Sorbents for the oxidation and removal of mercury
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.
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 coal comprises an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof, wherein the additive is added to the coal before the coal enters the combustion chamber, or
the combustion chamber comprises an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof or
a combination thereof;
injecting a sorbent comprising activated carbon into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent; and
separating the sorbent contacted with the mercury from the mercury-containing gas.
2. The method of claim 1 , wherein the coal comprises the additive comprising the Br 2 , HBr, the bromide compound, or a combination thereof, wherein the additive is added to the coal before the coal enters the combustion chamber.
3. The method of claim 1 , wherein the combustion chamber comprises the additive comprising the Br 2 , HBr, the bromide compound, or a combination thereof.
4. The method of claim 1 , wherein the coal is combusted in the combustion chamber at a coal-combustion facility, wherein the additive comprising the Br 2 , HBr, bromide compound, or combination thereof, is added to the coal before the coal enters the combustion chamber, wherein the addition of the additive comprising the Br 2 , HBr, bromide compound, or combination thereof, to the coal is performed at the coal-combustion facility.
5. The method of claim 1 , wherein the coal is combusted in the combustion chamber at a coal-combustion facility, wherein the additive comprising the Br 2 , HBr, bromide compound, or combination thereof, is added to the coal before the coal enters the combustion chamber, wherein the addition of the additive comprising the Br 2 , HBr, bromide compound, or combination thereof, to the coal is performed at a site other than the coal-combustion facility.
6. The method of claim 1 , wherein the combustion chamber is an electric utility coal combustion chamber.
7. The method of claim 1 , wherein the combustion chamber is a coal combustion furnace.
8. The method of claim 1 , wherein the coal comprises a subbituminous coal.
9. The method of claim 1 , wherein the coal comprises a lignite coal.
10. The method of claim 1 , further comprising
measuring the mercury content of the mercury-containing gas; and
modifying, in response to the measured mercury content of the mercury-containing gas,
an injection rate of injecting the sorbent into the mercury-containing gas,
an amount of the Br 2 , HBr, the bromide compound, or a combination thereof, added to the coal or the combustion chamber, or
a combination thereof.
11. The method of claim 10 , wherein the measuring of the mercury content comprises continuous measurement.
12. The method of claim 1 , further comprising:
modifying, in response to a measured mercury content,
an injection rate of injecting the sorbent into the mercury-containing gas,
an amount of the Br 2 , HBr, the bromide compound, or a combination thereof, added to the coal or the combustion chamber, or
a combination thereof.
13. The method of claim 1 , wherein the mercury-containing gas comprises about 1 g to about 30 g of the element bromine per 100 g of the sorbent.
14. The method of claim 1 , wherein the sorbent contacted with the mercury comprises the element bromine and mercury.
15. The method of claim 1 , comprising removing greater than 70 wt % of the mercury in the mercury-containing gas.
16. The method of claim 1 , comprising removing greater than 70 wt % of the mercury in the mercury-containing gas with the sorbent.
17. The method of claim 1 , wherein the sorbent in the mercury-containing gas comprises about 1 g to about 30 g of the added Br 2 , HBr, the bromide compound, or a combination thereof, per 100 g of the sorbent.
18. The method of claim 1 , wherein the Br 2 , HBr, or the bromide compound is contacted with the sorbent in vapor form, gaseous form, liquid form, or in an organic solvent.
19. The method of claim 1 , wherein the activated carbon comprises powdered activated carbon, granular activated carbon, or a combination thereof.
20. The method of claim 1 , wherein the sorbent injected into the mercury-containing gas is a sorbent obtained by contacting a sorbent with a halogen or halide promoter prior to the injection of the sorbent into the mercury-containing gas.
21. The method of claim 1 , wherein the sorbent injected into the mercury-containing gas is free of contact with a halogen or halide promoter prior to injection of the sorbent into the mercury-containing gas.
22. The method of claim 1 , wherein the combustion chamber comprises a boiler.
23. The method of claim 1 , wherein the mercury-containing gas is a flue gas.
24. The method of claim 1 , wherein the injection of the sorbent into the mercury-containing gas occurs upstream of a particulate separator, a scrubber, or a combination thereof.
25. The method of claim 24 , wherein the particulate separator comprises a baghouse, an electrostatic precipitator, a fabric filter, or a combination thereof.
26. The method of claim 1 , wherein a halide sorbent enhancement additive comprises the added Br 2 , HBr, bromide compound, or combination thereof.
27. The method of claim 26 , wherein the sorbent enhancement additive comprises the bromide compound.
28. A method of separating mercury from a mercury-containing as, 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 an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof, wherein the additive is added to the coal before the coal enters the combustion chamber, or
the combustion chamber comprises an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof, or
a combination thereof,
injecting a sorbent comprising activated carbon into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent; and
separating the sorbent contacted with the mercury from the mercury-containing gas.
29. 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 an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof, wherein the additive is added to the coal before the coal enters the combustion chamber, or
the combustion chamber comprises an additive comprising Br 2 , HBr, a bromide compound, or a combination thereof, or
a combination thereof;
injecting a sorbent 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;
separating the promoted sorbent contacted with the mercury from the mercury-containing gas;
measuring the mercury content of the mercury-containing gas; and
modifying, in response to the measured mercury content,
an injection rate of injecting the sorbent into the mercury-containing gas,
an amount of the Br 2 , HBr, the bromide compound, or a combination thereof, added to the coal or the combustion chamber, or
a combination thereof.