Numerical Modelling And Experimental Investigation Of Agglomeration Characteristics Of Fine Particles In A Turbulent Agglomerator

In recent years,fine particles has become the primary air pollutants,which cause serious damage to the human health.Dust emitted from coal-fired boiler is one of the important sources of fine particles in the atmosphere.Duo to submicron particles are difficult to be charged and the electric migration rate is low,the efficiency of traditional dry electrostatic precipitator is not high on the trapping of fine particles.In many new and efficient dust removal techniques,turbulent agglomeration is the use of the nucleation and agglomeration of fine particles in velocity gradient and fluctuation of turbulent jet,and then removing it by conventional electrostatic precipitator.Duo to simple structure,low operation and maintenance cost of turbulent agglomerator,and combined with other dust removal equipment,it has a good application prospect.The authors investigated the effect of the structure of turbulent agglomerator and flue gas parameters on the characteristics of the turbulent agglomeration.The vortex component is one of the most important components of the turbulence agglomerator.Firstly,by using the turbulent two-fluid model coupled with population balance model,the effects of structural parameters such as the type of vortex component and the arrangement on the agglomeration of particles is investigated.The results show that compared with the cylindrical and single vortex,the vortex of spoon type can obviously enhance the intensity of turbulence and increase the collision probability of particles.When the flow area of the turbulent agglomerator accounts for about 1/3 of the area of flue section,the pressure drop of the system is within a reasonable range,and the particles have good agglomeration effect.The spacing of the vortex components is too large or too small to weaken the agglomeration effect of the particles.Secondly,according to the numerical simulation results,the turbulent agglomerator with different vortex component type and arrangement was experimentally tested under actual flue gas parameters in the tail flue.Based on the distribution of particle size and pressure drop of turbulent agglomerator before and after agglomeration,the reason why the structural parameters of the turbulence agglomerator affect the efficiency of the fly ash particles are analyzed.Finally,the agglomeration rate of fine particles was studied with different flue gas parameters,including velocity,temperature,particle concentration and moisture content of the flue gas with a turbulent agglomerator after structural optimization.The results show that turbulent intensity is significantly improved by increasing flue gas velocity,promoting the agglomeration rate of fly ash particles.When the flue gas velocity was 16 m/s,the agglomeration rate of PM2.5 was 44.51%.The flue gas temperature has a limited effect on the agglomeration rate of fine particles above the acid dew point.The higher the concentration of particles,the greater the number of particles per unit volume in flue.This increases the probability of collisions between particles,and improves the agglomeration rate of fly ash.With a particle concentration of 35g/m3,the agglomeration rate of PM2.5 increased to 52.48%.The lower moisture content of flue gas has little effect on the agglomeration process of fly ash particles.