Treatment of NO x -containing gas streams

• US 8,784,762 B2
• Filed: 02/15/2011
• Issued: 07/22/2014
• Est. Priority Date: 02/15/2011
• Status: Expired due to Fees

• Current Assignee: ATI Properties Incorporated (Allegheny Technologies Incorporated)
• Original Assignee: ATI Properties Incorporated (Allegheny Technologies Incorporated)
• Inventors: Moore, James A.
• Primary Examiner(s): Silverman, Stanley
• Assistant Examiner(s): BOVA, JUSTIN M
• Application Number:
  US13/027,312
• Publication Number:
  US 20120207665A1
• Time in Patent Office: 1,253 Days
• Field of Search: 423/239.1, 423/235, 423/242.1, 423/390.1, 423/393, 423/394.2
• US Class Current: 423/235
• 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:

generating a gas stream comprising NO_x from an acid pickling solution in an acid pickling tank, bath, or spray;

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

directly following the preceding step, reacting at least a portion of the nitrogen sesquioxide and nitrogen pentoxide with water in the first chamber, thereby forming nitric acid in the first chamber;

collecting at least a portion of the nitric acid in a second chamber in direct fluid communication with the first chamber; and

recycling the nitric acid from the second chamber into the acid pickling tank, bath, or spray;

wherein the gas stream comprising NO_x is not treated with a caustic scrubbing solution in a scrubber between generating the gas stream comprising NO_x and recycling the nitric acid.

2. The method of claim 1, wherein the acid pickling solution comprises nitric acid.

3. The method of claim 1, wherein the acid pickling solution has a temperature of at least 140°

F.

4. The method of claim 1, wherein generating the gas stream comprising NO_x comprises treating one of a metal and an alloy with the acid pickling solution.

5. The method of claim 4, wherein generating the gas stream comprising NO_x comprises treating one of stainless steel, titanium, and titanium alloys with the acid pickling solution.

6. The method of claim 1, further comprising mixing the gas stream comprising NO_x and the ozone with a mixing device.

7. The method of claim 6, wherein mixing the gas stream comprising NO_x and the ozone comprises mixing in a static mixer.

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

9. The method of claim 8, wherein water vapor is introduced into the mist eliminator.

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

13. The method of claim 1 comprising introducing the gas stream comprising NO_x to the first chamber at a first inlet and introducing the ozone to the first chamber at a second inlet.

14. The method of claim 13, wherein each of the ozone and the gas stream comprising NO_x have a flow rate of at least 500 cubic feet/min.

15. The method of claim 13 comprising introducing water to the first chamber at a third inlet.

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

generating a gas stream comprising NO_x from a pickling solution;

contacting the gas stream comprising NO_x with ozone in a first chamber to form oxidation products including nitrogen sesquioxide and nitrogen pentoxide;

directly following the preceding step, reacting at least a portion of the nitrogen sesquioxide and nitrogen pentoxide with water to form nitric acid;

collecting at least a portion of the nitric acid in a second chamber in direct fluid communication with the first chamber; and

recycling the nitric acid from the second chamber into a process or apparatus that generated the gas stream comprising NO_x;

wherein the gas stream comprising NO_x is not treated with a caustic scrubbing solution in a scrubber between generating the gas stream comprising NO_x and recycling the nitric acid.

12. The method of claim 11 comprising treating one of a metal and an alloy with a pickling solution comprising the recycled nitric acid.