Ultrafine Particle Orthokinetic Aggregation Model And Investigation Of Aggregation Process In Sound Field

Particulate pollutants,also known as aerosol pollutants,are very serious pollutants in China,especially ultrafine particles.Particle pollutants are mainly from fossil fuel burning,vehicle exhaust and the human natural activity.In particular,respirable particle,especially the ultrafine particles are harmful to human health and environment.Because the ultrafine particle has small aerodynamic diameter,strong activity,big surface,and strong adsorption of some toxic substances,such as heavy metals,organic pollutants and microorganisms,these characteristics made them cause great harm to human health;Ultra-fine particles also caused smog,which is now a serious problem for most of the Chinese cities.Due to the inefficiency of the dust removal equipment of coal-fired power stations to remove PM_2.5,it is necessary to study the pretreatment of ultrafine particles.The sound field agglomerate is a potential pretreatment technology at present.The traditional particle remover can only capture some large particles,but the gathering effect of the acoustic field agglomeration technology is very efficient for ultrafine particles.In the coalescence device,different sizes of particles vibrate under the different amplitudes,and various sizes of particles have different velocity.The large particles act as a nuclear,and the relative motion between the particles made them collide and agglomerate together to form larger particles.Further,the large particles and other small particles continue to collide.After a period of time,the size of particles grows bigger and this procedure can achieve the purpose of removing ultrafine particles.This paper studied the ultrafine particle aggregation in sound field aggregation device and corrected the orthokinetic aggregation kernel using the collision efficiency?.This paper considered the influences of addition of vectors browian aggregation and orthokinetic aggregation and obtained a new sound field aggregation model.It further compared it with a scalar addition sound field aggregation model.This paper solved the population balance equation by employing grouping method and numerical simulation of particle aggregation process using Eulerian-Eulerian two-fluid coupling population balance model.This paper used user-defined sound field aggregation kernel of UDF function of Fluent to measure the effect of different residence time,sound pressure level and frequency on the aggregation of the ultrafine particle in sound field.The results showed that compared with the scalar addition aggregation model,the vector addition aggregation model with the particle diameter range from 0.2 to 0.8?m is more approximate to the experimental value.And it found that the vector addition sound filed aggregation model is more consistent with the experimental results.The results showed that he optimum frequency is 1400Hz and the sound pressure level is147dB.In addition,setting residence time to 4-6s is suitable to the ultrafine particle aggregation.This paper is on the flue of the front section of the cloth bag collector at the tail flue of the coal-fired power stations and adding half cylindrical“S”type vortex,I used the mathematical model that developed in this paper and simulated the acoustic agglomeration effect.The results show that the agglomeration effect of in sound field aggregation device is good;In addition,I also find that the decrease of inlet velocity and the increase of particle volume fraction can improve agglomeration effect.