Influence of the SCR(Selective Catalytic Reduction)-based NO_x Removal System on Mercury Morphology in Coal-fired Flue Gas

By adopting the standard Ontario method,measured and analyzed were the morphological distribution of mercury in flue gas before and after the selective catalytic reduction(SCR) denitrification system of a 300 MW unit.In combination with the chemical theory for SCR reactions to remove NOx,the influence of a SCR-based denitrification system on the mercury morphology of coal-fired flue gas was studied as a key problem.It has been found that the SCR catalyzer(V2O5-WO3(MoO3)/TiO2) plays a relatively small role of adsorbing the mercury in flue gas and has no influence on the total mercury concentration in flue gas.However,after a SCR,the mercury morphology in gas state underwent a relatively great change with the HgO concentration decreasing from 49.01% to 7.30% while the Hg2+ concentration increasing from 38.96% to 82.67%.The NH3 in the SCR-based denitrification system plays no role in transforming the mercury morphology.The oxidation of HgO by HCl was mainly completed through the Cl-Deacon reaction and the intermediate(HgO) under the catalytic action of the system and,eventually,HgCl2 was formed.