Experiments And Numerical Simulations On The Dust Removing Characteristics And Airflow Distribution Of An Electrostatic-Fabric Precipitator

Thermal power generation can produce a large number of fine particles,which are suspended in the atmosphere and have a serious impact on people’s normal production activities.In order to solve the severe air pollution problem,it is required that generators above 300 MW should achieve ultra-low emissions,and the emission standard is reduced from 50 mg/m~3 to 30 mg/m~3.The constant improvement of the environmental protection standard is put forward higher requirements on dust removal equipment.Electrostatic-fabric precipitator combines the advantages of electrostatic precipitator and fabric precipitator,it can achieve more than 99.9%of the dust removal efficiency,and filter pressure drop is small,efficiency is better.Therefore,researches on electrostatic-fabric precipitator for particles in ultra-low emissions have important guiding significance.In this paper,the dust removal characteristics and airflow distribution of the electrostatic-fabric precipitator are studied with experiment,numerical simulation and field application combined.In experiment,we set up electrostatic-fabric precipitator platform and analyse the particle size distribution of different dust removal areas and the influence of voltage,flue gas velocity and flue gas temperature on the dust removal efficiency is studied.The result shows that 70~80%of the particles can be removed in the electrostatic dust removal area and 20~30%in the fabric dust removal area.The electrostatic dust removal efficiency and the total dust removal efficiency increase with the increase of the voltage,but the fabric dust removal efficiency does not change basically.The velocity of flue gas is negatively correlated with the dust removal efficiency.Decrease on the flue gas temperature is beneficial to the improvement of dust removal efficiency,but the temperature cannot be lower than 100℃.In numerical simulation,CAD software is used for modeling,and FLUENT software is used for numerical simulation.The influence of specific resistance,charge and particle size on dust removal efficiency is studied,and the influence of porosity and aperture on airflow distribution is analyzed.The result shows that the specific resistance of particles is negatively correlated with the total dust removal efficiency and low temperature is beneficial to the improvement of dust removal efficiency.With the increase of particle charge,the total dust removal efficiency first increases sharply and then remains unchanged.The particle size has a significant influence on the dust removal efficiency in the electrostatic region.The larger the particle size is,and the higher the total dust removal efficiency is.The pressure drop can be reduced by increasing the porosity of the airflow distribution orifices.When the porosity of three airflow distribution orifices(plate A,B,C)is 0.45,0.30 and 0.40 respectively,the airflow distribution is optimal.Under the condition that the porosity of plates A,B and C remain unchanged,the airflow distribution is optimal as the aperture of plate C is 16 mm.In application,the influence of operating pressure drop,pulse interval time,vibration time and limiting current ratio on the dust removal efficiency of the electrostatic-fabric precipitator is studied.The result shows that the total dust removal efficiency decreases with the increase of operating pressure drop.With the increase of pulse interval time,the total dust removal efficiency does not change obviously.The total dust removal efficiency decreases with the increase of vibration interval time.The influence of the limiting current ratio on the total dust removal efficiency is very small,but it cannot be lower than 0.5.