Acid gas fractionation

• US 5,983,663 A
• Filed: 05/08/1998
• Issued: 11/16/1999
• Est. Priority Date: 05/08/1998
• Status: Expired due to Term

• Current Assignee: Kvaerner Process Systems Canada Inc.
• Original Assignee: Kvaener Process Systems US Inc.
• Inventors: Sterner, Anthony J
• Primary Examiner(s): CAPOSSELA, RONALD C
• Application Number:
  US09/075,488
• Time in Patent Office: 557 Days
• Field of Search: 62/922, 62/928, 62/620
• US Class Current: 62/620
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/002 by condensation
• CPC Class Codes: F25J 2200/02 in a single 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 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/04 Mixing or blending of fluids with the feed stream
• CPC Class Codes: F25J 2215/04 Recovery of liquid products
• CPC Class Codes: F25J 2220/66 Separating acid gases, e.g. CO2, SO2, H2S or RSH
• CPC Class Codes: F25J 2220/82 Separating low boiling, i.e. more volatile components, e.g. He, H2, CO, Air gases, CH4
• 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 2270/12 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 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 3/0266 separation of carbon dioxide production of carbon dioxide in general C01B32/00
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y10S 62/922 Sulfur
• CPC Class Codes: Y10S 62/928 Recovery of carbon dioxide

Abstract

A process to bulk separate H₂ S and CO₂ from a sour gas by first cooling the inlet sour gas, passing the cooled sour gas through a separator and removing a liquid acid gas as a bottoms product in a fractionation tower, and then either pumping or free flowing the liquid acid gas into a disposal well. Potential sulphur deposition problems are controlled by recycling liquid acid gas to the plant inlet.

Claims

1. Process for the bulk removal of H₂ S and CO₂ from a sour gas stream, which comprises:

a) feeding a dry, sour gas stream containing a mixture of H₂ S and CO₂ Into a gas/gas exchanger and a chiller to cool the dry, sour gas;

b) feeding the cooled, dry, sour gas into a separator to obtain a gaseous top product and a condensed liquid acid gas bottoms product;

c) feeding the condensed liquid acid gas bottoms product to a fractionation tower, to strip further vapors from the condensed liquid acid gas bottoms product and obtain a pressurized, condensed liquid acid gas bottoms product and over head vapors; and

d) combining and mixing the gaseous top product from the separator and the overhead vapors from the fractionation column and feeding them into the gas/gas exchanger to exchange heat with the dry, sour gas stream.

2. The process of claim 1 wherein said gaseous top product from said separator is further cooled to a cryogenic level and fed to a further separator where a further condensed liquid acid gas is obtained as a bottoms products, which further condensed liquid acid gas bottoms product from said further separator is fed to said fractionation tower.

3. The process of claim 2 wherein said gaseous product from said separator is further cooled in a cold gas exchanger and the pressure thereof is dropped across a Joule-Thompson valve.

4. The process of claim 2 wherein said gaseous product from said separator is further cooled in a cold gas exchanger and the pressure thereof is dropped across a turbo-expander.

5. The process of claim 2 wherein said further condensed liquid acid gas bottoms product is at an elevated pressure, and may be pumped or free flowed into a disposal well.

6. The process of claim 5, further including a compressor to compress said dry, sour gas stream before said gas/gas exchanger and said chiller so as to raise the pressure of said dry, sour gas stream.

7. The process of claim 6 wherein said gaseous product from said separator is further cooled in a gas exchanger and the pressure thereof is dropped across a turbo-expander.

8. The process of claim 1, further including a mixer at said inlet to said gas/gas exchanger and said chiller, and mixing a portion of said pressurized condensed liquid acid gas bottoms product with said dry, sour gas stream to prevent or remove sulphur deposits.

9. The process of claim 1, further including a compressor to compress said dry, sour gas stream before said gas/gas exchanger and said chiller so as to raise the pressure of said dry, sour gas stream.

10. The process of claim 9 wherein said gaseous product from said separator is further cooled in a gas exchanger and the pressure thereof is dropped across a turbo-expander.

11. The process of claim 1, further including the step of pumping the pressurized, condensed liquid acid into a disposal well.

12. The process of claim 1, further including the step of free flowing the pressurized, condensed liquid acid gas bottoms product into a disposal well.

13. The process of claim 1 wherein the pressurized, condensed liquid acid gas bottoms product is at an elevated pressure, and may be pumped or free-flowed into a disposed well.

14. The process of claim 1 wherein the dry, sour gas stream has a combined H₂ S and CO₂ concentration greater than 10%.

15. The process of claim 14 wherein the dry, sour gas stream has a combined H₂ S and CO₂ concentration from 10% to 85%.

16. Process for the bulk removal of H₂ S and CO₂ from a sour gas stream which comprises:

a) feeding a dry, sour gas stream containing a mixture of H₂ S and CO₂ into an inlet to a gas/gas exchanger and a chiller, to cool the dry, sour gas;

b) feeding the cooled, dry, sour gas into a separator to obtain a gaseous top product, and a condensed liquid acid gas bottoms product;

c) feeding the condensed liquid acid gas bottoms product to a fractionation tower, to strip further vapors from the condensed liquid acid gas bottoms product and obtain a further condensed liquid acid gas bottoms product and overhead vapors;

d) cooling said gaseous top product from said separator to a cryogenic level and feeding said cooled gaseous top product to a further separator where further condensed liquid acid gas is obtained as a bottoms products and further overhead vapors are obtained;

the further condensed liquid acid gas bottoms product from said further separator being fed to said fractionation tower;

e) combining and mixing the further overhead vapors from the further separator and the overhead vapors from the fractionation column and feeding them into the gas/gas exchanger to exchange heat with the dry, sour gas stream; and

f) dropping the pressure of said gaseous product from said separator across a Joule-Thompson valve.

17. The process of claim 16, further including the step of mixing a portion of said pressurized condensed liquid acid gas bottoms product with said dry, sour gas stream at the inlet to the gas/gas exchanger.

18. The process of claim 16 wherein the dry, sour gas stream has a combined H₂ S and CO₂ concentration greater than 10%.

19. Process for the removal of H₂ S and CO₂ from a sour gas stream which comprises:

a) feeding a dry, sour gas stream containing a mixture of H₂ S and CO₂ into an inlet to a gas/gas exchanger and a chiller to cool the dry, sour gas;

b) feeding the cooled, dry, sour gas into a first separator to obtain a first gaseous top product, and a first condensed liquid acid gas bottoms product;

c) feeding the condensed liquid acid gas bottoms product to a fractionation tower, to strip further vapors from the first condensed liquid acid gas bottoms product and obtain a second pressurized condensed liquid acid gas bottoms product and overhead vapors;

d) cooling said first gaseous top product from said first separator to a cryogenic level in a cold gas exchanger and feeding said cooled first gaseous top product to a second separator where a second condensed liquid acid gas is obtained as a bottoms products, and a second gaseous top product;

the second condensed liquid acid gas bottoms product from said second separator being fed to said fractionation tower;

e) combining and mixing the second gaseous product from the second separator and the overhead vapors from the fractionation column and feeding them into the gas/gas exchanger to exchange heat with the dry, sour gas stream; and

f) dropping the pressure of said first gaseous top product from said first separator across a turbo-expander.

20. The process of claim 19 wherein the dry, sour gas stream has a combined H₂ S and CO₂ concentration from 10% to 85%.