Coagulation Of Bipolar Charged Particles In Electric Field

Electrical agglomeration is supposed to be an efficient method to improve the collection efficiency of the electrostatic precipitator (ESP) for collecting the submicron particles. Experiments were carried out to investigate agglomeration charactertistics of bipolar charged particles in alternative current (AC) and pulsed electric field. The results are summarized as follows:1) A new-type electrostatic agglomerator with two zones was developed. The distinguishing feature of this elcectrostatic agglomerator is that the parcicles are bipolarly charged and coagulated in the same AC electric field simultaneously. And there are two advantages: the particles can be charged and agglomerated repeatedly. When the particles are agglomerated into a larger particle, the surface area becomes greater. The charge on the agglomerated particles is increased when this particle is charged again. Thus, the agglomeration rate gose up; because the particles can be bipolarly charged in the AC electric field, it is not necessary to have a precharging zone. Therefore, the total length of the electric field becomes shorter in the application.2) According to changing discharge type of DBD reactor, a new bipolarly charged method of particles in pulsed electric field was proposed. The comparison experimental results have shown that the collection efficiency of bipolar charged particles in pulsed electric field is higher than that in AC electric field. Furthermore, a PTP reactor was designed to investigate the influence of reactor structure on collection efficiency of electrostatic agglomerator.3) The theory of particle charging in pulsed electric field was established. The particle charging process is divided into two periods, the electron charging in pulse discharge duration and the ion charging after the pulse discharge duration.4) Formula to calculate the coagulation coefficient of bipolar particles in AC electiec field was proposed by adapting the method that was developed by Williams to evaluate the acoustic coagulation coefficient. According to the concept of the self-preserving in particle size distribution, the collection efficiency of electrostatic agglomerator was determined theoretically.