Simulation and evaluation of elemental mercury concentration increase in flue gas across a wet scrubber.
Experimental data from a laboratory-scale wet scrubber simulator confirmed that oxidized mercury, Hg2+, can be reduced by aqueous S(IV) (sulfite and/or bisulfite) species and results in elemental mercury (HgO) emissions under typical wet FGD scrubber conditions. The S(IV)-induced Hg2+ reduction and Hg0 emission mechanism can be described by a model which assumes that only a fraction of the Hg2+ can be reduced, and the rate-controlling step of the overall process is a first-order reaction involving the Hg-S(IV) complexes. Experimental data and model simulations predict that the Hg2+ in the flue gas can cause rapid increase of Hg0 concentration in the flue gas across a FGD scrubber. Forced oxidation can enhance Hg2+ reduction and Hg0 emission by decreasing the S(IV) concentration in the scrubbing liquor. The model predictions also indicate that flue gas Hg0 increase across a wet FGD scrubber can be reduced by decreasing the pH, increasing S(IV) concentration, and lowering the temperature.
Chang
John C S
JC
Air Pollution and Prevention Control Division, E305-03, National Risk Management Research Laboratory, Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. Chang.John@epa.gov
Ghorishi
S Behrooz
SB
D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000517:prevention & control*; D002119:Calcium Carbonate / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008628:Mercury / Q000032:analysis*; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D013696:Temperature
D000393:Air Pollutants; D017610:Calcium Compounds; D010087:Oxides; C016538:lime; D008628:Mercury; D002119:Calcium Carbonate