Multi Physical Field Coupling Simulation And Optimization Of Plate ESP Based On Dust Ultra-low Emission

The frequent occurrence of haze is directly related to the emission of particulate matter in coal-fired industrial boilers.The industrial electrostatic precipitators?ESPs?and bag filters normally are considered as the major air pollution control equipment that can collect the dust particles to be as low as 5 mg/m³ to meet the requirements of ultra-low emission.The computational fluid dynamics?CFD?software was used for the numeri cal simulation of the laboratory scale electrostatic precipitator?ESP?and bag filter,which mainly includes four parts.The corona discharge process was simulated by the plasma model.The simulation results showed the corona area was formed near the discharge wire,which contained a large number of positive ions and free electrons.The interelectrode interference could make the potential field cross linking between the discharges wires,and the field intensity at the midpoint of discharge wires was almost zero.The density of space charge affected the electric field.The flow field in ESPs was simulated to study the influence of the perforated plate and secondary electrohydrodynamic?EHD?flow on the flow field.It was found that the RMS of the perforated plate was 0.16,indicating that the flow distribution in the ESP was significantly improved.The EHD flow was actually the disturbance of space charge to flow field under the action of electric field force.When the airflow velocity was zero,four symmetrical vortexes were formed around the discharge wire.As the airflow velocity increases,the vortexes gradually decreased.When the airflow velocity remained unchanged,with the increase of voltage,the dimensionless E _hd increased,and the turbulence became more intense.Opened discrete phase model?DPM?to simulate particle motion.It was found that the particle phase was affected by turbulent diffusion,which the movement distances increased and the turbulence was severe..The higher of the voltage was,the larger of the particle size was,the lower of the airflow velocity was,the higher of the collection efficiency was,up to 99.5%.A laboratory-scale bag filter was built simulate the flow field distribution and partic le trajectories.It was found that the flow field of bag filter was non-uniform,and the particle phase movement was disordered.By flaring up the inlet pipe,adding a perforated plate and guide plates,the RMS was less than 0.15.The flow field of bag filter was evenly distributed,and the particle distribution was more uniform.A comparison of bag filters and ESPs by KEPs and Wattage numbe rs indicated that the ESPs exhibited significantly higher KEPs?1.91?and lower Wattage numbers?132.7W?.Thus,at the same level of operating mode,using the ESPs was more energy efficient than using bag filters.