Study On Vortex Coalescence Mechanism And Efficiency Of Ultrafine Particulate PM_0.1

In 2018,the 13th National People's Congress will include the construction of ecological civilization in the Constitution for the first time,which will certainly put forward new requirements for atmospheric environmental governance.The existing dust removal technology in coal-fired power plants can capture 99%of the large particles,but the efficiency of the ultra-fine particles is not satisfactory.In 2016,the Ministry of Environmental Protection first proposed to control the amount of particulate matter,and GB18352.6-2016,the Limit Value and Measurement Method of Pollutant Emission from Light Vehicles?Stage 6?,included particulate matter quantity?PN?in the pollutant control project for the first time,with a limit value of 6.0*10¹¹/km,which means that the control of particulate matter quantity may be implemented in other industrial fields in the future.However,in the flue gas of coal-fired power plants,ultrafine particles account for a very small part of the mass concentration of PM₁₀,while the quantity concentration accounts for 99%.Therefore,it is an urgent task to increase the collection efficiency of ultrafine particles.In this paper,the mechanism of collision and coalescence between particles in turbulent eddy coalescence device and the adsorption of PM₁ on PM_0.1 are analyzed by using the discrete element EDEM coupled fluent software.A small area in the coalescer is selected as the simulation area to simulate the dynamic characteristics of ultrafine particles in the flow field.The simulation results show that the existence of the spoiler will produce a small eddy flow field after the spoiler,which disturbs the steady flow field at the entrance and increases the probability of collision and coalescence between particles.It can be seen from the particle trajectory that there is a neutralization effect after the spoiler,which greatly increases the collision between particles.Furthermore,the simulation analysis shows that the velocity of large particles is lower than that of small particles.The existence of relative velocity will also increase the probability of particle collision and complete the coalescence process.In the process of rotation,due to the interaction between the kinetic energy of particles and the viscoelasticity between particles,the particles after collision are continuously extruded and stretched until the kinetic energy is exhausted to achieve coalescence.The adsorption of large particles to small particles is easy to occur because the high surface energy of small particles is in an unstable state.Using EDEM-API secondary development,the particle contact is compiled,and three functions are realized.One is particle bonding and realizing the interconnection of large particles and small particles to synthesize a larger particle,the other is recording the number of small particles adsorbed on the particle,giving the adsorption efficiency,and the last is to realize the movement of particles in the flow field.The results show that the total number of particles at the entrance of the simulation area is 34 904,and the number of particles at the exit of the L-shaped spoiler is 18 776.Within the simulation time of 0.00324 s,the amount of particles adsorbed near the spoiler accounts for 83.3%of the total amount of particles adsorbed in the whole region.This shows that the coalescence effect between particles is greatly increased due to the existence of spoilers.