Integration methods of gas processing plant and nitrogen rejection unit for high nitrogen feed gases

• US 10,359,230 B2
• Filed: 06/05/2017
• Issued: 07/23/2019
• Est. Priority Date: 10/24/2012
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Primary Examiner(s): Nguyen, Tam M
• Application Number:
  US15/614,407
• Publication Number:
  US 20170268819A1
• Time in Patent Office: 778 Days
• Field of Search: None
• CPC Class Codes: C10L 2290/08 Drying or removing water
• CPC Class Codes: C10L 2290/12 Regeneration of a solvent, catalyst, adsorbent or any other component used to treat or prepare a fuel
• CPC Class Codes: C10L 2290/46 Compressors or pumps
• CPC Class Codes: C10L 2290/48 Expanders, e.g. throttles or flash tanks
• CPC Class Codes: C10L 2290/541 Absorption of impurities during preparation or upgrading of a fuel
• CPC Class Codes: C10L 2290/545 Washing, scrubbing, stripping, scavenging for separating fractions, components or impurities during preparation or upgrading of a fuel
• CPC Class Codes: C10L 3/105 of nitrogen
• CPC Class Codes: F25J 2205/40 using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• CPC Class Codes: F25J 2205/50 using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil
• CPC Class Codes: F25J 2220/66 Separating acid gases, e.g. CO2, SO2, H2S or RSH
• CPC Class Codes: F25J 2240/44 the fluid being nitrogen
• CPC Class Codes: F25J 2245/42 the recycled stream being nitrogen
• 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 3/0257 separation of nitrogen from air F25J3/04, production of nitrogen in general C01B21/00
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Gas processing plants and methods are contemplated in CO₂ is effectively removed to very low levels from a feed gas to an NRU unit by adding a physical solvent unit that uses waste nitrogen produced by the NRU as stripping gas to produce an ultra-lean solvent, which is then used to treat the feed gas to the NRU unit. Most preferably, the physical solvent unit includes a flash unit and stripper column to produce the ultra-lean solvent.

Claims

1. A gas treatment plant for treatment of a feed gas that includes CO₂ and N₂, comprising:

a primary CO₂ removal unit configured to receive a feed gas from a feed gas source, and further configured to remove from the feed gas CO₂ to a first concentration to so form a treated feed gas;

a secondary CO₂ removal unit fluidly coupled to the primary CO₂ removal unit and configured to receive the treated feed gas, and further configured to use an ultra-lean solvent in an absorber to produce a CO₂-loaded solvent and a CO₂-depleted feed gas having residual CO₂ at a second concentration; and

a nitrogen rejection unit configured to remove N₂ from the CO₂-depleted feed gas and to produce a N₂ waste stream and a pipeline gas;

wherein the secondary CO₂ removal unit comprises a flash unit and a stripping column fluidly coupled to the absorber, wherein the flash unit is configured to flash the CO₂-loaded solvent and to produce a flashed solvent, and wherein the stripping column is configured to use the N₂ waste stream as a stripping gas for the flashed solvent to thereby produce the ultra-lean solvent.

2. The plant of claim 1, wherein the feed gas source is a hydrocarbon production well, and wherein the feed gas has a N₂ concentration of at least 10 mol % and a CO₂ concentration of at least 2 mol %.

3. The plant of claim 1, wherein the feed gas source is a hydrocarbon production well, and wherein the feed gas a pressure of at least 1000 psig.

4. The plant of claim 1, wherein the primary CO₂ removal unit comprises an amine absorber and an amine solvent regenerator, wherein the amine absorber produces a treated gas stream.

5. The plant of claim 4, wherein the primary CO₂ removal unit further comprises a drier which produces a dried stream from the treated gas stream.

6. The plant of claim 5, wherein the primary CO₂ removal unit further comprises a NGL unit which produces a NGL stream and a lean gas stream from the dried stream.

7. The plant of claim 6, wherein the primary CO₂ removal unit further comprises a compressor configured to compress the lean gas stream to form the treated feed gas.

8. The plant of claim 7, wherein the treated feed gas has a pressure of about 1,000 psig to 1,500 psig.

9. The plant of claim 1, wherein the flash unit in the secondary CO₂ removal unit is configured to operate at a pressure of equal to or less than 100 psig.

10. The plant of claim 1, wherein the flash unit comprises a hydraulic turbine.

11. The plant of claim 1, wherein the secondary CO₂ removal unit further comprises a compressor that is configured to increase a pressure of the N₂ waste stream prior to delivery of the N₂ waste stream to the stripping column.

12. The plant of claim 1, wherein the primary CO₂ removal unit is configured such that the treated feed gas has a CO₂ concentration of between 1-5 mol %.

13. The plant of claim 12, wherein the secondary CO₂ removal unit is configured such that the CO₂-depleted feed gas has a CO₂ concentration of equal to or less than 3,000 ppmv CO₂.

14. The plant of claim 1, wherein the primary CO₂ removal unit is configured such that the treated feed gas has a CO₂ concentration of between 1-5 mol %.

15. The plant of claim 14, wherein the secondary CO₂ removal unit is configured such that the CO₂-depleted feed gas has a CO₂ concentration of equal to or less than 1,000 ppmv CO₂.

16. The plant of claim 1, further comprising a blower configured to compress the N₂ waste stream to a pressure of about 5-50 psig for use as the stripping gas.