Study On Bipolar Charged Mechanism And Enhancement Characteristics Of Bipolar Electrostatic Enhancement Bag Filter

Electrostatic enhancement bag filter,which can be operated with high collection efficiency,low pressure drop and high adaptability,are widely used in the purification of dust pollutants in industrial flue gas.However,the dust discharging methods are unipolar in most of the conventional electrostatic enhancement bag filter.It has been found that the unipolar charged particles on the surface of the bag filter may cause the problem of the dust cleaning difficulty and the bag burning risk due to the charge accumulation on the fabrics.Therefore,a bipolar electrostatic enhancement bag filter is proposed based on the bipolar electrostatic precipitator technology.It is of great significance to study on the bipolar charged mechanism and enhancement characteristics of the bipolar electrostatic enhancement bag filter.It will promote the progress of dust removal technology of the bipolar electrostatic enhancement bag filter.Following researches are given:Firstly,the electrode configuration and the dust removal mechanism of the.wire-tube bipolar electrostatic enhancement bag filter are analyzed.According to Gauss flux theorem and superposition law,the theoretical normal expressions of electric field strength distribution of bipolar wire-tube precharger is derived.Then,the expressions of discharging quantity and efficiency of bipolar electrostatic enhancement bag filter are obtained by the formula of the field strength.The wire-tube bipolar precharger can realize discharging with only one power supply.The wire-tube precharge has simple structure and excellent discharging effect.To verify the enhancement of the bipolar electrostatic enhancement bag filter,the comparative experimental study on collection performances of the bipolar electrostatic enhancement bag filter and the unipolar electrostatic enhancement bag filter is carried out.The silicon powder with 1.74?m medium diameter is used as the test particles.The filtration velocity is 3m/min.The inlet dust concentration is 2500mg/m~3.The results show that,the emission concentration of the bipolar electrostatic enhancement bag filter is 2mg/m~3 when the average electric field strength is 6.0kV/cm.The emission concentration is 50%lower than that of the unipolar electrostatic enhancement bag filter.The dust penetration and pressure drop of bipolar electrostatic enhancement bag filter are25%and 27%respectively lower than that of unipolar electrostatic enhancement bag filter under the same test conditions.Based on SEM analysis,it is shown that the agglomeration of the fine particles is significant when the bipolar discharging method is used in the electrostatic enhancement bag filter.The results of the Particle size analysis show that the median of bipolar charged particle is 1.92 micron,and the cumulative volume fraction of the medium diameter more than 10?m is 10.91%,which is 65.9%higher than that of unipolar charged particle.It means that bipolar discharging method has better agglomeration effect on fine particles and can improve dust removal efficiency.In order to clarify the drag reduction of the bipolar charged particles,the accumulation density of the particles is measured by the natural stacking method.The results show that the accumulation density of the bipolar charged particles is less than that of the unipolar charged particles.It is proved that if the charged particles are bipolar,a fluffy dust layer can be formed on the surface of the bag.Thus,it is helpful to reduce the pressure drop and to improve the filter cleaning effect.