CONFIGURATIONS AND METHODS FOR NGL RECOVERY FOR HIGH NITROGEN CONTENT FEED GASES

• US 20190154333A1
• Filed: 01/29/2019
• Published: 05/23/2019
• Est. Priority Date: 09/20/2012
• Status: Active Application

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Application Number:
  US16/260,288
• Publication Number:
  US 20190154333A1
• Time in Patent Office: Days
• 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 2200/76 Refluxing the column with condensed overhead gas being cycled in a quasi-closed loop refrigeration cycle
• 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 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• 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 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 3/0228 characterised by the separated product stream
• 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

Abstract

A low cost and efficient design is used to convert a propane recovery process based on low nitrogen content feed gas to an ethane recovery process based on a high nitrogen feed gas while achieving over 95 mole % ethane recovery while maintaining a 99% propane recovery, and achieved without additional equipment.

Claims

1. A NGL plant configured to convert from a propane recovery configuration to an ethane recovery configuration, the NGL plant comprising:

an absorber; and

a fractionator,

wherein the absorber is configured to produce an absorber overhead product and an absorber bottom product, wherein the fractionator is configured to produce a fractionator overhead product and a fractionator bottom product,

wherein the absorber is configured to receive a vapor portion of the fractionator overhead product as a top reflux in the propane recovery configuration and to receive a stream comprising a first portion of a feed gas and a first portion of the absorber overhead product as the top reflux in the ethane recovery configuration;

wherein the fractionator overhead product is configured to flow to a chiller in the propane recovery configuration and to a bottom of the absorber in the ethane recovery configuration; and

wherein the absorber bottom product is configured to flow to a mid-section of the fractionator in the propane recovery configuration and to a top tray of the fractionator in the ethane recovery configuration.

2. The NGL plant of claim 1, wherein the fractionator overhead product is further configured to flow to a separator after flowing to the chiller in the propane recovery configuration.

3. The NGL plant of claim 2, wherein the separator is configured to separate the fractionator overhead into the vapor portion and a liquid portion in the propane recovery configuration.

4. The NGL plant of claim 3, wherein the fractionator is configured to receive a first portion of the liquid portion of the fractionator overhead product at the top tray of the fractionator in the propane recovery configuration.

5. The NGL plant of claim 4, wherein the absorber is configured to receive a second portion of the liquid portion of the fractionator overhead product in the propane recovery configuration.

6. The NGL plant of claim 5, wherein the absorber is configured to receive the second portion as a second reflux below the top reflux in the propane recovery configuration.

7. The NGL plant of claim 1, wherein the absorber is configured to receive a vapor portion of the feed gas at a mid-section thereof in the propane recovery configuration, wherein the absorber is configured to receive a liquid portion of the feed gas at the bottom thereof in the propane recovery configuration.

8. The NGL plant of claim 7, wherein the feed gas is cooled and then separated in a separator configured to produce the vapor portion of the feed gas and the liquid portion of the feed gas in the propane recovery configuration.

9. The NGL plant of claim 7, wherein the liquid portion of the feed gas is let down in pressure and heated prior to flowing to the bottom of the absorber in the propane recovery configuration.

10. The NGL plant of claim 7, wherein the vapor portion of the feed gas is expanded prior to flowing to the mid-section of the absorber in the propane recovery configuration.

11. The NGL plant of claim 1, wherein the absorber is configured to receive a vapor portion of a second portion of the feed gas at a mid-section thereof in the ethane recovery configuration, wherein the absorber is configured to receive a liquid portion of the second portion of the feed gas at the bottom thereof in the ethane recovery configuration.

12. The NGL plant of claim 11, wherein the second portion of the feed gas is cooled and then separated in a separator configured to produce the vapor portion of the second portion and the liquid portion of the second portion in the ethane recovery configuration.

13. The NGL plant of claim 11, wherein the liquid portion of the second portion is let down in pressure and combined with the fractionator overhead product prior to flowing to the bottom of the absorber in the ethane recovery configuration.

14. The NGL plant of claim 11, wherein the vapor portion of the second portion is expanded prior to flowing to the mid-section of the absorber in the ethane recovery configuration.

15. A NGL plant configured to convert from a propane recovery configuration to an ethane recovery configuration, the NGL plant comprising:

an absorber;

a fractionator;

a first heat exchanger;

a separator;

an expander; and

a chiller,

wherein the absorber is configured to produce an absorber overhead product and an absorber bottom product,

wherein the fractionator is configured to produce a fractionator overhead product and a fractionator bottom product,

wherein in the propane recovery configuration;

the first heat exchanger is configured to cool a feed gas to form a cooled feed gas,

the separator is configured to separate the cooled feed gas into a first vapor stream and a first liquid stream,

the expander is configured to expand the first vapor stream to form an expanded first vapor stream, and

wherein the expanded first vapor stream is directed to a mid-section of the absorber, and the first liquid stream is directed to a bottom of the absorber;

wherein in the ethane recovery configuration;

the feed gas is split into a first portion and a second portion,

the first heat exchanger is configured to cool the first portion to form a cooled first portion, wherein the cooled first portion is fed to the absorber as a top reflux,

the chiller is configured to chill the second portion of the feed gas utilizing propane refrigeration to form a chilled second portion,

the first heat exchanger is configured to cool the chilled second portion to form a cooled second portion,

the separator is configured to separate the cooled second portion into a second vapor stream and a second liquid stream,

the expander is configured to expand the second vapor stream to form an expanded second vapor stream, and

wherein the expanded second vapor stream is fed to the mid-section of the absorber, and the second liquid stream is fed to the bottom of the absorber.

16. The NGL plant of claim 15, wherein, in the propane recovery configuration, the NGL plant is configured to let the first liquid stream down in pressure and then heat the first liquid stream prior to flowing to the bottom of the absorber, and wherein, in the ethane recovery configuration, the NGL plant is configured to the second liquid stream is let down in pressure and combined with the fractionator overhead product prior to flowing to the bottom of the absorber in the ethane recovery configuration.

17. The NGL plant of claim 15,

wherein the absorber is configured to receive a vapor portion of the fractionator overhead product as the top reflux in the propane recovery configuration and to receive a first portion of the absorber overhead product as part of the top reflux in the ethane recovery configuration;

wherein the fractionator overhead product is configured to flow to the chiller in the propane recovery configuration and to combine with the second liquid stream before flowing to the bottom of the absorber in the ethane recovery configuration; and

wherein the absorber bottom product is configured to flow to the mid-section of the fractionator in the propane recovery configuration and to a top tray of the fractionator in the ethane recovery configuration.

18. The NGL plant of claim 17, wherein the fractionator overhead product is further configured to flow to a second separator after flowing to the chiller in the propane recovery configuration, wherein the second separator is configured to separate the fractionator overhead into the vapor portion and a liquid portion in the propane recovery configuration.

19. The NGL plant of claim 18, wherein the fractionator is configured to receive a first portion of the liquid portion of the fractionator overhead product at the top tray of the fractionator in the propane recovery configuration, wherein the absorber is configured to receive a second portion of the liquid portion of the fractionator overhead product in the propane recovery configuration.

20. The NGL plant of claim 17, wherein the absorber overhead product is heated in the first heat exchanger before being split into the first portion of the absorber overhead product and a second portion of the absorber overhead product in the ethane recovery configuration, wherein the second portion of the absorber overhead product comprises a sales gas in the ethane recovery configuration.