High propane recovery process and configurations

• US 6,837,070 B2
• Filed: 06/27/2001
• Issued: 01/04/2005
• Est. Priority Date: 08/11/2000
• Status: Expired due to Term

• Current Assignee: Fluor Enterprises Incorporated (Fluor Corporation)
• Original Assignee: Fluor Corporation
• Inventors: Mak, John
• Primary Examiner(s): Doerrler, William C.
• Application Number:
  US10/276,857
• Publication Number:
  US 20040025535A1
• Time in Patent Office: 1,287 Days
• Field of Search: 626/25, 626/30, 626/31, 626/32, 626/35, 626/36
• US Class Current: 62/625
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• 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 2220/66 Separating acid gases, e.g. CO2, SO2, H2S or RSH
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or 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 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• CPC Class Codes: F25J 2290/10 Mathematical formulae, modeling, plot or curves; Design methods
• CPC Class Codes: F25J 2290/12 Particular process parameters like pressure, temperature, ratios
• CPC Class Codes: F25J 2290/40 Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
• 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
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A gas processing plant has a de-ethanizer (106) and a refluxed absorber (103), wherein the absorber (103) operates at higher pressure than the de-ethanizer (106), and wherein at least a portion of the absorber bottoms product (7) is expanded to provide cooling for the absorber reflux stream and/or the distillation column feed stream. Especially contemplated gas processing plants include propane and ethane recovery plants, and where the gas processing plant is an ethane recovery plant, it is contemplated that the ethane product comprises no more than 500 ppm carbon dioxide.

Claims

1. A gas processing plant comprising:

a refluxed absorber operating at a first pressure, producing a bottoms product stream and receiving a feedstock and an absorber reflux stream;

a distillation column fluidly coupled to the absorber, receiving a distillation column feed stream, producing a distillation column overhead stream, and operating at a second pressure that is at least 100 psi lower an the first pressure; and

wherein at least a portion of the bottoms product stream is expanded and provides cooling for at least one of the absorber reflux stream and the distillation column feed stream; and

wherein the distillation column overhead stream is separated into a fluid portion that provides reflux for the distillation column an a gaseous portion that is liquefied and provides the absorber reflux stream.

2. The gas processing plant of claim 1 wherein the distillation column comprises a de-ethanizer column.

3. The gas processing plant of claim 2 wherein the feedstock is at a pressure of between 1000 psig and 2000 psig.

4. The gas processing plant of claim 3 wherein at least a portion of the feedstock is expanded in a turboexpander.

5. The gas processing plant of claim 3 wherein the bottoms product stream has a pressure and wherein expanding the bottoms product stream reduces the bottoms product stream pressure in a range of 100-250 psi.

6. The gas processing plant of claim 3 wherein the expanded bottoms product stream has a temperature between −

95°

F. to −

125°

F.

7. The gas processing plant of claim 3 wherein the expanded absorber bottoms product stream is fed as the distillation column feed stream in to the distillation column at a position that is at least three trays below an upmost tray of the distillation column.

8. The gas processing plant of claim 3 wherein the expanded bottoms product stream further provides cooling for a distillation column overhead stream.

9. The gas processing plant of claim 3 wherein the distillation column produces a distillation column overhead stream that is compressed, cooled, and fed into the absorber as the absorber reflux stream.

10. The gas processing plant of claim 3 wherein the feedstock comprises propane, and wherein the distillation column produces a distillation column product stream that comprises at least 95% of the propane in the feedstock.

11. The gas processing plant of claim 2 wherein the feedstock is at a pressure of between 550 psig and 800 psig.

12. The gas processing plant of claim 11 wherein the feedstock is fed into the absorber without passing through a turboexpander.

13. The gas processing plant of claim 11 wherein the bottoms product stream has a pressure and wherein expanding the bottoms product stream reduces bottoms product stream pressure in a range of 100-250 psi.

14. The gas processing plant of claim 11 wherein the bottoms product stream has a temperature between −

50°

F. to −

70°

F.

15. The gas processing plant of claim 11 wherein the expanded bottoms product stream is fed as the distillation column feed stream into the distillation column at a position that is at least three trays below an upmost tray in the distillation column.

16. The gas processing plant of claim 11 wherein at least a portion of the feedstock is fed into a lower section of the distillation column.

17. The gas processing plant of claim 11 further comprising an external refrigeration coupled to the distillation column.

18. The gas processing plant of claim 1 wherein the distillation column comprises a demethanizer.

19. The method of claim 18 wherein the feedstock is at a pressure of between 1000 psig and 2000 psig.

20. The gas processing plant of claim 18 wherein at least a portion of the feedstock is expanded in a turboexpander.

21. The gas processing plant of claim 18 wherein the bottoms product stream has a pressure and wherein expanding the bottoms product stream reduces the bottoms product stream pressure in a range of 100-250 psi.

22. The gas processing plant of claim 18 wherein the expanded bottoms product stream has a temperature between −

95°

F. to −

125°

F.

23. The gas processing plant of claim 18 wherein the expanded bottoms product stream is fed as the distillation column feed stream into the distillation column.

24. The gas processing plant of claim 18 wherein the distillation column produces a methane rich distillation column overhead stream that is compressed, cooled, and fed into the absorber as the absorber reflux stream.

25. The gas processing plant of claim 18 wherein the distillation column produces a distillation column product stream that comprises no more than 500 ppm carbon dioxide.

26. The gas processing plant of claim 18 wherein the feedstock is split into a first portion and a second portion, and wherein an external refrigeration cools at least part of the first portion.

27. The gas processing plant of claim 26 further comprising at least one side reboiler coupled to the distillation column, wherein the at least one side reboiler is fluidly coupled to the demethanizer between a top tray an a position eight trays below the top tray, provides heat duty for stripping CO₂ from demethanizer product stream, provides reboiling of the distillation column, and further provides cooling of the first portion of the feedstock.

28. The gas processing plant of claim 1, wherein the absorber and the distillation column are configured into a single tower configuration.