Sorbents for the oxidation and removal of mercury

• US 9,757,689 B2
• Filed: 06/27/2014
• Issued: 09/12/2017
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Midwest Energy Emissions Corp.
• Original Assignee: Midwest Energy Emissions Corp.
• Inventors: Olson, Edwin S., Holmes, Michael J., Pavlish, John Henry
• Primary Examiner(s): ORLANDO, AMBER ROSE
• Application Number:
  US14/318,270
• Publication Number:
  US 20140308188A1
• Time in Patent Office: 1,173 Days
• 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 halocarbon sorbent formed by an addition reaction between a base activated carbon and a promoter selected from the group consisting of Cl₂, Br₂, HCl, HBr, PBr₃, and combinations thereof, wherein

the halocarbon sorbent has a mean particle size greater than 60 microns, and

the halocarbon sorbent exposed to a gas stream comprising elemental mercury at a temperature of about 250°

C. has a 50% breakthrough time of the elemental mercury that is greater than or equal to about 2500% of the breakthrough time of the elemental mercury of a corresponding halocarbon sorbent that is free of the promoter and tested under the same conditions.

2. The halocarbon sorbent according to claim 1 wherein the promoter is selected from the group consisting of Br₂, HBr, and combinations thereof.

3. The halocarbon sorbent according to claim 1 wherein the base activated carbon is selected from the group consisting of powdered activated carbon, granular activated carbon, carbon black, carbon fiber, aerogel carbon, pyrolysis char, activated carbon with an average particle size greater than 60 micrometers, and combinations thereof.

4. The halocarbon sorbent according to claim 1 further comprising an alkaline component selected from the group consisting of alkali elements, alkaline earth elements, alkali salts, alkaline earth salts, and combinations thereof.

5. The halocarbon sorbent according to claim 1 further comprising a mercury-stabilizing reagent selected from the group consisting of S, Se, H₂S, SO₂, H₂Se, SeO₂, CS₂, P₂S₅, and combinations thereof.

6. The halocarbon sorbent according to claim 5 further comprising an alkaline or alkaline earth element.

7. The halocarbon sorbent of claim 2 further comprising a component that is selected from the group consisting of halogens, hydrogen halides, Group V halides, Group VI halides, and combinations thereof.

8. The halocarbon sorbent according to claim 7 wherein the concentration of the component in the halocarbon sorbent is present in about 1 wt-% to about 15 wt-% of the concentration of the promoter incorporated into the sorbent.

9. The halocarbon sorbent according to claim 8 wherein the component is selected from the group consisting of halogens, HI, HBr, HCl, and combinations thereof.

10. The halocarbon sorbent according to claim 9 wherein the component is selected from the group consisting of I₂, HI, and combinations thereof.

11. The halocarbon sorbent according to claim 1 wherein the promoter is substantially in vapor form in its addition reaction with the base activated carbon.

12. The halocarbon sorbent according to claim 11 wherein the promoter is combined with an organic solvent prior to reaction with the base activated carbon.

13. The halocarbon sorbent of claim 11 wherein the promoter and the component are combined with the base activated carbon substantially simultaneously.

14. The halocarbon sorbent according to claim 1 wherein the promoter is Br₂ and the sorbent comprises a component that is HI.

15. 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 that is the halocarbon sorbent of claim 1, comprising forming carbocations using the promoter on at least some edge structures of at least some of the graphene; and

contacting at least some of the mercury in the stream and the promoted sorbent particulate to form a stabilized mercury-promoted sorbent particulate, wherein the carbocations on the edge structures of the graphene accept at least some electrons from mercury atoms of the mercury.

16. The method of claim 15, wherein the promoter is an elemental halogen or a hydrohalide, or a combination thereof.

17. The method of claim 16, wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

18. The method of claim 15, wherein the promoter is PBr₃ or SCl₂ .

19. The method of claim 15, further comprising:

contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

20. The method of claim 15, wherein the promoter is in one of gaseous form or an organic solvent.

21. The method of claim 20, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or a supercritical carbon dioxide.

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

contacting carbon including at least some graphene having at least some edges thereon and a promoter including at least one of bromine, bromine compounds, and combinations thereof to form a promoted sorbent particulate that is the halocarbon sorbent of claim 1 by modifying at least some edges of at least some of the graphene; and

contacting at least some of the mercury in the stream and the promoted sorbent particulate to form a stabilized mercury-promoted sorbent particulate, wherein the modified edges of the graphene form carbocations that accept at least some electrons from mercury atoms of the mercury.

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

24. The method of claim 23, wherein the promoter is PBr₃ or SBr₂.

25. The method of claim 22, further comprising:

contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

26. The method of claim 22, wherein the promoter is in one of gaseous form or an organic solvent.

27. The method of claim 26, wherein the organic solvent is a hydrocarbon, a chlorinated hydrocarbon, or a supercritical carbon dioxide.

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

contacting carbon including at least some graphene having at least some edges 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 that is the halocarbon sorbent of claim 1 having at least some modified some edge structures of at least some of the graphene; and

contacting at least some of the mercury in the stream and the promoted sorbent particulate to form a stabilized mercury-promoted sorbent particulate, wherein the modified edge structures of the graphene form carbocations that accept at least some electrons from mercury atoms of the mercury.

29. The method of claim 28, wherein the promoter is an elemental halogen or a hydrohalide, or a combination thereof.

30. The method of claim 29, wherein the elemental halogen is bromine, or wherein the hydrohalide is hydrogen bromide, or both.

31. The method of claim 28, further comprising:

contacting the promoted sorbent particulate, the mercury-containing gas stream, or both, with an alkaline material.

32. The method of claim 28, wherein the promoter is in one of gaseous form or an organic solvent.

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