SORBENTS FOR THE OXIDATION AND REMOVAL OF MERCURY

• US 20180257030A1
• Filed: 05/08/2018
• Published: 09/13/2018
• 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 H.
• Granted Patent: US 10,668,430 B2
• Time in Patent Office: 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 method for separating mercury from a mercury-containing gas, the method comprising:

combusting a mixture of coal and an additive that has been added to the coal, the additive comprising a bromide compound, to form the mercury-containing gas;

adding a particulate sorbent material comprising activated carbon into the mercury-containing gas;

promoting at least a portion of the sorbent material by chemically reacting the sorbent material with Br₂, HBr, Br⁻

, or a combination thereof, in-flight, to form a promoted sorbent material;

chemically reacting mercury in the mercury-containing gas with the promoted sorbent material, to form a mercury-sorbent; and

separating the mercury-sorbent from the mercury-containing gas.

2. The method of claim 1, further comprising mixing the additive and the coal before combusting the coal.

3. The method of claim 2, wherein the additive mixed with the coal is in a liquid.

4. The method of claim 3, wherein the liquid is a hydrocarbon, a chlorinated hydrocarbon, supercritical carbon dioxide, water, salt solution, or a combination thereof.

5. The method of claim 1, wherein the promoted sorbent material comprises active sites, wherein the active sites comprise halide anions bound to the activated carbon.

6. The method of claim 1, wherein the promoted sorbent material comprises active sites, wherein the active sites comprise carbocations bound to halide anions.

7. The method of claim 1, wherein chemically reacting the sorbent material with the additive in the mercury-containing gas comprises chemically reacting carbene species edge sites in the activated carbon with the additive.

8. The method of claim 1, wherein carbocations in the activated carbon of the mercury-sorbent accept electrons from mercury atoms of the mercury-sorbent.

9. The method of claim 1, wherein the additive is substantially in vapor form in the mercury-containing gas.

10. The method of claim 1, wherein the additive comprises Ca, Na, or a combination thereof.

14. The method of claim 1, wherein the activated carbon is chosen from powdered activated carbon, granular activated carbon, carbon black, carbon fiber, aerogel carbon, pyrolysis char, and combinations thereof.

21. The method of claim 1, wherein the coal and the additive are mixed at a location upstream of a combustion furnace where combustion occurs.

22. The method of claim 1, comprising separating greater than 70 wt % of the mercury from the mercury-containing gas.

23. The method of claim 1, comprising separating greater than 70 wt % of the mercury from the mercury-containing gas on the sorbent.

24. The method of claim 1, wherein the sorbent material has a composition comprising from about 1 to about 30 grams of additive per 100 grams of activated carbon.

25. The method of claim 1, wherein the method is a method for reducing mercury in the mercury-containing gas to a desired level, wherein separating the mercury-sorbent from the mercury-containing gas forms a cleaned gas, the method further comprising:

monitoring the mercury content of the cleaned gas; and

controlling, in response to the monitored mercury content of the cleaned gas, an injection rate of injecting the sorbent into the mercury-containing gas, the sorbent composition, or a combination thereof, so that the mercury content of the cleaned gas is maintained at or below the desired level.

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