Removal of Hg, NO x , and SO x with using oxidants and staged gas/liquid contact

• US 8,242,324 B2
• Filed: 10/27/2009
• Issued: 08/14/2012
• Est. Priority Date: 10/01/2002
• Status: Expired due to Fees

• Current Assignee: Airborne International Holdings LLC
• Original Assignee: Airborne International Holdings LLC
• Inventors: Johnson, Dennis W.
• Primary Examiner(s): Johnson, Edward
• Application Number:
  US12/606,834
• Publication Number:
  US 20100068110A1
• Time in Patent Office: 1,022 Days
• Field of Search: 588/249, 588/403, 423/239.1, 423/243.01, 423/243.08, 423/244.01, 423/244.07, 423/244.08
• US Class Current: 588/403
• 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 Hg compounds from a gas stream, comprising:

a scrubbing operation, including;

contacting a gas stream containing Hg or Hg compounds and SO_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 or oxidant solution to oxidize and/or remove residual Hg or Hg compounds remaining in said stream.

2. The method as set forth in claim 1, wherein said gas stream includes NO_x compounds and a portion of the NO_x compounds and/or a portion of the Hg or Hg 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 stream is further contacted with a second sorbent selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium oxide, and 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 or oxidant solution.

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

5. The method as set forth in claim 2, wherein said partially cleaned gas stream containing NO_x compounds is further contacted with a second sorbent selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium oxide, and 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.

6. The method as set forth in claim 2, wherein contacting of said partially cleaned gas stream with an oxidant to remove residual Hg or Hg compounds remaining in said stream further removes at least a portion of NO_x in said gas or converts all or part of the NO to NO₂.

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

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

9. The method as set forth in claim 1, wherein said oxidant is selected from a group consisting of solutions of hydrogen peroxide, sodium chlorate, sodium chlorite, sodium hypochlorite, sodium perchlorite, chloric acid/sodium chlorate, chloric acid, potassium chlorate, potassium chlorite, potassium hypochlorite, potassium perchlorite, potassium permanganate, or a combination thereof or from a group of gaseous oxidants consisting of ozone, chlorine dioxide, or combination thereof.

10. The method as set forth in claim 2, wherein said oxidant is selected from a group consisting of solutions of hydrogen peroxide, sodium chlorate, sodium chlorite, sodium hypochlorite, sodium perchlorite, chloric acid/sodium chlorate, chloric acid, potassium chlorate, potassium chlorite, potassium hypochlorite, potassium perchlorite, potassium permanganate, or a combination thereof or from a group of gaseous oxidants consisting of ozone, chlorine dioxide, or combination thereof.

11. The method as set forth in claim 9, wherein said oxidant is in solution with an acid selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid.

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

13. The method as set forth in claim 12, wherein said alkali is selected from a group including:

caustic soda, sodium carbonate, or sodium bicarbonate.

14. The method as set forth in claim 9, wherein said oxidant includes chloride ions.

15. The method as set forth in claim 1, wherein said SO_x compounds include SO2 or SO3.

16. The method as set forth in claim 2, wherein said NO_x compounds include NO₂, N₂O₃, N₂O₅, N_xO_y and dimmers thereof.

17. The method as set forth in claim 1, further including the step of recirculating unreacted sorbent for use in said scrubbing operation.

18. The method as set forth in claim 2, further including the step of recirculating unreacted sorbent for use in said scrubbing operation.

19. 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.

20. The method as set forth in claim 2, wherein said gas is conditioned by injection of sorbent to reduce a portion of the inlet SO₃.

21. The method as set forth in claim 19, wherein at least some of said sulfur dioxide is removed and/or hydrochloric acid, NO_x or other acid gases are removed by the said injection.

22. The method as set forth in claim 2, including contacting said gas with a final wash.

23. The method as set forth in claim 2, wherein said SO_x compounds include SO₂ and SO₃.