Study On The Particle Removal Efficiency In Wet Membrane Electrostatic Precipitator

The ionic wind in the electrostatic precipitator will cause different scale disturbances to the flow field,which has a significant impact on the movement and capture of particulate matter.The wet membrane electrostatic precipitator evenly distributes a water film on the wall surface of the dust collecting plate to achieve the purpose of dust removal,and avoid secondary dust.A numerical model of multi-physics coupled with electrostatic field,flow field,particle charge and motion is established by using finite element software of COMSOL Multiphysics.It can be realized to do research on the electro-hydrodynamic flow in wet and dry electrostatic precipitators.The Ⅴ-Ⅰ characteristics and dust removal efficiency of the wet membrane electrostatic precipitator are tested experimentally under different working conditions,providing a theoretical basis for further improvement performance of the electrostatic precipitator.The contents are as follows:Firstly,the effects of three types of dust collector plates on the internal ionic wind disturbance mechanism and the charge,capture and motion trajectories of particulate matter are analyzed.It is found that the electric field and flow field of different plate shapes are significantly different.The particle charge is related to the applied voltage,inlet wind speed and particle release position.Under the same conditions,the M-type plate has a better regulation effect on the ionic wind.The charge of particulate matters is also high.The particle migration speed is studied and found that under the action of ionic wind,particles producing velocity components opposite to the direction of movement to the dust collector,which affects the particle capture efficiency.By comparing the effect of three plate types on the removal of fine particles,the following sequence is obtained that M-type plate is larger than P-type plate,P-type plate is larger than W-type plate.Secondly,the flow field distribution of the ionic wind generated by the saw-tooth electrode in the wet membrane electrostatic precipitator is studied.At a voltage of-30 k V and the inlet wind speed of 0.3 m/s,a pair of reverse symmetrical vortices is generated at the tip of the sawtooth front,squeezing the main airflow toward the dust collecting plate.The vortex at the tip of the flow channel points to the entrance is larger than the vortex whose tip points to the exit.The relationship between ionic wind and voltage and inlet wind speed is analyzed by quoting the ratio of electro-hydrodynamic force and fluid viscosity force(EHD/Re~2).It is obtained that the higher the voltage,the stronger the ionic vortex strength;The larger the inlet wind speed,the weaker the ionic wind convection field disturbance.The motion of the water membrane drives the airflow to generate a vortex at the bottom.This vortex generates a velocity component that is perpendicular to the main airflow.This component is opposite to the gravity direction of the particles,and promotes the deposition of particles along the main airflow toward the outlet.The interaction of water film motion and ionic wind makes the distribution of the flow field more complicated.With the increase of the inlet wind speed,the water film motion has weaker effect on the flow field than the ionic wind,but the effect on the main airflow motion is more sustained.Thirdly,an experimental platform for wet membrane electrostatic precipitator is designed and set up.It is found that the secondary current increases with the increase of the number of discharge electrodes by experiments.At the same voltage,increasing the water supply flow and reducing the wind speed can increase the secondary current value and the dust removal efficiency,while excessively high dust concentration will reduce the current value.At a voltage of 40 k V,the dust removal efficiency of the electrode line spacing of 150 mm is 16.482%higher than that of 75 mm.At the same voltage,the secondary current and dust removal efficiency of the tip of the sawtooth electrode perpendicular to the dust collecting plate are higher than those parallel to the dust collecting plate.By studying the influence of the auxiliary ground electrode between the discharge electrode and the dust collecting plate and the discharge electrode and the discharge electrode on the dust removal efficiency,it is found that arrangement of a ground electrode line between the discharge electrode and the discharge electrode has a certain improvement for the dust removal efficiency.Finally,based on Particle Image Velocimctry(PIV)technology,an experimental system for capturing the internal flow field in electrostatic precipitator is designed and set up.The working principle of the PIV instrument and the process of the shooting experiment of the flow field in the electrostatic precipitator are introduced in detail,and the technical difficulties in the shooting test process are explained.The flow field of the dry electrostatic precipitator is tested,it is obtained that the vector distribution of the velocity of the flow field.