Sorbents for the oxidation and removal of mercury

• US 8,512,655 B2
• Filed: 03/22/2012
• Issued: 08/20/2013
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Midwest Energy Emissions Corp.
• Original Assignee: Energy & Environmental Research Center (GE Aerospace)
• Inventors: Olson, Edwin S., Holmes, Michael J., Pavlish, John Henry
• Primary Examiner(s): ORLANDO, AMBER ROSE
• Application Number:
  US13/427,665
• Publication Number:
  US 20120183458A1
• Time in Patent Office: 516 Days
• Field of Search: 110/345, 951/34, 951/42, 951/37, 423/210
• US Class Current: 423/210
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/25 Coated, impregnated or composite adsorbents
• CPC Class Codes: B01D 2257/602 Mercury or mercury compounds
• CPC Class Codes: B01D 2258/0283 Flue gases
• CPC Class Codes: B01D 53/10 with dispersed adsorbents
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: B01J 20/02 comprising inorganic material
• CPC Class Codes: B01J 20/0262 Compounds of O, S, Se, Te
• CPC Class Codes: B01J 20/027 Compounds of F, Cl, Br, I
• CPC Class Codes: B01J 20/04 comprising compounds of alkali metals, alkaline earth metals or magnesium
• CPC Class Codes: B01J 20/041 Oxides or hydroxides
• CPC Class Codes: B01J 20/043 Carbonates or bicarbonates, e.g. limestone, dolomite, aragonite
• CPC Class Codes: B01J 20/10 comprising silica or silicate
• CPC Class Codes: B01J 20/106 Perlite
• CPC Class Codes: B01J 20/12 Naturally occurring clays or bleaching earth
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: B01J 20/22 comprising organic material
• CPC Class Codes: B01J 20/223 containing metals, e.g. organo-metallic compounds, coordination complexes
• CPC Class Codes: B01J 20/28004 Sorbent size or size distribution, e.g. particle size
• CPC Class Codes: B01J 20/28016 Particle form
• CPC Class Codes: B01J 20/3416 : of sorbents or filter aids comprising free carbon, e.g. activated carbon
• CPC Class Codes: B01J 2220/42 : Materials comprising a mixture of inorganic materials materials coated or impregnated on a carrier B01J20/32
• CPC Class Codes: Y10S 95/901 : Activated carbon

Abstract

A promoted activated carbon sorbent is described that is highly effective for the removal of mercury from flue gas streams. The sorbent comprises a new modified carbon form containing reactive forms of halogen and halides. Optional components may be added to increase reactivity and mercury capacity. These may be added directly with the sorbent, or to the flue gas to enhance sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The sorbent can be regenerated and reused. Sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active sorbent into the mercury contaminated gas stream are described.

Claims

1. A method for separating mercury from a mercury-containing gas stream, the method comprising:

contacting a particulate carbon including at least some graphene and a promoter selected from the group consisting of an elemental halogen, a group V halide, a group VI halide, a hydrohalide, and combinations thereof, to form a promoted sorbent particulate, modifying at least some edge structures of at least some of the graphene of the particulate carbon with the promoter to form carbocations, wherein some of the modified edge structures of the graphene accept electrons from neutral mercury atoms;

contacting the promoted sorbent particulate with a mercury stabilizing agent to form a bifunctional sorbent particulate;

contacting the mercury-containing gas stream and the bifunctional sorbent particulate to form a stabilized mercury/bifunctional sorbent particulate; and

separating at least a portion of the stabilized mercury/bifunctional sorbent particulate from the gas stream.

2. The method of claim 1 wherein the particulate carbon and the promoter are contacted prior to contacting with the gas stream.

3. The method of claim 2 wherein the promoted sorbent particulate and the gas stream are contacted prior to contacting with the mercury stabilizing agent.

4. The method of claim 2 wherein the promoted sorbent particulate and the mercury stabilizing agent are contacted prior to contacting with the gas stream.

5. The method of claim 1 wherein the particulate carbon and the promoter and the mercury stabilizing agent are all mutually contacted within the gas stream.

6. The method of claim 1 wherein the promoter is an elemental halogen or a hydrohalide.

7. The method of claim 6 wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide.

8. The method of claim 1 wherein the promoter is a group V halide or a group VI halide.

9. The method of claim 8 wherein the promoter is SCl₂ or PBr₃.

10. The method of claim 1 wherein the mercury stabilizing agent comprises S, Se, H₂S, SO₂, H₂Se, SeO₂, CS₂, P₂S₅, or combinations thereof.

11. The method of claim 10 wherein a mercury capacity per unit weight of the bifunctional sorbent particulate is increased relative to a mercury capacity per unit weight of a comparable sorbent particulate which has not been contacted with the mercury stabilizing agent.

12. The method of claim 1, further comprising contacting the bifunctional sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

13. The method of claim 12 wherein the alkaline material comprises an alkali or alkaline earth element in metallic or salt form.

14. The method of claim 12 wherein the mercury-containing gas stream is contacted with the alkaline material prior to contacting the mercury-containing gas stream with the bifunctional sorbent particulate.

15. The method of claim 1 further comprising reacting the particulate carbon with a secondary component to enhance reactivity and capacity of the bifunctional sorbent particulate with respect to mercury vapor, wherein the reacting of the particulate carbon with the secondary component takes place before, during, or after contacting the particulate carbon and the promoter.

16. The method of claim 15 wherein the secondary component is selected from the group consisting of iodine, HI, a group V iodine, and a group VI iodide, and any combination thereof.

17. The method according to claim 1, wherein the promoter is in gaseous form.

18. The method according to claim 1, wherein the promoter is in an organic solvent.

19. The method of claim 18, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or supercritical carbon dioxide.

20. The method of claim 1, wherein the mercury-containing gas stream is a product of coal or petroleum combustion.

21. A method for separating mercury, having at least some neutral mercury atoms, contained in a gas stream, comprising:

contacting activated carbon including at least some graphene and a promoter selected from the group consisting of an elemental halogen, a group V halide, a group VI halide, a hydrohalide, and combinations thereof, to form a promoted sorbent particulate by modifying at least some edge structures of the graphene to form carbocations, such that the modified edge structures accept electrons from the neutral mercury atoms of the mercury;

contacting the mercury-containing gas stream and the promoted sorbent particulate to form a stabilized mercury-sorbent particulate; and

separating at least some of the stabilized mercury-sorbent particulate from the gas stream.

22. The method of claim 21, wherein the promoter is an elemental halogen or a hydrohalide, or a combination.

23. The method of claim 22 wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

24. The method of claim 21, wherein the promoter is a group V halide or a group VI halide.

25. The method of claim 24 wherein the promoter is PBr₃ or SCl₂.

26. The method of claim 21 further comprising contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

27. The method according to claim 21, wherein the promoter is in gaseous form.

28. The method according to claim 21, wherein the promoter is in an organic solvent.

29. The method of claim 28, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or supercritical carbon dioxide.

30. The method of claim 21, wherein the mercury-containing gas stream is a product of coal or petroleum combustion.

31. A method for removing mercury from a mercury-containing gas stream, comprising:

contacting activated carbon including at least some graphene and a promoter selected from the group consisting of an elemental halogen, a group V halide, a group VI halide, a hydrohalide, and combinations thereof, to form a promoted sorbent particulate, modifying at least some of the edge structures of some of the graphene, for forming carbocations such that the promoted sorbent particulate accepts electrons from neutral mercury atoms of the mercury;

contacting the mercury-containing gas stream and the promoted sorbent particulate for forming a stabilized mercury-sorbent particulate; and

separating at least a portion of the stabilized mercury-sorbent particulate from the gas stream.

32. The method of claim 31, wherein the promoter is an elemental halogen or a hydrohalide, or a combination.

33. The method of claim 32 wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

34. The method of claim 31, wherein the promoter is a group V halide or a group VI halide.

35. The method of claim 34 wherein the promoter is PBr₃ or SCl₂.

36. The method of claim 31 further comprising contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

37. The method according to claim 31, wherein the promoter is in gaseous form.

38. The method according to claim 31, wherein the promoter is in an organic solvent.

39. The method of claim 38, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or supercritical carbon dioxide.

40. The method of claim 31, wherein the mercury-containing gas stream is a product of coal or petroleum combustion.

41. A method for separating mercury in a gas stream comprising:

contacting carbon including at least some graphene and a promoter selected from the group consisting of an elemental halogen, a group V halide, a group VI halide, a hydrohalide, and combinations thereof, to form a promoted sorbent particulate;

modifying at least some of the edge structures of at least some of the graphene of the carbon for forming carbocations for the promoted sorbent for accepting at least some electrons from mercury atoms of the mercury;

contacting the mercury-containing gas stream and the promoted sorbent particulate for forming a stabilized mercury-sorbent particulate; and

separating at least some of the stabilized mercury-sorbent particulate from the gas stream.

42. The method of claim 41, wherein the promoter is an elemental halogen or a hydrohalide, or a combination.

43. The method of claim 42 wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

44. The method of claim 41, wherein the promoter is a group V halide or a group VI halide.

45. The method of claim 44 wherein the promoter is PBr₃ or SCl₂.

46. The method of claim 41 further comprising contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

47. The method according to claim 41, wherein the promoter is in gaseous form.

48. The method according to claim 41, wherein the promoter is in an organic solvent.

49. The method of claim 48, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or supercritical carbon dioxide.

50. The method of claim 41, wherein the mercury-containing gas stream is a product of coal or petroleum combustion.

51. A method for separating mercury in a gas stream comprising:

contacting carbon including at least some graphene and a promoter including at least one of bromine, bromine compounds, and combinations thereof to form a promoted sorbent particulate;

modifying at least some of the edge structures of the graphene for forming carbocations for accepting some electrons from mercury atoms of the mercury;

contacting the mercury-containing gas stream and the a promoted sorbent particulate for forming a stabilized mercury-sorbent particulate; and

,

separating at least some of the stabilized mercury-sorbent particulate from the gas stream.

52. The method of claim 51, wherein the promoter is an elemental halogen or a hydrohalide, or a combination.

53. The method of claim 52 wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

54. The method of claim 51, wherein the promoter is a group V halide or a group VI halide.

55. The method of claim 54 wherein the promoter is PBr₃ or SBr₂.

56. The method of claim 51 further comprising contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

57. The method according to claim 51, wherein the promoter is in gaseous form.

58. The method according to claim 51, wherein the promoter is in an organic solvent.

59. The method of claim 58, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or supercritical carbon dioxide.

60. The method of claim 51, wherein the mercury-containing gas stream is a product of coal or petroleum combustion.