Process for separation of CO.sub.2 from CO.sub.2 -containing gases

• US 4,528,002 A
• Filed: 04/23/1984
• Issued: 07/09/1985
• Est. Priority Date: 04/21/1983
• Status: Expired due to Fees

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: Linde, Gerhard
• Primary Examiner(s): Hart, Charles
• Application Number:
  US06/602,884
• Time in Patent Office: 442 Days
• Field of Search: 55/40, 55/43, 55/46, 55/48, 55/51, 55/68, 55/73, 62/17, 62/27, 62/23, 62/24
• US Class Current: 95/174
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y10S 62/928 Recovery of carbon dioxide

Abstract

For separating CO₂ from CO₂ -containing gases, especially stack gases and/or blast furnace gases, dimethylformamide is employed as a physical scrubbing medium to ensure high CO₂ purity. After absorption of CO₂, the DMF is regenerated and returned into the scrubbing stage. Dimethylformamide is utilized as the scrubbing medium.

Claims

1. In a process for separating CO₂ from a CO₂ -containing gas, said process comprising scrubbing said gas in a scrubbing stage with dimethylformamide to absorb CO₂, regenerating resultant loaded dimethylformamide in a regeneration stage to remove CO₂, and compressing the CO₂ to medium and then to high pressure in a plurality of pressure stages, wherein the regeneration stage is conducted by pressure reduction and heating of the loaded dimethylformamide and recycling regenerated dimethylformamide into the scrubbing stage, the improvement which comprises heating the loaded dimethylformamide in heat exchange with a partial stream of the product CO₂ at a medium pressure, thereby liquefying the medium-pressure CO₂.

2. A process according to claim 1, wherein said scrubbing stage is conducted under a pressure of 1.5-3 bar and at a temperature of -30°

to -60°

C.

3. A process according to claim 2, wherein the regeneration of the scrubbing medium is conducted under a pressure of 0.05-0.3 bar and at a temperature of between -60°

C. and -10°

C.

4. A process according to claim 2, comprising recompressing the CO₂ liberated during regeneration in a plurality of compression stages, including a medium pressure level and a high pressure level.

5. A process according to claim 1, wherein the liquefied CO₂ is expanded and then vaporized in a cooling coil in heat exchange with the dimethylformamide in the scrubbing stage, so as to remove the heat of absorption of the CO₂ within the scrubbing stage.

6. A process according to claim 1, wherein the CO₂ -containing gas also contains SO₂, and a partial stream of partially regenerated dimethylformamide is further regenerated in a separate stage to remove SO₂ by heating at a higher temperature than the CO₂ -removal regeneration stage.

7. A process according to claim 1, further comprising pressure reducing, vaporizing, and withdrawing the liquefied CO₂.

8. A process according to claim 1, further comprising, prior to the scrubbing step, cooling the CO₂ -containing gas reversible regenerators.

9. A process according to claim 1, wherein the CO₂ -containing gas to be scrubbed contains at least about 8 percent by volume.

10. A process according to claim 9, wherein the CO₂ -containing gas is a stack gas.

11. A process according to claim 9, wherein the CO₂ -containing gas is a blast furnace gas.

12. In a process for separating CO₂ from a CO₂ -containing gas, said process comprising scrubbing said gas in a scrubbing stage with dimethylformamide to absorb CO₂, regenerating resultant loaded dimethylformamide in a regeneration stage to remove CO₂, wherein the regeneration stage is conducted by pressure reduction and heating of the loaded dimethylformamide and recycling regenerated dimethylformamide into the scrubbing stage, the improvement which comprises heating the loaded dimethylformamide in heat exchange with a partial stream of the product CO₂ thereby liquefying the CO₂, and expanding the liquified CO₂ and then vaporizing it in a cooling coil in heat exchange with the dimethylformamide in the scrubbing stage, so as to remove the heat of absorption of the CO₂ within the scrubbing stage.

13. In a process for separating CO₂ from a CO₂ and SO₂ -containing gas, said process comprising scrubbing said gas in a scrubbing stage with dimethylformamide to absorb CO₂, regenerating resultant loaded dimethylformamide in a regeneration stage to remove CO₂, wherein the regeneration stage is conducted by pressure reduction and heating of the loaded dimethylformamide and recycling regenerated dimethylformamide into the scrubbing stage, the improvement which comprises heating a partial stream of partially regenerated dimethylformamide to remove SO₂ in a separate stage at a higher temperature than the CO₂ -regeneration stage and heating the remaining loaded dimethylformamide in heat exchange with a partial stream of the product CO₂ thereby liquefying the CO₂.