Characteristics Study And Mechanism Analysis On Acoustic Agglomeration Of Fine Particles At Low Concentration

In order to alleviate the increasingly serious pollution of fine particles,the emission standards for fine particles at home and abroad have become stricter.In this regard,the acoustic agglomeration pretreatment technology can be used to agglomerate and grow the fine particles,and then remove them by using a wet electrical dust precipitator,which can not only further improve the dust removal efficiency,but also greatly reduce the amount of fine particles.Finally,achieving the goal of controlling fine particulate emissions.In the theoretical research,the force of the fine particles before and after the collision in the acoustic field was analyzed firstly,and the main force before and after the collision of the fine particles was obtained through theoretical calculation and analysis;then the motion generated by the fine particles after the force is applied.Through the calculation,the carrying properties of the air medium in the acoustic field to the fine particles and the vibration characteristics of the fine particles in the acoustic field were obtained.In addition,various agglomeration mechanisms that promote the agglomeration of fine particles in the acoustic field were studied.By calculating the kernel function of each agglomeration mechanism,the influence of the acoustic frequency,sound pressure level,particle size and temperature to agglomeration kernel function was studied,the results showed that the orthokinetic agglomeration mechanism had the greatest influence on the acoustic agglomeration,which was the main acoustic agglomeration mechanism,and the hydrodynamic mechanism was second.In the experimental research,the acoustic agglomeration experimental platform was designed and built.Firstly,the basic experiment of acoustic agglomeration was carried out.The effects of acoustic frequency,sound pressure level,initial concentration of particles,residence time,temperature and relative humidity on acoustic agglomeration were studied.The experimental results showed that the fine particles had the best optimal acoustic frequency at low concentration,and the optimal acoustic frequency was 900 Hz.Under the circumstances,the acoustic agglomeration efficiency reached 43.07%.The acoustic agglomeration effect was worse after deviating from that frequency;With the increase of sound pressure level,fine particles concentration and temperature,the acoustic agglomeration efficiency increased monotonically;With the extension of the residence time,the acoustic agglomeration efficiency climbed up and then declined,reaching a maximum at 6s.Then the optimization research of acoustic agglomeration was carried out.Firstly,the large kernel particles were added to the particle source.The effects of acoustic frequency,sound pressure level and residence time on the kernel particles-assisted acoustic agglomeration were studied.The experimental results showed that the average increase of acoustic agglomerationefficiency after kernel particles participated in the experiment was about 10%.The addition of kernel particles did not change the optimal frequency of acoustic agglomeration;The acoustic agglomeration effect under low sound pressure level was improved,and the energy consumption of acoustic agglomeration was reduced;In addition,after the addition of kernel particles,the agglomeration efficiency gradually increased with the extension of the residence time,and the optimal residence time did not occur.Afterwards,the spray was introduced into the agglomeration chamber to study the effects of acoustic frequency,sound pressure level,spray flow and chemical agglomerator on the spray-assisted acoustic agglomeration experiment.The experimental results showed that the effect of spray increased the acoustic agglomeration efficiency by more than 20% on average;The optimal frequency of acoustic agglomeration was still 900 Hz,and the acoustic agglomeration effect under low sound pressure level was further improved;With the increased of spray flow,the agglomeration efficiency increased monotonically;In addition,the addition of chemical agglomerator further improved the agglomeration effect of fine particles,and the highest agglomeration efficiency reached 73.26%.Finally,the design of the acoustic wave combined wet fine particle removal system was carried out,and the flow field of the acoustic wave combined wet fine particle removal system that was about to be used for engineering demonstration was optimized by numerical simulation.By means of adding guide plate and airflow distributing plate,the relative root mean square difference of airflow distribution in all electric fields is reduced to below 0.20,and some electric fields are reduced to below 0.15,and the flow deviation of each electric field was controlled within 5%.