A laboratory study of Hg oxidation catalyzed by SCR catalysts Karin Madsen on at CHEC Annual Day Anker Degn Jensen Joakim Reimer Thøgersen Flemming Frandsen

DTU Chemical Engineering Technical University of Denmark Outline •Background •Laboratory Study •Conclusions

DTU Chemical Engineering Technical University of Denmark Background •1930 tons of mercury was emitted in 2005 (Pacyna, 2010) –45% comes from combustion of fossil fuels •Existing air pollution control devices offers an economically feasible option for mercury control •Mercury species in flue gases from power plants –Hg 0 : Volatile, difficult to capture –Hg 2+ : Water soluble, can be captured in a wet scrubber –Hg p : Can be captured in particulate control devices •Mercury speciation is highly dependent on coal type/rank and operating conditions

DTU Chemical Engineering Technical University of Denmark Mercury oxidation and the SCR •Mercury is oxidized by halogens in the flue gas •(Potential) net reaction Hg HCl + 1/2 O 2 = HgCl 2 + H 2 O •SCR catalysts for NOx-control also have catalytic activity on the mercury oxidation –The combination SCR + wet FGD can offer >90% mercury capture

DTU Chemical Engineering Technical University of Denmark Laboratory Setup at Topsoe A/S

DTU Chemical Engineering Technical University of Denmark Mercury oxidation and Chlorine

DTU Chemical Engineering Technical University of Denmark Mercury Oxidation and Ammonia

DTU Chemical Engineering Technical University of Denmark Mercury Oxidation: Laboratory versus Pilot-scale data

DTU Chemical Engineering Technical University of Denmark Conclusion: Close Gap between Laboratory and Pilot- Scale Data •Difference in gas matrix –Laboratory Simulated flue gas containing Hg 0, O 2, H 2 O, NH 3, HCl and N 2 –Pilot Real flue gas from subbituminous coal combustion including NO, SO 2, and fly ash •Factor difference in catalyst activity must be due to difference in gas matrix •Future work involves testing of more complex gas matrices including NO and SO 2