Study on mercury oxidation by SCR catalyst in coal-fired power plant

The mercury speciation and concentration in flue gas before and after selective catalytic reduction (SCR) system of a 300MW coal-fired utility boiler has been determined using Ontario Hydro method (OHM). The effect of SCR catalyst on mercury speciation transformation is investigated and the impact of chlorine content in coal and ammonia on mercury oxidation by SCR catalyst are examined. The results show that SCR has little effect on mercury emission reduction and the concentration of particulate mercury changes little before and after SCR. SCR catalyst promotes the oxidation of elemental mercury to oxidized mercury and has significant impact on mercury emission. The oxidation of elemental mercury by SCR catalyst is greatly affected by chlorine content in coal and the higher the chlorine content in coal, the higher the concentration of oxidized mercury at SCR outlet. NH3 is detrimental to oxidation of elemental mercury by SCR catalyst.