| In recent years,with the country's more and more strict emission restrictions towards coal-fired power plants' air pollutants,smoke ultra clean emission technology has become a necessity for coal-fired power plants to survive and develop with sustainability.Electrostatic precipitation(ESP)together with wet ESP(WESP)technology is an important technique to realize smoke ultra clean emissions,but WESP costs high in investment and operation.Thus,by optimizing the wet desulfurization devices(WET-FGD)to efficiently help remove particulate matters(PM)has become an alternative to realize smoke ultra clean emissions.However,this technique needs to meet the premise that the front ESP export smoke whose concentration ? 20mg/m~3.For now,current power plants' ESPs have difficulties in meeting this target.Towards this problem,this paper proposes a solution to achieve the purpose that the front dry electric field can remove large particles efficiently and the end wet electric field remove fine PMs by adopting dry-wet ESP technology.To investigate the effect of water film evaporation on the distribution and removal of fine particles in the wet electric file during ESP,a dry-wet ESP simulation test bench was designed in this paper,and the result in wet and the dry electric fields are compared accordingly.The brief introduction of experiment steps and results are as below:First,the experiment studied the influence of voltage and flue gas temperature on the distribution and removal of fine particles in the dry electric field.The result shows that with the increase of voltage,the efficiency of fine PM removal also increased,and the grade and efficiency of fine PMs differentiated more.Moreover,particles of size around 0.381?m were affected little by voltage increase,and the removal was subtle.Besides,with the increase of smoke temperature,the removal efficiency of fine particles decreased,and the anti-mixing phenomenon appeared,which has little effect on the removal efficiency in the mainstream area,but great influence on those particles near wall.The increase of smoke temperature had the most severe influence on particles size around 0.381?m.Secondly,the experiment also studied the influence of voltage and flue gas temperature on the distribution and removal of fine particles in the wet electric field under the circumstance of natural evaporation of water film.Research indicates that when the voltage is low,the evaporation of the water film will affect the movement of the fine particles in the mainstream area and wall surface at the same time.When the voltage is high,the water film evaporation only affects the movement of the fine particles near the wall.Besides,with the increase of smoke temperature and intensity of natural evaporation,the removal efficiency of fine particles decreased first and then increased,and the anti-mixing phenomenon disappeared;the removal efficiency of particles sized d = 0.38?m-1.6?m was significantly improved.In wet electric field,the flue gas temperature has less capability to affect the resistance,and the increase in water film evaporation intensity will help improve the removal efficiency of fine particle.Finally,by increasing water temperature in the wet electric field to the intensify evaporation,this study also researched the influence rule of the evaporation intensity on the distribution and removal of the fine particles.The result indicates that when the voltage is high,to intensify the evaporation will influence the movement of fine particles both in the mainstream and wall areas.As for the main resistance to particle.movement caused by evaporation intensification,it's mostly in the very stage when smoke enters the wet field;in later stages,evaporation often causes strong flue gas disturbance and the fine particles aggregate,thus the removal efficiency of particles sized d<0.381?m is significantly improved. |
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