Numerical Simulation Research On Turbulent Coalescence Of The Coal-fired Fine Particles

The pollution of fine particles produced by coal-fired boilers has become a prominent atmospheric environmental problem,and the matter has drawn increasing attention from all countries.The combustion process is the main source of fine particles,including fixed coal-based heat source and fuel-based mobile heat source.PM_2.5 and other fine particles are the main factors that cause environmental problems such as reduced visibility of the atmospheric environment and haze and haze.Therefore,it is imperative to control the emission of superfine particles of combustion sources.At present,although the controlled technologies of the fine particulate have a very high standard,but PM2.5 and other ultra-fine particle size is small,the traditional dust removal method is difficult to effectively control these ultra-fine particulate matter emissions.By adding a pretreatment device in front of the traditional dust collector,the fine particles are aggregated into particles of larger particle size,which are then removed by the traditional dust collector to reduce the transmission of fine particulate matter into the atmosphere.In this paper,the turbulent aggregation of fine particles in a coalescence chamber is numerically analyzed by using the CFD software Fluent and the gas-solid two-phase flow.（1）The methods of aggregation of three different fine particles are introduced:Brownian coalescence,electric coalescence,turbulence coalescence,（2）The forces of the fine particles in the chamber are analyzed,including inertia force,gravity,buoyancy,Brownian motion,shearing force,drag force,additional mass force,Basset force,etc.（3）The effects of turbulence and aggregation of fine particles in different aggregated chambers were studied.In this paper,the turbulence clustering kernel function of fine particles is determined,and the turbulence aggregation model of turbulent particles is built.The Eulerian two-fluid model is coupled with the particle swarm equilibrium model.Effect of numerical solution.The effects of different flow devices（cylindrical and triangular shaped scrolls）on the effect of fine particle aggregation were studied.The results show that the two kinds of turbulence devices have good vortex effect,which can promote the turbulence aggregation of fine particles.Based on the characteristics of vortices produced by cylindrical and triangular vortices,a new three-dimensional turbulence gather chamber is constructed by combining the two.The results show that the new turbulence gather chamber is better To enhance the turbulence of the fine particulate matter.The influence of the flow time,the initial particle size of the inlet particles,the volume fraction of the particle phase and the gas flow rate on the coalescence were discussed.