Method and an apparatus for removing carbon dioxide form sulphur dioxide containing flue gases

• US 20060286011A1
• Filed: 06/13/2006
• Published: 12/21/2006
• Est. Priority Date: 06/15/2005
• Status: Active Grant

• Current Assignee: Metso Paper Oy (Metso Corporation)
• Original Assignee: Kvaerner Power Oy
• Inventors: Anttila, Mikko, Tuominiemi, Seppo, Hamalainen, Risto
• Granted Patent: US 7,910,079 B2
• Time in Patent Office: Days
• US Class Current: 422/168
• CPC Class Codes: B01D 2251/304 of sodium
• CPC Class Codes: B01D 2251/606 Carbonates
• CPC Class Codes: B01D 53/502 characterised by a specific solution or suspension
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: F23J 15/04 using washing fluids scrubbers for removing solids only F23J15/022
• CPC Class Codes: F23J 2215/50 Carbon dioxide
• CPC Class Codes: F23J 2219/40 Sorption with wet devices, e.g. scrubbers
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02E 20/32 Direct CO2 mitigation

Abstract

A method and an apparatus for removing carbon dioxide (CO₂) from sulphur dioxide containing (SO₂) flue gases, wherein the flue gases are washed with washing solution in a scrubber, which comprises at least two washing stages. In the first washing stage the flue gases are washed for removing the sulphur dioxide in the flue gases and after that in the second washing stage for removing carbon dioxide (CO₂). Sodium carbonate solution (Na₂CO₃) is used as washing solution in both the first and the second washing stages.

Claims

1. A method for removing carbon dioxide (CO₂) from sulphur dioxide (SO₂) containing flue gases, in which method the flue gases are washed with washing solution in a scrubber, which comprises at least two washing stages, wherein the flue gases are washed in the first washing stage removing sulphur dioxide in the flue gases and after that in the second washing stage for removing carbon dioxide (CO₂), wherein both in the first and the second washing stages sodium carbonate solution (Na₂CO₃) is used as washing solution.

2. The method according to claim 1, wherein the flue gases are washed in the flow direction of the flue gases first in the first washing stage and after that in the second washing stage.

3. The method according to claim 1, wherein the sodium bicarbonate solution (NaHCO₃) formed as a result of washing in the second washing stage is led to the stripper where it is processed in order to form a solution containing sodium carbonate and carbon dioxide gas.

4. The method according to claim 3, wherein the sodium carbonate solution formed in the stripper is led to the first and the second washing stage of the scrubber.

5. The method according to claim 3, wherein the sodium bicarbonate solution is processed in the stripper with steam.

6. The method according to claim 1, wherein sodium hydroxide solution (NaOH) is led to the second washing stage in order to form sodium carbonate solution.

7. The method according to claim 1, wherein the sodium sulphite (Na₂SO₃) and sodium bisulphite (Na₂HSO₃) containing solution formed in the first washing stage is removed.

8. The method according to claim 3, wherein the sodium bicarbonate solution is heated with at least one heat exchanger before it is led to the stripper.

9. The method according to claim 3, wherein the sodium bicarbonate solution is cooled with at least one heat exchanger before it is led to the second washing stage.

10. The method according to claim 8, wherein an external heat exchange medium circulation is used for heating the sodium bicarbonate solution.

11. The method according to claim 9, wherein an external heat exchange medium circulation is used for cooling the sodium carbonate solution.

12. The method according to claim 8, wherein a heat exchange medium is used in heating the sodium carbonate solution, which medium has absorbed heat in at least one heat exchanger that is a part of the heat exchange medium circulation.

13. An apparatus for removing carbon dioxide (CO₂) from sulphur dioxide (SO₂) containing flue gases, which apparatus comprises a scrubber, which comprises at least two washing stages, which comprise nozzles for spraying washing solution to the flue gases, wherein the flue gases are arranged to be washed in the first washing stage for removing sulphur dioxide (SO₂) in the flue gases and after that in the second washing stage for removing carbon dioxide (CO₂), wherein both in the first and the second washing stages sodium carbonate solution is arranged to be used as washing solution.

14. The apparatus according to claim 13, wherein the first washing stage is arranged in the flow direction of the flue gases of the scrubber before the second washing stage.

15. The apparatus according to claim 13, wherein the apparatus comprises a stripper, to which the sodium bicarbonate solution formed as a result of washing in the second washing stage is arranged to be led for forming sodium carbonate solution and carbon dioxide gas.

16. The apparatus according to claim 15, wherein the sodium carbonate solution formed in the stripper is arranged to be led to the first and to the second washing stage of the scrubber.

17. The apparatus according to claim 15, wherein the sodium bicarbonate solution is arranged to be processed in the stripper with steam.

18. The apparatus according to claim 13, wherein the apparatus comprises a line for leading the sodium hydroxide (NaOH) solution to the second washing stage of the scrubber.

19. The apparatus according to claim 13, wherein the apparatus comprises a line for removing the sodium sulphite (Na₂SO₃) and sodium bisulphite (Na₂HSO₃) containing solution formed in the first washing stage.

20. The apparatus according to claim 15, wherein the apparatus comprises at least one heat exchanger for heating the sodium bicarbonate solution before it is led to the stripper.

21. The apparatus according to claim 15, wherein the apparatus comprises at least one heat exchanger for cooling the sodium carbonate solution before it is led to the second washing stage.

22. The apparatus according to claim 20, wherein the apparatus comprises an external heat exchange medium circulation, which comprises at least one heat exchanger and at least one line conveying heat exchange medium between the heat exchangers, which heat exchange medium circulation is arranged to heat the sodium bicarbonate solution.

23. The apparatus according to claim 21, wherein the apparatus comprises an external heat exchange medium circulation, which comprises at least one heat exchanger and at least one line conveying heat exchange medium between the heat exchangers, which heat exchange medium circulation is arranged to cool the sodium carbonate solution.

24. The apparatus according to claim 20, wherein the heat exchange medium circulation comprises at least one heat exchanger, wherein the heat exchange medium flowing through it has absorbed heat in at least one heat exchanger belonging to the heat exchange medium circulation, and that the heat exchanger is arranged to heat sodium carbonate solution.