Methods for removing contaminants from exhaust gases

Patent metadata

Field	Value
Publication number	US-9533256-B2
Application number	US-201414567262-A
Country	US
Kind code	B2
Filing date	Dec 11, 2014
Priority date	Dec 16, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A method for removing contaminants from a gas stream by feeding the gas stream into a scrubber that can use seawater as the scrubbing medium. The gas stream is first scrubbed with the seawater and then mixed with ozone to remove the contaminants. Nitrogen oxides that are present in the gas stream are converted to nitric acid/nitrates and these are recovered via condensate or coalesced mist for neutralization. The treated gas stream is then treated by a second scrubber whereby other contaminants such as sulfur oxides, particulates and the like are removed and the thus treated gas stream is exhausted to the atmosphere. Optionally a droplet separator may be present in the scrubber.

First claim

Having thus described the invention, what I claim is:

1. A method for removing contaminants from a gas stream comprising the steps:
a) Feeding the gas stream containing the contaminants into a scrubber;
b) Contacting the gas stream with a scrubbing solution;
c) Contacting the gas stream with ozone, wherein nitrogen oxides are oxidized;
d) Contacting the gas stream containing the oxidized nitrogen oxides with a device selected from the group consisting of a droplet separator and a condensing surface to provide sufficient surface area to dissolve, condense and absorb and, thereby removing the oxidized nitrogen oxides;
e) Contacting the gas stream with a scrubbing solution, thereby removing particulates, sulfur oxides, acid gases and mercury from the gas stream; and
f) Recovering the gas stream.

2. The method as claimed in claim 1 wherein the gas stream is a flue gas.

3. The method as claimed in claim 2 wherein the flue gas is from an onboard ship process or an industrial operation near a salt water ocean.

4. The method as claimed in claim 1 wherein the contaminants are selected from the group consisting of nitrogen oxides, sulfur oxides, particulates, acid gases, and mercury.

5. The method as claimed in claim 1 wherein the scrubber is selected from the group consisting of standard spray, venturi, rod, packed, bed, and plate column scrubbers.

6. The method as claimed in claim 1 wherein the scrubbing solution in step b) is sea water.

7. The method as claimed in claim 1 wherein the gas stream and ozone remain in contact for a time sufficient to avow oxidation of the nitrogen oxides to occur.

8. The method as claimed in claim 1 wherein the ozone is added in an amount greater than stoichiometric to the amount of nitrogen oxides present in the gas stream.

9. The method as claimed in claim 1 wherein droplets from the surface are recovered.

10. The method as claimed in claim 9 wherein the droplets that are recovered are drained, neutralized and collected for discharge or use.

11. The method as claimed in 10 wherein the recovered droplets are employed as fertilizer.

12. The method as claimed in claim 1 wherein the scrubbing solution in step e) is sea water.

13. The method as claimed in claim 1 further contacting the gas stream after step e) with a device selected from the group consisting of a droplet separator and a condensing surface.

14. The method as claimed in claim 1 wherein the scrubber is a once-through system.

15. The method as claimed in claim 1 wherein the scrubber is two scrubbers in fluid communication with each other.

16. The method as claimed in claim 1 wherein the scrubber further comprises a cooling coil, a mist eliminator and an electrostatic precipitator.

17. A method for removing contaminants from a gas stream comprising the steps:
a) Feeding the gas stream containing the contaminants into a scrubber;
b) Contacting the gas stream with a scrubbing solution;
c) Contacting the gas stream with ozone, wherein nitrogen oxides are oxidized; and
d) Contacting the gas stream containing the oxidized nitrogen oxides with a device selected from the group consisting of a droplet separator and a condensing surface to provide sufficient surface area to dissolve, condense and absorb and, thereby removing the oxidized nitrogen oxides.

18. The method as claimed in claim 17 wherein the gas stream is a flue gas.

19. The method as claimed in claim 18 wherein the flue gas is from an onboard ship process or an industrial operation near a salt water ocean.

20. The method as claimed in claim 17 wherein the contaminants are selected from the group consisting of nitrogen oxides, sulfur oxides, particulates, acid gases, and mercury.

21. The method as claimed in claim 17 wherein the scrubber is selected from the group consisting of standard spray, venturi, rod, packed, bed, and plate column scrubbers.

22. The method as claimed in claim 17 wherein the scrubbing solution in step b) is sea water.

23. The method as claimed in claim 17 wherein the gas stream and ozone remain in contact for a time sufficient to allow oxidation of the nitrogen oxides to occur.

24. The method as claimed in claim 17 wherein the ozone is added in an amount greater than stoichiometric to the amount of nitrogen oxides present in the gas stream.

25. The method as claimed in claim 17 wherein droplets from the surface are recovered.

26. The method as claimed in claim 25 wherein the droplets that are recovered are drained, neutralized and collected for discharge or use.

27. The method as claimed in 26 wherein the recovered droplets are employed as fertilizer.

28. The method as claimed in claim 17 wherein the scrubber is a once-through system.

29. The method as claimed in claim 17 wherein the scrubber further comprises a cooling coil, a mist eliminator and an electrostatic precipitator.

30. The method as claimed in 17 further comprising feeding the gas stream to a second scrubber after removing the oxidized nitrogen oxides.

31. The method as claimed in 30 wherein the gas stream is contacted in the second scrubber with a scrubbing solution, thereby removing particulates, sulfur oxides, acid gases and mercury from the gas stream and recovering the gas stream.

32. The method as claimed in claim 31 wherein the scrubbing solution is sea water.

33. The method as claimed in claim 30 further contacting the gas stream in the second scrubber with a device selected from the group consisting of a droplet separator and a condensing surface.

34. A method for removing contaminants selected from the group consisting of nitrogen oxides, sulfur oxides, particulates, acid gases and mercury from a flue gas stream comprising the steps:
a) Feeding the flue gas stream into a scrubber;
b) Contacting the flue gas stream with a sea water scrubbing solution;
c) Contacting the flue gas stream with ozone wherein the nitrogen oxides are oxidized;
d) Contacting the flue gas stream containing the oxidized nitrogen oxides with a device selected from the group consisting of a droplet separator and a condensing surface to provide sufficient surface area to dissolve, condense and absorb and, thereby removing the oxidized nitrogen oxides; and
e) Contacting the flue gas stream with a sea water scrubbing solution, thereby removing sulfur oxides, particulates, acid gases and mercury from the flue gas stream and recovering the flue gas stream.

Assignees

• Suchak Naresh J
• Linde Ag

Inventors

• Suchak Naresh J

Classifications

• B01D2257/602

  Mercury or mercury compounds · CPC title

• B01D53/56

  Nitrogen oxides (B01D53/60 takes precedence) · CPC title

• B01D2258/0283

  Flue gases · CPC title

• B01D53/78

  with gas-liquid contact · CPC title

• B01D2251/104

  Ozone · CPC title