A Study Of Poisoning Effect Of Heavy Metals On Commercial SCR Catalyst In Coal Fired Power Plant

Selective catalytic reduction(SCR)of nitrogen oxides(NOx)with amlonia(NH3)is a successful method to eliminate NOx from immobile sources,for example,coal-fired power plant and mechanical boilers.Some of the heavy metals in the fly ash deactivate the catalysts because of the solid chemisorption on the dynamic destinations The poisoning chemicals may act by basically hindering the active sites or amend the adsorption patterns of reactants and products by an electronic reactionsIn this study,poisoning effects of heavy metals(Pb,P and Zn)on commercial SCR V2O5-WO3/MoO3 were elucidated and characterized.The fresh catalysts V2O5-WO3/MoO3 were poisoned by heavy metals via two different methods of poisoning(Incipient Wetness Impregnation and Solid Diffusion methods).The activity test results presented that fresh catalysts poisoned by incipient wetness impregnation method exhibited significant inhibiting effects on the denitrification efficiency of the catalyst but catalysts poisoned by solid diffusion method showed negligible loss in denitrification efficiency.Catalysts poisoned by heavy metals via incipient wetness impregnation method presented poisoning influences in this following PbO>P2O5>ZnC1b.Characterizations of fresh and Pb-poisoned catalysts from incipient wetness impregnation method were applied using comprehensive techniques such as X-Ray diffraction(XRD).field emission scanning electron microscopy(FE-SEM),X-ray fluorescence(XRF),NH3-temperature programmed desorption(NH3-TPD),X-Ray photoelectron spectroscopy(XPS),etc.The analytical results indicated that a phase transformation occurred in tungsten and molybdenum species and the amorphous WO3 and M0O3 converted into PbWO4 and PbMoO4 respectively,causing the accumulation and valence imbalance of active vanadium phase,which further decreased the surface acidity and activity of the V2O5-WO3(MoO3)/TiO2 catalyst.