Movement And Agglomeration Characteristics Of Particles With The Effect Of Charged Droplets And Acoustic Waves

Increasingly severe particulate pollution and more stringent emission standards place greater demands on further improving the removal efficiency of particulate matter,especially fine particles.Charged spray,acoustic agglomeration and synergistic method developed on this basis such as "acoustic agglomeration + spray" are important directions for particle agglomeration and removal.This paper focus on the joint effect of charged droplets and acoustic agglomeration.The research was carried out and analyzed in three aspects: microscopic visualization and mechanism of particle movements,morphology of particle capture and deposition,and change of particle size distribution.Firstly,a microscopic visualization platform was built,which use mosquito coil particles and ash from power plant to directly observe the movement of the particles near a charged droplet under different charging and acoustic conditions.Through experimental research and COMSOL simulation,effects of charge mode,charge voltage,sound pressure level and acoustic frequency on movement of particles were studied.Moving characteristics of particles with the joint effect of charged droplet and sound waves were further observed.By charging the droplet,the inertial capture of particles could be changed to electrostatic force(dielectrophoretic force,Coulomb force)-dominated attraction,and the trajectories of the particles in an acoustic field showed reciprocating vibration.With the joint effect,particles were attracted by the droplet while vibrating.Then,the deposition morphology and bonding state of ash particles on the surface of the droplet in different conditions were observed.Experimental results showed that charging of the droplet was the main reason for the deposition change of particles.When the droplet was not charged,the deposition morphology was mainly “dendritic”,in which cases capture of particles mainly depended on the inertial collision and interception of particle trees,and the particle trees tended to rupture under acoustic waves of larger frequencies.When the droplet was charged,particles were attracted on the entire surface of the droplet uniformly and closely.The deposition was more stable and not easily dispersed again due to this closely-attracted state.With the bipolar charge of ash particles and the droplet,and the addition of acoustic waves,the amount of particles captured by the droplet was further increased.Finally,a laser detection system was used to characterize the change of particle size distribution under different electro-acoustic conditions.Influence of different charge and acoustic parameters on the agglomeration effect was obtained and analyzed.It was found that charged droplets and acoustic waves can effectively promote the agglomeration of particles.When the two methods performed together,the agglomeration was significantly enhanced.Under the experimental condition in this paper,the median size of particles could be increased from 6.88?m to 28.23?m.