Experimental And Mechanism Study Of Mercury Oxidation In Coal-fired Flue Gas By Cerium-based SCR Catalysts

Coal-fired power plants are an important source of anthropogenic mercury emissionsin the atmosphere. Mercury to oxidized mercury (Hg2+), particulate mercury (Hgp) andelemental mercury (Hg0) exists in three forms in which the flue gas. Oxidized mercury,which is soluble in water,the wet desulfurization device is easy to remove; particulatemercury can be removed dust removal device; hardest to deal with is elemental mercury,because it does not dissolve in water and volatile, so it is easy to emissions of atmosphericpollution. SCR catalyst can catalyze the oxidation of elemental mercury, but the SCRcatalyst into industrial applications, there are some problems, such as a narrow temperaturewindow, low specific surface area, such as sulfur resistance is poor, requiring thedevelopment of new SCR catalyst, can be more efficient achieve synergy nitrogen oxidesand mercury removal.This paper introduces oxygen storage ability of CeO2and large specific surface areaSiO2, using the soil-gel synthesis of a new CeO2/TiO2-SiO2(CTS) catalyst and bench in afixed bed experiments, the catalyst was studied in a simulated flue gas catalytic oxidationof elemental mercury conditions. The results show that under simulated flue gas conditions,CTS catalyst for elemental mercury oxidation efficiency can reach about100%, in therange of150-250℃have reached a very high oxidation efficiency. CTS NO oxidationcatalyst can promote mercury, while SO2is inhibited. CTS mercury oxidation catalystfollowed Eley-Rideal mechanism.Synthesized using the soil-gel method CeO2-WO3(CW)catalyst in a fixed bedexperiment bench, the catalyst was studied under simulated flue gas conditions of catalyticoxidation of elemental mercury. The results show that only84%N2,4%O2,12%CO2unfavorable conditions of the flue gas,CW catalyst for the oxidation rate of elemental mercury is still as high as70%, indicating that in the absence of chlorine case,CW catalystfor mercury has a good oxidation resistance. NO oxidation catalyst on CW promote the roleof mercury, SO2significantly inhibit the oxidation of mercury’s role.CW introducing a catalyst based on TiO2as a vehicle for preparing a new type ofCeO2-WO3/TiO2(CWT) catalyst. Experimental studies have shown that simulated smokeCWT catalyst under conditions within the temperature range200-350℃maintained atapproximately100%of the mercury oxidation rate, having a relatively wide temperaturewindow. NO oxidation catalyst on mercury CWT has a significant role in promoting, andSO2have weak inhibition good sulfur resistance. O2and HCl CWT promote oxidationcatalyst on mercury is not obvious, low dependence on HCl. CWT on mercury oxidationcatalyst followed Langmuir-Hinshelwood mechanism.