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 . (canceled)
2 . A method of separating mercury from a mercury-containing gas, the method comprising:
combusting in a combustion chamber coal fed to the combustion chamber to provide the mercury-containing gas, wherein the combustion chamber comprises the coal and a halogen or halide promoter, a promoter precursor that transforms into the promoter, or a combination thereof, added to the coal, added to the combustion chamber, or a combination thereof,
adding a sorbent comprising a carbon sorbent material and/or a non-carbon sorbent material into the mercury-containing gas downstream of the combustion chamber;
contacting mercury in the mercury-containing gas with the sorbent; and
separating the sorbent from the mercury-containing gas;
wherein the halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof, added to the coal, added to the combustion chamber, or a combination thereof, is about 1 g to about 30 g per 100 g of the sorbent added to the mercury-containing gas.
3 . The method of claim 2 , comprising removing greater than 70 wt % of the mercury in the mercury-containing gas.
4 . The method of claim 2 , wherein the halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof, is added to the coal.
5 . The method of claim 2 , wherein the halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof, is added to the combustion chamber.
6 . The method of claim 2 , wherein the sorbent comprises the carbon sorbent material.
7 . The method of claim 6 , wherein the carbon sorbent material comprises activated carbon.
8 . The method of claim 7 , wherein the activated carbon comprises powdered activated carbon, granular activated carbon, or a combination thereof.
9 . The method of claim 2 , wherein the sorbent comprises the non-carbon sorbent material.
10 . The method of claim 9 , wherein the non-carbon material comprises 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, a bicarbonate compound, or a combination thereof.
11 . The method of claim 2 , wherein the sorbent comprises a combination of the carbon sorbent material and the non-carbon sorbent material.
12 . The method of claim 2 , wherein the halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof, is a halogen or halide compound.
13 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises Br − , Br 2 , HBr, or a combination thereof.
14 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises Br − and is a bromide compound.
15 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises HBr.
16 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises Cl − , Cl 2 , HCl, or a combination thereof.
17 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises Cl − and is a chloride compound.
18 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises I − , I 2 , HI, or a combination thereof.
19 . The method of claim 2 , wherein the halogen or halide promoter and/or the promoter precursor that transforms into the promoter comprises I − and is an iodide compound.
20 . The method of claim 2 , further comprising:
monitoring the mercury content of the mercury-containing gas after the separating of the sorbent therefrom; and
controlling, in response to the mercury content of the mercury-containing 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 halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof, or
a combination thereof,
so that the mercury content of the mercury-containing gas after the separating of the sorbent therefrom is maintained at or below a desired level.
21 . The method of claim 20 , comprising controlling, in response to the mercury content of the mercury-containing gas, the injection rate of injection the sorbent into the mercury-containing gas.
22 . The method of claim 20 , comprising controlling, in response to the mercury content of the mercury-containing gas, the rate of addition to the coal or the combustion chamber of the added halogen or halide promoter, the promoter precursor that transforms into the promoter, or a combination thereof.