Removal of Hg, NOx, and SOx with using oxidants and staged gas/liquid contact

• US 7,628,967 B2
• Filed: 03/17/2005
• Issued: 12/08/2009
• Est. Priority Date: 10/01/2002
• Status: Expired due to Fees

• Current Assignee: Airborne Industrial Minerals Inc.
• Original Assignee: Airborne Industrial Minerals Inc.
• Inventors: Johnson, Dennis W.
• Primary Examiner(s): Johnson; Edward M
• Application Number:
  US11/081,612
• Publication Number:
  US 20050214187A1
• Time in Patent Office: 1,727 Days
• Field of Search: 423/239.1, 423/243.01, 423/243.08, 423/244.01, 423/244.07, 423/244.08
• US Class Current: 423/239.1
• CPC Class Codes: B01D 2251/604 Hydroxides
• CPC Class Codes: B01D 2251/606 Carbonates
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 2257/602 Mercury or mercury compounds
• CPC Class Codes: B01D 53/1406 Multiple stage absorption
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: B01D 53/50 Sulfur oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/501 by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• CPC Class Codes: B01D 53/504 characterised by a specific device
• CPC Class Codes: B01D 53/507 by treating the gases with other liquids
• CPC Class Codes: B01D 53/508 by treating the gases with solids
• CPC Class Codes: B01D 53/56 Nitrogen oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/565 by treating the gases with solids
• CPC Class Codes: B01D 53/60 Simultaneously removing sulfur oxides and nitrogen oxides
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: B01D 53/75 Multi-step processes
• CPC Class Codes: B01D 53/77 Liquid phase processes
• CPC Class Codes: F23J 15/04 using washing fluids scrubbers for removing solids only F23J15/022
• CPC Class Codes: F23J 2215/20 Sulfur; Compounds thereof
• CPC Class Codes: F23J 2215/60 : Heavy metals; Compounds thereof
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A method of scrubbing mercury compounds and nitrogen oxides from a gas stream employing a scrubbing operation. The method involves the contact of the stream which contains mercury, SO_x and NO_x compounds with a sorbent to remove at least a portion of the latter compounds. This results in a partially cleaned stream. The method further involves contacting the latter stream with an oxidant to oxidize and remove substantially all residual nitrogen oxides, mercury and mercury compounds remaining in the stream.

Claims

1. A method of scrubbing NO_x compounds from a gas stream containing said NO_x compounds comprising a scrubbing operation, including:

contacting a gas stream containing SO_x and NO_x compounds with a sorbent for removing at least a portion of said SO_x compounds present in said stream to provide a partially cleaned gas stream; and

contacting said partially cleaned gas stream with an oxidant selected from the group consisting of;

hydrogen peroxide/nitric acid solution, hydrogen peroxide/nitric acid/hydrochloric acid solution, sodium chlorite solution, sodium chlorate solution, sodium hypochlorite solution, sodium perchlorite solution, chloric acid/sodium chlorate solution, oxone solution, potassium chlorate solution, potassium chlorite solution, potassium hypochlorite solution, potassium perchlorite solution, potassium permanganate solution, potassium permanganate/sodium hydroxide solution, chlorine dioxide gas or a combination thereof, to oxidize and/or remove residual NO_x remaining in said partially cleaned gas stream.

2. The method as set forth in claim 1, wherein at least some of the NO_x compounds present in the gas are removed in said scrubbing operation.

3. The method as set forth in claim 1, wherein said partially cleaned gas is further contacted with a second sorbent selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, magnesium oxide, magnesium hydroxide, buffering agents, additives, organic acids, or combinations thereof to remove substantially all remaining SO_x compounds prior to said contacting with an oxidant.

4. The method as set forth in claim 1, wherein substantially all of the residual NO_x Compounds are removed from said partially cleaned gas stream.

5. The method as set forth in claim 1, wherein oxidation of said partially cleaned gas stream with an oxidant to remove residual NO_x remaining in said stream further removes at least a portion of Hg or Hg compounds in said gas.

6. The method as set forth in claim 1, including contacting said gas containing NO₂ with water or an aqueous alkali to remove said NO₂.

7. The method as set forth in claim 1, including contacting said gas with a final wash.

8. The method as set forth in claim 1, wherein said oxidant is in solution with an acid selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid.

9. The method as set forth in claim 1, wherein said oxidant is in solution with an alkali.

10. The method as set forth in claim 9, wherein said alkali is selected from a group including:

caustic soda, sodium carbonate, or sodium bicarbonate.

11. The method as set forth in claim 1, wherein said oxidant includes chloride ions.

12. The method as set forth in claim 1, wherein said gas is conditioned by injection of sorbent to reduce a portion of the inlet SO₃.

13. The method as set forth in claim 1, wherein said gas is conditioned by injection of sorbent to reduce a portion of the inlet SO₂.

14. The method as set forth in claim 13, wherein a portion of said sulfur dioxide is removed and/or hydrochloric acid, NO_x or other acid gases are removed by the said injection.

15. The method as set forth in claim 1, wherein said oxidant is a sodium hypochlorite solution.

16. The method as set forth in claim 1, wherein said oxidant includes a sodium hypochlorite solution acidified with nitric acid.

17. The method as set forth in claim 16, wherein said sodium hypochlorite solution has a pH of 5.73.

18. The method as set forth in claim 1, wherein said oxidant includes a sodium hypochlorite solution acidified with hydrochloric acid.

19. The method as set forth in claim 18, wherein said sodium hypochlorite solution acidified with hydrochloric acid has a molar concentration of 0.1M NaClO and a pH of 3.74.

20. The method as set forth in claim 18, wherein said sodium hypochlorite solution acidified with hydrochloric acid has a pH of approximately 5.

21. The method as set forth in claim 1, wherein said oxidant includes a sodium hypochlorite solution acidified to have a pH of approximately 6.

22. The method as set forth in claim 1, wherein said oxidant is a potassium permanganate and sodium hydroxide solution.

23. The method as set forth in claim 1, wherein said oxidant includes a solution of 0.25 mol/l potassium permanganate and 2.5 mol/l sodium hydroxide.