Sorbents for the oxidation and removal of mercury
A promoted carbon and/or non-carbon base sorbent are described that are highly effective for the removal of mercury from flue gas streams. The promoted sorbent comprises a carbon and/or non-carbon base sorbent that has reacted with and contains forms of halogen and halides. Optional components may be added to increase and/or preserve reactivity and mercury capacity. These may be added directly with the base sorbent, or in-flight within a gas stream (air, flue gas, etc.), to enhance base sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The promoted sorbent can be regenerated and reused. Base sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active base sorbent into the mercury contaminated gas stream are described.
1. A method of separating mercury from a mercury-containing gas, the method comprising:
combusting coal in a combustion chamber, to provide the mercury-containing gas, wherein the mercury-containing gas comprises a halogen or halide promoter comprising HBr, Br − , or a combination thereof, wherein
the coal comprises added Br 2 , HBr, Br − , or a combination thereof, added to the coal upstream of the combustion chamber, or
the combustion chamber comprises added Br 2 , HBr, Br − , or a combination thereof, or
a combination thereof;
injecting a sorbent material comprising activated carbon into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent, to form a mercury/sorbent composition;
separating the mercury/sorbent composition from the mercury-containing gas, to form a cleaned gas;
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 a desired level.
2. The method of claim 1 , comprising removing greater than 70 wt % of the mercury in the mercury-containing gas.
3. The method of claim 1 , comprising removing greater than 70 wt % of the mercury in the mercury-containing gas on the sorbent.
4. The method of claim 1 , wherein the sorbent in the mercury-containing gas comprises about 1 g to about 30 g of the halogen or halide promoter per 100 g of the sorbent material.
5. The method of claim 1 , wherein the combustion chamber comprises the halogen or halide promoter.
6. The method of claim 1 , wherein the coal comprises added Br 2 , HBr, Br − , or a combination thereof, added to the coal upstream of the combustion chamber.
7. The method of claim 1 , wherein the promoter is contacted with the sorbent in vapor form, gaseous form, liquid form, or in an organic solvent.
8. The method of claim 1 , further comprising injecting a secondary material into the mercury-containing gas downstream of the combustion chamber.
9. The method of claim 8 , wherein the secondary material comprises a halogen, a compound derived from a halogen, a hydrohalide, a compound comprising a Group V or Group VI element and a molecular halogen, or a combination thereof.
10. The method of claim 1 , wherein the sorbent material injected into the mercury-containing gas further comprises a non-carbon sorbent material.
11. The method of claim 10 , wherein the non-carbon sorbent material comprises at least one of a porous felsic material, a vesicular felsic material, a porous basaltic material, a vesicular basaltic material, a clay-based compound, an alkaline compound, a calcium hydroxide compound, a sodium acetate compound, and a bicarbonate compound.
12. The method of claim 1 , wherein the activated carbon comprises powdered activated carbon, granular activated carbon, or a combination thereof.
13. The method of claim 1 , wherein the sorbent material injected into the mercury-containing gas is substantially free of halogen and halide promotion.
14. The method of claim 1 , wherein the sorbent material injected into the mercury-containing gas is a promoted sorbent obtained by contacting a base sorbent with another halogen or halide promoter.
15. The method of claim 1 , wherein the combustion chamber comprises a boiler.
16. The method of claim 1 , wherein the mercury-containing gas is a flue gas.
17. The method of claim 1 , wherein the injection of the sorbent material into the mercury-containing gas occurs upstream of an air pre-heater.
18. The method of claim 1 , wherein the injection of the sorbent material into the mercury-containing gas occurs upstream of a particulate separator or a scrubber.
19. The method of claim 1 , wherein the coal comprises added halide sorbent enhancement additive.
20. The method of claim 1 , wherein the combustion chamber comprises added Br 2 , HBr, Br − , or a combination thereof.
21. The method of claim 1 , wherein the coal comprises added sorbent enhancement additive that comprises Br − .
22. The method of claim 21 , wherein the sorbent enhancement additive comprises a bromide compound.
23. A method of separating mercury from a mercury-containing gas, the method comprising:
combusting coal in a combustion chamber, to provide the mercury-containing gas, wherein the mercury-containing gas comprises a halogen or halide promoter comprising HBr, Br − , or a combination thereof, wherein
the coal comprises added Br 2 , HBr, Br − , or a combination thereof, added to the coal upstream of the combustion chamber, or
the combustion chamber comprises added Br 2 , HBr, Br − , or a combination thereof, or
a combination thereof;
injecting a sorbent material comprising activated carbon into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent, to form a mercury/sorbent composition; and
separating the mercury/sorbent composition from the mercury-containing gas, to form a cleaned gas.
24. A method of separating mercury from a mercury-containing gas, the method comprising:
combusting coal in a combustion chamber, to provide the mercury-containing gas, wherein the mercury-containing gas comprises a halogen or halide promoter comprising HBr, Br − , or a combination thereof, wherein
the coal comprises added Br 2 , HBr, Br − , or a combination thereof, added to the coal upstream of the combustion chamber, or
the combustion chamber comprises added Br 2 , HBr, Br − , or a combination thereof, or
a combination thereof;
injecting a sorbent material comprising activated carbon into the mercury-containing gas downstream of the combustion chamber such that the activated carbon reacts with the halogen or halide promoter in the mercury-containing gas to form a promoted sorbent;
contacting mercury in the mercury-containing gas with the promoted sorbent, to form a mercury/sorbent composition;
separating the mercury/sorbent composition from the mercury-containing gas, to form a cleaned gas;
monitoring the mercury content of the cleaned gas; and
controlling, in response to the mercury content of the cleaned gas,
an injection rate of injecting the sorbent into the mercury-containing gas,
a rate of addition to the coal or the combustion chamber of the added Br 2 , HBr, the bromide compound, or a combination thereof, or
a combination thereof,
so that the mercury content of the cleaned gas is maintained at or below a desired level.
25. A method of separating mercury from a mercury-containing gas, the method comprising:
combusting coal in a combustion chamber, to provide the mercury-containing gas, wherein
the coal comprises added Br 2 , HBr, a bromide compound, or a combination thereof, added to the coal upstream of the combustion chamber, or
the combustion chamber comprises added Br 2 , HBr, a bromide compound, or a combination thereof, or
a combination thereof,
injecting a sorbent material comprising activated carbon into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent, to form a mercury/sorbent composition; and
separating the mercury/sorbent composition from the mercury-containing gas, to form a cleaned gas.
26. The method of claim 25 , wherein the coal comprises the added Br 2 , HBr, the bromide compound, or a combination thereof, added to the coal upstream of the combustion chamber.
27. The method of claim 25 , wherein the combustion chamber comprises the added Br 2 , HBr, the bromide compound, or a combination thereof.
28. The method of claim 25 , further comprising
monitoring the mercury content of the cleaned gas; and
controlling, in response to the mercury content of the cleaned gas,
an injection rate of injecting the sorbent into the mercury-containing gas,
a rate of addition to the coal or the combustion chamber of the added Br 2 , HBr, the bromide compound, or a combination thereof, or
a combination thereof,
so that the mercury content of the cleaned gas is maintained at or below a desired level.
29. The method of claim 25 , wherein the mercury-containing gas comprises about 1 g to about 30 g of the element bromine per 100 g of the sorbent.
30. The method of claim 25 , wherein the mercury/sorbent composition comprises the element bromine, the sorbent material, and mercury.