Numerical Simulation Of Flue Gas Mercury Removal By Sorbent Injection Based On Electrostatic Precipitator

Power sorbent injection（PSI）is currently the most mature and effective technology for eliminating mercury in coal-fired power plants,which can convert gas-phase mercury in flue gas into particulate mercury,and finally captured in electrostatic precipitators.However,due to the high-voltage environment inside the ESP,it is impossible to explore the removal mechanism of flue gas mercury in PSI by measuring the particle and mercury concentration in internal space Therefore,this paper will use numerical simulation to deeply study the mercury removal process in ESP system,and reveal the adsorption mechanism.This paper establishs the synergistic mercury removal model of in-flight adsorption and wall-bounded adsorption in the process of sorbent injection mercury removal,by further considering the convective mass transfer effect of wall-bounded adsorption on flue gas mercury.The simulation results that the increase in particle size of the spray sorbent from20μm to 80μm will reduce the adsorption surface area,gas-particle mass transfer rate and residence time during the adsorption,resulting in a decrease in in-flight mercury adsorption efficiency(E_In-flight)from 48.1%to3.3%.Meantime,due to the reduction of the reaction area of the ESP dust collection plate,the wall-bounded mercury adsorption efficiency(E_Wall-bounded)decreased from 5.0%to 2.2%.Increasing the spray concentration and the adsorption constant K mean that there are more active adsorption sites per unit volume,thereby reducing mass transfer resistance.The EHD effect plays a dual role by accelerating the deposition of adsorbents and reducing the residence time of sorbents in mercury removal in ESP.The effect of electrode adsorption on flue gas mercury removal after five minutes of sorbent spray was studied.As the ejection concentration increases from 2 g/m³ to 8 g/m³,the mercury removal efficiency increases from 3.5%to 7.4%in the initial stage,and shows a more excellent mercury removal effect in the subsequent adsorption process.Increasing the adsorption constant K means providing more active adsorption sites,which ensures efficient mass transfer propulsion and a more sustained adsorption effect during the adsorption process.The presence and enhancement of the EHD effect can enhance the convective mass transfer rate near the discharge electrode and promote the electrode adsorption.