CO.sub.2 removal from high CO.sub.2 content hydrocarbon containing streams

• US 4,529,411 A
• Filed: 04/30/1984
• Issued: 07/16/1985
• Est. Priority Date: 03/12/1982
• Status: Expired due to Fees

• Current Assignee: Amoco Corporation (BP PLC)
• Original Assignee: Standard Oil Company (BP PLC)
• Inventors: Turek, Edward A., George, Boyd A., Goddin, Clifton S. Jr.
• Primary Examiner(s): SPITZER, ROBERT H
• Application Number:
  US06/605,716
• Time in Patent Office: 442 Days
• Field of Search: 55/16, 55/68, 55/73, 62/17, 62/19, 62/20, 62/24, 62/44
• US Class Current: 95/51
• CPC Class Codes: B01D 53/1412 Controlling the absorption process
• CPC Class Codes: B01D 53/1443 Pretreatment by diffusion
• CPC Class Codes: B01D 53/1462 Removing mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y10S 62/929 From natural gas

Abstract

Carbon dioxide is removed from CO₂ and hydrocarbon containing gaseous streams. In the instance where the hydrocarbons and CO₂ are such that hydrocarbons would condense out during CO₂ removal, the gas stream is treated in one or more stages to accomplish hydrocarbon composition control.

Claims

1. Process for treating a gaseous stream comprising:

(a) separating a first portion of predominantly higher (C₃ and heavier) hydrocarbons from a gaseous stream such that hydrocarbon condensation does not occur from the resulting stream comprising CO₂ and at least C₁ and C₂ hydrocarbons during CO₂ removal during Step (b) hereinafter set forth, the gaseous stream comprising CO₂ and hydrocarbons including at least C₁ and C₂ hydrocarbons, and further including C₃ and heavier hydrocarbons such that hydrocarbon condensation occurs during removal of CO₂ unless the gaseous stream is treated prior to CO₂ removal to remove said first portion of the hydrocarbons;

then

(b) introducing said resulting stream comprising CO₂ and at least C₁ and C₂ hydrocarbons into a permeation zone and separating a first portion of CO₂ from said resulting stream in the permeation zone by selective permeation of CO₂ across a differentially permeable membrane to produce a CO₂ permeate stream and a hydrocarbon enriched first stream comprising C₁ and C₂ hydrocarbons; and

(c) further separating CO₂ from the hydrocarbon enriched first stream in at least one CO₂ removal zone by cryogenically fractionating the hydrocarbon enriched first stream to produce at least a C₁ stream and a CO₂ stream.

2. Process as in claim 1 wherein

the gaseous stream comprises in excess of about 30 mol % CO₂.

3. Process as in claim 2 wherein

the separating of Step (a) of claim 1 is by chilling the gaseous stream to a temperature such that the hydrocarbon dewpoint temperature profile during permeation is less than the temperature of the hydrocarbon enriched first stream produced in Step (b).

4. Process as in claim 3 wherein

the gaseous stream is chilled to a temperature such that the hydrocarbon dewpoint temperature profile is at least 10°

F. less than the temperature of the thus produced hydrocarbon enriched first stream.

5. Process as in claim 2 comprising

chilling the gaseous stream to separate said portion of hydrocarbons from the gaseous stream to produce a chilled gaseous second stream;

heating the thus chilled gaseous second stream to a temperature effective for maintaining the hydrocarbon dewpoint temperature profile during CO₂ removal in a permeation zone such that hydrocarbon condensation does not occur during CO₂ removal in said permeation zone;

separating a first portion of CO₂ from the thus heated gaseous second stream in a permeation zone by selective permeation of CO₂ across a differentially permeable membrane to produce a CO₂ permeate stream and a hydrocarbon enriched first stream; and

chilling the hydrocarbon enriched first stream to a temperature effective for cryodemethanizing.

6. Process as in claim 5 wherein

the chilled gaseous second stream is heated in heat exchange relation with the hydrocarbon enriched second stream.

7. Process as in claim 1 wherein

the gaseous stream comprises in the range of about 30 mol % CO₂ to about 95 mol % CO₂.

8. Process as in claim 1 wherein

the gaseous stream comprises in the range of about 30 mol % CO₂ to about 60 mol % CO₂.

9. Process as in claim 1 wherein

the gaseous stream is a gaseous stream from a CO₂ miscible flood produced reservoir and is characterized by containing greater than about 30 mol % CO₂ and by a variable C₃ and heavier hydrocarbon composition.

10. Process as in claim 1 wherein

the gaseous stream is further characterized by a generally increasing C₄ and heavier hydrocarbon fraction as a function of increased CO₂ content in the gaseous stream from the CO₂ miscible flood produced reservoir.

11. Process as in claim 1 comprising:

introducing the hydrocarbon enriched first stream into a cryodemethanizer column and separating C₁ hydrocarbon from CO₂ and other components of the hydrocarbon enriched first stream.

12. Process as in claim 11, further comprising:

introducing a stream comprising hydrocarbons removed from the gaseous stream during Step (a) of claim 1 at an intermediate level into the cryodemethanizer column.

13. Process as in claim 11 comprising:

chilling the gaseous stream to separate said first portion of hydrocarbons from the gaseous stream to produce a chilled gaseous second stream;

heating the thus chilled gaseous second stream to a temperature effective for maintaining the hydrocarbon dewpoint temperature profile during CO₂ removal in the permeation zone such that hydrocarbon condensation does not occur during CO₂ removal in the permeation zone;

separating a first portion of CO₂ from the thus heated gaseous second stream in the permeation zone by selective permeation of CO₂ across a differentially permeable membrane to produce a CO₂ permeate stream and a hydrocarbon enriched first stream;

chilling the hydrocarbon enriched first stream to a temperature effective for cryodemethanizing; and

cryogenically fractionating the hydrocarbon enriched first stream to produce a C₁ stream and a CO₂ stream.

14. Process as in claim 13 further comprising:

introducing a stream comprising hydrocarbons removed from the gaseous stream during Step (a) of claim 1 at an intermediate level into the cryodemethanizer column.