Injection of Sorbents in Ductwork Feeding Wet Scrubbers for Mercury Emission Control
Methods and systems are described for more effectively sequestering or removing mercury from flue gases. This is accomplished by feeding an adsorbent into the flow of flue gas in ductwork leading into a scrubber housing containing a wet scrubber composition and providing a residence time sufficient to enable the mercury to be sequestered by the adsorbent.
1 . A method for sequestering mercury and/or mercury-containing components from flue gases, which method comprises:
injecting an adsorbent into a stream of flue gases, thereby forming a dispersion of the adsorbent in the stream of flue gases, wherein the stream of flue gases is flowing directly into a wet scrubber composition, wherein said adsorbent comprises a bromine-containing powdered activated carbon;
providing a residence time for the dispersion of the adsorbent in the stream of flue gases prior to entry of the adsorbent into the wet scrubber composition (i) to enable contact between at least a portion of the adsorbent and the mercury and/or mercury-containing components of the stream of flue gases, and (ii) to provide for sequestration of at least a portion of said mercury and/or mercury-containing components by said adsorbent from said flue gases; and
allowing the dispersion of the adsorbent in the stream of flue gases to pass directly into the wet scrubber composition to minimize emission of mercury from the stream of flue gases,
wherein the flue gases are formed in a combustion chamber, and the method additionally comprises
introducing a bromine compound to the combustion chamber.
2 . A method as in claim 1 , wherein:
the injecting of the adsorbent is into a stream of flue gases in ductwork, which stream of flue gases is flowing directly to a scrubber housing comprising the wet scrubber composition,
the providing of the residence time for the dispersion of the adsorbent in the stream of flue gases is within said ductwork prior to entry of the adsorbent into the scrubber housing.
3 . A method as in claim 1 wherein the flue gases pass through a particulate collection device prior to said injecting of said adsorbent.
4 . A method as in claim 1 wherein the wet scrubber composition comprises a suspension, and the suspension comprises gypsum in an amount of about 20±5 wt. %.
5 . A method as in claim 1 wherein the bromine-containing powdered activated carbon has been formed from elemental bromine.
6 . A method as in claim 1 wherein the adsorbent has about 0.1 to about 20 wt. % bromine, based on the weight of the bromine-containing carbon adsorbent.