TREATMENT OF NOx-CONTAINING GAS STREAMS

• US 20120207665A1
• Filed: 02/15/2011
• Published: 08/16/2012
• Est. Priority Date: 02/15/2011
• Status: Active Grant

• Current Assignee: ATI Properties Incorporated (Allegheny Technologies Incorporated)
• Original Assignee: ATI Properties Incorporated (Allegheny Technologies Incorporated)
• Inventors: Moore, James A.
• Granted Patent: US 8,784,762 B2
• Time in Patent Office: Days
• US Class Current: 423/393
• CPC Class Codes: B01D 2251/104 Ozone
• CPC Class Codes: B01D 53/56 Nitrogen oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/8631 Processes characterised by a specific device
• CPC Class Codes: C01B 21/40 Preparation by absorption of oxides of nitrogen C01B21/26 takes precedence
• CPC Class Codes: C23G 1/02 with acid solutions

Abstract

Methods and systems for treating a gas stream comprising NO_x are disclosed. In one embodiment of the method, the gas stream comprising NO_x is reacted with ozone to form oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is reacted with water to form nitric acid, and a solubilized form of the nitric acid is collected and may be reused or otherwise utilized. Systems for conducting the method also are disclosed.

Claims

1. A method of treating a gas stream comprising NO_x, the method comprising:

contacting a gas stream comprising NO_x with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide;

reacting at least a portion of the nitrogen sesquioxide and nitrogen pentoxide with water, thereby forming nitric acid;

collecting at least a portion of the nitric acid.

2. The method of claim 1, wherein the gas stream comprising NO_x is generated from an acid pickling solution.

3. The method of claim 2, wherein the pickling solution comprises nitric acid.

4. The method of claim 2, wherein the pickling solution has a temperature of at least 140°

F.

5. The method of claim 2, wherein the pickling solution is used to treat materials selected from metals and alloys.

6. The method of claim 5, wherein the pickling solution is used to treat materials selected from stainless steel, titanium, and titanium alloys.

7. The method of claim 1, wherein contacting the gas stream comprising NO_x with the ozone comprises mixing the gas stream comprising NO_x and the ozone.

8. The method of claim 7, wherein mixing the gas stream comprising NO_x and the ozone comprises mixing using a static mixer.

9. The method of claim 1, wherein collecting at least a portion of the nitric acid comprises collecting solubilized nitric acid using a mist eliminator.

10. The method of claim 9, wherein water vapor is introduced into the mist eliminator.

11. The method of claim 1, further comprising recycling the nitric acid into a process or apparatus that generated the gas stream comprising NO_x.

12. The method of claim 1, further comprising recycling the nitric acid into an acid pickling tank, bath or spray that generated the gas stream comprising NO_x.

13. The method of claim 1, wherein a flow rate of the gas stream comprising NO_x is at least 500 cubic feet/min.

14. A system for treating a gas stream comprising NO_x, the system comprising:

a first chamber including

a first inlet communicating with a source of a gas comprising NOx,

a second inlet communicating with a source of ozone, and

an interior volume adapted to contact the gas comprising NOx with the ozone, thereby producing oxidation products including nitrogen sesquioxide and nitrogen pentoxide, wherein at least a portion of the nitrogen sesquioxide and nitrogen pentoxide react with water in the first chamber to form nitric acid; and

a second chamber directly fluidly communicating with the first chamber and receiving gaseous effluent from the first chamber, the second chamber including

a third inlet communicating with a source of water vapor,

an interior volume adapted to contact gases from the first chamber with the water vapor, thereby solubilizing nitric acid in the gaseous effluent from the first chamber with the water vapor, and

an outlet for collecting solubilized nitric acid from the interior volume of the second chamber.

15. The system of claim 14, further comprising at least one of a pickling tank, bath, or spray wherein the pickling tank, bath, or spray generates the gas stream comprising NO_x that is introduced into the first chamber through the first inlet.

16. The system of claim 15, wherein the pickling tank or bath includes an acid pickling solution comprising nitric acid.

17. The system of claim 15, wherein the pickling tank, bath, or spray is used to treat surfaces of materials selected from metals and alloys.

18. The system of claim 15, wherein the pickling tank, bath, or spray is used to treat surfaces of materials selected from stainless steel, titanium, and titanium alloys.

19. The system of claim 14, wherein the first chamber includes a static mixer adapted to mix the gas stream comprising NO_x and the ozone in the interior volume of the first chamber.

20. The system of claim 14, wherein the first chamber further comprises a third inlet that communicates with a source of water vapor.

21. The system of claim 14, wherein the source of ozone is an ozone generator.

22. The system of claim 14, wherein the second inlet is located adjacent the first inlet.

23. The system of claim 14, wherein a diameter of the first chamber is at least 24 inches.

24. The system of claim 14, wherein the second chamber is a mist eliminator.

25. The system of claim 14, further comprising a scrubber, wherein the scrubber neutralizes nitric acid using a caustic solution.