stream to phase separation by pressure reduction, thereby producing a stabilized NGL stream and a gas stream; (b) compressing and cooling said gas stream, thereby removing a portion of said C 3+ hydrocarbons as a liquid condensate from said gas stream, and leaving a non-condensed stream; (c) subjecting said non-condensed stream to membrane separation, thereby producing a product gas stream enriched in methane compared with said non-condensed stream, and a heavy stream enriched in C 3+ hydrocarbons compared with said non-condensed stream; (d) returning said heavy stream to bring said heavy stream into equilibrating contact with said raw NGL stream in step (a).

Claim 28

A process for stabilizing natural gas liquid (NGL) containing C 3+ hydrocarbons, comprising the following steps: (a) subjecting a raw NGL stream to phase separation by pressure reduction, thereby producing a stabilized NGL stream and a gas stream; (b) compressing and cooling said gas stream, thereby removing a portion of said C 3+ hydrocarbons as a liquid condensate from said gas stream, and leaving a non-condensed stream; (c) subjecting said non-condensed stream to membrane separation, thereby producing a product gas stream enriched in methane compared with said non-condensed stream, and a heavy stream enriched in C 3+ hydrocarbons compared with said non-condensed stream; (d) returning said heavy stream to bring said heavy stream into equilibrating contact with said raw NGL stream in step (a).

Claim 29

The process of claim 26, wherein said equilibrating contact is achieved in one theoretical partitioning stage.

Claim 30

The process of claim 26, wherein said equilibrating contact is achieved in multiple theoretical partitioning stages.

Claim 31

The process of claim 26, wherein said phase separation step (a) is carried out in a demethanizer column.

Claim 32

The process of claim 26, wherein said phase separation step (a) is carried out at a pressure of at least about 50 psia.

Claim 33

The process of claim 26, wherein said phase separation step (a) is carried out at a pressure of at least about 100 psia.

Claim 34

The process of claim 26, wherein said phase separation step (a) is carried out at a pressure of at least about 150 psia.

Claim 35

The process of claim 26, wherein said phase separation step (a) is carried out at a pressure of at least about 200 psia.

Claim 36

The process of claim 26, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream prior to passing said raw NGL stream into a phase separation vessel.

Claim 37

The process of claim 26, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream in a motionless mixer.

Claim 38

The process of claim 26, wherein said equilibrating contact is achieved by mixing said heavy stream with said raw NGL stream in an eductor.

Claim 39

The process of claim 26, wherein said equilibrating contact is achieved by running said heavy stream in countercurrent absorption/stripping contact against at least a portion of said raw NGL stream.

Claim 40

The process of claim 26, wherein said phase separation step (a) is carried out in a demethanizer column, and wherein said equilibrating contact is achieved by introducing said heavy stream into said demethanizer column.

Claim 41

The process of claim 26, wherein said step (b) is carried out in two sub-steps as follows: (i) compressing and cooling said gas stream, thereby condensing a portion of said C 3+ hydrocarbons, and leaving an intermediate gas stream; (ii) compressing and cooling said intermediate gas stream, thereby removing a portion of said C 3+ hydrocarbons as a liquid condensate from said intermediate gas stream, and leaving a non-condensed stream.

Claim 42

The process of claim 39, wherein said non-condensed stream has a pressure of at least about 1,000 psia.

Claim 43

The process of claim 26, wherein said membrane separation step (c) is carried out using a membrane selective for said C 3+ hydrocarbons over methane.

Claim 44

The process of claim 26, wherein said non-condensed stream has a pressure of at least about 1,000 psia.

Claim 45

The process of claim 26, further comprising returning said liquid condensate to said phase separation step.

Claim 46

The process of claim 26, wherein said membrane separation step (c) removes at least about 10 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 47

The process of claim 26, wherein said membrane separation step (c) removes at least about 50 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 48

The process of claim 26, wherein said membrane separation step (c) removes at least about 90 vol % of the C 3+ hydrocarbons from the non-condensed stream into the heavy stream.

Claim 49

The process of claim 26, further comprising passing said product gas to a gas pipeline.

Claim 50

The process of claim 26, wherein said phase separation step (a) is carried out in two sub-steps at progressively lower pressure, producing a first gas stream and a second, lower pressure gas stream, and wherein said cooling step (b) and said membrane separation step (c) are carried out on at least one of said first and second gas streams.

Claim 51

The process of claim 48, wherein at least portions of said first and second gas streams are combined for treatment in said membrane separation step (c).

Claim 52

The process of claim 26, wherein said cooling is achieved at least in part by heat exchange against said product gas stream.

Claim 53

The process of claim 26, wherein said cooling is achieved at least in part by heat exchange against said heavy stream.

Claim 54

The process of claim 26, further comprising introducing an additional stream for treatment by said process at said compressing and cooling step (b).

Claim 55

Apparatus for stabilizing natural gas liquid (NGL) containing C 3+ hydrocarbons, comprising: (a) phase separator means having a fluid inlet by which fluid for separation can enter and a gas outlet from which gas can be withdrawn; (b) condensing means connected to an outlet from said phase separator means such that gas exiting said phase separator means can be cooled and partially condensed in said condensing means; (e) a membrane separation unit, containing a membrane having a feed side and a permeate side and being selective for said C 3+ hydrocarbons over methane, and connected to said condensing means such that non-condensed gas from said condensing means can flow across said feed side, and connected to said phase separator means such that gas from said permeate side can be returned to said phase separator means, in such a manner as to bring said gas from said permeate side into equilibrating contact with said fluid for separation in said phase separator means, and having a residue gas outlet from which gas can be withdrawn.

Claim 56

Apparatus for stabilizing natural gas liquid (NGL) containing C 3+ hydrocarbons, comprising: (a) phase separator means having a fluid inlet by which fluid for separation can enter and a gas outlet from which gas can be withdrawn; (b) condensing means connected to an outlet from said phase separator means such that gas exiting said phase separator means can be cooled and partially condensed in said condensing means; (e) a membrane separation unit, containing a membrane having a feed side and a permeate side and being selective for said C 3+ hydrocarbons over methane, and connected to said condensing means such that non-condensed gas from said condensing means can flow across said feed side, and connected to said phase separator means such that gas from said permeate side can be returned to said phase separator means, in such a manner as to bring said gas from said permeate side into equilibrating contact with said fluid for separation in said phase separator means, and having a residue gas outlet from which gas can be withdrawn.

Claim 57

The apparatus of claim 53, further comprising a compressor connected between said phase separator means and said condensing means.