Visualization Research And Numerical Simulation On Movement And Agglomeration Characteristic Of Particles

In recent years,with the rapid economic growth,the problem of particulate pollution in China has become increasingly serious.Fine particulate matter not only reduces the visibility of the atmosphere and causes haze,but also causes direct harm to people's health.The issue of particulate pollution has attracted widespread attention in the society,and the domestic emission standards for particulate matter are becoming more and more strict.However,the traditional dedusting technologies have low removal efficiency of fine particles.It is an effective means to pretreat the particles and make them agglomerate to grow into particles with larger particle size through external effect and then be removed by conventional dust removal equipment.At present,electric coagulation and acoustic wave agglomeration has proved to be effective pretreatment method.The related research mainly focused on the macro particle removal efficiency before and after pretreatment or focused on the theory and model research.Direct observation experiments of particle movements are lacking.Direct observation of particle movements and agglomeration processes can help further understanding the mechanism.In this paper,the motion and agglomeration characteristics of particles under the action of temperature field,electric field,sound field and the combined action of electric field and sound field were observed by means of microscopic visualization technology,and the macroscopic agglomeration and removal effects were studied experimentally.First of all,a microscopic visualization experimental system was constructed to observe the movement of particulate matter under the action of the temperature field,electric field and sound field separately,the trajectories and velocities of particles were obtained by analyzing these photos.The forces acted on particles were analyzed and the particle motion model was established.COMSOL Multiphysics software was used to to simulate the trajectories and the motion speeds of particles under various working conditions.The experiment and simulation results coincide well.When the acoustic wave acts alone,the process of agglomeration between particles and the agglomerated particles separating into smaller particles are directly observed,which proves that the phenomenon of agglomeration and separation among particles exist simultaneously under the action of acoustic wave.Through the microscopic visualization experiment,the microscopic interpretation of the motion characteristics of particles is proposed,which has certain reference value for perfecting and verifying the existing theoretical model,and has certain guiding significance for further optimizing the control and removal technologies of particles.Then,macroscopic experiments were carried out on the charge,agglomeration and removal characteristics of particulate matter under the combined action of electric field and acoustic wave.The experimental results of the combined action of electric field and sound field showed that under the condition that the discharge needle is clean,the acoustic wave will not change the discharge characteristics of the electric field.When the fly ash is deposited on the needle electrode,the addition of sound wave will increase the discharge current.The charge amount of particles increases with the increase of voltage,sound pressure level and sound frequency.The removal efficiency of particles increases with the increase of voltage and sound pressure level,while the influence of sound frequency is more complex.The removal rate is the highest at 1600 Hz.A laser on-line detection system was established to measure the size distribution of particles under the combined action of sound wave and electric field.The experimental results showed that there is agglomeration between particles when the electric field acts alone,but the agglomeration effect is not ideal.The effect of acoustic wave combined with electric field is better than that of single field,but the enhancement is not obvious.The agglomeration process of two particles with opposite charges was directly observed using a high-speed camera.Finally,the forces acted on particles under the combined action of multiple fields were analyzed,and the motion model of particles was established.The agglomeration characteristics of particles under the combined action of temperature field and sound field,temperature field and electric field,and electric field and sound field were simulated.The effects of various parameters on the agglomeration effect were obtained.The theoretical results showed that the combined action of electric field and temperature field plays a synergistic role in promoting interparticle agglomeration.When the electric field and sound field act together,the collision between particles is mainly caused by the action of electric field force.When sound field and temperature field are combined,the synergistic effect of them is the best.