Configurations and methods for retrofitting an NGL recovery plant

• US 8,910,495 B2
• Filed: 06/20/2012
• Issued: 12/16/2014
• Est. Priority Date: 06/20/2011
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Primary Examiner(s): Ali, Mohammad M
• Assistant Examiner(s): RAYMOND, KEITH MICHAEL
• Application Number:
  US13/528,332
• Publication Number:
  US 20130014390A1
• Time in Patent Office: 909 Days
• Field of Search: 626/18, 626/20, 626/21, 626/23, 626/28, 626/30, 626/31, 626/57
• US Class Current: 62/631
• CPC Class Codes: C10G 2300/4056 Retrofitting operations
• CPC Class Codes: C10G 5/04 with liquid absorbents
• CPC Class Codes: C10G 5/06 by cooling or compressing
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: C10L 3/12 Liquefied petroleum gas liquefying by pressure and cold treatment F25J
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/40 Features relating to the provision of boil-up in the bottom of a column
• 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 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2280/02 Control in general, load changes, different modes ("runs"), measurements
• CPC Class Codes: F25J 2290/80 Retrofitting, revamping or debottlenecking of existing plant
• 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: F25J 3/0295 : Start-up or control of the process; Details of the apparatus used, e.g. sieve plates, packings
• CPC Class Codes: Y10T 29/49352 : Repairing, converting, servicing or salvaging
• CPC Class Codes: Y10T 29/53113 : Heat exchanger

Abstract

Devices and methods for retrofitting a natural gas liquids plant are contemplated to extend recovery of C3+ hydrocarbons from various feed gases to recovery of C2+ and C3+ hydrocarbons. In especially preferred aspects, dedicated C2+ exchangers are integrated to exclusively cool the feed gas to produce a cooled absorber feed and to produce two separate absorber reflux streams. During C2+ recovery, absorber reflux is provided by a portion of the residue gas and a portion of the feed gas, while during C3+ recovery absorber and distillation column reflux are provided by the distillation column overhead product.

Claims

1. A method of retrofitting a natural gas liquids plant for recovery of C2+ hydrocarbons, wherein the natural gas liquids plant has an absorber, a downstream distillation column, and a C3+ recovery exchanger that is configured to cool a feed gas and to cool an overhead product from the distillation column to thereby form a reflux stream for the absorber, and wherein a bottom product of the absorber is fed to the downstream distillation column, comprising:

installing a bypass circuit for the C3+ recovery exchanger that includes first and second dedicated C2+ recovery exchangers;

wherein the first C2+ recovery exchanger uses refrigeration content from an absorber overhead product to produce an ultra-lean reflux stream from a portion of compressed residue gas and a reflux stream from a portion of the feed gas;

wherein the second C2+ recovery exchanger uses refrigeration content from the absorber bottom product to produce a cooled feed gas from another portion of the feed gas; and

installing a bypass that routes the overhead product from the distillation column to the absorber as a stripping vapor.

2. The method of claim 1 further comprising a step of installing a conduit that provides a liquid portion of the cooled feed gas to the absorber.

3. The method of claim 1 further comprising a step of installing a control circuit that controls operation of switching valves to fluidly bypass the C3+ recovery exchanger when C2+ recovery is desired.

4. The method of claim 1 further comprising a step of using an overhead condenser of the distillation column to produce the cooled feed gas.

5. The method of claim 1 wherein a vapor portion of the cooled feed gas is expanded to absorber pressure prior to feeding the vapor portion into the absorber.

7. The method of claim 1 wherein at least one of the switching valves is a three-way valve.

8. The method of claim 1 further comprising a step of installing a control circuit that controls operation of the switching valves to bypass the C3+ recovery exchanger when C2+ recovery is desired.

9. The method of claim 1 further comprising a step of fluidly coupling an overhead condenser of the distillation column with the second C2+ recovery exchanger to produce the cooled feed gas from the second portion of the feed gas.

6. A method of retrofitting a natural gas liquids plant for recovery of C2+ hydrocarbons, wherein the natural gas liquids plant has an absorber, a downstream distillation column, and a C3+ recovery exchanger that is configured to cool a feed gas and to cool an overhead product from the distillation column to thereby form a reflux stream for the absorber, and wherein a bottom product of the absorber is fed to the downstream distillation column, comprising:

installing first and second dedicated C2+ recovery exchangers, piping, and a plurality of switching valves such that;

(a) flow of the feed gas is routable exclusively to the C3+ recovery exchanger or the first and second C2+ recovery exchangers;

wherein the C3+ recovery exchanger is configured to produce a cooled feed gas from the feed gas, wherein the first C2+ recovery exchanger is configured to produce a feed gas reflux stream from a first portion of the feed gas, and wherein the second C2+ recovery exchanger is configured to produce a cooled feed gas from a second portion of the feed gas;

(b) flow of the bottom product of the absorber is routable exclusively to the C3+ recovery exchanger or the second C2+ recovery exchanger to provide refrigeration content to the C3+ recovery exchanger or the second C2+ recovery exchanger;

(c) flow of an overhead product of the absorber is routable exclusively to the first C2+ recovery exchanger to provide refrigeration content to generate for the absorber an ultra-lean reflux stream from a portion of compressed residue gas; and

(d) flow of an overhead product of the distillation column is routable exclusively to the absorber as a stripping vapor, or to the absorber as the reflux stream for the absorber and the distillation column as a distillation column reflux.