Analysis On Movement Characteristics Of Particle Group In Asymmetric Impinging Stream

With increasingly stringent environmental policies,our country's requirements for energy saving and emission reduction are getting higher and higher.It is imperative to reduce the emission of pollutants generated by coal-fired power generation.Nowadays,ultrafine particle such as PM2.5 and PM10 contained in exhaust gas is harmful to the human body,but existing dust removal technology is generally not efficient in removing ultrafine particles.Therefore,the research of high-efficiency ultrafine particle agglomeration technology is extremely critical for dust removal.Among numerous coalescence methods,the turbulent coalescence of ultrafine particles by impinging stream is not only relatively simple to operate,but also economical and feasible,moreover,it is easy to apply on a large scale.Thus,studying the movement of particle groups in the impinging stream is of great significance for developing the turbulent coalescence technology,increasing the efficiency of particle agglomeration,and improving the theory of impinging stream.Based on the traditional symmetric impinging stream,this research takes air and pulverized coal particles as working fluids to establish the two and three dimensional models of motion of particles and flow fields in impinging stream reactor by changing the velocity of the inlet fluid.On the basis of computational fluid dynamics and discrete element coupling method(CFD-DEM),combined with Euler-Lagrange model,the 2D model is solved by the coupling of FLUENT and UDF.And the 3D model is solved by the coupling of FLUENT and EDEM in order to simulate the movement of the flow field and the particle group in the gas-solid two-phase impinging stream,and then explore the changes of residence time of the particle group at different inlet velocity ratio.The simulation results show that CFD-DEM model can be simulated by numerical methods,which is suitable for the characteristics of particles and flow fields both for two or three dimensional models.CFD-DEM model can accurately describe the interaction between the particles and the flow field and ensure that the particles can be coupled with the flow field better.The results of the study show that the average residence time of the particle group in the impact-active area increases with the ratio of the inlet velocity at both sides.Compared to symmetric impinging streams,the range of motion of particles in asymmetric impinging streams is larger,the number of collisions between particles increases,and collisions are more severe.The flow field can be set asymmetric by changing the inlet flow velocity in practical applications,effectively increasing the residence time of the particles in the impact-active area,improving the probability of collisions between particles,and thus increasing the efficiency of coalescence.