SYSTEMS AND METHODS FOR RECOVERING NITRIC ACID FROM PICKLING SOLUTIONS

• US 20120207664A1
• Filed: 09/13/2011
• 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 8,795,620 B2
• Time in Patent Office: Days
• US Class Current: 423/391
• CPC Class Codes: B01D 2251/104 Ozone
• CPC Class Codes: B01D 2252/103 Water
• CPC Class Codes: B01D 53/56 Nitrogen oxides B01D53/60 takes precedence
• 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
• CPC Class Codes: C23G 1/086 solutions containing HF
• CPC Class Codes: C23G 1/36 Regeneration of waste pickling liquors

Abstract

An embodiment of a method for recovering nitric acid from acid pickling solution includes introducing a treating material comprising at least one chemical into a pickling solution comprising free nitric acid. The treating material reacts with at least a portion of the free nitric acid in the pickling solution and produces NO_x. A gas stream comprising at least a portion of the NO_x is contacted with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is contacted with water, thereby forming nitric acid, and at least a portion of the nitric acid is collected.

Claims

1. A method for recovering nitric acid from acid pickling solution, the method comprising:

introducing a treating material comprising at least one chemical into an pickling solution comprising free nitric acid, wherein the treating material reacts with at least a portion of the free nitric acid in the pickling solution and produces NO_x;

contacting a gas stream comprising at least a portion of the 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 treating material comprises at least one chemical selected from the group consisting of ferrous sulfate, carbon steel, and iron.

3. The method of claim 1, wherein the pickling solution is disposed in a pickling tank or bath.

4. The method of claim 1, wherein the pickling solution is a pickling solution used in spray pickling.

5. The method of claim 1, wherein at least a portion of NO_x produced by the reaction between the treating material and the pickling solution enters gases in the headspace above the pickling solution, and wherein the gas stream includes NO_x from the headspace.

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

F.

7. The method of claim 1, wherein the pickling solution is used to treat materials selected from metals and alloys.

8. The method of claim 1, wherein the pickling solution is used to treat materials selected from stainless steel, titanium, and titanium alloys.

9. 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.

10. The method of claim 9, wherein mixing the gas stream comprising NO_x and the ozone comprises mixing using a static mixer.

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

12. The method of claim 11, wherein water vapor is introduced into the mist eliminator.

13. The method of claim 1, further comprising introducing at least a portion of the collected nitric acid back into the pickling solution.

14. 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.

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

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

a) a pickling apparatus selected from a pickling bath, a pickling tank, and a pickling spray device, the pickling apparatus including an acid pickling solution, the pickling apparatus comprising

an inlet adapted for introducing treating material into contact with the acid pickling solution, wherein the treating material reacts with nitric acid to form NO_x, and

a headspace in which gas comprising NO_x collects;

b) a first chamber including

an interior volume

a first inlet communicating with the headspace of the pickling apparatus and adapted to convey at least a portion of the gas comprising NO_x from the headspace to the interior volume,

a second inlet communicating with a source of ozone, and

wherein the interior volume is adapted to contact the gas comprising NO_x 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

c) 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.

17. The system of claim 16, wherein the pickling apparatus includes an acid pickling solution comprising nitric acid.

18. The system of claim 17, wherein the pickling apparatus is used to treat surfaces of materials selected from metals and alloys.

19. The system of claim 17, wherein the pickling apparatus is used to treat surfaces of materials selected from stainless steel, titanium, and titanium alloys.

20. The system of claim 16, 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.

21. The system of claim 16, wherein the first chamber further comprises a third inlet that communicates with a source of water vapor.

22. The system of claim 16, wherein the source of ozone is an ozone generator.

23. The system of claim 16, wherein the second inlet is located adjacent the first inlet.

24. The system of claim 16, wherein a diameter of the first chamber is at least 24 inches.

25. The system of claim 16, wherein the second chamber is a mist eliminator.

26. The system of claim 16, further comprising a scrubber.

27. The system of claim 16, wherein the inlet adapted for introducing treating material into contact with the acid pickling solution introduces the treating materials into the tank, bath, or spray device.

28. The system of claim 16, wherein the pickling apparatus further comprises a treating compartment in which the acid pickling solution is contacted with the treating material.

29. The system of claim 16, wherein the outlet of the second chamber fluidly communicates with the pickling apparatus so that solubilized nitric acid from the interior volume of the second chamber is conveyed to the pickling apparatus.