Flexible Ngl Process and Methods

• US 20070240450A1
• Filed: 10/05/2004
• Published: 10/18/2007
• Est. Priority Date: 10/30/2003
• Status: Active Grant

• Current Assignee: Fluor Enterprises Incorporated (Fluor Corporation)
• Original Assignee: Fluor Enterprises Incorporated (Fluor Corporation)
• Inventors: Mak, John
• Granted Patent: US 8,209,996 B2
• Time in Patent Office: Days
• US Class Current: 62/626
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 53/002 by condensation
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/78 Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2230/08 Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
• CPC Class Codes: F25J 2230/20 Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or a mixture of hydrocarbons
• CPC Class Codes: F25J 2235/60 the fluid being (a mixture of) hydrocarbons
• CPC Class Codes: F25J 2240/02 Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/12 External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/60 Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• CPC Class Codes: F25J 2280/02 Control in general, load changes, different modes ("runs"), measurements
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more

Abstract

Contemplated plants include an absorber in which the split ratio of various feed streams to an absorber are used to control recovery of a desired component in a bottom product of a distillation column that receives the bottom product of the absorber. In especially preferred aspects, the plant is an NGL plant and the split ratio of the feed streams used to control the level of desired ethane recovery.

Claims

1. A plant comprising:

an absorber that is configured to separately receive a first and a second portion of a feed gas vapor, a first and a second portion of a feed gas liquid, and a first and a second portion of a distillation column overhead;

wherein the first portion of the feed gas vapor and the first portion of the distillation column overhead provide reflux to the absorber; and

a control unit that controls a ratio of at least one of the first and second portion of the feed gas vapor, the first and second portion of the feed gas liquid, and the first and second portion of the distillation column overhead as a function of a desired recovery rate of a feed gas component in a bottom product of the distillation column.

2. The plant of claim 1 wherein the distillation column is configured to operate as at least one of a demethanizer and a deethanizer, and wherein the feed gas component in the bottom product is ethane.

3. The plant of claim 1 wherein the ratio determines absorber overhead temperature.

4. The plant of claim 1 wherein the absorber is configured to operate at an absorber pressure, wherein the distillation column is configured to operate at a distillation column pressure, and wherein the absorber pressure is greater than the distillation column pressure.

5. The plant of claim 4 wherein an absorber bottom product is expanded to provide at least a portion of feed gas chilling.

6. The plant of claim 1 wherein the second portion of the distillation column overhead is fed to the bottom of the absorber to thereby form a stripping gas stream.

7. The plant of claim 1 wherein the control unit controls a ratio of at least two of the first and second portion of the feed gas vapor, the first and second portion of the feed gas liquid, and the first and second portion of the distillation column overhead.

8. The plant of claim 1 wherein the control unit controls a ratio of the first and second portion of the feed gas vapor, the first and second portion of the feed gas liquid, and the first and second portion of the distillation column overhead.

9. The plant of claim 2 wherein ethane recovery in the bottom product increases when the first portion of the feed gas vapor increases relative to the second portion of the feed gas vapor.

10. The plant of claim 2 wherein ethane recovery in the bottom product increases when the first portion of the distillation column overhead decreases relative to the second portion of the distillation column overhead.

11. A method of operating a plant comprising:

providing an absorber and a distillation column, wherein the absorber receives a plurality of absorber feed streams and provides a bottom product to the distillation column;

splitting at least one of the feed streams into a first and second portion, and introducing the first and second portions at different locations to the absorber; and

using a flow ratio between the first and second portions to control recovery of a desired product in a bottom product of the distillation column.

12. The method of claim 11 further comprising a step of splitting another one of the feed streams into a first and second portion, and introducing the first and second portions at different locations to the absorber, and using a flow ratio between the first and second portions of the feed streams, respectively, to control recovery of the desired product in the bottom product of the distillation column.

13. The method of claim 11 wherein the plurality of feed streams comprises a natural gas liquids vapor and natural gas liquids liquid.

14. The method of claim 13 wherein the natural gas liquids vapor and natural gas liquids liquid are provided by a high-pressure separator.

15. The method of claim 13 wherein the desired product in the bottom product of the distillation column is ethane.

16. The method of claim 11 wherein the absorber is operated at a pressure that is higher than a pressure in the distillation column.

17. A method of operating a natural gas liquid plant, comprising:

providing an absorber that is fluidly coupled to a distillation column, wherein the absorber receives a feed gas vapor, a feed gas liquid, and an overhead product from the distillation column; and

feeding at least two of (a) a portion of the feed gas vapor, (b) a portion of the feed gas liquid, and (c) a portion of the overhead product to the absorber in a manner effective to control absorber overhead temperature such that ethane content in a bottom product of the distillation column increases when the absorber overhead temperature decreases.

18. The method of claim 17 wherein the absorber is operated at a pressure that is higher than a pressure in the distillation column.

19. The method of claim 17 wherein the portion of the feed gas vapor and the portion of the overhead product are used as absorber reflux.

20. The method of claim 17 wherein the portion of the feed gas vapor, the portion of the feed gas liquid, and the portion of the overhead product are fed to the absorber.