Experimental Research On Migration And Transformation Of Mercury In Wet Electrostatic Precipitator System

Coal fired power plant,which is one of the main mercury emission sources,had threaten human health and environment.Wet electrostatic precipitator?WESP?had been applied to plant to control partical emission.But the number of research about mercury removal in WESP is little and the mercury removal mechanism in WESP is still unclear.The research experimental studied mercury migration and transformation mechanism in WESP.A little WESP experiment bench was setted up according to the operating principle of WESP in power plant and the reliability of the bench was verified.Facts which has influence to mercury removal is considered such as electric field,flue gas components and water film.Corona wind in electric field had little contribution to mercury removal.·O and O₃,which generated by O₂ ionizaion,played an important role in merury oxidation and could form HgO with Hg⁰.·O had more effect in mercury oxidation than O₃.SO₂,NO,CO₂ and water vapor inhibited mercury removal by competing with O₂ capturing electron and suppress the formation of·O.Water film improving mercury removal by coerce effect.The flow rate,temperature and pH value of water film had little effect on mercury removal rate.NaClO₂ was chosen as additive in water film to improving elemental mercury removal rate in WESP.The impact of charactristics of water film and component of flue gas on mercury removal was studied.Increasing the concentration of NaClO₂ could improve mercury oxidation by generating more ClO₂^-.The value of pH had obviously effect on mercury remval,higher redox potential of NaClO₂ and concentration of H⁺was beneficial to mercury remoal while in sour environment.Temperature had little effect on mercury removal.Increasing flow rate of water film has a little effect on improving mercury remoal rate.While flue gas contains CO₂?SO₂?NO,NaClO₂ could promote mercury removal in WESP.Increasing concentration of CO₂ had little effect on mercury removal.SO₂ could improve mercury removal in WESP.Increasing SO₂ concentration could improve mercury removal in lower concentration while the effect could be weakened in higher concentration.Improving concentration of NO could improve mercury removal.The process of mercury removal in WESP after added NaClO₂ in water film was analysed.The formula of overall mass transfer coefficients(AK_OG)about Hg⁰ with water film was established by using two-film theory.The calculation of AK_OG according to experimental results is 863 g/h.The analysis of mercury removal progress was made by mass balance and the calculation model,related to overall mass transfer coefficients,flue gas rate and water film rate,of mercury removal rate was established.The model was used to analyse mercury remoal progress and the result shows that the calculation model is meaningful to calculate mercury removal rate in WESP.